the ms 7 3 1992 suusamyr kyrgyzstan earthquake in the tien shan 2 aftershock focal mechanisms and surface deformation abstract the m s 7 3 suusamyr earthquake of 19 august 1992 was a large thrust type earthquake in the northern tien shan of kyrgyzstan an intracontinental mountain belt in central asia focal mechanisms of both the mainshock and 13 moderate sized aftershocks are consistent with a seismotectonic setting that is dominated by nnw sse horizontal compression which manifests itself in reverse faulting along roughly east west trending steeply dipping fault planes the earthquake produced surface faulting at two widely separated locations along two different fault segments the total length of which was less than 4 km detailed measurements at one of the locations indicate a net slip of at least 4 2 0 4 m a wide variety of secondary surface effects was observed in the macroseismic zone that extended over an area of 2500 km 2 the lack of extensive surface rupture from such a large event can be explained by a combination of 1 redistribution of the net slip at depth among the secondary splays that branches out from the main fault near the surface and 2 variable surface slip over the fault length the active deformation associated with this event documents a structural style that involves steeply dipping reverse faults extending from mid crustal depths to the surface at nearly uniform dip accommodating crustal shortening in the interior of the tien shan

global sea level rise published values for the long term global mean sea level rise determined from tide gauge records exhibit considerable scatter from about 1 mm to 3 mm yr this disparity is not attributable to instrument error long term trends computed at adjacent sites often agree to within a few tenths of a millimeter per year instead the differing estimates of global sea level rise appear to be in large part due to authors using data from gauges located at convergent tectonic plate boundaries where changes of land elevation give fictitious sea level trends in addition virtually all gauges undergo subsidence or uplift due to postglacial rebound pgr from the last deglaciation at a rate comparable to or greater than the secular rise of sea level modeling pgr by the ice 3g model of tushingham and peltier 1991 and avoiding tide gauge records in areas of converging tectonic plates produces a highly consistent set of long sea level records the value for mean sea level rise obtained from a global set of 21 such stations in nine oceanic regions with an average record length of 76 years during the period 1880 1980 is 1 8 mm yr 0 1 this result provides confidence that carefully selected long tide gauge records measure the same underlying trend of sea level and that many old tide gauge records are of very high quality

seismic source modeling seismic source modeling is taken to mean the modeling of seismograms to investigate kinematic properties of the earthquake source current trends such as the use of other data types e g geodetic measurements of coseismic deformation and the explicit consideration of source dynamics when modeling seismograms are beginning to blur this definition but i will adhere to it in this review i have divided seismic source modeling into teleseismic regional and near source modeling teleseismic modeling has the advantage of global coverage for earthquakes of magnitude 5 5 and larger but does not provide much more than point source parameters regional distance modeling has the advantage of a more rapid assessment of earthquake source properties but is complicated by relatively complex wave propagation the coverage is also limited to areas of broadband regional networks typically continental areas of developed countries near source modeling has the potential for detailed imaging of source properties but very few earthquakes occur in regions with sufficient instrumentation to allow this i have also included a section on historical earthquakes because of the additional issues that seismologists face in working with pre wwssn data and because of the important issues such as earthquake recurrence that require historical data in addition to reviewing the progress in seismic source modeling during the last four years i have also briefly reviewed some of the progress in understanding earthquake physics and hazards that has come about because of basic research in earthquake source modeling

ultralong period seismic study of the december 2004 indian ocean earthquake and implications for regional tectonics and the subduction process analysis of the earth s longest period normal modes shows that the december 2004 sumatra andaman earthquake was much larger mw 9 3 than ini tially inferred from surface wave data and involved slip on a much longer fault than initially inferred from body wave data the seismic moment and relative excitation of the normal modes indicate that the entire aftershock zone ruptured consistent with the large tsunami amplitudes in thailand sri lanka and india an apparent increase in seismic moment with period results from interference between parts of the fault the earthquake resulted from subduction of the indian plate beneath the burma microplate a sliver plate between the indian and sunda plates hence the rate and direction of convergence depends on the motion of the burma plate which is not well known convergence would be highly oblique if the rate of motion between burma and sunda is that inferred from spreading in the andaman sea and less if a slower rate is inferred from the sagaing fault the december earthquake was much larger than expected from a previously proposed relation based on the idea of seismic coupling in which such earthquakes occur only when young lithosphere subducts rapidly moreover a global reanalysis finds little support for this correlation hence we suspect that much of the apparent differences between subduction zones such as some trench segments but not others being prone to m w 8 5 events and hence oceanwide tsunamis may reflect the short earthquake history sampled this possi bility is supported by the variability in rupture mode at individual trench segments

centroid moment tensor solutions for january march 1992 abstract centroid moment tensor solutions are presented for 160 earthquakes that occurred during the first quarter of 1992 the solutions are obtained using corrections for aspherical earth structure represented by a whole mantle shear velocity model sh8 u4l8 of dziewonski and woodward

the dynamics of a seismic wave field animation and analysis of kinematic gps data recorded during the 2011 tohoku oki earthquake japan 1 during rupture earthquakes induce permanent and dynamic ground displacements that can be measured by gps more than 1200 continuous gps stations distributed throughout japan recorded the displacements due to the march 11 2011 mw9 0 tohoku oki earthquake we animate these data which shows the growth of the earthquake rupture over time and illustrates differences of earthquake magnitude through two smaller aftershocks we also identify dynamic ground motion due to s waves body waves love waves and rayleigh waves surface waves in this data set real time availability of such displacements could be of great use in earthquake response and tsunami warning and to some degree in earthquake early warning we find that the length of the ruptured fault can be approximated from displacements which could allow rapid identification of areas prone to large aftershocks we outline a method that integrates real time displacements into an earthquake alarm system the animated displacements in map view are easily understandable by specialists and non specialists alike and hence provide a valuable education and outreach tool

pre and post seismic slow slip on the plate boundary off sanriku ne japan associated with three interplate earthquakes as estimated from small repeating earthquake data abstract the spatio temporal variation of quasi static slow slip on the plate boundary before and after three major earthquakes mj 7 1 in 1989 mj 6 9 in 1992 and mj 7 6 in 1994 off sanriku northeastern japan is estimated using small repeating earthquake data the small repeating earthquake sequence employed is considered to correspond to repeated rupture of a small isolated asperity surrounded by a quasi static slipping area and the activity of the source reflects the quasi static slip rate small repeating earthquakes accompanying moderate sized events appear to have been activated prior to the major events under investigation with activity starting 6 days 2 days and 8 months before the occurrence of the 1989 1992 and 1994 events these results indicate that the quasi static slip near the hypocenters of these major earthquakes was accelerated prior to the main shocks causing stress concentration at the asperities responsible for the main shocks this idea is supported by the fact that both the epicenters locations of initial breaks and areas where quasi static slip was accelerated were located on the same side of the main shock asperities migration of quasi static slip acceleration in the off sanriku region was also identified apparent in the aftershock activity of the 1994 event and the earthquake swarms including the 1989 mj 7 1 and 1992 mj 6 9 events the present results reveal that quasi static slip may have played a crucial role in the occurrence of these large earthquakes as well as contributing to aftershock and swarm activity on the plate boundary

location of the africa australia india triple junction and motion between the australian and indian plates results from an aeromagnetic investigation of the central indian and carlsberg ridges accepted 1994 june 7 received 1994 may 23 in original form 1993 may 24 summary prior studies have proposed and examined the hypothesis that india and australia are separate rigid plates separated by a wide near equatorial e w striking plate boundary attempts to place narrow limits on the location of the africa australiaindia triple junction have been hindered however by the lack of useful magnetic profiles crossing the eastern carlsberg ridge and northern central indian ridge herein we present near ridge portions of new profiles from an aeromagnetic survey of the carlsberg ridge east of 66 e and of the central indian ridge north of 19 s these new data are used to estimate 35 new spreading rates averaged from the middle of chron 2a 3 03 ma to the present all other plate motion data along the central indian and carlsberg ridges are also analysed to investigate the present kinematics of the indian ocean especially the motion and boundary between the indian and australian plates unlike prior efforts we objectively estimate uncertainties in the strikes of transform faults along the carlsberg and central indian ridges

centroid moment tensor solutions for october december 1992 abstract centroid moment tensor solutions are presented for 205 earthquakes that occurred during the fourth quarter of 1992 the solutions are obtained using corrections for aspherical earth structure represented by a whole mantle shear velocity model sh8 u4l8 of dziewonski and woodward

centroid moment tensor solutions for july september 1992 abstract centroid moment tensor solutions are presented for 224 earthquakes that occurred during the third quarter of 1992 the solutions are obtained using corrections for aspherical earth structure represented by a whole mantle shear velocity model sh8 u4l8 of dziewonski and woodward

vertical gps ground motion rates in the euro mediterranean region new evidence of velocity gradients at different spatial scales along the nubia eurasia plate boundary we use 2 5 to 14 years long position time series from 800 continuous global positioning system gps stations to study vertical deformation rates in the euro mediterranean region we estimate and remove common mode errors in position time series using a principal component analysis obtaining a significant gain in the signal to noise ratio of the displacements data following the results of a maximum likelihood estimation analysis which gives a mean spectral index 0 7 we adopt a power law white noise stochastic model in estimating the final vertical rates and find 95 of the velocities within 2 mm yr with uncertainties from filtered time series 40 smaller than from the unfiltered ones we highlight the presence of statistically significant velocity gradients where the stations density is higher we find undulations of the vertical velocity field at different spatial scales both in tectonically active regions like eastern alps apennines and eastern mediterranean and in regions characterized by a low or negligible tectonic activity like central iberia and western alps a correlation between smooth vertical velocities and topographic features is apparent in many sectors of the study area glacial isostatic adjustment and weathering processes do not completely explain the measured rates and a combination of active tectonics and deep seated geodynamic processes must be invoked excluding areas where localized processes are likely or where subduction processes may be active mantle dynamics is the most likely process but regional mantle modeling is required for a better understanding

detecting slow long duration slip of large earthquakes using very long period orbital surface waves summary in this paper we present a simple yet effective technique for measuring the source time delay spectrum from very long period world circling surface waves without relying on assumed earth models or calculation of synthetic seismograms by using autocorrelation and self convolution functions derived from whole seismograms of large earthquakes recorded at a seismic station it is possible to isolate the source effects and precisely 5 5 s determine the source delay spectrum at periods as long as 600 s measurements at such long periods are necessary for detecting slow precursory slip and slow creep after the main fast seismic phase of large earthquakes we apply this technique to five recent large earthquakes the 1989 macquarie ridge m 8 2 the 1992 nicaragua m 7 6 the 1993 mariana islands m 7 8 and the 1994 deep events in fiji m 7 6 and bolivia m 8 3 our results are largely in agreement with the results obtained by other investigators the mariana islands fiji and bolivia earthquakes had a normal rupture duration the nicaragua earthquake exhibits a source time delay spectrum with the delay increasing from 31 s at the 100 s period to 50 s at the 600 s period indicating an unusually slow rupture process the macquarie ridge earthquake is anomalous by the discrepancy between the love wave and rayleighwave estimates love waves in the period band of 150 to 600 s show a normal flat source delay spectrum with a delay of about 28 s the rayleigh wave spectrum agrees with the love wave spectrum for periods smaller than 200 s and greater than 400 s however it shows a significantly shorter source delay about 15 s in the 250 to 350 s period range the unusual nature of the macquarie ridge earthquake s surface wave spectrum was pointed out by ihmli harabaglia jordan 1993 who also provided an explanation in terms of a slow precursory moment release this explanation is not consistent with the flat love wave spectrum determined here

seismic moments of major earthquakes and the rate of shortening across the tien shan three twentieth century earthquakes that richter assigned m 8 and two of comparable magnitude in the nineteenth century imply rapid deformation within the tien shan seismic moment tensors of major earthquakes in this century suggest an average shortening rate of 7 2 mm yr 1 across the tien shan in the western part however where three of the five largest earthquakes occurred the calculated rate is consistent with the value of 20 mm yr 1 measured using gps in that area by abdrakhmatov et al as avouac et al suggested the high rate in the western part apparently is a manifestation of counter clockwise rotation of the tarim basin relative to eurasia about an axis near the east end of the tien shan

centroid moment tensor solutions for october december 1996 abstract centroid moment tensor solutions are presented for 237 earthquakes that occurred during the fourth quarter of 1996 the solutions are obtained using corrections for aspherical earth structure represented by a whole mantle shear velocity model sh8 u4l8 of dziewonski and woodward dziewonski a m woodward r l 1992 in emert h harjes h p eds acoustical imaging plenum 19 pp 785 797 a new model of anelastic attenuation of durek and ekstrom durek j j ekstrom g 1996 bull seism soc am 86 144 158 is used to predict the decay of the waveforms

the ms 7 3 1992 suusamyr kyrgyzstan earthquake 1 constraints on fault geometry and source parameters based on aftershocks and body wave modeling we investigated the suusamyr kyrgyzstan earthquake of 19 august 1992 using aftershock data teleseismic body wave modeling and field observations aftershocks were recorded by the iris kyrgyzstan broadband network a temporary six station aftershock network and a regional network operated by the kyrgyz institute of seismology the aftershocks which range in depth from the surface to 18 km defined a 50 10 km long rupture zone that dips 50 13 to the south and strikes roughly east west the base of the eastern end of the aftershock zone shallowed to the east along strike and may represent a lateral ramp the surface ruptures also had an east west strike and dipped south but the total length less than 4 km was much shorter than the aftershock zone a teleseismic body wave inversion using a point source and a directivity correction yields a focal mechanism with a strike of 221 dip of 46 and a slip of 43 we obtained a moment of 4 1 1019 n m with a centroid depth between 5 and 21 km the rupture propagated along an azimuth of 330 60 which matches the relative location of the mainshock with respect to the aftershock zone the results of the aftershock study and teleseismic inversion yield a clear picture of the fault geometry of a large thrust earthquake

mapping the upper mantle three dimensional modeling of earth structure by inversion of seismic waveforms a method is presented for the inversion of waveform data for the three dimensional distribution of seismic wave velocities the method is applied to data from the global digital networks international deployment of accelerometers global digital seismograph network the selected data set consists of some 2000 seismograms corresponding to 53 events and 870 paths the moment tensors of the earthquakes are determined through an iterative procedure which minimizes the corrupting influence of lateral heterogeneity a global model is constructed for shear wave velocity expanded up to degree and order 8 in spherical harmonics and described by a cubic polynomial in depth for the upper 670 km of the earth s mantle although no a priori information is incorporated the model predictions reproduce much of what is known about the dispersion of mantle waves for example high phase velocities for shields low velocities at ridges and a strong degree 2 pattern for rayleigh waves since the method makes use of complete waveforms overtone data are also included it is shown that the model is reproducible in that substantially the same model can be constructed from each half of the total data set considered independently the model shows that shields and ridges are major features in the depth interval 25 250 km the ridges of the southern pacific and the larger shields persist to 350 km but the southeast indian rise is underlain by a high velocity anomaly at this depth as is much of the mid atlantic ridge at 450 650 km the major features are a broad region of high velocities incorporating south america much of the south atlantic and parts of west africa a broad region of low velocities in the central and eastern pacific high velocities in the western pacific and a low velocity anomaly beneath the red sea and the gulf of aden in the absence of a crustal correction degrees 2 and 3 show a high positive correlation with the geoid paradoxically this is largely destroyed when the distribution in crustal thickness is taken into account spherical harmonic degrees 4 7 show a significant negative correlation

centroid moment tensor solutions for october december 1991 centroid moment tensor solutions are presented for 160 earthquakes that occurred during the fourth quarter of 1991 the solutions are obtained using corrections for aspherical earth structure represented by a whole mantle shear velocity model sh8 u4l8

imaging a slow bilateral rupture with broadband seismic waves the september 2 1992 nicaraguan tsunami earthquake the spatio temporal rupture history of the september 2 1992 nicaragua tsunami earthquake ms 7 2 mw 7 6 is analyzed using long period 157 288 s rayleigh and love wave spectral inversions and an empirical green function analysis of very broadband 10 250 s body and surface waves the event has a rupture duration exceeding 110 s with a slow 0 6 2 3 km s rupture velocity and involves shallow dipping 6 10 thrust faulting at a shallow depth 10 km with the latter being primarily responsible for the strong tsunami excitation two subevents dominate the source radiation resulting from a slow asymmetric bilateral 100 160 km long rupture long period surface wave directivity reveals a predominant rupture azimuth of 140 30 consistent with asymmetric extension of the bilateral rupture at an azimuth of 125 30 resolved by the source time function analysis an inverse radon transform of the source time functions confirms the asymmetric bilateral rupture characteristics

recurrence intervals of characteristic m4 8 0 1 earthquakes off kamaishi ne japan comparison with creep rate estimated from small repeating earthquake data abstract we examined the cause of the fluctuation in recurrence intervals of an m4 8 0 1 characteristic earthquake sequence off kamaishi ne japan by comparing the recurrence intervals with creep quasi static slip rates around the asperity estimated from small repeating earthquake data the eight recurrence intervals 5 52 yrs on average of the sequence are almost constant but have small fluctuations standard deviation of 0 68 yrs characterized by a longer recurrence interval following a shorter one from the analysis of small repeating earthquakes from 1990 to 2003 we found a significant acceleration of creep on the plate boundary during and after an earthquake swarm in 1992 to the east of the m4 8 0 1 event the acceleration seems to have migrated from east shallower part of the plate boundary to west deeper part over about 80 km in 2 yrs to reach the asperity of the m4 8 0 1 events the 1995 event that occurred with the shortest recurrence interval was probably advanced by this acceleration of creep in around 1994 we also found similar earthquake swarms prior to the 1962 and 1973 characteristic events that occurred after the second and third shortest recurrence intervals respectively therefore it is possible that the 1962 and 1973 events were also advanced by creep accelerations the three pairs of longer and shorter recurrence intervals we observed suggest the existence of creep deceleration following the acceleration we conclude that the recurrence interval fluctuations of the m4 8 0 1 events are mainly controlled by temporal changes of creep around its asperity

velocity gradients in the northern indian ocean inferred from earthquake moment tensors and relative plate velocities the region in the northern indian ocean between the central indian ridge the sumatra trench and 15 s to 9 n exhibits high seismicity along with basement and sediment deformation this area represents a diffuse plate boundary between the distinct and separate portions of the indian and australian plates we invert the spatial distribution of horizontal strain rates in this diffuse plate boundary zone to obtain the horizontal velocity field associated with the moment release from 61 earthquakes that have occurred over the past 80 years in the inversion the three dimensional rotation vector function w is determined at all corner points i e knot points of a grid such that the predicted strain rate values match the observed strain rates within the grid areas in a least squares sense the rotation vector of australia relative to india defined by the earthquake data alone is 10 1 s 9 1 81 5 e 5 4 0 1 0 06 m y 1 sigma error which is slightly different in location from the expected vector estimated using seafloor magnetic anomalies and transform fault trends 3 2 s 75 1 e 0 288 m y demets et al 1994a b by minimizing the rate of work within a continuous viscous medium that accommodates australia s motion relative to india demets et al 1994a we determine the complete horizontal velocity gradient tensor within the zone of diffuse deformation the viscosity tensor within all of the deforming areas can be specified when all the regions are free to strain in any direction and have the same viscosity uniform isotropic viscosity the predicted strain pattern is either pure extension or pure compression which is in contrast to the style of earthquake deformation east of chagos where both thrust and strike slip mechanisms are observed however when the isotropic viscosity of regions within the wharton basin is increased relative to the isotropic viscosity levels of areas along the ninetyeast ridge the plate motion is accommodated by combined thrust and strike slip styles of strain along the ninetyeast ridge and within the eastern central indian basin this predicted strain that accommodates plate motion is in agreement both in direction and style with the earthquake related strains in these regions although most of the observed style and direction of strain can be explained by lithospheric strength differences between the wharton basin and ninetyeast ridge areas alone the presence of strike slip faulting within the wharton basin requires a preexisting fabric that favors strike slip faulting there as a strain mechanism that accommodates in part the motion of australia relative to india to first order the direction of principal strain rates the style of strain and the spatial distribution of strain rates from the earthquakes are in accord with the accommodation of the expected plate motion whereas across the plate boundary zone the rates from 80 years of seismicity average out to at most 60 of the total strain rate

interplate seismic activity near the northern japan trench deduced from ocean bottom and land based seismic observations the off sanriku area the landward slope area of the northern japan trench is characterized by its active seismicity which is directly related to the subduction process of the pacific plate in july august 1992 a seismic swarm activity was observed near the trench five earthquakes of m 6 occurred successively within 2 weeks at the beginning of the activity we deployed an ocean bottom seismograph obs array in the epicentral region to make an in situ observation of the spatial distribution of these events and to study the characteristics of the swarm activity in detail we relocated 357 events from 23 july to 26 august with focal depth errors less than 5 km by using both the obs and the land network data the swarm events are not distributed homogeneously over the plate boundary but form several clusters a remarkable concentration of the earthquakes was found in the vicinity of the hypocenter of the largest event during the obs observation m 6 2 29 july this formed the most active cluster almost all the earthquakes including the m 6 2 event occurred at depths of about 15 km and were concentrated along a thin plane dipping to the west at 5 the location of the plane coincides well with that of the plate boundary derived from previous seismic explorations we also relocated epicenters of the off sanriku events by introducing station corrections to the land network data during the period when the obs array was absent the corrections were estimated from the travel time residuals of the hypocenter relocation using the obs and the land network data the result of the epicenter relocation strongly indicates the existence of a zone of extremely low seismic activity beneath the inner trench wall where low seismic velocity mechanically weak unconsolidated sediments overly the subducting pacific plate

a 20th century acceleration in global sea level rise 1 multi century sea level records and climate models indicate an acceleration of sea level rise but no 20th century acceleration has previously been detected a reconstruction of global sea level using tide gauge data from 1950 to 2000 indicates a larger rate of rise after 1993 and other periods of rapid sea level rise but no significant acceleration over this period here we extend the reconstruction of global mean sea level back to 1870 and find a sea level rise from january 1870 to december 2004 of 195 mm a 20th century rate of sea level rise of 1 7 0 3 mm yr 1 and a significant acceleration of sea level rise of 0 013 0 006 mm yr 2 this acceleration is an important confirmation of climate change simulations which show an acceleration not previously observed if this acceleration remained constant then the 1990 to 2100 rise would range from 280 to 340 mm consistent with projections in the ipcc tar

motion of the philippine sea plate consistent with the nuvel 1a model summary we determine euler vectors for 12 plates including the philippine sea plate ph relative to the fixed pacific plate pa by inverting the earthquake slip vectors along the boundaries of the philippine sea plate gps observed velocities and 1122 data from the nuvel 1 and the nuvel 1a global plate motion model respectively this analysis thus also yields euler vectors for the philippine sea plate relative to adjacent plates our results are consistent with observed data and can satisfy the geological and geophysical constraints along the caroline cr ph and pa cr boundaries the results also give insight into internal deformation of the philippine sea plate the area enclosed by the ryukyu trench nankai trough izu bonin trench and gps stations s102 s063 and okino torishima moves uniformly as a rigid plate but the areas near the philippine trench mariana trough and yap palau trench have obvious deformation

frequency dependent relocation of the 1992 nicaragua slow earthquake an empirical green s function approach we present a two step empirical green s function analysis of the slow 1992 nicaragua earthquake mw 7 7 in the first step a narrow band cross correlation method recovers he relative source amplitude and phase delay spectra between the main shock and a suitable empirical green s function egf the analysis is performed at 2mhz intervals from 4 to 44mhz using first and second orbit fundamental mode rayleigh waves from the low frequency relative amplitudes we obtain the differences in mechanism and depth between the main shock and the egf and we present a method to correct for such differences in the second step we use the relative spectra to relocate the main shock relative to the egf position al a set of discrete frequencies in addition we invert the relative spectra for the relative source time functions using both a positivity and a smoothing constraint unlike standard egf deconvolution the spectral resolution achieved in our cross correlation method allows us to determine the conditions of validity of the egf approach from our analysis it appears that the centre of low frequency radiation 4 10 mhz during the slow 1 992 nicaragua earthquake is situated about 40 km trenchwards of the epicentre between 20 and 44 mhz centroids occupy intermediate positions between the low frequency points and the epicentre relative source time functions have an average duration of about 120 s they reveal a slow 1 km s1 smooth component of rupture with unilateral directivity towards the se along the trench axis a large amount of slip occurred at shallow depths at the interface between the subducted cocos plate and the caribbean plate in agreement with tsunami models of the event the low frequency radiation appears to originate from a zone devoid of teleseismic aftershocks this suggests that unusual frictional properties at the plate interface perhaps related to subducted sediments are responsible for the slow and smooth nature of the 1992 nicaragua earthquake

slab segmentation and late cenozoic disruption of the hellenic arc the hellenic subduction zone displays well defined temporal and spatial variations in subduction rate and offers an excellent natural laboratory for studying the interaction among slab buoyancy subduction rate and tectonic deformation in space the active hellenic subduction front is dextrally offset by 100 120 km across the kephalonia transform zone coinciding with the junction of a slowly subducting adriatic continental lithosphere in the north 5 10 mm yr and a rapidly subducting ionian oceanic lithosphere in the south 35 mm yr subduction rates can be shown to have decreased from late eocene time onward reaching 5 12 mm yr by late miocene time before increasing again along the southern portion of the subduction system geodynamic modeling demonstrates that the differing rates of subduction and the resultant trench offset arise naturally from subduction of oceanic pindos lithosphere until late eocene time followed by subduction of a broad tract of continental or transitional lithosphere hellenic external carbonate platform and then by miocene entry of high density oceanic ionian lithosphere into the southern hellenic trench model results yield an initiation age for the kephalonia transform of 6 8 ma in good agreement with observations consistency between geodynamic model results and geologic observations suggest that the middle miocene and younger deformation of the hellenic upper plate including formation of the central hellenic shear zone can be quantitatively understood as the result of spatial variations in the buoyancy of the subducting slab using this assumption we make late eocene middle miocene and pliocene reconstructions of the hellenic system that include quantitative constraints from subduction modeling and geologic constraints on the timing and mode of upper plate deformation

seismic body wave constraint on mechanisms of intermediate depth earthquakes 1 source parameters of six large earthquakes 7 1 mw 7 7 in the depth range between 112 and 277 km from five different subduction zones are derived from teleseismic body waves recorded by global seismic networks except for the 21 october 1995 mexican event which is consistent with the model of simple rupture on a planar surface the investigated earthquakes show complex rupture processes that can be explained by irregularities in the focal region as is the case of shallow events the inferred velocity of the moment release varies between 2 5 and 4 km s corresponding to 40 90 of the shear velocity at the focus four of the six earthquakes show stress drops in the range observed for shallow events 1 10 mpa ruptures extend mainly parallel to the strike of subducting slabs with dimensions reaching up to 50 km the extent of rupture perpendicular to slab dip of generally less than 15 km is comparatively small this suggests that the rupture during large intermediate depth earthquakes propagates predominantly parallel to the strike of the subducting plate and that the seismogenic zone perpendicular to the dip direction is limited to a narrow width the relatively small rupture size perpendicular to slab dip suggests that the rupture process does not extend into regions of significantly different temperatures the spatial extent of the investigated earthquakes is consistent with the orientation of trench parallel faults that are generally observed in near trench outer rise regions suggesting that these events may result from reactivation of such preexisting faults at intermediate depths through dehydration of hydrous minerals concentrated in these zones of weakness depths of most of the earthquakes are consistent with the dehydration embrittlement of serpentine the bolivian earthquake of 23 january 1997 seems to be too deep 277 km for such an explanation

new estimates of secular sea level rise from tide gauge data and gia modelling summary during the last three decades at least 30 independent estimates of the secular global mean sea level rise gmslr have been published based on sufficiently long tide gauge tg records despite its apparent simplicity the problem of gmslr is fraught with a number of difficulties which make it one of the most challenging questions of climate change science not surprisingly published estimates show considerable scatter with rates ranging between 1 and 2 mm yr 1 for observations on the century timescale in previous work the importance of glacial isostatic adjustment gia upon the assessment of the gmslr has been clearly demonstrated in particular starting from the 1980s gia models have been routinely employed to decontaminate tg observations from the effects of melting of the late pleistocene ice sheets to fully highlight the sea level variations driven by climate change however uncertainties associated with the earth s rheological profile and the time history of the past continental ice sheets can propagate into the gia corrections after revisiting previous work and estimates we suggest a significant modification of the criteria for the selection of the tgs which are most suitable for the robust assessment of the secular gmslr in particular we seek a set of tgs for which gia corrections are essentially independent of the parametrization of the rheological profile of the earth s mantle and of the detailed time chronology of surface loading this insensitivity is established by considering predictions based upon three gia models widely employed in the recent literature namely ice 3g ice 5g and the one developed at the research school of earth sciences of the national australian university applying this approach and selection criteria previously proposed in the literature we identify a set of 22 sufficiently evenly distributed tgs by simple statistical methods these records yield a preferred gia independent gmslr estimate since 1880 namely 1 5 0 1 mm yr 1 rms 0 4 mm yr 1 wrms 0 3 mm yr 1 this value is consistent with various previous estimates based on secular tg observations and with that proposed for the 20th century by the intergovernmental panel on climate change ipcc fourth assessment report 1 7 0 5 mm yr 1

centroid moment tensor solutions for april june 1992 abstract centroid moment tensor solutions are presented for 245 earthquakes that occurred during the second quarter of 1992 the solutions are obtained using corrections for aspherical earth structure represented by a whole mantle shear velocity model sh8 u4l8 of dziewonski and woodward the solution for an earthquake under mindanao philippines on 9 may represents the 10 000th event in the cmt catalogue

neogene uplift of central eastern patagonia dynamic response to active spreading ridge subduction the chile triple junction ctj episodically migrated northward during the past 14 ma from 54 s to its present day position at 46 30 s as different almost trench parallel spreading segments entered in subduction this migration resulted in the opening of an asthenospheric window below patagonia inducing a disturbance in the regional mantle convection on the overriding plate the middle miocene time corresponds to a major change in the central patagonian basin dynamics with a transition from subsidence to generalized uplift the detailed mapping and the morphological study of post middle miocene terraces evidence regional scale trench parallel tilt histories that differ depending on latitude south of 46 30 s the slopes of the fluvial terraces indicate a change from northward to southward tilt during late miocene terraces younger than the early pliocene do not show any trench parallel tilt north of 46 30 s in contrast only northward tilt active until the pleistocene is recorded we use a semianalytical model of dynamic topography which suggests that the northward migration of the chile triple junction should be accompanied by a dynamic uplift of the central patagonian basin uplift would cause both north directed and south directed tilt north and south of the triple junction respectively with values of 0 1 0 2 500 km east of the trench tilt measured in the southeastern part of the central patagonian basin 0 1 is comparable to values predicted using the semianalytical model the dynamic topography associated to the chile ridge subduction may have exerted a major control on the neogene dynamics of patagonia

an experiment in systematic study of global seismicity centroid moment tensor solutions for 201 moderate and large earthquakes of 1981 data from the global digital seismograph network were used to obtain centroid moment tensor solutions using the method of dziewonski et al 1981 results were obtained for 201 earthquakes ranging in seismic moment from 7 1023 to 3 1027 dyne cm the wide dynamic range of the sro asro stations allows us to investigate using the same algorithm series of events among which the smallest and the largest may differ in moment by a factor as large as 1000 among the events studied is a particularly interesting series in january 1981 off the island of honshu the main shock was preceded by three foreshocks and followed by four aftershocks all falling within the range of our analysis there is an indication that the source mechanism changes with the size of the event statistical analysis of the results for all earthquakes reveals that the half duration of shallow and intermediate events is approximated by 1 6 10 8 m01 3 the shifts in origin time for deep focus earthquakes are indicative of the general complexity of these events which depends only weakly on the seismic moment the extreme departures from a double couple mechanism seem to depend both on the moment and on the focal depth while for shallow earthquakes these departures decrease from a maximum at about 1025 dyne cm with increasing moment the reverse appears to be true with respect to deep focus earthquakes shallow earthquakes north of new guinea and along the solomon islands show systematic and substantial departures from the double couple mechanism

facies analysis of yedoma thermokarst lakes on the northern seward peninsula alaska thermokarst lakes develop as a result of the thaw and collapse of ice rich permanently frozen ground permafrost of particular sedimentological importance are thermokarst lakes forming in late pleistocene icy silt yedoma which dramatically alter the land surface by lowering surface elevation and redistributing upland sediment into lower basins our study provides the first description of yedoma thermokarst lake sedimentology based on the cross basin sampling of an existing lake we present lake sediment facies descriptions based on data from sediment cores from two thermokarst lakes of medium depth claudi and jaeger informal names which formed in previously non thermokarst affected upland yedoma on the northern seward peninsula alaska we identify four prominent facies using sedimentological biogeochemical and macrofossil indicators a massive silt lacking aquatic macrofossils and other aquatic indicators situated below a sub lacustrine unconformity facies 1 two basal deposits interbedded organic silt and chaotic silt facies 2 3 and a silt rich mud facies 4 facies 1 is interpreted as yedoma that has thawed during lake formation facies 3 formed adjacent to the margin due to thaw and collapse events from the lake shore material from facies 3 was reworked by wave action to form facies 2 in a medium energy margin environment facies 4 formed in a lower energy environment toward the lake basin center this facies classification and description should enhance our ability i to interpret the spatial and temporal development of lakes and ii to reconstruct long term patterns of landscape change

analysis and automatic processing in near field of eight 1992 1994 tsunamigenic earthquakes improvements towards real time tsunami warning we study eight tsunamigenic earthquakes of 1992 1994 with data from single near field 3 component long period stations the analysis is made from the standpoint of tsunami warning by an automatic process which estimates the epicentral location and the seismic moment through the variable period mantle magnitude m m simulations of early warning based on the real time computation of the seismic moment are also tested with this system which would give a justified warning in each region of tsunami potentiality by exploiting the dependence of moment rate release with frequency the system has the capability of recognizing both tsunami earthquakes such as the 1992 nicaragua and 1994 java events as well as instances of the opposite case of low frequency deficiency interpreted as indicating a deeper than normal source 1993 guam event we report both the results of delayed time processing of the near field stations and the actual real time warnings at ppt which confirm the former

probabilistic surface reconstruction of coastal sea level rise during the twentieth century we present a new surface reconstruction procedure based on the bayesian inference method for coastal relative sea level variation during the twentieth century average rates are computed from tide gauge records models based on a voronoi tessellation adapt to the level of information which proves well suited to the strong heterogeneity of data each point of the reconstructed surface is defined through a probability density function a format particularly well adapted to this climate related datum the resolution of reconstructed surfaces strongly varies among the six large regions considered and within a given region anomalous sea level variations recorded locally are shown to reflect either anthropogenic effects or well identified fast tectonics for a poor data coverage these can cause a problematic distortion of the reconstructed surface europe north america australia and africa present a single trend with a decreasing precision of the reconstructed surface as a function of resolution of the tide gauge record the most prominent feature in europe is the pronounced uplift of fennoscandia coasts of united states have the best resolution in north america and present stronger rates of sea level rise on the atlantic than their european counterparts australia especially in the north and africa are poorly resolved asia and south america depart clearly from this trend a relatively uniform rise is obtained for asia in spite of a good tide gauge record conversely the reconstructed surface for south america presents an exceptional degree of roughness at odds with a relatively poor record overall this method not only offers a new assessment of sea level change validating earlier results but also quantifies the reliability of estimates

source discriminants for near field tsunamis summary we present numerical simulations of tsunami run up in the near field for a data set of 72 models of sources involving both seismic dislocations and landslides by varying one by one the parameters describing the source and the receiving beach we are able to separate their individual influence on the amplitude and distribution of run up which we characterize by forming several dimensionless parameters principally the ratio i 2 of its maximum amplitude to its lateral extent along the beach we find that i 2 remains less than 10 4 for seismic dislocation sources but is greater than this threshold for all physically realistic models of underwater landslides thus it can be used as a discriminant for the nature of the source of a near field tsunami for seismic dislocations we also consider the ratio i 1 of maximum run up to seismic slip on the fault plane and validate numerically the previously suggested rule of thumb that this ratio cannot be much greater than 1 in the case of underwater landslides we show that the distribution of near field run up is primarily controlled by the 2 d wall of water displaced on the ocean surface as an initial condition to the simulation and is practically independent of its extension in the third dimension perpendicular to the beach we apply this approach to nine profiles of tsunami run up obtained experimentally during recent field surveys and show that our method successfully identifies the 1998 papua new guinea tsunami as having been generated by an underwater landslide thus confirming the results of shipboard and hydroacoustic investigations it also strongly suggests a similar mechanism for the generation of the near field aleutian tsunami of 1946 april 1