validation and joint inversion of teleseismic waveforms for earthquake source models using deep ocean bottom pressure records a case study of the 2006 kuril megathrust earthquake the importance of accurate tsunami simulation has increased since the 2004 sumatra andaman earthquake and the indian ocean tsunami that followed it because it is an important tool for inundation mapping and potentially tsunami warning an important source of uncertainty in tsunami simulations is the source model which is often estimated from some combination of seismic geodetic or geological data a magnitude 8 3 earthquake that occurred in the kuril subduction zone on 15 november 2006 resulted in the first teletsunami to be widely recorded by bottom pressure recorders deployed in the northern pacific ocean because these recordings were unaffected by shallow complicated bathymetry near the coast this provides a unique opportunity to investigate whether seismic rupture models can be inferred from teleseismic waves with sufficient accuracy to be used to forecast teletsunami in this study we estimated the rupture model of the 2006 kuril earthquake by inverting the teleseimic waves and used that to model the tsunami source the tsunami propagation was then calculated by solving the linear long wave equations we found that the simulated 2006 kuril tsunami compared very well to the ocean bottom recordings when simultaneously using p and long period surface waves in the earthquake source process inversion

forearc collapse plate flexure and seismicity within the downgoing plate along the sunda arc west of sumatra deformation within the downgoing oceanic lithosphere seawards of subduction zones is typically characterised by regimes of shallow extension and deeper compression due to the bending of the oceanic plate as it dips into the subduction zone however offshore sumatra there are shallow compressional earthquakes within the downgoing oceanic plate outboard of the region of high slip in the 2004 aceh andaman earthquake occurring at the same depth as extensional faulting further seaward from the trench a clear separation is seen in the location of intraplate earthquakes with extensional earthquakes occurring further seawards than compressional earthquakes at the same depth within the plate the adjacent section of the forearc prism west of aceh is also anomalous in its morphology characterised by a wide prism with a steep bathymetric front and broad gradually sloping top this shape is in contrast to the narrower and more smoothly sloping prism to the south and along other subduction zones the anomalous near trench intraplate earthquakes and prism morphology are likely to be the result of the geologically rapid gravitational collapse of the forearc which leads to induced bending within the subducting plate and the distinctive plateau like morphology of the forearc such collapse of the forearc could be caused by changes through time of the material properties of the forearc rocks or of the thickness of the sediments entering the subduction zone

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

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

low vp vs ratios in the crust and upper mantle beneath the sea of okhotsk inferred from teleseismic pmp smp and sms underside reflections from the moho 1 teleseismic ground motion recordings of deep earthquakes often contain clear seismic wave reflections from the free surface above the source pp sp ss with isolated precursors pmp smp and sms produced by underside reflections from the moho the crust mantle boundary below the free surface reflection points the waveforms of the depth phases and their precursors are readily modeled providing constraints for steep angles of incidence on integrated two way crustal travel times and moho shear and compressional impedance contrasts above deep earthquake source regions we model surface reflection waveforms in stacks of three component long period wwssn and digital broadband seismograms for signals traversing the crust and upper mantle beneath the sea of okhotsk which overlies deep earthquakes in the subducted kurile slab the crust beneath most of the sea of okhotsk is 19 25 km thick indicating a submerged continental margin with minor crustal thinning toward the kuril back arc basin where thin oceanic crust is found modeling pmp and sms phases that sample the same subregion provides tight constraints on the vp vs ratio in the crust and uppermost mantle assuming common density structure and consistent crustal thickness for p and s waves the absolute velocities are not constrained by the data we find unusually low vp vs ratios in the range 1 6 1 7 for the uppermost mantle under the sea of okhotsk and comparably low average vp vs ratios for the crust in several regions the presence of fluids and extensive silica enrichment possibly involving low temperature veining are viable explanations for the anomalous vp vs ratios this may represent an important process of continentalization taking place landward from the volcanic arc in subduction zones

seismic moment catalog of large shallow earthquakes 1900 to 1989 we compile a worldwide catalog of shallow depth 70 km and large ms 7 earthquakes recorded between 1900 and 1989 the catalog is shown to be complete and uniform at the 20 sec surface wave magnitude ms 7 0 we base our catalog on those of abe 1981 1984 and abe and noguchi 1983a b for events with ms 7 0 those catalogs however are not homogeneous in seismicity rates for the entire 90 year period we assume that global rates of seismicity are constant on a time scale of decades and most inhomogeneities arise from changes in instrumentation and or reporting we correct the magnitudes to produce a homogeneous catalog the catalog is accompanied by a reference list for all the events with seismic moment determined at periods longer than 20 sec using these seismic moments for great and giant earthquakes and a moment magnitude relationship for smaller events we produce a seismic moment catalog for large earthquakes from 1900 to 1989 the catalog is used to study the distribution of moment released worldwide although we assumed a constant rate of seismicity on a global basis the rate of moment release has not been constant for the 90 year period because the latter is dominated by the few largest earthquakes we find that the seismic moment released at subduction zones during this century constitutes 90 of all the moment released by large shallow earthquakes on a global basis the seismic moment released in the largest event that occurred during this century the 1960 southern chile earthquake represents about 30 to 45 of the total moment released from 1900 through 1989 a frequency size distribution of earthquakes with seismic moment yields an average slope b value that changes from 1 04 for magnitudes between 7 0 and 7 5 to b 1 51 for magnitudes between 7 6 and 8 0 this change in the b value is attributed to different scaling relationships between bounded large and unbounded small earthquakes thus the earthquake process does have a characteristic length scale that is set by the downdip width over which rupture in earthquakes can occur that width is typically greater for thrust events at subduction zones than for earthquakes along transform faults and other tectonic environments

temporal variation of large intraplate earthquakes in coupled subduction zones the focal mechanisms of intraplate earthquakes within subducting lithosphere are frequently used to infer large scale stress regimes induced by slab pull bending or unbending and lateral segmentation and undulations of the slab numerous studies have further postulated that the intraplate activity is influenced by transitory regional stress regimes such as those associated with interplate thrust events temporal variations of the latter type may potentially play an important role in assessing regions of uncertain seismic potential and possibly even in earthquake forecasting a systematic analysis of 1130 focal mechanisms for intraplate earthquakes with m b 5 0 in the depth range 0 300 km is conducted for nine circum pacific subduction zones all of which are known to have large interplate thrust events the spatial and temporal relationships of the earthquakes within the subducting slab to the large thrust events in each region are appraised the earthquake catalog assembled contains all published focal mechanisms and is probably complete for m b 6 5 for the years 1963 1986 for many of the localized regions considered in detail the catalog is complete to lower thresholds of m b 6 0 or m b 5 5 this analysis provides compelling evidence for a temporal link between large interplate thrust activity and intraplate seismicity for the seismically coupled regions considered here outer rise compressional events have occurred prior to several large thrust events or are associated with seismic gaps while outer rise tensional events generally only follow interplate ruptures in the intermediate depth range large down dip tensional events generally precede interplate thrusts and are often concentrated at the down dip edge of the coupled zone a transition to down dip compressional stress or diminished tensional activity at intermediate depth is observed after several large thrust events e g 1960 chile 1974 peru 1957 aleutian 1971 new britain these examples support the notion that the intraplate stress environment responds viscoelastically to the temporally varying interplate stress regime assuming that this concept is correct the seismic potential of several seismic gaps is considered on the basis of both outer rise and intermediate depth earthquake activity

the wake of st vincent abstract the island of st vincent and the other windward islands in the southeastern caribbean were chosen as a field site for the study of weak mountain wakes by the authors definition a weak wake forms when the potential vorticity generated by a mountain is not strong enough to advect itself into eddies rather it is simply advected downstream by the ambient flow goes 8 and landsat sunglint images unambiguously revealed that the mountainous windward islands have remarkably long straight wakes the length of st vincent s wake exceeds 300 km although its width is only 20 km near the islands the wake structures reflect the details of the island topography these wakes do not exhibit any obvious diurnal effect boat surveys in the lee of st vincent confirmed the existence of features seen in the images the sharp wake boundary the small valley induced jet embedded in the near wake and the absence of any reverse flow aircraft surveys gave evidence of descent over the island and showed that the

quantitative estimates of interplate coupling inferred from outer rise earthquakes interplate coupling plays an important role in the seismogenesis of great interplate earthquakes at subduction zones the spatial and temporal variations of such coupling control the patterns of subduction zone seismicity we calculate stresses in the outer rise based on a model of oceanic plate bending and coupling at the interplate contact to quantitatively estimate the degree of interplate coupling for the tonga new hebrides kurile kamchatka and marianas subduction zones depths and focal mechanisms of outer rise earthquakes are used to constrain the stress models we perform waveform modeling of body waves from the gdsn network to obtain reliable focal depth estimates for 24 outer rise earthquakes a propagator matrix technique is used to calculate outer rise stresses in a bending 2 d elastic plate floating on a weak mantle the modeling of normal and tangential loads simulates the total vertical and shear forces acting on the subducting plate we estimate the interplate coupling by searching for an optimal tangential load at the plate interface that causes the corresponding stress regime within the plate to best fit the earthquake mechanisms in depth and location

influence of the earthquake cycle and lithospheric rheology on the dynamics of the eastern california shear zone the eastern california shear zone is bounded by the high heat flow region of the basin and range province and the low heat flow region of the sierra nevada block this difference in thermal state influences the rheology of the lower crust upper mantle resulting in a viscosity contrast between the two regions we analyze the effect of such a contrast on the kinematics and dynamics of the shear zone with numerical models this viscosity contrast drives asymmetric strain accumulation in the upper crust producing an asymmetric surface velocity field an additional consequence of this strain pattern is the potential for asymmetric co seismic displacement during an earthquake

basin centered asperities in great subduction zone earthquakes a link between slip subsidence and subduction erosion 1 published areas of high coseismic slip or asperities for 29 of the largest circum pacific megathrust earthquakes are compared to forearc structure revealed by satellite free air gravity bathymetry and seismic profiling on average 71 of an earthquake s seismic moment and 79 of its asperity area occur beneath the prominent gravity low outlining the deep sea terrace 57 of an earthquake s asperity area on average occurs beneath the forearc basins that lie within the deep sea terrace in sw japan slip in the 1923 1944 1946 and 1968 earthquakes was largely centered beneath five forearc basins whose landward edge overlies the 350 c isotherm on the plate boundary the inferred downdip limit of the locked zone basin centered coseismic slip also occurred along the aleutian mexico peru and chile subduction zones but was ambiguous for the great 1964 alaska earthquake beneath intrabasin structural highs seismic slip tends to be lower possibly due to higher temperatures and fluid pressures kilometers of late cenozoic subsidence and crustal thinning above some of the source zones are indicated by seismic profiling and drilling and are thought to be caused by basal subduction erosion the deep sea terraces and basins may evolve not just by growth of the outer arc high but also by interseismic subsidence not recovered during earthquakes basin centered asperities could indicate a link between subsidence subduction erosion and seismogenesis whatever the cause forearc basins may be useful indicators of long term seismic moment release the source zone for cascadia s 1700 a d earthquake contains five large basin centered gravity lows that may indicate potential asperities at depth the gravity gradient marking the inferred downdip limit to large coseismic slip lies offshore except in northwestern washington where the low extends landward beneath the coast transverse gravity highs between the basins suggest that the margin is seismically segmented and could produce a variety of large earthquakes

the 2011 northern kermadec earthquake doublet and subduction zone faulting interactions 1 a large intraslab earthquake doublet 6 july 2011 mw 7 6 21 october 2011 mw 7 4 occurred in the pacific plate beneath the outer trench slope of the northern kermadec subduction zone seaward of an interseismically coupled region of the megathrust the first large event a shallow 24 km centroid depth normal faulting rupture was followed by intraslab aftershocks within minutes and by aftershocks near the megathrust within hours the second large event a deeper 45 km centroid depth thrust faulting rupture below the northern portion of the first rupture plane was also followed by interplate and intraslab aftershocks the last large interplate activity in northern kermadec involved an underthrusting doublet on 14 january 1976 mw 7 8 7 9 previous studies interpret westward movement of the northern kermadec arc relative to the australian plate from gps measurements to be a result of interseismic coupling on the northern kermadec megathrust a locked plate interface in this region should tend to reduce trench slope extensional stresses coulomb stress change calculations using a finite fault model determined from teleseismic body wave inversions for the normal faulting event in the 2011 doublet favor activation of megathrust faulting coulomb stress changes for the october compressional event appear to reduce interplate thrust activity and for a short time reversed the westward motion of the upper plate the net effect of the doublet is a few bar increase of interplate thrust fault driving stress which may have advanced a future large megathrust event intraslab normal faulting may serve as a harbinger not only a response to large megathrust ruptures

observational constraints on the fracture energy of subduction zone earthquakes we relate seismologically observable parameters such as radiated energy seismic moment rupture area and rupture speed to the dynamics of faulting to achieve this objective we computed the radiated energy for 23 subduction zone earthquakes recorded between 1992 and 2001 most of these earthquakes have a magnitude m w 7 5 but we also included some smaller m w 6 7 well studied subduction zone earthquakes and six crustal earthquakes we compiled static stress drop estimates for these 29 earthquakes from literature and used a slip weakening model to determine the radiation efficiency of these earthquakes we also determined the rupture speed of these earthquakes from literature from fracture mechanics fracture energy and hence radiation efficiency can be related to the rupture speed the radiation efficiencies estimated from the partitioning of energy as given by the slip weakening model are consistent with the rupture speed estimated for these earthquakes most earthquakes have radiation efficiencies between 0 25 and 1 and are hence efficient in generating seismic waves but tsunami earthquakes and two deep earthquakes the 1994 bolivia and the 1999 russia china border earthquakes have very small radiation efficiencies 0 25 and hence dissipate a large amount of energy during faulting we suggest that differences in the radiation efficiencies of different types of earthquakes could be due to fundamental differences in their rupture mechanics in deep events the energy is probably dissipated in thermal processes in the fault zone while it is possible that the morphology of the trench causes large energy dissipation during the rupture process of tsunami earthquakes

influence of fore arc structure on the extent of great subduction zone earthquakes 1 structural features associated with fore arc basins appear to strongly influence the rupture processes of large subduction zone earthquakes recent studies demonstrated that a significant percentage of the global seismic moment release on subduction zone thrust faults is concentrated beneath the gravity lows resulting from fore arc basins to better determine the nature of this correlation and to examine its effect on rupture directivity and termination we estimated the rupture areas of a set of mw 7 5 8 7 earthquakes that occurred in circum pacific subduction zones we compare synthetic and observed seismograms by measuring frequency dependent amplitude and arrival time differences of the first orbit rayleigh waves at low frequencies the amplitude anomalies primarily result from the spatial and temporal extent of the rupture we then invert the amplitude and arrival time measurements to estimate the second moments of the slip distribution which describe the rupture length width duration and propagation velocity of each earthquake comparing the rupture areas to the trench parallel gravity anomaly tpga above each rupture we find that in 11 of the 15 events considered in this study the tpga increases between the centroid and the limits of the rupture thus local increases in tpga appear to be related to the physical conditions along the plate interface that favor rupture termination owing to the inherently long timescales required for forearc basin formation the correlation between the tpga field and rupture termination regions indicates that long lived material heterogeneity rather than short timescale stress heterogeneities are responsible for arresting most great subduction zone ruptures

gap flows through idealized topography part ii effects of rotation and surface friction numerical simulations are conducted of geostrophically balanced flow over an isolated mountain cut by a horizontal gap the relative importance of the along gap synoptic scale pressure gradient and terraininduced mesoscale circulations for the generation of gap winds was examined by changing the direction of the synoptic scale wind relative to the topography in all cases the forcing associated with mesoscale circulations generated by the mountain was at least as significant as the synoptic scale pressure gradient in the cases where a component of the large scale flow was directed perpendicular to the ridge the dynamics were dominated by either the vertical momentum fluxes due to mountain lee waves or by mesoscale pressure gradients associated with upstream blocking or lee troughing mesoscale circulations were also important when the large scale flow was parallel to the ridge because surface friction turned the low level winds toward the high pressure side of the ridge partially blocking the flow and enhancing the along gap pressure gradient the flow in the interior of a very long uniform gap was also simulated for a case with the synoptic scale winds parallel to the ridge so that the synoptic scale pressure gradient was down the gap the flow in the interior of the long gap was not horizontal and not in a simple dynamical balance between acceleration the pressure gradient force and surface friction even the flow in the lowest 150 m was gradually subsiding subsidence and lateral momentum flux convergence at low levels near the center of the gap were important contributors to the mass and along gap momentum budgets

regional and teleseismic double difference earthquake relocation using waveform cross correlation and global bulletin data 1 we have developed a double difference algorithm to relocate earthquakes recorded at global seismic networks using differential arrival times for first and later arriving regional and global phases to invert for the vectors connecting the hypocenters differential times are formed from global seismic bulletins and are accurately measured on similar seismograms by time domain waveform cross correlation we evaluate the performance of this spherical multiphase double difference algorithm using three dimensional regional scale synthetic data and two sets of earthquake data in different tectonic settings the first includes 3783 intermediate depth earthquakes that occurred between 1964 and 2000 in the subducting nazca plate beneath northern chile where the relocated seismicity confirms a narrowly spaced double seismic zone previously imaged with temporary local seismic data residual statistics and comparison with accurately known locations indicate mean relative location errors at the 90 confidence level of 2 4 km laterally and 1 8 km vertically later events typically constrained by cross correlation data have errors of 1 6 km laterally and 1 4 km vertically the second data set includes 75 crustal earthquakes in the 1999 izmit and duzce turkey aftershock sequences where the double difference solutions image orientation and dip of individual fault segments that are consistent with focal mechanisms and near surface information fault complexity likely causes a low level of waveform similarity in this aftershock sequence and thus generates fewer correlated events compared to the chile earthquakes differences between the double difference locations and corresponding locations in global seismicity catalogs earthquake data report edr international seismological centre isc engdahl hilst buland ehb are typically greater than 10 km we evaluate the potential of cross correlation and double difference methods to improve hypocenter locations on a global scale

seismology energy radiation from the sumatra earthquake we determined the duration of high frequency energy radiation from indonesia s great sumatra andaman earthquake 26 december 2004 to be about 500 seconds this duration can be translated into a rupture length of about 1 200 km which is more than twice as long as that inferred from body wave analyses performed soon after the event our analysis was able rapidly to define the extent of rupture thereby aiding the assessment of seismic hazard in the immediate future

source inversion of w phase speeding up seismic tsunami warning w phase is a long period phase arriving before s wave it can be interpreted as superposition of the fundamental first second and third overtones of spheroidal modes or rayleigh waves and has a group velocity from 4 5 to 9 km s 1 over a period range of 100 1000 s the amplitude of long period waves better represents the tsunami potential of an earthquake because of the fast group velocity of w phase most of w phase energy is contained within a short time window after the arrival of the p wave at a distance of 50 w phase energy is contained within 23 min after the origin time which is the distinct advantage of using w phase for rapid tsunami warning purposes we use a time domain deconvolution method to extract w phases from the broad band records of global seismic networks the bandwidth of w phase is approximately from 0 001 to 0 01 hz and we bandpass filter the data from 0 001 to 0 005 hz in most cases having extracted w phase from the vertical component records we perform a linear inversion using a point source to determine mw and the source mechanism for several large earthquakes including the 2004 sumatra andaman earthquake the 2005 nias earthquake the 2006 kuril is earthquake and the 2007 sumatra earthquake w phase inversion yields reliable solutions and holds promise of the use of w phase for rapid assessment of tsunami potential

intraplate and interplate faulting interactions during the august 31 2012 philippine trench earthquake mw 7 6 sequence on august 31 2012 a large m w 7 6 thrust earthquake occurred within the subducting philippine sea plate seaward of a low seismicity region of the plate boundary 9 5 n 11 5 n possibly as a result of horizontal compressional stress accumulation offshore of a locked megathrust the mainshock ruptured from 30 50 km depth with high radiated energy seismic moment ratio and enriched short period p wave radiation the nine largest aftershocks with global centroid moment tensor solutions m w 5 2 5 6 were shallow 10 13 km normal faulting outer rise events and a waveform template analysis using regional broadband data indicates many 48 110 similar normal faulting events m b 4 0 5 5 and a few 8 110 likely shallow thrust faulting events on the megathrust with additional very small unidentified events coulomb stress perturbations may contribute to the mix of intraplate and interplate faulting geodetic assessment of any slip deficit on the megathrust is essential for quantifying the potential for a future large interplate rupture in this region

long term seismic observations along myanmar sunda subduction margin insights for 2004 m w 9 0 earthquake the present study investigates the temporal variation of few seismic parameters between the myanmar zone i andaman nicobar northwest sumatra zone ii southeast sumatra west indonesia zone iii and east indonesia zone iv converging boundaries in reference to the generation of 26 december 2004 mw 9 0 off sumatra mega earthquake event the four segments are distinguished based on tectonics parameters distinct geological locations great earthquake occurrences and the wadati benioff zone characteristics two important seismic parameters such as seismic energy and b values are computed over a time window of 6 month period during the entire 1976 2013 period for these segments the b values show a constant decrease in zones ii iii and iv whereas the zone i does not show any such pattern prior to the 2004 mega event the release of seismic energy was also gradually decreasing in zones ii and iii till the 2004 event and little similar pattern was also noted in zone iv this distinct observation might be indicating that the stress accumulation was dominant near the sumatra java area located towards southeast of zone ii and northwest of zone iii the released strain energy during the 2004 event was subsequently migrated towards north rupturing 1300 km of the boundary between the northwest sumatra and the north andaman the occurrence of 2004 mega event was apparently concealed behind the long term seismic quiescence existing near the sumatra and nicobar margin a systematic study of the patterns of seismic energy release and b values and the long term observation of collective behaviour of the margin tectonics might have had given clues to the possibility of the 2004 mega event

source process of the great 1977 sumba earthquake in order to investigate the applicability of the asperity model to intraplate earthquakes we have studied the rupture process of the great 1977 sumba normal faulting earthquake mw 8 2 8 3 one of the largest earthquakes since 1963 this event has been variously interpreted as a plate detachment event i e rupture through the entire lithosphere or a shallow plate bending event we have analyzed long period body waves in order to determine the spatiotemporal rupture characteristics including the depth extent of the rupture area visible depth phases in the initial stage of weak radiation beginning about 15 s before the main pulse suggest that the earthquake nucleated near 29 km depth which corresponds to the maximum depth of the aftershock sequence the excitation of a strong tsunami implies that rupture extends to the surface while deconvolutions of long period p waves suggest a relatively shallow 50 km maximum depth extent however the existence of slip below this depth cannot be ruled out particularly if it preferentially radiates frequencies below the passband of the body waves used 0 02 hz for undiffracted phases the source time function of the principal rupture which initiated 30 km west of the epicenter of the precursor comprises a dominant initial short duration 24 s triangular pulse followed by several smaller pulses however slightly diffracted phases indicate a simple basic underlying character for the rupture consisting of the initial 24 s triangle superimposed on a longer duration 42 44 s trapezoid the absence of observable directivity in the deconvolved source time functions suggests a bilateral rupture mode although the body waves do not require a fault length greater than 80 km the aftershock area and surface wave results of zhang and kanamori 1988 imply a total length of at least 200 km the body wave source functions are well modeled by a 200 km long fault extending to 30 50 km depth on which slip nucleates at the center of the fault and has variable displacement along strike the peak moment release of the deconvolved source functions indicates higher displacement in the hypocentral area than in other areas of the fault the spatial relationship of the precursor and the main pulse is suggestive of rupture initiating at and propagating along the edge of an asperity prior to the rupture of the asperity itself the large size of the event may be due to an unusual stress environment arising from strong lateral gradients in seismic interplate coupling along the java timor arc

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

multiple branching rupture of the 2009 tonga samoa earthquake several source models have been proposed to explain the enigmatic 2009 tonga samoa earthquake the long period data require a composite source model and can be fit with a normal faulting subevent followed by one or more reverse faulting subevents the short period data in contrast indicate a more compact rupture pattern around the epicenter the lack of a unified source model reflects the complexity of the event we analyze the spatiotemporal evolution of this earthquake with p wave back projection from globally distributed stations in different frequency bands low frequency 0 05 0 2 hz high frequency 0 2 2 hz and a multiple moment tensor inversion the rupture propagation revealed by back projection exhibits frequency dependent behavior with two branches of high frequency enriched bilateral rupture around the epicenter and a high frequency deficient rupture branch at the subduction interface a composite source model with one mw 8 0 normal faulting earthquake east of the trench axis seaward followed by one mw 8 1 reverse faulting earthquake along the subduction interface west of the trench axis landward can explain the very long period data 200 500 s combined with high resolution swath bathymetry data the back projection images show that the azimuth of rupture branches east of the trench axis were controlled by the geometry of bending related faults on the pacific plate and that the rupture branch west of the trench axis may correlate with the along strike fore arc segmentation the rupture along the subduction interface was triggered by the seaward rupture and a partially subducted normal fault may have played a key role in facilitating the triggering the apparent normal reverse faulting interactions pose a higher seismic risk to this region than their individual strands at the northernmost corner of the tonga subduction zone

rapid estimation of rupture directivity application to the 1992 landers ms 7 4 and cape mendocino ms 7 2 california earthquakes using empirical green functions with regional and teleseismic surface waves it is possible to resolve fault finiteness effects in many cases uniquely defining the fault plane for relatively large earthquakes the technique requires very little data processing and can be applied in near real time with the current distribution of seismic stations the landers strike slip earthquake was dominated by two sub events with predominantly north northwestward rupture the second sub event was 1 5 times larger and rotated in strike by 12 counterclockwise relative to the first the cape mendocino thrust event had a relatively smooth rupture that propagated to the southwest on a shallow dipping fault

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

deep learning of aftershock patterns following large earthquakes aftershocks are a response to changes in stress generated by large earthquakes and represent the most common observations of the triggering of earthquakes the maximum magnitude of aftershocks and their temporal decay are well described by empirical laws such as bath s law1 and omori s law2 but explaining and forecasting the spatial distribution of aftershocks is more difficult coulomb failure stress change3 is perhaps the most widely used criterion to explain the spatial distributions of aftershocks4 8 but its applicability has been disputed9 11 here we use a deep learning approach to identify a static stress based criterion that forecasts aftershock locations without prior assumptions about fault orientation we show that a neural network trained on more than 131 000 mainshock aftershock pairs can predict the locations of aftershocks in an independent test dataset of more than 30 000 mainshock aftershock pairs more accurately area under curve of 0 849 than can classic coulomb failure stress change area under curve of 0 583 we find that the learned aftershock pattern is physically interpretable the maximum change in shear stress the von mises yield criterion a scaled version of the second invariant of the deviatoric stress change tensor and the sum of the absolute values of the independent components of the stress change tensor each explain more than 98 per cent of the variance in the neural network prediction this machine learning driven insight provides improved forecasts of aftershock locations and identifies physical quantities that may control earthquake triggering during the most active part of the seismic cycle neural networks trained on data from about 130 000 aftershocks from around 100 large earthquakes improve predictions of the spatial distribution of aftershocks and suggest physical quantities that may control earthquake triggering

redshift of earthquakes via focused blind deconvolution of teleseisms we thank the editor prof huajian yao and reviewers jiuxun yin and anonymous for providing their valuable feedback we thank our colleagues nafi toks oz matt li aurelien mordret tom herring hongjian fang and michael floyd for providing insight and expertise that greatly assisted this research we thank martin mai from king abdullah university of science and technology for his informative commentary of a draft version the material is based upon work assisted by a grant from equinor any opinions findings and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of equinor ld is also supported by afosr grant fa9550 17 1 0316

the mechanism of postseismic deformation triggered by the 2006 2007 great kuril earthquakes received 21 january 2011 accepted 15 february 2011 published 24 march 2011 1 in 2006 2007 a doublet of great earthquakes mw 8 struck in the center of the kuril subduction zone a thrust event followed by an extensional event our observations of the kuril gps array in 2006 2009 outline a broad zone of postseismic deformation with initial horizontal velocities to 90 mm a and postseismic uplift we show that most of the postseismic signal after the great kuril doublet is caused by the viscoelastic relaxation of shear stresses in the weak asthenosphere with the best fitting maxwell viscosity in the range of 5 10 10 17 pa s an order of magnitude smaller than was estimated for several subduction zones we predict that the postseismic deformation will die out in about a decade after the earthquake doublet our results suggest large variations among subduction zones in the asthenospheric viscosity one of the most important rheological parameters citation kogan m g n f vasilenko d i frolov j t freymueller g m steblov b w levin and a s prytkov 2011 the mechanism of postseismic deformation triggered by the 2006 2007 great kuril earthquakes geophys res lett 38 l06304 doi 10 1029 2011gl046855

shear and compressional velocity models of the mantle from cluster analysis of long period waveforms summary we present a new technique for the efficient measurement of the traveltimes of long period body wave phases the technique is based on the fact that all arrivals of a particular seismic phase are remarkably similar in shape for a single event this allows the application of cross correlation techniques that are usually used in a regional context to measure precise global differential times the analysis is enhanced by the inclusion of a clustering algorithm that automatically clusters waveforms by their degree of similarity this allows the algorithm to discriminate against unusual or distorted waveforms and makes for an extremely efficient measurement technique this technique can be applied to any seismic phase that is observed over a reasonably large distance range here we present the results of applying the algorithm to the long period channels of all data archived at the iris dmc from 1976 to 2005 for the seismic phases s and p from 23 to 100 and ss and pp from 50 to 170 the resulting large data sets are inverted along with existing surface wave and updated differential traveltime measurements for new mantle models of s and p velocity the resolution of the new model is enhanced particularly in the mid mantle where ss and pp turn we find that slow anomalies in the central pacific and africa extend from the core mantle boundary to the upper mantle but their direct connection to surface hotspots is beyond our resolution furthermore we find that fast anomalies that are likely associated with subducting slabs disappear between 1700 and 2500 km and thus are not continuous features from the upper to lower mantle despite our extensive coverage and high resolution of the mid mantle

spatially linked asperities of the 2006 2007 great kuril earthquakes revealed by gps 1 in 2006 2007 two great earthquakes ruptured the center of the kuril subduction zone first the interplate thrust event then the intraplate extensional event on the outer rise the affected region was a seismic gap since 1915 published patterns of slip differ for various seismic and tsunami inversions the surface offsets that we measured with gps on the kuril islands are sensitive to the total slip including slow components beyond the seismic and tsunami band we invert coseismic offsets and show that the asperities or regions of high slip are spatially linked for both earthquakes this pattern suggests although does not prove that the first event triggered the second for the 2006 earthquake the asperity is very shallow probably because of the absence of an accretionary prism for the 2007 earthquake our modeling suggests that the rupture occurred in the bent pacific lithosphere to a depth of 50 km

faulting within the pacific plate at the mariana trench implications for plate interface coupling and subduction of hydrous minerals we investigate faulting within the incoming pacific plate at the mariana subduction trench to understand stresses within the bending plate regional stresses acting upon the plate interface and the extent of possible faulting induced mantle serpentinization we determine accurate depths by inverting teleseismic p and sh waveforms for earthquakes occurring during 1990 2011 with global centroid moment tensor gcmt solutions for earthquakes with mw 5 0 we determine centroid depths and source time functions and refine the fault parameters results from central mariana indicate that all earthquakes are extensional and occur at centroid depths down to 11 km below the moho at the southern mariana trench extensional earthquakes continue to 5 km below the moho one compressional earthquake at 34 km below the seafloor suggests stronger plate interface coupling here in addition we model the stress distribution within the pacific plate along two bathymetric profiles extending seaward from the mariana subduction trench axis to better understand whether our earthquake depth solutions match modeled scenarios for plate bending under applied external forces results from our flexure models match the locations of extensional and compressional earthquakes and suggest that the pacific plate at southern mariana is experiencing larger compressional stresses possibly due to greater interplate coupling additionally we conclude that if extensional faulting promotes the infiltration of water into the subducting plate mantle then the top 5 15 km of the pacific plate mantle are partially serpentinized and a higher percentage of serpentinization is located near the central mariana trench where extensional events extend deeper

inelastic models of lithospheric stress 11 implications for outer rise seismicity and dynamics summary outer rise seismicity and dynamics are examined using inelastic models of lithospheric deformation which allow a more realistic characterization of stress distributions and failure behaviour we conclude that thrust and normal faulting outer rise earthquakes represent substantially different states of stress within the oceanic lithosphere specifically the normal faulting events occur in response to downward plate bending which establishes the standard bending dominated state of outer rise stress and the thrust faulting events occur in response to an elevated level of in plane compression which develops only in response to exceptional circumstances this interpretation accounts for the observation that normal faulting outer rise earthquakes occur more frequently and are more widely distributed than their thrust faulting counterparts an observation for which the simple bending model offers no explanation in addition attributing both thrust and normal faulting outer rise earthquakes to plate bending implies that both classes of events should occur within relatively close lateral proximity to one another because both are allegedly a manifestation of the same bendingdominated stress distribution whereas in reality this is not observed we propose that the tendency for thrust faulting outer rise earthquakes to exhibit greater source depths than their normal faulting counterparts an observation that is frequently cited in support of the bending interpretation of the former is merely a consequence of the fact that bending induced tension is confined to the upper lithosphere our model predicts that outer rise in plane force variations may promote thrust faulting outerrise activity prior to an underthrusting interplate subduction earthquake and normalfaulting outer rise activity following such an earthquake but that both forms of outerrise activity are unlikely to be associated with the same subduction earthquake a corollary implication of our model is that subduction earthquakes are likely to be either preceded by or followed by an absence of large outer rise earthquakes levels of in plane compression necessary to generate thrust faulting outer rise earthquakes are attributed to stress concentrations within the subducting plate that are induced by relatively localized resistance to regionally distributed plate driving forces resistance of this nature may result from either the attempted subduction of relatively buoyant i e isostatically compensated bathymetric features or the existence of strong interplate

tip jets and barrier winds a quikscat climatology of high wind speed events around greenland the high topography of greenland results in a number of orographically induced high wind speed flows along its coast that are of interest from both a severe weather and climate perspective here the surface wind field dataset from the nasa jpl seawinds scatterometer on board the quick scatterometer quikscat satellite is used to develop a wintertime climatology of these flows the high spatial resolution and the twice daily sampling of the seawinds instrument allows for a much more detailed view of the surface winds around greenland than has been previously possible three phenomena stand out as the most distinctive features of the surface wind field during the winter months the previously identified tip jets and reverse tip jets as well as the hitherto unrecognized barrier flows along its southeast coast in the vicinity of the denmark strait peak surface wind speeds associated with these phenomena can be as large as 50 m s 1 with winds over 25 m s 1 occurring approximately 10 15 of the time at each location a compositing technique is used to show that each type of flow is the result of an interaction between a synoptic scale parent cyclone and the high topography of greenland in keeping with previous work it is argued that tip jets are caused by a combination of conservation of the bernoulli function during orographic descent and acceleration due to flow splitting as stable air passes around cape farewell while barrier winds are a geostrophic response to stable air being forced against high topography it is proposed that reverse tip jets occur when barrier winds reach the end of the topographic barrier and move from a geostrophic to a gradient wind balance becoming supergeostrophic as a result of their anticyclonic curvature

independent active microplate tectonics of northeast asia from gps velocities and block modeling 1 independent okhotsk and amurian microplate motions are tested using velocities from 123 gps sites 80 from within the proposed okh and amu plate boundaries used to constrain the plate kinematics of northeast asia a block modeling approach is used to incorporate both rigid block rotation and near boundary elastic strain accumulation effects in a formal inversion of the gps velocities models include scenarios with and without independent okh and amu plate motion our modeling favors scenarios with independent okh and amu motion based on the application of f test statistics the independent okh plate rotates 0 231 deg myr clockwise with respect to north america about a pole located north of sakhalin the modeled amu plate rotates 0 298 deg myr counterclockwise with respect to nam about a pole located west of the magadan region the plate motion parameters of the independent plates are consistent with the kinematics inferred from earthquake focal mechanism solutions along their boundaries

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

coseismic slip distribution for the mw 9 2011 tohoku oki earthquake derived from 3 d fe modeling 1 the coseismic slip distribution of the mw 9 0 2011 tohoku oki earthquake has been estimated by inverting near field onshore and offshore geodetic data using green s function calculated with a 3 d finite element fe model the fe model simulates several geophysical features of the subduction zone that hosted the rupture surface of the event these features include a 3 d geometric configuration and distribution of material properties of the tectonic system a precise geometric configuration of the irregular rupture surface and an irregular free surface according to the topography and bathymetry a model that simulates rupture along the interface between the relatively weak overriding okhotsk plate and stiff subducting slab of the pacific plate requires less slip to produce the observed surface deformation compared to a model having uniform material properties across the rupture interface furthermore the estimated slip of the heterogeneous model is more widely distributed over the shallow portion of the plate boundary whereas the estimated slip of the homogeneous model is more focused updip of the epicenter this demonstrates the sensitivity of inverse analyses of geodetic data for the 2011 tohoku oki earthquake to the simulated domain geometry and configuration of material properties

comparative study of two tsunamigenic earthquakes in the solomon islands 2015 mw 7 0 normal fault and 2013 santa cruz mw 8 0 megathrust earthquakes the july 2015 mw 7 0 solomon islands tsunamigenic earthquake occurred 40 km north of the february 2013 mw 8 0 santa cruz earthquake the proximity of the two epicenters provided unique opportunities for a comparative study of their source mechanisms and tsunami generation the 2013 earthquake was an interplate event having a thrust focal mechanism at a depth of 30 km while the 2015 event was a normal fault earthquake occurring at a shallow depth of 10 km in the overriding pacific plate a combined use of tsunami and teleseismic data from the 2015 event revealed the north dipping fault plane and a rupture velocity of 3 6 km s stress transfer analysis revealed that the 2015 earthquake occurred in a region with increased coulomb stress following the 2013 earthquake spectral deconvolution assuming the 2015 tsunami as empirical green s function indicated the source periods of the 2013 santa cruz tsunami as 10 and 22 min

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

the december 7 2012 japan trench intraplate doublet mw 7 2 7 1 and interactions between near trench intraplate thrust and normal faulting a pair of large earthquakes ruptured within the pacific plate below the japan trench about 14 s apart on december 7 2012 the doublet began with an m w 7 2 thrust event 50 70 km deep followed by an m w 7 1 7 2 normal faulting event in the range 10 30 km deep about 27 km to the south southwest the deep lithosphere thrust earthquake is the largest such event to be recorded seaward of the rupture zone of the great march 11 2011 tohoku m w 9 0 earthquake it follows an extensive intraplate normal faulting aftershock sequence since 2011 extending up to 100 km east of the trench many small normal faulting aftershocks of the doublet occurred along a 60 km long trench parallel trend beneath the inner trench slope the complex overlapping signals produced by the doublet present challenges for routine long period moment tensor inversion procedures but the inadequacy of any single point source inversion was readily evident from comparisons of different data sets and solutions using different frequency bands we use a two double couple inversion of w phase signals to quantify the doublet characteristics along with an iterative deconvolution of p wave signals that extracts a compatible three sub event sequence the occurrence of a large deep compressional event near the trench several years subsequent to a great megathrust event is similar to a sequence that occurred in the central kuril islands between 2006 and 2009 and appears to be associated with stress changes caused by the preceding interplate thrusting and intraplate normal faulting recent large deep compressional events in the philippine trench and northern kermadec trench regions may be influenced by strain accumulation on adjacent locked interplate megathrusts regions having more pronounced curvature of the subducting plate may have unrelaxed bending stresses facilitating occurrence of large deep thrust faulting in advance of future megathrust failures as was observed in 1963 in the central kuril islands region but not in the gently curving pacific plate offshore of the great tohoku event

an overview of barrier winds off southeastern greenland during the greenland flow distortion experiment during the greenland flow distortion experiment barrier flow was observed by an instrumented aircraft on 1 2 5 and 6 march 2007 off southeastern greenland during this time period the barrier flow increased from a narrow jet 15 m s 1 to a jet filling almost the whole of the denmark strait with maximum wind speed exceeding 40 m s 1 dropsonde observations show that the barrier flow was capped by a sharp temperature inversion below mountain height below the inversion was a cold and dry jet with a larger northerly wind component than that of the flow above which was also warmer and more moist thus the observations indicate two air masses below mountain height a cold and dry barrier jet of northern origin and above this a warmer and moister air mass that was of cyclonic origin numerical simulations emphasize the non stationarity of the greenland barrier flow and its dependence on the synoptic situation in the greenland iceland region they show that the barrier jet originated north of the denmark strait and was drawn southward by a synoptic scale cyclone with the strength and location of the maximum winds highly dependent on the location of the cyclone relative to the orography of greenland experiments without greenland s orography suggest a 20 m s 1 enhancement of the low level peak wind speeds due to the presence of the barrier thus the greenland barrier flows are not classic geostrophically balanced barrier flows but have a significant ageostrophic component and are precisely controlled by synoptic scale systems copyright c 2009 royal meteorological society

impact of surface characteristics on flow over a mesoscale mountain dynamical downscaling of atmospheric flow over iceland has revealed that prominent downslope accelerated flows are not merely extreme events but rather constitute a strong climatological signal over the larger ice caps ice caps are characterised by smooth and cold surfaces and both of these properties have previously been found to enhance downslope flows in this article we investigate the response of downslope accelerated flow over hofsjokull in central iceland to an increase in surface roughness and a change in surface temperature corresponding to the effect of melting hofsjokull s ice cap we do so by exploring the flow over hofsjokull for a summertime case by means of several numerical sensitivity experiments in the experiments we find a stronger downslope flow acceleration with than without the ice cap while an increased surface roughness distinctly dampens the downslope flow the effect of changing the surface temperature is minimal this study is both of general relevance through its exploration of factors affecting downslope acceleration of stably stratified flow and also of interest because glaciers diminish rapidly in a changing climate

a reassessment of outer rise seismicity and its implications for the mechanics of oceanic lithosphere we use body waveform modelling to constrain the source parameters of earthquakes occurring globally in oceanic lithosphere beneath the subduction zone outer rise and outer trench slope these data are then used to map the stress state in the lithosphere of the downgoing plate as it bends into the subduction zone our results provide new constraints on the faulting of oceanic lithosphere at the outer rise which is important for understanding the transmission of plate driving forces through the subduction system in all cases shallow normal faulting earthquakes are observed at the top of the plate and are separated in depth from any deeper thrust faulting earthquakes no temporal variation associated with large thrust faulting earthquakes on the subduction interface is seen in the depth extent of each type of faulting at the outer rise the transition depth from trench normal extension to compression is found to vary in agreement with models in which deformation is driven by the combination of in plane stresses and bending stresses resulting principally from slab pull combining the seismologically derived constraints on the thickness of the elastic core of the plate with estimates of the plate curvature we place upper bounds on the strength of the lithosphere at the outer rise which is required to be 300 mpa for a constant yield stress model or governed by an effective coefficient of friction of 0 3

large trench parallel gravity variations predict seismogenic behavior in subduction zones we demonstrate that great earthquakes occur predominantly in regions with a strongly negative trench parallel gravity anomaly tpga whereas regions with strongly positive tpga are relatively aseismic these observations suggest that over time scales up to at least 1 million years spatial variations of seismogenic behavior within a given subduction zone are stationary and linked to the geological structure of the fore arc the correlations we observe are consistent with a model in which spatial variations in frictional properties on the plate interface control trench parellel variations in fore arc topography gravity and seismogenic behavior

rupture details of the 28 march 2005 sumatra mw 8 6 earthquake imaged with teleseismic p waves 1 we image the rupture of the 28 march 2005 sumatra mw 8 6 earthquake by back projecting teleseismic p waves recorded by the global seismic network and the japanese hi net to their source the back projected energy suggests that the rupture started slowly had a total duration of about 120 s and propagated at 2 9 to 3 3 km s from the hypocenter in two different directions first toward the north for 100 km and then after a 40 s delay toward the southeast for 200 km our images are consistent with a rupture area of 40 000 km2 the locations of the first day of aftershocks and the harvard cmt mw of 8 6 which implies an average slip of 6 m the earthquake is similar in its location size and geometry to a mw 8 5 event in 1861 our estimated average slip is consistent with a partially coupled subduction interface gps forearc velocities and the 59 mm yr convergence rate if the 2005 earthquake released elastic strain that accumulated over many hundreds of years rather than just since the last 1861 event

the p wave upper mantle structure beneath an active spreading centre the gulf of california summary detailed analysis of short period travel time dt d and wave form data reveals the upper mantle structure beneath an oceanic ridge to depths of 900 km more than 1400 digital seismograms from earthquakes in mexico and central america recorded at scarlet yield 1753 travel times and 58 direct measurements of dt d as well as high quality stable waveforms the 29 events combine to form a continuous record section from 9 to 40 with an average station spacing of less than 5 km first the travel times are inverted using the tau method of bessonova et al the resultant model is adjusted to agree with the experimental p values further constraints arise from the observed relative amplitudes of mantle phases which are modelled by trial and error using wkbj synthetic seismograms chapman wiggins model gca which is appropriate for western mexico north of 20 latitude is similar to existing upper mantle models for shield tectonic continental and arc trench regimes below 400 km but differs significantly in the upper 350 km gca velocities are very low in this depth range the model catches up with the others with a very large velocity gradient from 225 to 390 km this well resolved feature is consistent with the shear wave model tna for western north america of grand helmberger the abundant data from 20 to 30 control the detailed shape of the 660 km discontinuity very large velocity gradients lie both above 620 660 km and below 661 680km a 2 8 per cent velocity change

the dynamics of orographic wake formation in flows with upstream blocking the development of orographic wakes and vortices is revisited from the dynamical perspective of a three dimensional 3d vorticity vector potential formulation particular emphasis is given to the role of upstream blocking in the formation of the wake scaling arguments are first presented to explore the limiting form of the 3d vorticity inversion for the case of flow at small dynamical aspect ratio it is shown that in the limit of small the inversion is determined completely by the two horizontal vorticity components that is the part of the velocity induced by the vertical component of vorticity vanishes in the small limit this result leads to an approximate formulation of small fluid mechanics in which the three governing prognostic variables are the two horizontal vorticity components and the potential temperature the remainder of the study then revisits the problem of orographic wake formation from the perspective of this small vorticity dynamics framework previous studies have suggested that one of the potential routes to stratified wake formation is through the blocking of flow on the upstream side of the barrier this apparent link between blocking and wake formation is shown to be relatively straightforward in the small vorticity context in particular it is shown that blocking of the flow inevitably leads to a horizontal vorticity distribution that favors deceleration of the leeside flow at the ground this process of leeside flow deceleration as well as the subsequent time evolution of the wake is illustrated through a series of numerical initial value problems involving flows past 2d and 3d barriers it is proposed that the initiation of the wake flow in these stratified problems resembles the flow produced by a retracting piston in shallow water theory

twenty five years of progress in the science of geological tsunamis following the 1992 nicaragua and flores events we review a set of 47 tsunamis of geological origin triggered by earthquakes landslides or volcanoes which have occurred over the past 25 years and provided significant new insight into theoretical experimental field or societal aspects of tsunami science among the principal developments in our command of various aspects of tsunamis we earmark the development of the w phase inversion for the low frequency moment tensor of the parent earthquake the abandonment of the concept of a maximum earthquake magnitude for a given subduction zone controlled by simple plate properties the development and implementation of computer codes simulating the interaction of tsunamis with initially dry land at beaches thus introducing a quantitative component to realistic tsunami warning procedures and the recent in situ investigation of current velocities in addition to the field of surface displacements during the interaction of tsunamis with harbors continued research remains warranted notably in the field of the real time identification of tsunami earthquakes whose tsunamis are larger than expected from their seismic magnitudes especially conventional ones the recent tragedy during the 2018 krakatau flank collapse along a scenario which had been quantitatively forecast also emphasizes the need for a continued effort in the education of the populations at risk

gravity anomalies crustal structure and seismicity at subduction zones 2 interrelationships between fore arc structure and seismogenic behavior an ensemble averaging technique is used to remove the long wavelength topography and gravity field associated with subduction zones short wavelength residual anomalies are attributed to the tectonic structure of subducting and overthrusting plates a paired positive negative fore arc anomaly is observed consisting of a long 1000 km linear trench parallel ridge landward of the deep sea terrace basin ridges have amplitudes of 1500 3000 m and 160 240 mgal wavelengths of 150 200 km and high gravity anomaly to topography ratios 50 75 mgal km 1 the ridge crests correlate with the downdip limit of coseismic slip and strong interplate coupling and in cascadia the updip limit of tremor epicenters the ridge crest may be interpreted as defining the boundary between the velocity weakening and seismogenic region of the subduction interface and the downdip frictional transition zone in tonga kermadec the kuril islands and chile landward ridges are associated with extinct volcanic arcs paired anomalies are attributed to the preferential subduction erosion of the outer fore arc and a spatially varying combination of a lower crustal underplating beneath the inner fore arc b the transformation of interseismic strain into permanent geologic strain via faulting folding or buckling of the inner fore arc and c the relative trenchward migration of extinct volcanic arcs in regions operating with a net crustal deficit along strike transitions in fore arc morphology and seismogenic behavior are related to preexisting crustal structure of subducting and overthrusting plates fore arcs have the added potential of recording the time integrated response of the upper plate to subduction processes and fore arc structure should be considered in tandem with seismological observations

broadband source modeling of the november 8 1997 tibet mw 7 5 earthquake and its tectonic implications we studied the source process of a large ms 7 9 intraplate earthquake that occurred on november 8 1997 at 1002 ut in a remote region of northern tibet we used four distinct methods to investigate the broadband source process and thereby better understand the tectonic implications of this event we relocated aftershocks using a master event technique and found that the distribution of aftershocks covers a region of 200 km in lateral extent we also employed a surface wave spectral inversion technique to estimate the mainshock moment depth centroid location and centroid time and utilized an empirical green s function technique to extract rupture directivity information and a detailed source time function from observed seismograms we also inverted body waves to estimate the moment release along the fault and the source time function the 1997 earthquake ruptured a strike slip fault that appears to be an extension or splay of the kun lun fault system this fault is one of the most seismically active strike slip faults within the tibetan plateau and has had events with surface wave magnitudes of 6 1 7 4 and 7 9 in this region since 1973 the rupture released most of the energy within the first 20 s and propagated bilaterally initially with the later rupture propagating westward for 20 30 s the absence of large aftershocks suggests that the earthquake efficiently released the stored strain comparing mainshock to the largest aftershock energy ratios for this event and other large strike slip events shows that faulting within the plateau has the characteristics of weak faults e g fracture zone faulting

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

rapid estimation of first order rupture characteristics for large earthquakes using surface waves 2004 sumatra andaman earthquake 1 broadband surface waves from large earthquakes can be rapidly processed to estimate seismic moment faulting duration and general slip distribution supplying important information for hazard response efforts including tsunami warnings deconvolution of surface wave green s functions removes propagation effects yielding azimuthally varying effective source time functions even a single faultperpendicular time function can provide robust first order estimates of the temporal history of seismic radiation and associated slip distribution simplified two dimensional finite fault modeling using a few surface wave time functions can reliably characterize the smooth component of the overall rupture process these procedures are demonstrated using 13 rayleigh wave observations for the 26 december 2004 sumatra andaman earthquake yielding satisfactory agreement with models based on more complete seismic data sets depending on source and station locations stable slip estimates can be obtained within 15 60 minutes of the onset of a large earthquake citation ammon c j a a velasco and t lay 2006 rapid estimation of first order rupture characteristics for large earthquakes using surface waves 2004 sumatra andaman earthquake geophys res lett 33 l14314 doi 10 1029 2006gl026303

imaging the 2016 mw 7 8 kaikoura new zealand earthquake with teleseismic p waves a cascading rupture across multiple faults the 13 november 2016 mw 7 8 kaikoura new zealand earthquake was investigated using teleseismic p waves backprojection of high frequency p waves from two regional arrays shows unilateral rupture of at least two southwest northeast striking faults with an average rupture speed of 1 4 1 6 km s and total duration of 100 s guided by these backprojection results 33 globally distributed low frequency p waves were inverted for a finite fault model ffm of slip the ffm showed evidence of several subevents however it lacked significant moment release near the epicenter where a large burst of high frequency energy was observed a local strong motion network recorded strong shaking near the epicenter hence for this earthquake the distribution of backprojection energy is superior to the ffm as a guide of strong shaking for future large earthquakes that occur in regions without strong motion networks initial shaking estimates could benefit from backprojection constraints

inelastic models of lithospheric stress i theory and application to outer rise plate deformation summary outer rise stress distributions determined in the manner that mechanical engineers evaluate inelastic stress distributions within conventional materials are contrasted with those predicted using simple elastic plate models that are frequently encountered in studies of outer rise seismicity this comparison indicates that the latter are inherently inappropriate for studies of intraplate earthquakes which are a direct manifestation of lithospheric inelasticity we demonstrate that the common practice of truncating elastically superimposed stress profiles so that they are not permitted to exceed laboratory based estimates of lithospheric yield strength will result in an accurate characterization of lithospheric stress only under relatively restrictive circumstances in contrast to elastic plate models which predict that lithospheric stress distributions depend exclusively upon the current load inelastic plate models predict that stress distributions are also significantly influenced by the plate loading history and in many cases this influence is the dominant factor in determining the style of potential seismicity e g thrust versus normal faulting numerous intuitive interpretations of outer rise earthquakes have been founded upon the implicit assumption that a unique relationship exists between a specified combination of plate curvature and in plane force and the resulting lithospheric stress distribution we demonstrate that the profound influence of deformation history often invalidates such interpretations finally we examine the reliability of yield envelope representations of lithospheric strength that are constructed on the basis of empirically determined frictional sliding relationships and silicate plastic flow laws although representations of this nature underestimate the strength of some major interplate faults such as the san andreas they appear to represent a reliable characterization of the strength of intraplate oceanic lithosphere

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

teleseismic p wave imaging of the 26 december 2004 sumatra andaman and 28 march 2005 sumatra earthquake ruptures using the hi net array 1 seismograms from a dense high quality seismic network in japan are used to investigate the characteristics of the 26 december 2004 sumatra andaman and the 28 march 2005 sumatran earthquakes the onset of the p waveforms are aligned through cross correlation and a simple concept of back projecting seismic energy to a grid of potential source locations is applied the waveform alignment removes the effects due to lateral variations in wave speed between the hypocenter and each station to better approximate the effects of three dimensional heterogeneity for paths originating from grid points away from the hypocenter cross correlation results of the p waveforms from aftershocks are introduced this additional information leads to improved resolution of smaller scale features near many of the aftershocks by reducing wavefront distortion the back projection analysis provides a quick assessment of the spatiotemporal extent and variability of relative high frequency energy release which can be translated into an estimate of the moment magnitude as well as an unparalleled view of high frequency rupture propagation the results are in general consistent with those obtained from more involved source inversion methods the 2004 sumatra andaman earthquake released most energy in a region northwest of the sumatra island and the rupture extended to the northern andaman islands about 1300 km from the epicenter this northern portion of the rupture radiated a considerable amount of energy but there is little evidence of slow slip the 2005 event is imaged to have bilateral rupture with northwestern slip occurring for about 50 s before it moved to the southeast of the epicenter

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

worldwide doublets of large shallow earthquakes abstract we investigated all the pairs of mw 7 5 shallow earthquakes in the harvard catalog that occurred at a centroid distance of less than 100 km we showed that most of these pairs have similar focal mechanisms because these earthquakes generally should have focal regions in excess of 100 km diameter their rupture zones apparently intersect for all these pairs the time interval is significantly less than the time span needed for plate motion to accumulate the strain released by the first event these observations conflict strongly with quasi periodic recurrence models on which the seismic gap hypothesis is based power law recurrence fits these earthquake ob servations much better introduction many models used to forecast long term seismic hazard are based on the quasi periodic or seismic cycle hypothesis of large earthquake occurrence this hypothesis assumes that the probability of a large earthquake is low after signifi cant release of seismic energy and that danger increases only when tectonic plate motion accumulates strain sufficient for a new strong event several models have been formulated to apply this idea to long term earthquake prediction mccann

along strike variability of rupture duration in subduction zone earthquakes 1 subduction zone earthquakes exhibit a wide spectrum of rupture times that reflect conditions on the megathrust fault tsunami earthquakes are examples of slower than expected ruptures that produce anomalously large tsunamis relative to the surface wave magnitude one model explaining tsunami earthquakes suggests slip within patches of low rigidity material at shallow depths heterogeneous fault conditions such as having patches of low rigidity material surrounded by higher strength material should produce heterogeneous earthquake rupture parameters here we investigate along strike variation in rupture duration for 427 shallow thrust earthquakes mw 5 0 7 0 in the peru chile alaska tonga kuril izu and java sumatra subduction zones to explore how heterogeneous seismic and tectonic characteristics such as differences in sediment type thickness and roughness of subducting bathymetry affect earthquake properties earthquake source parameters including rupture durations are estimated using multi station deconvolution of teleseismic p and sh waves to solve for earthquake source time functions and all events are relocated using additional depth phase information we classify events into shallow 26 km and deep 26 km and 61 km groups based on the overall mean depth and focus on the longest duration events with moment normalized rupture durations of 1 standard deviation above the mean duration for each group we find long duration events at all depths within the study regions except peru and chile we find no correlation with incoming sediment thickness or type and limited spatial correlation with regions of past tsunami earthquakes regions of observed afterslip and subducting bathymetric features

cyclic stressing and seismicity at strongly coupled subduction zones we use the finite element method to analyze stress variations in and near a strongly coupled subduction zone during an earthquake cycle deformation is assumed to be uniform along strike plane strain on a cross section normal to the trench axis and periodic earthquake slip is imposed consistent with the long term rate of plate convergence and degree of coupling simulations of stress and displacement rate fields represent periodic fluctuations in time superimposed on an average field the oceanic plate descending slab and continental lithosphere are assumed here to respond elastically to these fluctuations and the remaining mantle under and between plates is assumed to respond as maxwell viscoelastic in the first part of the analysis we find that computed stress fluctuations in space and time are generally consistent with observed earthquake mechanism variations with time since a great thrust event in particular trench normal extensional earthquakes tend to occur early in the earthquake cycle toward the outer rise but occur more abundantly late in the cycle in the subducting slab downdip of the main thrust zone compressional earthquakes when they occur at all have the opposite pattern our results suggest also that the actual timing of extensional outer rise events is controlled by the rheology of the shallow aseismic portion of the thrust interface the second part of the analysis shows the effects of mantle relaxation on the rate of ground surface deformation during the earthquake cycle models without relaxation predict a strong overall compressional strain rate in the continental plate above the main thrust zone with the strain rate constant between mainshocks however with significant relaxation present a localized region of unusually low compressional or even slightly extensional strain rate develops along the surface of the continental plate above and somewhat inland from the downdip edge of the locked main thrust zone the low strain rate starts in the middle or late part of the cycle depending on position this result suggests that the negligible or small contraction measured on the shumagin islands alaska during 1980 to 1991 may not invalidate an interpretation of that region as being a moderately coupled subduction zone in contrast mantle relaxation causes only modest temporal nonuniformity of uplift rates in the overriding plate and of extensional stress rates in the subducting plate even when the maxwell time is an order of magnitude less than the recurrence interval

the 17 july 2006 java tsunami earthquake the 17 july 2006 java earthquake involved thrust faulting in the java trench and excited a deadly tsunami 5 8 m that inundated the southern coast of java the earthquake s size estimates vary significantly with seismic wave period very long period signals 300 500 s indicate a seismic moment of 6 7 10 20 nm m w 7 8 m s 20 s 7 2 m b 1 s 6 2 while shaking intensities 3 10 hz were mmiv the large tsunami relative to ms characterizes this event as a tsunami earthquake like previous tsunami earthquakes the java event had an unusually low rupture speed of 1 0 1 5 km s and occurred near the up dip edge of the subduction zone thrust fault most large aftershocks involved normal faulting the rupture propagated 200 km along the trench with several pulses of shorter period seismic radiation superimposed on a smooth background rupture with an overall duration of 185 s

mixing basaltic and dacitic magmas by forced convection although magma mixing is an old concept which has been applied to many magma types recent petrographic studies have revived interest in the theory by suggesting that it may account for the origin of calk alkaline magma1 6 and mid ocean ridge basalt7 9 there has been no previous experimental investigation into how two magmas with different properties can mix to form a homogeneous magma of andesitic composition or to produce textures such as observed in banded dacite we present here the results of experiments demonstrating that basaltic and dacitic magmas can be easily mixed by forced convection to form both banded dacite and homogeneous andesite in less than a few hours

tracking the rupture of the mw 9 3 sumatra earthquake over 1 150 km at teleseismic distance on 26 december 2004 a moment magnitude mw 9 3 earthquake occurred along northern sumatra the nicobar and andaman islands resulting in a devastating tsunami in the indian ocean region the rapid and accurate estimation of the rupture length and direction of such tsunami generating earthquakes is crucial for constraining both tsunami wave height models as well as the seismic moment of the events compressional seismic waves generated at the hypocentre of the sumatra earthquake arrived after about 12 min at the broadband seismic stations of the german regional seismic network grsn located approximately 9 000 km from the event here we present a modification of a standard array seismological approach and show that it is possible to track the propagating rupture front of the sumatra earthquake over a total rupture length of 1 150 km we estimate the average rupture speed to be 2 3 2 7 km s 1 and the total duration of rupture to be at least 430 s and probably between 480 and 500 s

rupture imaging of the mw 7 9 12 may 2008 wenchuan earthquake from back projection of teleseismic p waves 1 the mw 7 9 wenchuan earthquake of 12 may 2008 was the most destructive chinese earthquake since the 1976 tangshan event tens of thousands of people were killed hundreds of thousands were injured and millions were left homeless here we infer the detailed rupture process of the wenchuan earthquake by back projecting teleseismic p energy from several arrays of seismometers this technique has only recently become feasible and is potentially faster than traditional finite fault inversion of teleseismic body waves therefore it may reduce the notification time to emergency response agencies using the iris dmc we collected 255 vertical component broadband p waves at 30 95 from the epicenter we found that at periods of 5 s and greater nearly all of these p waves were coherent enough to be used in a global array we applied a simple down sampling heuristic to define a global subarray of 70 stations that reduced the asymmetry and sidelobes of the array response function arf we also considered three regional subarrays of seismometers in alaska australia and europe that had apertures less than 30 and p waves that were coherent to periods as short as 1 s individual arfs for these subarrays were skewed toward the subarrays however the linear sum of the regional subarray beams at 1 s produced a symmetric arf similar to that of the groomed global subarray at 5 s for both configurations we obtained the same rupture direction rupture length and rupture time we found that the wenchuan earthquake had three distinct pulses of high beam power at 0 23 and 57 s after the origin time with the pulse at 23 s being highest and that it ruptured unilaterally to the northeast for about 300 km and 110 s with an average speed of 2 8 km s it is possible that similar results can be determined for future large dip slip earthquakes within 20 30 min of the origin time using relatively sparse global networks of seismometers such as those the usgs uses to locate earthquakes in near real time

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

empirical green function deconvolution of broadband surface waves rupture directivity of the 1992 landers california mw 7 3 earthquake we present a simple method to determine gross temporal and spatial characteristics of faulting that can uniquely define the fault plane for a relatively large earthquake the technique involves deconvolution of teleseismic and regional broadband surface waves and or body waves of a small event an empirical green function from the corresponding signals at the same stations for a large mainshock this deconvolution corrects each mainshock seismic record for propagation and instrument response and if the focal mechanisms and centroid depths are identical deconvolution provides relative source time functions for the mainshock azimuthal variations of source time function width or subevent interference reveal the mainshock rupture directivity changes in the source mechanism during rupture can be evaluated for some classes of events our empirical green function procedure is novel in its application to surface waves and its use for large m 7 earthquakes we perform synthetic tests to establish intrinsic limitations of the method the procedure requires very little data processing and can be applied in near real time with the current distribution of seismic stations that have dial up data retrieval capability it also provides a straightforward procedure for reducing bias in source duration estimates resulting from aspherical heterogeneity and for detecting anomalous long period radiation we apply the procedure to the 28 june 1992 landers california mw 7 3 earthquake the landers earthquake source duration lasted about 25 sec and was dominated by two subevents with predominantly north northwestward rupture extending 60 to 70 km the subevents show counter clockwise rotations of at least 12 in strike that correlate well with mapped surface rupture

paleotsunamis from the central kuril islands segment of the japan kuril kamchatka subduction zone abstract paleotsunami records from the central kuril island segment of the japan kuril kamchatka subduction zone indicate that the region has been frequently inundated by tsunamis as many as 20 22 tsunami deposits are recognized on matua island for the past 3300 yr with an average tsunami recurrence interval of 150 yr and 34 36 tsunami deposits are evident on simushir island for the past 2350 yr with an average recurrence of 65 yr these intervals are short but comparable to other segments of the japan kuril kamchatka subduction zone results from all survey locations reveal shortening recurrence intervals toward the present especially for the last 600 yr indicating a possible preservation bias on simushir tsunamis at least 11 m higher than the modern tsunamis in 2006 and 2007 occurred every 300 yr on average on matua tsunamis with slightly farther inundation than the 2006 and 2007 tsunamis occurred every 215 yr while those with at least 100 m farther inland inundation occur every 750 yr our paleotsunami record almost certainly includes tsunamis that are not from great subduction zone earthquakes in the central kuril segment we expect the matua record includes volcanic tsunamis and the simushir record includes tsunamis from the southern kuril segment

the wake south of the alps dynamics and structure of the lee side flow and secondary potential vorticity banners the dynamics and structure of the lee side flow over the po valley during a northerly fohn event which occurred in the framework of the mesoscale alpine programme special observation period on 8 november 1999 during intensive observation period 15 has been investigated using aircraft data and high resolution numerical simulations numerical simulations were performed with the mesoscale non hydrostatic model meso nh using three nested domains with horizontal resolutions 32 8 and 2 km the 2 km resolution domain being centred on the po valley the basic data model comparison and back trajectory and tracer release analyses provided evidence that the jet wake structure of the flow above the po valley could be reasonably identified with the mountain pass peak distributions measurements from three aircraft flying below the alps crestline at 2700 1500 and 600 m above sea level along two 350 km east west legs designed to be approximately perpendicular to the northerly synoptic flow were used to compute the potential vorticity pv experimentally assuming the lee side flow to be two dimensional the simplified form of the pv under these assumptions is hereafter referred to as spv due to increasing lee side flow curvature with decreasing altitude caused by flow splitting at the scale of the alps the experimentally derived spv was compared to its simulated counterpart in situ measurements showed that coherent secondary pv banners pvb2s do exist downstream of the complex alpine terrain as observations show oscillations between positive and negative values of spv as expected from the simulations the details of the structure of the spv field simulated with meso nh were found to be different from the observations i e the location of observed maxima and minima of spv did not match their simulated counterparts at particular points this is because the correspondence between observed and modelled velocity and potential temperature fields was not good enough to expect good correspondence between differentiated quantities such as vorticity and potential temperature gradient since less reliable shorter scale features are thereby accentuated parametrized processes such as surface drag and internal diffusion and numerical processes such as model filters to which pv production mechanisms are sensitive and whose role is difficult to assess also contribute to the poor agreement between observed and modelled spv fluctuations finally simulations suggest that lowlevel gravity wave breaking was the main mechanism responsible for the formation of the elongated pvb2 modelled observed over the po valley

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

kuril islands arc two seismic cycles of great earthquakes during which the complete history of seismicity ms 6 is observed two adjacent segments of pacific eurasia plate boundary along the kuril islands arc were broken during two great shallow thrust earthquakes that occurred in 1963 moment magnitude m w 8 5 and 1969 m w 8 2 respectively in 1994 a great shock m w 8 3 rebroke the 200 km long plate boundary segment previously broken by the 1969 event and a series of shocks in 1991 m w 7 6 1995 m w 7 9 and 1996 m w 7 2 rebroke major portions of the 300 km long segment previously ruptured by the 1963 event due to the heterogeneities and incompleteness of the instrumental seismicity catalog for shallow focal depth h m s 6 particularly for the first half of the century this is one of the first times that a complete history of instrumental seismicity at an energy level as low as m s 6 occurring in a focal region of great earthquakes during a full seismic cycle has been observed my findings indicate that significant activity at the m s 6 and m s 7 levels took place both within and as well as along the downdip edges of the forthcoming 19909s ruptures during most of the seismic cycle whereas the adjacent regions of the plate boundary were relatively less active the average displacements and repeat times 28 5 yr 3 5 observed for these great earthquakes along this section of the plate boundary as a whole are consistent with the strain energy accumulated during that time by subduction of the pacific plate under the eurasian plate at a rate of 10 cm yr

asperity distribution of the 1952 great kamchatka earthquake and its relation to future earthquake potential in kamchatka the 1952 kamchatka earthquake is among the largest earthquakes of this century with an estimated magnitude of m w 9 0 we inverted tide gauge records from japan north america the aleutians and hawaii for the asperity distribution the results show two areas of high slip the average slip is over 3 m giving a seismic moment estimate of 155 x 102onm or m w 8 8 the 20th century seismicity of the 1952 rupture zone shows a strong correlation to the asperity distribution which suggests that the large earthquakes m 7 are controlled by the locations of the asperities and that future large earthquakes will also recur in the asperity regions

the 2017 mw 8 2 chiapas mexico earthquake energetic slab detachment on 8 september 2017 a great m w 8 2 normal faulting earthquake ruptured within the subducting cocos plate 70 km landward from the middle american trench beneath the tehuantepec gap iterative inversion and modeling of teleseismic and tsunami data and prediction of gps displacements indicate that the steeply dipping rupture extended 180 km to the northwest along strike toward the oaxaca coast and from 30 to 70 km in depth with peak slip of 13 m the rupture likely broke through the entire lithosphere of the young subducted slab in response to downdip slab pull the plate boundary region between the trench and the fault intersection with the megathrust appears to be frictionally coupled influencing location of the detachment comparisons of the broadband body wave magnitude m b and moment scaled radiated energy e r m 0 establish that intraslab earthquakes tend to be more energetic than interplate events accounting for strong ground shaking observed for the 2017 event

new images of the earth s upper mantle from measurements of surface wave phase velocity anomalies 1 the sensitivity of a surface wave to the lateral structure of the earth s mantle depends on the local structure and thickness of the crust particularly at short periods the strong lateral heterogeneity of the crust has a significant nonlinear effect on the surface wave sensitivity functions thus far this effect has not been quantified and tomographic studies of the upper mantle based on surface wave observations have not taken it into account on the basis of a jeffreys wentzel kramers brillouin jwkb description of surface wave propagation we find and discuss the lateral variations of the sensitivity of love and rayleigh waves to mantle seismic anomalies associated with a realistic model of the crust mooney et al 1998 we then use the resulting laterally varying sensitivity kernels to determine a new tomographic image of horizontally and vertically polarized shear velocity in the upper mantle from love and rayleigh wave phase velocity measurements periods from 35 to 300 s in terms of large scale patterns of high and low velocity our model is similar to previously published ones confirming among other features the anomalous anisotropy underlying the central pacific ekstrom and dziewonski 1998 we find however that the lateral dependence of the surface wave sensitivity kernels has a significant effect on the absolute amplitude of the anomalies which should not be neglected as we attempt to obtain higher resolution images of the upper mantle