sentinel 1 observation of the 2017 sangsefid earthquake northeastern iran rupture of a blind reserve slip fault near the eastern kopeh dagh abstract new satellites are now revealing insar based surface deformation within a week after natural hazard events quick hazard responses will be more publically accessible and provide information to responding agencies here we used sentinel 1 interferometric synthetic aperture radar insar data to investigate coseismic deformation associated with the 2017 sangsefid earthquake which occurred in the southeast margin of the kopeh dagh fault system the ascending and descending interferograms indicate thrust dominated slip with the maximum line of sight displacement of 10 5 and 13 7 cm respectively the detailed slip distribution of the 2017 sangsefid mw6 1 earthquake inferred from geodetic data is presented here for the first time although the insar interferograms themselves do not uniquely constrain what the primary slip surface is we infer that the source fault dips to southwest by analyzing the 2 5 d displacement field decomposed from the insar observations the determined uniform slip fault model shows that the dip angle of the seimogenic fault is approximately 40 with a strike of 120 except for a narrower fault width than that predicted by the empirical scaling law we suggest that geometric complexities near the kopeh dagh fault system obstruct the rupture propagation resulting in high slip occurred within a small area and much higher stress drop than global estimates the insar determined moment is 1 71 1018 nm with a shear modulus of 3 32 1010 n m2 equivalent to mw 6 12 which is consistent with seismological results the finite fault model the west dipping fault plane reveals that the peak slip of 0 90 m occurred at a depth of 6 3 km with substantial slip at a depth of 4 10 km and a near uniform slip of 0 1 m at a depth of 0 2 5 km we suggest that the sangsefid earthquake occurred on an unknown blind reverse fault dipping southwest which can also be recognised through observing the long term surface effects due to the existence of the blind fault

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

internal waves across the pacific 1 the long range propagation of the semidiurnal internal tide northward from the hawaiian ridge and its susceptibility to parametric subharmonic instability psi at the critical latitude c 28 8 n were examined in spring 2006 with intensive shipboard and moored observations spanning 25 37 n along a tidal beam velocity and shear at c were dominated by intense vertically standing inertially rotating bands of several hundred meters vertical wavelength these occurred in bursts following spring tide contrasting sharply with the downward propagating wind generated features seen at other latitudes these marginally stable layers which have inverse 16 meter richardson number ri16 1 0 7 are interpreted as the inertial waves resulting from psi of the internal tide elevated near inertial energy and parameterized diapycnal diffusivity and reduced asymmetry in upgoing downgoing energy were also observed at and equatorward of c yet simultaneous moored measurements of semidiurnal energy flux and 1 km deep velocity sections measured from the ship indicate that the internal tide propagates at least to 37 n with no detectable energy loss or phase discontinuity at c our observations indicate that psi occurs in the ocean with sufficient intensity to substantially alter the inertial shear field at and equatorward of c but that it does not appreciably disrupt the propagation of the tide at our location

annual cycle and depth penetration of wind generated near inertial internal waves at ocean station papa in the northeast pacific abstractthe downward propagation of near inertial internal waves following winter storms is examined in the context of a 2 yr record of velocity in the upper 800 m at ocean station papa the long time series allow accurate estimation of wave frequency whereas the continuous data in depth allow separation into upward and downward propagating components near inertial kinetic energy kein dominates the record at all measured depths energy in downgoing motions exceeds that of upward propagating motions by factors of 3 7 whereas kein is elevated by a factor of 3 5 in winter relative to summer the two successive winters are qualitatively similar but show important differences in timing and depth penetration energy is seen radiating downward in a finite number of wave groups which are tagged and catalogued to determine the vertical group velocity cgz which has a mean of about 1 5 10 4 m s 1 13 m day 1 case studies of three of these are presented in detail downward energy flux is estimated as cgz

observations of energetic high wavenumber internal waves in the kuroshio abstract intense and spatially coherent shear layers were detected in and under the kuroshio in an april 2000 survey in the east china sea the sloping layers revealed by shipboard doppler sonars on the r v roger revelle appeared to cross isopycnal surfaces except in a small region near the kuroshio shelfbreak front the rms finescale shear associated with the layers significantly exceeded the geostrophic shear an april 2002 follow on cruise was organized to establish whether these motions were propagating internal waves shipboard and lowered adcps were both operated from the r v melville in addition to ctd sonar transects a 30 h time series of currents and shear was obtained in the core of the kuroshio near the island of kyushu japan the shear structures were indeed found to be propagating with both up and down going internal wave motions present in comparison with the nearby open ocean the finescale 160 m vertical shear variance is increased by a factor of 3 in the kuroshio and by a fact

depth dependent rupture mode along the ecuador colombia subduction zone a large earthquake mw 7 7 occurred on 16 april 2016 within the source region of the 1906 earthquake in the ecuador colombia subduction zone the 1906 event has been interpreted as a megathrust earthquake mw 8 8 that ruptured the source regions of smaller earthquakes in 1942 1958 and 1979 in this subduction our seismic analysis indicated that the spatial distribution of the 2016 earthquake and its aftershocks correlated with patches of high interplate coupling strength and was similar to those of the 1942 earthquake and its aftershocks suggesting that the 2016 and 1942 earthquakes ruptured the same asperity our analysis of tsunami waveforms of the 1906 event indicated mw around 8 4 and showed that large slip occurred near the trench off the source regions of the above three historical and the 2016 earthquakes suggesting that a depth dependent complex rupture mode exists along this subduction zone

trapped near inertial waves and enhanced chlorophyll distributions waves with near inertial frequencies were observed along a front associated with a large mesoscale feature in the sargasso sea during the late summer of 1987 high subsurface chlorophyll concentrations occurred on the edge of this front coincident with the wave packets the amplitude of the waves increased with time and kinetic energy propagated downward reducing 20 m richardson numbers in the thermocline to 1 or less chlorophyll levels were episodic showing no periodicity coincident with wave dynamics however on two occasions chlorophyll concentration increased from 1 mg chl m 3 several hours after the waves penetrated the thermocline it was hypothesized that mixing associated with shear instabilities stimulated new production a diffusivity model combined with nutrient data produced a phytoplankton bloom that accounted for only one of the maxima the other increase in chlorophyll may have been the result of horizontal advection of the wave packets near the front

slip segmentation and slow rupture to the trench during the 2015 mw8 3 illapel chile earthquake the 2015 mw8 3 illapel chile earthquake is the latest megathrust event on the central segment of that subduction zone it generated strong ground motions and a large up to 11 m runup tsunami which prompted the evacuation of more than 1 million people in the first hours following the event observations during recent earthquakes suggest that these phenomena can be associated with rupture on different parts of the megathrust the deep portion generates strong shaking while slow large slip on the shallow fault is responsible for the tsunami it is unclear whether all megathrusts can have shallow slip during coseismic rupture and what physical properties regulate this here we show that the illapel event ruptured both deep and shallow segments with substantial slip we resolve a kinematic slip model using regional geophysical observations and analyze it jointly with teleseismic backprojection we find that the shallow and deep portions of the megathrust are segmented and have fundamentally different behavior we forward calculate local tsunami propagation from the resolved slip and find good agreement with field measurements independently validating the slip model these results show that the central portion of the chilean subduction zone has accumulated a significant shallow slip deficit and indicates that given enough time shallow slip might be possible everywhere along the subduction zone

supercycle at the ecuadorian subduction zone revealed after the 2016 pedernales earthquake large earthquakes are usually assumed to release all of the strain accumulated since the previous event implying a reduced seismic hazard after them however long records of seismic history at several subduction zones suggest supercycle behaviour where centuries long accumulated strain is released through clustered large earthquakes resulting in an extended period of enhanced seismic hazard here we combine historical seismology results present day geodesy data and dense local observations of the recent mw 7 8 2016 pedernales earthquake to reconstruct the strain budget at the ecuador subduction zone since the great 1906 earthquake we show that the pedernales earthquake involved the successive rupture of two patches on the plate interface that were locked prior to the earthquake and most probably overlaps the area already ruptured in 1942 by a similar earthquake however we find that coseismic slip in 2016 exceeds the deficit accumulated since 1942 the seismic moment of every large earthquake during the twentieth century further exceeds the moment deficit accumulated since 1906 these results together with the seismic quiescence before 1906 highlighted by historical records and marine palaeoseismology argue for an earthquake supercycle at the ecuador colombia margin this behaviour which has led to an enhanced seismic hazard for 110 years is possibly still going on and may apply to other subduction zones that recently experienced a great earthquake large earthquakes are often assumed to reset the seismic hazard of a region analysis of recent and historical seismicity in ecuador suggests that this region may experience clusters of large earthquakes and extended periods of high seismic hazard

forced ocean response during the frontal air sea interaction experiment a central hypothesis of the frontal air sea interaction experiment fasinex was that the strong gradients in the upper ocean associated with ocean fronts would spatially modulate the response of the ocean to local atmospheric forcing to test this hypothesis measurements of near surface meteorology and upper ocean variability were made for 5 months from an array of moorings and for one of those 5 months from two ships a number of fronts passed through the moored array and the moored meteorological and current meter data were used to examine the response of the upper ocean to atmospheric forcing at subinertial and near inertial frequencies at low frequencies an ekmanlike frictionally driven component in the mixed layer and a more deeply penetrating component thought to be forced by ekman pumping were found strong near inertial response was found in the mixed layer the near inertial motion showed considerable spatial variability in the seasonal thermocline here it was evident that the structure of the front influenced the downward propagating near inertial internal waves data were also obtained by profiling instruments deployed along cross frontal sections these data were used to examine the spatial and temporal variability of the internal waves microstructure and dissipation and the relation of that variability to oceanic fronts and atmospheric events the spectral densities of the components of the internal waves that rotated clockwise with increasing depth were higher in regions of negative relative vorticity than those predicted by garrett and munk munk 1981 and estimates of clockwise and total shear were highest in regions of negative relative vorticity in the strong shear of the ocean front significant anisotropy of the internal wave field was observed and kinetic energy dissipation levels relative to the rate of work by the wind were higher than previously reported

boundary layer upper ocean and ice observations in the greenland sea marginal ice zone during the 1984 marginal ice zone experiment a coordinated ocean boundary layer and mixed layer experiment was carried out in concert with a complete heat and mass balance study in the summer marginal ice zone miz of the greenland sea the measurements were made at two drifting ice stations and included observations of ocean boundary layer turbulence profiles of water temperature salinity and velocity ice ablation ice concentration solar radiation and spectral albedos ocean conditions were found to be extremely variable the ice and water velocities were heavily influenced by tidal and inertial motions with amplitudes from 6 to 12 cm s 1 in the course of the drift a 30 km eddy was crossed wherein ice and water velocities exceeded 15 cm s 1 the northern extension of the east greenland polar front was encountered and a northward flow of atlantic water into the arctic basin was observed below the eastern edge of the front but the drift station never moved quite far enough west to be caught in the southward transport of arctic surface water heat from the ocean was a major factor in ice melt and when the ice was over atlantic water it was the dominant factor the events that had the greatest impact on the ice were two outbreaks during which off ice winds blew the ice across warm ice edge ocean fronts once south of these fronts and over surface water as warm as 1 c the ice bottom melted at rates up to 100 kg m 2 d 1 the rapid changes in stratification associated with the outbreaks had a dramatic impact on the drag and heat transfer coefficients the drag coefficient relative to the square of the relative water velocity at 30 m ranged from 0 002 to 0 02 and averaged 0 006 the heat transfer coefficient relative to the friction velocity u and the mixed layer temperature elevation above freezing ranged from 0 0025 to 0 009 and averaged 0 0038 in agreement with the idea that stratification inhibits turbulent exchange the heat transfer coefficient decreased when stratification increased in fact the observed melt rates can be simulated well if molecular heat and salt transfer through a thin near surface laminar boundary layer are accounted for as well as transfer through the turbulent outer boundary layer also in agreement with turbulent boundary layer theory the drag coefficient decreased when stratification increased slightly above neutral however for the large increases in surface stratification the drag coefficient increased this was due to the generation of internal gravity waves by ice bottom roughness because the surface exchange coefficients are so sensitive to surface stratification which is in turn highly variable in the miz accurate simulations of ice motion and ice melt will require realistic estimates of stratification and a good understanding of the relation between the ice ocean interactions and upper ocean conditions

joint inversion of gps insar and teleseismic data sets for the rupture process of the 2015 gorkha nepal earthquake using a generalized abic method abstract various observations are made to invert for the source model of the 2015 gorkha earthquake previously published slip models involve different slip distributions and slip amplitudes to obtain a robust model we jointly invert for the rupture process of the gorkha earthquake using three types of observations global positioning system gps interferometric synthetic aperture radar insar and teleseismic p wave data three constraints i e spatial and temporal smoothness and minimum moment constraints are applied to regulate the rupture process the weight ratios between data sets and prior constraints are determined from a new developed generalized akaike s bayesian information criterion gabic weight determination method this gabic method can simultaneously and objectively weigh various kinds of observations and prior constraints rather than being limited to the two types in the traditional abic method the inverted slip model reveals the seismic moment of the earthquake is 9 40 10 20 n m released primarily in the first 60 s equivalent to mw 7 92 the rupture front propagates unilaterally along the strike direction and spreads in both the strike and dip directions the slip distribution shows one large slip patch with two peaks along the strike direction with a maximum slip amplitude of approximately 7 6 m and identifies large slips 2 m that occur in the updip section of the main himalayan thrust mht fault plane our results indicate that the released slip amplitude is larger than the accumulated slip amplitude since 1833 so the 2015 earthquake likely does not overlap with the 1833 earthquake

the 16 april 2016 mw 7 8 ms 7 5 ecuador earthquake a quasi repeat of the 1942 ms 7 5 earthquake and partial re rupture of the 1906 ms 8 6 colombia ecuador earthquake the 2016 ecuador m w 7 8 earthquake ruptured the subduction zone boundary between the nazca and south american plates joint modeling of seismic and tsunami observations indicates an 120 km long rupture area beneath the coastline north of the 1998 m w 7 2 rupture the slip distribution reveals two discrete asperities near the hypocenter and around the equator their locations and the patchy pattern are consistent with the prior interseismic geodetic strain which showed highly locked patches also beneath the coastline aftershocks cluster along two streaks one aligned nearly parallel to the plate convergence direction up dip of the main slip patches and the other on a trench perpendicular lineation south of the 1958 rupture zone comparisons of seismic waveforms and magnitudes show that the 2016 event and 1942 earthquakes have similar surface wave magnitude m s 7 5 overlapping rupture areas and similar main pulses of moment rate the same area ruptured as the southernmost portion of the larger earthquake of 1906 m w 8 6 m s 8 6 the seismic behavior reflects persistent heterogeneous frictional properties of the colombia ecuador megathrust

observations of near inertial surface currents off oregon decorrelation time and length scales 1 high resolution km in space and hourly in time surface currents observed by an array of high frequency radars off oregon are analyzed to quantify the decorrelation time and length scales of their near inertial motions the near inertial surface currents are dominantly clockwise with amplitudes of 9 12 cm s 1 however they appear asymmetric and elliptical as a result of counterclockwise inertial motions with magnitudes in a range of 2 5 cm s 1 the decorrelation time and length scales are computed from the decay slope of the near inertial peak and the spatial coherence in the near inertial frequency band respectively decorrelation time scales of clockwise near inertial motions increase from 2 days nearshore within 30 km from the coast to 6 days offshore and their length scales increase from 30 to 90 km seaward possibly due to coastal inhibition the local spatial coherence has an exponentially decaying structure for both clockwise and counterclockwise rotations and their phases propagate northwestward offshore for clockwise and northeastward onshore for counterclockwise rotations

interaction of superinertial waves with submesoscale cyclonic filaments in the north wall of the gulf stream abstracthigh resolution nearly lagrangian observations of velocity and density made in the north wall of the gulf stream reveal banded shear structures characteristic of near inertial waves niws here the current follows submesoscale dynamics with rossby and richardson numbers near one and the vertical vorticity is positive this allows for a unique analysis of the interaction of niws with a submesoscale current dominated by cyclonic as opposed to anticyclonic vorticity rotary spectra reveal that the vertical shear vector rotates primarily clockwise with depth and with time at frequencies near and above the local coriolis frequency f at some depths more than half of the measured shear variance is explained by clockwise rotary motions with frequencies between f and 1 7f the dominant superinertial frequencies are consistent with those inferred from a dispersion relation for niws in submesoscale currents that depends on the observed aspect ratio of the wave shear as well as the vertical vorticity

space time scales of shear in the north pacific abstractthe spatial temporal and directional characteristics of shear are examined in the upper 1400 m of the north pacific during late spring with an array of five profiling moorings deployed from 25 to 37 n 1330 km and simultaneous shipboard transects past them the array extended from a regime of moderate wind generation at the north to south of the critical latitude 28 8 n where parametric subharmonic instability psi can transfer energy from semidiurnal tides to near inertial motions analyses are done in an isopycnal following frame to minimize contamination by doppler shifting approximately 60 of rms shear at vertical scales 20m and 80 for vertical scales 80 m is contained in near inertial motions an inertial back rotation technique is used to index shipboard observations to a common time and to compute integral time scales of the shear layers persistence times are o 7 days at most moorings but o 25 days at the critical latitude simultaneous shipboard transects show that these sh

role of near inertial internal waves in subthermocline diapycnal mixing in the northern gulf of mexico abstractmoored adcp data collected in the northern gulf of mexico are analyzed to examine near inertial internal waves and their contribution to subthermocline diapycnal mixing based on a finescale parameterization of deep ocean mixing the focus of the study is on the impact of near inertial internal waves generated by an extreme weather event that is hurricane katrina and by month to month variation in weather patterns on the diapycnal mixing the inferred subthermocline diapycnal mixing exhibits pronounced elevation in the wake of katrina both the increased near inertial 0 8 1 8f where f is the coriolis frequency and superinertial 1 8f shear variances contribute to the elevated diapycnal mixing but the former plays a more dominant role the intense wind work on near inertial motions by the hurricane is largely responsible for the energetic near inertial shear variance energy transfer from near inertial to superinertial internal waves however appears to play an important role in elevating th

the upper ocean response to monsoonal forcing in the arabian sea seasonal and spatial variability abstract observations from four towed profiler surveys undertaken between december 1994 and october 1995 examine the seasonal and spatial variability of the upper ocean response to the monsoon cycle in the arabian sea although observed atmospheric forcing agrees well with modern climatologies cross basin patterns of mixed layer depth and water properties observed in 1994 1995 are not entirely consistent with an upper ocean response dominated by ekman pumping during the winter monsoon the mixed layer deepens dramatically with distance offshore surface cooling intensifies with offshore distance and a one dimensional response dominated by convective overturning could explain observed wintertime mixed layer depths except for waters associated with a filament extending offshore from the omani coast mixed layer depths and water properties show only modest cross basin contrasts during the southwest monsoon filament waters differ from surrounding mid basin waters having shallow mixed layers and water properties similar to those of waters upwelled near the omani coast in september following the southwest monsoon waters within 1000 km of the omani coast have cooled and freshened with marked changes in stratification extending well into the pycnocline estimates of ekman pumping and wind driven entrainment made using the southampton oceanographic center 1980 1995 surface flux and the levitus mixed layer climatologies indicate that during the southwest monsoon wind driven entrainment is considerably stronger than ekman pumping inshore of the windstress maximum ekman pumping partially counters wind driven entrainment while offshore the two processes act together to deepen the mixed layer as ekman pumping is too weak to counter wind driven mixed layer deepening inshore of the windstress maximum another mechanism must act to maintain the shallow mixed layers seen in our observations and in climatologies offshore advection of coastally upwelled water offers a mechanism for maintaining upper ocean stratification that is consistent with observed changes in upper ocean water properties ekman upwelling will modulate wind driven entrainment but these results indicate that the primary mechanisms acting inshore of the windstress maximum are wind driven mixing and horizontal advection

near inertial wave propagation in the western arctic abstract from october 1997 through october 1998 the surface heat budget of the arctic sheba ice camp drifted across the western arctic ocean from the central canada basin over the northwind ridge and across the chukchi cap during much of this period the velocity and shear fields in the upper ocean were monitored by doppler sonar near inertial internal waves are found to be the dominant contributors to the superinertial motion field typical rms velocities are 1 2 cm s 1 in this work the velocity and shear variances associated with upward and downward propagating wave groups are quantified patterns are detected in these variances that correlate with underlying seafloor depth these are explored with the objective of assessing the role that these extremely low energy near inertial waves play in the larger scale evolution of the canada basin the specific focus is the energy flux delivered to the slopes and shelves of the basin available for driving mixing at the ocean boundaries the energy and

motion of continental slivers and creeping subduction in the northern andes regions of intense continental deformation termed continental slivers have been identified in chile bolivia and ecuador analyses of gps data now identify another large sliver in peru the inca sliver that is moving away from a neighbouring sliver in ecuador implying that moving continental slivers control the deformation of almost the entire andean mountain range

variable rupture mode of the subduction zone along the ecuador colombia coast three large earthquakes occurred within the rupture zone of the 1906 colombia ecuador earthquake m w 8 8 in 1942 m s 7 9 1958 ms 7 8 and 1979 m s 7 7 we compared the size and mechanism of these earthquakes by using long period surface waves tsunami data and macroseismic data the 1979 event is a thrust event with a seismic moment of 2 9 10 28 dyne cm and represents subduction of the nazca plate beneath south america the rupture length and direction are 230 km and n40 e respectively examination of old seismograms indicates that the 1906 event is also a thrust event which ruptured in the northeast direction the seismic moment estimated from the tsunami data and the size of the rupture zone is 2 10 29 dyne cm the 1942 and 1958 events are much smaller about 1 5 to 1 10 of the 1979 event in the seismic moment than the 1979 event we conclude that the sum of the seismic moments of the 1942 1958 and 1979 events is only formula of that of the 1906 event despite the fact that the sequence of the 1942 1958 and 1979 events ruptured approximately the same segment as the 1906 event this difference could be explained by an asperity model in which the fault zone is held by a discrete distribution of asperities with weak zones in between the weak zone normally behaves aseismically but slips abruptly only when it is driven by failure of the asperities a small earthquake represents failure of one asperity and the rupture zone is pinned at both ends by adjacent asperities so that the effective width and the amount of slip are relatively small a great earthquake represents failure of more than one asperity and consequently involves much larger width and slip

historical 1942 ecuador and 1942 peru subduction earthquakes and earthquake cycles along colombia ecuador and peru subduction segments two large shallow earthquakes occurred in 1942 along the south american subduction zone inclose proximity to subducting oceanic ridges the 14 may event occurred near the subducting carnegie ridge off the coast of ecuador and the 24 august event occurred off the coast of southwestern peru near the southern flank of the subducting nazca ridge source parameters for these for these two historic events have been determined using long periodp waveforms p wave first motions intensities and local tsunami data we have analyzed thep waves for these two earthquakes to constrain the focal mechanism depth source complexity and seismic moment modeling of thep waveform for both events yields a range of acceptable focal mechanisms and depths all of which are consistent with underthrusting of the nazca plate beneath the south american plate the source time function for the 1942 ecuador event has one simple pulse of moment release with a duration of 22 suconds suggesting that most of the moment release occurred near the epicenter the seismic moment determined from thep waves is 6 8 1020n m corresponding ot a moment magnitude of 7 8 7 9 the reported location of the maximum intensities ix for this event is south of the main shock epicenter the relocated aftershcks are in an area that is approximately 200 km by 90 km elongated parallel to the trench with the majority of aftershocks north of the epicenter in contrast the 1942 peru event has a much longer duration and higher degree of complexity than the ecuador earthquake suggesting a heterogeneous rupture seismic moment is released in three distinct pulses over approximately 74 seconds the largest moment release occurs 32 seconds after rupture initiation the seismic moment as determined from thep waves for the 1942 peru event is 10 25 1020n m corresponding to a moment magnitude of 7 9 8 2 aftershock locations reported by the iss occur over a broad area surrounding the main shock the reported locations of the maximum intensities ix are concentrated south of the epicenter suggesting that at least part of the rupture was to the south we have also examined great historic earthquakes along the colombia ecuador and peru segments of the south american subduction zone we find that the size and rupture length of the underthrusting earthquakes vary between successive earthquake cycles this suggests that the segmentation of the plate boundary as defined by earthquakes this century is not constant

baroclinic energy flux at the hawaiian ridge observations from the r p flip abstract estimates of baroclinic energy flux are made in the immediate nearfield september october 2002 and 450 km offshore farfield october november 2001 of the kaena ridge an active barotropic to baroclinic conversion site the flux estimates are based on repeated profiles of velocity and density obtained from the research platform floating instrument platform flip as an aspect of the hawaii ocean mixing experiment energetic beams associated with both semidiurnal and diurnal internal waves are observed in the kauai channel beam depths and orientations are consistent with generation along the upper flanks of the ridge at the far field site the baroclinic energy flux is borne primarily by first mode semidiurnal waves the energy flux associated with the entire spectrum of internal waves is computed by cross spectral analysis significant energy fluxes are found in the inertial diurnal semidiurnal and twice semidiurnal frequency bands the semidiurnal energy flux strongly dominates the s

influence of varying upper ocean stratification on coastal near inertial currents the influence of varying horizontal and vertical stratification in the upper layer o 10 m associated with riverine waters and seasonal atmospheric fluxes on coastal near inertial currents is investigated with remotely sensed and in situ observations of surface and subsurface currents and realistic numerical model outputs off the coast of oregon based on numerical simulations with and without the columbia river cr during summer the directly wind forced near inertial surface currents are enhanced by 30 60 when the near surface layer has a stratified condition due to riverine water inputs from the cr comparing model results without the cr for summer and winter conditions indicates that the directly wind forced near inertial surface current response to a unit wind forcing during summer are 20 70 stronger than those during winter depending on the cross shore location which is in contrast to the seasonal patterns of both mixed layer depth and amplitudes of near inertial currents the model simulations are used to examine aspects of coastal inhibition of near inertial currents manifested in their spatial coherence in the cross shore direction where the phase propagates upward over the continental shelf bounces at the coast and continues increasing upward offshore toward surface and then downward offshore at the surface with magnitudes and length scales in the near surface layer increasing offshore this pattern exhibits a particularly well organized structure during winter similarly the raypaths of clockwise near inertial internal waves are consistent with the phase propagation of coherence showing the influence of upper layer stratification and coastal inhibition

origin of a crustal splay fault and its relation to the seismogenic zone and underplating at the erosional north ecuador south colombia oceanic margin 1 splay faults within accretionary complexes are commonly associated with the updip limit of the seismogenic zone prestack depth migration of a multichannel seismic line across the north ecuador south colombia oceanic margin images a crustal splay fault that correlates with the seaward limit of the rupture zone of the 1958 mw 7 7 tsunamogenic subduction earthquake the splay fault separates 5 6 6 km s velocity inner wedge basement rocks which belong to the accreted gorgona oceanic terrane from 4 to 5 km s velocity outer wedge rocks the outer wedge is dominated by basal tectonic erosion despite a 3 km thick trench fill subduction of 2 km high seamount prevented tectonic accretion and promotes basal tectonic erosion the low velocity and poorly reflective subduction channel that underlies the outer wedge is associated with the aseismic decollement thrust subduction channel fluids are expected to migrate upward along splay faults and alter outer wedge rocks conversely duplexes are interpreted to form from and above subducting sediment at 14 to 15 km depths between the overlapping seismogenic part of the splay fault and the underlying aseismic decollement coeval basal erosion of the outer wedge and underplating beneath the apex of inner wedge control the margin mass budget which comes out negative intraoceanic basement fossil listric normal faults and a rift zone inverted in a flower structure reflect the evolution of the gorgona terrane from cretaceous extension to likely eocene oblique compression the splay faults could have resulted from tectonic inversion of listric normal faults thus showing how inherited structures may promote fluid flow across margin basement and control seismogenesis

the 2011 tohoku oki earthquake displacement reaching the trench axis we detected and measured coseismic displacement caused by the 11 march 2011 tohoku oki earthquake moment magnitude mw 9 0 by using multibeam bathymetric surveys the difference between bathymetric data acquired before and after the earthquake revealed that the displacement extended out to the axis of the japan trench suggesting that the fault rupture reached the trench axis the sea floor on the outermost landward area moved about 50 meters horizontally east southeast and 10 meters upward the large horizontal displacement lifted the sea floor by up to 16 meters on the landward slope in addition to the vertical displacement

near inertial current oscillations off the mid east coast of korea abstract near inertial current oscillations were observed at depths of 620 and 790 m at a current meter mooring station in water 840 m deep off the mid east coast of korea the oscillatory inertial motions with an amplitude of up to 8 cm s existed during 73 days between august 27 and november 7 of 1986 with a large temporal variation in speed spectral analysis of the data was conducted and the result showed that the most dominant signal in the records was clockwise rotation whose frequency was close to the inertial frequency the peak frequency of the near inertial oscillations was slightly greater than the local inertial frequency f 0 0511 cph by 2 5 these clockwise oscillations had the mean amplitude of about 2 5 cm s reaching an instantaneous maximum of 7 5 cm s the mean ratio of the semi major axis to the semi minor one was found to be about 1 2 and the mean direction of the major axis was nearly parallel to the isobaths around the mooring station high near inertial energy parallel continuously during the first 15 days and then appeared in the form of group wave packets lasting several days during the remaining period three prominent events of wave packets were more energetic at the deeper depth the phase difference between the two horizontal near inertial current vectors changed largely with time but it remained relatively constant during each of the three energetic events changing its sign from one event to another the horizontal near inertial current vector rotated clockwise with increasing depth during one event but counterclockwise during the other two events the corresponding phase propagation was upward with a phase speed of 2 5 cm s for the clockwise polarization with depth but downward with 1 8 and 1 1 cm s for the counterclockwise rotating events

fault slip distribution of the 1999 mw 7 1 hector mine california earthquake estimated from satellite radar and gps measurements we use a combination of satellite radar and gps data to estimate the slip distribution of the 1999 m w 7 1 hector mine earthquake a right lateral strikeslip earthquake that occurred on a northwest southeast striking fault in the southern california mojave desert the data include synthetic aperture radar interferograms insar from both ascending and descending orbits radar amplitude image offset fields sario for both ascending and descending azimuth directions and campaign gps observations from 55 stations provided by agnew et al 2002 we model the fault with nine segments derived from the field mapped fault rupture the sario data and aftershock locations we first estimate the dip of each fault segment as well as a single constant strike slip component across each segment resulting in an average dip of 83 to the northeast and slip of up to 5 6 m then we fix the optimal fault segment dip discretize the fault segments into 1 5 km 1 5 km patches and solve for the variable slip distribution using a nonnegative least squares method that includes an appropriate degree of smoothing our preferred solution has both right lateral strike slip and reverse faulting the estimated geodetic moment is 5 93 10 19 n m m w 7 1 similar to seismological estimates indicating that there are insignificant interseismic and postseismic deformation signals in the data we find strike slip displacements of up to 6 0 m and reverse faulting of up to 1 6 m with the maximum slip located just northwest of the epicenter most of the slip is concentrated northwest and south of the epicenter little slip is found on the northeastern branch of the fault the sario data and our modeling indicate that the amount and extent of surface fault rupture were underestimated in the field

the 2011 magnitude 9 0 tohoku oki earthquake mosaicking the megathrust from seconds to centuries geophysical observations from the 2011 moment magnitude m w 9 0 tohoku oki japan earthquake allow exploration of a rare large event along a subduction megathrust models for this event indicate that the distribution of coseismic fault slip exceeded 50 meters in places sources of high frequency seismic waves delineate the edges of the deepest portions of coseismic slip and do not simply correlate with the locations of peak slip relative to the m w 8 8 2010 maule chile earthquake the tohoku oki earthquake was deficient in high frequency seismic radiation a difference that we attribute to its relatively shallow depth estimates of total fault slip and surface secular strain accumulation on millennial time scales suggest the need to consider the potential for a future large earthquake just south of this event

seismicity associated with the great colombia ecuador earthquakes of 1942 1958 and 1979 implications for barrier models of earthquake rupture abstract we have relocated earthquakes along the colombia ecuador coast with the method of joint hypocenter determination in order to examine the nature of fault heterogeneities that controlled northward propagation of plate boundary rupture from the source region of the earthquake of 14 may 1942 to the source region of the 19 january 1958 earthquake and eventually to the source region of the earthquake of 12 december 1979 the entire region of the 1942 1958 and 1979 shocks had previously ruptured in the single great earthquake of 31 january 1906 the relocated hypocenters lie on the same plane to within the approximately 20 km uncertainty of the focal depths also the main shocks nucleated at nearly the same distance from the colombia trench these observations suggest that the heterogeneities between the 1942 and 1958 ruptures and between the 1958 and 1979 ruptures do not correspond to a major distortion of the downgoing slab but rather to either minor distortions of the slab or to regions of high friction or low available strain energy on a continuous fault surface in particular the heterogeneity between the 1958 and 1979 rupture zones seems to have been a high strength barrier with dimensions much smaller than the dimensions of either of the rupture zones the 1942 and 1958 earthquakes had source dimensions no larger than the 1979 main shock but they had stronger aftershock sequences than the 1979 earthquake this observation suggests that the arrest of earthquake rupture in 1979 left the plate boundary segment that had ruptured in 1906 in a state of lower stress than it had been following the 1942 and 1958 earthquakes long term seismicity in the decades preceding the 1979 earthquake occurred mostly outside or on the boundaries of the rupture area defined by the distribution of 1979 aftershocks the intense aftershock activity that followed the 1958 main shock within tens of kilometers of the eventual 1979 hypocenter may correspond to a long term precursory seismic swarm for the 1979 earthquake

tectonic segmentation of the north andean margin impact of the carnegie ridge collision the north andean convergent margin is a region of intense crustal deformation with six great subduction earthquakes mw 7 8 this century the regional pattern of seismicity and volcanism shows a high degree of segmentation along strike of the andes segments of steep slab subduction alternate with aseismic regions and segments of flat slab subduction this segmentation is related to heterogeneity on the subducting nazca plate in particular the influence of the carnegie ridge collision is investigated four distinct seismotectonic regions can be distinguished region 1 from 6on to 2 5on with steep ese dipping subduction and a narrow volcanic arc region 2 from 2 5on to 1os showing an intermediate depth seismic gap and a broad volcanic arc region 3 from 1os to 2os with steep ne dipping subduction and a narrow volcanic arc region 4 south of 2os with flat subduction and no modern volcanic arc the carnegie ridge has been colliding with the margin since at least 2 ma based on examination of the basement uplift signal along trench parallel transects the subducted prolongation of carnegie ridge may extend up to 500 km from the trench as suggested by the seismic gap and the perturbed broad volcanic arc these findings conflict with previous tectonic models suggesting that the carnegie ridge entered the trench at 1 ma furthermore the anomalous geochemical adakitic signature of the volcanoes in the broad ecuador volcanic arc and the seismicity pattern are proposed to be caused by lithospheric tears separating the buoyant shallowly subducting carnegie ridge from segments of steep subduction in regions 1 and 3 it is further suggested that carnegie ridge supports a local flat slab segment similar to that observed in peru the impact of the carnegie ridge collision on the upper plate causes transpressional deformation extending inboard to beyond the volcanic arc with a modern level of seismicity comparable to the san andreas fault system the pattern of instrumental and historical seismicity indicates 1 great earthquakes on the northern and southern flanks of the colliding ridge 2 a slight reduction in observed seismicity at the trench ridge intersection 3 increased stress far into the continent and 4 a nne displacement of the n andes block to be further effects of the collision 1999 elsevier science b v all rights reserved

are rupture zone limits of great subduction earthquakes controlled by upper plate structures evidence from multichannel seismic reflection data acquired across the northern ecuador southwest colombia margin 1 subduction of the nazca plate beneath the ecuador colombia margin has produced four megathrust earthquakes during the last century the 500 km long rupture zone of the 1906 mw 8 8 event was partially reactivated by three thrust events in 1942 mw 7 8 1958 mw 7 7 and 1979 mw 8 2 whose rupture zones abut one another multichannel seismic reflection and bathymetric data acquired during the sisteur cruise show evidence that the margin wedge is segmented by transverse crustal faults that potentially correlate with the limits of the earthquake coseismic slip zones the paleogene neogene jama quininde and esmeraldas crustal faults define a 200 km long margin crustal block that coincides with the 1942 earthquake rupture zone subduction of the buoyant carnegie ridge is inferred to partially lock the plate interface along central ecuador however coseismic slip during the 1942 and 1906 earthquakes may have terminated against the subducted northern flank of the ridge we report on a newly identified manglares crustal fault that cuts transversally through the margin wedge and correlates with the limit between the 1958 and 1979 rupture zones during the earthquake cycle the fault is associated with high stress concentration on the plate interface an outer basement high which bounds the margin seaward of the 1958 rupture zone may act as a deformable buttress to seaward propagation of coseismic slip along a megathrust splay fault coseismic uplift of the basement high is interpreted as the cause for the 1958 tsunami we propose a model of weak transverse faults which reduce coupling between adjacent margin segments together with a splay fault and an asperity along the plate interface as controlling the seismogenic rupture of the 1958 earthquake

submesoscale water mass spectra in the sargasso sea submesoscale stirring contributes to the cascade of tracer variance from large to small scales multiple nested surveys in the summer sargasso sea with tow yo and autonomous platforms captured submesoscale water mass variability in the seasonal pycnocline at 20 60 m depths to filter out internal waves that dominate dynamic signals on these scales spectra for salinity anomalies on isopycnals were formed salinitygradient spectra are approximately flat with slopes of 20 2 6 0 2 over horizontal wavelengths of 0 03 10km while the two to three realizations presented here might be biased more representative measurements in the literature are consistent with a nearly flat submesoscale passive tracer gradient spectrum for horizontal wavelengths in excess of 1km a review of mechanisms that could be responsible for a flat passive tracer gradient spectrum rules out i quasigeostrophic eddy stirring ii atmospheric forcing through a relict submesoscale winter mixed layer structure or nocturnal mixed layer deepening iii a downscale vortical mode cascade and iv horizontal diffusion because of shear dispersion of diapycnal mixing internal wave horizontal strain appears to be able to explain horizontal wavenumbers of 0 1 7 cycles per kilometer cpkm but not the highest resolved wavenumbers 7 30cpkm submesoscale subduction cannot be ruled out at these depths though previous observations observe a flat spectrum well below subduction depths so this seems unlikely primitive equation numerical modeling suggests that nonquasigeostrophic subinertial horizontal stirring can produce a flat spectrum the last need not be limited to mode one interior or surface rossby wavenumbers of quasigeostrophic theory but may have a broaderband spectrum extending to smaller horizontal scales associated with frontogenesis and frontal instabilities as well as internal waves

strain budget of the ecuador colombia subduction zone a stochastic view the 2016 pedernales earthquake m w 7 8 ruptured a portion of the colombia ecuador subduction interface where several large historical earthquakes have been documented since the great 1906 earthquake m 8 6 considering all significant ruptures that occurred in the region it has been suggested that the cumulative moment generated co seismically along this part of the subduction over the last century exceeds the moment deficit accumulated inter seismically since 1906 such an excess challenges simple models with earthquakes resetting the elastic strain accumulated inter seismically in locked asperities these inferences are however associated with large uncertainties that are generally unknown the impact of spatial smoothing constraints on co seismic and inter seismic models also prevents any robust assessment of the strain budget we propose a bayesian kinematic slip model of the 2016 pedernales earthquake using the most comprehensive dataset to date including insar and gps offsets tsunami waveforms and kinematic records from high rate gps and strong motions in addition we use inter seismic geodetic velocities to produce a probabilistic inter seismic coupling model of the subduction interface our stochastic co seismic and inter seismic solutions include the ensemble of all plausible models consistent with our prior information and that fit the observations within uncertainties the analysis of these model ensembles indicates that an excess of co seismic moment during the 1906 2016 period is likely in central ecuador only if we assume that 1942 and 2016 earthquakes are colocated if this assumption is relaxed we show that this conclusion no longer holds given uncertainties in co and inter seismic processes the comparison of 1942 and 2016 teleseismic records reveals large uncertainties in the location of the 1942 event hampering our ability to draw strong conclusions on the unbalanced moment budget in the region our results also show a heterogeneous coupling of the subduction interface that coincides with two slip asperities in our co seismic model for the 2016 pedernales earthquake and with the location of historical ruptures in 1958 1979 and 1998 the spatial variability in coupling and complexity in earthquake history suggest strong heterogeneities in frictional properties of the subduction megathrust

a near inertial internal wave spectrum for the sargasso sea in late summer abstract independent estimates of the frequency wavenumber spectrum of near inertial waves for the sargasso sea in late summer were made using 8 time series of horizontal velocity from a single moored vertical array and 58 vertical profiles of horizontal velocity from a horizontal array of expendable velocity profilers the profiler data were analyzed to produce an internal wave frequency wavenumber spectrum with sufficient resolution to resolve the details of the inertial peak and compute the vertical energy flux comparison with the lower resolution spectrum from the moored array shows qualitative agreement the differences are most likely due to biases in both techniques and to intermittency of the internal wave field these data reveal a marked asymmetry of the near inertial internal wave field with a net downward enemy flux of 0 12 0 12 ergs cm 2 s 1 the downward propagating waves have more energy a larger horizontal scale and a lower frequency than the upward propagating waves the magnitude of t

near inertial mixing in the central arctic ocean observations were made in april 2007 of horizontal currents hydrography and shear microstructure in the upper 500m from a drifting ice camp in the central arctic ocean an approximately 4 day long time series collected about 10 days after a storm event shows enhanced near inertial oscillations in the first half of the measurement period with comparable upward and downward propagating energy rough estimates of wind work and near inertial flux imply that the waves were likely generated by the previous storm the nearinertial frequency band is associated with dominant clockwise rotation in time of the horizontal currents and enhanced dissipation rates of turbulent kinetic energy the vertical profile of dissipation rate shows elevated values in the pycnocline between the relatively turbulent underice boundary layer and the deeper quiescent water column dissipation averaged in the pycnocline is near inertially modulated and its magnitude decays approximately at a rate implied by the reduction of energy over time observations suggest that near inertial energy and internal wave induced mixing play a significant role in vertical mixing in the arctic ocean

inertial wave dynamics in the north atlantic subtropical zone doppler current profiler observations of an inertial wave packet are presented from a region where a cold core ring impinges on a front in this intense current a drogue is deployed to mark one region of the fluid as the drogue is advected by the current the ship follows it zigzagging across the drogue s trajectory along this ship track vertical rotary velocity spectra indicate the presence of a downgoing intertial wave with a vertical wavelength which slowly changes from 50 to 100 m as time progresses the wave s intrinsic frequency was measured for the first time ever a horizontally synoptic data set is obtained at the drogue depth by correcting for frontal advection and the temporal rotation of the wave velocity examination of these synoptic data indicates the presence of a southgoing near inertial wave with horizontal wavelength 20 km the wave is confined to a 25 km region supplementary ray tracing calculations through objective maps of the ring flow field indicate that the wave is strongly influenced by doppler shifting this is accompanied by a slow counterclockwise turning of the horizontal wave number vector a decrease in the intrinsic frequency and an increase in the vertical wavelength in qualitative agreement with the data a companion paper marmorino et al this issue details the effect of this inertial wave upon the small scale temperature activity with horizontal length scales of 1 3 m

slab1 0 a three dimensional model of global subduction zone geometries 1 we describe and present a new model of global subduction zone geometries called slab1 0 an extension of previous efforts to constrain the two dimensional non planar geometry of subduction zones around the focus of large earthquakes slab1 0 describes the detailed non planar three dimensional geometry of approximately 85 of subduction zones worldwide while the model focuses on the detailed form of each slab from their trenches through the seismogenic zone where it combines data sets from active source and passive seismology it also continues to the limits of their seismic extent in the upper mid mantle providing a uniform approach to the definition of the entire seismically active slab geometry examples are shown for two well constrained global locations models for many other regions are available and can be freely downloaded in several formats from our new slab1 0 website http on doi gov d9arbs we describe improvements in our two dimensional geometry constraint inversion including the use of average active source seismic data profiles in the shallow trench regions where data are otherwise lacking derived from the interpolation between other active source seismic data along strike in the same subduction zone we include several analyses of the uncertainty and robustness of our three dimensional interpolation methods in addition we use the filtered subduction related earthquake data sets compiled to build slab1 0 in a reassessment of previous analyses of the deep limit of the thrust interface seismogenic zone for all subduction zones included in our global model thus far concluding that the width of these seismogenic zones is on average 30 larger than previous studies have suggested

the isc gem global instrumental earthquake catalogue 1900 2009 introduction abstract in this introductory article we give a general description of the isc gem global instrumental earthquake catalogue 1900 2009 we also provide the background for four further articles that describe the effort in collecting and digitizing parametric earthquake bulletin data as well as the methodologies developed to compute homogeneous earthquake parameters the result of the two and a half year project is a catalogue of approximately 20 000 large earthquakes covering 110 years with hypocentres and uncertainties computed using the same technique and velocity model we show that the overall homogeneity of the main earthquake parameters in the catalogue was achieved despite changes in instrumentation and routine measurement practices concurrent with developments in instrumental seismology from almost a ground level to its current state for each earthquake mw magnitude values and uncertainties were computed either based on available estimates of seismic moment or using new empirical relationships between mw ms and mb further important results of this project include the electronic availability of a considerable volume of seismic wave arrival time and amplitude measurements from early instrumental printed station bulletins these newly recovered amplitude measurements provided a basis for computation of many previously unavailable ms magnitudes with uncertainties in this article we describe why such a catalogue is required for a comprehensive assessment of global and regional seismic hazard we also describe other potential uses of the catalogue in many other fields of earth sciences we discuss the catalogue availability and lay out the plans of further development

observations of shear and vertical stability from a neutrally buoyant float measurements of 1 to 5 m shear and strain from a neutrally buoyant float are used to examine the statistics and causes of shear instability in a 9 day record unstable conditions defined as vz n 2 where vz vz are due to higher than average shear rather than lower than average buoyancy frequency and there are no instances of unstable buoyancy frequency or overturns on the 0 5 m spacing of the thermistors shear is dominated by upward propagating near inertial motions unstable events were more frequent when a near inertial wave packet occupied the water parcel tracked by the float groups of unstable events occur roughly every 5 7 hours at scales 2 5 m and much less often at larger scales events typically last 10 min one buoyancy period or longer these time scales appear to be controlled by vertical advection of 1 m fine structure past the float sensors so do not represent the intrinsic time scales of instability turbulent and mixing quantities are estimated from these fine scale measurements giving a dissipation rate of e 2 3 16 10 10 w kg and an eddy diffusivity of k 3 10 6 m2 s in agreement with direct microstructure estimates therefore the float adequately resolves those quantities needed to estimate turbulent dissipation and could be used to monitor turbulent mixing in the ocean

rupture process of the 2016 mw 7 8 ecuador earthquake from joint inversion of insar data and teleseismic p waveforms abstract the 2016 ecuador earthquake ruptured the ecuador colombia subduction interface where several historic megathrust earthquakes had occurred in order to determine a detailed rupture model interferometric synthetic aperture radar insar images and teleseismic data sets were objectively weighted by using a modified akaika s bayesian information criterion abic method to jointly invert for the rupture process of the earthquake in modeling the rupture process a constrained waveform length method unlike the traditional subjective selected waveform length method was used since the lengths of inverted waveforms were strictly constrained by the rupture velocity and rise time the slip duration time the optimal rupture velocity and rise time of the earthquake were estimated from grid search which were determined to be 2 0 km s and 20 s respectively the inverted model shows that the event is dominated by thrust movement and the released moment is 5 75 1020 nm mw 7 77 the slip distribution extends southward along the ecuador coast line in an elongated stripe at a depth between 10 and 25 km the slip model is composed of two asperities and slipped over 4 m the source time function is approximate 80 s that separated into two segments corresponding to the two asperities the small magnitude of the slip occurred in the updip section of the fault plane resulted in small tsunami waves that were verified by observations near the coast we suggest a possible situation that the rupture zone of the 2016 earthquake is likely not overlapped with that of the 1942 earthquake

shallow ocean response to tropical cyclones observed on the continental shelf of the northwestern south china sea based on observed temperature and velocity in 2005 in northwestern south china sea the shallow ocean responses to three tropical cyclones were examined the oceanic response to washi was similar to common observations with 2 degrees c cooling of the ocean surface and slight warming of the thermocline resulted from vertical entrainment moreover the wavefield was dominated by first mode near inertial oscillations which were red shifted and trapped by negative background vorticity leading to an e folding timescale of 12 days the repeated reflections by the surface and bottom boundaries were thought to yield the successive emergence of higher modes the oceanic responses to vicente appeared to be insignificant with cooling of the ocean surface by only 0 5 degrees c and near inertial currents no larger than 0 10 m s as a result of a deepened surface mixed layer however the oceanic responses to typhoon damrey were drastic with cooling of 4 5 degrees c near the surface and successive barotropic like near inertial oscillations during the forced stage the upper ocean heat content decreased conspicuously by 11 65 and the stratification was thoroughly destroyed by vertical mixing in the relaxation stage the water particle had vertical displacement of 20 30 m generated by inertial pumping the current response to damrey was weaker than washi due to the deepened mixed layer and the destroyed stratification our results suggested that the shallow water oceanic responses to tropical cyclones varied significantly with the intensity of tropical cyclones and was affected by local stratification and background vorticity

recent crustal deformation and the earthquake cycle along the ecuador colombia subduction zone recent results from global positioning system gps measurements show deformation along the coast of ecuador and colombia that can be linked to the rupture zone of the earthquake in 1979 a 3d elastic boundary element model is used to simulate crustal deformation observed by gps campaigns in 1991 1994 1996 and 1998 deformation in ecuador can be explained best by 50 apparent locking on the subduction interface although there have not been any historic large earthquakes mw 7 south of the 1906 earthquake rupture zone 50 apparent elastic locking is necessary to model the deformation observed there in colombia only 30 apparent elastic locking is occurring along the subduction interface in the 1979 earthquake rupture zone mw 8 2 and no elastic locking is necessary to explain the crustal deformation observed at two gps sites north of there there is no evidence from seismicity or plate geometry that plate coupling on the subduction zone is reduced in colombia however simple viscoelastic models suggest that the apparent reduction in elastic locking can be explained entirely by the response of a viscous upper mantle to the 1979 earthquake these results suggest that elastic strain accumulation is occurring evenly throughout the study area but postseismic relaxation masks the true total strain rate

distribution of discrete seismic asperities and aseismic slip along the ecuadorian megathrust abstract a dense gps network deployed in ecuador reveals a highly heterogeneous pattern of interseismic coupling confined in the first 35 km depth of the contact between the subducting oceanic nazca plate and the north andean sliver interseismic models indicate that the coupling is weak and very shallow 0 15 km in south ecuador and increases northward with maximum found in the rupture areas of large mw 7 0 megathrust earthquakes that occurred during the 20th century since the great 1906 mw 8 8 colombia ecuador earthquake may have involved the simultaneous rupture of three to six asperities only one or two asperities were reactivated during the large seismic sequence of 1942 mw 7 8 1958 mw 7 7 1979 mw 8 2 and 1998 mw 7 1 the axis of the carnegie ridge which is entering the subduction zone south of the equator coincides well with the location of a 50 km wide creeping corridor that may have acted as persistent barrier to large seismic ruptures south of this creeping region a highly locked asperity is found right below la plata island while this asperity may have the potential to generate an mw 7 0 7 5 earthquake and a local tsunami until now it is unknown to have produced any similar events that region is characterized by the presence of slow slip events that may contribute significantly to reduce the long term moment deficit accumulated there and postpone the failure of that asperity at the actual accumulation rate a characteristic recurrence time for events such as those in 1942 1958 and 1979 is 140 30 yr 90 20 yr 153 80 yr respectively for the great 1906 event we find a recurrence time of at least 575 100 yr making the great 1906 earthquake a rare super cycle event

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

turbulent mixing induced by upgoing near inertial waves in the seasonal thermocline of the norwegian sea acoustic doppler current profiler and towed thermistor chain measurements made in the seasonal thermocline in the norwegian sea are examined for evidence that near inertial shear leads to small scale turbulent mixing as inferred from meter scale temperature fluctuations for the 1 day of data examined here spatial variability in shear is dominated by near inertial waves having upward energy propagation 30 m vertical wavelength and 5 to 10 km horizontal extent 20 km wavelength repeated samples of one of these waves had high froude number and enhanced small scale variability dominated by 20 m long waveforms which we conjecture are kelvin helmholtz instabilities arising from the near inertial shear

slip distribution of the 1992 landers earthquake and its implications for earthquake source mechanics we use near source 10 to 164 km displacement seismograms to image the slip distribution and rupture history of the 28 june 1992 mw 7 3 landers california earthquake aftershock seismograms from similar distances are modeled to find the velocity model and frequency range 0 05 to 0 25 hz over which theoretical green s functions are most accurate and the measure of fit is used as an upper bound on theoretical error in the mainshock inversion we represent the rupture surface with three planar segments divided into 3 by 3 km elements extending from the surface to 18 km depth and solve for the slip distribution and the rupture time model that minimizes misfit to both recorded seismograms and mapped surface displacement in a least squares sense we investigate two faulting models one with a uniformly short 3 sec rise time everywhere on the fault surface and the other with a variable rise time 2 to 6 sec we perform sensitivity tests using synthetic data from a hypothetical earthquake to evaluate model resolution and solution stability in the sensitivity tests both fault models recover similar slip and rupture features but neither is capable of imaging details of the rise time for the landers earthquake we find an average rupture velocity of 2 5 km sec and use this average for a starting model in a linearized inversion for rupture time in our solutions of slip amplitude distribution the southernmost johnson valley fault segment has 20 of the total seismic moment 6 to 8 1019 n m with small displacements near the hypocenter the homestead valley segment contributes half of the moment with the largest slip amplitudes 25 to 35 km northwest of the hypocenter at 4 to 12 km depth and the camp rock emerson segment contributes the remaining moment with the largest slip amplitude 35 to 50 km northwest of the hypocenter in the shallow crust 9 km there is some evidence that the rupture front is delayed as it encounters high slip regions suggesting that prior to the mainshock these areas were further from failure owing either to greater strength or lower prestress

the rupture process of the great 1979 colombia earthquake evidence for the asperity model we have determined the asperity distribution in the segment of the ecuador colombia subduction zone that was ruptured by the 1979 mw 8 2 and 1958 mw 7 7 earthquakes for the 1979 earthquake we are able to document directivity in the p wave source time functions and consequently have spatially located the moment release by combining results from both p wave and surface wave directivity we have defined three regions 1 from 0 to 56 km northeast of the epicenter with low moment release and a small seismic displacement 2 the asperity from 56 to 116 km northeast of the epicenter with most of the moment release and a displacement of 6 m and 3 a small displacement region from 116 to 180 240 km northeast of the epicenter thus the 1979 rupture zone is composed of an asperity 60 km in length bounded by two weak small displacement regions the displacement at the asperity is equal to the cumulative tectonic displacement between 1979 and 1906 the year of the previous great earthquake in this segment the 1958 earthquake is characterized by the rupture of a small asperity length scale approximately 25 km in the epicentral region the 1958 event continued to rupture past this small epicentral asperity and stopped near the epicenter of the following 1979 event this detailed study of the spatial variation in moment release offers strong support for the asperity model of large earthquake occurrence

near surface frontal zone trapping and deep upward propagation of internal wave energy in the japan east sea the full depth current structure in the japan east sea was investigated using direct velocity measurements performed with lowered and shipboard acoustic current doppler profilers rotary spectral analysis was used to investigate the three dimensional energy distribution as well as wave polarization with respect to vertical wavenumbers yielding information about the net energy propagation direction highly energetic near inertial downward propagating waves were found in localized patches along the southern edge of the subpolar front between 500 and 2500 m depth the basin average energy propagation was found to be upward with the maximum of relative difference between upward and downward propagating energy lying at about 1500 m depth this difference was most pronounced in the southeastern part of the basin

radar interferogram filtering for geophysical applications the use of sar interferometry is often impeded by decorrelation from thermal noise temporal change and baseline geometry power spectra of interferograms are typically the sum of a narrow band component combined with broad band noise we describe a new adaptive filtering algorithm that dramatically lowers phase noise improving both measurement accuracy and phase unwrapping while demonstrating graceful degradation in regions of pure noise the performance of the filter is demonstrated with sar data from the ers satellites over the jakobshavns glacier of greenland

inversion of strong ground motion and teleseismic waveform data for the fault rupture history of the 1979 imperial valley california earthquake a least squares point by point inversion of strong ground motion and teleseismic body waves is used to infer the fault rupture history of the 1979 imperial valley california earthquake the imperial fault is represented by a plane embedded in a half space where the elastic properties vary with depth the inversion yields both the spatial and temporal variations in dislocation on the fault plane for both right lateral strike slip and normal dip slip components of motion inversions are run for different fault dips and for both constant and variable rupture velocity models effects of different data sets are also investigated inversions are compared which use the strong ground motions alone the teleseismic body waves alone and simultaneously the strong ground motion and teleseismic records the inversions are stabilized by adding both smoothing and positivity constraints the moment is estimated to be 5 0 10 25 dyne cm and the fault dip 90 5 dislocation in the hypocentral region south of the united states mexican border is relatively small and almost dies out near the border dislocation then increases sharply north of the border to a maximum of about 2 m under interstate 8 dipslip motion is minor compared to strike slip motion and is concentrated in the sediments the best fitting constant rupture velocity is 80 per cent of the local shear wave velocity however there is a suggestion that the rupture front accelerated from the hypocenter northward the 1979 imperial valley earthquake can be characterized as a magnitude 5 earthquake at the hypocenter which then grew into or triggered a magnitude 6 earthquake north of the border

internal wave observations from the arctic environmental drifting buoy a free drifting buoy serving as an ice anchor and flotation sphere for a 125 m instrumented mooring line was deployed in the arctic pack ice by the r v polarstern in august 1987 at the northernmost point achieved by the arktis iv expedition current measurements were made from this arctic environmental drifting buoy aedb using a 150 khz acoustic doppler current profiler adcp attached to the mooring line at a depth of 16 m below the flotation sphere with the transducers facing downward velocity profiles spanning depths between 35 and 327 m with 15 m resolution were collected at half hour intervals over a period of 216 days while the buoy drifted from its starting point near 86 n 22 e to about 70 n 16 w the full experimental record was separated into three sections corresponding to periods of the drift spent in the nansen basin over the yermak plateau and in the greenland sea velocity time series and spectra were computed and results for the three analysis sections were compared spectra in the nansen basin were found to have energy levels significantly less than those typical for mid latitudes roughly one third of the canonical garrett munk gm level and a spectral slope between and 2 5 that was significantly flatter than that expected from the gm model between 83 n and 81 n as the buoy passed over the yermak plateau internal wave energy increased to levels comparable to gm isolated energetic near inertial wave packets with upward group velocity were observed in this portion of the record presumably generated by interaction of the barotropic tide with the bottom topography of the plateau estimates of the upward energy flux from these near inertial packets were comparable to the downward fluxes from typical surface sources interpretation of the greenland sea section was complicated by adcp sampling problems and a lack of argos fixes but the available data showed internal wave spectral levels that were intermediate between those of the nansen basin and yermak plateau and no evidence of upward propagating near inertial energy

geodetic data inversion using a bayesian information criterion for spatial distribution of fault slip summary we developed a new inversion method to reconstruct static images of seismic sources from geodetic data using akaike s bayesian information criterion abic coseismic surface displacements are generally related with a slip distribution on a fault surface by linear integral equations parametric expansion of the fault slip distribution by a finite number of known basis functions yields a set of observation equations expressed in a simple vector form incorporating prior constraints on the smoothness of slip distribution with the observation equations we construct a bayesian model with unknown hyperparameters the optimal values of the hyperparameters which control the structure of the bayesian model are objectively determined from observed data by using abic once the values of hyperparameters are determined we can use the maximum likelihood method to find the optimal distribution of fault slip we examined the validity of this method through a numerical experiment using theoretical data with random noise we analysed geodetic data associated with the 1946 nankaido earthquake ms 8 2 by using this method the result shows that the fault slip distribution of this earthquake has two main peaks of 4 and 6 m located off kii peninsula and muroto promontory these two high slip areas are clearly separated by a low slip zone extending along kii strait such a slip distribution corresponds with the fact that the rupture process of this earthquake in the western part is notably different from that in the eastern part

geodetic data inversion using abic to estimate slip history during one earthquake cycle with viscoelastic slip response functions summary we developed a new method of geodetic data inversion to estimate slip history at a plate interface by using akaike s bayesian information criterion abic in this method we considered the effects of viscoelastic stress relaxation in the asthenosphere which cannot be neglected to estimate slip history at a plate interface during one earthquake cycle we also introduced a proper formulation to incorporate two sorts of partially dependent prior information into observed data by bayes rule by applying the new inversion method to levelling data for 1893 1983 in shikoku southwestern japan we reconstructed the pattern of space time variation in slip motion during one earthquake cycle including the 1946 nankai earthquake at the interface between the eurasian and the philippine sea plates the result shows that a steady slip motion at a plate convergence rate 40 mm yr 1 proceeds in the shallow and the deep regions through the entire earthquake cycle in the intermediate depth range 10 30 km on the other hand an instantaneous slip of approximately 4 m occurs at the time of the nankai earthquake after that this portion keeps in stationary contact until the occurrence of the next nankai earthquake if we neglect the effects of viscoelastic stress relaxation the inversion analysis gives geophysically unrealistic results

near inertial current oscillations in the vicinity of the bering sea marginal ice zone near inertial current oscillations with 10 20 cm s amplitudes were prevalent over the bering sea shelf during november 1982 and again in march and april 1983 and also evident at reduced amplitudes during the intervening winter spectral peak frequencies were consistently within 1 of the local inertial frequency in contrast to the more superinertial 5 above frequencies commonly reported elsewhere a superinertial secondary energy peak at 1 038 was evident corresponding to the first mode wave amplitudes decreased with distance shoreward from the shelf break consistent with the effects of decreasing bottom depth and increasing mixed layer depth the oscillations were highly coherent over 100 km distances similar to observations reported by thomson and huggett 1981 for the british columbia coast whereas near inertial oscillations have been commonly reported to be uncoupled over much shorter 10 km distances in other regions vigorous near inertial ringing was associated with rapidly passing weather systems the decline in near inertial oscillation amplitudes during winter was partially due to a significant reduction in both cyclone frequency and occurrence of wind events causing clockwise wind shifts the decline was enhanced by reduction in the vertical stratification needed to support inertio gravity internal waves as the shelf waters apparently became mixed from top to bottom the loose mobile sea ice in the winter marginal ice zone miz did not appear to inhibit wind generation of the inertial oscillations the presence of sea ice appears in fact to have contributed to the spring increase of near inertial current amplitudes through restratification of the water column caused by melting ice our observations particularly the spatial coherency and spectral properties were generally consistent with kundu and thomson s 1985 model for inertio gravity waves generated in the wake of a translating weather front the half wavelength typical of these waves forced by transiting weather fronts on the bering shelf appears to be 150 km or approximately the width of the winter miz the associated near inertial currents are 180 out of phase with those a half wavelength away in the direction of phase propagation thus a storm passing perpendicular to the ice edge can excite waves at near inertial frequencies which compress deform and dilate the ice pack by up to a few percent of the miz width we suggest that this mechanism in conjunction with near inertial interfacial shear which can increase upward heat flux influences the width scale of the miz

source rupture process of the tecoman colima mexico earthquake of 22 january 2003 determined by joint inversion of teleseismic body wave and near source data the spatial and temporal slip distribution of the tecoman colima mexico earthquake is estimated from near source strong motion and teleseismic body wave data to perform a stable inversion we applied smoothing constraints and determined their optimal relative weights on the observed data using an optimized akaike s bayesian information criterion abic the source parameters are as follows strike dip slip 300 20 93 seismic moment m 2 3 1020 n m source duration 30 sec along strike distance 35 km along dip distance 70 km we found that the rupture process can be divided into three stages the rupture nucleated near the hypocenter stage i then it broke the first asperity centering about 15 km southwest from the epicenter stage ii and the rupture propagated to the northeast and the second asperity was broken stage iii we also estimated the shear stress change due to the rupture process of the mainshock on and around the major fault zone it appears that one cluster of aftershocks for the first 5 days which took place in and adjacent to the zones of stress increased due to the fault rupture during the mainshock but overall correlation between the aftershock location and the stress pattern is not clear manuscript received 14 may 2003

a method for the joint inversion of geodetic and seismic waveform data using abic application to the 1997 manyi tibet earthquake geodetic imaging data and seismicwaveformdata have complementary strengthswhen considering the modelling of earthquakes the former particularly modern space geodetic techniques such as interferometric synthetic aperture radar insar permit high spatial density of observation and thus fine resolution of the spatial pattern of fault slip the latter provide precise and accurate timing information and thus the ability to resolve how that fault slip varies over time in order to harness these complementary strengths we propose a method through which the two data types can be combined in a joint inverse model for the evolution of slip on a specified fault geometry we present here a derivation of akaike s bayesian information criterion abic for the joint inversion of multiple data sets that explicitly deals with the problem of objectively estimating the relative weighting between data sets as well as the optimal influence of model smoothness constraints in space and time we demonstrate our abic inversion scheme by inverting insar displacements and teleseismic waveform data for the 1997 manyi tibet earthquake we test using a simplified fault geometry three cases insar data inverted alone vertical component teleseismic broad band waveform data inverted alone and a joint inversion of both data sets the insar only model and seismic only model differ significantly in the distribution of slip on the fault plane that they predict the joint inversion model however has not only a similar distribution of slip and fit to the insar data in the insar only model suggesting that those data provide the stronger control on the pattern of slip but is also able to fit the seismic data at a minimal degradation of fit when compared with the seismic only model the rupture history of the preferred joint inversion model indicates bilateral rupture for the first 20 s of the earthquake followed by a further 25 s of westward unilateral rupture afterwards with slip peaking at 7m in the upper 6 km of the fault this joint inversion approach is thus shown to be a viable method for the study of large shallow continental earthquakes and may be of particular benefit in cases where near field seismic observations are not available the authors 2014 published by oxford university press on behalf of the royal astronomical society