the role of horizontal divergence in submesoscale frontogenesis abstractoceanic surface submesoscale currents are characterized by anisotropic fronts and filaments with widths from 100 m to a few kilometers an o 1 rossby number and large magnitudes of latera

time scales of submesoscale flow inferred from a mooring array abstractwhile the distribution of kinetic energy across spatial scales in the submesoscale range 1 100 km has been estimated from observations the associated time scales are largely unconstraine

the location and source parameters of the lompoc california earthquake of 4 november 1927 in this paper we address the relocation magnitudes and the style of faulting of the lompoc earthquake from a sparse assortment of teleseismic and regional seismograms the highest quality teleseismic waveform data come from a station at de bilt netherlands that remains in operation thus recordings of numerous modern events in central coastal california i e the 1969 santa lucia banks 1983 coalinga 1978 santa barbara and 1989 loma prieta earthquakes have been used for comparison with the 1927 records location constraints for the lompoc event were established from the de bilt recording by comparing s p and sss s waveform matches against the above master events to avoid the effect of unknown clock errors on locations that use absolute times these same seismograms were modeled to estimate the depth faulting parameters and source strength a similar approach using observational comparisons and numerical modeling was applied to the regional waveform data obtained from the stations at berkeley tucson and pasadena our results indicate a north northwesterly striking reverse event located about 40 km west of point conception which is in excellent agreement with the recent tsunami modeling results by satake and somerville 1992 this location is 25 km south of that proposed by hanks 1979 and well within his error bars we obtain a body wave moment of 1 10 26 dyne cm a trapezoidal time history of 2 2 2 sec and a source depth of 10 km the weak beginning of the pnl wavetrain at berkeley indicates some source complexity which is characteristic of many large events the fault parameters are strike n20 w dip 66 ne and rake 95 most seismicity catalogs report a m s 7 3 for this event after gutenberg and richter 1956 but this was a long period body wave magnitude and not a surface wave result their original worksheets indicate a smaller ms 7 0 the body waves of the loma prieta event m s 7 1 appear distinctly larger than those of the lompoc event at de bilt in agreement with our lower estimate of source strength

broadband modelling along a regional shield path harvard recording of the saguenay earthquake summary the saguenay earthquake 1988 november 25 is one of the first large shield type events recorded by a broadband high dynamic range instrument the streckeisen system installed at harvard station hrv the event is sufficiently large to be well recorded teleseismically and thus the source characteristics can be determined by independent means and considered known this allows a detailed study of the propagational effects along this path at an epicentral distance of 625 km where the strengths of the surface waves can be compared with the crustal body phases broadband modelling using standard analytical techniques and flat layered models works amazingly well over the period range of 0 5 20 s a detailed strategy for modelling broadband regional phases is given in terms of a decomposition of the vertical and radial seismograms into three segments pnl containing pn ppn spn pmp p coupled pl waves snl containing sn ssn sms etc and the fundamental rayleigh waves information about the upper crust is obtained from the fundamental rayleigh waves while crustal thickness and velocity gradients in the mantle are obtained from pnl and snl this particular crustal model has a thickness of 35 km with a sharp moho and a substantial gradient in the top 20 km of the mantle 0 01 km s 1 per km for both p and s velocities the mantle velocities 8 2 and 4 55 km s 1 are slower than expected for a shield environment attenuation is not required for waveform modelling or for absolute amplitude estimation

genesis of the jurassic dongfengbeishan porphyry mo deposit in eastern yanbian ne china inferred from molybdenite re os and zircon u pb ages and whole rock elemental and zircon hf isotopic compositions abstract the dongfengbeishan porphyry mo deposit is located to the southeast of the lesser xing an range zhangguangcai range metallogenic belt in ne china la icp ms zircon u pb dating of the beishan monzogranite yields an age of 194 75 0 81 ma five molybdenite samples define a re os isochron age of 194 0 2 0 ma suggesting that mineralization was associated with emplacement of the beishan monzogranitic pluton monzogranite samples are classified as high k calc alkaline and are relatively enriched in light rare earth elements depleted in heavy rare earth elements nb ba p sr ti and zr and yield negative eu anomalies these characteristics are interpreted to record fractional crystallization of the parental magmas zircon ehf t values for beishan monzogranite samples range from 8 2 to 15 9 and two stage model ages tdm2 range from 217 to 711 ma indicating that the parental magma was produced during partial melting of juvenile lower crust combined with previous studies our data suggest that the dongfengbeishan porphyry mo deposit was associated with westward subduction of the paleo pacific plate in the early jurassic

wavenumber spectrum in the gulf stream from shipboard adcp observations and comparison with altimetry measurements the wavenumber spectra for velocity and temperature in the gulf stream region are calculated from a decade 1994 2004 of shipboard acoustic doppler current profiler adcp measurements taken as part of the oleander project the velocity and temperature spectra have comparable magnitude in terms of the kinetic and potential energy and both indicate a k 23 slope in the mesoscales in contrast the corresponding velocity spectrum determined from satellite altimetry sea surface heights yields a significantly higher energy level and a k 22 slope the discrepancy between altimeter derived and directly measured velocity spectra suggests that altimetric velocity probably is contaminated by noise in sea surface height measurement also the k 23 slope which appears to be in agreement with two dimensional quasigeostrophic turbulence theory does not support the contemporary surface quasigeostrophic theory these results highlight large gaps in the current understanding of the nature of surface geostrophic turbulence

geochronology and zircon hf isotope geochemistry of granites in the giant chalukou mo deposit ne china implications for tectonic setting abstract in this contribution the largest porphyry mo deposit in ne china chalukou is selected to provide insights into the tectonic evolution of ne china the deposit was considered to be rift related or climax type porphyry mo deposit developed in an extensional setting while other researchers attributed its formation to the subduction of the paleo pacific ocean in view of different granite petrogenesis between rift type and subduction type porphyry mo deposits geochronological and zircon lu hf isotope studies have been carried out on granitic rocks associated with the chalukou deposit zircon grains from the ore host monzogranite and ore causative granite porphyry yield weighted mean 206pb 238u ages of 166 2 ma and 152 2 ma with molybdenite samples yielding a re os isochron age of 150 2 ma indicating a jurassic age for both granitic intrusion and mo mineralization zircon ehf t values of monzogranite and granite porphyry range from 0 9 to 3 0 and from 1 4 to 0 5 respectively when integrated with published zircon lu hf isotopic data our data suggest that the barren granites both pre and post ore were mainly derived from mantle derived juvenile rocks whereas the syn ore granite requires additional involvement of old continental crust thus a contribution of continental crust to mo mineralization is suggested the petrogenesis and geochemical data reveal that the chalukou deposit is a subduction related porphyry mo deposits and not rift related integrated evidence links its formation to the southeastward subduction of the mongol okhotsk ocean instead of the westward subduction of the paleo pacific ocean

characterizing the transition from balanced to unbalanced motions in the southern california current author s chereskin teresa k rocha cesar b gille sarah t menemenlis dimitris passaro marcello

rupture process of the 1987 superstition hills earthquake from the inversion of strong motion data a pair of significant earthquakes occurred on conjugate faults in the western imperial valley involving the through going superstition hills fault and the elmore ranch cross fault the first event was located on the elmore ranch fault m s 6 2 and the larger event on the superstition hills fault m s 6 6 the latter event is seen as a doublet teleseismically with the amplitudes in the ratio of 1 2 and delayed by about 8 sec this 8 sec delay is also seen in about a dozen strong motion records these strong motion records are used in a constrained least squares inversion scheme to determine the distribution of slip on a 2 d fault upon closer examination the first of the doublets was found to be itself complex requiring two episodes of slip thus the rupture model was allowed to have three separate subevents treated as separate ruptures with independent locations and start times the best fits were obtained when all three events initiated at the northwestern end of the fault near the intersection of the cross fault their respective delays are 2 1 and 8 6 sec relative to the first subevent and their moments are 0 4 0 9 and 3 5 10 25 dyne cm which is about half of that seen teleseismically this slip distribution suggests multi rupturing of a single asperity with stress drops of 60 200 and 15 bars respectively the first two subevents were confined to a small area around the epicenter while the third propagated 18 km southwestward compatible with the teleseismic and afterslip observations

the role of mixed layer instabilities in submesoscale turbulence upper ocean turbulence at scales smaller than the mesoscale is believed to exchange surface and thermocline waters which plays an important role in both physical and biogeochemical budgets but what energizes this submesoscale turbulence remains a topic of debate two mechanisms have been proposed mesoscale driven surface frontogenesis and baroclinic mixed layer instabilities the goal here is to understand the differences between the dynamics of these two mechanisms using a simple quasi geostrophic model the essence of mesoscale driven surface frontogenesis is captured by the well known surface quasi geostrophic model which describes the sharpening of surface buoyancy gradients and the subsequent breakup in secondary roll up instabilities we formulate a similarly archetypical eady like model of submesoscale turbulence induced by mixed layer instabilities the model captures the scale and structure of this baroclinic instability in the mixed layer a wide range of scales are energized through a turbulent inverse cascade of kinetic energy that is fuelled by the submesoscale mixed layer instability major differences to mesoscale driven surface frontogenesis are that mixed layer instabilities energize the entire depth of the mixed layer and produce larger vertical velocities the distribution of energy across scales and in the vertical produced by our simple model of mixed layer instabilities compares favourably to observations of energetic wintertime submesoscale flows suggesting that it captures the leading order balanced dynamics of these flows the dynamics described here in an oceanographic context have potential applications to other geophysical fluids with layers of different stratifications

comments on the lompoc california earthquake november 4 1927 m 7 3 and its aftershocks by thomas c hanks

broadband study of the 1989 loma prieta earthquake we determined the source characteristics of the oct 18 1989 loma prieta california earthquake using teleseismic data the solution from body waves gives a mechanism with dip 70 rake 138 and strike 128 and a seismic moment of 3 10 26 dyne cm m w 6 9 this solution is similar to those obtained from long period rayleigh and love waves p nl waves and first motion data the body wave form suggests a depth of about 15 km the effective duration of the source is 6 sec which suggests a fault length of 30 km and 15 km for bilateral and unilateral faulting respectively considering the extent of the aftershock area we used 35 km as an estimate of the total rupture length the strike slip and the thrust components of the coseismic slip are 177 and 159 cm respectively the large thrust component raises an important question regarding the recurrence pattern if the loma prieta earthquake is a characteristic earthquake with a recurrence interval of about 100 years the 159 cm displacement implies a long term uplift rate of about 1 cm year which appears too large for this region three hypotheses for reconciling this apparent conflict are 1 the geometry of plate motion along the santa cruz mountain segment changes over a time scale of several thousand years so that the coseismic displacement has not accumulated enough to produce high topographic relief 2 the coseismic shp direction varies from event to event 3 the slip plane of the 1989 loma prieta earthquake is different from the major boundary between the pacific and the north american plates if this is the case the loma prieta earthquake is a rather rare non characteristic event the surface slip of about l m for the 1906 san francisco earthquake is one of the key data in long term forecasting no surface slip was observed for the 1989 loma prieta earthquake even if the horizontal slip at depth is as large as 1 8 m this points to a risk of relying too heavily on surface observations for long term seismic risk analysis

seasonality of submesoscale flows in the ocean surface boundary layer a signature of submesoscale flows in the upper ocean is skewness in the distribution of relative vorticity expected to result for high rossby number flows such skewness has implications for mixing dissipation and stratification within the upper ocean an array of moorings deployed in the northeast atlantic for one year as part of the osmosis experiment reveals that relative vorticity is positively skewed during winter even though the scale of the rossby number is less than 0 5 furthermore this skewness is reduced to zero during spring and autumn there is also evidence of modest seasonal variations in the gradient rossby number the proposed mechanism by which relative vorticity is skewed is that the ratio of lateral to vertical buoyancy gradients as summarized by the inverse gradient richardson number restricts its range during winter but less so at other times of the year these results support recent observations and model simulations suggesting the upper ocean is host to a seasonal cycle in submesoscale turbulence

ocean convergence and the dispersion of flotsam floating oil plastics and marine organisms are continually redistributed by ocean surface currents prediction of their resulting distribution on the surface is a fundamental long standing and practically important problem the dominant paradigm is dispersion within the dynamical context of a nondivergent flow objects initially close together will on average spread apart but the area of surface patches of material does not change although this paradigm is likely valid at mesoscales larger than 100 km in horizontal scale recent theoretical studies of submesoscales less than 10 km predict strong surface convergences and downwelling associated with horizontal density fronts and cyclonic vortices here we show that such structures can dramatically concentrate floating material more than half of an array of 200 surface drifters covering 20 20 km2 converged into a 60 60 m region within a week a factor of more than 105 decrease in area before slowly dispersing as predicted the convergence occurred at density fronts and with cyclonic vorticity a zipperlike structure may play an important role cyclonic vorticity and vertical velocity reached 0 001 s 1 and 0 01 ms 1 respectively which is much larger than usually inferred this suggests a paradigm in which nearby objects form submesoscale clusters and these clusters then spread apart together these effects set both the overall extent and the finescale texture of a patch of floating material material concentrated at submesoscale convergences can create unique communities of organisms amplify impacts of toxic material and create opportunities to more efficiently recover such material

determining source parameters of moderate size earthquakes from regional waveforms abstract waveform modeling of the teleseismic long period body wave phases of shallow earthquakes has proven quite effective in determining source parameters for events of magnitude larger than six unfortunately these teleseismic phases become too weak for smaller events and regional data must be used which are generally much more complicated this is because the crust mantle system acts as a leaky waveguide and a large number of rays are required to model the observations in this report we review a procedure for the systematic determination of source parameters from regional body waves a least squares inversion technique is used which is based on a cross correlation of the data and a synthetic seismogram the synthetic waveforms are a linear combination of those for the three fundamental types of fault a set of profiles of the synthetic waveforms is presented although the synthetic waveforms are generated for a model developed for the western united states this model seems to be adequate for most continental regions the inversion is parameterized in terms of fault strike dip and rake these parameters are relatively insensitive to small changes in crustal structure several examples are presented

recurrence models and parkfield california earthquakes main shocks of the earthquake sequences that occurred on the parkfield section of the san andreas fault in central california in 1922 1934 and 1966 are characterized by southeast rupture expansion over the same 20 to 30 km long section of the fault whereas the seismic moments for the 1922 and 1934 events are identical to within a precision of 10 the seismic moment for 1966 is 20 greater than for the earlier events to within a precision of 20 the parkfield area seismicity in general seems well described by a recurring moderate size characteristic earthquake repeating the same epicenter magnitude seismic moment rupture area and southeast direction of rupture expansion an unexplained 10 year advance of the 1934 event is the only discrepancy in the hypothesis that the parkfield earthquakes in 1857 1881 1901 1922 1934 and 1966 represent a strictly periodic process assuming the strictly periodic model and the absence since 1966 of the perturbations hypothesized for the 1922 to 1934 period the next characteristic parkfield earthquake should occur between 1983 and 1993

magnitudes of large shallow earthquakes from 1904 to 1980 abstract in order to obtain a uniform magnitude catalogue surface wave magnitudes ms and broad band body wave magnitudes mb have been determined for large shallow earthquakes from 1904 to 1980 in making the catalogue homogeneous the author consistently adheres to the original definitions of ms and mb given by gutenberg 1945 and gutenberg and richter 1956 the determinations of ms and mb are all based on the amplitude and period data listed in gutenberg and richter s unpublished notes bulletins from stations worldwide and other basic information mb is measured on broad band instruments in periods of 8 s consistency of the magnitude determinations from these different sources is carefully checked in detail more than 900 shallow shocks of magnitude 7 and over are catalogued the meaning of the magnitude scales in various catalogues is examined in terms of ms and mb most of the magnitudes listed by gutenberg and richter 1954 in their seismicity of the earth are basically ms for large shocks shallower than 40 km but are basically mb for large shocks at depths of 40 60 km the surface wave magnitudes given by earthquake data reports are higher than ms by 0 2 unit whether the combined horizontal amplitude or the vertical amplitude is used mb and the currently used 1 s body wave magnitude are measured at different periods and should not be directly compared

geodetic measurement of tectonic deformation in the santa maria fold and thrust belt california we have analyzed geodetic observations to resolve tectonic deformation across the santa maria fold and thrust belt northwest of santa barbara california the geodetic network forms a braced quadrilateral with 40 km sides whose southwest corner is the vandenberg very long baseline interferometry station the data include 1 historical triangulation from the 1880s 1920s and 1950s 2 electronic distance measurement trilateration from 1971 and 1985 and 3 global positioning system observations from 1986 and 1987 we combine the three different types of data to estimate two dimensional station positions and strain rate parameters simultaneously using a model which constrains the relative velocity field to be linear in space and constant in time we find significant strain rates the maximum compressive strain is oriented n17 e 5 e and the compressive strain rate in this direction is 0 13 0 03 strain yr under the assumption that the unresolved rotational component of the velocity field is zero we estimate that the integrated rate of deformation across the basin is 7 1 mm yr oriented at n03 e 13 this vector can be decomposed into 6 2 mm yr of crustal shortening on the general structural trend of n30 e and 3 1 mm yr of right lateral shear across this axis on the basis of these values and earthquake focal mechanisms in the area we infer that the deformation occurs on northwest trending folds and thrusts within the belt these results are consistent with the rate and direction of deformation across the central california coast ranges inferred by balancing pacific north america plate motion against san andreas slip and basin and range extension they imply that the santa maria fold and thrust belt is the primary active element in transforming motion from the coast ranges to the western transverse ranges and the santa barbara channel

parameterization of mixed layer eddies part i theory and diagnosis ageostrophic baroclinic instabilities develop within the surface mixed layer of the ocean at horizontal fronts and efficiently restratify the upper ocean in this paper a parameterization for the restratification driven by finite amplitude baroclinic instabilities of the mixed layer is proposed in terms of an overturning streamfunction that tilts isopycnals from the vertical to the horizontal the streamfunction is proportional to the product of the horizontal density gradient the mixed layer depth squared and the inertial period hence restratification proceeds faster at strong fronts in deep mixed layers with a weak latitude dependence in this paper the parameterization is theoretically motivated confirmed to perform well for a wide range of mixed layer depths rotation rates and vertical and horizontal stratifications it is shown to be superior to alternative extant parameterizations of baroclinic instability for the problem of mixed layer restratification two companion papers discuss the numerical implementation and the climate impacts of this parameterization

interpreting energy and tracer spectra of upper ocean turbulence in the submesoscale range 1 200 km submesoscale 1 200km wavenumber spectra of kinetic and potential energy and tracer variance are obtained from in situ observations in the gulf stream region and in the eastern subtropical north pacific in the gulf stream region steep kinetic energy spectra at scales between 200 and 20km are consistent with predictions of interior quasigeostrophic turbulence theory both in the mixed layer and in the thermocline at scales below 20km the spectra flatten out consistent with a growing contribution of internal wave energy at small scales in the subtropical north pacific theenergyspectraareflatterand inconsistentwith predictionsofinteriorquasigeostrophic turbulence theory the observed spectra and their dependence on depth are also inconsistent with predictions of surface quasigeostrophic turbulencetheoryfortheobservedoceanstratification itappearsthatunbalancedmotions most likely internal tides at large scales and the internal wave continuum at small scales dominate the energy spectrum throughout the submesoscale range spectra of temperature variance along density surfaces which are not affected by internal tides are also inconsistent with predictions of geostrophic turbulence theories reasons for this inconsistency could be the injection of energy in the submesoscale range by small scale baroclinic instabilities or modifications of the spectra by coupling between surface and interior dynamics or by ageostrophic frontal effects

fluid inclusions and h o s pb isotope systematics of the chalukou giant porphyry mo deposit heilongjiang province china abstract the chalukou giant porphyry mo deposit located in the northern great xing an range is the largest mo deposit in the xing an mongolia orogenic belt this deposit s ore bodies are mainly hosted in an intermediate felsic complex and jurassic volcanic sedimentary rocks of which late jurassic granite porphyry quartz porphyry and fine grained granite are closely associated with the mo mineralization three types of fluid inclusions fis are present in the quartz associated with oxide and sulphide minerals i e liquid rich two phase gas rich two phase and daughter mineral bearing multiphase fis the fis in the quartz phenocrysts of the granite porphyry contain liquid rich two phase gas rich two phase and daughter mineral bearing multiphase fis the homogenization temperatures vary from 230 c to 440 c and 470 c to 510 c and their salinities vary from 0 7 to 53 7 nacl eq and 6 2 to 61 3 nacl eq respectively the fis of k feldspar quartz magnetite veins of the early stage are composed of liquid rich two phase gas rich two phase and daughter mineral bearing multiphase fis with homogenization temperatures and salinities of 320 c to 440 c and 4 2 to 52 3 nacl eq respectively the fis of quartz molybdenite veins and breccia of the middle stage are composed of liquid rich two phase gas rich two phase and daughter mineral bearing multiphase fis with homogenization temperatures and salinities of 260 c to 410 c and 0 4 to 52 3 nacl eq respectively fis of quartz fluorite galena sphalerite veins of the late stage are liquid rich two phase fis with homogenization temperatures and salinities of 170 c to 320 c and 0 5 to 11 1 nacl eq respectively the ore forming fluids of the chalukou deposit are characterised by high temperature high salinity and high oxygen fugacity belonging to an f rich h 2 o nacl co 2 system the 18 o w values vary from 4 5 to 3 2 and the d w values vary from 138 to 122 indicating that the ore forming fluids were a mixture of magmatic and meteoric water the 34 s values range from 1 9 to 3 6 with an average of 1 6 the 206 pb 204 pb 207 pb 204 pb and 208 pb 204 pb values of the metallic minerals are in the ranges of 18 269 18 501 15 524 15 567 and 38 079 38 264 respectively both the s and pb isotopic systems indicate that the ore metals and fluids came primarily from a deep seated magma source from the juvenile lower crust the mo mineralization in the chalukou deposit occurred at a depth of 0 5 to 1 3 km and multiple stages of phase separation or immiscibility of ore forming fluid was critical for the formation of the chalukou deposit

seismic characteristics of earthquakes along the offshore extension of the western transverse ranges california the short and long period body waves of five moderate m l 5 to 6 earthquakes that took place in the nearshore region of southcentral california between 1969 and 1981 are modeled to obtain the source parameters both regional pnl waveforms and teleseismic p waveforms are used in this analysis four of the events are thrust earthquakes with strikes that rotate southwestward as the epicenters move southward the fifth is a strike slip event occurring on a fault subparallel to the san andreas fault the focal mechanisms for all five events are consistent with known faults in the source localities and suggest that the regional stress field is compressional in a north south direction at least three events have complex source time histories suggesting that complex sources are common even for events of this size the most exotic event started with a low stress drop subevent ruptured bilaterally and concluded with strong asperity ruptures at each end since pnl waveforms for thrust events are particularly sensitive to crustal thickness regionalized crustal models were developed the crustal thickness appears to increase southward but may be a function of the distance of the event from shore rather than of latitude basin and range paths yield the thinnest crustal models while paths crossing the colorado plateau and rockies yield the thickest we also examined amplitude variations with station and path in general the amplitudes seem to be controlled by the station site rather than the path

re os isotopic dating of molybdenite separates from chalukou porphyry mo polymetallic deposit in heilongjiang province located at the northernmost corner of the deerbugan metallogenic belt and in the northeastern part of the mongolian hinggan amalgamated massif the newly found chalukou ore deposit is the largest molybdenum polymetallic deposit ever discovered in china it contains 1 34 mt of mo metal 0 37 mt of pb zn and 4 200 t of ag as a part of the evaluation project of the molybdenum deposit mineral exploration around chalukou is still underway during the mesozoic yanshanian orogeny intense extensional tectonic and igneous activities resulted in the formation of large scale acid volcanic rocks and granitoid intrusions at chalukou and its neighboring areas the chalukou granite porphyry and quartz porphyry stocks were emplaced in the jurassic volcano sedimentary sequence controlled by ne and nw trending fault zones rock forming minerals of the two porphyry stocks are mainly quartz microcline microperthite and plagioclase associated with minor biotite and sericite accessory minerals include magnetite apatite zircon sphene and allanite molybdenum mineralization occurs within the chalukou porphyry stocks and volcanic rocks as stockworks veins veinlets and disseminated blocks the molybdenum ore consists of pyrite chalcopyrite molybdenite sphalerite galena magnetite pyrrhotite k feldspar fluorite quartz sericite and chlorite as the most important economic molybdenum mineral molybdenite occurs in the impregnation radioflake thin film aggregated flake and veinlet forms re os isotopic dating of eight molybdenite separates from the main ore body yielded an isochron age of 146 96 0 79 ma and model ages ranging from 146 2 ma to 149 1 ma with an average value of 147 4 ma the re os isochron age is in agreement with field geological evidence and the molybdenite is coexistent with chalcopyrite and pyrite suggesting that the re os isochron age represents the ore forming time of the porphyry mo mineralization in the chalukou ore deposit and its neighboring areas combined with field geological observations and petrological evidence the authors hold that the ore forming materials might have been derived from a mixed source of depleted mantle and crustal derived magma or fluids the re os isochron age of the molybdenite separates at chalukou indicates that late jurassic intraplate granitoid magmatism and relevant molybdenum polymetallic mineralization in the northernmost part of the da hinggan mountains were active after the latest paleozoic collision between the siberian plate and the mongolian hinggan amalgamated massif therefore the chalukou district and its neighboring areas have a great potential for mesozoic yanshanian granitoid porphyry molybdenum polymetallic deposits

the 25 november 1988 saguenay quebec earthquake source parameters and the attenuation of strong ground motion the saguenay earthquake of 25 november 1988 occurred close to the southern margin of the saguenay graben in southern quebec it was caused by almost purely dip slip faulting centered at a depth of 26 km with a p axis oriented northeast southwest this faulting mechanism is similar to those of the larger historical earthquakes in eastern north america but the focal depth is substantially greater than all but one of these events the seismic moment estimated from regional pni waves and teleseismic long period body waves is 5 10 24 dyne cm corresponding to a moment magnitude of 5 8 the source duration of the earthquake is estimated to be 1 8 sec corresponding to a stress drop of 160 bars which is not significantly higher than the average stress drop of 120 bars estimated from previous large earthquakes in eastern north america in order to simultaneously match the recorded ground motion amplitudes of strong motion acceleration strong motion velocity and teleseismic short period and long period body waves it is necessary to use a source function having a complex shape that implies the presence of asperities and larger local stress drops the large set of strong motion recordings of the saguenay earthquake has been used to validate a procedure for estimating strong ground motion attenuation based on a simple wave propagation model the most important feature of the recorded strong motions is that their peak amplitudes do not decay significantly with distance inside 120 km but then decay abruptly beyond 120 km profiles of recorded accelerograms with absolute times indicate that at distances beyond 64 km the peak ground motions are due to strong postcritical reflections from velocity gradients in the lower crust the principal shear wave arrivals and the variation of their peak amplitudes with distance were reproduced in synthetic seismograms generated using a regional crustal structure model the critical distances for the postcritical reflections were short because of the deep focal depth of the event causing the elevation of ground motion amplitudes out to 120 km similar studies of earthquakes in other regions of eastern north america indicate that the strength of the postcritical reflections and the distance ranges over which they are dominant are controlled by the focal depth and crustal structure regional variations in crustal structure thus give rise to predictable regional variations in strong ground motion attenuation

seasonality in transition scale from balanced to unbalanced motions in the world ocean abstractthe transition scale lt from balanced geostrophic motions to unbalanced wave motions including near inertial flows internal tides and inertia gravity wave continuum is explored using the output from a global 1 48 horizontal resolution massachusetts institute of technology general circulation model mitgcm simulation defined as the wavelength with equal balanced and unbalanced motion kinetic energy ke spectral density lt is detected to be geographically highly inhomogeneous it falls below 40 km in the western boundary current and antarctic circumpolar current regions increases to 40 100 km in the interior subtropical and subpolar gyres and exceeds in general 200 km in the tropical oceans with the exception of the pacific and indian sectors of the southern ocean the seasonal ke fluctuations of the surface balanced and unbalanced motions are out of phase because of the occurrence of mixed layer instability in winter and trapping of unbalanced motion ke in shallow mixed layer in summe

reply to w gawthrop s comments on the lompoc california earthquake november 4 1927 m 7 3 and its aftershocks

ore genesis and hydrothermal evolution of the baiyinnuo er zinc lead skarn deposit northeast china evidence from isotopes s pb and fluid inclusions the baiyinnuo er zinc lead deposit 32 74 mt at 5 44 zn 2 02 pb and 31 36 g t ag located in the south segment of the great xing an range is the largest zn pb deposit in northern china skarn and orebodies mainly occur between the different units of the huanggangliang formation or within the contact zone between the intrusions and permian marble several phases of igneous rocks exposed within the mining areas and among them the yanshanian plutonic rocks which intruded into limestone of the early permian huanggangliang formation are interpreted to be the source of ore since their pb isotope compositions 206pb 204pb 18 25 18 35 207pb 204pb 15 50 15 56 and 208pb 204pb 38 14 38 32 are highly consistent with the sulfides including sphalerite galena and chalcopyrite 206pb 204pb 18 23 18 37 207pb 204pb 15 47 15 62 and 208pb 204pb 37 93 38 44 sulfur isotope values of the sulfides give a narrow 34s interval of 6 1 to 4 6 mean 5 4 n 15 suggesting the ore forming fluid is of magmatic origin three main paragenetic stages of skarn formation and ore deposition have been recognized based on petrographic observation which are the preore stage garnet clinpyroxene wollastonite magnetite sulfides the synore stage sulfides epidote quartz calcite garnet and the postore stage calcite chlorite quartz fluorite several fluid evolution episodes can be inferred from microthermometric results at the baiyinnuo er zn pb deposit 1 immiscibility preore stage coexistence of halite bearing brine inclusions s1 type 44 wt nacl equiv and vapor rich fluid inclusions v type sharing the same homogenization temperatures 470 c confirms that fluid unmixing occurred under lithostatic pressures of 400 bars 1 5 km and the brine is considered to account for most prograde skarn minerals e g clinopyroxene 2 overpressure trapping preore stage brine inclusions homogenized by halite dissolution s2 type postdated the immiscible assemblages this type of inclusions is characterized by high but variable minimum trapping pressures 150 3 000 bars relative to s1 type inclusions and can be explained as a result of entrapment under overpressuring condition 3 boiling the presence of both vapor and liquid inclusions i e v and l type in the same assemblages within synore stage quartz calcite and sphalerite indicates the occurrence of fluid boiling 350 c at hydrostatic pressures of 150 bars and depth of 1 5 km which resulted in large scale mineralization in the baiyinnuo er zn pb deposit 4 mixing with external fluids fluid inclusions scattered within postore stage calcite or secondary trails in synore stage minerals show low homogenization temperatures 260 c and both decreasing for l type and increasing for cacl2 bearing inclusions i e lc type trends for salinities as homogenization temperatures decrease implying addition of both meteoric water low temperature low salinity and basinal brines low temperature ca rich respectively systematic fluid inclusion studies also indicate that the mineralization related fluid is of magmatic origin prograde minerals formed during the preore stage fluid immiscibility while sulfides deposition occurred during the synore stage fluid boiling mixing with external fluids began as the hydrothermal system cooled to 300 c when the main metal precipitation process had ended

zircon u pb and molybdenite re os dating of the chalukou porphyry mo deposit in the northern great xing an range china and its geological significance abstract the newly discovered chalukou giant porphyry mo deposit located in the northern great xing an range is the biggest mo deposit in northeast china the chalukou mo deposit occurs in an intermediate acid complex and jurassic volcano sedimentary rocks of which granite porphyry quartz porphyry and fine grained granite are closely associated with mo mineralization however the ages of the igneous rocks and mo mineralization are poorly constrained in this paper we report precise in situ la icp ms zircon u pb dates for the monzogranite granite porphyry quartz porphyry fine grained granite rhyolite porphyry diorite porphyry and andesite porphyry in the chalukou deposit corresponding with ages of 162 2 ma 149 5 ma 148 2 ma 148 1 ma 137 3 ma 133 2 ma and 132 2 ma respectively analyses of six molybdenite samples yielded a re os isochron age of 148 1 ma these data indicate that the sequence of the magmatic activity in the chalukou deposit ranges from jurassic volcano sedimentary rocks and monzogranite through late jurassic granite porphyry quartz porphyry and fine grained granite to early cretaceous rhyolite porphyry diorite porphyry and andesite porphyry the chalukou porphyry mo deposit was formed in the late jurassic and occurred in a transitional tectonic setting from compression to extension caused by subduction of the paleo pacific oceanic plate

open ocean submesoscale motions a full seasonal cycle of mixed layer instabilities from gliders abstractthe importance of submesoscale instabilities particularly mixed layer baroclinic instability and symmetric instability on upper ocean mixing and energetics is well documented in regions of strong persistent fronts such as the kuroshio and the gulf stream less attention has been devoted to studying submesoscale flows in the open ocean far from long term mean geostrophic fronts characteristic of a large proportion of the global ocean this study presents a year long submesoscale resolving time series of near surface buoyancy gradients potential vorticity and instability characteristics collected by ocean gliders that provides insight into open ocean submesoscale dynamics over a full annual cycle the gliders continuously sampled a 225 km2 region in the subtropical northeast atlantic measuring temperature salinity and pressure along 292 short 20 km hydrographic sections glider observations show a seasonal cycle in near surface stratification throughout the fall september november

mixed layer instabilities and restratification abstract the restratification of the oceanic surface mixed layer that results from lateral gradients in the surface density field is studied the lateral gradients are shown to be unstable to ageostrophic baroclinic instabilities and slump from the horizontal to the vertical these instabilities which are referred to as mixed layer instabilities mlis differ from instabilities in the ocean interior because of the weak surface stratification spatial scales are o 1 10 km and growth time scales are on the order of a day linear stability analysis and fully nonlinear simulations are used to study mlis and their impact on mixed layer restratification the main result is that mlis are a leading order process in the ml heat budget acting to constantly restratify the surface ocean climate and regional ocean models do not resolve the scales associated with mlis and are likely to underestimate the rate of ml restratification and consequently suffer from a bias in sea surface temperatures and ml depths in a

the october 17 1989 loma prieta california earthquake and its aftershocks geometry of the sequence from high resolution locations hypocenters of the loma prieta sequence form a dipping zone that rises from the mainshock hypocenter and is parallel to the mainshock nodal plane most aftershocks cluster around the perimeter of the zone surrounding a relatively aseismic center which approximates the region of mainshock rupture at its southeastern end the dipping aftershock zone warps into a vertical surface that corresponds to the san andreas fault in the central and northwestern parts of the zone at depths above 10 km the aftershocks define numerous disjoint fault structures the large component of reverse slip observed in this event agrees with a simple model for slip on a dipping plane within a compressional fault bend we do not believe that the loma prieta earthquake occurred on the sargent fault however we are unable to conclude whether it ruptured the principal plate boundary fault or a less frequently active fault

incursion of meteoric water triggers molybdenite precipitation in porphyry mo deposits a case study of the chalukou giant mo deposit there has been a long term debate about the timing of the incursion of meteoric water into porphyry systems and whether it plays an important role in ore precipitation to evaluate the role of meteoric water in the mineralization in porphyry mo deposits typical hydrothermal veins of different stages from the chalukou giant porphyry mo deposit are selected for combined scanning electron microscope cathodoluminescence sem cl fluid inclusion microthermometry and high resolution secondary ion mass spectroscopy sims oxygen isotope analyses multiple generations of quartz are identified in almost all of the veins the barren quartz veins and quartz magnetite veins of the early mo mineralization stage are dominated by granular cl bright quartz emq1 which usually shows dissolution and re deposition textures and are overprinted by cl dark quartz emq2 filled healed fractures the molybdenite precipitation in the quartz molybdenite veins of the main mo mineralization stage is synchronous with small volumes 85 of cl bright quartz mmq1 similar to the quartz molybdenite veins the precipitation of pyrite in the quartz pyrite veins during the transitional stage and sphalerite in the quartz sphalerite pyrite veins during the zn pb mineralization stage are also directly associated with cl dark quartz tsq2 zpq2 the sims oxygen isotopic values of emq1 and mmq1 fall into the range of 5 42 9 79 o with calculated equilibrium fluid compositions of 2 07 6 45 0 indicating a magma dominated fluid composition whereas mmq2 tsq2 and zpq2 have very low oxygen isotopic values from 4 68 to 4 29 parts per thousand with corresponding fluid compositions of 13 64 to 5 94 parts per thousand implying that the fluid formed by the mixing of magmatic water and a large proportion of meteoric water the contrasting sem cl features and oxygen isotopic compositions of the two generations of quartz in the quartz molybdenite veins demonstrate that the incursion of meteoric water into the hydrothermal system occurred earlier than the molybdenite precipitation based on these results and the crosscutting relationships and spatial distribution of the veins we reconstructed the quartz evolutionary sequence during the vein development process after the early precipitation of barren quartz the reduction in fluid pressure from lithostatic to hydrostatic conditions allowed the incursion of convecting cool meteoric water into the relatively hot hydrothermal system and the temperature of the evolved mo rich fluid decreased rapidly from 500 degrees c to 400 degrees c leading to concentrated molybdenite precipitation with small volumes of quartz fluid cooling resulting from the incursion of meteoric water may have played a greater role in the metal precipitation in the chalukou mo deposit than wallrock interactions and fluid boiling moreover this process may have also occurred in other porphyry mo deposits

common features of the excitation and propagation of strong ground motion for north american earthquakes the central matter of this investigation is the commonly held belief that eastern north america ena earthquakes are felt to much greater distances at all levels of intensity than their western u s wus counterparts of the same source strength by comparing the areas enclosed by modified mercalli intensities i to iii felt iv v vi and vii for ena and wus earthquakes at the same source strength we find that this proposition is mostly false at damaging levels of ground motion intensities vi to vii and greater for m 7 neither should such differences exist if strong ground motion is confined to r 150 km and arrives principally as body waves and if ena and wus earthquakes share the same average stress drop in fact observable differences in the areas enclosed by intensity vi a vi for ena and wus earthquakes at the same m point to slight but significant differences in stress drop the ena earthquakes having stress drops a factor of about 2 higher only for the largest earthquakes m 7 as the 1811 to 1812 new madrid and 1886 charleston earthquakes seem to be can strong ground motion propagate to much greater distances as low loss higher mode surface waves in ena relative to wus the strong dependence of high frequency strong ground motion on stress drop and its weak dependence on m admit the possibility that the 1811 to 1812 events and the 1886 charleston earthquakes are no larger than m 6 to 7 provided that their stress drops are higher than average by a factor of 2 or so

patterns of seismic release in the southern california region southern california experiences earthquakes on the san andreas system of vertical right lateral predominantly strike slip faults and on a second system of faults that includes thrusts oblique slip left lateral and other faults pattern recognition and cluster analysis are used to analyze the catalog of earthquakes with magnitudes 5 5 from 1915 to 1994 we use pattern recognition to find a suite of traits that would characterize each of these two systems and distinguish them from each other both pattern recognition and cluster analysis show that epochs of seismic release occur in which one or the other system is the predominant form of earthquake activity for the past 2 decades the second system has been the active one small changes in the direction of plate movements could account for this phenomenon seismic release on the san andreas system is preceded by episodes of activity in the great basin or in the gulf of california presumably these episodes would represent extension in the former region and spreading and slip on transform faults in the latter

intracontinental porphyry and porphyry skarn mineral systems in eastern china scrutiny of a special case made in china in this contribution we discuss a series of porphyry and porphyry skarn mineral systems which constitute important metallogenic belts along major lithospheric breaks and or collision zones that form the margins of the north china craton and the yangtze craton we describe a selection of porphyry and porphyry skarn deposits in the great xing an range in northeast china the yanshan liaoning xilamulum belts along the northern margin of the north china craton the qinling orogen and the middle lower yangtze river valley along the bonudaries between the north china and the yangtze cratons the occurrence of platform carbonate successions may have played some role in the evolution of ore fluids that resulted in the formation of porphyry skarn deposits the porphyry deposits of eastern china although sharing some common features with classic porphyry systems that are related to convergent margins do exhibit unusual features particularly in terms of ore fluid compositions the common presence of fluorite hydrothermal alteration assemblages which tend to be less hydrous than the porphyry at convergent margins on the other hand the porphyry mineral systems of eastern china have some similarities with the climax type porphyry a major tectonothermal event yanshanian which took place in the jurassic cretaceous affected eastern china and most of the eastern margin of asia this yanshanian event was responsible for the magmatism and associated mineral systems in the region the granitoid intrusions and accompanying porphyry and porphyry skarn deposits were developed along orogenic belts and major structural discontinuities mostly along the tectonic boundaries between the north china and yangtze cratons and between the northern margin of the north china craton and the mongolia siberia plate the porphyry and porphyry skarn deposits herein described include chalukou in the great xing an range orogen jiguanshan in the xilamulun metallogenic belt xiaojiayingzi lanjiagou chehugou yuanbaoshan in the yanshan liaoning belt nanninhu yuchiling jinduicheng lemeingou in the east qinling orogen tongchakoou shaxi from the middle lower yangtze river valley the role of mantle lithosphere dynamics in eastern china which led to the formation of these porphyry and porphyry skarn mineral systems is discussed and reviewed

the chalukou deposit in the north great xing an range of china a protracted porphyry mo ore forming system in a long lived magmatic evolution cycle abstract the chalukou deposit is located in the north great xing an range of the xing an mongolia orogen bordering and to the northeast of the north china craton the deposit is a high f type porphyry mo deposit hosted by the chalukou composite igneous body containing small intrusive bodies genetically related to mo mineralization the composite igneous body includes pre mineralization dolerite monzogranite and syenogranite syn mineralization rhyolitic porphyry granitic porphyry and fine grained monzogranite and post mineralization rhyolitic porphyry quartz porphyry dioritic porphyry and andesitic porphyry detailed laser ablation inductively coupled plasma mass spectrometry la icp ms u pb zircon dating of the igneous components of the composite igneous body was carried out to determine the temporal framework for magmatism in the chalukou region the new la icp ms u pb ages constraint documented here together with the published ages indicate that there was a protracted porphyry mo ore forming event of approximately 7 million years between ca 152 when the ore related rhyolitic porphyry was emplaced and ca 145 ma when molybdenite ceased being deposited the dating reveals that the mineralization is a part of relatively long lived magmatic cycle involving the emplacement of small doleritic stocks at ca 165 ma that progressively evolved into extensive granitic intrusions at ca 164 ma and then diminished with the emplacement of mineralization related porphyries to ca 152 ma the emplacement of barren early cretaceous magmatism represented by volcanic units in the ca 136 ma guanghua formation and porphyries followed the mineralized magmatism the syn mineralization porphyry units associated with mo contain zircons assaying 15 times higher in u and th than the pre mineralization magmatic phases this indicates that there was a significant enrichment of mo u and th in the magma and directly associated with ore fluid exsolution the return to their normal levels in the three elements in the post mineralization magmatic phases indicates that they were exhausted from the magma chamber in the later phases a genetic model is proposed for the enormous introduction of ore metals and enrichment at the chalukou deposit the protracted and multiphase igneous activity during the long lived magmatism reflects a multistage enrichment of metal and may play a crucial role in the formation of a volatile enriched fertile and large volume magma chamber beneath the chalukou deposit such a chamber is envisaged to be required for the formation of porphyry mo deposits in general

a frontal challenge for climate models the ocean surface is filled with a convoluted web of fronts that separate waters of different temperatures and salinities see the figure just as thin ducts in the lung called alveoli facilitate the rapid exchange of gases when breathing fronts are the ducts through which heat carbon oxygen and other climatically important gases enter into the deep ocean a lack of observations however has hampered progress in understanding the dynamics of fronts which can be as narrow as hundreds of meters and as wide as tens of kilometers global satellite measurements of ocean surface velocities and air sea fluxes for instance are only available at resolutions of a few hundred kilometers although shipboard researchers can sample vertical ocean profiles down to centimeter scales only rarely do they collect profiles that are less than 100 km apart on page 318 of this issue d asaro et al 1 present a breakthrough in observing ocean fronts providing direct observations of the workings of the kuroshio front off japan on scales from kilometers to millimeters this detailed and wide ranging portrait was made possible by the development of towed instruments that continuously sample the waters behind a steaming ship the deployment of freely drifting instruments that follow ocean currents and the exercising of a great deal of ingenuity in keeping all these tools along the front for a few weeks in 2007

do altimeter wavenumber spectra agree with the interior or surface quasigeostrophic theory in high eddy energy regions it is generally assumed that sea level wavenumber spectra compare well with quasigeostrophic qg turbulence models and that spectral slopes are close to the expected k 5 law this issue is revisited here sea level wavenumber spectra in the gulf stream kuroshio and agulhas regions are estimated using the most recent altimeter datasets the ocean topography experiment topex poseidon jason 1 the environmental satellite envisat and the geosat follow on the authors show that spectral slopes in the mesoscale band are significantly different from a k 5 law in disagreement with the qg turbulence theory however they very closely follow a k 11 3 slope which indicates that the surface quasigeostrophic theory sqg is a much better dynamical framework than the qg turbulence theory to describe the ocean surface dynamics because of the specific properties of the sqg theory these results offer new perspectives for the analysis and interpretation of satellite data

alteration mapping with short wavelength infrared swir spectroscopy on xiaokelehe porphyry cu mo deposit in the great xing an range ne china metallogenic and exploration implications abstract the newly discovered xiaokelehe porphyry cu mo deposit pcd is situated in northern part of the great xing an metallogenic belt northeastern china the syn mineralization granodiorite porphyry was intruded by multiple phases of post ore barren monzonite diorite porphyry and granite porphyry leading to complex and overprinting hydrothermal alteration patterns this paper present new data on the alteration mineralogy vein paragenesis sulfide assemblages and swir short wavelength infrared spectroscopy at xiaokelehe and discuss how swir spectral data can help to understand hydrothermal fluid evolution and assist pcd exploration at xiaokelehe oligoclase epidote alteration is distributed at the deeper levels of the granodiorite porphyry but played little role in mineralization the following potassic alteration hydrothermal biotite and k feldspar was developed in the granodiorite porphyry with the main cu mo mineralization drill core logging suggests that the subsequent chlorite illite alteration affected almost the entire granodiorite porphyry and is spatially and genetically associated with minor cu mineralization the youngest quartz muscovite pyrite alteration dominated in the upper level and outer parts of the pcd and overprints the earlier alteration phases with only very minor mineralization the short wavelength infrared swir analysis results indicate that chlorite and white micas illite and muscovite are the most abundant alteration minerals at xiaokelehe the wavelengths of fe oh band pos2250 of chlorite show a decreasing trend away from the granodiorite porphyry into the surrounding sedimentary wall rocks probably reflecting a drop in temperature and fe contents of the hydrothermal fluids the illite crystallinity ic values of white micas show a reverse trend different from many pcds which is likely caused by the distribution pattern of illite and muscovite formed in the ore proximal chlorite illite and ore distal quartz muscovite pyrite alteration respectively at xiaokelehe cu and mo mineralization is mainly distributed in quartz veins or disseminated within the potassic alteration zones resembling typical pcds meanwhile chlorite illite alteration is also associated with minor cu mineralization thus areas with intensive chlorite illite alteration overlapping on potassic alteration likely represent the best exploration targets for high grade cu mo mineralization these target areas coincide spatially with areas of lower ic 2245 nm values suggesting the latter two are effective vectoring tools for pcd exploration at xiaokelehe

geochemical signature of the granitoids in the chalukou giant porphyry mo deposit in the heilongjiang province ne china abstract the chalukou porphyry mo deposit located in the northern great xing an range is the largest mo deposit in the xing an mongolia orogenic belt its ore bodies are mainly hosted in the intermediate felsic complex and jurassic volcanic sedimentary rocks of which late jurassic granite porphyry quartz porphyry and fine grained granite are closely associated with mo mineralization the middle jurassic monzogranite belongs to shoshonite series with sio2 and al2o3 contents of 69 48 to 74 98 and 12 35 to 14 48 respectively the total alkali k2o na2o content ranges from 7 67 to 10 42 with k2o na2o ratios between 1 07 and 2 81 these rocks are strongly enriched in rb and k but are depleted in ta nb p and ti with negative eu anomalies and positive ehf t the late jurassic granite porphyry quartz porphyry and fine grained granite are shoshonite or high k calc alkaline series their sio2 and al2o3 contents range from 73 87 to 78 95 and 10 35 to 13 47 respectively the total alkali k2o na2o contents range from 8 06 to 10 02 with k2o na2o ratios from 1 03 to 8 20 these rocks are strongly enriched in rb k and th but are depleted in p ti ba and sr indicating clear negative eu anomalies and positive ehf t the middle late jurassic granitoids in the chalukou deposit are highly fractionated i type granitoids and derived from juvenile lower crust materials that originated from the neoproterozoic depleted mantle these granitoids formed in the extension tectonic setting of the post collision stage of the mongol okhotsk orogenic belt probably superposed by the back arc extension related to the subduction of the paleo pacific plate

the near source ground motion of the 6 august 1979 coyote lake california earthquake a finite fault striking n24 w and extending to a depth of 10 km is proposed to explain the strong ground motion data for the 6 august 1979 coyote lake california earthquake m l 5 9 our source model suggests that right lateral faulting initiated at a depth of 8 km and ruptured toward the south with a velocity of 2 8 km sec this unilateral rupture can explain the large displacement recorded south of the epicenter however the waveform coherency across an array south and southwest of the epicenter suggests that the rupture length is less than 6 km the maximum dislocation is about 120 cm in a small area near the hypocenter and the total moment is estimated to be 3 5 10 24 dyne cm an abrupt stopping phase which corresponds to a deceleration of right lateral motion can explain the high peak acceleration recorded at array station 6 the stress drop in the hypocentral area is about 140 bars the average stress drop over the entire rupture surface is 30 bars the preferred finite source model can predict the p n1 waveforms and the beginning features in the teleseismic seismograms no clear arrivals can be observed in the near source data for the possible second and third smaller events suggested by nabelek personal communication

spectral decomposition of internal gravity wave sea surface height in global models two global ocean models ranging in horizontal resolution from 1 12 to 1 48 are used to study the space and time scales of sea surface height ssh signals associated with internal gravity waves igws frequency horizontal wavenumber ssh spectral densities are computed over seven regions of the world ocean from three simulations of the hybrid coordinate ocean model hycom and two simulations of the massachusetts institute of technology general circulation model mitgcm high wavenumber high frequency ssh variance follows the predicted igw linear dispersion curves the realism of high frequency motions 0 87cpd in the models is tested through comparison of the frequency spectral density of dynamic height variance computed from the highest resolution runs of each model 1 25 hycom and 1 48 mitgcm with dynamic height variance frequency spectral density computed from 9 in situ profiling instruments these high frequency motions are of particular interest because of their contributions to the small scale ssh variability that will be observed on a global scale in the upcoming surface water and ocean topography swot satellite altimetry mission the variance at supertidal frequencies can be comparable to the tidal and low frequency variance for high wavenumbers length scales smaller than 50km especially in the higher resolution simulations in the highest resolution simulations the high frequency variance can be greater than the low frequency variance at these scales

location and size of the 1927 lompoc california earthquake from tsunami data abstract the lompoc earthquake of 4 november 1927 m s 7 0 was one of the largest offshore events in california and the associated tsunami was recorded in hawaii as well as on the california coast the epicenter of this event has long been debated one location is offshore where the ocean is about 1000 m deep whereas another location is very near shore beneath a water depth of less than 100 m we analyzed the tsunami records from this event from tsunami travel times the source location was estimated to be well offshore at about 34 2 n 120 75 w consistent with recent seismic waveform analysis waveform modeling of the tsunami also supports an outer continental shelf location the seismic moment is estimated to be 3 10 26 dyne cm corresponding to a moment magnitude of 7 0 the tsunami computation reproduced the large tsunami in hawaii indicating that the observed large tsunami was due to bathymetry effects particularly near hilo bay the tsunami magnitude of 7 6 obtained from the hawaiian recordings by abe thus appears to be an overestimate

an annual cycle of submesoscale vertical flow and restratification in the upper ocean abstractnumerical simulations suggest that submesoscale turbulence may transform lateral buoyancy gradients into vertical stratification and thus restratify the upper ocean via vertical flow howev

the mo deposits of northeast china a powerful indicator of tectonic settings and associated evolutionary trends abstract northeast ne china lies in the eastern sector of the central asian orogenic belt caob that connects with the circum pacific orogenic belt in the east and accommodates multistage magmatism crustal growth and mineralization in this region 69 mo only or mo dominated and 9 cu mo deposits have been discovered including 65 deposits ranking medium size 10 kt mo metal or larger in tonnage and containing a total resource of 10 5 mt mo metal six giant and seventeen large deposits have total reserves of 6 7 and 3 1 mt mo respectively these deposits occur in the areas surrounding the songliao basin including the northern margin of the north china craton the great hingan range and the ji hei fold belt and have been formed during paleozoic and mesozoic tectono magmatic events all the mo only or mo dominated deposits were formed in the mesozoic postdating the closure of the paleo asia ocean and in a series of pulses around 250 200 ma 200 160 ma 160 130 and

submesoscale dynamics in the northern gulf of mexico part iii lagrangian implications abstractfour numerical simulations are used to characterize the impact of submesoscale circulations on surface lagrangian statistics in the northern gulf of mexico over 2 months february and august representative of winter and summer the role of resolution and riverine forcing is explored focusing on surface waters in regions where the water column is deeper than 50 m whenever submesoscale circulations are present the probability density functions pdfs of dynamical quantities such as vorticity and horizontal velocity divergence for eulerian and lagrangian fields differ with particles preferentially mapping areas of elevated negative divergence and positive vorticity the stronger the submesoscale circulations are the more skewed the lagrangian distributions become with greater differences between eulerian and lagrangian pdfs in winter lagrangian distributions are modestly impacted by the presence of the riverine outflow while increasing the model resolution from submesoscale permitting to sub

m 6 earthquakes in southern california during the twentieth century no evidence for a seismicity or moment deficit abstract a broadly based report on seismic hazards in southern california wgcep 1995 concluded that the predicted seismicity exceeds that observed since 1850 a subsequent independent analysis argued that infrequent huge m 8 earthquakes are needed to explain the low rate of large earthquakes jackson 1996 frequency magnitude relationships and earthquake reporting suggest that the 1903 to 1997 catalog we present here with a b value of 1 0 and a rate of m 6 shocks of 0 42 to 0 49 yr 1 is nearly complete in contrast the 1850 to 1994 catalog used by wgcep is incomplete before the turn of the century and thus its reported seismicity rate of 0 32 m 6 shocks yr 1 is too low principally because the wgcep 1995 model results in b values of up to 4 0 for regions of lesser and blind faults the rate of m 6 shocks off the san andreas system predicted by the wgcep 1995 model is three times greater than that observed in this century because they obtained b 0 4 for m b 2 2 for m 7 3 on major faults their expected rate of m 7 san andreas shocks is twice as high as observed thus part of the seismicity and moment discrepancy identified by wgcep was caused by use of an incomplete catalog and part was caused by inappropriate b values we obtain a southern california moment release rate of 8 to 12 10 18 n m yr 1 which cannot be distinguished from the moment release estimated by fault slip or the moment accumulation inferred from plate motions or geodetically measured shear strain we thus find no evidence for a moment deficit significant aseismic moment release or for rare m 8 earthquakes off the san andreas fault system finally the number of m 6 earthquakes per decade does not depart significantly from a poisson process during this century and thus we find no evidence that the rate of seismicity is increasing now or at any other time since 1900

geodynamic setting of mesozoic magmatism in ne china and surrounding regions perspectives from spatio temporal distribution patterns of ore deposits abstract north eastern china and surrounding regions host some of the best examples of phanerozoic juvenile crust on the globe however the mesozoic tectonic setting and geodynamic processes in this region remain debated here we attempt a systematic analysis of the spatio temporal distribution patterns of ore deposits in ne china and surrounding regions to constrain the geodynamic milieu from an evaluation of the available geochronological data we identify five distinct stages of ore formation 240 205 ma 190 165 ma 155 145 ma 140 120 ma and 115 100 ma the triassic 240 205 ma magmatism and associated mineralisation occurred during in a post collisional tectonic setting involving the closure of the paleo asian ocean the early mid jurassic 190 165 ma events are related to the subduction of the paleo pacific ocean in the eastern asian continental margin whereas in the erguna block these are associated with the subduction of the mongol okhotsk ocean from 155 to 120 ma large scale continental extension occurred in ne china and surrounding regions however the late jurassic magmatism and mineralisation events in these areas evolved in a post orogenic extensional environment of the mongol okhotsk ocean subduction system the early stage of the early cretaceous events occurred under the combined effects of the closure of the mongol okhotsk ocean and the subduction of the paleo pacific ocean the widespread extension ceased during the late phase of early cretaceous 115 100 ma following the rapid tectonic changes resulting from the paleo pacific oceanic plate reconfiguration

the global frequency wavenumber spectrum of oceanic variability estimated from topex poseidon altimetric measurements two years of altimetric data from the topex poseidon spacecraft have been used to produce preliminary estimates of the space and time spectra of global variability for both sea surface height and slope the results are expressed in terms of both degree variances from spherical harmonic expansions and in along track wavenumbers simple analytic approximations both in terms of piecewise power laws and pade fractions are provided for comparison with independent measurements and for easy use of the results a number of uses of such spectra exist including the possibility of combining the altimetric data with other observations predictions of spatial coherences and the estimation of the accuracy of apparent secular trends in sea level

tsunamis within the eastern santa barbara channel several locally generated tsunamis have been reported in southern california during the past 200 years yet the hazard from locally generated tsunamis has received considerably little attention we consider here tsunamis generated by coseismic displacements on the channel islands thrust cit system as well as waves generated by slope failures along the walls of the santa barbara channel we find that purely tectonic sources could generate regional tsunamis with 2m runup whereas combinations of tectonic sources and submarine mass movements could generate local runup as large as 15m