estimation of interannual and interdecadal variations of typhoon induced primary production a case study for the outer shelf of the east china sea 1 using multiplatform satellite data and 13 typhoon passages from 1998 through 2004 an empirical relationship to assess typhoon forced primary production pp enhancement in the outer shelf of the east china sea is introduced the constructed relationship requires variables of typhoon maximum sustained wind typhoon transit speed and bottom depth of the location below the typhoon track as this relationship does not require ocean color data it enabled us to reconstruct the interannual and interdecadal variations of typhoon forced pp enhancement from 2004 back to 1980 typhoon forced pp enhancements and typhoon contributions to summer fall new production during el nino years tended to be higher than those during la nina years typhoon enhanced pp also has shown a tendency to be higher during the 1991 2004 period than during the 1980 1990 one the method we detail in this study is applicable for other tropical cyclone trajectory basins

radial qμ structure of the lower mantle from teleseismic body wave spectra abstract we have measured 150 000 p and 130 000 s wave spectral ratios up to 0 8 hz using recordings of 250 deep focal depth 200 km earthquakes from 890 global and regional network stations we have inverted these data to estimate the attenuation parameters t p and t s for p and s waves and a radial profile of the quality factor q for the lower mantle on average t p increases by about 0 2 s and t s increases by about 0 7 s between epicentral distances of 30 and 97 the relatively strong increase of t s t s 4t p suggests that intrinsic shear attenuation is the cause of the overall trend in our data the increase of t p and t s with distance is smaller than predicted by models prem 12 ql6 11 and qlm9 16 assuming prem values for q in the upper mantle where the data lack resolving power the p and s wave spectra are explained best if q increases from about 360 at prem s 670 km discontinuity to 670 in the lowermost mantle the high values for q can be reconciled with previously determined values by invoking a frequency dependence of q that is proportional to 0 1 data that are separated in pacific and circum pacific subsets have slightly different trends estimates of t p and t s for the pacific data which sample the large low shear velocity province of the pacific are higher than the circum pacific estimates thus it appears that the pacific large low shear velocity province has accompanying low q the difference in q in the lowermost 1000 km of the mantle beneath the pacific and beneath the circum pacific is at most 17 lateral variations of this magnitude are marginally resolvable given the uncertainties of our measurements

dynamic and thermal responses of the kuroshio to typhoon megi 2004 relatively weak hurricane induced cooling 1 c is often observed in the loop current while observed sea surface temperature sst cooling is much stronger in the kuroshio this was previously attributed to strong advection effects by the loop current based on a budget analysis this study quantitatively diagnoses the dynamic and thermal responses of the kuroshio to typhoon megi and four additional tropical cyclones tcs which produce up to 3 c sst cooling within the kuroshio itself the results show that the surface thermal response of the kuroshio is a wind induced temperature cooling primarily due to vertical mixing up to 96 the dynamic response of the kuroshio depends not only on tc conditions intensity and wind direction but also on prestorm ocean conditions e g ocean mixed layer depth baroclinicity and current velocity differently from the open ocean where the ocean gains kinetic energy mainly from wind stress work the kuroshio can obtain greater kinetic energy from its baroclinic pressure work especially in the upper ocean the strong sst cooling observed in the kuroshio region is therefore likely associated with the kinetic energy extracted from the kuroshio baroclinic potential energy which greatly enhances local vertical mixing

progress on upwelling studies in the china seas east asian marginal seas surrounding china exhibit rich ocean upwelling mostly in response to the southwesterly summer monsoon upwelling in the china seas namely the south china sea the taiwan strait the east china sea the yellow sea and the bohai sea has become increasingly important because the potential changes in the upwelling may have dramatic ecosystem socioeconomic and climate impacts this paper reviews the progress of upwelling studies in the china seas since the year 2000 by presenting the principal characteristics and new understanding of 12 major upwelling regions in the china seas upwelling exhibits long term variability at intraseasonal to multi decadal scales as well as short term variability frequently caused by tropical cyclones it is also associated with the el nino southern oscillation local environmental variation and biogeochemical factors the coastal upwelling around hainan island and the upwelling or cold dome northeast of taiwan island are specifically highlighted because they have attracted great interest for decades this paper summarizes upwelling mechanisms in terms of wind topography tide stratification and background flow with applications mostly to the china seas finally we propose some topics for future upwelling research i e potential intensification of coastal upwelling under global climate change downwelling intrusion of upwelling into coastal embayments and the influence of upwelling on fishery and biogeochemical processes

seismic attenuation in northeastern sonora mexico we studied the attenuation of local and regional earthquake body waves recorded by the seismic network of northeastern sonora mexico red sismica del noreste de sonora resnes the source station paths of the selected data set cover the epicentral region of the may 1887 m w 7 5 sonora earthquake we used the best located earthquakes recorded by resnes between 2003 and 2004 to analyze the spectral amplitude decay of body waves with hypocentral distance the database consists of 44 earthquakes with magnitudes between 1 8 and 3 2 and hypocentral distances between 25 and 150 km we calculated fourier spectral amplitudes from more than 400 records and defined attenuation functions with a nonparametric model by inverting the observed spectral amplitudes at 23 individual frequencies between 0 4 and 63 1 hz we determined regional attenuation curves based on events located more than 100 km northwest of the center of the network and local curves based on earthquakes located near the fault zone that ruptured in the 1887 earthquake the obtained attenuation curves indicate that the spectral amplitudes decay faster in the area of the 1887 rupture than in the surrounding region to analyze the possible sources of attenuation we parameterized the attenuation functions considering three terms one that accounts for geometrical spreading another one for anelastic attenuation and a third for near surface attenuation we found the s wave quality factor q to be similar in both the general region and near the 1887 rupture however in the region of the 1887 rupture the near surface attenuation exceeds the regional average finally in the region of the 1887 rupture the nonparametric attenuation functions and the estimates of q indicate that at between 0 6 and 63 1 hz p waves attenuate more than s waves q p 20 8 f 1 1 whereas q s 83 8 f 0 9

lg attenuation characteristics across the indian shield abstract new measurements of lg q are obtained using a reliable two station method to understand the attenuation characteristics across the indian subcontinent we use data from 514 events with magnitude 3 5 and depth less than 40 km collected during 2006 2008 from 17 stations deployed across india we measure 1 hz lg q q 0 values between many pairs of stations finally 34 high quality interstation paths were selected from 336 possible pairs that are 1 aligned approximately with the source and 2 separated enough to permit the use of the standard two station method for lg q measurement we found some spatial variation in lg wave attenuation across india low q regions are present in western india we attribute this to the recent tectonic activities in this region the central indian platform shows a moderate to high q 0 value the southernmost part of india exhibits higher values which may indicate that the crust in this part is more stable the obtained values correlate with the regional crustal heterogeneities and tectonic trends as a whole the estimated interstation q 0 values compare well with the areas of moderate seismicity across the earth

movement of the kuroshio axis to the northeast shelf of taiwan during typhoon events abstract we investigated the movement of the kuroshio axis on the northeast shelf of taiwan associated with the passage of typhoons using sea surface current data observed by the ocean radar system on yonaguni and ishigaki islands first we examined daily kuroshio axis variation on the northeast shelf of taiwan during typhoon events the ocean radar data showed that the kuroshio axis moved onto the shelf after passages of typhoons the kuroshio moved onto the shelf and stayed there after the passage of typhoon hai tang while the kuroshio maintained this pattern southerly wind blew continuously for 4 days the mean current speed northeast of taiwan after the typhoon s passage increased by 18 cm s 1 in addition the sea level difference between two satellite altimetry tracks east of taiwan increased by 14 4 cm these results suggest that coastal upwelling east of taiwan caused by the southerly wind generated an east west sea level difference that in turn generated a northward geostrophic current this current could have enhanced the kuroshio east of taiwan and pushed it onto the shelf

a continent wide map of 1 hz lg coda q variation across eurasia and its relation to lithospheric evolution 1 we present new maps of lg coda q qo and its frequency dependence at 1 hz that cover virtually all of eurasia qo is relatively high up to 650 or more in the east european siberian indian and kazakh platforms but is surprisingly low 300 500 in the arabian platform and western portion of the siberian platform as well as in great britain and the northwestern portion of mainland europe it is generally low throughout the tethysides orogenic belt but there too it displays substantial regional variations 150 400 most qo anomalies appear to be related to the tectonic history of the eurasian crust the four regions with lowest values coincide with four of eurasia s most active concentrations of earthquake activity observed eurasian qo values are consistent with a previously determined empirical plot of global values in which qo in any region is proportional to the time elapsed since the most recent episode of tectonic or orogenic activity there comparisons of the new qo map with maps of rayleigh wave velocity temperature subducted lithosphere and seismicity lead us to infer that lg coda wave attenuation is most easily explained by energy lost in moving fluids through permeable rock or in being scattered from fluid enhanced zones the fluids are likely to have originated by hydrothermal release from subducting lithosphere or other upper mantle heat sources anomalies in qo and other lithospheric properties in some cases extend well outside the tethysides belt and other regions where upper mantle heat sources are known to occur possible explanations include earlier episodes of subduction activity crustal deformation due to collision of the afro arabian and indian plates or broader than expected back arc activity beneath eurasia

spectral characteristics of the excitation and propagation of lg from underground nuclear explosions in central asia the nonlinear inverse method of xie 1993 is applied to analyze lg spectra from many recent underground nuclear explosions in central asia the analysis simultaneously determines lg seismic moments m0 and corner frequencies fc of events as well as path variable lg q values and their frequency dependences at 1 hz lg q at 1 hz estimated for many paths from the lop nor and balapan test sites to various broadband incorporated institution for seismology chinese digital seismic network and kyrghizstan network stations agree well with path averaged lg coda q values from previously obtained tomographic maps for eurasia this suggests that the lg q values obtained in this inversion have not been significantly affected by focusing defocusing or other effects of three dimensional structural complexities the logarithms of lg m0 values obtained in this study correlate linearly with a slope of about 1 2 with international seismological centre isc body wave magnitudes mb the linear relationship is consistent with a previous empirical relationship found between the logarithm of p wave seismic moments and isc mb values the slope of the linear relationship also suggests that the logarithm of lg m0 is a more direct measure of event size than is mb which for larger events is affected by high frequency amplitude falloff another important finding of this study is that the m0 values for the explosions scale with fc 4 rather than with fc 3 as would be expected if stress drops were constant this is consistent with previous scaling relations derived using lg from earthquake sources and suggests that the difference between lg and local s excitation by the same source types explosion or earthquake may overwhelm that between the excitation of lg by different source types a comparison between lg m0 and fc values obtained using an explosion source model with those obtained using an earthquake source model suggests that the m0 values estimated using the explosion source model are systematically lower by a factor of 0 27 than those estimated using the earthquake source model this occurs even though the data used are the same in the inversions with the two types of source model the factor of 0 27 is therefore due to the source model dependence of the m0 fc estimates the overshoot and lower spectral levels at lower frequencies in the explosion source model tend to reduce both the estimated m0 and fc values this suggests that in any nuclear monitoring program the same type of source model either an earthquake or explosion should always be used to discriminate explosions using lg the source model dependence also suggests that more effort should be made to estimate the amount of overshoot in the lg excitation caused by various source types

attenuation of coda waves in western mexico using local seismicity coda waves are an important instrument to study the elastic properties of the lithosphere the attenuation of coda waves in western mexico is analyzed using seismograms recorded during the mapping of the rivera subduction zone experiment the coda wave attenuation is measured by means of q within the single backscattering model and the single isotropic scattering model schemes the frequency dependence of q is analyzed using the power fit formulation q f q f the resulting q q and are then used to study the seismic attenuation properties in western mexico we compare our results with the crustal structure by means of the surface geology seismic activity crustal thickness and p wave velocity patterns in the study area there is a poor correlation of the attenuation parameters with such crustal features however an analysis of the variations of the p wave velocity shows that the seismic attenuation parameters correlate to some extent with seismic velocity variations previously noted in the study area where low attenuation and weak frequency dependence correlate with low velocity variation

attenuation of multiphase surface waves in the basin and range province part i lg and lg coda summary broad band data recorded by the lawrence livermore laboratory network are used to investigate whether or not lg q and lg coda q have similar values in the basin and range province of north america in order to retrieve spectral estimates of the broad band lg and lg coda signals a hybrid method is used which retains high fidelity at lower frequencies while strongly smoothing the spectral estimates and minimizing the number of spectral points at high frequencies a stochastic approach is used to model the lg signal and ambient noise and to analyse results from two station determinations of lg q in the basin and range the effects of ambient noise frequency dependent station site response and focusing defocusing on lg q inversion are analysed it is shown that after averaging spectral ratios determined from repeated observations over four two station paths a modest site effect will not cause significant errors in the resulting lg q relation using this inversion scheme and spectral ratio estimates averaged over those paths at frequencies between 0 2 and 2 5 hz we obtain the relation qlg f 267 f 56 f0 37 0 06 for the basin and range province further constraints on lg q were obtained from lg coda which due to the natural averaging effect of scattering is insensitive to effects of focusing defocusing to investigate the validity of the single isotropic scattering model for lg coda in the basin and range province we calculated ischrons for scatterers corresponding to later lg coda signals as required by the single scattering model it is found that when significant portions of these isochrons are oceanic lg coda amplitude decay becomes irregular and abnormally slow suggesting a strong scattering reflection effect caused by the rapidly changing crustal structure along the coast applying the single isotropic scattering model to lg coda records with isochrons mostly confined to the continental crust results in q f 275 f 26 f 0 36 0 03 which is nearly identical to our qlg relation this indicates that even in a complicated geological province a joint interpretation of the dynamic properties of lg and lg coda can be successful and fruitful inconsistent lg q and coda q relations found in earlier studies in the basin and range province may be attributed to different settings of parameter trade offs different seismic phases or different dynamic properties being used

interpretation of high frequency coda at large distances stochastic modelling and method of inversion summary based on previous work a stochastic convolution model is proposed for the lg coda observed at large epicentral distances 200 km coda at these distances differ from local coda in several respects effects of various physical processes such as dispersion scattering and mode conversion on coda at large distances are discussed in detail a spectral ratio method is developed for inversion of lg coda q in which the large variance associated with inversion is greatly reduced the method is also extended to the inversion of seismic source parameters by jointly using lg and its coda we have tested the model and method exhaustively using data from two gdsn stations and found the results to be superior to other methods when those methods used only a small number of stations

lg magnitudes and yield estimates for underground novaya zemlya nuclear explosions abstract lg wave amplitudes of 30 novaya zemlya underground nuclear explosions as recorded by short period seismographs in denmark finland germany norway spitsbergen and sweden are used to determine m b lg values assuming that the m b lg versus explosion yield relation derived from nevada test site data applies to all continental areas the yields of the explosions are estimated they cover a large range of values from 2 5 to 4900 kt the largest explosion since april 1976 had an estimated yield of 145 kt the m b lg values when subtracted from the m b p values can be used to estimate the m b p bias between two test sites in this way the m b p bias between novaya zemlya and the nevada test site is estimated to be 0 20 magnitude units

lg coda q variation across eurasia and its relation to crustal evolution an extensive set of broadband and short period seismograms from regional seismic events has been used to derive a tomographic image of broad scale variations of lg coda q for most of eurasia the image indicates that lg coda q at a frequency of 1 hz varies between about 200 and 1000 lowest q values 800 are found in four regions the east european shield the siberian shield the indian shield and the southwestern and oldest portion of the altaid belt the pattern of lg coda q variation across eurasia suggests that crustal q in any region is directly proportional to the length of time that has elapsed since the most recent episode of large scale compressional tectonic activity or upper mantle heating that occurred there we interpret the low q as resulting largely from hydrothermal fluids generated by tectonic activity or heating that now reside in cracks and permeable portions of the eurasian crust crustal q increases with time after that activity as fluids are lost to the surface or absorbed by retrograde metamorphism

lg coda q and its relation to the geology and tectonics of the middle east regional seismograms were collected to image the lateral variations of lg coda q at 1 hz q 0 and its frequency dependence in the middle east using a back projection method the data include 124 vertical component traces recorded at 10 stations during the period 1986 1996 the resulting images reveal lateral variations in both q 0 and in the turkish and iranian plateaus a highly deformed and tectonically active region q 0 ranges between about 150 and 300 with the lowest values occurring in western anatolia where extremely high heat flow has been measured the low q 0 values found in this region agree with those found in other tectonically active regions of the world throughout most of the arabian peninsula a relatively stable region q 0 varies between 350 and 450 being highest in the shield area and lowest in the eastern basins all values are considerably lower than those found in most other stable regions low q values throughout the middle east may be caused by interstitial fluids that have migrated to the crust from the upper mantle where they were probably generated by hydrothermal reactions at elevated temperatures known to occur there low q 0 values about 250 are also found in the oman folded zone a region with thick sedimentary deposits varies inversely with q 0 throughout most of the middle east with lower values 0 4 0 5 in the arabian peninsula and higher values 0 6 0 8 in iran and turkey q 0 and are both low in the oman folded zone and western anatolia

propagation of lg waves in the north australian craton influence of crustal velocity gradients abstract aftershocks of three large earthquakes near tennant creek in the northern territory of australia provide a unique opportunity to study regional seismic phases in the north australian craton three portable digital seismographs were operated near the source zone to provide control on earthquake locations and seven recorders formed a line between tennant creek and the seismic array at alice springs which is 430 km to the south eleven earthquakes of sufficient size for analysis were recorded during a one week deployment two months following the main shocks the group velocity observed for lg waves along this profile of 3 7 km sec is at the high end of the normal range and appropriate for a stable continental interior we estimate attenuation in discrete frequency bands by measuring the decay of amplitude as a function of distance from the source and assuming the common r 5 6 relationship for geometrical spreading however this assumption leads to frequency dependent q values q 230 36 f 0 66 0 12 that are abnormally low for a stable continental region the apparent q is also not consistent with other observations such as the high lg group velocity the positive bias in m l estimates obtained for other parts of australia using standard attenuation relations the size of felt areas for large central australian earthquakes nor with the high frequency content of seismic reflection data collected near our profile some crustal models for northern australia derived from seismic refraction work show a gradient zone between 30 and 55 km rather than a sharp moho discontinuity we therefore investigate the effect of gradient zones at the crust mantle transition on the decay of lg amplitudes using synthetic seismograms calculated with the wavenumber integral method the modeling suggests that some of the s wave energy that would be trapped in a crustal wave guide with a sharp lower boundary can leak out in the presence of a gradient and so enhance the attenuation in addition there are focusing effects due to the formation of caustics from the gradient zones which cannot be represented by a single analytic amplitude correction

evaluation of strength of heterogeneity in the lithosphere from peak amplitude analyses of teleseismic short period vector p waves summary we quantitatively characterize the regional variations in the strength of heterogeneity in the lithosphere of the globe by analysing the observed seismogram envelopes of teleseismic p waves in the frequency band of 0 5 4 hz we apply a theoretical scattering model based on the markov approximation for a plane p wave propagating through the random medium characterized by a gaussian autocorrelation function since this model presumes the vertical incidence of an impulsive plane wavelet we first analyse teleseismic p waves from deep earthquakes occurring along the western pacific regions we measure the ratios of peak intensity of transverse components to that of the sum of the three components and determine the quantity of randomness e 2 z a where e a and z are fractional fluctuation correlation distance and thickness of a heterogeneous structure respectively although source time functions of shallow earthquakes are too complex to directly apply the scattering model a good correlation between the ratios of peak amplitude and the normalized transverse amplitude which is the square root of the energy partition of the p coda waves into the transverse component enables us to use the shallow earthquakes that occur widely around the world as a result the quantity e 2 z a extends from 1 15 10 4 to 6 34 10 2 at 0 5 1 hz 2 02 10 3 to 1 89 10 1 at 1 2 hz and 1 49 10 4 to 1 89 10 1 at 2 4 hz which are in agreement with the results of previous studies using different methods the spatial distribution of randomness almost agrees with various tectonic settings and roughly correlates with lateral variations of lg coda q and shear wave velocity perturbations at 80 km depth suggesting that lateral heterogeneity extends from the shallow crust to uppermost mantle

effect of low q sediments and crustal q on lg attenuation in the united states q values for lg and its coda exhibit significant lateral variations across the united states some of which correlate with known variations in the thickness of shallow sedimentary layers the possibility that all variations in lg attenuation are caused by changes in the thickness of shallow sediments is investigated by computing multi mode synthetic seismograms for crustal models with various thicknesses of low q sediments using crustal velocity and q models obtained in previous studies and reasonable values for the thicknesses and intrinsic q values of sediments in several regions we find that the variation of lg q values between the appalachian and rocky mountains can easily be produced by varying accumulations of sandstone and shale of mesozoic age and younger by contrast throughout most of the western united states neither the low lg q values which have been observed nor the regional variation of those values can be explained by accumulations of low q sediments instead their explanation appears to require low and laterally varying values of q in the crystalline crust

qlg distribution in the basin and range province of the western united states q values for the direct l g phase were estimated for event station q lg paths that lie entirely within the western united states particularly in the southern great basin and surrounding areas the qo at 1 hz values were estimated by qlg fitting synthetic spectra to observed lg spectra using a genetic algorithm technique we have created a tomographic image of the variations of qo for a part of the southwestern united states the image shows that qo varies between about 234 and 312 at 1 hz with an average of 267 the lowest qo occurs in the northwest part of the basin and range province where extensional deformation has occurred since the mesozoic qo values start to increase toward the colorado plateau to the east and continue to gradually increase northward and decrease southward we also find rela tively high frequency dependence to the values with a 1d mean of g 0 57 qlg

a case for the use of 3d attenuation models in ground motion and seismic hazard assessment abstract attenuation relationships that are used to characterize estimated ground motion often ignore details of the earth s highly variable 3d velocity and attenuation structure increasingly available attenuation models can be used to refine the expected ground motions first some tests are performed to look at the effect of the variability in several parameters such as crustal attenuation upper mantle attenuation and crustal thickness a concrete example is then provided using the results of a recent crust and upper mantle attenuation model of the middle east variations in 1 hz spectral accelerations of 30 40 are found simply from the same event recorded in different directions because overall regional variability is expected to be even higher this effect seems significant enough to be accounted for in strong ground motion estimates and seismic hazard assessment this has the potential to account for some of the smaller scale amplitude variations not considered using broadly applied 1d attenuation relationships

attenuation of high frequency seismic waves in northeast india summary we studied attenuation of s and coda waves their frequency and lapse time dependencies in northeast india in the frequency range of 1 24 hz we adopted theories of both single and multiple scattering to bandpass filtered seismograms to fit coda envelopes to estimate q for coda waves qc and q for s waves qs at five central frequencies of 1 5 3 6 12 and 24 hz the selected data set consists of 182 seismograms recorded at ten seismic stations within epicentral distance of 22 300 km in the local magnitude range of 2 5 5 2 we found that with the increase in lapse time window from 40 to 60 s q0 qc at 1 hz increases from 213 to 278 while the frequency dependent coefficient n decreases from 0 89 to 0 79 both qc and qs increase with frequency the average value of qs obtained by using coda normalization method for ne india has the power law form of 96 8 21 5 f 1 03 0 04 in 1 24 hz we adopted energy flux model efm and diffusion model for the multiple scattered wave energy in three dimensions the results show that the contribution of multiple scattering dominates for longer lapse time close to or larger than mean free time of about 60 s the estimates of qc are overestimated at longer lapse time by neglecting the effects of multiple scattering some discrepancies have been observed between the theoretical predictions and the observations the difference could be due to the approximation of the uniform medium especially at large hypocentral distances increase in qc with lapse time can be explained as the result of the depth dependent attenuation properties and multiple scattering effect

attenuation of lg waves in the new madrid seismic zone of the central united states using the coda normalization method abstract unique properties of coda waves are employed to evaluate the frequency dependent quality factor of lg waves using the coda normalization method in the new madrid seismic zone of the central united states instrument and site responses are eliminated and source functions are isolated to construct the inversion problem for this purpose we used 121 seismograms from 37 events with moment magnitudes m ranging from 2 5 to 5 2 and hypocentral distances from 120 to 440 km recorded by 11 broadband stations a singular value decomposition svd algorithm is used to extract q values from the data while the geometric spreading exponent is assumed to be a constant inversion results are then fitted with a power law equation from 3 to 12 hz to derive the frequency dependent quality factor function the final results of the analysis are q v lg f 410 38 f 0 49 0 05 for the vertical component and q h lg f 390 26 f 0 56 0 04 for the horizontal component where the term after sign represents one standard error for stations within the mississippi embayment with an average sediment depth of 1 km around the memphis metropolitan area estimation of quality factor using the coda normalization method is not well constrained at low frequencies f

typhoon induced upper ocean cooling off northeastern taiwan 1 the ocean cooling off northeastern taiwan induced by typhoons is complicated by the presence of the continental shelf of the east china sea and the kuroshio the cooling is primarily due to the upwelling of the kuroshio s subsurface water which accompanies the kuroshio s intrusion onto the shelf rather than the entrainment mixing generated by the wind the kuroshio s intrusion in this region has a seasonal variation being more substantial in winter than in summer previous studies found that the winter northeasterly monsoon creates an intrusion favored flow pattern while the reversed summer monsoon opposes it this study found that the strong northeast wind accompanied by a typhoon along a certain path could significantly alter the circulations on the shelf an intrusion event will be triggered via a similar mechanism as induced by the winter monsoon but at a faster pace a numerical study and observation data are provided to illustrate this mechanism

surface currents in the tropical atlantic across high density xbt line ax08 1 three temperature sections that cross the tropical atlantic obtained from high density xbt transects are used to identify the major surface currents and to compute their water mass transports the dynamic heights are computed using xbt temperature profiles with salinity derived from historical t s relationships the values of dynamic height estimated from altimeter data used in conjunction with climatological dynamic height fields are within 3 cm of the xbt derived values the error in xbt derived dynamic height introduced by using historical t s relationships instead of actual salinity values are estimated to be of the order of 1 5 cm dynamic height estimates using the actual salinity values underestimate those obtained using historical t s relationships the structure exhibited in the dynamic height and altimeter derived sea height fields do not reveal all the upper ocean currents making these temperature sections presented here critical for computing transports and identifying currents in this region

a lithospheric attenuation model of north america abstract recent moderate sized but strongly felt earthquakes in eastern and central north america have highlighted the important role of the earth s attenuation structure in estimating and predicting local and regional ground motions over the past several years we have been developing methods to use the amplitudes of regional phases pn sn and to invert for the crust and upper mantle attenuation structure in eurasia and have recently started transporting the methodology to north america we now have path coverage for most of north america including canada the united states mexico and portions of the caribbean with the best coverage in the united states after describing the development of the model we discuss the results in the context of the tectonics of the region most notably the large differences between western north america and areas east of the rockies we will then demonstrate the use of the model in a number of applications including estimating reliable moment magnitudes for the wells nevada earthquake sequence the use of the models in strong ground motion prediction for the mineral virginia mainshock and in both discriminating and estimating explosion characteristics depth yield of events at the nevada test site

tropical atlantic sea surface temperature variability and its relation to el nino southern oscillation past analyses of tropical atlantic sea surface temperature variability have suggested a dipole behavior between the northern and southern tropics across the intertropical convergence zone itcz by analyzing an improved 43 year 1950 1992 record of sst smith et al 1996 and other data derived from the comprehensive ocean atmosphere data set coads it is shown that the regions north and south of the itcz are statistically independent of each other at the seasonal to interannual timescales dominating the data confirming the conclusions of houghton and tourre 1992 some dipole behavior does develop weakly during the boreal spring season when there is a tendency for sst anomaly west of angola to be opposite of that in the tropical north atlantic it is further shown that tropical atlantic sst variability is corre lated with pacific e1 nifio southern oscillation enso variability in several regions the ma jor region affected is the north atlantic area of ne trades west of 40ow along 10on 20on and extending into the caribbean there about 50 80 of the anomalous sst variability is associ ated with the pacific enso with atlantic warmings occurring 4 5 months after the mature phases of pacific warm events an analysis of local surface flux fields derived from coads data shows that the enso related atlantic warmings occur as a result of reductions in the surface ne trade wind speeds which in turn reduce latent and sensible heat losses over the region in ques tion as well as cooling due to entrainment this enso connection is best developed during the boreal spring following the most frequent season of maximum enso anomalies in the pacific a region of secondary covariability with enso occurs along the northern edge of the mean itcz position and appears to be associated with northward migrations of the itcz when the north at lantic warmings occur although easterly winds are intensified in the western equatorial atlantic in response to pacific warm events they do not produce strong local changes in sst contrary to expectations from studies based on equatorial dynamics these teleconnected wind anomalies do not give rise to significant correlations of sst in the gulf of guinea with the pacific enso as the teleconnection sequence matures strong se trades at low southern latitudes follow the de velopment of the north atlantic sst anomaly and precede by several months the appearance of weak negative sst anomalies off angola and stronger positive anomalies extending eastward from southern brazil along 15o 30os

lg coda q and its relation to the structure and evolution of continents a global perspective tomographic maps of lg coda q q lg c variation are now available for nearly the entire african eurasian south american and australian continents as well as for the united states q lg c at 1 hz q 0 varies from less than 200 to more than 1000 and q lg c frequency dependence varies between 0 0 and nearly 1 0 q 0 appears to increase in proportion to the length of time that has elapsed since the most recent major episode of tectonic or orogenic activity in any region a plot of q 0 versus time since that activity indicates that a single q 0 time relation approximates most mean q 0 values those that deviate most from the trend lay in australia the arabian peninsula and the east african rift the increase in q 0 with time may be due to a continual increase in crustal shear wave q q caused by the loss of crustal fluids and reduction of crustal permeability following tectonic or orogenic activity extrapolated values of q lg c at 5 hz using q 0 and values measured at 1 hz and assuming that is constant in all regions between 1 and 5 hz show a similar percentage wise increase with times that has elapsed since the most recent activity other factors that can reduce q 0 in continental regions include thick accumulations of sediment especially sandstone and shale of mesozoic age and younger severe velocity gradients at the crust mantle transition and possibly lateral variations in the depth thickness and severity of those gradients severe and large increases of q in the mid crust of some regions can cause relatively large values of even if the frequency dependence of q is small

a back projection method for imaging large scale lateral variations of lg coda q with application to continental africa summary a new method is developed which uses back projection tomography to regionalize large scale lateral variations of coda q for lg waves which have traversed long continental paths successful use of this method requires precise and stable single trace measurements of lg coda q xie nuttli 1988 the method converges rapidly and requires minimal computer storage it also allows quantitative estimation of resolution and error in imaging lateral variations of coda q the spatial resolution of this method is limited by the uneven spatial coverage of the data base by our limited knowledge of lg coda generation and by the trade off between the stability and the spatial resolution of the coda q inversion the method is applied to a large set of digital lg coda data from africa where large scale lateral variations of lg coda q are found to correlate well with major tectonic features most of africa is stable and like other stable regions has relatively high coda q values the lowest values of coda q are associated with the african rift system other regions of low q values include the atlas mountains and cape fold belt regions of mesozoic and younger deformation the lateral variation of frequency dependence of lg coda q correlates in most regions with that of q at 1 hz our analysis of the spatial resolution of this method indicates that the resolving power of lg coda q imaging is comparable to that of velocity tomography using long period surface waves using empirical approaches we estimate that uncertainties in lg coda q and its power law frequency dependence parameter are less than about 60 and about 0 2 respectively for most of africa

attenuation of multiphase surface waves in the basin and range province iii inversion for crustal anelasticity summary a combined inversion forward modelling procedure in which the frequency dependence of shear wave internal friction q 1 is allowed to vary with depth was developed and applied to selected rayleigh wave and lg attenuation data in the basin and range province of the south western united states both q and the frequency dependence of lg waves were used to constrain the models many models can explain rayleigh wave and lg data sets within their uncertainties but at 1 hz most have low values of q 50 80 in the upper 8 km of the crust rapidly increasing values to about 1000 at mid crustal depths and decreasing values at greater depths models which include a layer of higher q values 80 150 in the upper few kilometres of the crust overlying a region of lower q values cannot be precluded by the attenuation data of this study assuming that q varies with frequency as f models for which the frequency dependence is low 0 0 0 1 in the upper crust best explain the data of this study in the lower crust that frequency dependence is not well determined but the models which best explain both the fundamental mode and lg data and produce realistic models of q are characterized at 1 hz by high values of both q and its frequency dependence because of that frequency dependence q may be an order of magnitude lower at a period of 100 s 100 than it is at 1 s 1000 investigations of the effects of changing crustal velocity on values for lg q and its frequency dependence indicate that realistic velocity changes cause only small changes in those values and thus are inconsequential to our results the low q values and their constancy with frequency in the uppermost crust can be explained by fluid flow in a network of cracks in brittle rock increasing q with depth to 10 15 km can be explained by the closing of those cracks due to pressure and their enhanced healing with increasing temperature plastic flow at greater depths may contribute further to the dissipation of cracks and to further increases in q decreasing q values at greater depths can be explained as being the result of increasing temperature increasing content of partial melt enhanced dislocation motion or some combination of these effects

multisatellite observation on upwelling after the passage of typhoon hai tang in the southern east china sea 1 the serial remote sensing based imageries clearly revealed large scale of upwelling within large regional enhancement of chlorophyll a chl a concentration in the southern east china sea ecs after the passage of super typhoon hai tang in july 2005 after the typhoon on 22 july the upwelling area 3 0 mg m3 appeared in the shelf region where the high chl a pattern matched the upwelling in terms of location and time on the other hand a large offshore sst cooling was also observed mainly to the right of typhoon track on 20 july it lasted in a period of 2 3 days this paper provides clear and high resolution evidence that typhoon significant increased upwelling and chl a concentration in the southern ecs

deep seismic reflectivity beneath an intracratonic basin insights into the behavior of the uppermost mantle beneath the illinois basin abstract reflectivity images of the lower crust and uppermost mantle beneath the paleozoic illinois basin have been derived from reprocessing of several hundred kilometers of industry seismic reflection data using extended vibroseis recorrelation the recorrelation was based on extending an originally 4 s correlated record acquired with a 16 s sweep from 14 to 126 hz to the absolute limit of the full 20 s 70 km listening traveltime sub moho reflections are recorded to 18 s two way traveltime unmigrated and are observed on intersecting profiles apparently dipping to the southwest and striking northwest southeast occasional moho reflections are also observed across the profiles 12 s or 38 km while reflectivity in the lower crust is generally marked by intermittent horizontal packages and short gently dipping reflections and diffraction segments the presence of newly observed mantle reflectivity beneath the illinois basin indicates significant uppermost mantle heterogeneity relative to other parts of the usa studied using reflection methods the mantle reflectivity effectively defines an area of anomalous mantle that rests beneath the depocenter of the early paleozoic illinois basin which is itself superimposed over a deeper proterozoic basinal depocenter filtering and inversion of geopotential field data reveal that this anomalous mantle also partially correlates with a positive density anomaly in the upper mantle these correlations suggest that the anomalous mantle zone exerted an influence on the early paleozoic subsidence of the basin perhaps as a buried load due to eclogitization of former lower crust the relatively isolated occurrence of sub moho reflections beneath the basin makes it difficult to uniquely infer their origin however available geologic and geophysical constraints especially from geochemical and geochronological studies of drilled and exposed basement rocks limit the possibilities to 1 remnants or scars of sub crustal processes associated with lithospheric extension or delamination related to the melting of the proterozoic crust that led to the emplacement of the granite rhyolite province that underlies much of usa midcontinent or 2 deformation caused by plate subduction associated with the hypothetical accretion of a juvenile island arc to the pre 1 6 ga southern margin of the laurentian continent

source characterization of nevada test site explosions and western u s earthquakes using lg waves implications for regional source discrimination an investigation is made of the lg waves from 15 nuclear tests at the nevada test site nts and 25 shallow western united states earthquakes to obtain a scheme for discriminating between possible source mechanisms the data were recorded at four broadband stations operated by lawrence livermore national laboratory llnl which encircle the nts the lg wave spectra are modeled through a genetic algorithm search to find optimal values for 1 the seismic moment m o 2 the corner frequency of the amplitude spectrum f c 3 the 1 hz attenuation quality factors q o for all of the paths and 4 the frequency dependence of attenuation along the paths because the inversion solves for the path attenuation characteristics little a priori information is needed for the analysis the resulting m o and f c values are used in conjunction with the m b values as seismic discriminants the populations of earthquakes and explosions have nearly identical relationships between their moments and corner frequencies for earthquakes the relationship is log m o 16 07 2 93 log f c for the set of nts explosions using an earthquake source model the relationship is log m o 15 87 2 76 log f c a source discriminant is found however through a comparison of the moments and m b values this gives a line log m o 10 20 1 16 m b which cleanly separates the earthquake and explosion populations with earthquakes falling above and explosions below the line reliability tests examine the inverse trade off between moments and q o values noise in the lg spectra has a limited effect on the scaling relations

shear wave velocity structure in north america from large scale waveform inversions of surface waves a two step nonlinear and linear inversion is carried out to map the lateral heterogeneity beneath north america using surface wave data the lateral resolution for most areas of the model is of the order of several hundred kilometers the most obvious feature in the tomographic images is the rapid transition between low velocities in the tectonically active region west of the rocky mountains and high velocities in the stable central and eastern shield of north america the model also reveals smaller scale heterogeneous velocity structures a high velocity anomaly is imaged beneath the state of washington that could be explained as the subducting juan de fuca plate beneath the cascades a large low velocity structure extends along the coast from the mendocino to the rivera triple junction and to the continental interior across the southwestern united states and northwestern mexico its shape changes notably with depth this anomaly largely coincides with the part of the margin where no lithosphere is consumed since the subduction has been replaced by a transform fault evidence for a discontinuous subduction of the cocos plate along the middle american trench is found in central mexico a transition is visible from low velocities across the trans mexican volcanic belt tmvb to high velocities beneath the yucatan peninsula two elongated low velocity anomalies beneath the yellowstone plateau and the eastern snake river plain volcanic system and beneath central mexico and the tmvb seem to be associated with magmatism and partial melting another low velocity feature is seen at depths of approximately 200 km beneath florida and the atlantic coastal plain the inversion technique used is based on a linear surface wave scattering theory which gives tomographic images of the relative phase velocity perturbations in four period bands ranging from 40 to 150 s in order to find a smooth reference model a nonlinear inversion based on ray theory is first performed after correcting for the crustal thickness the phase velocity perturbations obtained from the subsequent linear waveform inversion for the different period bands are converted to a three layer model of s velocity perturbations layer 1 25 100 km layer 2 100 200 km layer 3 200 300 km we have applied this method on 275 high quality rayleigh waves recorded by a variety of instruments in north america iris usgs iris ida terrascope rstn sensitivity tests indicate that the lateral resolution is especially good in the densely sampled western continental united states mexico and the gulf of mexico

frequency dependent lg attenuation in the indian platform we use seismograms from regional earthquakes recorded on digital seismographs in peninsular india to determine the frequency dependent q of lg for the indian platform we measure lg attenuation by determining the decay of spectral amplitudes with distance the available data suggest some spatial variation in attenuation but a much denser ray path coverage would be required to validate such observations we therefore combine all the measurements of overlapping regions that span both the shield and intervening terranes to obtain an average value of attenuation for the indian platform lg q 665 10 with the frequency exponent n 0 67 0 03 this average value of lg attenuation for the indian platform is similar to the average for other stable regions of the globe

measurement of frequency dependent lg attenuation in the great basin measurement of the spatial decay of spectral amplitudes of the higher mode seismic surface wave train lg indicates that in the great basin the apparent seismic quality factor q is a function of frequency observations along a 300 km profile recording of a nuclear explosion yield the function q 206 0 68 over the band 0 3 10 0 hz similar analysis using numerous recordings of earthquakes along paths which provide a good average sampling of the great basin crust gives q 214 15 0 54 0 09 for 0 3 5 0 hz if the crustal sampling by lg energy from nuclear explosions surface sources is primarily in the shallow crust as has been suggested then these results indicate a greater frequency dependence of apparent q there than at depth

regional variation of lg coda q in the continental united states and its relation to crustal structure and evolution records from broadband digital stations have allowed us to map regional variations of lg coda q across almost the entire united states using a stacked ratio method we obtained estimates of q 0 lg coda q at 1 hz and its frequency dependence for 218 event station pairs those sets of estimates were inverted using a back projection method to obtain tomographic images showing regional variations of q 0 and q 0 is lowest 250 300 in the california coastal regions and the western part of the basin and range province and highest 650 750 in the northern appalachians and a portion of the central lowlands intermediate values occur in the colorado plateau 300 500 the columbia plateau 300 400 the rocky mountains 450 550 the great plains 500 650 the gulf coastal plain and the southern portion of atlantic coastal plain 400 500 and the portions of the central lowlands surrounding the high q region 500 550 the pattern of q 0 variations suggests that the united states can be divided into two large q provinces one province spans the area from the rocky mountains to the atlantic coast is tectonically stable and exhibits relatively high q 0 the other extends westward from the approximate western margin of the rocky mountains to the pacific coast is tectonically active and exhibits low q 0 the transition from high to low lg coda q in the western united states lies further to the west than does an upper mantle transition for q and electrical resistivity found in earlier studies the difference in q 0 between the western and eastern united states can be attributed to a greater amount of interstitial crustal fluids in the west regions of moderately reduced q within the stable platform often occur where there are accumulations of mesozoic and younger sediments reduced q 0 in the southeastern united states may not be due to anelasticity but may rather be explained by a gradational velocity increase at the crust mantle boundary that causes shear energy to leak into the mantle

lg coda q variations across south america and their relation to crustal evolution nine broadband seismograph stations in south america have provided 389 recordings of lg coda with paths that cover most of the continent lg coda q q0v and frequency dependence values at 1 hz obtained from these records were inverted using back projection tomography to obtain regionalized maps of q0 and the entire western margin of the continent the active andean mountain belt is typified by low q0 250 450 whereas broad regions of high q0 700 1100 span the central brazilian shield and contiguous regions to the north and south intermediate q0 450 700 characterizes the northern patagonia platform and most of the atlantic shield reduced q0 in the atlantic shield may be related to tectonic or igneous activity that occurred during the breakup of gondwanaland during the jurassic period this q distribution is generally consistent with earlier studies where q0 was found to be directly proportional to the time that has elapsed since the most recent episode of major tectonic or orogenic activity in any region reduced q0 in the patagonian platform may however be due to young sediments there

estimation of the coda wave attenuation and geometrical spreading in the new madrid seismic zone using the single backscattering method coda quality factor functions through coda window lengths of 20 30 40 50 and 60 s have been estimated for the new madrid seismic zone nmsz furthermore geometrical spreading functions for distances less than 60 km have been determined in this region at different center frequencies exploiting the coda normalization method a total of 284 triaxial seismograms with good signal to noise ratios snr 5 from broadband stations located in the nmsz were used the database consisted of records from 57 local earthquakes with moment magnitudes of 2 6 4 1 and hypocentral distances less than 200 km q factor values were evaluated at five frequency bands with central frequencies of 1 5 3 6 12 and 24 hz vertical components were utilized to estimate vertical coda q factor values horizontal coda q factor values were determined using the average amount of the q factor values estimated from two orthogonal horizontal components the coda q factor increases with increasing of the coda window length implying that with increasing the depth the coda q factor increases the intermediate values of the q factor and intermediate values of the frequency dependency indicate that the earth s crust and upper mantle beneath the entire nmsz is tectonically a moderate region with a moderate to relatively high degree of heterogeneities the geometrical spreading factors of s wave amplitudes are frequency dependent and determined to be 0 761 0 991 1 271 1 182 and 1 066 for center frequencies of 1 5 3 6 12 and 24 hz respectively at hypocentral distances of 10 60 km the geometrical spreading factors for lower frequencies are not recommended to be used due to the greater impact of the radiation pattern and directivity effect on low frequencies as well as the greater sensitivity of band pass filtered seismograms of small earthquakes to the noise in low frequencies

l g coda q variation across the myanmar arc and its neighboring regions regional seismograms were collected to image the lateral variations of lg coda q at 1 hz q0 and its frequency dependence across burma and its neighboring regions the data include 660 vertical component traces recorded at 39 stations the resulting image indicates that lg coda q at a frequency of 1 hz varies between 100 and 500 lowest q values 250 are found in the eastern indian block from the lg coda q tomography we found that 1 the sagain fault acts as a rough boundary between the eastern indian plate and the three rivers area of the eurasia plate 2 near the eastern himalayan syntaxis higher q value appears in the background of relatively low q which may be the consequence of the northward intrusion of the assam block of the indian plate into the southern qinghai tibet plateau

lg attenuation in the central and eastern united states as revealed by the earthscope transportable array abstract lg waveforms recorded by earthscope s transportable array ta are used to estimate lg q 0 in the central and eastern united states ceus attenuation is calculated based on lg spectral amplitudes filtered at a narrow band from 0 5 to 1 5 hz two station and reverse two station techniques are used to calculate q 0 values 39 events occurring from 2010 to 2012 and ranging from magnitude 3 to magnitude 6 are used in this study 39 258 and 4 627 interstation q 0 values are determined using the two station and reverse two station techniques respectively the results show northeast trending high q 0 regions low attenuation ranging from eastern new mexico to wisconsin regions of low q 0 high attenuation are seen along the minnesota wisconsin border the gulf coastal plain gcp along the south dakota nebraska border and along the oklahoma texas border a positive correlation between heat flow sediment thickness recent tectonic activity fluids and low q 0 was observed areas with low heat flow thin sediment cover no recent tectonic activity and a lack of fluids were observed to have consistently high q 0 these new models use a greater amount of data attain more coverage than previous studies and better constrain attenuation this increase in detail can improve high frequency ground motion predictions of future large earthquakes for more accurate far field hazard assessment and improve the overall understanding of the structure and assemblage of the ceus

regionalization of crustal coda q in the continental united states a contour map of crustal q sub 0 values for the entire united states is presented based on a scattering model to explain the coda waves of local and near regional earthquakes these coda q sub 0 values are in good agreement with q of lg waves data are obtained from over 250 local earthquakes with most magnitudes between 3 0 and 5 0 recorded by 25 wwssn and 27 lrsm stations throughout the continental united states these two sets of data provide a range of frequencies from 0 5 to 3 5 hz a frequency dependence of q is observed in the range of frequencies considered a power law dependence of the form q q sub 0 f f sub 0 sup eta is assumed the value of frequency dependence eta is found to be maximum in the tectonically active western united states and least in the stable regions of the central and south central united states the lowest q sub 0 values are obtained in the western united states with values ranging from 140 to 200 in the coastal plains average crustal q sub 0 values for the basin and range province vary from 200 to 300 increasing gradually to 400 in the colorado plateau region q sub 0 valuesmore in the columbia plateau vary from 200 to 400 q sub 0 values increase very rapidly along the central and southern rocky mountains from 400 to 800 east of the rocky mountains q sub 0 values increase gradually in the interior plains to a maximum value of around 1300 in the mississippi embayment region farther east q sub 0 values decrease gradually to an almost constant value of 1000 along the appalachian mountains coastal regions of eastern and northeastern united states have a crustal q sub 0 value between 900 to 700 regions of north central and gulf coastal plains show low q sub 0 values ranging from 600 to 400 and less the source factor b f sub p a measure of the intensity of scattering was obtained for several different regions of the continental united states regions of high q sub 0 values exhibit low intensity of scattering less

satellite views of the episodic terrestrial material transport to the southern okinawa trough driven by typhoon using satellite derived water transparency alias secchi depth images we found clear signals of terrestrial material transport to the southern okinawa trough triggered by the typhoon morakot in august 2009 three sources were identified one is from the eastern coast of taiwan another is from the western coast of taiwan and the other is from the coast of mainland china carried by northward flows typhoon triggered terrestrial materials from both sides of taiwan s coasts were transported to the region northeast of taiwan moreover the terrestrial material from the coast of mainland china could cross the taiwan strait and be further transported to the region northeast of taiwan these typhoon induced terrestrial materials off northeastern taiwan could then be transported to the southern okinawa trough along the western edge of the kuroshio in addition to the particulate terrestrial material transported nutrients might also be transported to the kuroshio main stream a significant phytoplankton bloom was observed along the kuroshio path for about 300 km off northeast of taiwan our results indicate that episodic cyclone driven terrestrial material transport could be another source of mud in the southern okinawa trough

crustal q structure in the united states from multi mode surface waves determination of q structures are made using a new method which matches observed surface wave spectra with theoretical spectra computed for earthquakes with known fault plane solutions the importance of the method lies in its ability to utilize relatively short paths between a single source and receiver both of which are preferably located within a single geological province the method has been applied to study the regions of the eastern united states the colorado plateau and the basin and range province q models have been obtained through trial and error procedures and with an inversion scheme developed for that purpose models for each region obtained from these two procedures are in good agreement q values in the upper crust as obtained from inversions are 275 for the eastern united states 160 for the colorado plateau and 85 for the basin and range province q values in the lower crust although not well determined must be much higher than upper crustal values in all three regions the conclusions are consistent with those of previous work in which q values in the upper crust of a broad region of the western united states are lower than those of the eastern united states these new results show that substantial variations of q occur in different regions of the western united states the upper crustal q values show an inverse relationship to heat flow values

transient modulation of kuroshio upper layer flow by directly impinging typhoon morakot in east of taiwan in 2009 this study deals with the modulation of the kuroshio upper layer flow kulf in response to the passage of typhoon morakot in 2009 using regional oceanic modeling system roms and in situ measurements from argos drifters and argo floats the analysis of the simulated current fields near the typhoon track revealed an intermittency phenomenon of the kulf which was almost shut down for at least 6 hours the process begun 2 days prior to the approach of typhoon center due to blockage of the kulf by the steadily northerly winds and lasted for more than 2 days simultaneously shifting the kuroshio main stream kms path when the morakot gradually moved closely to the kuroshio the kms shifted vertically from the surface layer to deeper layer of 50 100 m depth and the maximum current speed in the kms decreased from more than 1 3 m s 1 to less than 1 1 m s 1 when the morakot center approached about 100 km to the original position of the kuroshio the kulf spread eastward for 1 5 degrees at 24 n when the morakot center moved to the original position of the kms the kuroshio abruptly rushed with a maximum speed near 1 4 m s 1 meanwhile an offshore cool jet originating from southeastern tip of taiwan was generated and extended northward along the kuroshio in the cool jet the lowest temperature reached about 5 c lower than the ambient waters modeled current variations and the cool jet during the morakot passage were validated by in situ measurements

variability of crustal attenuation in the northeastern united states from lg waves high quality digital seismograms from eight pairs of collocated earthquakes in the northeastern united states were analyzed to determine accurate source spectrum corner frequencies this was accomplished by applying the empirical green s function method to regional pg and lg or sg phases recorded by vertical component seismographs of the u s national seismographic network usnsn and the lamont doherty cooperative seismographic network lcsn stations the frequency band used was 0 5 16 hz for usnsn and 1 30 hz for lcsn records the source spectrum corner frequencies for the eight larger earthquakes of the event pairs magnitudes between mb lg 2 5 4 1 range from about 4 3 to 16 3 hz based on the comer frequencies obtained independently from the empirical green s function analysis sg or lg wave displacement amplitude spectra up to 30 hz were used to determine the crustal average q factors along 87 event station paths these paths crossed diverse tectonic features in the northeastern united states and were in the epicentral distance range of 41 to 1394 km we found that within the northeastern united states the crustal average qlg we obtained was frequency dependent and showed spatial variability which correlated fairly well with the major tectonic features in the region our attenuation measurements indicated low lg attenuation in the adirondack mountains with exposed precambrian grenville basement with qlg 905 f0 40 high lg attenuation in the central appalachian province with qlg 561 586 f0 46 0 47 and an intermediate lg attenuation in northern new england appalachians with q 705 f0 41

lg coda q in australia and its relation to crustal structure and evolution we have determined lg coda q lg c from ground motion recorded at seven broadband stations in australia using a stacked spectral ratio method in spite of the relatively small number of events and less than optimum station coverage we were able to use those data to obtain a tomographic map q lg c and its frequency dependence at 1 hz for almost the entire island continent