regional source scaling of the 9 october 2006 underground nuclear explosion in north korea abstract the 9 october 2006 underground nuclear explosion une test in north korea was well monitored by dense regional seismic stations in south korea japan and china this observation allows extensive investigation of the regional source properties of the une the moment for isotropically radiated energy from the une is estimated to be 2 92 10 14 n m source spectra of major regional phases from the une are studied by inverting for apparent moments corner frequencies overshoot parameters attenuation factors and frequency power dependence parameters the overshoot parameters of p phases from the une are estimated to be high while those of s phases are estimated to be significantly low the inverted source spectra agree well with conventional models the low overshoot parameters of s phases suggest that their excitation sources may be different from those for pn and pg it is shown that pn lg and pg lg amplitude ratios are useful for discriminating between unes and natural earthquakes in the frequencies of 1 8 hz

modelling the mid late holocene evolution of the huelva estuary and its human colonization south western spain abstract the major changes that occurred in the southwestern estuaries of the spanish atlantic coast during the last 6500 yr bp were simultaneous to human settlement and therefore the understanding of their coastal evolution will help interpreting human patterns in these areas the study of the morpho sedimentary features of new outcrops appearing in the middle sector of saltes island huelva estuary spain has been used to develop a model to understand the complex evolution of sand barriers than can be applied to similar inlets along the atlantic iberian coast the first human settlements 6000 4000 yr bp in the early huelva estuary tinto and odiel rivers were located in the ancient coastal banks or in the nearby hills from 4000 yr bp onwards the estuarine sediments started to emerge as sand barriers and chenier plains prograding towards the mouth as the littoral strands stabilized morphologically they were colonized by human settlements in successive periods the oldest inland almendral and more recent outward cascajera the study of the upper sedimentary layers of la cascajera barrier display a tempestitic sequence of landward progradational washover fans the calibrated and modelled ams dates in marine shells provide a storminess time range between the second half of first century bce and the entire first century ce sedimentary records are useful to evaluate environmental changes either from natural or anthropogenic causes such as global and climate change the interrelationship between the archaeological findings mainly salting fish factories and old ports and the morpho sedimentary evolution at the mouth of the tinto and odiel rivers allows us to highlight not only the huelva estuary s dynamics evolution but also the possible regional patterns of human habitation from the beginning of the present sea level highstand middle holocene

the complete synthesis of seismic crustal phases at regional distances using a new method to evaluate green s functions for elastic layered media we compute complete synthetic seismograms at regional distances for an earthquake in the earth crust we choose as source parameters the ones inferred for an earthquake in central france and compare the computed seismograms to the ones recorded at several short period stations of the french seismic network the major features of the records including complexity and duration are well reproduced by the synthetics lg waves which are the prominant phase are shown to be guided waves made up of sh and sv waves incident on the moho at angles of incidence more grazing than the critical angle and multiply reflected within the crust the length of the computed lg wave coda extends between group velocities of 3 5 and 2 8 km s and is in good agreement with the data

long period regional wave moment tensor inversion for earthquakes in the western united states source parameters of moderate to large size mw 4 5 earthquakes in the western united states from 1992 to 1994 are determined by point source moment tensor inversion of complete long period t 35 50 s ground motions recorded at regional distances 1 12 stable long period signals are obtained by low pass filtering records from the very broadband seismometers recently deployed in several networks in the western united states these signals are dominated by fundamental mode rayleigh and love waves which have very simple waveforms due to the limited dispersion on the short paths to regional stations since long period motions are relatively insensitive to the attenuation model and crustal structure used in the inversion they provide robust constraints on the seismic moment and faulting geometry as long as adequate azimuthal coverage is available comparisons of solutions for 21 events with results of other regional and teleseismic wave inversions are made to assess the model dependence and uncertainties of our regional centroid moment tensor rcmt solutions rcmt inversion has limited source depth resolution for shallow crustal events but the focal mechanism and seismic moment determinations prove quite stable over a range of source depths in the crust as well as over a range of crustal propagation models simultaneous waveform inversion of shorter period body wave signals can improve the source depth resolution by applying path corrections for heterogeneous crustal structure shorter period surface wave energy can also be inverted allowing the methodology to be extended to lower magnitude regional events as well the rcmt procedure requires minimal signal processing only a sparse broadband network and a simple laterally homogeneous propagation model thus it can readily be automated and applied in near real time to events in the magnitude range from 4 5 to 7 5 distributed over an area as large as the western united states

spectral discrimination between nts explosions and western united states earthquakes at regional distances spectral ratio disciminants are applied to 72 western united states earthquakes and 64 nts explosions recorded at four broadband seismic stations surrounding nts the ratio of the energy in the 1 to 2 and 6 to 8 hz bands for pn pg and lg is calculated and a simple distance correction applied to the data the spectral ratio appears to have potential as a disciminant at relatively small magnitudes 3 0 4 5 to 5 0 this may be due to uncertainties in the apparent source time function for explosions these complications may be due to changes in the dynamic response of the material in the near source region as a function of overburden pressure effects of secondary sources or to variations in regional phase excitation with depth

the end cretaceous in the southwestern tethys elles tunisia orbital calibration of paleoenvironmental events before the mass extinction an integrated study of magnetic mass susceptibility ms bulk stable isotopes and calcareous nannofossil paleoecological changes is undertaken on the late maastrichtian of the elles section tunisia spanning the last ca 1 myr of the cretaceous a cyclostratigraphic analysis reveals the presence of milankovitch frequencies and is used for proposal of two distinct orbital age models and to provide ages of important stratigraphic horizons relative to the age of the cretaceous paleogene boundary k pgb principal component analysis pca performed on the nannofossil assemblage reveal two main factors pca1 mostly representing fluctuations of d rotatorius p stoveri lithraphidites spp retecapsa spp staurolithites spp micula spp and pca2 mostly representing fluctuations of a regularis c ehrenbergii micula spp rhagodiscus spp w barnesiae and zeugrhabdotus spp variations in pca1 and pca2 match changes in bulk 13c and 18o respectively and suggest changes in surface water fertility and temperatures and associated stress the variations in abundances of high latitude taxa and the warm water species micula murus and in bulk 18o delineate fast changes in sea surface paleotemperatures as in many other sites an end maastrichtian greenhouse warming is highlighted followed by a short cooling and an additional warm pulse in the last 30 kyr of the maastrichtian which has rarely been documented so far orbital tuning of the delineated climatic events is proposed following the two different age models calcareous nannofossil assemblages highlight a decrease in surface water nutriency but their species richness remains high through the latest maastrichtian indicating in tunisia a weak impact of deccan volcanism on calcareous nannoplankton diversity before the mass extinction

lg wave propagation in a laterally varying crust and the distribution of the apparent quality factor in central france the aim of this study is to evaluate the sensitix ity of lg waves to lateral changes of the earth s structure considering a simple model of uplift of the moho numerical simulations show that the geometrical attenuation of lg is not much affected by a smooth anomaly of the moho depth on the other hand the passing of the lg wave through the region of the moho uplift results in a clear deterioration of the wave shapes which confirms the occurrence of mode conversions the presence of an overlying sedimentary basin causes a local amplification of lg above the basin itself and the appearance behind the basin of a secondary surface wave guided in the sediments the effect of the basin on the lg wave is found to be reasonably taken into account by applying a local amplification function to the data we use a data set consisting of records of lg phases in france to test the conclusions of our numerical study the mapping of the apparent quality factor computed from lg at different frequencies confirms the interpretation of the strong attenuation of s waves around i hz in terms of scattering and shows the weak sensitivity of the amplitude of lg to smooth changes in the depth of the moho

analysis of seismic discrimination capabilities using regional data from western united states events additional studies have been conducted to help verify the findings of previous investigations cf murphy and bennett 1982 which indicated that spectral differences in short period regional phases may be diagnostic of source type for nevada test site nts explosions and nearby earthquakes recorded at tonto forest observatory in arizona regional phase signals from two additional stations the uinta basin observatory array in utah and the blue mountains observatory array in oregon and from supplemental events including aftershocks of the 1966 caliente nevada earthquake have been analyzed these stations are at epicentral distances of 430 to 530 km for tonto forest observatory 520 to 670 km for uinta basin observatory and 870 to 880 km for blue mountains observatory with the near ranges representing the distances to the caliente source area and the far ranges to the average nts source receiver distances this enhanced data base included 50 earthquakes within about 150 km of nts and 35 nts explosions recorded at one or more stations the events cover a magnitude range from about 2 8 to 5 2 mb with the majority of earthquakes concentrated in the lower half of that range the current investigation essentially corroborated our previous findings that comparison of simple peak amplitude measurements of regional p and lg phases did not consistently discriminate between earthquakes and explosions this discriminant breakdown appears to be related to variability in excitation of regional phases from similar sources which has been dramatically illustrated by observations from the 1966 caliente aftershocks these events produced large variations in the relative amplitudes of pg and lg signals even though the events were spatially restricted to a small zone in contrast the lg spectral ratio discriminant measure defined in the previous study continued to provide reliable distinction between the earthquake and explosion sources for data observed at all three stations the discrimination capability of the spectral ratio prevails in spite of the evident mechanism variability between earthquakes and shifts in the discrimination threshold between stations apparently related to attenuation differences along the propagation paths

attenuation of high frequency earthquake waves in south america earlier attenuation studies for the south american continent indicate that for sn and lg waves there is low attenuation in the shield region east of the andes whereas in the west of south america with some exceptions there is high attenuation those studies however were nonquantitative in this study theq0 1 hz values for lg waves for south america are presented based on a scattering model ofaki 1969 as extended byherrmann 1980 for the coda waves of shallow local and near regional earthquakes the results of the codaq method are compared with those obtained bynuttli s method 1973 theseq0 values are in good agreement with the apparentq0 of lg waves obtained by the latter method the data were obtained from over 100 local and regional earthquakes recorded by 12 wwssn stations throughout continental south america they provided a range of frequencies from 0 4 to 1 4 hz for which the frequency dependence ofq was investigated by assumingq q0 f f0 the observed data indicate that the tectonic region of western south america is characterized by lowq0 and a large frequency dependent factor the values ranging from 150 to 350 and 0 4 to 0 7 respectively theq0 values increase in the shield region east of the andes but frequency dependence decreases the average crustalq0 for north and central argentina ranges from 420 to 580 and ranges from 0 2 to 0 3 theq0 is larger in the brazil region ranging from 580 to 980 and varies from 0 0 to 0 2 in the lower attenuation region of eastern south america higher values of attenuation correlate with greater thickness of the sedimentary layers

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 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

marine mollusc exploitation in mediterranean prehistory an overview abstract marine molluscs have been recovered from sites around the mediterranean sea dating as far back as the lower palaeolithic when hominins might have started consuming them ca 300 ka during the middle palaeolithic and the early upper palaeolithic humans homo neanderthalensis and homo sapiens ate molluscs at many sites across the mediterranean at least as early as the last interglacial although the scale of this exploitation is still unclear due to biases produced in the coastal archaeological record by late glacial and post glacial sea level rise the exploitation of marine molluscs apparently increased in the late glacial and early holocene when humans collected them in relatively large quantities and from all available ecosystems the consumption of shellfish and of other small animals aquatic and continental probably contributed to the success of the flexible and opportunistic subsistence strategies adopted by mediterranean hunter gatherers for much of prehistory this is particularly evident in later foraging economic systems i e late upper palaeolithic and mesolithic in which coastal resources probably acted as buffers against the negative outcomes of environmental and anthropogenic impacts on available resources

effects of tidal amplitude on intertidal resource availability and dispersal pressure in prehistoric human coastal populations the mediterranean atlantic transition abstract in this paper i argue that there is a growing body of evidence supporting an increasingly central position of coastal environments in human evolution and dispersals rather than as merely peripheral habitats eustatic fluctuations during glacial cycles have meant that most prehistoric coastlines are now underwater and lack of evidence to date of a close relationship between people and the coast can be most plausibly ascribed to the limited studies so far on submerged sites coastal environments provide high diversity in food resources consisting of multiple ecotones in close proximity which reduces the need to forage widely one of the richest and most easily exploited coastal resources by human populations living on the coast are molluscs from marine rocky intertidal communities which recent evidence has highlighted as important as far back as the middle palaeolithic however the density of these resources is limited by a number of factors and this varies geographically one of the main large scale factors limiting rocky intertidal mollusc densities is tidal amplitude beyond which smaller scale local factors such as exposure to wave action and shore aspect further affect species distributions the area around the strait of gibraltar is used as a case study of an area which is affected by large variations in tidal amplitudes thus allowing for quantitative comparisons between taxonomically and climatically similar regions shorelines along the mediterranean coast with reduced tidal amplitudes exhibit compressed zonations and harbour fewer macro mollusc individuals with the reverse being the case along the atlantic coast which has significantly larger tides data from middle and upper palaeolithic sites along the strait are used to establish harvested species and present day data are used to model the potential distributions and associated variables such as calorific returns of key food species an optimal foraging model is used to explore the effects of differential levels of resource availability along these coastlines results suggest that the nature and variability of the coastline has a direct influence on the tempo and mode of subsistence strategy followed and whether certain strategies can be adopted at all the possible implications of these biogeographical distributions for foraging economics dispersals and social structures in homo are discussed

genesis and occupancy of a shell midden on parana state coast brazil abstract the publications related to pedological characterization of shell middens are rare and there are no comprehensive studies the objective of the present study was to understand habits and intensity of seasonal human occupancies and genesis of stratigraphic levels of an archaeological site on parana state coast brazil the formation of the shell midden by hunter fisher gatherer groups over thousands of years followed only a few patterns of interaction with the environment which would facilitate the studies of correlations with other middens of the brazilian coast in addition to strategies of searching food the amerindian also diversified their activities to improve life quality including cooking certain foods and the placement of insulating material on the midden the evolution of the genesis of layers was much more dependent on the depositional period than the post depositional interval during the post depositional period only the formation of silicate in the clay fraction of the more superficial layers was favored

regional moments energy levels and a new discriminant teleseismic observations of explosions tend to be richer in short period energy than are earthquakes thus the effectiveness of themb ms discriminant at regional distances the same basic separation occurs for smaller events in terms ofml m0 woodset al 1993 andmb m0 patton andwalter 1993 while these studies demonstrate the basic differences in excitation they suffer in practical application because of the detailed information required in the retrieval ofm0 in this paper we introduce a new method of discrimination based on the energy strength me from broadband regional records that appears to be effective and efficient in this method all events are processed as earthquakes and explosions are distinguished by their stronger energy levels relative to their long period amplitudes results from 29 events recorded by terrascope sampling 15 explosions from nts and 14 earthquakes from the southwestern united states are represented indicating complete separation 45 data points ml 3 6 is the smallest event examined to date but the method can probably be extended to even smaller levels in calibrated regions

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

using archaeological shell middens as a proxy for past local coastal upwelling in northern chile abstract shell middens large heaps of refuse materials that are often interspersed with burials hearths and other cultural features provide important data regarding the lifestyles of past coastal and maritime dwellers despite the abundance of organic materials radiocarbon ages from shell middens can be a challenge to interpret because marine shells are depleted in radiocarbon with respect to their contemporaneous atmosphere known as the reservoir effect r this issue is particularly problematic in regions like the coastal atacama desert where the upwelling of subsurface radiocarbon depleted waters creates a shell local reservoir effect r with a time variable intrinsic uncertainty here we review and discuss how the dating of diverse materials from these deposits including the shells themselves can reveal large shifts between the terrestrial atmospheric and marine carbon cycles furthermore a chronology of such shifts can be used as a proxy of upwelling intensity and to help establish the duration of strong versus weak local upwelling episodes to test and evaluate these ideas we present a chronology of r and r variations from a 2 m shell midden sequence from caleta vitor in northern chile that spans the middle holocene which remains underrepresented by regional r values the 2000 y sequence of caleta vitor located onshore from a major upwelling center displays dramatic shifts in radiocarbon reservoir effects which we hypothesize are linked to strong changes in the intensity of local upwelling further replication of such archaeomalacological records will be key for not only solving methodological problems regarding the dating of coastal sites but can provide further insights into the evolving terrestrial and marine carbon cycles and how these relate to past climate change

a study of ground motion attenuation in the southern great basin nevada california using several techniques for estimates of qs log a 0 and coda q as a first step in the assessment of the earthquake hazard in the southern great basin of nevada california this study evaluates the attenuation of peak vertical ground motions using a number of different regression models applied to unfiltered and band pass filtered ground motion data these data are concentrated in the distance range 10 250 km the regression models include parameters to account for geometric spreading anelastic attenuation with a power law frequency dependence source size and station site effects we find that the data are most consistent with an essentially frequency independent q and a geometric spreading coefficient less than 1 0 regressions are also performed on vertical component peak amplitudes reexpressed as pseudo wood anderson peak amplitude estimates pwa permitting comparison with earlier work that used wood anderson wa data from california both of these results show that q values in this region are high relative to california having values in the range 700 900 over the frequency band 1 10 hz comparison of ml magnitudes from stations brk and pas for earthquakes in the southern great basin shows that these two stations report magnitudes with differences that are distance dependent this bias suggests that the richter log a0 curve appropriate to california is too steep for earthquakes occurring in southern nevada a result implicitly supporting our finding that q values are higher than those in california the pwa attenuation functions derived from our data also indicate that local magnitudes reported by california observatories for earthquakes in this region may be overestimated by as much as 0 8 magnitude units in some cases both of these results will have an effect on the assessment of the earthquake hazard in this region the robustness of our regression technique to extract the correct geometric spreading coefficient n and anelastic attenuation q is tested by applying the technique to simulated data computed with given n and q values using a stochastic modeling technique we generate suites of seismograms for the distance range 10 200 km and for both wa and short period vertical component seismometers regressions on the peak amplitudes from these records show that our regression model extracts values of n and q approximately equal to the input values for either low q california attenuation or high q southern nevada attenuation regressions on stochastically modeled wa and pwa amplitudes also provides a method of evaluating differences in magnitudes from wa and pwa amplitudes due to recording instrument response characteristics alone these results indicate a difference between mlwa and mlpwa equal to 0 15 magnitude units which we term the residual instrument correction in contrast to the peak amplitude results coda q determinations using the single scatterer theory indicate that qc values are dependent on source type and are proportional to p where p 0 8 to 1 0 this result suggests that a difference exists between attenuation mechanisms for direct waves and backscattered waves in this region

a multidisciplinary analysis of shell deposits from saltes island sw spain the origin of a new roman shell midden abstract the analysis of shell deposits eroded by a ebb tide channel on saltes island tinto odiel estuary sw spain resulted in the identification of a new shell midden associated with the activity of a nearby roman factory over the 4th 5th centuries ce this midden differs from other old shell deposits sandy tidal flats cheniers washover fans in several features a its malacological content dominated by edible species mainly the bivalve glycymeris nummaria and differentiated by statistical analysis b a partial selection and better conservation of glycymeris nummaria linnaeus its most abundant species c the absence of microfauna which implies a previous washing to its final deposit and d an age concordant with the one deduced from the roman amphoraic remains found in this area and subsequent to the washover fans on whom it was deposited all these features together with the absence of both anthropic fractures or cooking would indicate that this roman shell midden was the end result of a trawling on subtidal glycymeris rich sandy bottoms with adjacent grasslands where the gastropod bittium reticulatum da costa was the most abundant mollusc this gastropod is the dominant species in the remaining shell deposits

the shape of ground motion attenuation curves in southeastern canada the shape of the attenuation curve of the fourier spectrum of acceleration is established for southeastern canada from empirical data the dataset is comprised of 1200 digital vertical component seismograms from 100 earthquakes recorded on 30 stations of the eastern canada telemetered network the distance range of the observations is 10 to 1700 km focal depths are from 5 to 30 km results indicate that the attenuation curve has three distinct sections at distances less than 70 km corresponding to attenuation of the direct wave amplitudes decay slightly more rapidly than 1 r r 1 1 between 70 and 130 km where the direct wave is joined by sms spectral amplitudes are approximately constant beyond 130 km corresponding to the lg phase amplitudes decay at a rate that is consistent with r 0 5 and q 670 f 0 33 the findings support the hypothesis of burger et al 1987 that postcritical reflections from the moho discontinuity play an important role in determining the shape of the attenuation curve however the influence of sms is subtle allowing the shape to be approximated by simple functional forms for example the commonly assumed bilinear form r 1 r 0 5 with frequency dependent q fits well if the transition from direct wave to lg spreading is placed at approximately 60 km a linear form r 1 over all distances with constant q 2000 also provides a satisfactory fit overall we find little evidence for the dependence of attenuation on focal depth or tectonic province

modeling some empirical vertical component lg relations abstract higher mode surface wave theory is used to model the vertical component lg wave observed in eastern north america at regional distances tests of the model are made to determine whether it is capable of describing empirical spectral scaling laws spatial attenuation and peak time domain lg amplitudes it is found that a simple crustal model and a rough estimate of crustal qb are all that are required to accomplish this good results are obtained if the average crustal qp is equated to the coda q of the same frequency introduction the lg wave is a wave observed on short period seismograms of local and regional seismic events which travels with a group velocity of approximately 3 5 km sec in the central united states it is usually the largest arrival on the seismogram which makes it suitable for defining a magnitude scale nuttli 1973 herrmann and nuttli 1982 as part of developing the magnitude scale there have been many studies on the spatial attenuation of the lg wave nuttli 1973 street 1976 bollinger 1979 singh and herrmann 1982 the lg wave is usually thought of as a superposition of higher mode surface waves propagating within the crustal wave guide herrmann and nuttli 1975a b attempted to deterministically model observed lg amplitudes in terms of focal mechanism focal depth and seismic moment using surface wave techniques they were limited by their inability to compute surface wave eigenfunctions at frequencies greater than 0 5 hz however their results were encouraging harkrider 1979 drawing upon the work of apsel 1979 discovered a way to compute surface wave energy integrals of the higher modes very precisely bache

source spectra for the 1988 saguenay quebec earthquakes abstract source spectra are obtained for the 1988 saguenay quebec earthquake m n 6 5 its foreshock m n 4 8 and largest aftershock m n 4 1 using recordings from analog and digital seismographs on rock sites at epicentral distances from 40 to 700 km the source spectra of the foreshock and the aftershock are well matched by a single corner frequency 2 model with seismic moments of 2 2 10 22 and 2 2 10 21 dyne cm respectively and a stress parameter of 65 bars for both events by contrast the spectrum of the mainshock differs dramatically from this simple shape a stress parameter of 500 bars is required to match the observed high frequency amplitudes using the seismic moment determined from teleseismic observations as a constraint this single corner frequency model however overestimates amplitudes at frequencies near 1 hz by a factor of about 2 the relative radiation of short and long period energy for the mainshock is inconsistent with that from other intraplate earthquakes the fore and aftershocks appear typical in this regard the extraction of source spectra from the regional data required a careful examination of attenuation azimuthal variations were observed with the attenuation being most severe to the southeast normal to the st lawrence valley and the dominant structural grain of the region the st lawrence river coincides in part with the boundary between the grenville and appalachian tectonic provinces and the difference in attenuation may be related to the difference in tectonic province the distribution of data however makes it difficult to obtain good estimates of the attenuation in each province lumping the data from both provinces and the three earthquakes together results in an anelastic attenuation factor given by q 755 f 0 5 for frequencies f from 0 6 to 18 hz using data at distances r beyond 100 km from the sources and assuming 1 r geometrical spreading this attenuation is similar to that obtained in a number of other studies in the general area three component recordings were available at a few stations and from these the following frequency dependent ratio of horizontal to vertical motion was obtained hiv 1 14 0 118 f 0 00638 f 2 for frequencies from 0 2 to 15 hz different methods of correcting observations for attenuation in order to derive source spectra were examined source spectra derived by simple regression analyses of observed data assuming a uniform medium are very similar to those based on a more complicated synthetic seismogram correction which accounts for wave propagation in a layered earth

a new mechanism for chenier development and a facies model of the saltes island chenier plain sw spain abstract the scientific literature describes two types of cheniers these two types differ in the origin of the coarse sediments that constitute the ridge and the relative significance of the transversal and longitudinal wave transport in both cases storm waves are described as the main factor responsible of the origin and development and both final facies are characterized by ridges of coarse sediments above the finer sediments of a tidal flat the odiel tinto estuary is one of the most significant estuarine systems of the mesotidal huelva coast on the northwestern portion of the gulf of cadiz and saltes island is a part of the closure history of the estuarine system previous works on saltes island described the surficial disposition of sandy landforms as a classic ridge chain or a barrier island succession nevertheless an architectural scheme based on a vibracore study shows a disposition that accord to the typical chenier plain facies model this disagreement was the basis for a controversy about the origin of the ridges in this study historical nautical charts and aerial photographs document the evolution of the last of these cheniers during the past 200 years in contrast to the accepted models of chenier evolution the cheniers of saltes island migrated on the tidal flat but did not evolve only during storms indeed their development occurred mainly during high spring tides the data presented in this paper are used as the basis for a new conceptual model of chenier generation and evolution the model consists of a migration of sand bars in a similar way to the classic beach ridges with the difference that in our case the bars migrate over a tidal flat from a local point of view this paper removes the controversy about the origin of the island s geomorphology but from a global point of view this mechanism can explain certain chenier plains in estuarine mouths located in other coasts of the world

late holocene morphodynamics in the littoral zone of the iwik peninsula area banc d arguin mauritania abstract in the littoral zone of the banc d arguin both littoral sedimentary units and man made deposits shell middens abound they were formed during the late holocene after the final onset of the post glacial transgression here a geo archaeological approach is used to study them the geomorphological and sedimentological characteristics of the coastal features define two distinct coastal sedimentary units in the iwik aouatil zone between an ancient shoreline which formed on the tafaritian substratum ca 6 7 5 7 cal ka bp and the present one i very extensive sand flats and ii linear relief features both covered by a thin veneer of anthropogenic anadara senilis shell middens they developed under a stable sea level regime the sand flats expanded at variable rates throughout the period the linear relief features represent beach barriers and coastal dunes which can be dated archaeologically thanks to the superimposed shell middens supplemented by 14 c dating two series of linear sedimentary units are identified first a complex north south system of dunes and hook ended sand barriers developed from 4 8 to 4 1 cal ka bp and secondly two regular and linear beach barriers developed between 3 7 and 3 3 cal ka bp their morphological characteristics suggest that they were generated through littoral drift processes directional changes observed between the first and the second groups demonstrate that the wave refraction pattern was dramatically modified after the closure of the strait between the former iwik island and the land a comparison with the nearby jerf el oustani coastal area in the late holocene shows that both sites shared similarities in depositional patterns but also differences in the chronology of the sedimentary units processes involved in the development of the linear units are indicative of the enhancement of both sand influx and longshore drift due to climatic change

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

source estimation from broadband regional seismograms recently developed source inversion techniques do not take full advantage of the broadband nature of regional seismograms the reason is that green s functions generated from flat layered models are not correct for the complicated propagational phenomena associated with realistic crustal structure the inversion is usually performed by removing short periods and inverting only selected portions of the records in this article we introduce a source estimation technique that allows for better use of the entire broadband record when only imperfect green s function are available the procedure desensitizes the timing between the principal crustal arrivals by fitting portions of the green s functions independently the preferred source is the orientation that minimizes the average l1 and l2 norms in term of the four parameters m 0 strike dip and rake the l2 error emphasizes the longer period surface waves while the l1 error weights the shorter period body waves we obtain estimates of duration by modeling long period and broadband signals the depth determination can be obtained directly from the surface reflected phases sp mp or ss ms or by cycling through the depth dependent green s functions in addition to the source parameters we obtain t phase alignments shifts that can be used as green s function corrections for relocating other events or as a guide to deriving new crustal models

ml m0 as a regional seismic discriminant the m b m s ratio determined by teleseismic observations has proven to be an effective discriminant for explosive sources tend to be significantly richer in short period energy than are earthquakes unfortunately this method is limited by the detection threshold of teleseismic surface waves however recent advances in instrumentation allowing low amplitude surface wave measurements coupled with new analytical techniques make it feasible to use regional waveform data to determine the long period source excitation level of low magnitude events we propose using the ratio of m l local magnitude to m 0 scalar seismic moment as an analogous regional discriminant we applied this criterion to a data set of 299 earthquakes and 178 explosions and found that this ratio seems to be diagnostic of source type for a given m 0 the m l of an explosion is more than 0 5 magnitude units larger than that of an earthquake this separation of populations with respect to source type can be attributed to the fact that m l is a short period 1 hz energy measurement whereas seismic moment is determined from long period body wave phases period 4 s and surface waves 10 to 40 sec using regional stations with sources 200 to 600 km away the effective threshold for magnitude measurements for this discriminant is found to be m l 3 1 for earthquakes and m l 3 6 for explosions this method does require the determination of regional crustal models and path calibrations from master events or by other means

marine resources exploitation by palaeolithic hunter fisher gatherers and neolithic tribal societies in the historical region of the strait of gibraltar this work has been financially supported by the benzu project spanish ministry of culture and ceuta government158 08 pv benzu cv the project dges har2008 06477 c03 02 the aecid hispanic moroccan projects pci a 2893 05 a 6317 06 and a 010823 07 and junta de andalucia project p07 hum 03015 authors are grateful to carol and paul beven and ana durante for their editorial assistance and to the anonymous referees for their helpful suggestions also we are grateful to ivan briz and marco madella for the corrections and suggestions

propagation and attenuation characteristics of the crustal phase lg thelg wave consists of the superposition ofs waves supercritically reflected and thus trapped in the crust this mode of propagation explains the strong amplitude of this phase and the large distance range in which it is observed the numerical simulation leads to successful comparison between observed seismograms in stable continental areas and synthetics computed for simple standard crustal models in regions with strong lateral variations the influence of large scale heterogeneities on thelg amplitude is not yet clearly established in terms of the geometrical characteristics of the crustal structure

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

moment magnitude determination for local and regional earthquakes based on source spectra we investigated the use of an automated routine to determine moment magnitudes from the displacement spectra of local and regional earthquakes two algorithms a genetic algorithm and a converging grid search were developed and tested with earthquake data from mexico norway and deception island antarctica it was found that compared with manual analysis the algorithms give reliable automatic moment magnitude m w estimates in the range 1 m 8 the converging grid search appeared to be more cost effective than the genetic algorithm m w at local and regional distances seems superior to amplitude based magnitudes that saturate for large earthquakes the application of the automated algorithm in near real time may help to obtain a nonsaturated magnitude estimate in the case of a large earthquake immediately after the earthquake has occurred also the method can be useful for processing large amounts of data manuscript received 27 july 2001

using foraminifera to distinguish between natural and cultural shell deposits in coastal eastern australia foraminifera are single cell protozoa that are ubiquitous in marine environments although the hard casings or tests of foraminifera are routinely studied in the earth sciences they have been little studied by archaeologists despite their potential to contribute to understandings of coastal site formation processes and palaeoenvironments in this study techniques and methods of foraminiferal analysis are developed and applied to the problem of distinguishing between natural and cultural marine shell deposits using the mort creek site complex central queensland australia as a case study results allow separation of natural and cultural deposits based on foraminiferal density natural deposits were found to have 1000 foraminifera per 100 g of sediment while cultural deposits exhibited 50 foraminifera per 100 g of sediment results allow us to better understand site formation processes at the mort creek site complex and highlight the potential of foraminiferal analyses in the interpretation of terrestrial marine deposits

multimodal function optimization with a niching genetic algorithm a seismological example abstract we present a variant of a traditional genetic algorithm known as a niching genetic algorithm nga which is effective at multimodal function optimization such an algorithm is useful for geophysical inverse problems that contain more than one distinct solution we illustrate the utility of an nga via a multimodal seismological inverse problem the inversion of teleseismic body waves for the source parameters of the m w 7 2 kuril islands event of 2 february 1996 we assume the source to be a pure double couple event and so parametrize our models in terms of strike dip and slip guaranteeing that two global minima exist one of which represents the fault plane and the other the auxiliary plane we use ray theory to compute the fundamental p and sh synthetic seismograms for a given source receiver geometry the synthetics for an arbitrary fault orientation are produced by taking linear combinations of these fundamentals yielding a computationally fast forward problem the nga is successful at determining that two major solutions exist and at maintaining the solutions in a steady state several inferior solutions representing local minima of the objective function are found as well the two best focal solutions we find for the kuril islands event are very nearly conjugate planes and are consistent with the focal planes reported by the harvard cmt project the solutions indicate thrust movement on a moderately dipping fault a source typical of the convergent margin near the kuril islands

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

corner frequency scaling of regional seismic phases for underground nuclear explosions at the nevada test site model fits are used to estimate source spectral corner frequencies of regional seismic phases pn pg and lg from underground nuclear explosions unes at the nevada test site nts based on recordings by lawrence livermore national laboratory llnl nts network stations the spectra are corrected for instrument response distance and station effects and then network averaged explicit information regarding geophysical working point properties depth of burial and some announced yields for nts explosions springer et al 2002 is utilized for the spectral modeling scaling of pn pg and lg corner frequencies with source yield is examined for sets of explosions at yucca flat pahute mesa and rainier mesa with similar material properties medium type density velocities and gas porosity the unes are limited to those in media with gas porosity of 10 or less so that a source spectral model with a rolloff of f 2 is applicable model comparisons are also examined for regional p lg discriminants a key result is that lg corner frequencies for ntsunes exhibit similar scaling with source size as for p waves but shifted lower analogous to observations by fisk 2006 for the lop nor semipalatinsk and novaya zemlya test sites this appears to corroborate an important effect that is that major contributions to s wave generation by explosions occur near the source with a similar length scale comparable to the elastic radius as for p waves from explosions although the explicit physical mechanism is not yet understood the implications are important regarding where and perhaps how s waves are predominantly generated by explosions a related key result is that the increasing separation of p lg at higher frequencies between nts explosions and earthquakes has a consistent model based explanation as at other nuclear test sites in terms of the difference between explosion p and s corner frequencies

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

regional seismic discriminants using wave train energy ratios we have examined broadband regional waveforms of recent since 1988 nevada test site nts underground explosions and earthquakes throughout the southwestern united states and baja mexico recorded by terrascope and other iris stations in order to characterize seismic sources for the purposes of event identification as expected earthquakes tended to be richer in long period surface wave and short period shear wave energy relative to explosions of comparable p wave strength also explosions in general were found to be richer in 1 to 6 sec surface wave rg energy and other late arriving coda energy than were earthquakes most earthquakes show relatively little long period t 6 sec rg and surface wave coda energy which we attribute to their deeper source depths whereas known shallow earthquakes do exhibit these phases we have developed several seismic discriminants based on our observations the most promising discriminant is the ratio of short period f 1 0 hz vertical component pnl wave train energy esppz to long period 0 05 to 0 167 hz three component surface wave energy e lp 3 for this ratio explosions tend to have a higher value than do earthquakes this discriminant works on the same premise as the teleseismic mb ms ratio for which earthquakes are richer in long period surface wave energy relative to explosions with the same body wave magnitude the long period passband was chosen to limit the effect of longer period noise and to remove the effect of the coda surface waves another potential discriminant examined is the ratio of short period f 1 0 hz vertical component p wave to s wave energy esppz espsz we find that this criterion only yields marginal separation of the source populations but becomes more effective at higher frequency bands f 4 0 hz or when looking at single station observations it does however help to quantify significant short period waveform differences between the three test subsites with pahute mesa shots generating relatively little s wave energy compared to those of yucca flat for which the s wave or lg is often the largest phase while rainier s shots are intermediate in character with distinct but less prominent s waves this s wave generation is thought to be caused by near source scattering to converted phases and appears to be highly dependent on the near source geology these two discriminants are useful in that they are simple and fast to calculate using regional stations for sources 200 to 1300 km away the magnitude threshold for the esppz e lp 3 discriminant is roughly ml 4 0 the limiting factor being the signal level of the airy phase while that for the esppz espsz discriminant is roughly ml 3 0 for the same distance ranges

the glycymeris query along the coast and shallow shelf of israel southeast mediterranean abstract high concentrations of empty valves of the genus glycymeris are found along the israeli coast both at the water line and in adjacent archeological sites in contrast with the abundance of the empty shells live specimens are rare this discrepancy raises the questions of when and where did glycymeris live on the israeli shelf and why and when did they disappear in this study concentrations of empty shells from contemporary depositional environments were sampled at 13 sites along the waterline and 91 sites on the israeli inner shelf between 3 and 30 m water depth in addition 12 coastal archeological sites were sampled so as to determine the distribution of bivalves in the last few thousands years and a random sample was checked for taphonomic characteristics six valves of glycymeris insubrica were radiocarbon dated glycymeris shells comprise 89 to 100 of the total dead mollusks shells found south of haifa with g insubrica comprising up to 100 of the entire glycymeris assemblage in archeological sites g insubrica is also abundant g insubrica an opportunist species appeared in large numbers 5000 5500 years ago and almost ceased to exist 1500 1000 years ago taphonomic studies based on the present day state of preservation of glycymeris support the observation that they ceased to exist sometime after 2000 years ago the sharp increase in their numbers is attributed to a combination of several factors the inner shelf became oligotrophic 5500 years ago the late holocene sea level rise slowed down considerably and nearly reached its maximum sandy sediments predominated and new habitats were open the near disappearance of g insubrica 1500 to 2000 years ago was probably due to the ongoing impoverishment of nutrient flux and reduction in marine productivity of the eastern mediterranean it may also have been part of the natural succession of populations that replace each other resulting in a distinct community change

facies analysis foraminiferal record and chronostratigraphy of holocene sequences from saltes island tinto odiel estuary sw spain the origin of high energy deposits abstract a multidisciplinary analysis of holocene sediments from la cascajera tinto odiel estuary sw spain has allowed to differentiate five sedimentary facies sandy tidal flat clayey tidal flat washover fan salt marsh edaphic horizon according to their granulometric characteristics internal structure mineralogical composition clay mineral assemblage and paleontological record these data coupled to 14c ams dating suggest an evolution from a sandy tidal plain to a chenier before 2100 cal yr bp this initial chenier was partially eroded later by regional storms between 2100 cal yr bp and 1900 cal yr bp leading to the deposition of two washover fans these facies have been eroded in the last centuries by the action of an ebb tide channel

spatial and temporal correlation between coda q and seismicity in china a map of coda q at 1 hz q was constructed for china by analyzing more than 1000 seismograms from 80 seismic stations distributed throughout china the resultant contour map of q shows a strong correlation with the epicenters of historic great earthquakes in china the high q regions are devoid of the epicenters and the low q regions are full of them a remarkably linear relation was found between the logarithm of coda q and the maximum earthquake within the area sampled by coda waves radius of about 150 km from each station when we consider earthquakes which occurred from 1700 to present roughly speaking if q is 1000 m max is about 4 and if q is 100 m max is about 8 this relation will be very useful for siting critical facilities such as nuclear power plants and waste disposal sites we also found evidence in support of the migration of low q region coincident with the well known migration of high seismicity region over the distance of several hundred kilometers during the period of several hundred years if the migration is due to a diffusion process the diffusion constant is of the order of 100 km2 yr which agrees very well with those associated with the aftershock migration fluid injection and vp vs anomaly comparison of coda q with q1 estimated from the intensity data shows that they agree very well for q1 150 supporting the validity of the s to s single backscattering model for coda waves for q1 150 however coda q becomes constant independent of q1 this behavior is qualitatively consistent with numerical experiments of frankel and clayton and suggests that coda q may be measuring the intrinsic q of about 150 for these regions where q1 150 this limiting coda q value may depend on regions because coda q lower than 100 has been observed in some active regions in this study and also coda q as low as 30 to 40 has been reported in california mexico and italy

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

empirical magnitude and spectral scaling relations for mid plate and plate margin earthquakes abstract published values of body wave magnitude m b surface wave magnitude m s and seismic moment m o for mid plate and plate margin earthquakes are analyzed to determine their inter relationship and to develop scaling laws for earthquake spectra all of the plate margin earthquakes used in the study occurred near the border of the pacific ocean the mid plate earthquakes occurred in both continental plate interiors and oceanic plate interiors for mid plate earthquakes the m b m s relation can be represented by two straight lines of slope one and two the intersection of the two lines corresponds to the body wave magnitude for which the corner period of the spectrum is at 1 sec the m b m s relation for plate margin earthquakes is more complicated because the derived spectra exhibit two corner periods a principal feature of the m b m o and m s m o relations is the fact that the large plate margin earthquakes have a higher m o value than the mid plate earthquakes for the same m b or m s because m b is a measure of the spectral amplitude for frequencies at which damaging ground motion occurs and m 0 is a measure of the spectrum at very long periods it follows that mb is a good estimator of strong ground motion whereas a moment derived magnitude is not the latter however is a good measure of fault rupture area the derived spectra of the mid plate earthquakes are flat at the long periods and have a slope of two at the short periods their seismic moment varies as the fourth power of the corner period implying that the stress drop increases as the moment increases for the large plate margin earthquakes the derived spectra are flat at the long periods have a slope of one at intermediate periods and a slope of two at short periods the stress drops are almost independent of moment for the larger plate margin earthquakes the moment magnitude relations for mid plate earthquakes indicate that an m s 8 7 event requires a fault rupture length of only 60 km for a fault width of 20 km a plate margin earthquake of m s 8 7 and fault width of 20 km would require a fault length of 6000 km obviously impossible assuming a fault width of 20 km an m s 8 2 earthquake has a rupture length of about 850 km which is as large as can be expected for strike slip faults such as the san andreas of california subduction zone earthquakes on the other hand if they have fault widths as great as 200 km can give rise to m s 8 7 earthquakes

phase and spectral ratio discrimination between nts earthquakes and explosions part i empirical observations seismic discrimination of small magnitude mb 0 5 hz regional measurements in this study we evaluate the most promising short period discriminants p wave to s wave phase amplitude ratios and low to high frequency spectral amplitude ratios for a data set from the nevada test site the data consist of 130 underground nuclear explosions one very large chemical explosion and 50 earthquakes ranging from magnitude 2 to 6 recorded at two broadband digital seismic stations operated by lawrence livermore national laboratory in contrast with much previous discrimination work in the western united states the common stations and paths for all the events in this study allow the discriminants to be evaluated without applying propagation corrections and differences between events can be ascribed to very near source effects the source effects found to have the most influence on the discriminants in this study are depth for the earthquakes and the source medium properties of gas porosity density and velocity for the explosions the phase amplitude ratio discriminants tested are pn lg and pg lg both show little dependence on magnitude and work better at higher frequencies and when averaged over the two stations at 6 to 8 hz pn lg discriminates all except the shallowest earthquakes while pg lg discriminates all but the high gas porosity explosions low to high frequency spectral amplitude ratio discriminants were tested in each of the phases pn pg lg and lg coda the explosions show significant dependence on source material properties such as gas porosity all the spectral ratios show dependence on magnitude and for 1 2 hz 6 8 hz none performs well below magnitude 3 5 of the spectral ratios lg coda performs the best at least in part because of its extremely small interstation variability discriminating all but the low gasporosity explosions the best discriminant performance is given by combining phase and spectral ratios a sum of the logarithmic values of pn lg pg lg and the lg coda discriminates all but two of the shallowest earthquakes the source medium dependence of the discriminants suggests that discrimination performance differences between the western united states and other regions of the world may be due more to source property differences than differences in the regional path simply put western united states discriminant studies differ from those in the rest of the world because of the lack of explosions in very high gas porosity low velocity materials outside of the nevada test site

yield estimates of nevada test site explosions obtained from seismic lg waves a methodology is presented for determining the yield of underground nuclear explosions from lg wave amplitudes the methodology is applied to nevada test site nts explosions for which the data from short period vertical component analog seismographs at three stations are used to develop calibration curves for unsaturated material and water saturated rock source conditions the latter curves are found to provide reasonably accurate estimates of the yields of explosions in other areas of the united states and in the french sahara suggesting that they may be applicable to all continental areas if so they also can provide an estimate of the bias of mb p magnitudes between different continental sites for example the lg data from nts explosions indicate a 0 31 0 02 magnitude unit bias between nts and eastern north america similar to the approximately 0 33 unit bias found between western and eastern north america previously by use of earthquake data

excitation and propagation of lg from earthquakes in central asia with implications for explosion earthquake discrimination broadband lg records from 52 shallow earthquakes that occurred near the balapan and lop nor nuclear test sites have been used to study spectral characteristics of the excitation and propagation of the lg phase in central asia using a source model that falls off as 2 at high frequencies and a nonlinear inversion method we simultaneously inverted for lg seismic moments m0 corner frequencies fc and path variable values of q0 and qlg at 1 hz and its power law frequency dependence the logarithms of m0 obtained using lg correlate linearly with logarithms of fc the slope being about 3 56 when all data are used and 4 04 when data were sufficient that full inversions could be performed these slopes differ only slightly from the slope of 3 83 obtained in our earlier studies using underground nuclear explosions the fc values in this study are systematically lower than those found for explosions at the same m0 level a comparison of corner frequencies and lg moment values for unknown events with the plots for known events of this study therefore provides means to discriminate between earthquakes and explosions the mb values are systematically lower for earthquakes of this study than for previously studied explosions at the same seismic moment moreover the logarithms of lg moments obtained in this study correlate linearly with a slope of 1 04 with mb values when all data are used and 1 21 when only well recorded events are used these slopes are close to the slope of 1 19 obtained for explosions the average qlg values along the paths used in this study agree well with those obtained using explosion data in central asia and with reported lg coda q values

a statistical model for ground motion produced by earthquakes at local and regional distances to adapt random process theory techniques for statistical estimation of peak ground motion to more realistic earth models we constrain the parameters of duration geometrical spreading and spectral shape by modeling the main ground motion as being the result of major contributions by the direct s wave and supercritically reflected s waves the results of our modeling are constrained to be consistent with values from full wave synthetics for the test models the combination of estimation theory and theoretical amplitude spectrum of the main ground motion within the ergodic window successfully predicts the mean peak vertical ground displacements velocities and accelerations of the 1982 miramichi earthquakes in new brunswick canada in addition upon considering the effects of source depth and crustal structure for the november 25 1988 saguenay earthquake m 5 8 in quebec canada the predicted mean peak horizontal ground accelerations match the observed data very well the effects of source depth and crustal structure on the peak ground motion are complicated for different source sizes and at different epicentral distance ranges

coastal shell middens in florida a view from the archaic period current models generally place the appearance of shell middens along florida s coasts after 5000 b p this paper argues that substantial shellfishing began at least two millennia earlier it reviews information on the earliest shell middens known in coastal florida and traces their evolution through the archaic period 10 000 3000 b p in three areas 1 the panhandle 2 the northeast and 3 southwestern florida in the panhandle estuarine exploitation was well established by 7200 b p the subsistence base included minor but consistent amounts of freshwater and terrestrial resources throughout the archaic on the northeast florida coast midden contents demonstrate that a range of terrestrial estuarine and littoral resources were being exploited by 6000 b p by 4500 b p however this diverse subsistence base was abandoned and a more targeted estuarine focus was adopted in southwest florida the earliest ca 7000 b p coastal populations gathered shellfish but the total subsistence regime is not clearly understood until 5000 4000 b p when intensive exploitation of marine shellfish and fish is recognized along the shore by 4500 b p in all three regions of florida estuarine subsistence bases supported population nucleation and the creation of monumental architecture by the end of the archaic period ca 3500 b p however the brief venture into large scale social works was abandoned in some but not all of florida as climate and or sea level regression brought significant environmental changes