test ban treaty verification with regional data a review this paper summarizes the use of regional 30 seismic data in a test ban context for detecting locating identifying and determining the yield of underground nuclear explosions in many areas of the world eastern north america africa eastern ussr lg is the largest amplitude wave recorded on standard seismograph systems and thus is the most appropriate phase for monitoring small magnitude events excellent location capability for near regional events has been demonstrated at the norwegian small aperture array noress using lg and p waves lg and other regional phases may contain information on source depth but such information has not been exploited to date fifteen classes of regional discriminants have been identified including 1 1 first motion 2 2 ms mb 3 3 p2 p1 ratio 4 4 excitation of short period sh waves 5 5 lg rg amplitude ratios 6 6 pn lg pg lg and pmax lg amplitude ratios 7 7 lg group velocity and energy ratios in lg 8 8 excitation of sn 9 9 third moment of frequency 10 10 generation of higher mode surface waves 11 11 peak amplitudes of love and rayleigh waves and long period surface wave energy density 12 12 prevailing period of long period love waves 13 13 spectral ratio long period s waves to rayleigh waves 14 14 spectral ratio long period love waves to rayleigh waves 15 15 frequency of the peak spectral amplitudes and spectral ratios in pn pg s and lg each of these proposed discriminants has with differing degrees of success separated some explosions from some earthquakes however most have been tested only on limited data usually from one geographic region and only one or two recording stations no systematic analyses have been done to determine the best individual discriminant or combination of them preliminary evaluation of the use of lg for yield determination suggests that regional waves hold promise in this application theoretical studies have contributed significantly to the understanding of propagation characteristics of regional waves but further studies are required emphasizing modeling for realistic anisotropic sources the major conclusion of this study is that a systematic and comparative evaluation of all the proposed regional discriminants is now required utilizing a common data base derived from all present day test sites this evaluation would suggest the optimal discrimination procedure using regional waves and would also define areas of needed research without such an integrated evaluation it is still possible to speculate using existing results on the most promising regional discriminants

single crystal 40ar 39ar dating of the olorgesailie formation southern kenya rift single crystal laser fusion sup 40 ar sup 39 ar analyses and several conventional bulk fusion sup 40 k sup 40 ar dates have been used to determine the age of volcaniclastic strata within the olorgesailie formation and of associated volcanic and sedimentary units of the southern kenya rift in the principal exposures along the southern edge of the legemunge plain the formation spans the interval from approximately 500 to 1 000 ka deposition continued to the east along the ol keju nyiro river where a tuff near the top of the formation has been dated at 215 ka in these exposures the formation is unconformably overlain by sediments dated at 49 ka a possible source for the olorgesailie tephra the ol doinyo nyokie volcanic complex contains as ash flow dated at approximately 1 ma extending the known age range of this complex to encompass that of virtually the entire olorgesailie formation in the legemunge plain these geologic examples illustrate the importance of the single crystal sup 40 ar sup 39 ar dating technique whereby contaminant altered or otherwise aberrant grains can be identified and eliminated from the determination of eruptive ages for reworked or altered pyroclastic deposits the authors have presented a computer modeling procedure based on an inverse isochron analysis thatmore promotes a more objective approach to trimming sup 40 ar sup 39 ar isotope data sets of this type less

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

spectral discrimination of nts explosions and earthquakes in the southwestern united states using high frequency regional data a high frequency seismic station has been operating since march 1987 near nelson nv records of earthquakes at regional distances from the station show substantially more energy at frequencies above 10 hz than records of nuclear tests of comparable magnitude on the nevada test site this contradicts the predictions made by investigators who have advocated high frequency monitoring for nuclear test detection and identification measuring the slopes of the pg velocity spectra between 4 and 30 hz successfully discriminates 11 nts explosions from 36 earthquakes recorded in the first seven months of operation the spectral differences may result from the respective source depths with the earthquakes occurring deeper and in faster material than the explosions

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

precambrian permafrost horizons as indicators of palaeoclimate abstract periglacial phenomena such as polygonal wedge structures and microrelief features commonly preserved in fossil permafrost horizons can provide valuable information on palaeoclimate including indications of mean annual air temperature seasonal temperature range relative precipitation and evidence for long term 104 years oscillations of climate such features are known from early and late proterozoic rocks and indicate mean annual air temperatures as low as 12 to 20 c or lower and strongly seasonal periglacial climates these palaeoclimatic data together with information on palaeolatitude and proximity to palaeo sea level may impose strong constraints on palaeoclimate models for proterozoic glaciation

discriminating quarry blasts from earthquakes using coda waves abstract a new quarry blast earthquake discrimination method is presented based on the analysis of seismic coda waves quarry blasts and local earthquakes in the area encompassing the south central mojave desert and eastern transverse ranges were used to test this method we found that the coda decay rate q c 1 is significantly higher for quarry blasts than earthquakes for lower frequencies 1 5 and 3 hz for lapse time up to about 30 sec this result is attributed to the greater contribution of surface waves to quarry blasts due to the shallowness of their source depth the difference in q c 1 however disappears for lapse time greater than 30 sec for the same frequency range as well as for higher frequencies 6 and 12 hz for lapse time greater than 20 sec this suggests that the coda waves at the lapse time greater than these critical values are dominated by the same type of body waves probably s waves for both quarry blasts and earthquakes the power spectrum p 0 obtained after the correction for attenuation was compared between earthquakes and quarry blasts at the same stations and a significant difference was found in the spectral shape between these two data sets the curves of power spectrum p 0 versus frequency for quarry blasts decrease more sharply than for earthquakes at high frequencies indicating a lack of energy in high frequencies for quarry blasts as compared to earthquakes the different frequency dependence of power spectrum p 0 between quarry blasts and earthquakes is attributed to their different source properties and can be used for seismic discrimination of quarry blasts from earthquakes

a comparison of regional phases from underground nuclear explosions at east kazakh and nevada test sites abstract analysis of regional data from east kazakh ussr and nevada test site nts underground nuclear explosions suggests possible mechanisms for the generation of both low and high frequency lg spectral characteristics of pn and lg phases from 25 soviet nuclear shots recorded at the chinese digital seismic network cdsn station wmq are analyzed for their dependence on parameters such as m b generally related to shot depth and spatial location shagan versus degelen test sites the observed results are compared with those from the nevada test site nts where the near source conditions are better known the average amplitude ratio pn lg is found to be stable with m b but to vary strongly with frequency for both shagan and yucca flat explosions of similar yield the reduction in amplitude over the frequency range of about 1 to 5 hz is considerably larger for lg than for pn the low frequency lg appears to be generated by the scattering of explosion generated rg into s especially for the shagan river explosions for which good agreement between observation and theory is observed this mechanism also provides a possible explanation for the stability of lg as an estimator of explosive yields because the scattering should be expected to occur over a large region of the shallow crust another important result supported by theory is that the higher frequency lg is strongly dependent on the source medium velocity at higher frequencies 3 to 7 hz the amplitude ratios pn lg for explosions from shagan degelen pahute mesa and yucca flat test sites show significant differences that appear related to differences in their source medium velocities the observed large differences in the relative spectral content of pn and lg from east kazakh and nts explosions are mainly due to the vast differences in the crustal structure of the two test sites

mineralogy of the tumanny au ag te hg epithermal veins western chukchi peninsula russia abstract the tumanny au ag te hg epithermal prospect chukchi peninsula russia is located in the near contact zone of the large vuknei pluton part of the early cretaceous egdykgych complex which is related to the peschanka porphyry copper deposit and the nakhodka porphyry epithermal ore district located 45 km north of tumanny mineralization at tumanny is characterized by an early carbonate base metal and a late gold silver sulfosalt mineral assemblage pyrite of the first assemblage is unzoned and as poor and tennantite tetrahedrite solid solutions ttrs are characterized by a weak oscillatory zoning caused by variable contents of sb and as low ag content and the widely variable sb sb as values pyrite of the second assemblage is zoned and as rich up to 5 2 wt and ttrs is weakly zoned and ag rich up to 10 35 apfu and has a comparatively narrow range of sb sb as value electrum au ag alloy kustelite au ag s phases hessite polybasite and imiterite recognized at the prospect belong to the second mineral assemblage the homogenization temperature of primary fluid inclusions in quartz ranges from 340 to 210 c and decreased during the mineralizing process fluid salinity varying from 0 8 to 5 2 wt nacl equiv is not evolved during the process cores of quartz crystals formed from a boiling fluid whereas crystal rims appear to have formed from a lower temperature non boiling liquid logfs2 decreased from 8 at the formation of carbonate base metal assemblage to 16 at the deposition of gold silver sulfosalt assemblage as temperature decreased from 340 to 200 c bulk icp oes analysis of mineralized samples indicated up to 38 ppm au 908 ppm ag 154 ppm mo 106 ppm te 53 ppm se 9246 ppm as 1284 ppm sb and 23 ppm bi cluster analysis of the data obtained identified three geochemical associations corresponding the carbonate base metal the gold silver sulfosalt and to the overlapped mineral assemblages the whole ore composition is controlled by mineralogy of these assemblages taking into account the geological setting mineralogy composition of minerals and fluid inclusion data the tumanny au ag te hg prospect is characterized as intermediate sulfidation epithermal style

automatic discrimination among landslide explosion quake and microtremor seismic signals at stromboli volcano using neural networks in this article we report on the implementation of an automatic system for discriminating landslide seismic signals on stromboli island southern italy this is a critical point for monitoring the evolution of this volcanic island where at the end of 2002 a violent tsunami occurred triggered by a big landslide we have devised a supervised neural system to discriminate among landslide explosion quake and volcanic microtremor signals we first preprocess the data to obtain a compact representation of the seismic records both spectral features and amplitude versus time information have been extracted from the data to characterize the different types of events as a second step we have set up a supervised classification system trained using a subset of data the training set and tested on another data set the test set not used during the training stage the automatic system that we have realized is able to correctly classify 99 of the events in the test set for both explosion quake landslide and explosion quake microtremor couples of classes 96 for landslide microtremor discrimination and 97 for three class discrimination landslides explosion quakes microtremor finally to determine the intrinsic structure of the data and to test the efficiency of our parametrization strategy we have analyzed the preprocessed data using an unsupervised neural method we apply this method to the entire dataset composed of landslide microtremor and explosion quake signals the unsupervised method is able to distinguish three clusters corresponding to the three classes of signals classified by the analysts demonstrating that the parametrization technique characterizes the different classes of data appropriately

late quaternary lake level changes of lake el gygytgyn ne siberia abstract lake el gygytgyn is situated in a 3 6 ma old impact crater in northeastern siberia presented here is a reconstruction of the quaternary lake level history as derived from sediment cores from the southern lake shelf there a cliff like bench 10 m below the modern water level has been investigated deep water sediments on the shelf indicate high lake levels during a warm mid pleistocene period one period with low lake level prior to marine oxygen isotope stage mis 3 has been identified followed by a period of high lake level 10 m above present in the course of mis 2 the lake level dropped to 10 m at the end of mis 2 the bench was formed and coarse beach sedimentation occurred subsequently the lake level rose rapidly to the holocene level changes in water level are likely linked to climate variability during relatively temperate periods the lake becomes free of ice in summer strong wave actions transport sediment parallel to the coast and towards the outlet where the material tends to accumulate resulting in lake level rise during cold periods the perennial lake ice cover hampers any wave activity and pebble transport keeping the outlet open and causing the lake level to drop

near source effects on regional seismograms an analysis of the nts explosions pera and queso a comparative analysis of two closely spaced nevada test site explosions pera and queso is made to study the effects of near source phenomena on regional wave excitation although the two explosions were of similar size burial depth and only separated by 4 km the 1 to 2 and 6 to 8 hz regional wave spectral ratio for queso is anomalously low a factor of 10 smaller than that of pera examination of the regional and close in spectra for each event shows a remarkable similarity and suggests that queso has less low frequency and more high frequency energy than pera these observations may be caused by a 564 m3 funnel shaped region filled with unconsolidated sand and a possible void directly above the queso detonation point close in observations suggest that this region may have partially decoupled the up going energy from queso resulting in a reduction of the low frequency energy the high frequency enhancement for queso may be due to the rapid loss of energy to nonlinear effects such as greater pore collapse and fracturing in the anomalous region this resulted in the radiation of more impulsive shorter duration waveforms producing a higher corner frequency and less rapid high frequency spectral decay for queso for pera the loss of energy to a two wave system occurred more slowly and over a larger volume resulting in a broader source pulse typical of explosions in porous materials comparison of shock radius versus time data suggests that the shock wave was strongly affected in the anomalous zone a few meters above the queso device one dimensional finite difference calculations with and without a partial decoupling region within 8 m of the device are consistent with the observations although spallation was reduced for queso simulations using a finite spall model indicate that the spall spectral peak should be centered at about 3 to 7 hz and probably did not significantly contribute to the reduced spectral ratio the remarkable similarity of the pera queso spectral ratios taken at distances of 90 m and 400 km suggests that the spectral characteristics of explosions are established in close proximity to the source although depth dependent effects of attenuation acting at small strains may enhance the differences in spectral ratios between nts explosions and western u s earthquakes these effects are probably secondary to the high pressure high strain rate dynamic material response to the radiated explosion shock wave these observations point out the importance of up going energy on the generation of regional phases from explosions because of reduced overburden pressures above the detonation point large nonlinear deformations predominate in this region and appear to affect all of the signals except perhaps the very initial part of the pn waveform

geochemical and sedimentological responses of arctic glacial lake ilirney chukotka far east russia to palaeoenvironmental change since 51 8 ka bp abstract palaeoenvironmental reconstructions with temporal coverages extending beyond marine isotope stage mis three are scarce within the data sparse region of chukotka far east russia the objective of this paper is to infer palaeoenvironmental variability from a 10 76 m long osl and 14c dated sediment core from lake ilirney chukotka 67 21 n 168 19 e we analysed high resolution sediment geochemistry xrf sedimentology tc tn toc grain size mineralogy xrd and preliminary micropalaeontological data diatoms and pollen from the core as well as acoustic sub bottom profiling data from the lake basin our results affirm the application of xrf based sediment geochemical proxies as effective tracers of palaeoenvironmental variability within arctic lake systems our study reveals that a lake formed during mis3 from 51 8 4 1 ka bp following extensive mis4 glaciation catchment palaeoenvironmental conditions during this time remained harsh associated with the continued presence of a catchment glacier until 36 2 2 6 ka bp partial amelioration reflected by increased diatom catchment vegetation and lake organic productivity and clastic sediment input from mixed sources from 36 2 2 6 ka bp resulted in a lake high stand 15 m above present and is interpreted as evidence of a more productive palaeoenvironment coincident with the mis3 interstadial optimum a transitional period of deteriorating palaeoenvironmental conditions occurred 30 27 9 ka bp and was superseded by periglacial glacial conditions from 27 9 0 8 ka bp during the last glacial maximum deglaciation as marked by sediment geochemical proxies commenced at 20 2 0 8 ka bp our findings are compared with lacustrine yedoma and river bluff records from across beringia and potentially yield limited support for a marked younger dryas cooling in the study area

new 40ar 39ar ages of cretaceous continental volcanics from central chukotka implications for initiation and duration of volcanism within the northern part of the okhotsk chukotka volcanic belt northeastern eurasia abstract we used the single crystal sanidine laser fusion 40ar 39ar method to date five samples of volcanic rocks from the northern chukotka part of the cretaceous okhotsk chukotka volcanic belt northeastern eurasia ages of four samples from lowermost stratigraphic units range from 87 94 to 87 08 ma and one sample from the top of the section shows the age of 87 55 ma new results combined with previously published 40ar 39ar data indicate that volcanism within the northern part of the belt started in coniacian time at ca 88 ma and was very short lived ca 1 6 m yr

site amplification of coda waves from local earthquakes in central california the goals of this study are two fold 1 to examine the site effect of coda waves believed to be the average site effect of shear waves in order to understand its spatial and frequency dependent behavior and 2 to learn what we can about the processes that generate the coda itself we use digital data from over 90 earthquakes each recorded by a subset of some 150 stations in the coast ranges of central california between san francisco and san luis obispo results from the band 1 5 to 24 hz indicate that site amplification depends strongly on surface geology and frequency at low frequencies 1 5 to 3 0 hz changes in amplification up to a factor of 20 are observed amplification generally varies inversely with deposit age at sediment sites and is lowest at granite and franciscan basement sites at high frequencies 6 to 24 hz the pattern changes many granite sites the majority in the gabilan range exhibit increasing amplification with frequency relative to the average station this behavior differs strikingly from that observed at sediment and franciscan sites which roll off at an intermediate rate and many sediment sites adjacent to the san andreas fault zone which decay away even more rapidly with frequency these results can be explained qualitatively by appealing to variable near site impedance and attenuation however complicating phenomena such as mode excitation in valley sediments must exist at low frequencies peaked behavior at a few hard rock sites at high frequency 12 hz currently lacks explanation at a few sediment sites the low frequency excitation is so strong that the coda envelopes begin to take on different shapes this contradicts the assumption based on previous observations that the coda shape is independent of source receiver location thus some site measurements may be artificially high the working model of coda waves as body wave energy backscattered from randomly distributed inhomogeneities must be modified to include the possibility of efficient near site resonance excited by incident direct and coda wave energy

the vendian succession of northeastern spitsbergen petrogenesis of a dolomite tillite association abstract the sedimentary record of late precambrian time is magnificently displayed in the highland snowfields of northeastern spitsbergen svalbard vendian strata are represented essentially by the polarisbreen group which consists mostly of dolostone and includes two dolomitic glacial units the oldest sediments in the polarisbreen group compose the elbobreen formation c 400 m which is divided into four laterally persistent members the lower carbonate member e1 125 m contains a distinctive basal dark grey limestone with microspar filled synaeresis cracks suggested to be of lagoonal origin and associated with minor dolostone shale and chert higher parts of the member are dominantly dolostone partly stromatolitic with some shale and sandstone shallow subtidal to intertidal deposition is indicated by the dominance of intraclastic lithologies and relics of anhydrite penecontemporaneous dolomite is partially overprinted by microsparry dolomite thought to be of groundwater origin the redefined petrovbreen member e2 consists of diamictite and other detrital dolostone pronounced thickness variations 2 40 m are thought to be original depositional features the member represents the deposits of a short glacial period in which the following depositional processes are inferred lodgement massive diamictite subaqueous meltout massive and bedded diamictite ice rafting lithologies bearing dropstones and possibly also diamictite redeposition by sediment gravity flows some diamictite and conglomerate rhythmite and shale current winnowing thin tabular conglomerate subaerial or subaqueous meltwater action channelled conglomerate and sandstone periglacial shrinkage diamictite wedge fillings the macdonaldryggen member e3 230 m is a monotonous succession of shaly dolostone of lagoonal origin it grades up into the slangen member e4 25 m which consists of subtidal to intertidal dolarenite with anhydrite relics succeeded by fenestral dolostone that was fractured and cemented by saline groundwaters in an emergent environment the wilsonbreen formation 160 m represents a return to glacial deposition but this time longer lasting and with substantial extra basinal material represented the gropbreen member w1 28 107 m and the ormen member w3 44 139 m consist dominantly of dolomitic diamictite with subordinate conglomerate and sandstone and are separated by a middle carbonate member w2 3 30 m which contains distinctive rhythmitic and stromatolitic limestone as well as sandstone the same depositional processes can be recognised as in the petrovbreen member but the wilsonbreen formation is overall of somewhat more continental aspect lower proportion of rhythmite and dropstone structures in addition there are basal breccia and crack fillings formed by frost shattering of the underlying cemented dolostone tabular sandstone thought to be formed by wave reworking of outwash a striated terrestrial cobble pavement supraglacially derived breccia horizons periglacial wedges filled by sand and the w2 assemblage of possible lacustrine origin the dracoisen formation 525 m represents an abrupt return to non glacial conditions an upward deepening wave dominated succession of pure dolostone d1 20 m and impure dolostone d2 105 m is succeeded by offshore black shale d3 150 m and then by a very shallow water succession of evaporite lacustrine aspect with a dolostone containing evaporite relics d5 10 m separating dolomitic sandstone and shale d4 80 m and d6 150 m the contact with the transgressive cambrian sandstones above is poorly exposed deposition of the succession dominantly under marine conditions is inferred but it is difficult to rule out a lacustrine environment at any particular horizon this dolomite tillite association can be explained by penecontemporaneous and minor secondary dolomite formation in marginal environments with warm climatic indicators at some levels being sharply interrupted because of rapid climatic changes by glacial sediments containing abundant detrital dolomite since the latter sediments make up only 17 of the 1080m thick succession glacial conditions only occupied a small proportion of vendian time

developing local to near regional explosion and earthquake discriminants abstract we develop local to near regional 0 200 km amplitude discriminants using earthquakes single fired explosions and delayed fired explosions we use the source phenomenology experiment spe broadband data collected across the colorado plateau during the summer of 2003 which recorded explosions in hard and soft rock mines we optimized a local surface wave magnitude scale derived from a stable regional surface wave magnitude russell 2006 for the sources however the magnitude of the source and the distance to the station limit the surface wave energy which can cause instability in the surface wave magnitudes magnitude scales for the local phases pg lg sg and rg were also tested and compared when an azimuthal station correction was applied to each magnitude scale there was an average reduction of standard deviation by 16 58 regional and teleseismic discrimination techniques were optimized for local distance and our results show that lithology of the source is a critical component in discriminating events at local distances we also found that magnitude and amplitude ratios are effectively used to discriminate between small earthquakes and explosions at local distances with each performing the best in the hard rock lithology furthermore the ratio techniques perform equally in both lithologies if multiple stations are used to establish the ratio values we find that an average of four or five stations will generally have a 90 or better correct identification for both types of ratios finally we find that the source lithology local site effects and large scale geologic features control most of the variability in the amplitude measurements

source parameters of the june 29 1992 little skull mountain earthquake from complete regional waveforms at a single station the june 29 1992 m sub b 5 5 little skull mountain earthquake occurred 20 km southeast of yucca mountain within the boundaries of the nevada test site this event was recorded at a very broadband station located about 310 km to the east at kanab utah both body and surface waves from this single station were used in a grid search technique for the best fitting double couple moment tensor the technique minimizes the misfit between reflectivity generated complete synthetic seismograms and the three component displacement data via a search over the strike dip and rake of the source in the passband of 50 15 s period the grid search results in a well defined nearly pure normal mechanism with a strike of 35 degrees a dip of 54 degrees a rake of minus 87 degrees and a seismic moment of 4 1 x 10 sup 17 n m applying the same technique to the large aftershock on july 5 1992 the authors obtain a somewhat less well defined minimum with a strike of 358 degrees a dip of 36 degrees a rake of minus 177 degrees and a moment of 4 3 x 10 sup 15 n m the minimum compression axes of these mechanisms are consistent with northwest southeast extension in the basin and range 14more refs 7 figs less

evidence for non self similarity and transitional increment of scaled energy in the 2005 west off fukuoka seismic sequence 1 we investigated seismic scaling relations of the 2005 west off fukuoka seismic sequence in japan using a coda based methodology two independent methods such as coda source spectrum method and coda spectral ratio method were applied to seismic waveform data recorded at four broadband seismic stations located around the epicenter of the mainshock the corner frequencies determined from both methods are consistent with each other and the scaling relations between the corner frequencies and the corresponding seismic moments are clearly non self similar in both cases moreover the scaled energy obtained from the coda source spectrum method shows that there is a transitional change in the scaled energy with seismic moment the scaled energy is larger for events with mw 5 0 than for events with mw 4 0 for events larger than mw 5 0 the scaled energy is almost constant and it means that they obey self similar scaling for events smaller than about mw 4 0 the scaled energy is more or less constant but it is difficult to decide whether it follows self similar or non self similar scaling because of scatter and the limitation of the minimum moment magnitude mw 3 4 the most important observation is a linear increment of the scaled energy between about mw 4 0 and 5 0 these observations imply that the rupture dynamics for larger and smaller earthquakes are different and that the change in dynamics may occur continuously between about mw 4 0 and 5 0 in this seismic sequence

lithostratigraphy of the impactite and bedrock section of icdp drill core d1c from the el gygytgyn impact crater russia in 2008 2009 the international continental scientific drilling program icdp obtained drill cores from the el gygytgyn impact structure located on the chukotka peninsula russia these cores provide the most complete geological section ever obtained from an impact structure in siliceous volcanic rock the lithostratigraphy comprises a thick sequence of lacustrine sediments overlying impact breccias and deformed target rock the interval from 316 m below lake floor blf to the end of the core at 517 m depth can be subdivided into four lithological sequences at 316 m depth the first mesoscopic clasts of shocked target rock occur in lacustrine sediments the growing abundance of target rock clasts with increasing depth and corresponding decrease of lacustrine sediment components indicate the extent of this transition zone to 328 m depth it constitutes a zone of mixed reworked impact breccia and lacustrine sediments volcanic clasts in this reworked suevite section show all stages of shock metamorphism up to melting the underlying unit 328 390 m depth represents a suevite package a polymict impact breccia with considerable evidence of shock deformation in a wide variety of volcanic clasts this includes fragments with quartz that exhibit planar fractures and planar deformation features pdf in addition at three depths several centimeter sized clasts with shatter cones were detected due to microanalytical identification of relatively rare microscopic impact melt particles in the matrix of this breccia this material can be confidently labeled a suevite also in this sequence three unshocked 1 m thick intersections of volcanic blocks occur at 333 83 351 52 and 383 00 m depths the upper bedrock unit begins at 390 74 m depth has a thickness of 30 15 m and represents a sequence of different volcanic rocks an upper part with basaltic composition from 390 74 to 391 79 m depth overlying a lower rhyodacitic part from 391 79 to 420 27 m depth this parautochthonous basement unit is only very weakly affected by the impact only one shocked quartz grain with two sets of pdf was recorded at 391 33 m depth the lower bedrock unit 420 89 517 09 m depth end of core is a brittly deformed rather homogeneous welded ignimbrite that in part can be considered a cataclasite the top three meters of this section are sheared which could represent pre impact tectonic deformation a 54 cm thick injection of polymict impact breccia occurs at 471 42 471 96 m depth

discrimination between natural earthquakes and explosions based on the azimuthal distribution of s p amplitude ratiosdiscrimination between natural earthquakes and explosions based on the azimuthal distribution

single station spectral discrimination using coda waves spectral discrimination methods applied at regional distances are based on the observation that there is a difference in the frequency content of the seismic waves radiated from the source region of earthquakes and explosions we have investigated a spectral discrimination method that exploits the scattered energy contained in the event codas of seismograms to measure the relative source excitation of earthquakes and explosions as a function of frequency key strengths of the coda method include the following 1 it is not affected by source radiation pattern because the scattering process averages the radiation over the focal sphere 2 path corrections are not required with the coda method because coda waves are scattered throughout a common crustal volume 3 it can be successfully applied using data from only a single station and 4 it can be successfully applied using data with clipped direct arrivals to implement the coda method we first estimate a type curve which represents the average shape of all the individual coda decay curves for a particular frequency band the shape of the type curve as well as the shape of all individual coda decay curves is controlled by the scattering and attenuation properties of the crustal volume sampled by the coda waves a common path effect the amplitude of the type curve is not defined and we arbitrarily adjust it to have a zero mean the amplitude difference between an individual event coda decay curve and the type curve provides a relative measure of the event s source size within the particular frequency band we define this amplitude difference as the relative source factor our approach exploits all of an event s usable coda for each spectral measurement thus providing a more stable measure of relative source size than could be obtained from using a predefined fixed length time window analysis of 27 nevada test site explosions and 15 southern great basin earthquakes 3 1 m 4 7 shows that the source factor difference between the 0 5 to 1 and 2 to 4 hz bands plotted against the 1 to 2 hz source factor is a stable event discriminant the method reliably distinguishes small explosions from small earthquakes 3 0 m 3 5 even if the explosions are overburied because the coda method requires only one seismic station we believe that it would be especially useful in identifying small clandestine underground nuclear tests that occur far from established networks

the effects of spall on regional seismograms the effects of spall on regional signals are investigated using synthetic seismograms to frequencies of 20 hz depending on the scaling relationships used it is found that spall may have an important effect on regional body waves and especially surface waves the frequency range in which the spall effect dominates is dependent upon the characteristic times of the spallation process but generally occurs in the frequency range of about 0 2 to 2 hz because of the peaked nature of the radiated spall spectra effects at frequencies outside the 0 2 to 2 hz frequency range will be dominated by the explosion source the frequency range and strength of the spall effect depend in a complicated manner upon the yield depth of burial near source structure and material strength uncertainties in the spall scaling relationships need to be better understood before the effects of spall on regional discrimination and yield estimation can be properly quantified copyright american geophysical union 1989

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

the 1992 landers earthquake sequence seismological observations the m w 6 1 7 3 6 2 1992 landers earthquakes began on april 23 with the m w6 1 1992 joshua tree preshock and form the most substantial earthquake sequence to occur in california in the last 40 years this sequence ruptured almost 100 km of both surficial and concealed faults and caused aftershocks over an area 100 km wide by 180 km long the faulting was predominantly strike slip and three main events in the sequence had unilateral rupture to the north away from the san andreas fault the m w6 1 joshua tree preshock at 33 n58 and 116 w19 on 0451 ut april 23 was preceded by a tightly clustered foreshock sequence m 4 6 beginning 2 hours before the mainshock and followed by a large aftershock sequence with more than 6000 aftershocks the aftershocks extended along a northerly trend from about 10 km north of the san andreas fault northwest of indio to the east striking pinto mountain fault the m w7 3 landers mainshock occurred at 34 n13 and 116 w26 at 1158 ut june 28 1992 and was preceded for 12 hours by 25 small m 3 earthquakes at the mainshock epicenter the distribution of more than 20 000 aftershocks analyzed in this study and short period focal mechanisms illuminate a complex sequence of faulting the aftershocks extend 60 km to the north of the mainshock epicenter along a system of at least five different surficial faults and 40 km to the south crossing the pinto mountain fault through the joshua tree aftershock zone towards the san andreas fault near indio the rupture initiated in the depth range of 3 6 km similar to previous m 5 earthquakes in the region although the maximum depth of aftershocks is about 15 km the mainshock focal mechanism showed right lateral strike slip faulting with a strike of n10 w on an almost vertical fault the rupture formed an arclike zone well defined by both surficial faulting and aftershocks with more westerly faulting to the north this change in strike is accomplished by jumping across dilational jogs connecting surficial faults with strikes rotated progressively to the west a 20 km long linear cluster of aftershocks occurred 10 20 km north of barstow or 30 40 km north of the end of the mainshock rupture the most prominent off fault aftershock cluster occurred 30 km to the west of the landers mainshock the largest aftershock was within this cluster the m w6 2 big bear aftershock occurring at 34 n10 and 116 w49 at 1505 ut june 28 it exhibited left lateral strike slip faulting on a northeast striking and steeply dipping plane the big bear aftershocks form a linear trend extending 20 km to the northeast with a scattered distribution to the north the landers mainshock occurred near the southernmost extent of the eastern california shear zone an 80 km wide more than 400 km long zone of deformation this zone extends into the death valley region and accommodates about 10 to 20 of the plate motion between the pacific and north american plates the joshua tree preshock its aftershocks and landers aftershocks form a previously missing link that connects the eastern california shear zone to the southern san andreas fault

regional source discrimination of small events based on the use of lg wavetrain nuclear monitoring requires identification of small events observed at regional distances for which lg is generally the largest seismic phase recent research including ours has provided significantly better understanding of the generation of lg from explosions but the new concepts have not yet been fully exploited for improving discrimination between low magnitude explosions and earthquakes in different regions of the world our analysis of spectrograms which display spectral energy versus time shows that lg from explosions alone is generally followed by several distinct arrivals with progressively lower frequency contents probably due to the scattering of explosion generated rg into s at several discrete near source locations this promising new discriminant may offer a distinct advantage over other seismic methods of discrimination since it may not require the region of interest to be calibrated with the help of earlier known type seismic events moreover regional discrimination based on the lg wavetrain can be especially useful when signal to noise considerations for a small event preclude the use of other seismic phases

the 2011 expedition to the el gygytgyn impact structure northeast russia toward a new geological map for the crater area el gygytgyn is a 3 6 ma 18 km diameter impact crater formed in an approximately 88 ma old volcanic target in northeast siberia the structure has been the subject of a recent icdp drilling project in parallel to those efforts a russian german expedition was undertaken in summer 2011 to investigate the permafrost soil lake terraces and the volcanic rocks of the southern and eastern crater rim this provided the unique opportunity for mapping and sampling of the volcanic target rocks around a large part of this complex impact structure samples from 43 outcrops were collected and analyzed petrographically and geochemically the results were combined with earlier mapping outcomes to create a new geological map of this impact structure and its immediate environs at the scale of 1 50 000 compositions of our rock suites are compared with the lithologies of the 2009 icdp drill core the ignimbrite described as lower bedrock in the icdp drill core shows petrographically and chemically strong similarities to the rhyolitic and rhyodacitic ignimbrites observed on surface the suevite sequence exposed in the icdp drill core is a mixture of all observed target rocks at their respective proportions in the area in contrast to previous studies the calculated average target composition of el gygytgyn takes the contribution of the basic target rocks into consideration mafic and intermediate rocks approximately 7 5 and felsic rocks approximately 92 5

a discrimination analysis of short period regional seismic data recorded at tonto forest observatory abstract a new seismic discriminant based on spectral differences of regional phases from earthquakes and explosions recorded at a single station has been tested and found to work remarkably well the test data consisted of a well constrained set of 30 nevada test site nts explosions and 21 earthquakes located within about 100 km of nts which were recorded on short period seismographs at the tonto forest observatory in central arizona at an epicentral distance averaging 530 km the events in the data set cover a magnitude range from 3 3 to 4 8 m b for which p n p g and l g phases have been analyzed we found that although l g phases from earthquakes are typically more prominent than for explosions with comparable p wave amplitude levels simple time domain l g p amplitude ratios do not result in a separation of the earthquake and explosion samples consistent enough to provide reliable discrimination however spectral analyses of the data over the frequency band from 0 5 to 5 0 hz revealed significant differences in the spectra of certain regional phases which proved to be a quite reliable discriminant in particular both the p g and l g spectra from earthquakes have been found to be richer in high frequency content than corresponding explosion spectra a discriminant measure defined as the ratio of average l g spectral amplitude level in the 0 5 to 1 0 hz passband to that in the 2 0 to 4 0 hz passband provides good separation of earthquake and explosion populations

source scaling of contained chemical explosions as constrained by regional seismograms quantification of source coupling and characterization parameters for contained single fired chemical explosions observed at a regional seismic array are quantified the explosions were conducted in a mine in northeast wyoming where delay fired explosions occur regularly the primary observational data sets consist of close in measurements in the mine and regional observations at the international monitoring system primary array at pinedale wyoming pdar the single fired explosions ranged in size from 5500 to 50 000 lb and were separated from one another from 30 m to over 4 km peak amplitude measures at a single element of the regional array are well matched with a power law dependence on explosive weight similar scaling constants were determined for each of the dominant regional phases p n 0 84 0 14 p g 0 84 0 09 and l g 0 91 0 08 peak amplitudes across pdar show a factor of 3 variation for an individual explosion across all array elements this amplitude variation is accompanied by a decrease in spatial correlation with increasing station separation indicating the importance of near receiver structure the regional signals were further characterized by computing frequency dependent envelope functions at each array element consistent source scaling factors at a single array element were obtained from the envelope functions a high degree of spatial variability as a function of frequency was documented for the envelope functions spectral ratios are used to investigate source scaling relations for the different explosions four similarly prepared shots with total explosive weights between 5500 and 6000 lb were detonated to investigate source repeatability spectral ratio analysis identified two of the four shots as only partially detonating resulting in a reduction of long period spectral level by factors of 10 and 50 these long period reductions were accompanied by increases in source corner frequency consistent with a smaller source size spectral ratios of waveforms from the larger explosions that fully detonated illustrate that p g and l g source functions are similar the empirical source ratio is well modeled with a mueller murphy source model these experiments and the resulting data analysis suggest that simple single fired explosions of modest explosive weight can be used to calibrate regional seismic arrays networks and individual stations

moment energy stress drop and source spectra of western united states earthquakes from regional coda envelopes we present a new method to estimate stable seismic source parameters such as energy moment and orowan stress drop using regional coda envelopes from as few as one broadband station we use the method to compute path and site corrected seismic moment rate spectra for 117 recent western united states earthquakes empirical green s function corrections were applied to our surface and body wave coda envelope measurements to generate s wave source spectra these source spectra provide stable single station estimates of radiated seismic energy es and seismic moment mo that for common events are in excellent agreement with network averaged estimates obtained using local and regional data teleseismic moment estimates are compatible with our regional results but teleseismic energy estimates appear to be nearly an order of magnitude low we estimated the seismic moment of events ranging between mw 2 2 and 7 3 and energy estimates for which we had measured at least 70 of the total energy generally events above mw 3 3 we use these estimates to examine the behavior of derived parameters such as the orowan stress drop 2 es mo while the earthquakes we studied have a small range in orowan stress drop generally between 0 1 and 20 mpa they show a strong tendency for orowan stress drop to increase with moment approximately as mo0 25 we believe this is a source effect and is not due to inadequate bandwidth or attenuation correction and note that this trend appears to continue for microearthquakes as described in a recent deep borehole study in southern california many of the large high stress drop earthquakes show complexity in their moment rate spectra near the corner frequency and cannot be fit by a simple square model instead above the first corner frequency the spectral decay ranges between f 1 0 and f 1 5 this leads to larger estimates of radiated energy than predicted with a simple square model and has implications for seismic hazard estimation coda envelopes have three main advantages over direct arrivals for estimating seismic moment and energy 1 coda amplitudes vary little with geology and source radiation anisotropy and allow accurate single station applications 2 path corrected coda amplitude measurements can be applied to very large regions allowing a comparison of source parameters throughout the western united states using a common methodology and stations 3 because long period coda can last for hours for large local and regional events it allows the analysis of seismograms with clipped early arrivals

yield estimation using regional mb pn seismic yield estimation at regional distances will become increasingly important in monitoring a low yield threshold test ban lyttb in order to investigate seismic yield estimation using regional data we have examined regional mb pn values for a large population of nevada test site nts underground nuclear explosions that occurred in widely varying geologic media with a range of yields from less than 1 kt to 300 kt magnitude yield relationships were developed using data from a set of pre 1985 events calibration set to obtain an independent estimate of the uncertainty in estimating yields of events at nts using mb pn alone the calibrated relationships were applied to a set of post 1984 events prediction set we found that the average uncertainty in the yield estimate based on a weighted combination of the yield estimates from the four livermore nts network lnn seismic stations is about 1 8 at the 2 level if data are available from all four lnn stations the uncertainty is about 1 7 at the 2 level by including a term for the gas filled porosity of the rock near the working point in the magnitude yield relationship we were able to develop a single relationship valid for events both above and below the water table as well as those in alluvium and tuff we have found however systematic differences in the relationships for events in yucca flat pahute mesa and rainier mesa

effects of glacial transport and neomorphism on precambrian dolomite crystal sizes late precambrian glacial rocks are notable for their association with dolostones1 and this has been regarded as a palaeoclimatological paradox2 5 however little detailed work has been carried out to determine the mode of origin of the dolomite in north east spitsbergen svalbard the vendian6 7 succession contains two glacial stratigraphical units8 9 which are dolomitic and are underlain and overlain by dolostones evidence from sedimentary structures and gross textures indicates that dolomite within the glacial units is detrital whereas at other levels it is a precipitate10 accordingly dolomite crystal sizes were analysed to determine whether evidence of glacial erosion and transport rock flour has been preserved allowing for the effects of later crystal enlargement aggrading neomorphism which vary within and between samples the results show a markedly higher proportion of very fine crystals in the inferred detrital dolostones compared with the precipitated dolostones the very fine crystals are interpreted as relics of rock flour the preservation of which demonstrates a novel means of testing the origin of dolostones associated with glacial sequences inorganic precipitation of dolomite during glaciation or secondary dolomitization of till are not required to explain the dolomite tillite association but pronounced climatic changes at the onset and close of glacial periods are indicated

automatic recognition of landslides based on neural network analysis of seismic signals an application to the monitoring of stromboli volcano southern italy in the last 9 years the amount and the quality of geophysical and volcanological observations of stromboli s activity have undergone a marked increase this new information highlighted that the landslides on the sciara del fuoco flank are tightly linked to the volcanic activity actually at the beginning of the december 28 2002 effusive eruption the seismic monitoring network was less dense than now and therefore it is not known if there was an increase in the landslide rate before the eruption despite this it is known that a big landslide occurred 2 days after the beginning of the eruption which caused a tsunami december 30 2002 more recently the effusive eruption in february 2007 was preceded by an increase in landslides on the sciara del fuoco flank which were recorded by the seismological monitoring system that had been improved after the 2002 2003 crisis these episodes led us to believe that monitoring the sciara del fuoco flank instability is an important topic and that landslides might be significant short term precursors of effusive eruptions at the stromboli volcano to automatically detect landslide signals we have developed a specialized neural algorithm this can distinguish between landslides and the other types of seismic signals usually recorded at the stromboli volcano i e explosion quakes and volcanic tremor the discrimination results show an average performance of 98 67 according to the experience of the crisis of 2007 to identify changes that can be considered as precursors of effusive eruptions we set up an automatic decision making method based on the neural network responses this method can operate on a continuous data stream it calculates a landslide percentage index lpi that depends on the number of records that are classified by the net as landslides over a given time interval we tested the method on february 27 2007 including the beginning of the effusive phase the index showed an increase as early as at 09 00 utc on that day and reached its maximum value 100 at 12 00 about 40 min before the onset of the eruption after the beginning of the effusive phase the index remains high due to the blocks that roll down along the slope from the front of the lava flow on the basis of these tests we propose a decision making method that is able to recognize a trend in the lpi similar to that of 2007 eruption allowing the identification of precursors of effusive phases at the stromboli volcano

spectral discrimination between quarry blasts and earthquakes in southern california we compare p wave spectra of quarry blasts and earthquakes recorded by the southern california seismic network scsn between 2000 and 2005 with the goal of developing methods to discriminate between these events we process the spectra using an iterative robust least squares method to isolate source receiver and propagation path contributions this corrects for first order attenuation structure as well as near receiver site effects and any errors in the instrument response functions using the earthquake spectra and a simple omega 2 source model we compute an empirical green s function egf to remove the trade off between the source terms and other parameters in our model a constant stress drop model gives a good fit to the observed average earthquake spectra over a wide range of moment magnitude but provides a mediocre fit to the average quarry blast spectra which have a generally steeper fall off at high frequencies than omega 2 we also compare p and s wave amplitudes and find modestly smaller average s amplitudes for the explosions compared to the earthquakes for southern california the root mean square rms misfit of p wave spectra to an omega 2 source model is a more reliable explosion discriminant than the s to p amplitude ratio and works for about 90 of the events

a preliminary study of regional seismic discrimination in central asia with emphasis on western china abstract in support of a comprehensive test ban treaty we have started to evaluate regional seismic event discrimination capabilities for central asia emphasizing western china we have measured noise and signal levels of over 260 earthquakes and 26 underground nuclear explosions recorded at the broadband digital station wmq in western china and over 120 earthquakes and five nuclear explosions at station aak in kyrgyzstan the explosions are from the kazakh test site kts and lop nor china the earthquakes are mostly from northwest china event magnitudes measured as either m b or m l range between 2 5 and 6 5 and maximum event station distance is about 1700 km we formed phase spectral cross spectral short period long period and long period ratios to test many possible event discriminants all ratios were corrected for distance effects before forming ratio versus magnitude discrimination plots the most consistent discriminants for separating earthquakes from explosions are p s phase ratios for frequencies above 3 to 4 hz p wave f 1 hz to rayleigh wave 0 03 hz f p s ratios separation between earthquakes and explosions increases with frequency and for the p r ratios separation increases with increasing p frequency the p 3 to 6 hz s 0 75 to 1 5 hz cross spectral ratios also separate earthquakes and explosions these cross spectral ratios may prove quite useful because due to weak high frequency l g signals from explosions the high frequency p l g ratio sometimes cannot be evaluated but the p 3 to 6 hz l g 0 75 to 1 5 hz can be evaluated successfully p spectral ratios 3 to 6 hz 0 75 to 1 5 hz also separate earthquakes and explosions but not quite as consistently as the p s ratios however p spectral ratios may prove useful in cases where path effects block or highly attenuate s n and l g waves rendering the p s ratios unavailable in contrast to nevada test site nts events the l g 3 to 6 hz 0 75 to 1 5 hz spectral ratio does not separate earthquakes and nuclear explosions in central asia this observation may be a source effect as asian explosions are thought to be detonated in highly lithified rocks below the water table while most of the smaller m b for station aak the short period spectral and cross spectral ratios identify a few earthquakes not recorded at wmq from the north pamir region that plot with the lop nor explosions the waveforms from these earthquakes lack surface waves and a distinct l g phase these events which we interpret as having occurred in a subducted slab do separate from the explosions on high frequency f 4 hz p s discrimination plots for station wmq long period r l rayleigh wave love wave ratios separate kts explosions and asian earthquakes however r l ratios fail to identify the large lop nor explosions recorded at station aak because the love waves are as large as the rayleigh waves suggesting that strong tectonic release occurs with these explosions because we have examined only one path at a single station for these explosions source radiation pattern may be influencing this observation