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

comparison of different site response estimation techniques using aftershocks of the 1999 izmit earthquake on 17 august 1999 the m w 7 4 izmit earthquake occurred in northwestern turkey a temporary seismic network was installed to improve the geometry of a previously installed network in this study 262 aftershocks of the izmit earthquake with magnitude m l ranging between 0 4 and 4 5 were analyzed using digital recordings from 17 stations of these networks s wave and p wave spectral records corrected for path attenuation function were inverted by means of the generalized inversion technique git the git site responses were compared with those calculated by horizontal to vertical h v ratios applied to both earthquake data and to pre event noise in most cases the h v of the earthquake data provided site responses with shapes consistent with those obtained using git however the level of amplification was occasionally found to be different in general these discrepancies can be explained either by the amplification affecting the vertical component of the ground motion that we detected by git or by the waves having a propagation in almost the vertical direction using the h v ratio applied to noise for most cases we obtained not only the peaks for the fundamental resonance frequencies but site responses with shapes similar to those obtained by git the detected level of amplifications using the h v ratio showed a tendency not to exceed those calculated by the inversion finally amplifications up to a factor 5 are found for stations placed over complex topography for these sites amplifications are not always correctly identified by the h v technique using either earthquakes or noise

textural control on gold distribution in as free pyrite from the dongping huangtuliang and hougou gold deposits north china craton hebei province china article i nfo pyrite from the dongping huangtuliang and hougou gold deposits hebei province china was investigated using a combination of ore microscopy including back scattered imaging and in situ laser ablation inductively coupled plasma mass spectroscopy la icp ms a range of elements including au te ag pb bi cu co ni and as was analyzed with the aim to constrain the textural controls and influence of superimposed deformation on the distribution of invisible gold in as free pyrite thedatasetshowsexcellentcorrespondence betweenmeasuredhighgoldvaluesandthreekeytexturalcriteria i areasofclusteredtellurideinclusions especiallyindongping ii microshearingandfracturing brecciation dongping and huangtuliang and iii pyrite recrystallization huangtuliang invisible gold is only at trace levels in the hougou and gold bearing telluride minerals are not observed this is considered to result from larger scale remobilization of gold during advanced brecciation and recrystallization of pyrite pyrite grains containing clustered inclusions have by far the highest gold concentrations up to 1 wt with consistent values of thousands of ppm au interpretation of textures and la icp ms data infers that in these areas the distribution of telluride inclusions extends pervasively from micron to nanoscale i e as fields of nanoparticles local employment of coupled dissolution reprecipitation reaction between pyrite and fluids driving the k metasomatic alteration dated at 150 ma is invoked to explain such patterns syn deformational grain scale mobilization of gold and other elements took place leading to a portion of the gold being recrystallized within fractures and microshears the deformational event leads to gold enrichment in the huangtuliang pyrite where brittle fracturing brecciation has been followed by a resorption and recrystallization in the latter case foam textured pyrites again without as can contain up to hundreds of ppm gold theinterpreted sequenceof pyritepost depositional eventsis inaccordancewith the protracted magmaticevolution of the area starting with variscan alkaline intrusions 390 ma and reactivated during the yanshanian orogeny 150 ma thestudyshows i thatas freepyritecanreadilycontainsignificantamountsofinvisiblegold bothasnanoparticles

calibration of mb pn mb lg scales and transportability of the m0 mb discriminant to new tectonic regions we have developed mo mb relationships for earthquakes and explosions in central asia using regional waveform data from the chinese broadband digital station wmq regional magnitude scales mb pn and mb lg were established by 1 determining the attenuation rates of pn and lg waves 2 calibrating the mb pn against the teleseismic rob and 3 applying nuttli s method to determine m b from the lg waves seismic moments for earthquakes and explosions were obtained by applying the bolt and herraiz 1983 method calibrated using cmt moments for earthquakes and regional moment estimates of the soviet joint verification experi ment jve explosion the results show that mo mb pn relationships for central asian earthquakes and explosions are in excellent agreement with the relationships for the western united states this demonstrates that the mo r discriminant is transportable to other regions and supports theoretical claims patton and walter 1993 that mo m b are directly comparable for explosions detonated in different emplacement media successful application depends upon correcting the mb pn for the magnitude bias known to exist between the shagan river test site and the nevada test site nts in general region specific mb bias must be accounted for whenever regional mag nitude scales are calibrated against teleseismic rob as pointed out by douglas and marshall 1996 transporting mo mb lg can be problematic because attenuation rates based on coda waves or lg waves from earthquakes may not necessarily apply to lg waves from explosions and vice versa this is demonstrated for the western united states where the coda q measured from explosion data is much lower than the coda q from earthquake data we show that mb lg for earthquakes located close to nts is greatly overestimated using the q values determined from the coda of nts explosions this is apparently not a problem for lg calibration in central asia perhaps because of differences in velocity and or q structures for the two regions other important considerations are the character of lg propagation on short paths 400 km for nts explosions versus long paths 1000 kin for east kazakh explosions and the properties of coda wave spreading as a function of distance and velocity structures for different tectonic regions

trace element systematics of pyrite from submarine hydrothermal vents abstract submarine hydrothermal sulfide ores occur at mid ocean ridges intra oceanic arcs and in back arc basins associated with host rocks of highly variable composition pyrite is the dominant sulfide mineral in most samples presented within this study and thus the trace element composition of pyrite may reflect the different metal sources and precipitation processes here we report on a systematic study of minor and trace element contents in pyrite from active and inactive submarine hydrothermal vent fields at different plate tectonic settings including the indian and mid atlantic ridges the tonga kermadec intra oceanic arc the lau back arc and the central okinawa trough our results show that the trace element contents of pyrite from different locations vary significantly but for most elements without any systematic correlation to the concentration in the magmatic host rocks only as appears to be depleted in pyrite from ultramafic hosted vent systems that are affected by serpentinization these as depleted pyrites preferentially host au 0 micro or nano particles bismuth is enriched in pyrite from hydrothermal systems that contain a sedimentary component and micro inclusions of sphalerite are either due to fluid sediment interaction or phase separated fluid venting pyrites from individual locations have highly variable concentrations of elements like au co cu se mo ag and sb that are most likely related to fluid evolution and changes in fluid composition sub seafloor hydrothermal fluid seawater mixing influences the distribution of au co cu se and mo in pyrite elements like au ag sb and pb often have a characteristic affinity to as while cd correlates closely with zn a magmatic volatile contribution to the hine hina hydrothermal system may result in the precipitation of cu enriched pyrite our results show that the concentrations of most trace metals in pyrite are a function of the physicochemical parameters of the fluid phase rather than a reflection of the magmatic host rock composition

seismic evidence for reverse activation of a paleo rifting system in the east sea sea of japan abstract the japanese islands were separated from the eurasian plate due to continental rifting during the oligocene to mid miocene which caused the opening of the east sea sea of japan such tectonic evolution in the east sea is important for understanding the evolution of back arc regions with active convergent margins to understand the evolution of the paleo rifted back arc region we investigate seismicity crustal seismic anisotropy focal mechanism solutions and ambient stress field around the korean peninsula the korean peninsula displays diffused seismicity with small and moderate earthquakes shallow earthquakes rarely occur in the central east sea the crustal fast shear wave polarization directions in the korean peninsula are observed to vary in azimuth between 40 and 90 the focal mechanism solutions are calculated by long period waveform inversions the ambient stress field is calculated from the focal mechanism solutions the compressional stress field in the korean peninsula is observed to be in ene wsw which is consistent with the fast shear wave polarization directions the compressional stress directions in the east sea progressively change from ene to se with increasing longitude the rapid change of compressional directions in the central east sea prohibits accumulation of stress causing rare shallow seismicity high seismicity of reverse faulting events is observed at the fringes of the east sea in particular around the east coast of the korean peninsula and the west coast of japanese islands which correspond to paleo rifted margins where compressional stresses are accumulated the compressional stress field and active thrustal events suggest reverse activation of paleo normal faults that were developed during the opening of the east sea

review of seismic source models for underground nuclear explosions abstract a number of seismic source models for underground nuclear explosions have been developed over the past 2 decades these models include the spherically symmetric compressional source model the wave conversion source model the tectonic strain release source model the spall slapdown source model and the near regional source model these model are reviewed in this study and are shown to be inconsistent with various geophysical data associated with underground nuclear explosions in particular the rayleigh and love wave signals generated by underground nuclear explosions have not been explained satisfactorily by any of these source models to explain the observed explosion data it may be necessary to model the explosion seismic source as a sequence of mechanisms producing seismic signals these mechanisms all act within the first few seconds following the explosion detonation one of the most important of these mechanisms is probably explosion induced thrust faulting

differences between site characteristics obtained from microtremors s waves p waves and codas we examine differences of empirical site characteristics among s waves p waves coda and microtremors using records at 20 sites in and around the sendai basin japan and interpret the differences theoretically at soft soil sites the horizontal to vertical spectral ratios hvrs for early p coda become different from hvrs for a p wave with increasing time and eventually converge on hvrs for microtremors the hvrs for an s coda become similar to hvrs for microtremors with increasing time in the frequency range lower than 3 hz at soft soil sites by contrast at a rock site and two hard soil sites hvrs for s coda agree well with hvrs for an s wave the soil to rock spectral ratios for horizontal hhrs and vertical vvrs components for early s coda are larger than those for an s wave at soft soil sites when we use the deep sedimentary structures above the bedrock before tertiary age theoretical hvr for the fundamental mode of rayleigh waves is consistent with observed hvr for microtremors and theoretical hvr for an obliquely incident sv wave is consistent with observed hvr for an s wave theoretical s wave site amplification factor explains well observed hhr for s wave but does not coincide with hvr for microtremors in general the frequencies of maximum peaks of hvrs for microtremors do not coincide with those of hvrs and hhrs for s wave however if we select hvrs with peak frequencies lower than 1 hz and peak amplitudes larger than three the peak frequencies of hvrs for microtremors roughly coincide with those of hvrs and hhrs for s wave even under these constraints their amplitudes do not coincide with each other concerning coda we conclude that the rayleigh wave contamination in coda is significant in the frequency range lower than 3 hz at soft soil sites

pyrite zoning as a record of mineralization in the ventersdorp contact reef witwatersrand basin south africa the archean metasedimentary succession of the witwatersrand basin south africa hosts the largest au deposit in the world gold mineralization is mostly concentrated in conglomerate horizons or reefs and is tightly associated with pyrite trace element zoning of pyrite from the ventersdorp contact reef studied by x ray elemental as ni co and pb maps electron microprobe analysis and laser ablation inductively coupled plasma mass spectrometry indicates successive stages of pyrite formation each characterized by different textures and trace element composition as 2 2 wt ni 1 37 wt co 1 98 wt four generations have been distinguished generation 1 is detrital and includes compact nonporous porous and laminated pyrite generations 2 to 4 are postsedimentary authigenic generation 4 pyrite formed at near peak metamorphic conditions t 270 350 c chlorite geothermometry porous and concentrically laminated pyrite grains generation 1 are particularly enriched in au average 6 4 ppm maximum 70 ppm in addition to sb tl pb mn mo cu and ag in comparison with compact pyrite types of all generations in these grains au occurring as invisible gold and other trace elements might be finely dispersed with the phyllosilicates filling the pyrite pores trace element composition of porous and concentrically laminated pyrite is reminiscent of pyrite known to form in suboxic to anoxic environments black shales the presence of au in detrital pyrite indicates an early introduction of au in the ventersdorp contact reef gold is also present as secondary inclusions of electrum associated with the last pyrite generation generation 4 together with sphalerite chalcopyrite galena and pyrrhotite

la icpms and epma studies of pyrite arsenopyrite and loellingite from the bhukia jagpura gold prospect southern rajasthan india implications for ore genesis and gold remobilization abstract the bhukia jagpura gold prospect is hosted by a paleoproterozoic metasedimentary rock sequence that constitutes the lowermost part of the aravalli supergroup lying in close proximity to the basement cover contact a combined ore petrographic la icpms and epma studies of iron sulfides and sulfarsenides from the prospect has revealed four varieties of pyrite and two varieties of arsenopyrite with different trace element compositions the data indicates a sedimentary diagenetic origin for the earliest pyrites py i and ii which are devoid of any gold in contrast to hydrothermal py iii and iv with a minor but significant content of invisible gold 0 3 1 6 ppm associated loellingite 35 51 ppm and arsenopyrite aspy i 0 28 10 ppm contain the maximum concentration of invisible gold while it is substantially lower in aspy ii 0 06 1 5 ppm the compositions of the gold bearing pyrites low ni co ratios arsenopyrites and loellingite rich in co and the presence of au bi te mineral phases within arsenopyrite support a magmatic hydrothermal model for the origin of gold sulfide mineralization which appears to have taken place during the peak of regional metamorphism or at an earlier stage the different stages of deformation and metamorphism released and remobilized gold in invisible and discrete forms from the sulfarsenides during prograde metamorphism of aspy i gold was partially incorporated and relatively enriched within the structure of loellingite later during retrograde metamorphism gold was exsolved as visible grains at the interface of loellingite and aspy ii and or within loellingite

decoupled geochemical behavior of as and cu in hydrothermal systems cu rich and as rich growth zones in pyrite provide new insights into the composition of late stage magmatic fluids and their host hydrothermal ore deposits the pyrite is from the pueblo viejo dominican republic and yanacocha peru high sulfidation gold silver deposits which are thought to form from hydrothermal systems that interacted with magmatic vapor plumes electron microprobe analysis secondary ion mass spectrometry and elemental maps show that pyrite the most common sulfide mineral in both deposits contains three different types of growth zones 1 as rich zones that are enriched in au ag sb te and pb 2 cu rich zones with significantly lower concentrations of these elements and 3 barren pyrite zones with no other elements these zones are interpreted to result from mixing between the pyrite forming fluid and vapors that invaded the main hydrothermal system episodically comparison to experimental studies of elemental partitioning and analyses of fumaroles and fluid inclusions from magmatic hydrothermal systems suggests that the as rich vapor formed at high and possibly magmatic temperatures whereas the cu rich vapor formed at lower temperatures possibly during migration of the original magmatic vapor the presence of finely spaced multiple growth zones in pyrite suggests that the composition of at least high sulfidation hydrothermal systems can be affected intermittently and repetitively by vapors probably from underlying magmas

pn travel time tomography of the paleo continental collision and rifting zone around korea and japan abstract a recent dense deployment of seismic stations in south korea and japan allows regional seismic imaging of the far east asian region that experienced continental collisions and riftings we perform seismic imaging based on a mantle lid p wave pn travel time tomography to exploit the tectonic imprints in the lithosphere the average pn velocity in the region is estimated to be 7 95 0 03 km sec the inverted pn velocities illuminate the tectonic structures high velocities of 8 15 km sec are observed in the precambrian massif regions while low velocities of 7 8 km sec are associated with the fold belt and sedimentary basin regions in the southern korean peninsula the pn velocity is estimated to be low in the backarc basins including the ulleung and the yamato basins while it is estimated to be higher on the continental fragments including the south korea plateau and the oki bank the high velocity structures along the japanese islands support the separation of the japanese province from the eurasia plate the high velocity anomaly along the east coast of the korean peninsula around the hupo bank suggests intrusion and solidification of high density material in the lower crust and mantle lid

vp vs ratios in the upper crust of the southern korean peninsula and their correlations with seismic and geophysical properties abstract the p and s velocity ratio v p v s is a seismic property that is convertible to poisson s ratio a widely analyzed physical property of elastic materials the lateral variation in the v p v s ratios of the upper crust of the southern korean peninsula is investigated based on the travel times of p and s waves of local events with epicentral distances of 50 km or less and focal depths of 25 km or less the dense seismic networks in the korean peninsula allow us to investigate the regional variation of v p v s ratios these v p v s ratios are estimated to be 1 60 1 91 with an average of 1 69 the v p v s ratios are as high as 1 73 1 91 in the gyeongsang basin jeju island and offshore region of the eastern okcheon belt but have relatively low values of 1 64 1 72 in precambrian massif regions the stability of the v p v s ratios is tested with randomly resampled travel time data the results of which suggest nearly constant v p v s ratios with increasing depth in the upper crust the influences of plausible errors on origin times and arrival times are quantified to verify the v p v s estimates the v p v s ratios are correlated with geological and tectonic structures comparisons with known seismic and geophysical properties suggest that structural features observed on the surface may extend at least to the mantle lid

tectonic and sedimentary evolution of the korean peninsula a review and new view abstract this review focuses on the tectonics and sedimentation of major sedimentary basins and orogenic belts late proterozoic neogene in the korean peninsula the korean peninsula is part of the amuria plate and represents an important link between continental blocks of north and south china and the island arcs of japan the basement rocks exposed in the kyonggi and yongnam massifs consist of 2 7 to 1 1 ga high grade gneiss and schist these massifs are separated by the okchon fold belt which comprises metasedimentary rocks and bimodal meta volcanic rocks the stratigraphy of the okchon group is unclear at present the okchon basin was probably initiated as an intraplate rift prior to the late proterozoic the hwanggangri formation clast bearing phyllite most likely represents deposition by subaqueous debris flows in slope environments of an enclosed basin the stratigraphic relationship between the okchon group and the choson supergroup cambro ordovician of the taebaeksan basin is poorly constrained the choson supergroup unconformably overlies the yongnam massif and consists mainly of carbonate sequence that formed mostly in shallow marine and tidal environments reflecting numerous sea level fluctuations the sequence is disconformably overlain by siliciclastic sequence of pyongan supergroup carboniferous triassic which formed most likely in shallow marine deltaic and fluvial environments the imjingang belt is an east trending fold and thrust zone and consists of metasedimentary rocks and volcaniclastics devonian carboniferous underlain unconformably by proterozoic basement rocks late proterozoic amphibolites of oceanic affinity were metamorphosed at about 8 13 kbar and 630 740 c during the late permian to the early triassic the south vergent contraction and top down to the north normal faulting are suggestive of a suture belt between the north china block sino korea craton and the south china block yangtze craton an extension of sulu belt across the yellow sea entire peninsula experienced strong deformation and metamorphism during the suturing event namely songrim orogeny during this orogenic event the kyonggi massif and the okchon basin accreted to the yongnam massif and taebaeksan basin along the south korean tectonic line running northeast southwest a series of northward trending thrust formed along the boundary zone to the east kaktong and kongsuwon thrusts and others piggyback basins locally developed along the thrust faults forming the taedong group the crustal deformation resumed in the early to late jurassic daebo event under contractional setting dextral ductile shearing associated with thrusting and folding continued in the mid southern part of the peninsula it was due to orthogonal northwestward subduction of the izanagi plate under the asian continent the yongnam massif experienced continuous dextral offset along the honam shear zone in the early cretaceous the izanagi plate began to subduct northward and caused formation of strike slip basins in retroarc setting i e kyongsang basin in the southeastern part and a number of small scale basins in the mid southwestern part of the peninsula small scale alluvial fans and fluvial channel networks formed in the basin margin and were transitional to ephemeral lacustrine systems under semiarid to arid conditions extensive intrusion of granitoids occurred from triassic to early tertiary with a gap between 160 and 100 ma representing continental magmatic arc in the tertiary the southeastern margin of the korean peninsula experienced back arc opening pull apart basins formed in the miocene bounded by the yangsan and hupo faults the yonil group sedimentary fill of the pohang basin comprises more than 1 km thick siliciclastic sequence which represents deposition in fan delta systems on the hanging wall of the yangsan fault thick more than 10 km thick sediments in the ulleung basin margin were deformed in the late miocene due to the northward movement of kyushu block quarternary volcanic events in cheju island represent intraplate hot spots

regional seismic observations of the 9 october 2006 underground nuclear explosion in north korea and the influence of crustal structure on regional phases 1 the crustally guided shear wave lg is typically the most prominent phase of a nuclear explosion at regional distance this lg phase is analyzed often to discriminate a nuclear explosion from a natural earthquake in addition the lg phase allows us to determine the size of the detonation a nuclear explosion test in north korea was conducted on 9 october 2006 the epicenter was located close to the eastern shore of the korean peninsula resulting in raypaths that vary significantly according to the azimuths in particular rays radiated in the southern direction experience lateral variation of crustal structures at the continental margin we examine the influence of raypaths on regional seismic phases by comparing the spectra and waveforms from different raypaths three natural earthquakes in north korea are also examined to determine the raypath effect we find that the lg from the nuclear explosion dissipated significantly as result of energy leakage into the mantle resulting from variations in crustal thickness along the portion of the raypath traversing the western tip of the sea of japan east sea some of the leaked energy develops into mantle lid waves sn causing a large energy increase to sn a similar feature is observed in the records of natural earthquakes this feature is confirmed by seismic waveform modeling the raypath effect also causes underestimation of magnitude the lg body wave magnitude mb lg is estimated to be 3 8 4 2 for records from pure continental paths and 2 6 3 4 for records from paths crossing continental margins this result illustrates the need to consider raypath effects for the correct estimation of magnitudes of regional events including a nuclear explosion

site amplification effects based on teleseismic wave analysis the case of the pellice valley piedmont italy the investigation of local amplification phenomena by seismic signal analysis is a fundamental step in carefully defining the seismic response of an area in this study we investigate the use of teleseismic recordings in assessing seismic wave amplification in the pellice valley northwestern alps italy assuming that teleseismic p waves are sensitive to the deep structure of a basin we deal with the computation of horizontal to vertical spectral ratios hvsrs and with the estimate of teleseismic p wave arrival time delays and p wave amplifications with respect to a reference site the reliability of the hvsr results obtained by considering teleseismic signals is confirmed by the agreement with the results coming from both the hvsr of noise and hvsr of s wave of local events methods strong correlation between the p wave arrival time delays and the relative p wave amplifications with respect to thickness of the low velocity layers and the geometry of the bedrock is found

geometrical spreading and q of pn waves an investigative study in eastern canada abstract station site effects uncertainties in seismic source spectrum and instrument response errors are among the well known frequency dependent contaminating factors that limit the reliability of short period q measurements of regional phases for the pn wave a regional phase of importance for both magnitude determination and nuclear test ban verification the problem is made worse by the added uncertainty of its geometric spreading function for realistic earth models the pn geometric spreading function is likely to depart drastically from that expected of canonical head waves the extent of this departure is sensitively dependent upon the regional crust mantle structure making geometric spreading assumption a conspicuous source of disagreement among the published pn attenuation q pn estimates we describe a technique referred to here as the extended reversed two station method rtsm for simultaneous determination of q pn and geometrical spreading function the formulation being designed to bring about direct cancellation of the contaminating source station and instrument effects is a reliable tool for mapping the pn propagation characteristics over continental paths long and short the extended rtsm has been tested using pn spectral amplitude data derived from seismic records of the eastern canada telemetered network ectn we find the spreading rate coefficient n in the power law representation of the geometric spreading d n d being epicentral distance to be frequency dependent increasing from 1 11 at 1 hz to 1 77 at 20 hz our q pn model in eastern canada takes the form of q pn 189 f 0 87 the results from eastern canada suggest that a there exists a significant positive velocity gradient in the uppermost mantle 0 0037 sec 1 b the regionally recorded pn waves are dominated by the superposition of a series of interfering diving waves bent by the velocity gradient and internally reflected at the underside of the moho discontinuity and c the very strong frequency dependence of q pn we found in this study region may not be unique among low attenuating shield and platform regions

m b pn scale for the korean peninsula and site dependent pn amplification the korean peninsula is located in the far eastern eurasian plate margin where crustal structures vary laterally causing significant raypath dependent modulations of crustal phases the discriminative variations of crustal phases hinder application of conventional local magnitude scales in the continental margin the mantle lid phase is less affected by the crustal structures than the crustal phases providing a better constraint to magnitude estimation a regional body wave magnitude scale based on the mantle lid p wave pn mb pn is developed for regional events around the korean peninsula the mb pn scale is determined to be mb pn 0 380 0 299 log a 2 012 0 122 log d where a is the peak to peak pn amplitude in m and d is the epicentral distance in km the mb pn estimates of regional events around the korean peninsula are determined the mb pn estimates are compared with other available magnitude estimates mb lg ml the influence of structures beneath stations on pn amplification is investigated from inter station magnitude residuals a characteristic spatial variation of inter station magnitude residuals with strengths mostly between 6 and 6 but with maximum strengths of 10 is observed the inter station magnitude residuals appears to be correlated well with geological and seismic structures in the crust

influence of continental margin on regional seismic wavefield abstract regional seismic analysis is an only way to investigate the source properties of small or moderate sized seismic events that occur in physically unaccessible regions such as oceanic regions and politically prohibited regions the ground motions by earthquakes need to be understood for better mitigation of seismic hazards particularly in continental margins that often incorporate high seismicity it has not been fully understood how seismic waves interact with complex crustal structures in continental margins responses of regional waves to complex crustal structures need to be quantified analysis of regional waveforms from controlled sources is desirable for investigation of influence of crustal structures the influence of continental margin around the korean peninsula is investigated in terms of spectral contents horizontal to vertical h v spectral ratios and quality factors using regional waveforms for the 2009 north korean underground nuclear explosion test that was well recorded by stations in the southern korean peninsula regional waveforms and spectral amplitudes vary significantly by path spectral contents of regional phases are different among stations in common great circle directions all regional phases modulate highly in continental margins path dependent seismic attenuation is strong in low frequencies 3 hz and weak in high frequencies 3 hz continental margins cause directional energy partition of regional waves depending on the path regional waves attenuate highly in passage across continental margin and then regrow on continental paths the growth rate is stronger than inherent attenuation rate causing seismic amplification the shapes of h v ratios are similar among various regional phases at common stations on the other hand the h v ratios for common phases vary by station in the same azimuths characteristic differences in h v ratios between two horizontal components suggest directional partition of seismic energy by crustal structures in the paths

frequency dependence of q in the mantle underlying the shield areas of eurasia part iii the q model summary a large set of teleseismic body wave data covering a broad range in frequency was analysed to determine the frequency arid depth dependence of q for p and s waves under the northern shield areas of eurasia based on numerous f estimates for p and s waves covering the seismic band between 0 02 and 8 hz a q model of the eurasian shield was constructed the data require a model in which q increases with frequency and which is characterized by q values in the upper mantle that are generally higher than those of global average models the model with the best fit includes a minimum in q between about 100 and 200 km depth and high q values on the order of thousands throughout most of the deeper mantle these results are generally consistent with proposed models of attenuation as a thermally activated process which is influenced by the temperature and pressure in the earth preliminary results suggest that t under tectonic regions is higher than t under shield regions for all frequencies over the 0 02 to 8 hz frequency range suggesting that q varies regionally as well as with frequency and depth

japan sea opening history and mechanism a synthesis the respective tectonic effects of back arc spreading and continental collision in asia are considered either as two independent processes or as closely interrelated extrusion tectonics assumes that the opening of the south china sea and the left lateral motion along the red river fault are geometrically linked in a pull apart manner this model is not accepted by several workers because the structural link between the two processes is not clearly demonstrated in the case of the japan sea we can show without ambiguity that back arc opening was controlled by large intracontinental strike slip faults which can be easily understood as effects of the india asia collision far from the indenter the japan sea opened in the early miocene in a broad pull apart zone between two major dextral strike slip shear zones the first one extends from north sakhalin to central japan along 2000 km it has accommodated about 400 km of finite displacement deformation along it varies from dextral transpression in the north to dextral transtension in the south the second is between korea and sw japan and has accommodated a smaller displacement of about 200 km the extensional domain in between lies in the back arc region of japan distributed stretching of the arc crust resulted in the formation of most of the japan sea while localized oceanic spreading at the southern termination of the eastern transpressional shear zone shaped the japan basin the first oceanic crust was formed in a small triangle based on the eastern shear zone and spreading propagated westward inside the pull apart region timing of oceanic crust formation of formation of the dextral shear zones and of block rotation in between as well as the internal structure of the basins and the geometry of deformation along the master shear zones are used to reconstruct the opening history this evolution is discussed by comparison to other manifestations of the arc and back arc activity such as the history of sedimentation and volcanism the paper then suggests that the collision of india can have tectonic consequences as far north as japan and sakhalin and describes the geometrical relation of back arc opening there and diffuse extrusion

oceanic crust in the japan basin of the japan sea by the 1990 japan ussr expedition in september of 1990 a seismic refraction and reflection survey was conducted in the japan basin in the northeastern part of the japan sea as a part of the japan ussr joint expedition twenty six ocean bottom seismometers obss were deployed on two 200 km long lines explosives and an airgun were fired as controlled seismic sources on the two mutually perpendicular lines airguns were also used as the source for the multi channel reflection profiles the crustal structure deduced is that of a typical oceanic basin the crustal thickness is about 8 5 km including 2 km of sediment we obtained a more detailed crustal structure than that obtained previously from the dense airgun shooting data the crustal structure is well resolved to show layer 1a layer 1b layer 2a 2b 2c layer 3 and the mantle the crust basically consists of laterally homogeneous layers but the moho deepens slightly westward

tomographic regionalization of crustal lg q in eastern eurasia 1 we measure q of crustal lg waves in eastern eurasia using the reliable two station methods more than 5 000 spectral ratios are collected over 594 interstation paths and are used to determine values of lg q0 and q at 1 hz and its frequency dependence over these paths these values are used to derive tomographic models of laterally varying q0 and with resolutions between 4 and 10 the q0 model contains values that vary between 100 and 900 q0 are the lowest in the tibetan plateau increase to moderate levels towards the east and north and reach maxima in the siberian and eastern europe cratons q0 values correlate well with regional tectonics most values are between 0 14 and 0 50 with a mean of 0 18 these values are lower than those obtained previously using either an lg coda q method or a method of simultaneous inversion of source spectra and q

trace element concentrations in porphyry copper deposits from metaliferi mountains romania a reconnaissance study there are fifteen miocene intrusions with porphyry copper mineralization in the metaliferi mountains romania most are associated with epithermal au ag te bi se ge vein systems the investigation of fifty samples from six deposits rosia poieni bucium tarni a colnic rovina valea morii and bolcana indicated bulk rock mean values of 0 16 0 88 ppm au 1000 ppm in bornite in the porphyry type mineralization galena forms microinclusions in pyrite chalcopyrite and bornite and contains up to 3750 ppm ag 17 380 ppm se 1570 ppm ge and 780 ppm te galena and pyrite from the epithermal mineralization in the m gura bolcana troi a system contain concentrations of ag and se ten times lower than in the same minerals from the porphyry copper mineralization the present data show that te is a significant trace element in the potassic zone of the investigated porphyry systems the data also shows that this does not correlate with the presence or absence of ophiolitic basement or with variation in the chemistry of the host intrusions tellurium enrichment in porphyry type deposits of the metaliferi mountains supports their genetic relationship with the spatially associated epithermal systems

global lateral variations of shear wave attenuation in the upper mantle we analyze several thousand high quality globally recorded ss s differential waveforms to constrain the lateral variation of shear wave attenuation q in the upper mantle we use a multitaper frequency domain technique to measure attenuation parameterized by a t operator and implement a robust estimation technique to compute t and its variance the differential waveform technique minimizes the effect of factors such as finite source duration and structural complexity near the source and receiver so the differential ss s waveforms are mainly sensitive to the shear attenuation in the upper mantle under the ss bounce point we use seismograms recorded at ranges of 45 to 100 and compute the ss s differential t from the broadening of the ss waveform relative to the hilbert transform of the s waveform a careful choice of fitting windows allows us to reduce the biasing effects of interfering phases which can affect t by up to 0 5 s the t residuals with respect to preliminary reference earth model prem vary by 1 5 s with an average of 0 24 s our study suggests an average q value of 112 most of the lateral variations of q are within 30 of this value in the top 400 km of the mantle slightly lower than the prem value of 128 there is a qualitative correlation of t residual with tectonic region with distinctly higher attenuation observed under young oceans compared to platforms and shields also the lateral variations of the residuals are similar in trend to those observed in studies of the attenuation of scs multiples at long wavelengths the qp map shows a modest correlation with shear wave attenuation maps computed from surface wave analyses and with the patterns of lateral variations of shear velocities at certain upper mantle depths predicted by the model s16b30 the correlation with the velocity model is highest at 300 500 km depth indicating that there may be a contribution to long wavelength attenuation from relatively deep regions formal inversion for an upper mantle q model shows that while lateral resolution is quite good depth resolution is poor as might be expected better depth resolution must await combined body wave and surface wave inversions

mineral chemistry and h o s pb isotopic compositions of skarn type copper deposits in the jiurui district of the middle lower yangtze river metallogenic belt eastern china abstract the skarn type copper deposits are widespread in the jiurui district in the middle lower yangtze river metallogenic belt this paper reports a detailed study on mineral chemistry and h o s and pb isotopic compositions on skarn silicate and sulfide minerals in the three major skarn dominant deposits wushan dongleiwan and dengjiashan the wushan skarn deposit is characterized with prograde garnet dominated and clinopyroxene limited skarns with average andradite content of 83 and hedenbergite content of 10 whereas the dongleiwan and dengjiashan deposits are featured with retrograde skarn alteration with abundant hydrous minerals such as epidote and chlorite the garnet and clinopyroxene compositions show 59 andradite and 15 hedenbergite for the dongleiwan skarns and 43 and 22 for the dengjiashan skarns respectively the pistacite components ps value defined as fe3 fe3 al and fe3 fe2 value of epidote are 0 12 and 1 63 for the wushan skarns 0 30 and 32 73 for the dongleiwan skarns and 0 17 and 42 85 for the dengjiashan skarns it is suggested that the prograde skarn mineralization in the three deposits was all formed in a relatively oxidizing environment with the wushan showing the highest oxidation potential and the dengjiashan having the least oxidation potential however in the retrograde skarns the dongleiwan and dengjiashan deposits show higher oxidation potential than that of wushan the three deposits show similar sulfur isotopic compositions of 2 9 to 1 4 and similar lead isotopic compositions with 206pb 204pb 207pb 204pb and 208pb 204pb ratios of 17 900 to 18 205 15 538 to 15 649 and 38 170 to 39 025 respectively all the three deposits should have similar magmatic origin for the ore forming materials based on their s and pb isotopes the oxygen isotopic compositions of the prograde and retrograde fluids in the three deposits show some differences with 18ofluid values of 8 13 and 7 81 for the wushan 6 47 and 2 33 for the dongleiwan and 8 27 and 4 43 for the dengjiashan but the hydrogen isotopic compositions are similar for the prograde 65 to 31 and retrograde 64 to 33 fluids therefore the fluid origins and evolution may be different in each deposit the hydrothermal fluids for the prograde skarns in all three deposits were likely derived from magmatic hydrothermal sources but the dongleiwan and dengjiashan show a higher proportion of meteoric water input in the retrograde stage considering the similar average prograde temperatures 574 to 560 c as calculated from coexisting garnet clinopyroxene pairs and similar retrograde temperatures 281 to 246 c as calculated from chlorite chemistry for the three deposits we suggest that the trigger for deposition of sulfide ores in the wushan garnet dominated skarn deposit was mainly caused by system cooling with temperature drop along with magmatic intrusion and crystallization process the dongleiwan and dengjiashan skarn deposits constitute a well developed retrograde skarn system with abundant epidote chlorite quartz and calcite which probably caused by fluid mixing of high temperature saline magmatic hydrothermal fluids with cooler oxidizing and dilute meteoric water

regional observations of the second north korean nuclear test on 2009 may 25 summary the suspicious seismic event that occurred in the northern korean peninsula on 2009 may 25 was declared to be the second underground nuclear test nk2nd by north korea we investigated the characteristics of nk2nd using seismic signals recorded at regional distance stations in south korea and china the pn lg ratios of nk2nd definitely discriminate this event from two nearby natural earthquakes at frequencies above 4 hz full moment tensor inversion of full waveform data shows that nk2nd had a very large isotropic component pure isotropic moment tensor inversion also resulted in good recovery of observed waveforms with clear indication that nk2nd was explosive in origin the moment magnitude mw from the full moment tensor inversion was estimated to be 4 5 and network averaged values of 4 6 and 3 6 were calculated for rms mb lg and ms vmax respectively although mb ms signature has been considered one of the most reliable discriminants for separating explosions and earthquakes this signature showed poor discrimination in the case of nk2nd the pn lg ratios and moment tensor inversion give more reliable evidence than does the mb ms for classifying the suspicious event in the northern korean peninsula as a possible explosion the characteristics of nk2nd are also quite similar to those of the first north korean nuclear test on 2006 october 9

characterization of eagle ford shale this paper presents the synthesized and characterized properties of eagle ford shale efs based on the collected data and laboratory testing results from the canceled superconducting super collider ssc site in texas usa index and mechanical properties of the clay shale were summarized and analyzed statistically correlations between index and mechanical properties were established the estimated shear strength of the intact shale was based on the results of drained triaxial compression and extension tests the results from uniaxial compression test on vertical and inclined cores and from the triaxial compression and extension tests show that the shale has strength anisotropy shear strength along the discontinuities was estimated based on the results from direct shear and triaxial tests on samples with preexisting joints constitutive models and bounds of drained shear strengths were evaluated and proposed for intact clay shale bedding planes and discontinuities the information on strength parameters and discontinuities can be used as the basis of future design and numerical studies

attenuation of broadband p and s waves in tonga observations of frequency dependent q teleseismic broadband recordings of intermediate and deep focus earthquakes are used to quantify both compression q and shear q wave attenuation within the lau backarc basin a spectral ratio method is employed to measure differential attenuation t between the depth phases ss pp and sp and the direct s and p phases over the frequency band 0 05 and 0 5 hz we use a stacking algorithm to combine the spectra of several phase pairs from a single event having similar azimuth and range to obtain more robust t measurements these estimates are then used to compute the average q above the focal depth q and q are measured directly from the ss s and pp p phase pairs respectively however the interpretation of t measured from sp p requires assumptions about the ratio q q we find an empirical ratio of q q 1 93 for this region and use it to compute q and q from the q sp observations

geochemistry of sulfide minerals from skarn cu au deposits in the fenghuangshan ore field tongling eastern china insights into ore forming process abstract in situ elemental compositions of sulfide minerals have been widely applied to trace ore forming processes of magmatic hydrothermal ore systems yet the application of elemental compositions of the sulfide minerals in skarn ore deposits is still restricted by the lack of understanding of their behaviors during the skarn formation processes in this study in situ la icp ms and epma elemental compositions of medium to coarse grained euhedral pyrite and xenomorphic granular chalcopyrite are investigated for the fenghuangshan and baoshantao skarn cu au deposits in the tongling region eastern china the results show that the studied pyrite samples have relatively consistent trace element composition characteristics while the chalcopyrite studied displays high zn ag and pb contents and relatively high bi content au ag cu pb bi sb and tl are mainly of lattice bound appearance in the pyrite structure the au ag sb pb and bi are mainly incorporated into the chalcopyrite structure as coupled substitutions low au mainly 1 and se tl mainly 10 ratios of the pyrite studied and high sn 10 ppm and low tl

focusing and defocusing of teleseismic p waves by known three dimensional structure beneath pahute mesa nevada test site the focusing and defocusing of teleseismic p waves predicted by a known three dimensional structure beneath the nevada test site is calculated by dynamic raytracing and superposition of gaussian beams the 20 to 100 km scale lengths of this model having velocity fluctuations of several per cent account for a factor of 3 fluctuation in the azimuthal pattern of p amplitudes since similar sized scale lengths and intensities of velocity fluctuation are commonly resolved in three dimensional inversions of mantle structure in other regions focusing and defocusing of teleseismic p waves is likely to be a ubiquitous feature of every test site hence network averages of mb that weight azimuthal windows in which p energy is either focused or defocused will tend to either over or underestimate the yields of underground tests the results obtained with a known nevada test site structure suggest that structural inversions having similar structural resolution may be capable of reducing 25 per cent of the variance in amplitudes due to the focusing and defocusing of upper mantle structure near the source assuming that scattering processes are concentrated in the crust and upper most mantle beneath the source and receiver the integrated energy in the p coda should be more stable than direct p because it tends to homogenize the effect of focusing defocusing structure near the source for scattering into direct p near the source for direct p scattering near the receiver however even the late coda is not capable of completely removing the effects of focusing defocusing near the source

surface wave tomography from ambient seismic noise of accelerograph networks in southern korea 1 an efficient and robust cross correlation technique for estimation of surface wave green s function between two locations is applied to a set of ambient noise data recorded by accelerograph networks in the southern korea we have estimated 1843 group velocities of rayleigh waves in the period band of 2 4 seconds from correlation pairs of 91 accelerograph stations relatively dense and uniform coverage of the pairs provides us with high resolution tomographic image of surface wave group velocities in the region the resulting group velocity distribution correlates well with the characteristic features of geological map of the region displaying low velocities for the sedimentary basins and regions of volcanic and metasedimentary rocks and high velocities for the regions where granitoid basement rocks outcrop the short period information from the accelerograph network can enhance resolution of the subsurface structures at depths within a few kilometers which may be predominantly responsible for simulation results of strong ground motions

fluid evolution in the formation of the fenghuangshan cu fe au deposit tongling anhui china the fenghuangshan cu fe au deposit is located in tongling anhui province in central east china within the middle lower yangtze river polymetallic belt the mineralization is related to late yanshanian magmatic intrusions emplaced in lower triassic limestones and is divided into two episodes the first and more important episode a is related to granodiorite granodiorite porphyry and characterized by massive disseminated veinlet and breccia style mineralization in skarn formed at the contact zone whereas the second episode b is related to a quartz monzodiorite porphyry stock which crosscuts the previous skarn and is characterized by disseminated and veinlet style mineralization within the porphyry based on mineral assemblages and their crosscutting relationships the hydrothermal evolution of episode a is further divided into five substages a1 a5 and that of episode b into four b1 b4 among which a4 a5 and b3 are the main copper mineralization stages this paper focuses on microthermometric studies of fluid inclusions in the various stages with an aim to characterize the thermal and compositional evolution of hydrothermal fluids and to discuss their implications for mineralization in terms of fluid sources and metal deposition mechanisms fluid inclusions were studied in garnet quartz and calcite from stages a1 a4 a5 b1 b2 b3 and b4 four types and 13 subtypes of fluid inclusions were distinguished based on fluid composition and phase assemblages type i fluid inclusions contain one or more salt daughter minerals halite and sylvite and homogenize into the liquid phase whereas type ii inclusions homogenize into the vapor phase both commonly containing an opaque daughter mineral type iii fluid inclusions are aqueous inclusions that do not contain daughter minerals and homogenize into the liquid phase and type iv inclusions are co2 bearing homogenize to the co2 or the aqueous phase and commonly contain an opaque daughter mineral primary fluid inclusions in stage a1 are of type i and ii interpreted to represent two immiscible phases resulting from boiling and those in stages a4 and a5 are of type iii stages b1 and b2 are characterized by type i primary inclusions and stages b3 and b4 by type iii type iv inclusions occur as secondary inclusions in b1 quartz and are interpreted to be related locally to b3 stage mineralization microthermometric data indicate a trend of decreasing temperatures and salinities from early to late stages for both mineralization episodes reflecting a change from a magmatic fluid dominated system to one invaded by fluids from the country rocks and meteoric water the fact that the main stages of mineralization a4 a5 b3 coincided with the development of fluid inclusions without daughter minerals of salt suggests that sulfide precipitation did not take place until the system was diluted by cooler fluids with lower salinities however the observation that the fluid inclusions hosted in minerals before sulfide mineralization i e stages a1 b1 and b2 commonly contain opaque daughter minerals inferred to be sulfides suggests that the ore forming components were likely derived from the higher temperature magmatic fluids and the fluids derived from the country rocks mainly contributed to the precipitation of sulfides through mixing and cooling

regional phase excitation and propagation in the lop nor region of central asia and implications for p lg discriminants ital pn and ital lg spectra for lop nor explosions and nearby earthquakes were analyzed for source and propagation effects using a modified inversion method of ital xie 1993 spectral analyses were performed on waveform data from incorporated research institution for seismology chinese digital seismic network kazakhstan and krgyzstan networks ital pn amplitude variations of a factor of 20 are observed across the small aperture lt 200 km kyrgyzstan network and are probably related to three dimensional moho structure close to the network comparisons of ital pn amplitudes and spectral ratios provide evidence for nonisotropic radiation pattern effects in the case of earthquakes and overshoot in explosion time histories complex source effects are born out in our inversion results 1 logarithm of seismic moment m sub 0 from ital pn and ital lg spectra scale linearly with body wave magnitude m sub b for explosions 5 0 le m sub b le 6 0 and for earthquakes 4 0 le m sub b le 5 5 2 pn m sub 0 estimates are similar to lg m sub 0 for earthquakes but are higher than lg m sub 0 for explosions 3 corner frequency f sub c scale as quarter root of m sub 0 for explosions and cube root for earthquakes 4 at the same m sub 0 level pn f sub c aremore 4 endash 5 times higher than lg f sub c for earthquakes and explosions and 5 ital pn source spectra are characterized by significant overshoot for explosions our results suggest that the cause of maximum separation between earthquake and explosion populations on plots of p lg spectral ratios which typically occurs for frequencies above explosion pn f sub c between 2 and 4 hz for explosions in this study may be related to overshoot in the reduced velocity potential copyright 1999 american geophysical union less

geochemical constraints on cu fe and fe skarn deposits in the edong district middle lower yangtze river metallogenic belt china abstract copper and iron skarn deposits are economically important types of skarn deposits throughout the world especially in china but the differences between cu and fe skarn deposits are poorly constrained the edong ore district in southeastern hubei province middle lower yangtze river metallogenic belt china contains numerous fe and cu fe skarn deposits in this contribution variations in skarn mineralogy mineralization related intrusions and sulfur isotope values between these cu fe and fe skarn deposits are discussed the garnets and pyroxenes of the cu fe and fe skarn deposits in the edong ore district share similar compositions i e dominantly andradite ad 29 100 gr 0 68 and diopside di 54 100 hd 0 38 respectively this feature indicates that the mineral compositions of skarn silicate mineral assemblages were not the critical controlling factors for variations between the cu fe and fe skarn deposits intrusions associated with skarn fe deposits in the edong ore district differ from those cu fe skarn deposits in petrology geochemistry and sr nd isotope intrusions associated with fe deposits have large variations in their la yb n ratios 3 84 24 6 and eu anomalies eu 0 32 1 65 and have relatively low sr y ratios 4 2 44 0 and high yb contents 1 20 11 8 ppm as well as radiogenic sr nd isotopes end t 12 5 to 9 2 and 87 sr 86 sr i 0 7067 to 0 7086 in contrast intrusions associated with cu fe deposits are characterized by relatively high sr y 35 0 81 3 and la yb n 15 0 31 6 ratios low yb contents 1 00 1 62 ppm without obvious eu anomalies eu 0 67 0 97 as well as 87 sr 86 sr i 0 7055 to 0 7068 and end t 7 9 to 3 4 geochemical evidence indicates a greater contribution from the crust in intrusions associated with fe skarn deposits than in intrusions associated with cu fe skarn deposits in the edong ore district the sulfides and sulfates in the cu fe skarn deposits have sulfur isotope signatures that differ from those of fe skarn deposits the cu fe skarn deposits have a narrow range of 34 s values from 6 2 to 8 7 in sulfides and 13 2 to 15 2 in anhydrite while the fe skarn deposits have a wide range of 34 s values from 10 3 to 20 0 in pyrite and 18 9 to 30 8 in anhydrite sulfur isotope data for anhydrite and sedimentary country rocks suggest that the formation of skarns in the edong district involved the interaction between magmatic fluids and variable amounts of evaporites in host rocks

source analysis of the memorial day explosion kimchaek north korea 1 a series of source inversions are performed for the 25 may 2009 memorial day north korean seismic event using intermediate period 10 50 s complete waveform modeling an earthquake source is inconsistent with the data and the best fit full seismic moment tensor is dominantly explosive 60 with a moment magnitude mw of 4 5 a pure explosion solution yields a scalar seismic moment of 1 8 1022 dyne cm mw4 1 and fits the data almost as well as the full solution the difference between the full and explosion solutions is the predicted fit to observed tangential displacement which requires some type of non isotropic non explosive radiation possible causes of the tangential displacement are additional tectonic sources tensile failure at depth and anisotropic wave propagation similar displacements may be hidden in the noise of the 2006 event future analyses of this type could be used to identify and characterize non earthquake events such as explosions and mine collapses

evidence for strong ground motion by waves refracted from the conrad discontinuity abstract the conrad discontinuity a boundary between the upper and the lower crusts has long been identified in many continental crusts the influence of the conrad discontinuity on seismic hazards however has been rarely known strong regional phases corresponding to the waves refracted from the conrad discontinuity are observed in the korean peninsula these phases show strong amplitudes of 2 4 times larger than those of the direct waves the observation is confirmed by numerical modeling of waveforms these observations not only support the existence of the conrad discontinuity in the korean peninsula but also suggest the potential of seismic hazards by the conrad phases such strong conrad refracted phases are typically recorded in the pn coda portion which may cause overestimation of pn body wave magnitudes for regional events

trace element characteristics of different pyrite types in mesoarchaean to palaeoproterozoic placer deposits a comparative in situ la icp ms trace element study on pyrite from three different variably auriferous archaean to palaeoproterozoic palaeoplacer deposits in the ouro fino syncline quadrilatero ferrifero brazil the elliot lake area north of lake huron se canada and several deposits within the witwatersrand basin south africa revealed systematic differences between morphologically different pyrite types and between the various palaeoplacer deposits especially the ni and au concentrations as well as co ni and mo ni ratios were found to be systematically different in detrital compact detrital porous and post sedimentary hydrothermal pyrite grains from different source areas high co ni ratios and low au concentrations are typical of post sedimentary pyrite which is hydrothermal in origin in contrast relatively low co ni ratios and high au contents characterise detrital porous banded and concentric pyrite grains au 1 ppm which are syn sedimentary in origin in the elliot lake area and the witwatersrand basin detrital compact rounded pyrite is characterised by high co ni ratios which is in agreement with derivation from a hydrothermal source low au concentrations in this pyrite type support the contention of the gold and the pyrite in these deposits coming from different source rocks in contrast derivation from an originally diagenetic pyrite is suggested for the detrital compact pyrite in the ouro fino syncline because of low to intermediate co ni ratios high au contents may indicate a genetic relationship between pyrite and gold there systematic differences exist between the three areas with respect to au ni co mo and cu distributions in detrital pyrite which reflects differences in the provenance a predominantly mafic ultramafic source is indicated for the ouro fino a felsic source for the elliot lake and a mixed felsic mafic provenance for the witwatersrand pyrite populations independently of pyrite type the higher au endowment of the studied witwatersrand and ouro fino conglomerates are also reflected by an overall higher au concentration in the respective pyrite grains compared to the relatively au poor samples from elliot lake in general a strong positive correlation between au and pb levels in the various pyrite grains is noted analogous to pb which is well known for not being easily accommodated in the pyrite crystal lattice but occurring as discrete pbs phases au is considered to be present mainly in the form of discrete au phases in minute pores and interstices of the pyrite grains rather than within the pyrite lattice

geological and geochemical constraints on the genesis of the xiangquan tl only deposit eastern china abstract the xiangquan tl deposit located in the northern part of the middle lower yangtze valley metallogenic belt eastern china is the only known tl only deposit it is hosted in micritic limestone marl and mudstone of the lower ordovician lunshan formation the orebodies are controlled by the xiao xiaolongwang dalongwang anticline and two reverse faults and are generally stratabound and lenticular tl is only ore metal contained in disseminated massive brecciated and banded ores the ore is composed of tl bearing pyrite and gangue minerals quartz fluorite barite and carbonate alteration minerals include fluorite barite fine grained quartz and carbonate tl occurs isomorphously replacing iron in the lattice of pyrite and less commonly as tiny independent tl bearing minerals which may be lafossaite tlass 2 or lorandite tlcl appearing as 0 1 1 m sized cubic crystals xiangquan is a submarine sedimentary deposit and demonstrates that tl as a normally dispersed element can form not only part of poly metallic deposits but also as independent tl deposits

site effect evaluation using spectral ratios with only one station the spectral ratio technique is a common useful way to estimate empirical transfer function to evaluate site effects in regions of moderate to high seismicity the purpose of this paper is to show that it is possible to estimate empirical transfer function using spectral ratios between horizontal and vertical components of motion without a reference station the technique originally proposed by nakamura to analyze rayleigh waves in the microtremor records is presented briefly and it is discussed why it may be applicable to study the intense s wave part in earthquake records results are presented for three different cities in mexico oaxaca oax acapulco gro and mexico city these cities are very different by their geological and tectonic contexts and also by the very different epicentral distances to the main seismogenic zones affecting each city each time we compare the results of nakamura s technique with standard spectral ratios in all three cases the results are very encouraging we conclude that if site effects are caused by simple geology a first estimate of dominant period and local amplification level can be obtained using records of only one station

regional and teleseismic analysis of underground nuclear explosion waveforms and constraints for shear wave excitation mechanisms 1 regional and teleseismic waveforms of underground nuclear explosions unes at the balapan and the nevada test sites are analyzed to understand the nature of shear waves excited from unes the phase composition of wavefields in the source and receiver regions is examined using a source array frequency wave number analysis and polarization analyses it is observed that regional mantle lid shear waves sn often develop strongly on the other hand observed teleseismic shear waves from unes are much weaker than those from earthquakes source array analyses of the shear waves from unes display coherent energy that is polarized in a certain azimuthal direction the observation of coherent shear energy in different unes suggests that the shear energy is excited in a consistent manner at every une we constrain the dominant shear wave excitation mechanism from the observed shear wave features the observations appear to be consistent with the tectonic release model with conical rock cracking

transition from rifted continental to oceanic crust at the southeastern korean margin in the east sea japan sea 1 the southeastern korean margin documents the processes of continental rifting and seafloor spreading that eventually led to the opening of the southern part of the east sea japan sea two dimensional crustal structure of the southeastern korean margin was computed from ocean bottom seismometer data by tomographic inversion and iterative forward modeling the crustal structure shows the emplacement of high velocity 7 km s lower crust under the continental shelf and slope area associated with a rapid transition from rifted continental to oceanic crust the high velocity lower crust is interpreted as magmatic underplating formed by voluminous igneous activity during rifting magnetic modeling confirms its primary correlation with a prominent magnetic anomaly along the edge of the korean peninsula we suggest that the rifting and subsequent seafloor spreading at the korean margin was significantly controlled by the supply of magma in a region of hotter than normal mantle temperature

site amplification in the san fernando valley california variability of site effect estimation using the s wave coda and h v methods during the months that followed the 17 january 1994 m 6 7 northridge california earthquake portable digital seismic stations were deployed in the san fernando basin to record aftershock data and estimate site amplification factors this study analyzes data recorded on 31 three component stations from 38 aftershocks ranging from m 3 0 to m 5 1 and depths from 0 2 to 19 km site responses from the 31 stations are estimated from coda waves s waves and ratios of horizontal to vertical h v recordings for the coda and the s waves site response is estimated using both direct spectral ratios and a generalized inversion scheme results from the inversions indicate that the effect of qs can be significant especially at high frequencies site amplifications estimated from the coda of the vertical and horizontal components can be significantly different from each other depending on the choice of the reference site the difference is reduced when an average of six rock sites is used as a reference site in addition when using this multi reference site the coda amplification from rock sites is usually within a factor of 2 of the amplification determined from the direct spectral ratios and the inversion of the s waves however for nonrock sites the coda amplification can be larger by a factor of 2 or more when compared with the amplification estimated from the direct spectral ratios and the inversion of the s waves the h v method for estimating site response is found to extract the same predominant peaks as the direct spectral ratio and the inversion methods the amplifications determined from the hiv method are however different from the amplifications determined from the other methods finally the stations were grouped into classes based on two different classifications general geology and a more detailed classification using a quaternary geology map for the los angeles and san fernando areas average site response estimates using the site characterization based on the detailed geology show better correlation between amplification and surface geology than the general geology classification

joint analysis of teleseismic receiver functions and surface wave dispersion using the genetic algorithm teleseismic p wave receiver function data and rayleigh wave phase velocity measurements are combined using the genetic algorithm a global optimi zation technique to model crustal structure in southern korea the two datasets complement each other because receiver functions are sensitive to shear wave ve locity contrasts in layered structures while surface wave dispersion is sensitive to averages of shear wave velocities the genetic algorithm is more useful than line arized inversion in regions where there is little a priori information about local velocity structure because it is not sensitive to the initial model the stability and variability of resulting crustal model parameters are quantified by using a monte carlo technique in specifying a suite of initial models depths to the moho discon tinuity in southern korea were estimated to be 29 30 km for stations near the western coast and 33 36 km for inland stations a well resolved crustal low velocity zone was inferred for some stations

regional phases in continental and oceanic environments summary the very different crustal thicknesses between continental and oceanic crust lead to the establishment of distinct styles of regional seismic wavefield observations and numerical simulations of events near subduction zones in japan allow a direct comparison of seismic wave propagation in oceanic and continental structures the thick zone of lower seismic velocities in the continental crust acts to trap s wave energy in particular and generates crustally guided phases such as pg lg in the oceanic environment there is no efficient s wave trapping and crustal energy progressively leaks into the mantle reverberations in the crust and the water above help to sustain the amplitude of the mantle arrivals pn sn to large distances

seismological constraints on the collision belt between the north and south china blocks in the yellow sea abstract the korean peninsula eastern china and the yellow sea comprise the eastern eurasian plate and are believed to share considerable tectonic evolution history the tectonic structures in the yellow sea are poorly understood raising difficulty in reconstruction of tectonic evolution history in the eastern eurasian plate the tectonic structures in the yellow sea are constrained by seismicity and fault plane solutions of earthquakes the fault plane solutions are determined by waveform inversions and seismic phase polarity analyses the ambient stress fields are deduced from the fault plane solutions the primary stress field around the yellow sea is composed of ene wsw directional compression and nnw sse directional tension normal faulting earthquakes with ene wsw directional strikes are observed in the central yellow sea between the shandong peninsula and the central korean peninsula the normal faulting region is interpreted to be a northern margin of collision belt between the north and south china blocks the normal faulting system suggests post collisional lithospheric delamination causing reverse activation of paleo thrustal faults that were developed by the collision between the north and south china blocks in the early jurassic period

source spectra and site response from s waves of intermediate depth vrancea romania earthquakes abstract seismograms from 55 intermediate depth vrancea earthquakes m 4 0 7 1 recorded at 43 stations of an accelerometric network in romania are used to derive source spectra and site amplification functions from s waves in the frequency range 0 5 20 hz with the generalized inversion technique git castro et al 1990 attenuation is taken into account using the nonparametric attenuation functions derived by oth et al 2008 from the same dataset and the attenuation corrected data are then split into source and site contributions the source spectra follow the 2 model brune 1970 1971 with high corner frequencies and a related brune stress drop of the order of 100 mpa the site amplification functions are separately determined for both horizontal and vertical components contrary to widespread expectation the vertical component shows significant amplification effects at high frequencies the h z ratios determined from the git results compare well with h v ratios computed directly from the s wave window of the accelerograms lermo and chavez garcia 1993 the basic assumption for the determination of site effects from h v ratios is that the vertical component is not or only little affected by site effects for vrancea earthquakes this assumption is incorrect consequently site effects should not be estimated from h v ratios the reason for this peculiar fact is the geometry of intermediate depth seismicity that leads to almost vertical ray paths beneath the stations

geodynamic settings and tectonic model of skarn gold deposits in china an overview seventy skarn type gold deposits including 1 super large 19 large and 24 medium sized are known from different geotectonic units of china they contain a total resource of approximately 1000 t of gold 625 t in south china and account for 20 of china s gold reserves these skarn deposits are sited in collisional orogenic belts fault controlled magmatic belts and reactivated cratonic margins all of the chinese skarn gold provinces were affected by phanerozoic collisional orogenesis the timing of the metallogenic events and the spatial temporal distribution of the chinese skarn gold deposits indicates that they were formed during ore forming processes linked to the transition from shortening to extension in the geodynamic evolution of a collision orogen and not to subduction systems as is commonly advocated for porphyry copper systems around the pacific rim

the coupled geochemistry of au and as in pyrite from hydrothermal ore deposits the ubiquity of au bearing arsenian pyrite in hydrothermal ore deposits suggests that the coupled geochemical behaviour of au and as in this sulfide occurs under a wide range of physico chemical conditions despite significant advances in the last 20years fundamental factors controlling au and as ratios in pyrite from ore deposits remain poorly known here we explore these constraints using new and previously published empa la icp ms sims and pixe analyses of as and au in pyrite from carlin type au epithermal au porphyry cu cu au and orogenic au deposits volcanogenic massive sulfide vhms witwatersrand au iron oxide copper gold iocg and coal deposits pyrite included in the data compilation formed under temperatures from 30 to 600 c and in a wide variety of geological environments the pyrite au as data form a wedge shaped zone in compositional space and the fact that most data points plot below the solid solubility limit defined by reich et al 2005 indicate that au1 is the dominant form of au in arsenian pyrite and that au bearing ore fluids that deposit this sulfide are mostly undersaturated with respect to native au the analytical data also show that the solid solubility limit of au in arsenian pyrite defined by an au as ratio of 0 02 is independent of the geochemical environment of pyrite formation and rather depends on the crystal chemical properties of pyrite and post depositional alteration compilation of au as concentrations and formation temperatures for pyrite indicates that au and as solubility in pyrite is retrograde au and as contents decrease as a function of increasing temperature from 200 to 500 c based on these results two major au as trends for au bearing arsenian pyrite from ore deposits are defined one trend is formed by pyrites from carlin type and orogenic au deposits where compositions are largely controlled by fluid rock interactions and or can be highly perturbed by changes in temperature and alteration by hydrothermal fluids the second trend consists of pyrites from porphyry cu and epithermal au deposits which are characterised by compositions that preserve the au as signature of mineralizing magmatic hydrothermal fluids confirming the role of this sulfide in controlling metal ratios in ore systems

pyrite physical and chemical textures pyrite may crystallize initially in forms as diverse as framboids or cubes depending upon the temperatures and pressures fluid rich diagenesis or low grade metamorphism clearly results in thorough recrystallization and the common formation of cubes once these have formed the pyrite becomes much more refractory and retains many characteristics even in deposits which have undergone penetrative deformation this is in strong contrast to the behavior of most of the accompanying sulfides which often undergo ductile deformation solid state or chemical remobilization and annealing pyrite deforms sparingly until there is brittle failure however there may be significant pyrite corrosion and regrowth during metamorphism as the result of sulfur exchange with other minerals especially pyrrhotite pyrite fabrics may also be significantly modified by pressure solution or coble creep optical microscopic examination and electron microprobe chemical mapping of pyrites from a variety of mineral deposits including several high grade metamorphic ones reveals that the pyrites frequently contain both physical and chemical textures that may be interpreted in terms of the depositional and the post depositional history of the deposits inclusions of sulfides or other minerals reveal information on the timing of the crystallization or recrystallization of the pyrite chemical mapping of elements such as ni co and as reveals information on the relative time of transport of these elements in the ore fluids

joint inversion of h v ratios and dispersion curves from seismic noise estimating the s wave velocity of bedrock 1 a joint inversion of phase velocity and h v ratio curves both obtained from seismic noise recordings permits the retrieval of the shear wave velocity structure of local sedimentary cover our inversion scheme uses a genetic algorithm and considers the influence of higher modes on the data sets encouraged by the results published previously on joint inversion parolai et al 2005 we went one step further we found using a synthetic data set that the impedance contrast at the sediment bedrock interface has a strong influence on the shape of the h v ratio curve which therefore allows the bedrock s wave velocity to be well constrained in the joint inversion procedure our observations were further confirmed using a real data set

lg body wave magnitude scaling for the continental margin around korea and japan regional body wave magnitude scalings are essential for quantification of small and moderate size earthquakes that are observed only up to regional distances crustally guided shear waves lg develop stably at regional distances in continental crusts and are minimally influenced by the source radiation patterns lg body wave magnitude scalings m b lg are widely used for assessment of sizes of regional crustal events the m b lg scaling has rarely been tested in continental margins where lg waves are significantly attenuated due to abrupt lateral variation of crustal structures we test the applicability of m b lg scaling to the eastern margin of the eurasian plate around the korean peninsula and japanese islands both third peak and root mean square rms amplitudes of lg vary significantly according to the crustal structures along raypaths causing apparent underestimation of m b lg implementation of raypath dependent quality factors q allows accurate estimation of m b lg retaining the transportability of m b lg in the continental margin around korea and japan the calibration constants for an rms amplitude based m b lg scaling are not determined to vary by region in the continental margin due to complicated crustal structures the calibration constants are determined to be distance dependent both the third peak amplitude based and rms amplitude based m b lg scalings yield accurate magnitude estimates when raypath dependent quality factors are implemented

a new concept on tectonic correlation between korea china and japan histories from the late proterozoic to cretaceous abstract the dabie sulu collision belt in china extends to the hongseong odesan belt in korea while the okcheon metamorphic belt in korea is considered as an extension of the nanhua rift within the south china block the hongseong odesan belt divides korea s gyeonggi massif into northern and southern portions the southern gyeonggi massif and the yeongnam massif are correlated with china s yangtze and cathaysia blocks respectively while the northern gyeonggi massif is part of the southern margin of the north china block the southern and northern gyeonggi massifs rifted from the rodinia supercontinent during the neoproterozoic to form the borders of the south china and north china blocks respectively subduction commenced along the southern and eastern borders of the north china block in the ordovician and continued until a triassic collision between the north china and south china blocks while subduction was occurring on the margin of the north china block high p t metamorphic belts and accretionary complexes developed along the inner zone of southwest japan from the ordovician to the permian during the subduction the hida belt in japan grew as a continental margin or continental arc collision between the north and south china blocks began in korea during the permian 290 260 ma and propagated westwards until the late triassic 230 210 ma creating the sinistral tanlu fault in china and the dextral fault in the hida and hida marginal belt in japan phanerozoic subduction and collision along the southern and western borders of the north china block led to formation of the qinling dabie sulu hongseong hida yanji belt

lg attenuation in a region with both continental and oceanic environments abstract the crustally guided shear wave lg is typically the strongest phase at regional distances lg phases are analyzed often for estimation of magnitudes of regional events the variation of lg in regions with both continental and oceanic environments has been rarely investigated we investigate lg attenuation in a plate margin area around korea and japan that is encompassed by seas and oceans the mean quality factor of lg at 1 hz q 0 is 498 the geometrical spreading exponent term is estimated as 0 75 these observations characterize the study region as a high attenuation region compared to typical intraplate continental regions low q regions are widely developed over the japanese islands with some spotted high q regions relatively high q is observed in most regions of the korean peninsula except a southeastern part where a cretaceous volcanic sediment basin exists the high q values are close to the typical q value in continental crust significantly low q of 100 or less is observed in most oceanic regions including the east sea sea of japan the pacific ocean and the south china sea the high attenuation of lg in oceanic regions suggests possible underestimation of magnitudes of oceanic events thus it appears that proper correction of lg amplitude is highly desired for accurate estimation of magnitudes of regional oceanic events

evidence of tectonic release from underground nuclear explosions in long period s waves the sh waves from 21 underground nuclear explosions at pahute mesa nts were used to investigate tectonic release the equivalent double couple representation of the tectonic release which was constrained by waveform modeling and the polarity of sp is very similar for all the explosions the average orientation is a right lateral strike slip fault trending n15 w seismic moments were determined on the basis of comparisons with two western united states strike slip earthquakes benham has the largest tectonic release moment 5 6 10 24 dyne cm and stilton 0 1 10 24 dyne cm the smallest of the events studied in general the seismic moments increase with the size of the explosion but the location of the explosion relative to previous explosions can strongly affect the tectonic release the pahute mesa events can be separated into two populations 1 events which are well separated 4 km from previous explosions and 2 those events which are close 4 km to previous explosions those events which are close to previous explosions show a marked decrease in tectonic release a least squares fit of seismic moment to event size as determined from the world wide average ab amplitude shows that the two populations are approximately parallel but offset the fact that the trends remain separated even at small yields e g pipkin and scotch suggests that for pahute mesa there is not a threshold for tectonic release since spatial position gives the best separation of high and low tectonic release events a volume model is favored for the source mechanism the preferred model is motion on a system of faults and joints

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