a study of the regional variation of low frequency around the korean peninsula we studied regional graphic 1 at 1 hz graphic 2 around the korean peninsula based on broadband vertical component seismic records of six incorporated research institutions for seismology iris global seismographic network stations and 19 korean stations of the korea institute of geoscience and mineral resources kigam using 177 seismic events with magnitudes between 5 3 and 5 7 and depths less than 50 km the reversed two station method was applied and 94 high quality interstation paths were selected from 869 possible pairs these results show high graphic 3 paths around the sea of japan east sea reflecting the typical oceanic structure and low graphic 4 paths around northeastern china related to inactive seismicity assigning these path values into 193 cells around south korea with a size of 1 by 1 we observed that the regional graphic 5 decreased gradually from east to west between 2 and 1 10 3 1 embed inline graphic 2 gif 2 embed inline graphic 3 gif 3 embed inline graphic 4 gif 4 embed inline graphic 5 gif 5 embed inline graphic 6 gif

a climosequence of soils on late quaternary volcanic ash in highland papua new guinea abstract some chemical physical and mineralogical properties of three soils developed in volcanic ash at altitudes of 1040 m 1720 m and 2350 m in papua new guinea s enga province are presented silt fraction mineralogy and total chemical analyses show that fresh ash occurs in the upper approximately 30 cm of profile at each site this fresh ash is probably only a few thousand years old and overlies an older weathered ash tomba tephra more than 50000 years old at the lowest site the majority of the primary minerals predominantly amphiboles volcanic glass and felspar and some pyroxenes have been decomposed by weathering to produce a high clay content with increasing altitude greater proportions of silt sized unweathered and partially altered primary minerals are recognised and molar ratios of calcium magnesium sodium and potassium to aluminum increase accordingly in the clay fractions allophane with al si ratios of approximately 2 0 is dominant at the highest site whereas with decreasing altitude lower proportions of allophane occur al si ratios decline and halloysite becomes dominant gibbsite is found in all three profiles

a remarkable pulse of large scale volcanism on new britain island papua new guinea new studies of the deposits from the latest caldera forming eruption the dk event at dakataua volcano new britain island papua new guinea help identify an intense space time concentration of large scale volcanism during the 7th century ad on new britain radiocarbon dating of charcoal from the dk deposits yields an age of 1 383 28 bp calibration of this result gives an age in the range ad 635 670 at 1 s d at about the same time two other volcanoes on new britain rabaul and witori also produced very large eruptions very high acidity levels in ice cores from antarctica and greenland at ad 639 and ad 640 respectively may be linked to either or both of the dakataua and rabaul eruptions another ice core high acidity level at ad 692 may be associated with the witori eruption significant volcanic risk within the new britain region is indicated by its late cenozoic history of relatively frequent large scale eruptions from as many as 8 caldera systems within an arc parallel zone about 380 km long over the last 20 ka the return period for major vei 5 eruptions in this region was about 1 0 ka and individually high frequencies of major eruptive activity were experienced at witori and rabaul the relatively short return period for major eruptions in the region would tend to increase the chance that such events could cluster in time

seismic amplitude tomography for crustal attenuation beneath china summary amplitude tomography reconstructs seismic attenuation directly from recorded wave amplitudes we have applied the tomography to amplitude data reported in the annual bulletin of chinese earthquakes and interpreted the regionally varying crustal attenuation in terms of tectonics the seismic amplitudes were originally recorded for determining the m l and m s magnitudes they generally correspond to the maximum amplitudes of the horizontal components of the short period s waves and intermediate period rayleigh waves both sets of measurements are sensitive to crustal structure the peak amplitudes from m l amplitudes spread spherically with significant dispersion and scattering m s amplitudes show cylindrical spreading with little dispersion average crustal q values for attenuation at 1 hz are 737 and 505 for m l and m s respectively with substantial regional variations frequency dependence in the attenuation is also indicated regions with the lowest attenuation high q values are beneath the south china block sichuan basin ordos platform the daxinganling and the korea craton these tend to be tectonically inactive regions which are generally dominated by intrusive and cratonic rocks in the upper crust regions with the highest attenuation low q values are beneath bohai basin yunnan eastern songpan ganzi terrain margins of the ordos platform and the qilian shan these are predominantly active basins grabens and fold belts the continental margin also highly attenuates both s and surface waves

regional seismic characteristics of the 9 october 2006 north korean nuclear test we investigate the regional seismic signature of the 9 october 2006 north korean nuclear test broadband regional data for the nuclear test and a group of earthquakes close to the test site were obtained between december 2000 and no vember 2006 epicentral distances from the stations to the test site are between 371 and 1153 km we first use these regional events to calibrate the lg wave magnitude in the network then the network is used to calculate mblg 3 93 for the north ko rean nuclear explosion using a modified fully coupled magnitude yield relation the yield of the north korean nuclear test is estimated to be 0 48 kt because of large uncertainties in the source depth the estimate is preliminary the p s type spectral ratios pg lg pn lg and pn sn are calculated for the nuclear explosion and a group of earthquakes close to the test site at frequencies above 2 hz the network averaged p s spectral ratios clearly separate the 9 october 2006 explosion from the regional earthquakes our result indicates that a single blast explosion in the north korea re gion shows different seismic characteristics from an earthquake any well coupled single blast explosion detonated in this region with yield similar to that for the north korean nuclear test has a large probability of being identified by a regional seismic network such as the one adopted in this study

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

tomographic inversion of pn travel times in china 1 pn travel times are useful for studying crustal and uppermost mantle structure and regional tectonics because they are affected by crustal velocity and thickness as well as uppermost mantle velocity and anisotropy we obtained 57 740 pn travel time picks from 5433 earthquakes and 307 stations from chinese national and provincial earthquake bulletins and the international seismological center bulletins to invert for pn velocity variation and anisotropy and station delays in china our inversion reveals significant features that correlate with surface geology the main results are as follows 1 the pn velocities show a mosaic of very fast and very slow anomalies mirroring the heterogeneous geology of china at the surface the pn velocities are high beneath the major basins in the west sichuan qaidam west tarim tulufan and junggar and low in areas of active volcanoes myanmar and western yunnan and quaternary volcanism in northern tibet in seismically active areas in north china and tien shan and in the southern part of south china the hainan plume 2 the pn anisotropy beneath the major basins in the west is generally weak strong anisotropy is found beneath high deformation regions the tibetan plateau southeastern margin of the tibetan plateau western tien shan and part of north china suggesting the anisotropy is likely related to recent large scale tectonic activity 3 a large area of north china shows prominent low pn velocity beneath archean basement with thin crust our observations are consistent with rifting lithospheric thinning and mantle upwelling in the region the pn anisotropy is consistent with a dextral simple shear in the nne direction in the lithosphere mantle during the last and ongoing major deformation period 4 the pn velocity in northern tibet is generally lower than that in the south southern tibet has significant e w structure low velocity anomalies can be traced from northern tibet across southwestern tibet and south central tibet to near the india plate anisotropy is absent beneath much of the himalaya block but consistent anisotropy with e w fast direction is present beneath the lhasa block and large anisotropy up to 4 is observed in low velocity regions of the northern and western tibet complex station delays in the eastern margin of the plateau suggest that the whole crust may be highly deformed the anisotropy pattern in the southeastern margin of the tibetan plateau suggests a mantle lithospheric deformation similar to the clockwise rotation of material observed at the surface 5 crustal thicknesses inferred from our station delays are consistent with previous models which correlate well with surface topography

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

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

seismic attenuation characteristics along the hi climb profile in tibet from lg q inversionseismic attenuation characteristics along the hi climb profile in tibet from lg q inversion

seismic lg wave q tomography in and around northeast china 1 we investigate regional variations in the lg wave quality factor q in northeast china and its vicinity with a tomographic method digital seismic data recorded at 20 broadband stations from 125 regional events are used to extract lg wave spectra tomographic inversions are independently conducted at 58 discrete frequencies distributed log evenly between 0 05 and 10 0 hz we simultaneously invert for the lg wave q distribution and source spectra at individual frequencies without using any a priori assumption about the frequency dependence of the q model and source function the best spatial resolution is approximately 1 1 in well covered areas for frequencies between 0 4 and 2 0 hz the lg q shows significant regional variations and an apparent relationship with regional geology we use a statistical method to investigate the regional variations of lg q and their frequency dependence the average q0 1 hz lg q in the entire investigated region is 414 sedimentary basins are usually characterized by lower average q0 values from 155 to 391 while volcanic mountain areas have relatively high average q0 values from 630 to 675 lg q generally increases with increasing frequency however the frequency dependence has complex nonlinear features on a double logarithmic scale indicating that the commonly adopted power law relationship may be oversimplified in a broad frequency band the frequency dependence varies in different geological areas with larger variations seen at lower frequencies

late pleistocene glaciation of the mt giluwe volcano papua new guinea abstract the mt giluwe shield volcano was the largest area glaciated in papua new guinea during the pleistocene despite minimal cooling of the sea surface during the last glacial maximum glaciers reached elevations as low as 3200 m to investigate changes in the extent of ice through time we have re mapped evidence for glaciation on the southwest flank of mt giluwe we find that an ice cap has formed on the flanks of the mountain on at least three and probably four separate occasions to constrain the ages of these glaciations we present 39 new cosmogenic 36 cl exposure ages complemented by new radiocarbon dates direct dating of the moraines identifies that the maximum extent of glaciation on the mountain was not during the last glacial maximum as previously thought in conjunction with existing potassium argon and radiocarbon dating we recognise four distinct glacial periods between 293 306 ka gogon glaciation 136 158 ka mengane glaciation centred at 62 ka komia glaciation and from 20 3 11 5 ka tongo glaciation the temperature difference relative to the present during the tongo glaciation is likely to be of the order of at least 5 c which is a minimum difference for the previous glaciations during the tongo glaciation ice was briefly at its maximum for less than 1000 years but stayed near maximum levels for nearly 4000 years until about 15 4 ka over the next 4000 years there was more rapid retreat with ice free conditions by the early holocene

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

attenuation of high frequency p and s waves in the crust of central and western tien shan in order to better understand the attenuation characteristics in the crust of the central and western tien shan orogenic belt we investigate both qp and qs values by applying the extended coda normalization method we estimate the frequency dependent attenuation of both p and s waves in the frequency band of 1 0 20 0 hz using data from local networks the average frequency relations of qp and qs have been derived as qp 61 9 f 1 21 0 08 and qs 77 6 f 1 11 0 04 by fitting a power law frequency dependence model for the study region the low q0 and high values indicate that the central and western tien shan is a tectonically and seismically active region we also find lateral variations of both qp s and qs qp values reflecting complex tectonic structures in the study area in general the relatively high attenuation areas corresponding to tectonically active regions are found beneath mountainous ranges in the central tien shan whereas the relatively low attenuation areas are associated with stable regions such as fergana basin and issyk kul lake besides regions in the central tien shan with qs qp 1 are likely partially saturated with fluids or rich in scattering heterogeneities whereas regions in the western tien shan display qs qp 1 possibly suggesting almost complete fluid saturation

significance and timing of the mid 17th century eruption of long island papua new guinea tibito tephra was first recorded in the central highlands of papua new guinea png in 1971 by the late 1970s the tephra had been mapped across tens of thousands of square kilometres traced to i

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

late quaternary tephra in the new ireland basin papua new guinea sediment cores were recovered from the new ireland basin east of papua new guinea in order to investigate the late quaternary eruptive history of the tabar lihir tanga feni tltf volcanic chain foraminifera delta 18 o profiles were matched to the low latitude oxygen isotope record to date the cores which extend back to the early part of delta 18 o stage 9 333 ka sedimentation rates decrease from 10 cm 1000 yr in cores near new ireland to similar to2 cm 1000 yr further offshore the cores contain 36 discrete ash beds mostly 1 8 cm thick and interpreted as either fallout or distal turbidite deposits most beds have compositionally homogeneous glass shard populations indicating that they represent single volcanic events shards from all ash beds have the subduction related pattern of strong enrichment in the large ion lithophile elements relative to morb but three distinct compositional groups are apparent group a beds are shoshonitic and characterised by 1300 ppm sr high ce yb and high nb yb relative to morb group b beds form a high k series with morb like nb yb but high ce yb and well developed negative eu anomalies whereas group c beds are transitional between the low k and medium k series and characterised by flat chondrite normalised ree patterns with low nb yb relative to morb a comparison with published data from the tltf chain the new britain volcanic arc and backarc including rabaul and bagana on bougainville demonstrates that only group a beds share the distinctive phenocryst assemblage and shoshonitic geochemistry of the tltf lavas the crystal and lithic rich character of the group a beds point to a nearby source and their high sr ce yb and nb yb match those of tanga and feni lavas a youthful stratocone on the eastern side of babase island in the feni group is the most probable source group a beds younger than 20 ka are more fractionated than the older group a beds and record the progressive development of a shallow level magma chamber beneath the cone in contrast group b beds represent glass rich fallout from voluminous eruptions at rabaul whereas group c beds represent distal glass rich fallout from elsewhere along the volcanic front of the new britain arc c 2003 elsevier b v all rights reserved

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

high precision location and yield of north korea s 2013 nuclear test 1 using north korea s 2009 nuclear test as reference and satellite imagery we show that the location and yield of north korea s 2013 nuclear test can be quickly and accurately determined based on seismic data north korea s 2013 nuclear test site is pinpointed by deriving relative location of north korea s 2009 and 2013 nuclear tests and using the previously determined location of the 2009 nuclear test while its yield is estimated based on the relative amplitude ratios of the lg waves recorded for both events the previously determined lg magnitude of 2009 nuclear test and burial depth inferred from satellite imagery north korea s 2013 test site is determined to be located at 41 17 26 88 n 129 4 34 68 e about 345 m south and 453 m west of its 2009 nuclear test site with a geographic precision of 94 m its yield is estimated to be 12 2 3 8 kt

a novel technique for measuring lg attenuation results from eastern canada between 1 to 10 hz spectral amplitudes of regionally recorded lg waves are studied in detail between 0 6 and 10 hz using vertical component velocity seismograms of the eastern canada telemetered network stations and a supplementary seismic research observatory type station at glen almond gac quebec we find that the site responses vary among these stations by more than a factor of 3 within the frequency range of interest furthermore they are found to be strongly frequency dependent consequently it is essential that they be taken into consideration in studies of lg wave attenuation and lg source spectra of regionally recorded seismic events we present a new method of measuring interstation surface wave attenuation which is closely related to the conventional two station method while retaining all the desirable features of the conventional two station method the new technique which we will call the reversed two station method allows simple direct one parameter determination of the lg wave attenuation from sparse spectral data in a manner unaffected by station site effects and associated instrument error the reversed two station method is successfully tested over weakly attenuating short 53 to 210 km interstation paths in eastern canada a difficult experimental condition by normal standards the lg attenuation coefficient 0 6 to 10 hz in eastern canada is found to be frequency dependent and of the form f 0 0008 f 0 81 km 1 at higher frequencies the lg attenuation appears to be essentially frequency independent this latter finding is preliminarily interpreted as evidence that regionally recorded lg waves in the canadian shield are as in the case of lg waves propagating through the structurally complex appalachian province contaminated by the high frequency coda of sn waves the lg contamination over the shield paths becomes severe starting at 14 hz twice the frequency above which the lg signal propagating over the appalachian province becomes completely dominated by non lg arrivals

constraints of crustal heterogeneity and q f from regional 4 hz wave propagation for the 2009 north korea nuclear testconstraints of crustal heterogeneity and q f from regional 4 hz wave propagation

magnitude estimation and source discrimination a close look at the 2006 and 2009 north korean underground nuclear explosions north korea detonated its first known nuclear device a moderate sized event in the northeastern corner of the korean peninsula on 9 october 2006 a second one several times more powerful was set off nearby on 25 may 2009 both were recorded at high signal to noise ratio snr by a modern broadband 0 03 30 hz network of seismographs deployed since 2004 along the sino korean border and by station mdj due north of ground zero spanning a wide range of station azimuth 259 11 the near regional 1 3 3 3 paths are all purely continental and away from continental margins making the resulting data uniquely suited for assessing the capabilities of an out country network to verify the compliance by north korea with a future comprehensive nuclear test ban treaty the mblg magnitudes for the 2006 and 2009 nuclear explosions were determined anew giving 4 32 0 13 and 4 86 0 13 respectively we show that the ms mblgmethod correctly differenti ates these nuclear explosions from natural earthquakes although the differentiation was not achieved in studies based on published mblg values an analysis of the pg lg ratio derived from recordings of the two nuclear tests and of four regional earthquakes selected for their comparable magnitudes 4 2 mb 4 8 reveals that the ratios associated with the explosion and earthquake populations showed surpris ingly little overlap for a broad frequency range of 3 to 11 hz in principle ms mb can also be used to correctly identify the nuclear tests as explosions but the mb measure ment for such moderate sized events is not as robust as the mblg measurement rendering this traditionally favored method less practical

attenuation of lg in the western us using the usarray 1 the unprecedented breadth and density of the usarray allows us to resolve lateral variations of 1 hz lg attenuation to 0 5 degrees over much of the western united states we collected over 31 000 lg amplitudes from 547 events and 408 stations of the initial usarray footprint two dimensional tomographic inversion yielded q ranging from 60 to 550 with a variance reduction of 47 relative to the best fit constant q model q 155 q is low over most of the region with lowest values associated with recent volcanic activity and active shear zones high q is found in older stable crust notably the colorado and columbia plateaus while smaller islands of high q are associated with batholiths including the sierra nevada peninsular and bitterroot ranges the western mojave and okanogan highlands as well as other areas of competent crust such as the harcuvar range and two topographically bounded blocks in the basin and range

lateral variations of crustal seismic attenuation along the indepth profiles in tibet from lg q inversion 1 fourier spectra of crustal guided lg waves are collected to study seismic attenuation or q along the indepth profiles the 1 hz lg q q0 values are measured between many pairs of two stations and input to a back projection algorithm to obtain laterally varying q0 models along the indepth iii profile in central tibet the q0 model consists of low and nearly constant values of 90 these low values are consistent with abnormally high temperature as well as partial melts in the crust along the indepth ii profile in southern tibet the q0 values increase southward they are extremely low 60 over the northernmost segment but increase by a factor of 2 over a distance of 100 km between the indus yalong suture and the kangmar dome farther south and into the high himalayas q0 values are higher than 300 regional rayleigh waves observed along the northern indepth ii profile are used to infer a low velocity low q layer at midcrustal depths between 15 and 30 km in southern tibet the aqueous fluid trapped in the upper crust and a midcrust partial melting zone associated with the underthrusting of the indian lithosphere are the likely causes of the high lg attenuation in southern tibet low q rather then a systematic lg conversion along a dipping moho is the main cause of the previously observed lg blockage over paths crossing the southern tibetan boundary

a revised age of ad 667 699 for the latest major eruption at rabaul the most recent major eruption at rabaul was one of the largest known volcanic events at this complex system having a volcanic explosivity index vei rating of 6 the eruption generated widespread pumice lapilli and ash fall deposits and ignimbrites of different types the total volume of pyroclastic material produced in the eruption exceeded 11 km3 and led to a new phase of collapse within rabaul caldera initial 14c dating of the event yielded an age of about 1400 years bp and the eruption became known as the 1400 bp eruption previous analyses of the timing of the eruption have sought to link it to events in ad 536 and ad 639 however we have re evaluated the age of the eruption using the bayesian wiggle match radiocarbon dating method and the eruption is now thought to have occurred in the interval ad 667 699 the only significant equatorial eruptions recorded in both greenland and antarctic ice during this interval are at ad 681 and ad 684 dates that coincide with frost rings in bristlecone pines of western usa in the same years definitively linking the rabaul eruption to this narrow age range will require identification of rabaul tephra in the ice records however it is proposed that a new working hypothesis for the timing of the most recent major eruption at rabaul is that it occurred in the interval ad 681 684

yield estimation of the 25 may 2009 north korean nuclear explosion we collect nine vertical component broadband seismograms from the 25 may 2009 north korean nuclear explosion for a regional seismic network in which eight stations also recorded the 9 october 2006 north korean nuclear test comparing the observed waveforms and spectra from the two events we estimate that the amplitudes of the records from the second event are approximately five times those from the first one additionally we use 599 vertical broadband seismograms from 82 regional events recorded on the regional network between december 1995 and may 2009 to calibrate the network lg wave magnitude the calibrated network is used to calculate the lg wave body wave magnitude m b lg 4 53 for the 25 may 2009 north korean nuclear explosion based upon 15 first arrivals from the two north korea nuclear explosions the regional pn velocity in the northeast china north korea region is calculated to be 8 0 km s this result along with the regional geological structures suggests that the north korean test site nkts is located at a relatively stable continental region we thus use a modified fully coupled magnitude yield relation to estimate the explosion yield and the result shows that the yield of the 25 may 2009 north korean nuclear test is approximately 2 35 kt under the minimum burial depth assumption online material epicentral parameters computed m b lg and corrected m b lg for 82 events used in the study

temporal variation in the interhemispheric 14c offset contemporaneous tree ring dated wood from trees in the northern and southern hemispheres gives different 14c dates previous studies vogel et al 1986 1993 using wood from south africa and the netherlands have shown depletion s of 4 56 0 85 0 and 5 12 0 62 0 respectively this trans lates to age differences of 36 7 and 41 5 years yrs with the southern hemisphere giving the older dates more recently stuiver and braziunas 1998 have shown that an offset of 23 4 yrs exists between combined 19th century wood measure ments from tasmania and chile in the southern hemisphere and the west coast of the u s washington in the northern hemisphere in this study measurements on contemporaneous decadal samples of oak from the british isles and cedar from new zealand over the period 1725 to 1885 ad show a deple tion of 3 4 0 589 00 27 2 4 7 yrs however data after 1895 ad has a mean offset of 0 66 1 06 o 5 3 8 5 yrs with increased variance compared to 19th century data this we believe is attributable to anthropogenic fossil fuel which due to its long residence time in the earth has long since lost any 14c component and when burned preferentially depletes the northern hemisphere atmosphere of 14c

crustal structure of western tibet revealed by lg attenuation tomography abstract the lateral lg wave attenuation in western tibet and surrounding regions is studied a total of 706 two station method tsm and 533 reverse two station method rtsm pairs are generated from 282 regional earthquakes the earthquakes are recorded at 48 seismic stations operated across western kunlun and western tibet regions the lg phases are extracted from the vertical component of seismograms with magnitude greater than 4 6 mb and focal depth less than 50 km to measure the tsm and rtsm lg q at 1 hz q0 the lgq0 tomography map is generated with grid size 0 5 0 5 using the least squares orthogonal factor decomposition lsqr algorithm lateral variation of lg attenuation is found to exist across the region the results provide new insights into the attenuation properties of the crust and its linkage with regional geodynamics the low lgq0 200 is revealed in the central part of lhasa terrane in western tibet from both tsm and rtsm images the high lgq0 values complemented with the high pn velocities beneath the central part of lhasa terrane reveal the trace of underthrusting indian lithosphere beneath the western tibet

lg wave attenuation in the isparta angle and anatolian plateau turkey we estimate lg wave attenuation using local and regional seismic phases in the isparta angle and the anatolian plateau turkey the isparta angle ia is a tectonically active zone forming the boundary between the african plate and the anatolian plateau and is currently undergoing n s extensional deformation the anatolian plateau contains many intra continental faults including the north anatolian fault zone and the east anatolian fault zone as well as the menderes massif a large waveform data set was compiled from a variety of local and regional seismic networks including 121 digital seismic stations broad band and short period between 1999 and 2008 spanning the ia the anatolian plateau and azerbaijan the data set was used to determine the nature of lg wave propagation and characterize the nature of seismic attenuation within the crust of these regions lg waveforms were used to calculate the frequency dependent lg qo and lg eta a wide range of lg qo values was obtained between 52 6 and 524 227 low lg qo values 90 155 are calculated towards the north of ia iskenderun gulf and its vicinity bingol karliova izmit and its vicinity lg qo values are especially low 90 along the menderes massif and the aksehir simav fault zones this may be due to intrinsic attenuation of lg associated with the partially molten crust and young volcanism the high lg qo values 350 are probably caused by the crust not being subject to large amounts of extensional deformation like the antalya gulf and apparently being thick enough to support lg propagation relatively higher values along the border of this subduction zone and plate boundary might be related to the taurus mountain belts and bitlis zagros suture zone the lateral frequency dependency lg eta is also consistent with high tectonic activity in this region

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

attenuation tomography of the yellow sea korean peninsula from coda source normalized and direct lg amplitudes we invert for regional attenuation of the crustal phase lg in the yellow sea korean peninsula yskp using three different amplitude attenuation tomography methods the first method solves for source site and path attenuation the second method uses a scaling relationship to set the initial source amplitude and interpret the source term after inversion the third method implements a coda derived source spectral correction by comparing methods with slightly different assumptions we are able to make a more realistic assessment of the uncertainties in the resulting attenuation maps than is obtainable through formal error analysis alone we compare the site source and path terms produced by each method and comment on attenuation which correlates well with tectonic and topographic features in the region source terms correlate well with each other and with magnitude site terms are similar except for two stations that are located in a region that has the greatest difference in path term which demonstrates the site path trade off another region of path term difference has the fewest crossing paths where the tomography method employing the coda derived spectral correction may perform more accurately since it is not as susceptible to the source path trade off the bohai bay basin an area of extension is a region of high attenuation and regions of low attenuation occur along topographic highs located in the da xin an ling and changbai mountains and mount taishan

pgq model for nepal himalaya abstract we investigate the spatial variations of pg attenuation structure in nepal himalaya we implement the two station method on 2325 waveforms obtained from 435 events recorded at 151 stations deployed across nepal himalaya to measure the pg wave quality factor q these station station measurements are inverted further for investigating the spatial variations of pg attenuation using a back projection algorithm the model contains variations across the region with much of the region being dominated by high attenuation it is observed that the areas around the existing faults and lineaments exhibit very low q values a few exceptional high q pockets are observed to be limited predominantly in the north western side of our study area we hypothesize that intrinsic attenuation plays a major role in causing the high apparent pg attenuation in the crust of nepal himalaya this may be mainly caused by highly pressurized fluids trapped within a thin low velocity layer lvl at shallow depths moreover it is interesting to observe that all the past earthquakes of m w 7 since 1934 fall into the regions of low q values but not the lowest it may be anticipated that the very low q areas are too weak to sustain the accumulation of high energy release during a large magnitude earthquake therefore the observed low q structures across the study area may imply a weak crust and subsequently a favorable zone for future rupture

new insights into the lithosphere beneath the superior province from rayleigh wave dispersion and receiver function analysis we study the azimuthally anisotropic upper mantle structure of the superior craton and grenville province in ontario canada using rayleigh wave phase velocity data in the period range 40 160 s 152 two station dispersion measurements are combined in a tomographic inversion that solves simultaneously for isotropic and anisotropic terms using a least squares technique we perform a series of tests to derive optimal regularization smoothing and damping and to assess the resolution of and trade offs between isotropic and anisotropic anomalies the tomographic inversion is able to resolve isotropic phase velocity anomalies on a scale of 200 300 km and to distinguish between different anisotropic regimes on a 500 km scale across the study region isotropic phase velocity anomalies in the tomographic model span a range of up to 2 per cent around a regional average which is similar to the canadian shield dispersion curve of brune dorman 1963 with phase velocities up to 3 per cent above global reference models the amplitude of azimuthal phase velocity anisotropy reaches a maximum of 1 2 per cent a clear east west division of the study area based on both isotropic phase velocity anomalies and azimuthal anisotropy is apparent in the western superior isotropic phase velocities are generally higher than the regional average anisotropy is observed at all periods with ene wsw to ne sw fast propagation directions at periods 120 s the anisotropy likely results from frozen lithospheric fabric aligned with tectonic boundaries whereas the anisotropy at longer periods is interpreted to arise from present day sublithospheric flow the fast directions from published sks measurements are close to the fast rayleigh wave propagation directions throughout the period range sampled and the large sks splitting times may be accounted for by this near coincidence of fast propagation directions across most of eastern ontario phase velocities are lower than the regional average fast propagation directions rotate from nw se at 40 130 s period to wnw ese at periods 140 160 s the results suggest a difference in fast propagation directions between the anisotropic fabric frozen into the lithosphere and the fabric due to current and recent sublithospheric flow the superior craton and grenville province are characterized by large scale structural variations that reflect the complex tectonic history of the region this study highlights differences between the characteristics of eastern and western ontario and indicates the occurrence of multiple layers of anisotropy in the subcratonic upper mantle

how to invert multi band regional phase amplitudes for 2 d attenuation and source parameters tests using the usarray we inverted for laterally varying attenuation absolute site terms moments and apparent stress using over 460 000 lg amplitudes recorded by the usarray for frequencies between 0 5 and 16 hz corner frequencies of wells nevada aftershocks obtained by independent analysis of coda spectral ratios controlled the tradeoff between attenuation and stress while independently determined moments from st louis university and the university of california constrained absolute levels the quality factor q was low for coastal regions and interior volcanic and tectonic areas and high for stable regions such as the great plains and colorado and columbia plateaus q increased with frequency and the rate of increase correlated inversely with 1 hz q with highest rates in low q tectonic regions and lowest rates in high q stable areas moments matched independently determined moments with a scatter of 0 2 nm apparent stress ranged from below 0 01 to above 1 mpa with means of 0 1 mpa for smaller events and 0 3 mpa for larger events stress was observed to be spatially coherent in some areas for example stress was lower along the san andreas fault through central and northern california and higher in the walker lane and for isolated sequences such as wells variance reduction relative to 1 d models ranged from 50 to 90 depending on band and inversion method parameterizing frequency dependent q as a power law produced little misfit relative to a collection of independent multi band q models and performed better than the omega square source parameterization in that sense amplitude residuals showed modest but regionally coherent patterns that varied from event to event even between those with similar source mechanisms indicating a combination of focal mechanism and near source propagation effects played a role an exception was the wells mainshock which produced dramatic amplitude patterns due to its directivity and was thus excluded from the inversions the 2 d q plus absolute site models can be used for high accuracy broad area source spectra magnitude and yield estimation and in combination with models for all regional phases can be used to improve discrimination in particular for intermediate bands that allow coverage to be extended beyond that available for high frequency p to s discriminants

uppermost mantle velocities beneath china and surrounding regions 1 seismic p wave velocity variations in the uppermost mantle beneath china are tomographically imaged using pn wave travel time data the average velocity of the mantle lid beneath china is 8 05 km s with a range from 0 30 km s to 0 35 km s eastern china has slower mantle velocities and a thinner crust than western china different inversions performed for shorter ray path and longer ray path data sets separated the shallow and deep structure within the mantle lid velocities in the lower lid are no more than 0 2 km s faster than at the top the fastest velocities are beneath cratons which remained relatively undeformed despite orogenic events around their margins the pn velocity beneath southern tibet is faster than that beneath northern tibet suggesting that this contrast delineates the northern edge of the indian lithosphere on the southeastern margin of the tibetan plateau the panxi rift slow pn velocity exists in the lithosphere due to the transextensional tectonic environment in eastern china extension of the north china block produced a series of nne ssw trending rifts that cause slow mantle lid velocities these slow velocities extend to the base of the mantle lid suggesting that late cenozoic pacific subduction drove the rifting both high temperature and hydration may contribute to these low uppermost mantle velocities the shanxi rift along the east margin of the ordos platform is characterized by a slow mantle velocity in contrast the yinchuan rift on the west margin does not show any uppermost mantle velocity anomaly

stratigraphy age and correlation of two widespread late holocene tephras preserved within lake kutubu southern highlands province papua new guinea sediment cores were retrieved from lake kutubu the largest upland lake in papua new guinea to assess palaeoenvironmental baselines two prominent tephra layers were encountered within the cores using a combination of core stratigraphy sediment properties and geochemical characterization electron microprobe and laser ablation inductively coupled plasma mass spectrometry techniques we were able to correlate these tephras with tibito and olgaboli tephras both previously described at adjacent distal localities glass shard compositional data of tibito tephra from lake kutubu kuk swamp and from proximal volcaniclastic successions from long island are indistinguishable and this similarity strongly supports long island as the eruptive source for olgaboli tephra the location of its eruptive source is less certain but the glass shard compositional data indicate a karkar island source the occurrence of tibito and olgaboli tephras in lake kubutu sediments extends their known distributions further south west into the southern highlands region and affirms their importance as inter regional stratigraphic markers of late holocene age that have considerable potential for use in future palaeoenvironmental archaeological and volcanic hazard and or impact studies

lg attenuation near the north korean border with china part ii model development from the 2006 nuclear explosion in north korea an underground nuclear explosion was set off on 9 october 2006 in north korea the event was recorded at near regional to regional distances over purely continental paths by a network of broadband seismographs located along the northern edge of the korean peninsula the event provided the first window of opportunity to make a reliable measurement of lg wave attenuation in northernmost north korea where the regional phase propagation characteristics are poorly known the results of our analysis show q0 317 14 and 0 343 0 024 in close agreement with the corresponding values obtained of late using a completely different methodology and an independent set of seismic recordings in an adjacent region to the northwest in southern jilin and in liaoning provinces in china

a first look at oxygen isotope records from modern and holocene aged gastropod stenomelania shells from lake kutubu papua new guinea the lake kutubu project was funded by the department of archaeology and natural history at the anu and the australian institute of nuclear science and engineering ainse grants aingra08028 and aingra10113 obtained by s g h

lg attenuation tomographic models of himalaya and southern tibet abstract we investigate the lg attenuation structure of the crust beneath the tectonically complex himalaya and southern tibet regions adopting a tomographic regionalization method a total of 1671 earthquake waveforms registered at 38 seismic stations operated in the region are selected for the initial lgq measurements using the standard two station method q0 1 hz lgq values of 76 high quality interstation paths are finally considered as input for the tomographic inversion the estimates of q0 exhibit distinct variations in the crustal attenuation from north to south across the whole region the zones of lowest q0 values

strong lg wave attenuation in the middle east continental collision orogenic belt abstract using lg wave q tomography we construct a broadband crustal attenuation model for the middle east the q lg images reveal a relationship between attenuation and geological structures strong attenuation is found in the continental collision orogenic belt that extends from the turkish and iranian plateau to the pamir plateau we investigate the frequency dependence of q lg in different geologic formations the results illustrate that q lg values generally increase with increasing frequency but exhibit complex relationships both with frequency and between regions an average q lg value between 0 2 and 2 0 hz q lg 0 2 2 0 hz may be a critical index for crustal attenuation and is used to infer the regional geology low q lg anomalies are present in the eastern turkish plateau and correlate well with low pn velocities and cenozoic volcanic activity thus indicating possible partial melting within the crust in this region very strong attenuation is also observed in central iran the afghanistan block and the southern caspian sea this in line with the previously observed high crustal temperature high conductivity layers and thick marine sediments in these areas suggests the high lg attenuation is caused by abnormally high tectonic and thermal activities

exploiting regional amplitude envelopes a case study for earthquakes and explosions in the korean peninsula abstract we introduce a new method to use narrowband regional amplitude envelopes for event analysis building on the success of the coda wave method we construct synthetic template envelopes that attempt to fit the entire waveform including multiple direct phases and their coda across a broad frequency band the method makes use of our understanding of earthquake and explosion source models regional wave propagation and the relationship between direct amplitudes and their respective codas we demonstrate the power of the method by examining earthquake and nuclear explosions in the korean peninsula at regional distance stations mdj mudangjing china and tjn taejon south korea in order to implement the method however we need to account for propagation through the use of an attenuation model for the region which we have developed in addition to an empirical correction to provide for unaccounted effects in the direct to coda transfer functions under the assumption that our explosion and attenuation models and the empirically obtained p to p coda and s to s coda transfer functions are correct we determine that the 2006 test by the democratic people s republic of korea dprk is consistent with a yield between 200 and 800 tons and a depth between 20 and 300 m with our best fit at 500 tons at a depth of 100 m similarly the 2009 dprk test is consistent with a yield range of 1 5 kt and a depth range of 70 600 m with our best fit at 2 kt at a depth of 200 m

towards a weathering model of mount lamington ash papua new guinea abstract the mount lamington ash halo has been studied at six sites both close to and distant from the volcano negligible alumina occurs in the seepage waters from the ash and so alumina is assumed constant during weathering in andesitic ashes weathering to allophane an approximation to a first order reaction was found in 1968 and is confirmed here with given infiltration and silica concentration the weathering rate constant decreases with increasing content of weathering minerals and increasing thickness of ash being weathered the rate constant also increased with increasing infiltration and decreasing median size of the ash the total weathering rate is the product of the thickness percentage of ash being weathered and the weathering rate constant the total weathering rate is the same for thick less weathered proximal ashes as it is for the thin more weathered distal ashes first order kinetics imply a high rate of leaching decreasing with time but continual burial under new ash at a nearly constant rate leads to linear leaching of the upper part of the profile the leaching rate decreases exponentially with depth and appears to ignore buried topsoil barriers it is possible to construct weathering models exploring the rate constant and to link it with leaching rates two thirds of the loss on weathering is silica and there is a total leaching rate of 3 4 mg sio 2 cm 2 year 1 as on basalt in hawaii and on andesite in st vincent water analyses show silica concentrations in the ash of 17 35 ppm and in draining streamlets of 9 20 ppm measured concentrations agree with calculated concentrations from the weathering data silica concentrations are similar in other humid tropical rivers

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

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

seismic attenuation characteristics along the hi climb profile in tibet from lg q inversion we investigate the q of crustal lg waves along the himalayan tibetan continental lithosphere during mountain building hi climb profile in tibet using a reliable two station method four earthquakes of m 5 5 recorded along a 800 km long densely spaced seismic profile are used to extract lg wave spectra one hundred seven high quality interstation paths that allow us to use the standard two station method for lg q measurement are selected from 2369 possible pairs by using those 107 interstation q0 1 hz lg q values as input lateral variations in attenuation char acteristics are derived through inversion the region has q0 estimates ranging from 88 5 to 165 15 with the lowest value in the qiangtang terrane and the highest across some part of the lower himalaya the lowest value is attributed to the high poisson s ratio higher temperatures as well as partial melts in the crust the results do not contain any detectable variation in q0 either across the himalaya tibet collision zone i e the indus tsangpo suture zone or along the major bangong nujiang suture zone bnsz consistent low q0 values along the hi climb profile manifest the presence of omnipresent partial melting of the crust throughout the plateau