propagation characteristics of lg across the tibetan plateau abstract we present the results of a study on the propagation of lg within the tibetan plateau we analyze over 1200 seismograms for lg propagation from 185 local and regional earthquakes recorded at distances from 150 to 2000 km 52 of which are located within the tibetan plateau although the propagation of lg has been observed across most of asia lg has not been observed for paths crossing the tibetan plateau we analyze paths that cross the plateau boundaries and paths contained entirely within the tibetan plateau lg is generated within the tibetan plateau and can propagate to epicentral distances of at least 600 km for events located outside of the tibetan plateau lg is either absent or severely diminished for paths that cross both the himalayan and kunlun ranges confirming that the margins of the plateau weaken lg transmission based on the observations from our qualitative analysis we invert lg amplitudes for event station paths that are confined to the tibetan plateau to estimate the quality factor q the inversion yields a frequency dependent q function q f 366 37 f 0 45 0 06 0 5 f 16 h z similar observations in other areas indicate that frequency dependent apparent q within the tibetan plateau is well below that expected for a typical continental interior instead it has a frequency dependence that is characteristic of a tectonically active region

synsedimentary collapse of portions of the lower blomidon formation late triassic fundy rift basin nova scotia a chaotic mudstone unit within the lower blomidon formation late triassic has been traced for 35 km in the mesozoic fundy rift basin of nova scotia this unit is characterized by highly disrupted bedding that is commonly cut by small 0 5 m domino style synsedimentary normal faults downward movement of material geopetal structures variable thickness and an irregular partially faulted contact with the overlying unit the chaotic unit is locally overlain by a fluvial sandstone which is overlain conformably by mudstone although the thickness of the sandstone is highly variable the overlying mudstone unit exhibits only gentle regional dip the sandstone unit exhibits numerous soft sediment deformation features including dewatering structures convoluted bedding kink bands and convergent fault fans the frequency and intensity of these features increase dramatically above low points at the base of the sandstone unit these stratigraphic relations suggest buried interstratal karst the subsurface

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

the anatomy and provenance of thick volcaniclastic flows in the cretan basin south aegean sea abstract santorini volcano has been the largest source of volcaniclastic sediment in the eastern mediterranean during the late quaternary a dozen cores from the cretan basin south of santorini have sampled two megabeds that consist of gravity emplaced volcaniclastic sequences the uppermost megabed u consists of a succession of five u 5 u 1 base cut out turbiditic units lower megabed a is a single turbiditic event only the uppermost u 2 and u 1 turbidites are separated from the underlying beds by hemipelagic marls the texture and composition of the u and a megabeds closely match the texture and composition of the fine vitric ash of the minoan deposits on santorini islands dating from about 3500 yr bp these megabeds are therefore attributed to rapid accumulation of separate gravity flows fed by the minoan eruption except for the upper u 2 and u 1 turbidites deposited from subsequent gravity flows transporting eroded volcaniclastic sediments with the exception of the margin south of santorini dozens of cores retrieved around the margins of the cretan basin have a continuous late quaternary succession that shows no evidence for massive sediment remobilization into the deeper basin including the passage of the minoan tsunami extensive high resolution 3 5 khz records revealed the acoustic character architecture and distribution of the u and a megabeds and four underlying late quaternary volcanogenic megabeds in the cretan basin the acoustic facies of megabeds are typical of megaturbidites and consist of an upper transparent lower velocity layer that corresponds to the fine grained upper turbiditic silt and clay section and a lower strongly reflective higher velocity section that corresponds to the lowest coarser grained base of the turbidite that is developed over a sharp erosional surface penetration of the high resolution records reveals the existence of at least six megabeds correlation with core lithology and the physical properties of the various lithofacies including down core velocity profiles has allowed us to determine the thickness and volumes of the upper four megabeds which are u 9 m thick volume 3 7 km 3 a 25 m thick volume 12 2 km 3 b 22 m thick volume 10 3 km 3 c 15 m thick volume 8 km 3 these thick megabeds are the uppermost products of repeated explosive eruption of santorini in the late quaternary calculated sedimentation rates from and after the minoan eruption are 9 4 m 1000 yr that rise to over 15 7 m 1000 yr if megabed b was also deposited during this eruption

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

clastic dykes in east belgium evidence for upper pleistocene strong earthquakes west of the lower rhine rift segment fissures of seismic origin are described from terrace deposits of the meuse river in the liege maastricht area west of the lower rhine roer rift segment though associated with hydroplastic deformation of the sediments they are not injection structures they are interpreted as tension cracks resulting from local deformation of susceptible layers inferred to be due to cyclic loading by seismic waves the fissures have been tilled afterwards from above by vertically laminated sands and silts the distribution of the fissured areas and the special features of some ground cracks suggest that they could be linked to more than one earthquake between 650 and l00 ka bp by comparison with liquefaction phenomena described in relation to actual earthquakes the failure of the meuse terrace deposits could have been produced by seismic events of m l 6 5

modelling seismites with a digital shaking table abstract soft sediment deformation structures induced by seismically triggered liquefaction and or fluidization seismites have been reproduced with a digital shaking table we have used natural sediments with variable granulometric ranges clay silt and sand and an earthquake simulator that is able to reproduce real tridimensional seismograms acceleration and pore pressure recording allowed us to follow liquefaction and or fluidization processes in unconsolidated sediments during earthquakes different types of seismites were produced by variations in the tested sedimentary column

earthquakes of the holocene geologic studies of earthquakes involve mapping of coseismic surface faulting and secondary deformation from historical events trenching and geomorphic analysis to define the timing and size of past earthquakes and investigations of fault zone structure and geometry in both unconsolidated sediments and bedrock this research is now being referred to as paleoseismology seismic geology and earthquake geology since the mid 1970s it has led to some of the most exciting and important contributions to the understanding of earthquake behavior in space and time hanks 1985 allen 1986 the present report is the first of what is hoped will become a regularly contributed summary of the geologic aspects of the study of earthquakes

source effects on regional seismic discriminant measurements source effects on high frequency regional seismic discriminant measurements involving p s type ratios pn lg pg lg are isolated for earthquakes in southern california and southern nevada the scatter in earthquake population discriminant measurements for fixed propagation paths is statistically analyzed to assess the spatial and frequency dependent contributions from source radiation pattern and source depth variations along with variable near source scattering this is useful because procedures for reducing the variance caused by propagation effects must be constrained by knowledge of the intrinsic scatter resulting from independent source effects for which corrections are not available without a priori knowledge of the source type and depth broadband waveforms for earthquakes near the nevada test site nts and in southern california recorded at stations of the livermore nts network lnn the caltech terrascope network and the berkeley digital seismic network bdsn are used to obtain pg lg and pn lg measurements and to assess source depth and mechanism contributions to measurement variance pn lg and pg lg spectral amplitude ratios for several frequency bands between 0 5 and 10 hz from vertical velocity waveforms are computed for a total of 18 tightly located clusters of earthquakes for each cluster we examine the correlations between observed pn lg and pg lg ratios and estimated source depths or predictions based on previously determined source mechanisms focal mechanism predictions do not match the observations well likely due to strong near source scattering and directivity effects that overwhelm the point source radiation pattern however the data do show significant scatter even for sources only a few kilometers apart source depth produces some coherent trends which can be emphasized by averaging results from multiple stations these trends vary from region to region presumably due to specific local crustal layering but most of the variance is not deterministically predictable and appears to arise from strong variations in near source scattering variance estimates for logarithmic amplitude ratios normalized by mean amplitude ratios vary from 0 01 to 0 05 for different phase pairs frequency dependent variations of the mean variance minimum and maximum amplitude ratio parameters show strong distance dependence out to about 300 km and then appear to become independent of event station distance these variance parameters appear to be suitable for use in spatial interpolations of observed p s type ratios for a specific unidentified event path as needed for nuclear test monitoring

plate boundary earthquakes and tsunamis of the past 5500 yr sixes river estuary southern oregon eleven plate boundary earthquakes over the past 5500 yr have left a stratigraphic signature in coastal wetland sediments at the lower sixes river valley in south coastal oregon within a 1 8 km2 abandoned meander valley 10 buried wetland soils record gradual and abrupt relative sea level changes back in time to 6000 yr ago an additional youngest buried soil at the mouth of the sixes river subsided during the a d 1700 cascadia earthquake multiple lines of evidence indicate that tectonic subsidence caused soil burial including permanent relative sea level rise following burial lateral continuity of buried soil horizons over hundreds of meters diatom assemblages showing that sea level rose abruptly at least 0 5 m and sand deposits on top of buried soils demonstrating coincidence of coseismic subsidence and tsunami inundation for at least two of the buried soils liquefaction of sediment accompanied subsidence the 11 soil burial events took place between 300 and 5400 yr ago yielding an average recurrence interval of plateboundary earthquakes of 510 yr comparing paleoseismic sites in southern washington and south coastal oregon with the sixes river site for the past 3500 yr indicates that the number and timing of recorded plate boundary earthquakes are not the same at all sites in particular a sixes earthquake at 2000 yr ago lacks a likely correlative in southern washington therefore unlike the a d 1700 cascadia earthquake some cascadia plate boundary earthquakes do not rupture the entire subduction zone from southern oregon to southern washington in the lower sixes river valley the upperplate cape blanco anticline deforms sediment of late pleistocene and holocene age directly above the subduction zone differential tectonic subsidence occurred during two of the plate boundary earthquakes when a blind upper plate reverse fault for which the cape blanco anticline is the surface fold slipped coseismically with rupture of the plate boundary during these two earthquakes sites 2 km from the anticline axis subsided 0 5 m more than sites 1 km from the axis

last stage of the japan sea back arc opening deduced from the seismic velocity structure using wide angle data the japan sea is one of the most well studied back arc basins in the northwestern pacific the seismic crustal model however has been inadequate to elucidate the detailed opening model of the japan sea in 2002 to clarify the late stage of the formation style of the japan sea opening a seismic experiment using 35 ocean bottom seismographs obss an air gun array and a multichannel hydrophone streamer was undertaken in the areas from the southwestern yamato basin the oki ridge and the southwestern oki trough to the coast of the southwestern japan island arc the crusts beneath the southwestern yamato basin and the oki ridge are estimated as having approximately 13 km and 19 5 km respectively the upper and lower crusts of the southwestern yamato basin are approximately 3 2 km and 8 km thick respectively those of the oki ridge are approximately 8 2 km and 10 5 km thick respectively the upper crust of the oki ridge thickens more steeply than that of the southwestern yamato basin however the lower crust thickens more gently the crustal structure of the southwestern yamato basin shows the extended continental crust accompanied with the opening of the japan sea a remarkable structural characteristic the upper crust being thinner than the lower crust caused by listric or complicated normal faults developed in the upper crust of the southwestern yamato basin this deformed upper crust is a common structural characteristic in the southern japan sea which includes the yamato basin the southern yamato basin including the southwestern yamato basin has the thinnest upper and lower crusts in the japan sea for that reason it is suggested that the southern yamato basin had the strongest deformation by a back arc opening and that the period of the opening in the southern yamato basin had been longest in the southern japan sea the formation process of the southern yamato basin is inferred to have two stages rifting and extension of continental crust separating the northeastern and southwestern japan island arcs from the asian continent and further the extension affected by the rotation of the southwestern japan island arc

frequency dependent attenuation in eastern kazakhstan and implications for seismic detection thresholds in the soviet union abstract the frequency dependent attenuation of regional seismic phases recorded by three stations near the nuclear explosion test site in eastern kazakhstan is estimated by inverting spectra from 21 events with magnitudes between 2 3 and 4 6 at distances between 200 and 1300 km the pn spectra are inverted between 1 and 10 hz and the lg spectra are inverted between 0 5 and 2 5 hz the motivation for this study is that previous estimates of detection capability in the soviet union are based on data recorded in other regions eastern north america and scandinavia and therefore have large uncertainty the data recently recorded in eastern kazakhstan provide an excellent opportunity to compare regional wave propagation and noise characteristics at these sites to conditions assumed in previous detection capability simulations it is found that attenuation in eastern kazakhstan is not much different from attenuation in scandinavia but it is greater than attenuation in eastern north america this implies that estimates of detection thresholds that assume attenuation like that observed in eastern north america will be lower than estimates of detection thresholds that assume attenuation like that observed in eastern kazakhstan or scandinavia however it is not known how well data recorded in eastern kazakhstan represent conditions in other areas of the soviet union

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 near the north korean border with china part i model development from regional earthquake sources we have collected broadband data from three seismic networks two portable and one permanent in a remote part of northeast china bordering north korea the combined network coverage allows first hand investigations of seismic wave propagation in a region of import for nuclear test ban monitoring research application of the reversed two station method to the newly acquired data has pro duced stable measurements of the quality factor q q0f for lg waves the re sults a weighted regional average over 23 interstation paths involving 51 events and 21 stations point to 1 hz q or q0 of 345 and of 0 38 in a jarring incongruity with what appears to be a popular perception of the region as being of very low attenuation for lg waves the results also show that lg q varies from one interstation path to another the highest lg wave attenuation 110 q 0 140 is found along intersta tion paths that crossed two recently active volcanoes huangyishan and chang baishan the subregion exhibiting the next highest lg attenuation is bohai an extensional basin known to feature above average heat flow

seismotectonic implications of sand blows in the southern mississippi embayment we explore seismically induced sand blows from the southern mississippi embayment and their implications in resolving the question of near or distal epicentral source region this was accomplished using aerial photography field excavations and cone penetration tests our analysis shows that three sand blow fields exhibit a distinct chronology of strong ground motion for the southern embayment 1 the ashley county arkansas sand blow field near the arkansas louisiana state border experienced four holocene sand venting episodes 2 to the north the desha county field experienced at least three episodes of liquefaction and 3 the lincoln jefferson counties field experienced at least one episode cone penetration tests cpt conducted in and between the sand blow fields suggest that the fields may not be distal liquefaction associated with new madrid seismic zone earthquakes but rather are likely associated with strong earthquakes on local faults this conclusion is consistent with the differences in timing of the southern embayment sand venting episodes and those in the new madrid seismic zone these results suggest that active tectonism and strong seismicity in intraplate north america may not be localized at isolated weak spots but rather widespread on fault systems that are favorably oriented for slip in the contemporary stress field

activity along the osning thrust in central europe during the lateglacial ice sheet and lithosphere interactions abstract the osning thrust is one of the major fault systems in central europe with a length of approximately 115 km it underwent a polyphase tectonic evolution in the mesozoic that ranged from extensional movements in the jurassic to reverse faulting and thrusting during inversion in the late cretaceous a series of complex metre scale faults and related fold structures are developed within the upper pleistocene alluvial aeolian complex of the upper senne 1 km away from the thrust the faults dip towards the north and show offsets in a range of several decimetres growth strata indicate a two fold evolution of the structures the faults began as normal faults and were later transformed into reverse faults which resulted in the formation of small scale inversion structures with a typical harpoon shape glaciotectonics can be ruled out as the driving mechanism for these structures because new optically stimulated luminescence osl ages imply that the sedimentary succession was deposited during the late pleistocene between 29 3 2 9 ka and 13 1 1 5 ka at which time the ice margin was much further to the northeast we believe the inversion structures were caused by movement on the osning thrust due to generation of a forebulge of the late pleistocene weichselian ice sheet this led to normal faulting as a consequence of extension in the forebulge area during glaciation the osl ages for the normal fault related growth strata are in a range of 16 13 ka later reverse movements occurred during deglaciation due to the n s directed compressional stress field in northern germany numerical simulations of the deglaciation seismicity point to seismic events with a thrust mechanism in the study area between 15 5 and 12 3 ka bp although normal faulting is also possible in this time period numerous soft sediment deformation structures imply that movement on the osning thrust caused earthquakes with a significant magnitude in the autumn of 1612 an earthquake took place in this area it is very likely that this event is related to background seismicity on this fault although movement due to the influence of the ongoing glacial rebound in fennoscandia is also possible

quaternary tectonic faulting in the eastern united states abstract paleoseismological study of geologic features thought to result from quaternary tectonic faulting can characterize the frequencies and sizes of large prehistoric and historical earthquakes thereby improving the accuracy and precision of seismic hazard assessments greater accuracy and precision can reduce the likelihood of both underprotection and unnecessary design and construction costs published studies proposed quaternary tectonic faulting at 31 faults folds seismic zones and fields of earthquake induced liquefaction phenomena in the appalachian mountains and coastal plain of the 31 features seven are of known origin four of the seven have nontectonic origins and the other three features are liquefaction fields caused by moderate to large historical and holocene earthquakes in coastal south carolina including charleston the central virginia seismic zone and the newbury massachusetts area however the causal faults of the three liquefaction fields remain unclear charleston has the highest hazard because of large holocene earthquakes in that area but the hazard is highly uncertain because the earthquakes are uncertainly located of the 31 features the remaining 24 are of uncertain origin they require additional work before they can be clearly attributed either to quaternary tectonic faulting or to nontectonic causes of these 24 14 features most of them faults have little or no published geologic evidence of quaternary tectonic faulting that could indicate the likely occurrence of earthquakes larger than those observed historically three more features of the 24 were suggested to have had quaternary tectonic faulting but paleoseismological and other studies of them found no evidence of large prehistoric earthquakes the final seven features of uncertain origin require further examination because all seven are in or near urban areas they are the moodus seismic zone hartford connecticut dobbs ferry fault zone and mosholu fault new york city lancaster seismic zone and the epicenter of the shallow cacoosing valley earthquake lancaster and reading pennsylvania kingston fault central new jersey between new york and philadelphia and everona fault mountain run fault zone washington d c and arlington and alexandria virginia

the search for evidence of large prehistoric earthquakes along the atlantic seaboard the spacial distribution of seismically induced liquefaction features discovered along the atlantic seaboard suggest that during the last 2000 to 5000 years large earthquakes body wave magnitude m b 5 8 0 4 in this region may have been restricted exclusively to south carolina paleoliquefaction evidence for six large prehistoric earthquakes was discovered there at least five of these past events originated in the charleston south carolina area the locale of a magnitude 7 event in 1886 during the past two millennia large events may have occurred about every 500 to 600 years

ground motion and liquefaction simulation of the 1886 charleston south carolina earthquake as part of a comprehensive earthquake loss and vulnerability evaluation of the state of south carolina ground motions were simulated for a moment magnitude m 7 3 1886 charleston like earthquake using finite fault and point source stochastic numerical modeling the probability for liquefaction was also predicted based on factors of safety computed from average cyclic stress and shear wave velocity based cyclic resistance ratios clay content and saturation because there is considerable uncertainty regarding the 1886 source the rupture plane of the 1886 event was modeled as both a 100 km long 20 km wide fault static stress drop of 27 bars and a 50 km long 16 km wide fault 107 bar stress drop the source was assumed to be a north northeast striking strike slip fault coincident with the woodstock fault based on comparing the computed and observed 1886 liquefaction areas and ground motions for both the low and high stress drop events the two cases were weighted 0 8 and 0 2 respectively to accommodate epistemic uncertainty in eastern u s earthquake source processes three region specific point source attenuation models were also developed and used a single corner frequency model with both a constant stress drop and a magnitude dependent stress drop and the double corner frequency model the finite fault and point source models were weighted 0 8 and 0 2 respectively to incorporate site effects into the ground motion estimates an extensive effort was made to characterize the thicknesses shear wave velocities v s and dynamic material properties of unconsolidated sediments characteristic v s profiles were developed using the available subsurface information which incorporated a wide range of soil and rock conditions amplification factors were computed for four site response categories each of which were a function of soil thickness input hard rock motion and spectral frequency from the five weighted stochastic ground motion models two finite fault and three point source and amplification factors rock and soil ground motions were computed to produce statewide ground motion maps for the m 7 3 scenario event weighting of the charleston source and ground motion models was implemented so that the resulting liquefaction areas matched the 1886 areas of liquefaction peak horizontal ground acceleration pga values as high as 0 6 g 0 7 g were estimated in the vicinity of the modeled rupture pgas in the range of 0 3 g 0 4 g were estimated for charleston consistent with the observed building damage and liquefaction significant ground shaking pga 0 2 g extends out to distances of 50 60 km strong long period 1 0 sec ground motions are predicted throughout the state the probabilities for liquefaction were highest in the epicentral region 50 consistent with the observed occurrences of liquefaction in 1886 manuscript received 5 february 2003

liquefaction and flowage at archaeological sites in the inner belt of central japan tectonic and hazard implications abstract all archaeological data gathered at 55 archaeological sites excavated in the alluvial plains and basins of the inner belt of central japan revealed the occurrence and age of events of liquefaction and flowage the alluvial plains and basins are bounded on one or both sides by active faults representing tectonic or block boundary lines the excavated sites with liquefaction and flowage events identified are found distributed within a 15 km wide zone along the tectonic or block boundary lines of the alluvial plains and basins this suggests that seismic hazards caused by liquefaction and flowage mainly occur within this 15 km wide zones along the tectonic lines sand filled dikes of various shapes were found and are thought to represent evidence of liquefaction and flowage the sand filled dikes can be classified into two main types a lenticular type arrangeden echelon and a cylindrical type opening upward in a fan shape archaeological age estimates indicate that the liquefaction and flowage were induced by earthquakes which occurred during three periods around 1000 b c between 0 and 500 a d and after 1500 a d suggesting that active seismic periods occurred at an interval of approximately 1000 years

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

palaeoseismic investigations along the kachchh mainland fault a comprehensive review and new insights of the past earthquakes in the kachchh basin western india abstract the intraplate kachchh rift basin has been hit by several devastating earthquakes in the historic past including the 1819 allah bund earthquake and the 2001 bhuj earthquake the source region of these earthquakes within the basin have been studied by several workers in the last two decades to understand their potential for earthquake recurrence however very little information is available on the palaeoseismic and geomorphic characterization of kachchh mainland fault kmf therefore in the present study six trenches were excavated across the kmf between lakhpat and nirona to understand ground deformation pattern and timing of the historic earthquakes based on geomorphic and palaeoseismic investigations five palaeoearthquakes of early to late holocene have been identified between 10 000 890 yrs apart from the holocene an earthquake of late quaternary period was also identified which possibly occurred around 19 800 yrs bp fault related parameters were analyzed to understand the geometry of the active fault scarp along kmf the results of the analyzed fault geometric parameters show that the vertical displacement along the kmf is higher than the horizontal displacement the slip rate of the kmf from the western portion to the middle portion decreases from 0 08 to 0 04 mm yr and increases towards east from 0 22 mm yr to 0 36 mm yr as the kachchh district of the gujarat state is rapidly developing in terms of infrastructural development the outcome of this research might provide significant inputs for micro zonation studies and also in the evaluation of the seismic hazard in the kachchh region

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

propagation characteristics of sn and lg in northeastern china and mongolia we present propagation characteristics of the short period seismic phases sn and lg in northeastern china and mongolia three component broadband and short period seismograms from the global seismic network station uln and the chinese digital seismic network stations bjt hia and mdj were used in this study the digital waveforms were bandpass filtered 1 0 5 0 hz and were used to rank sn and lg amplitudes relative to the pn and pg phases the short period sn waveforms exhibit great variability efficient sn propagation is observed in southern siberia and along the daxinganling mountains inefficient sn transmission is found near lake baikal and most of northeastern china sn does not propagate across mongolia or the north china plain in northeast china zones of attenuation exist within regions of extension and high heat flow in mongolia severe sn attenuation suggests the presence of a partially melted uppermost mantle the zones of inefficient sn propagation coincide with zones of low pn velocities 7 9 km sec determined by wu et al 1998 in contrast the lg seismic phase has large amplitudes and propagates efficiently for all distances in northeastern china and mongolia

recognition of seismically induced liquefaction features application of fourier grain shape analysis to two sites in the charleston south carolina area abstract sediments collected from two sites in fishburne creek dorchester county near charleston south carolina suspected to have been affected by seismically induced liquefaction were analyzed for shape variation by the fourier grain shape analysis fgsa technique the results indicate that the shape variation of the samples from these sites can be defined by a four end member model the feature at the first site contains a greater proportion of 5 and 6 end members rougher grains and the host has a maxima of 3 and 4 end members smoother grains the cumulative probability values obtained for these end members by fisher s exact test also indicate the presence of extraneous sand in the feature at the first site further confirming the fgsa results no discernible contrast based on shape families can be observed between the feature and the host at the second site indicating possible absence of injected sand the discrimination based on the shape of sand grains by the fgsa technique offers an alternative method to differentiate between liquefaction and nonliquefaction features

mid continental earthquakes spatiotemporal occurrences causes and hazards abstract large earthquakes in north china australia northwestern europe central and eastern united states and other mid continents show complex spatiotemporal patterns that do not fit existing earthquake models individual faults or fault zones tend to fall into long term thousands of years or longer dormancy after a cluster of ruptures whereas large earthquakes seem to roam between widespread faults these behaviors are characteristic of complex dynamic systems of interacting faults in such systems widespread faults collectively accommodate slow tectonic loading and a major fault rupture both transfers stress to the neighboring faults and perturbs loading conditions on distant faults because of the slow tectonic loading local stress variations from fault interaction or nontectonic processes or changes of fault strength could trigger mid continental earthquakes the precise spatiotemporal occurrence of large mid continental earthquakes may be unknowable an intrinsic limitation of complex dynamic systems but their qualitative system behavior may be understood by a system approach this approach would render some commonly used concepts such as seismic cycles recurrence intervals characteristic earthquakes and seismic gaps inadequate or irrelevant in mid continents and calls for rethinking of the probability estimates based on these concepts it requires a better understanding of fault interactions on multiple spatial and temporal scales rather than focusing solely on the balance of tectonic loading and yield strength of individual faults or fault segments it also indicates the need for paleoseismic and geodetic studies extending beyond areas where recent large earthquakes occurred and for hazard assessments to reduce the biasing influence of the most recent large earthquakes that tend to dominate the short and incomplete earthquake records

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

thermal tectonic evolution of the yellow sea and east china sea implication for transformation of continental to oceanic crust and marginal basin formation abstract the yellow sea was developed in a craton environment into basins of deposition by rifting followed by intrusions of heated materials in a phase of basification of the continental crust the east china sea was developed by the same processes on a mobile zone with extensive subsidence into a basin bordered by a parageosynclinal zone in which back arc spreading was in operation the evolution of these two seas is recognized to be the result of transformation of continental to oceanic crust in which tensional activities in the form of rifting in the initial stage created open space to be filled with heated materials in the form of hot spot volcanism these two phases of operation create density instabilities and anomalous mantle structure that induce extensive subsidence accompanied by formation of oceanic type crust in the basins the transformation of continental to oceanic crust in the case of the yellow sea and the east china sea can be visualised as progressing though three stages 1 1 the yellow sea is in a state of greater tensional activities but less volcanism 2 2 the east china sea is in a more advanced stage of greater volcanism and subsidence 3 3 the okiniwa trough is created by back arc spreading as a typical marginal basin these three basins separated by their submarine ridges manifest a stress pattern characteristic of a basin range structure in a time scenario for the tertiary evolution of asian continental margin

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

paleoseismic features as indicators of earthquake hazards in north coastal san diego county california usa abstract new road cut and mass grading excavations in the north coastal area of san diego county california expose heretofore generally unrecognized probable late holocene tsunami deposits and paleoseismically deformed sediments remnant tsunami deposits occur up to 100 m in elevation around the margins of modern coastal lagoons and estuaries and combined with local mima mounds of possible sand blow origin provide indirect but compelling evidence for the late quaternary activity of onshore and offshore faults in the immediate study area probable paleoliquefaction features are regionally widespread and range from fissures filled with sediments derived from overlying marine terrace sand and soil to the more traditional sand filled injection dikes and sills lateral spreads and filled craterlets the source of most liquefied sediment is underlying tertiary bedrock sand and local quaternary marine terrace deposits a paleoseismic liquefaction origin rather than soft sediment loading is deduced for these features based on morphology internal stratigraphy field setting and near proximity to known seismogenic sources some paleoseismic events impacted late holocene indian middens and burial sites the last seismic event probably occurred within the past 1 to 3 ka and possibly even records the historic earthquakes of either november 22 1800 or may 27 1862 the liquefaction features also affect marine terrace sediments tens of meters above modern regional water levels inferentially recording paleoseismic events in this mediterranean type climatic region during winter rains when high level perched water saturates the several meter thick source sediments based on their regional extent the paleoseismic features were likely caused by m 7 tectonic events inferentially generated by the nearby offshore newport inglewood rose canyon fault system or possibly by smaller recently exposed related and localized faults accordingly the seismic hazard of the north coastal area of san diego county may be substantially higher than previously assumed and hence of concern owing to the rapid ongoing and projected population increase

high frequency seismic observations in eastern kazakhstan ussr with emphasis on chemical explosion experiments two temporary three station seismic networks deploying surface and 100 m borehole high frequency seismometers of the order of 200 km from the kazakh test site in the ussr and the nevada test site in the united states are discussed with emphasis on chemical explosion experiments seismograms attained from the detonation of three buried explosions 10 t 20 t 10 t in eastern kazakhstan at distances between 156 and 637 km are examined in the frequency band of 1 80 hz observed signal to noise s n ratios were high reaching a maximum of 400 for pg waves and 200 for lg waves good signal to noise levels persisted to high frequencies s n 2 at about 50 hz for lg waves about 250 km from the source and at about 14 hz at 680 km distance for pg waves s n 2 at about 50 hz 270 km from the source shapes of displacement amplitude spectra were similar characterized by a broad maximum in signal to noise levels between 4 8 hz and a decay at higher frequencies e g above 10 hz of about f 3 5 f 4 1 for lg waves and f 3 1 f 4 5 for pg unconnected for distance magnitudes estimated from lg time domain amplitudes for the 10 t explosion are between 2 8 and 3 3 depending on the magnitude relation used spectral characteristics are used to put some constraint on lg q pg q is poorly constrained by the data a similar experiment in southern nevada showed much lower pg and lg signal to noise levels above 1 hz although kazakh and nevada absolute noise levels are comparable

an inversion of lg wave attenuation and site response from seismic spectral ratios in the eastern china region abstract both lg wave attenuation and site responses are determined in the eastern china region the region ranges from 26 n to 33 n and 117 e to 124 e we analyze over 1360 three component seismograms from 92 local and regional earthquakes the seismograms are recorded in the distance range of 100 600 km the earthquakes occurred between 2002 and 2012 in the region and varied in magnitude between 2 0 and 4 7 m l a combined inversion method which can simultaneously estimate attenuation and site response from seismic spectral ratios is implemented in the study modeling errors are determined using a delete j jackknife resampling technique fourier spectral amplitudes are measured from lg phases windowed between the group velocity limits 2 6 and 3 6 km s the inversion are performed in a frequency range of 1 6 hz with an interval of 0 2 hz the frequency dependent quality factor is modeled in the form of q q 0 f the eastern china region displays high q 0 and a weaker frequency dependence characterized by the functions q 335 16 f 0 45 0 02 q 411 21 f 0 26 0 01 and q 432 26 f 0 24 0 01 for vertical north south and east west components respectively the values are similar to the average for other stable regions of the globe site responses from 32 stations are estimated in the region most stations do not show obvious amplification the site responses are mainly smooth flat and less than 5 in the frequency range of 1 6 hz

shallow marine massive sandstone sheets as indicators of palaeoseismic liquefaction an example from the ordovician shelf of central bolivia abstract the middle to upper ordovician siliciclastic succession in central bolivia provides excellent exposures of up to 1 m thick massive sandstone beds produced by liquefaction induced sediment remobilisation these fine grained massive sandstones occur in shallow marine nearshore facies that were deposited above storm wave base vertical to steeply inclined clastic dykes which penetrate up to 1 5 m of the overlying sediment pile feed into the basal parts of massive sandstone sheets these dykes are interpreted as pathways used by liquefied sediment during upward directed escape from a subsurface horizon the relatively short lateral spacing of 5 to 25 m between the individual dykes initiated lateral coalescence of ejected individual sediment bodies as a result massive sandstone sheets formed and can be traced laterally over several kilometres while undeformed sandy deposits contain between 5 to 10 dispersed clay the average clay content in massive sandstone sheets is 15 the elongated sometimes s shaped form of the sandy laminated fragments reflects squeezing during movement showing that they have been deformed under shear stress during flow the axis of maximum elongation of the fragments indicates local flow direction as the massive sandstone sheets are likely the products of seismic shocks they provide the first evidence of tectonic activity in this part of the basin during the middle to late ordovician

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

controls on space time distribution of soft sediment deformation structures applying palaeomagnetic dating to approach the apparent recurrence period of paleoseisms at the concud fault eastern spain abstract this work describes soft sediment deformation structures clastic dykes load structures diapirs slumps nodulizations or mudcracks identified in three sections concud ramblillas and masada cociero in the iberian range spain these sections were logged from boreholes and outcrops in upper pliocene lower pleistocene deposits of the teruel concud residual basin close to de concud normal fault timing of the succession and hence of seismic and non seismic ssdss covering a time span between 3 6 and 1 9 ma has been constrained from previous biostratigraphic and magnetostratigraphic information then substantially refined from a new magnetostratigraphic study at masada cociero profile non seismic ssdss are relatively well correlated between sections while seismic ones are poorly correlated except for several clusters of structures between 29 and 35 seismic deformed levels have been computed for the overall stratigraphic succession factors controlling the lateral and vertical distribution of ssdss are their seismic or non seismic origin the distance to the seismogenic source concud fault the sedimentary facies involved in deformation and the observation conditions borehole core vs natural outcrop in the overall stratigraphic section seismites show an apparent recurrence period of 56 to 108 ka clustering of seismic ssdss levels within a 91 ka long interval records a period of high paleoseismic activity with an apparent recurrence time of 4 8 to 6 1 ka associated with increasing sedimentation rate and fault activity such activity pattern of the concud fault for the late pliocene early pliocene with alternating periods of faster and slower slip is similar to that for the most recent quaternary last ca 74 ka bp concerning the research methods time occurrence patterns recognized for peaks of paleoseismic activity from ssdss in boreholes are similar to those inferred from primary evidence in trenches consequently apparent recurrence periods calculated from ssds inventories collected in borehole logs close to seismogenic faults are comparable to actual recurrence times of large paleoearthquakes

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

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

tectonic elements with south china affinity in the korean peninsula new early jurassic palaeomagnetic data summary early jurassic sandstones and shales were collected at 14 sites from the kimpo area in the western part of the korean peninsula for a palaeomagnetic study a characteristic remanent magnetization component which passes the fold test was isolated from seven sites this characteristic component is interpreted to be of primary early jurassic origin because the folding age is middle late jurassic the primary directions together with previously reported ones provide a mean direction d 38 1 i 39 7 95 3 8 11 sites and a palaeomagnetic pole 54 1 n 230 2 e a95 4 1 for the kimpo area this palaeomagnetic pole shows good agreement with the coeval poles for the south china block and is significantly removed from that for the north china block suggesting that the kimpo area has been part of the south china block since at least early jurassic times the kimpo area constitutes a part of the imjingang belt which is palaeontologically allocated to the south china block in its origin while all precambrian tectonic blocks that compose the basement of the korean peninsula are interpreted to be of north china origin we conclude that the imjingang belt including the kimpo area is a tectonic extension of the south china block on the korean peninsula the south china elements were obducted onto the north china block at the site of the present korean peninsula during the collision event of the north and south china blocks and hence the korean peninsula is composed of areas with both north and south china affinities

the helena banks strike slip fault zone in the charleston south carolina earthquake area results from a marine high resolution multichannel seismic reflection survey in 1981 the u s geological survey conducted a high resolution 12 channel seismic reflection survey offshore of charleston south carolina to study young faults that may be earthquake sources we collected data along 24 profiles totaling about 600 km with shotpoints at 10 m intervals the helena banks fault zone hbfz was crossed by 13 high resolution profiles which combined with 5 conventional 64 channel profiles acquired in 1979 across the fault zone provide greater definition of this structure than any similar feature along the atlantic seaboard or continental margin the hbfz trends n66 e and is about 110 km long the same trend as the underlying kiawah triassic basin it comprises several segments 10 40 km long that trend between n68 e and n77 e with a mean of n72 e the left stepping echelon pattern of the segments connected by normal faults observed on two profiles in the hbfz suggests slip could possibly be left lateral despite high angle reverse separation mean fault dip 70 5 of coastal plain strata seen on the individual reflection profiles aeromagnetic data constrain the maximum ratio of horizontal to vertical slip from about 10 1 to 100 1 our interpretation is consistent with the present day northeast trending maximum horizontal compressional stress field however the reflection data cannot independently prove that the main sense of motion on the hbfz is strike slip examination of vertical separations on six segments across the hbf indicates a linear increase with depth of 51 12 m km which is similar to 36 m km and 48 m km reported previously as measured on multichannel seismic reflection profiles crossing the gants and cooke faults respectively on land in the meizoseismal area of the 1886 earthquake we interpret these results to indicate that as a first approximation the stress field did not vary significantly in direction or magnitude from late cretaceous time to pleistocene time and likely to the present in the charleston region the trend of the hbfz as mapped by the reflection profiles follows the narrow kiawah triassic basin which was delineated by the second vertical derivative of total magnetic intensity several reflection profiles indicate that the hbfz is a compressional reactivation of an extensional triassic fault zone bounding the basin

the 1886 charleston south carolina earthquake and the appalachian detachment several lines of evidence from new and existing data are consistent with an extended fault slip associated with the 1886 earthquake in south carolina back slip over a portion of the appalachian detachment approximately corresponding to the coastal plain of south carolina fits some of the data including coseismic and post seismic strain indicators a small seismic source for the august 31 1886 main shock cannot be ruled out and a large but only partially seismic fault slip is possible during this event intensities of mm viii occurred over a wide area of the coastal plain and are not limited to the charleston summerville area where the traditional small source for this earthquake is located near source effects such as ground fissuring liquefaction changes in line of sight foreshocks and aftershocks occurred over a wide area of the coastal plain and neighboring inner piedmont which we tentatively refer to as the meizoseismal area this area is sharply bounded by the savannah river toward the southwest and approximately by the north carolina south carolina state border toward the northeast these boundaries are not associated with any known structure transverse to the strike of the appalachians during the 14 years prior to 1886 seismicity was concentrated around the extended meizoseismal area while the seismicity within that area was unusually low suggesting a premonitory doughnutlike pattern the intensity distribution in the far and near field of the 1886 event and of the great indian detachment earthquakes e g the 1905 m 8 and the 1934 m 8 3 events are qualitatively and quantitatively similar this is consistent with comparable source dimensions since well known intermediate magnitude earthquakes in india and in eastern north america exhibit similar intensity patterns and indicate similar seismic attenuation in the two cratonic environments several meters of coseismic 1886 northwest compressive strain near summerville are indicated by buckling of rails a large postseismic normal displacement is suggested by releveling data 1935 1968 across the brevard fault zone updip northwest of the presumed 1886 detachment slip these strains are consistent with a southeastward slip of the detached crystalline sheet associated with the 1886 earthquake available data indicate that in the southern appalachians the updip transition from maximum horizontal to least horizontal compressive stress in the dip direction perpendicular to structural trends occurs somewhere in the piedmont and may coincide with the steepest portion of the detachment the stress field may also contain a time dependent component in the sediments of the coastal plain orthogonal sets of subvertical clastic dikes oriented along and across the appalachian strike direction suggest one or more interchange of the principal stress axes we infer from coseismic dry fissuring and liquefaction that clastic dikes filled from above and from below were also generated during the 1886 event prehistoric clastic dikes along with other structures in the sediments may have been generated during prehistoric earthquakes similar to the 1886 event stress reversals corresponding to earthquake cycles may characterize the stress field within detached sheets or wedges that move primarily by great detachment earthquake ruptures appendices are available with entire article on microfiche order from american geophysical union 2000 florida avenue n w washington d c 20009 document j81 008 1 00 payment must accompany order

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

high resolution mantle tomography of china and surrounding regions 1 a high resolution p wave tomographic model of the crust and mantle down to 1100 km depth under china and surrounding regions is determined by using about one million arrival times of p pp pp and pcp waves from 19 361 earthquakes recorded by 1012 seismic stations the subducting pacific slab is imaged clearly as a high velocity zone from the oceanic trenches down to about 600 km depth and intermediate depth and deep earthquakes are located within the slab the pacific slab becomes stagnant in the mantle transition zone under east china the western edge of the stagnant slab is roughly coincident with a surface topographic boundary in east china the active changbai and wudalianchi intraplate volcanoes in northeast china are underlain by significant slow anomalies in the upper mantle above the stagnant pacific slab these results suggest that the active intraplate volcanoes in ne china are not hot spots but a kind of back arc volcano associated with the deep subduction of the pacific slab and its stagnancy in the transition zone under the mariana arc however the pacific slab penetrates directly down to the lower mantle the active tengchong volcano in southwest china is related to the eastward subduction of the burma microplate the subducting indian and philippine sea plates are also imaged clearly the indian plate has subducted down to 200 300 km depth under the tibetan plateau with a horizontal moving distance of about 500 km high velocity anomalies are revealed in the upper mantle under the tarim basin ordos and sichuan basin which are three stable blocks in china

acoustic facies of holocene megaturbidites in the eastern mediterranean abstract the acoustic facies of holocene megaturbidites in the central western abyssal plains of the eastern mediterranean sea is analysed combining core lithology and synthetic seismograms produced on the basis of p wave velocity profiles derived by multi sensor core logging from a core in the western herodotous trough the acoustic facies of the megaturbidite is divided in two layers 1 an upper transparent low velocity layer corresponding to structureless mud 2 a lower highly reflective high velocity layer corresponding to the graded sandy base correlation with sub bottom profiler data allowed us to estimate in about 21 23 m the maximum total thickness of the two layer megaturbidite in the ionian abyssal plain these results demonstrate that thicknesses traditionally computed on the basis of the acoustically transparent layer alone may produce a relevant underestimation of the total volume of the deposit the total volume of the megaturbidite extending over the ionian and sirte abyssal plains including the western herodotous trough is therefore estimated in about 162 10 km 3

intraplate seismicity and stress in the southeastern united states abstract the stress induced by topography and by density heterogeneities in the lithosphere has been computed for two seismic regions in the southeastern united states the southern appalachian mountains and the south carolina coastal plain the lithosphere was assumed to be a three dimensional layered elastic slab overlying an inviscid fluid the calculations indicate that the local stress is of the same magnitude as the tectonic stress tens of mpa but contradictory conclusions are suggested by the comparison of stress differences and principal directions with earthquake locations and focal mechanisms in the southern appalachians the seismicity correlates well with the stress maximum and focal mechanisms agree with the calculations where regional stress is combined with locally induced stress in south carolina a combination of regional and local stress can explain the orientation of focal mechanisms but stress does not concentrate in the region of charleston and thus other factors must play a role in the charleston seismicity

holocene earthquakes inferred from a fan delta sequence in the dead sea graben abstract the holocene sequence of the fan delta of nahal darga in israel records deformation associated with earthquakes related to the dead sea transform in general and to the jericho fault in particular the fan delta sequence is well exposed and 20 radiocarbon ages help to date the earthquakes that are inferred from a displacement along faults b liquefaction features associated with 11 separate sandy and silty layers and c slumped allocthonous bodies of sediments located directly above one of the main splays of the jericho fault on average an earthquake larger than m 5 5 has occurred approximately every 600 years this estimate is based on the earthquake record of the complete stratigraphic sequence with erosional hiatuses omitted from the calculations the most recently deformed layer is related to the 1927 jericho m l 6 2 earthquake this layer provides a modern analog for the style of soft sediment deformation associated with earthquakes in the late pleistocene and holocene silty sand beds of the fan delta complexes of the dead sea and its predecessor lake lisan

on the attenuation of lg waves in western and central asia and their use as a discriminant between earthquakes and explosions data from earthquakes and explosions in the western and central parts of the soviet union are used to determine the values of the coefficient of anelastic attenuation of 1 sec period lg waves from the russian uplands region and for the region from the caspian sea to the southern perimeter of the soviet union for the former region the value is approximately 0 15 deg 1 and for the latter 0 35 deg 1 using the empirical veith and clawson 1972 curve for the amplitude of p waves at regional distances and theoretical curves for the attenuation of higher mode surface waves for lg curves are constructed which show the variation of the amplitude ratio of lg to p with epicentral distance with the coefficient of anelastic attenuation as a parameter when data from explosions and earthquakes in the soviet union are compared with the calculated curves the amplitude ratios of lg and p on the average are larger for earthquakes than explosions however there is much overlap so that this ratio by itself does not appear to be a useful discriminant between earthquakes and explosions

geologic evidence for recurrent moderate to large earthquakes near charleston south carolina multiple generations of earthquake induced sand blows in quaternary sediments and soils near charleston south carolina are evidence of recurrent moderate to large earthquakes in that area the large 1886 earthquake the only historic earthquake known to have produced sand blows at charleston probably caused the youngest observed blows older late quaternary sand blows in the charleston area indicate at least two prehistoric earthquakes with shaking severities comparable to the 1886 event

crustal in south korea using the source pair receiver pair method graphic 1 has been studied extensively because its regional variations reflect geological structure values around 1 hz show close correlation with tectonic seismicity we analyze graphic 2 in south korea by applying the source pair receiver pair sprp method to 39 korean earthquakes and 32 far regional earthquakes we obtain nearly 1500 source receiver pairs with the combined difference of epicentral distance d ranging from 16 to 657 km seismograms are filtered by using an eight pole bandpass butterworth filter with five center frequencies 0 375 0 75 1 5 3 and 6 hz the obtained graphic 3 for all frequencies are less than 0 002 which is a reasonable value for a seismically inactive region in spite of the short range of d the results of the sprp method show reliable values especially at 1 5 and 3 hz 1 embed inline graphic 2 gif 2 embed inline graphic 3 gif 3 embed inline graphic 4 gif

characteristics of deformation and past seismicity associated with the 1819 kutch earthquake northwestern india the 1819 earthquake in kutch northwestern india is one of the most significant events to have occurred in a plate interior setting despite being the second largest among the stable continental region scr earthquakes this event has not been analyzed within the context of present day understanding of earthquake seismology coseismic changes related to this earthquake include massive ground deformation in a wide low lying tidal flat area although detailed historic accounts of this earthquake exist many questions regarding the mode of deformation and the seismic history of the region remain unresolved we explored the region nearly 180 years after the earthquake and the information gathered adds to our understanding of this event and provides a fresh perspective on this unique intraplate seismogenic zone a 90 km long tract of elevated land with a peak height of 4 3 m is the most visible surface expression of this earthquake we surveyed and analyzed the morphological features of this scarp and also carried out exploratory trenching in this region the scarp morphology is suggestive of a growing fold related to a buried north dipping thrust rather than a discrete fault that could have resulted from a surface rupture the extensive liquefaction field associated with the earthquake offered an ideal setting to explore the paleoearthquake history age data of liquefaction features suggest that a previous event of comparable size must have occurred 800 1000 years ago seismic activity appears to be related to the reactivation of an ancient rift in a stress regime that is dominated by nearly north south compression

seismogenic deformation structures in microbialites and mudstones silurian lockport dolomite northwestern ohio u s a syndepositional deformation structures are present at two different stratigraphic levels in the silurian lockport dolomite at a quarry in maumee ohio such structures are absent in this unit at twelve other quarries in northwestern ohio the structures at maumee present within stromatolites thrombolites and variably bedded mudstones include convolute layers homogenization of bedding and breccia clasts clasts of stromatolites boudinage structures normal reverse and thrust faults and discordant and concordant breccias the distribution of deformation structures within beds suggests substantial control from substrate rheology possibly resulting from differences in degrees of lithification and from variations in water content the extensive variety of syndepositional deformation structures juxtaposed evidence for nearly synchronous compression and dilation proximity 4 5 km of the structures to the largest fault in northwestern ohio the bowling green fault and the restricted geographic distribution of the deformation structures suggest seismic shaking as a probable mode of genesis similarities between features produced by seismogenic deformation of siliciclastic sediments and deformation features in the lockport dolomite provide additional evidence that the latter features are seismogenic it is postulated that two earthquakes one with a magnitude 5 caused the formation of the syndepositional deformation structures present in the youngest facies in the lockport dolomite at maumee quarry the bowling green fault 4 5 km west of maumee was a growth fault during formation of the lockport dolomite and is considered to have been the source of earthquakes that created the syndepositonal deformation structures in this unit at maumee quarry evidence from the lockport dolomite in northwestern ohio suggests that seismogenic deformation structures created by two earthquakes along the bowling green fault with magnitudes of 5 did not form in this unit over large areas i e all of northwestern ohio this evidence challenges the suggestion that syndepositional seismogenic deformation structures are always formed over a large area

holocene tectonic activity along kachchh mainland fault impact on late mature harappan civilization kachchh western india abstract paleoseismic and archaeological records of the kachchh rift basin krb of western india indicates that the region become tectonically active during the period of middle to late holocene to understand the relationship between strain accumulation earthquake genesis and landform development we analyzed uplifted late quaternary terraces and archaeological evidence along the kachchh mainland fault kmf zone dividing the elevation of the bedrock strath at each site by their ages yields vertical uplift rates of 0 29 1 17 mm y for the kmf zones archaeological data from the excavation of the kotada bhadli site suggest that the site was occupied during the late mature harappan 2300 2500 bce period and abandoned around 1900 bce the ruins of harappan civilization at kotada bhadli location are resting over the middle holocene fluvial sediments the oldest fluvial sediment is dated to 4 ka whereas the youngest sediment yielded an age of 3 ka the chronological constraints in geomorphic and archaeological records suggest that the area was hit by an earthquake around 2200 bc 3 5ka the geomorphic and chronologically constrained uplift rates reveal that the kmf zone of the intraplate region of the kachchh is geodynamically controlled by several fault segments which are consistent with the ambient tectonic stress field owing to the northward movement of the indian plate concerning the eurasian plate

crustal structure volcanism and opening mode of the ulleung basin east sea sea of japan abstract a study of the ulleung basin in the southwestern east sea sea of japan based on single and multi channel seismic reflection profiles and ocean bottom seismometer obs data suggests that the basin formed largely by pull apart opening and the deep northern basin is underlain by thicker than normal oceanic crust 10 km thick probably formed during the earliest stage of seafloor spreading volcanic activity in association with basin opening occurred over much of the basin but it ceased first in the south while it continued in the north until recently the principal evidence for pull apart opening includes 1 an overall rhomboidal shape of the basin consisting of two basement lows and a median high known to be characteristic of pull apart basins 2 the location and orientation of the major volcanic sources suggesting more or less n s opening and 3 the strike slip fault system along the western basin margin which appears to have guided the pull apart opening the lack of extensional deformation along the western basin margin which would have been prevalent if sw japan had rotated away from the korean peninsula as suggested by paleomagnetic data is also not in favor of the alternative rotational opening of the basin the absence of graben and rift topography in the acoustic basement in the deep northern ulleung basin is indicative of the non brittle or ductile nature of the crust tau p analysis of the obs data reveals that the igneous crust consists of upper and lower layers with velocities typical of oceanic layers the velocity depth profiles with a two gradient velocity structure is also characteristic of oceanic crust however the lower layer is much thicker than oceanic layer 3 and the change of velocity gradient which occurs at around 6 5 km s in typical oceanic crust occurs at about 6 km s suggesting that the crust is not a typical oceanic crust the meager basin size and short opening period may suggest that the basin opening did not lead to the formation of full fledged oceanic crust but instead resulted in embryonic or incipient oceanic crust thickened by upper mantle thermal perturbations evoked by rifting

soft sediment deformation structures interpreted as seismites in middle late pleistocene aeolian deposits apulian foreland southern italy abstract soft sediment deformation structures in middle late pleistocene deposits of torre san gennaro brindisi southern italy have been analysed from a morphologic point of view the deformational structures are represented by deformed cross bedding and large injection structures they are restricted to aeolian sediments and the mechanism of deformation is related to liquefaction and or fluidization processes the liquefaction and or fluidization processes have been interpreted as seismic induced after consideration of all other possible trigger agents the discussion about the possible source areas of the palaeoseismic event was carried out through the analysis both of the general magnitude distance relations and the main structural features of the study zone in conclusion we consider the key criteria for trigger mechanism interpretation of soft sediment deformation structures in aeolian deposits and the actual feasibility of using aeolian sediments for the palaeoseismic studies

liquefaction features on the fraser delta evidence for prehistoric earthquakes sand dykes and sills and vented sand boils on the fraser river delta and adjacent serpentine river floodplain in southwestern british columbia record one or more major liquefaction events the source of the dykes is a shallow subsurface saturated sand unit that was deposited in foreslope and distributary channel environments during holocene progradation of the fraser delta the dykes cut steeply through a crust of delta topset muds and locally flatten out as sills in overlying peaty sediments at two sites evidence was found for venting of sand onto a subaerial or intertidal surface liquefaction and upward movement of sand and water locally deformed the intruded sediments causing some subsidence and uplift of the delta surface all observed liquefaction features are younger than ca 3500 bp and at least some are younger than 2400 bp it is not clear however whether they formed during one or several separate events a review of possible causes suggests that the liquefaction features probably are seis

predicted detection rates of regional scale meteorite impacts on mars with the insight short period seismometer abstract in 2016 nasa will launch the insight discovery class mission which aims to study the detailed internal structure of mars for the first time short and long period seismometers form a major component of insight s payload and have the potential to detect seismic waves generated by meteorite impacts large globally detectable impact events producing craters with diameters of 100 m have been investigated previously and are likely to be rare teanby n a wookey j 2011 phys earth planet int 186 70 80 but smaller impacts producing craters in the 0 5 20 m range are more numerous and potentially occur sufficiently often to be detectable on regional scales 1000 km at these distances seismic waves will have significant high frequency content and will be suited to detection with insight s short period seismometer seis sp in this paper i estimate the current martian crater production function from observations of new craters malin m c et al 2006 science 314 1573 1577 daubar i j et al 2013 icarus 225 506 516 model results williams j p pathare a v aharonson o 2014 icarus 235 23 36 and standard isochrons hartmann w k 2005 icarus 174 294 320 these impact rates are combined with an empirical relation between impact energy source receiver distance and peak seismogram amplitude derived from a compilation of seismic recordings of terrestrial and lunar impacts chemical explosions and nuclear tests the resulting peak seismogram amplitude scaling law contains significant uncertainty but can be used to predict impact detection rates i estimate that for a short period instrument with a noise spectral density of 10 8 ms 2 hz 1 2 in the 1 16 hz frequency band approximately 0 1 30 regional impacts per year should be detectable with a nominal value of 1 3 impacts per year therefore small regional impacts are likely to be a viable source of seismic energy for probing mars crustal and upper mantle structure this is particularly appealing as such impacts should be easily located with orbital imagery increasing their scientific value compared to other types of events with unknown origins finally comparison of the empirical results presented here with the modelling study of teanby and wookey teanby n a wookey j 2011 phys earth planet int 186 70 80 provides constraints on the seismic efficiency suggesting that values of 5 10 4 may be appropriate for impact generated seismic waves comparing explosion and impact datasets indicate that buried explosions are 10 times more efficient at generating seismic waves than impacts

attenuation of 1 6 s lg waves in eurasia we report our investigation of the lg attenuation characteristics in eurasia using digital recordings from the incorporated research institutions for seismology chinese digital seismic network broadband stations to maximize the utilization of the current station and source distribution in the region we have derived a new technique known as the source pair receiver pair sprp method for lg attenuation measurement the procedure eliminates seismic source and site effects leaving behind decontaminated amplitude data from which regional wave attenuation is estimated for lg attenuation studies the sprp method is more flexible and of greater general applicability than its predecessor the reversed two station method chun et al 1987 the application of the sprp method to our time domain analysis of 33 regional and far regional seismic events has provided stable regional average for lg attenuation in periods of 1 6 s our time domain analysis aided by a damped least squares inversion algorithm has led to robust measurements of lg attenuation q and its frequency dependence in nine subregions of tectonic significance regions of active tectonics and seismicity generally have lower q0 than that in the stable continental interior subregional q and are found compatible with the published results in areas of relatively uniform geology values are comparatively poorly determined suggesting that they are susceptible to the presence of crustal heterogeneities along the wave paths

opening mode of the japan sea inferred from the palaeomagnetism of the japan arc the western edge of the pacific plate is marked by a chain of back arc basins stretching from the aleutians through japan and the philippines to new zealand most of the basins lie behind volcanic island arcs far from continents and are the result of extension of the oceanic lithosphere1 but the japan sea is bounded on one side by continental crust the sikhote alin and korean peninsula of the asian continent and on the other by an active arc with continental fragments it can thus be said to be associated more with continental rifting1 4 than with oceanic processes we report here palaeomagnetic data from the japan arc which indicate that since the early miocene north east japan has rotated counter clockwise through 47 around a vertical axis while south west japan has rotated clockwise through 56 refs 5 8 we attribute this differential rotation which took place concurrently between 21 and 11 myr ago to the back arc opening of the japan sea8 with a double door mode that is there are two fan shaped spreading basins facing each other such a fan shaped opening is probably peculiar to the geological phenomenon of rifting of a continental fragment from thick continental lithosphere

repeated large subduction zone earthquakes in the nankai suruga trough evidence from submarine liquefactions 1 subduction zones are generally characterized by large earthquakes that contribute about 90 of the total seismic moment worldwide and can cause great damage from tsunamis such as the 2004 sumatra mw 9 0 earthquake here we report recurrent large subduction zone earthquakes revealed by extensive submarine liquefactions formed in the nankai suruga trough where the philippine sea plate is subducting beneath the eurasian plate field evidence and grain size analysis of liquefied deposits show that the multiple liquefactions were repeatedly induced by strong earthquake shaking during the pleistocene in the eastern nankai suruga subduction zone the recognition and analysis of submarine liquefactions provide reliable paleoseismic evidence in the nankai suruga subduction zone

soft sediment deformation structures in nw germany caused by late pleistocene seismicity new data on seismically triggered soft sediment deformation structures in pleniglacial to late glacial alluvial fan and aeolian sand sheet deposits of the upper senne area link this soft sediment deformation directly to earthquakes generated along the osning thrust which is one of the major fault systems in central europe soft sediment deformation structures include a complex fault and fold pattern clastic dikes sand volcanoes sills irregular intrusive sedimentary bodies flame structures and ball and pillow structures the style of soft sediment deformation will be discussed with respect to brittle failure liquefaction and fluidization processes and was controlled by 1 the magnitude of the earthquake and 2 the permeability tensile strength and flexural resistance of the alluvial and aeolian sediments it is the first time in northern germany that fluidization and liquefaction features can be directly related to a fault the occurrence of seismicity in the late pleistocene and in the seventeenth century indicates ongoing crustal movements along the osning thrust and sheds new light on the seismic activity of northern germany the late pleistocene earthquake probably occurred between 15 9 1 6 and 13 1 1 5 ka the association of soft sediment deformation structures implies that it had a magnitude of at least 5 5

the relationship between late cenozoic tectonic events and stress field and basin development in northeast japan the regional tectonic stress field basin development and crustal deformation of the ne japan arc in the interval between 32 ma to the quaternary can be synthesized based on dike vein and fault orientation data as well as on the compilation of the regional geology an extensional stress field became prevalent from 32 ma and major normal faulting started at 25 20 ma which resulted from back arc rifting normal faulting trending nearly parallel to the arc propagated from the present japan sea coast to the forearc side following the trenchward migration of the main volcanic field from 20 to 15 ma normal faults with an oblique trend to the arc developed due to the counterclockwise rotation of ne japan the rapid clockwise rotation of sw japan since 16 ma produced a nw se directed transtensional stress regime in the ne japan arc due to crustal stretching associated with this pull apart movement the back arc side of the ne japan arc subsided rapidly to middle bathyal environments after the termination of the opening of the japan sea at about 14 ma a neutral stress regime prevailed which included phases of both weak extension and compression lithospheric cooling eventually led to thermal subsidence of the back arc region and igneous underplating caused uplift of the axial zone of the volcanic arc the increase in velocity of the westward motion of the pacific plate at around 4 ma produced strong compression across the arc reactivating most of the miocene normal faults and uplifting the volcanic arc the greatest crustal shortening occurred in areas that were stretched the most in the miocene within the volcanic arc which implies tectonic inversion

seismites an attempt at critical analysis and classification abstract the main types of seismites are reviewed following the proposed classification and are illustrated by our own case studies the large variety of seismites depends on the sedimentologic hydrodynamic and diagenetic characters of the deposits subject to seismic shocks on a given site generally different types of seismites cane be related to the same seismic event these peculiar but widespread sedimentary structures are not always univocal and may often be related to different causes therefore the structures discussed must necessarily be placed in a detailed geological context

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

dynamics of magma emplacement in centrifuge models of continental extension with implications for flank volcanism a set of experimental small scale models of continental extension investigated the emplacement of orthogonal and oblique magma chambers initially underplated at the base of the crust the models are driven by a centrifugal body force which simulates the role of gravity in nature the models represent crustal conditions analogous to relatively mature continental rifts and consider both symmetric and asymmetric extension the experimental results suggest that magma emplacement is controlled by the interactions between tectonics and rheology of the crustal layers in particular extension is mainly accommodated by lateral flow and ductile doming in the viscous layer simulating the lower crust and by listric normal faults in the overlying brittle layer associated with the ductile domal uplift stretching of the continental crust induces a reactive migration of viscous layers into the footwall of major normal faults where magma accumulation at the core of the domes takes place this behavior suggests that widespread magmatism is expected to localize in the footwall of major normal faults a situation that is often observed in core complex structures although the models presented here are intended to simulate magma emplacement during extension of a two layer brittle ductile system lateral flow and migration of magma initially underplated at the base of the crust beneath narrow rifts e g the ethiopian rift may also provide a similar mechanism and a possible explanation for the occurrence of important volcanoes on the plateaus flanking the rift zones in the suggested model such volcanoes are related to large basaltic magma reservoirs located at the base of the crust to accommodate the space vacated by lateral flow and thinning of the ductile crust the similarity in structure of the models with natural examples of continental extension modes such as rift systems and core complexes may suggest a close similarity of dynamic processes

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

earthquakes in the eastern great lakes basin from a regional perspective abstract this paper presents a summary of the seismicity and its relation to stress and geologic structures in the eastern great lakes basin eglb and compares it with that of other regions in the central and eastern north america cena the earthquakes scattered throughout the eglb are occurring at a rate somewhat less than that of the appalachians and along the atlantic seaboard paleoseismology studies suggest that the lower seismicity rate may be characteristic of the eglb since the late wisconsin north of the eglb earthquakes have primarily thrust mechanisms while to the south of the eglb most earthquakes are strike slip throughout the region including the eglb the average p axes of the earthquakes are oriented ne sw and are aligned with the direction of the current plate driving stress on a regional basis earthquakes are centered primarily in the precambrian basement beneath the paleozoic cover many of the earthquakes in the eglb have occurred in areas of preexisting faults at least some of which may have been active during past episodes of continental rifting for individual faults that have been studied in some detail however it is not clear whether earthquakes represent reactivations of local preexisting structures or nucleation of new ruptures in or near the old fault zones

geochronologic evidence for a possible mis 11 emergent barrier beach ridge in southeastern georgia usa abstract predominantly clastic off lapping transgressive near shore marine sediment packages that are morphologically expressed as subparallel ne trending barriers beach ridges and associated back barrier areas characterize the near surface stratigraphic section between the savannah and the ogeechee rivers in effingham county southeastern georgia each barrier back barrier shoreline complex is lower than and cut into a higher older complex each barrier or shoreline complex overlies miocene strata no direct age data are available for these deposits previous researchers have disagreed on their age and provenance using luminescence and meteoric beryllium 10 10 be inventory analyses we estimated a minimum age for the largest westernmost morphologically identifiable and topographically highest barrier beach ridge the wicomico shoreline barrier and constrained the age of a suite of younger barrier beach ridges that lie adjacent and seaward of the wicomico shoreline barrier at the study site the near shore marine estuarine deposits underlying the wicomico shoreline barrier are overlain by eolian sand and an intervening zone of mixing optically stimulated luminescence osl data indicate ages of 43 ka for the eolian sand and 116 ka for the zone of mixing meteoric 10 be and pedostratigraphic data indicate minimum residence times of 33 4 ka for the eolian sand 80 6 ka for the zone of mixing and 247 ka for the paleosol the combined osl and 10 be age data indicate that at this locality the barrier beach ridge has a minimum age of about 360 ka this age for the wicomico shoreline barrier deposit is the first for any pleistocene near shore marine estuarine deposit in southeast georgia that is conclusively older than 80 ka the 360 ka minimum age is in agreement with other geochronologic data for near coastline deposits in georgia and south carolina the geomorphic position of this barrier beach ridge is similar to deposits in south carolina considered to be 450 ka to 1 ma the age and geomorphic data for georgia and south carolina possibly suggest the presence of mis 11 420 360 ka shoreline deposits between 15 m and 28 m above present sea level in the southeastern atlantic coastal plain

frequency dependent attenuation in the crust beneath central france from lg waves data analysis and numerical modeling abstract the quality factor of shear waves in the crust beneath central france is evaluated by the combined use of data analysis and theoretical modeling the measurement is made from lg wave records of 18 earthquakes at 22 short period vertical seismic stations of the french seismic network the geometrical attenuation of lg waves has been calculated through a numerical simulation in a perfectly elastic model the station responses including site effects have been evaluated from lg waves and from records of the seismic noise q has been calculated for a set of 11 frequencies between 0 5 and 10 hz and has been found to be in the form q 290 f 0 52 where f is the frequency the numerical simulation leads to the interpretation of q of lg waves as the mean value of q within the crust theoretical and experimental decay of energy with distance are in very good agreement the lg waves present a different sensitivity to a low q zone whether this zone is associated with the sediments or with scattering in the lower crust the lower crust beneath central france appears from our experimental results to be associated with high values of q

recurrent liquefaction induced by the 1989 loma prieta earthquake and 1990 and 1991 aftershocks implications for paleoseismicity studies sandblows formed in man made lake deposits near watsonville california resulted from the october 1989 m 7 1 loma prieta earthquake and its april 1990 m 5 5 aftershock and a march 1991 m 4 6 aftershock excavations in the dry bed of soda lake expose the subsurface structure of sandblows induced by the october and april events we also made surface observations three days after the march 1991 event lateral spread fissures developed in the lake sediment during the mainshock and the host deposits were vertically offset 3 to 6 5 cm liquefied sand erupted through the fissures onto the dry lake bed and formed sandblow cone deposits these deposits range from low angle conical structures 30 to 50 cm thick and 2 to 5 m in diameter to elongate deposits up to 35 m long sandblows associated with the april 1990 aftershock commonly reoccupied preexisting fissures but also formed new solitary vents sandblows developed during the march 1991 aftershock erupted only through preexisting vents sandblow vents reactivated in april 1990 contain sediment clasts of sandblow deposits formed in the october 1989 mainshock clasts of host sediment were also present in the sand dikes lamination in the sandblow cones and sand dikes shows that they were not formed in a single episode surface cones and feeder dikes composed of multiple laminated subunits represent the three generations of sandblows the subunits suggest that the cone deposits were formed by pulses of water and sediment expelled from the vent the pulses result from cyclic phases of local excess pore pressure and its release in the liquefied bed at depth the three generations of structures at soda lake formed six months to a year apart have distinct tonal and textural differences that may mimic liquefaction structures formed decades or centuries apart this study provides modern analogs for comparison to and interpretation of prehistoric liquefaction structures that are frequently partly eroded or poorly exposed

magnitude the relation of ml to mblg abstract the m blg magnitude developed by nuttli 1973 for the central united states is adapted to other regions of the world by incorporating a specific term for the spatial coefficient of anelastic attenuation using region specific values m blg values are determined for earthquakes occurring near the wwssn stations bks gsc and dug a comparison of the m blg values with published m l magnitudes shows that these two magnitude scales are essentially equivalent between magnitudes 3 to 5 because of this observation we now have a direct way of comparing eastern and western united states earthquake sizes for the purpose of adapting western strong motion data bases to the east and also for understanding teleseismic magnitude biases

evaluation of a seismic event 12 may 2010 in north korea we assess seismological evidence bearing on claims that north korea conducted a small nuclear test on 12 may 2010 in the vicinity of known underground nuclear tests unts in 2006 2009 2013 and 2016 first we use lg wave cross correlation and more traditional methods to locate the 2010 event between about 4 and 10 km southwest of the 2009 test second we compare the relative sizes of regional p and s waves using stations within 400 km of the known north korean nuclear tests to assess the nature of the event we measured p s ratios at different frequencies at first using data from the open station mdj in northeast china for training sets of earthquakes and of explosions we developed a linear discriminant function ldf that in application to p s measured at mdj is most effective in separating the earthquake and explosion populations mdj lacks usable data for the event of interest but we obtained regional data from stations of the nearby dongbei broadband seismographic network dbsn for the 12 may 2010 event and for nearby unts conducted in 2006 and 2009 when our ldf is applied to dbsn data and to data from stations smt and ne3c in china the ldf values measured from p s ratios from known explosions are explosion like but for the 12 may 2010 event the ldf values are earthquake like for frequencies between 6 and 12 hz our method for characterizing earthquakes and explosions on the basis of their regional signals can be widely applied measurements of p s based on the three component waveform data provide better discrimination power than do those based on vertical component data alone electronic supplement 1 tutorial material on the mahalanobis distance squared measure three component linear discriminant function ldf analysis tables of measurements of the log10 p s spectral ratios obtained from waveforms recorded at station mdj for the two training sets and three component discrimination analysis and figures of log p s values measured at 8 hz from vertical component waveforms at station mdj for two training sets and probability distributions for d 1 http www bssaonline org lookup suppl doi 10 1785 0120160111 dc1

evidence for lower crustal ductile strain localization in southern new york historic triangulation data have been analysed to determine whether intraplate seismicity is associated with ongoing ductile deformation in the lower crust the model we have attempted to test is basically analogous to strain accumulation and release along plate boundary strike slip faults like the san andreas fault in california that is beneath an elastic seismogenic upper crust 20 km thick strain is preferentially localized within ductile shear zones in the lower crust due to broad scale plate driving forces the localized lower crustal ductile strain causes stress and strain to accumulate elastically in the brittle crust which is eventually released in crustal earthquakes at greater depths this localized shear deformation probably develops into pervasive ductile flow numerous geodetic measurements along the san andreas fault confirm that earthquakes in the brittle upper crust are produced by the release of elastic strain that results from ongoing ductile shear or slip in the lower crust1 2 we have found evidence of high rates of crustal deformation in southern new york which suggest that localized ductile shear is occurring in the lower crust

seismic strain rates in the central and eastern united states seismic strain rates for the entire central and eastern united states are estimated from historical seismicity and from several seismicity models typical strain rates are estimated to be the on the order of 10 12 to 10 11 per year except near historical sites of large earthquakes where higher rates pertain uncertainties in strain rates are large deformation caused by strain rates less than 10 10 yr 1 is very small compared to average denudation rates denudation and deposition may control the rate of earthquake occurrence in some parts of the central and eastern united states by modifying the vertical stress due to load a simple quantitative model predicts the earthquake occurrence rate in the appalachian mountains from an estimate of the regional denudation rate

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

paleoseismic evidence for recurrence of earthquakes near charleston south carolina a destructive earthquake that occurred in 1886 near charleston south carolina was associated with widespread liquefaction of shallow sand structures and their extravasation to the surface several seismically induced paleoliquefaction structures preserved within the shallow sediments in the meizoseismal area of the 1886 event were identified field evidence and radiocarbon dates suggest that at least two earthquakes of magnitudes greater than 6 2 preceded the 1886 event in the past 3000 to 3700 years the evidence yielded an initial estimate of about 1500 to 1800 years for the maximum recurrence of destructive intraplate earthquakes in the charleston region

structural and tectonic setting of the charleston south carolina region evidence from the tertiary stratigraphic record eleven upper eocene through pliocene stratigraphic units occur in the subsurface of the region surrounding charleston south carolina these units contain a wealth of information concerning the long term tectonic and structural setting of that area these stratigraphic units have a mosaic pattern of distribution rather than a simple layered pattern because deposition erosion and tectonic warping have interacted in a complex manner through time by generating separate structure contour maps for the base of each stratigraphic unit an estimate of the original basal surface of each unit can be reconstructed over wide areas changes in sea level over geologic time generate patterns of deposition and erosion that are geographically unique for the time of each transgression such patterns fail to persist when compared sequentially over time in some areas however there has been persistent repetitive net downward or upward movement over the past 34 m y these repetitive patterns of persistent motion are most readily attributable to tectonism the spatial pattern of these high and low areas is complex but it appears to correlate well with known tectonic features of the region this correlation suggests that the tectonic setting of the charleston region is controlled by scissors like compression on a crustal block located between the north trending adams run fault and the northwest trending charleston fault tectonism is localized in the charleston region because it lies within a discrete hinge zone that accommodates structural movement between the cape fear arch and the southeast georgia embayment