intermediate term predictions of earthquakes in italy algorithm m8 large earthquakes in italy are preceded by a specific seismic activation which could be diagnosed by a reproducible intermediate term earthquake prediction method a modification for lower seismic rate areas of the algorithm known as m8 keilis borok and kossobokov 1990 use has been made of the pfg ing catalog of earthquakes compiled on a regular basis to determine areas and times of increased probability for occurrences of m 6 earthquakes in retroactive simulation of forward prediction for the period 1972 1995 both the 1976 friuli m 6 1 and the 1980 irpinia m 6 5 earthquakes are predicted in the experiment where priority magnitude scale is used the times of increased probability for a strong earthquake to occur tips occupy less than a quarter of the total magnitude space time domain and are rather stable with respect to positioning of circles of investiga tion successful stability tests have been made considering a recently compiled catalog cci97 peresan et al 1997 in combination with the cn algorithm results costa et al 1996 the spatio temporal uncertainty of the prediction could be reduced to 5 the use of m8 for the forward prediction requires the computations to be repeated each half year using the updated catalog

a successful prediction of a strong earthquake in the southwestern hellenic arc by means of the algorithm m8 abstract in an earlier study a current tip time of increased probability has been diagnosed along the southwestern part of the hellenic arc by applying the algorithm m8 in that paper we pointed out that the current tip of duration of five years started at the end of 1986 or at the beginning of 1987 and if the algorithm m8 works reliably then it will be completed by the end of 1992 with an earthquake of a surface waves magnitude in the range 6 0 ms on november 21 1992 an earthquake of ms 6 5 took place in the candidate region in the following we discuss the applicability of the algorithm m8 to delineating critical seismic areas and the necessity of using current tips to focus the attention of multidisciplinary research for evaluating short term precursory phenomena if any

late pleistocene holocene paleoproductivity circulation in the japan sea sea level control on δ13c and δ15n records of sediment organic material organic carbon and total nitrogen contents and their isotope ratios were determined in a sediment core recovered from the japan sea to investigate the record of organic matter resources and paleoproductivity in a semi enclosed marginal sea 13c 15n relationships show that the composition of sediment organic material resulted from the mixing of terrestrial and marine organic matter we found synchronous down core variations in the carbon and nitrogen isotope records which are explained by surface productivity control on the composition of sediment organic material moreover these variations are related to sea level changes which caused variable surface water inflows last glacial sea level lowering increased continental run off leading to water column stratification in the japan sea anaerobic conditions due to basin water stagnation led to the deposition of laminated clay sediment organic c n and isotope ratios fluctuated markedly in the transitional stage from aerobic to anaerobic conditions the fluctuations are likely to have been caused by large scale oscillations in sea level just before the last glacial maximum

origins and paleoceanographic significance of laminated muds from the ulleung basin east sea sea of japan abstract a detailed facies analysis of long piston core sediments from the ulleung basin reveals four mud facies laminated mud crudely laminated mud bioturbated mud and homogenous mud the laminated and homogeneous muds were most likely deposited from turbidity currents whereas the bioturbated and crudely laminated muds were formed by hemipelagic pelagic sedimentation under well oxygenated and poorly oxygenated bottom water conditions respectively a detailed analysis of vertical distribution of the mud facies together with a chronostratigraphic framework derived from correlative tephra layers with known eruption ages reveals paleoenvironmental changes during the late quaternary during the period between 49 and 23 ka eustatic lowering of sea level facilitated frequent slope failure resulting in repeated deposition of fine grained turbidites on the basin floor normal hemipelagic sediments were intensively bioturbated under well oxygenated bottom water conditions during the period between 23 and 13 to 11 ka deposition from turbidity currents continued but hemipelagic sediments were non bioturbated under poorly oxygenated bottom water conditions the bottom water deoxygenation is attributed to further lowering of sea level during the last glacial period and consequent intensified stratification in the water column by freshwater supply to the nearly isolated sea primary laminae preserved in the crudely laminated mud generally exhibit low compositional bimodality in backscattered electron images which suggests low surface primary productivity and presence of superficial micro bioturbation after rapid rise of sea level at 13 to 11 ka the slopes were stabilized and pelagic sedimentation has prevailed under well oxygenated bottom water conditions

plio quaternary seismic stratigraphy and depositional history of the ulleung basin east sea association with debris flow activity abstract we analyzed multi channel seismic reflection profiles to decipher the plio quaternary stratigraphic architecture and resolve the depositional history of the ulleung basin a detailed seismic stratigraphic interpretation revealed nine seismic units units 1 9 separated by unit boundaries in the plio quaternary deposits of the ulleung basin unit 1 pliocene is dominated by debris flow deposits dfds throughout the basin units 2 9 quaternary are characterized by stacked dfds interbedded with thin hemipelagic sediments along the southern slope whereas the northern basin floor is filled with hemipelagic and pelagic sediments the areal distribution and dimensional characteristics of the dfds indicate that sedimentation in the ulleung basin has been controlled by a combination of tectonic movement eustatic changes in sea level and gas hydrates dissolution and dissociation during the pliocene unit 1 sedimentation was mainly controlled by tectonic movements causing margin wide slope failures under the compressional regime large sediment deposits were supplied to the basin through mass transport processes resulting in an abundance of dfds throughout the basin during the quaternary units 2 9 compressive stress decreased sharply causing the dfds to retreat landward at that time sedimentation was mainly influenced by eustatic changes in sea level and gas hydrates dissolution and dissociation as the sea fell to the lowstand slope failures were activated by the generation of high pore water overpressure and the generation of weak layers in the sediments resulting in stacked dfds however as the sea level rose to the highstand sediment was primarily deposited via hemipelagic and pelagic processes due to increased hydrostatic pressure and slope stability

refining the eruptive history of ulleungdo and changbaishan volcanoes east asia over the last 86 kyrs using distal sedimentary records abstract the eruptive histories of ulleungdo south korea and changbaishan north korea china border volcanoes are not well constrained since their proximal stratigraphies are poorly exposed or largely inaccessible however determining the past behaviour of these volcanoes is critical since future eruptions are likely to disperse ash over some of the world s largest metropolitan regions alkaline tephra deposits erupted from both centres are routinely identified in marine cores extracted from the sea of japan as well as high resolution lacustrine records east of the volcanoes here we review the distal ash occurrences derived from ulleungdo and changbaishan and provide new data from the lake suigetsu central honshu japan sediment core in order to provide a more complete and constrained eruption framework the intensely dated lake suigetsu archive provides one of the most comprehensive distal eruption records for both centres despite being located ca 500 km e of ulleungdo and ca 1000 km sse of changbaishan the suigetsu record is utilised to precisely date and geochemically fingerprint using major minor and trace element glass compositions ash fall events that reached central honshu here we identify a new non visible cryptotephra layer in the suigetsu sediments which reveals a previously unreported explosive event from changbaishan at 42 750 42 323 intcal13 yrs bp 95 4 confidence interval this event is chronologically and geochemically distinct from the b j baegdusan japan basin tephra reported in the sea of japan ca 50 ka furthermore we also confirm that the widespread u ym tephra erupted from ulleungdo reached central japan and is herein dated to 40 332 39 816 intcal13 yrs bp 95 4 confidence interval this terrestrial 14c derived age of the u ym can be used to constrain the chronology of marine records containing the same marker layer this reviewed and integrated tephrostratigraphic framework highlights the pivotal role that distal sedimentary records can play in evaluating the eruptive histories and hazard potential of ulleungdo and changbaishan

geochemistry of surface sediments in the southwestern east japan sea abstract we analyzed 77 surface sediment samples collected in the southwestern east japan sea from the korea strait through the ulleung basin and the korea plateau for grain size calcium carbonate organic carbon and major na mg al fe k ca and ti and trace elements p mn sr li sc v cr co ni zn cu and pb the chemical composition of the surface sediments was found to be highly variable spatially cluster analysis of surface sediment chemical compositions indicated five major geochemical sedimentary environments basin lower slope coast and upper slope inner shelf and outer shelf continental shelf sediments were rich in shell fragments and had relict and coarse grained characteristics recent fine grained sediments were only distributed in coastal slope and basin areas concentrations of al k ca ti cr and sc were highest in the coastal and upper slope areas and decreased with water depth elemental ratios using major and trace elements indicated that coastal and upper slope detrital sediments were mixtures of sediments derived from the changjiang yangtze and nakdong rivers although the concentrations of organic carbon p mn v co ni cu and pb increased with water depth their distribution patterns indicated authigenic v cu and pb and diagenetic fe p mn co and ni origins the distribution pattern with water depth suggested that the chemical composition of surface sediment was determined by sedimentologic and geochemical processes such as the supply of detrital and biogenic materials and authigenic and post depositional diagenetic processes in sediments

integrated geologic and geophysical interpretation of the buraco da velha copper deposit rondonia brazil a basis for exploring in related environments abstractthe buraco da velha copper deposit lies at the northern limit of the parecis basin in the colorado graben rondonia brazil new geophysical data indicate the presence of a magnetic source below and to the north of the buraco da velha deposit where it corresponds with high gamma ray u th and k counts we have studied the source of the magnetic anomaly and delineated it through derivative transforms euler deconvolution maximin total magnetization direction analysis staged inverse modeling th k ratio and radiometric ternary imaging the magnetic anomaly is elongated in the east west direction and measures 23 6 km and the top of the source is estimated to lie at depths mostly between 50 and 100 m based on the magnetic model we indirectly estimate a jurassic to cretaceous age which is compatible with the 180 80 ma range dated for the copper mineralization gamma ray data are consistent with the hydrothermal alteration in the sedimentary cover and with the presence of an intrusion in the s

quaternary sedimentation in the japan arc trench system quaternary sedimentation around the japanese islands took place in a dynamic morphotectonic setting that included seismically active trenches a large back arc basin and a tectonically complex slope environment characterized by en echelon folds and fault bounded ridges with small intervening basins these structural ridges created barriers to sediment transport by bottom currents and acted as dams on the slope behind which quaternary sediments ponded sea levels higher than at present throughout most of the pleistocene impeded escape of coarse sediments from the shelf except through a few major submarine canyons that extended completely across the shelf and slope thus deeper water sediments in both the japan fore arc and back arc are dominantly hemipelagic muds and subordinate mud turbidites a drop in sea level to about 130 m below the present level at approximately 18 000 yr b p resulted in deposition of widespread fluviomarine sands and gravels on the continental shelf and an increase in sand silt turbidites in the latest pleistocene record in both the fore arc and the back arc sandy turbidites interbedded with hemipelagic mud or mud turbidites occur particularly in the trench fill of nankai trough southwest japan trench in some fore arc basins on the south west japan slope and in the western part of the japan sea back arc basin they are sparsely represented in the japan trench and the northeast japan slope apparently owing to the poor development of throughgoing submarine canyons on the northeast slope diatomaceous and calcareous muds and oozes occur in some parts of both the fore arc and the back arc and volcanic ash and pumice are virtually ubiquitous throughout the quaternary sediment record in nearly all parts of the japan arc trench system quaternary sedimentation rates are less than about 30 m m y in the open pacific deep sea basins seaward of the trenches but they increase toward the fore arc and reach values as high as 230 m m y in the japan trench inner slope and 300 900 m m y in the trench fill of nankai trough back arc sedimentation rates for the total quaternary range from 20 140 m m y and latest pleistocene holocene rates range from 65 230 mm 1 000 yr

relationships between magnetic and structural fabrics revealed by variscan basement rocks subjected to heterogeneous deformation a case study from the klodzko metamorphic complex central sudetes poland

provenance of turbidites in the ulleung tsushima back arc basin east sea sea of japan in the inactive ulleung back arc basin accumulation of turbidites was predominant over hemipelagic deposition since about pliocene time most of the late pleistocene turbidite layers deposited in the time interval between major volcanic eruptions at about 9 300 21 000 and 50 000 yrs b p contain heavy minerals that were derived mainly from the stable craton of the east korean peninsula during major eruptions however turbidites composed dominantly of unstable minerals originated mainly from the volcanic arc of northwestern honshu a few turbidite layers contain mineral assemblages common to both margins turbidites in the ulleung interplain gap were derived from the adjacent islands and banks modified journal abstract

widespread submarine tephras around japan petrographic and chemical properties abstract in deep sea sediments around the japanese islands tephra layers are frequently recognized and some tephras can be identified by petrographic and chemical features and correlated to source volcanoes of both japan and korea most tephras distributed over more than several hundred kilometers from the source volcanoes were presumably carried away by the dominant westerly wind six characteristic marker tephras in deep sea sediments can be identified and correlated according to their distribution and grain size petrography and chemistry they play an important role in compiling the late quaternary chronology of the deep sea sediments distributed around the japanese islands petrographic and geochemical studies reveal that the refractive index of volcanic glass shards in tephras is controlled by the amount of total transition metal oxides rather than the amount of sio 2 we propose a new equation relating refractive index to glass shard chemistry

magnetic fabrics and strain in pencil structures of the knobs formation valley and ridge province us appalachians pencil structures which are found in weakly deformed mudrocks reflect the bedding cleavage intersection in weak to moderatelycleaved rocks their presence indicates conditions where bedding and cleavage fabrics are approximately equal in intensity we have determined the anisotropy of magnetic susceptibility ams in pencil structures from a sequence of mudstones of the ordovician knobs formation in the valley and ridge province of the us appalachians magnetic mineralogy was determined by x ray analysis and lowtemperature susceptibility measurements distribution of the magnetic ellipsoid axes is consistent with the incipient tectonic fabric of the pencil mudstones the maximum susceptibility axes parallel the pencils long axes while the minimum axes of susceptibility are normal to the primary sedimentary fabric independent strain quantification permits a correlation between magnetic fabric and tectonic strain an exponential relationship between the ams shape parameter t and tectonic shortening has been found for the interval of 10 25 shortening shortening 17 p exp t this relationship appears to be supported by tectonic strains up to 40 the t parameter t lnf 2 lnl lnl lnf where l lineation is kmax kint and f foliation is kint kmin describes the shape of the magnetic susceptibility ellipsoid which appears more sensitive to strain than past correlation attempts with the magnetic intensity parameter p or p 0 whereas this correlation between strain and ams is only valid within a restricted window of strain 10 40 shortening it establishes the magnitude and directions of tectonic strain in weakly deformed clay rich rocks where strain indicators are otherwise lacking or are poorly developed q 2003 published by elsevier science ltd

anisotropy of magnetic susceptibility of heated rocks abstract heating produces changes which does not always correspond to simple enhancement of the magnetic fabric two methods are proposed to determine the anisotropy of magnetic susceptibility of the ferrimagnetic minerals formed or that have disappeared by chemical change during successive heating the first diagonalizes the tensor from the difference between each tensor term before and after heating the second employs linear regression for each tensor term made with the values obtained throughout a thermal treatment when the same magnetic fabric is obtained from several thermal steps it cannot be related to randomly oriented ferrimagnetic minerals instead the newly formed fabric must be related to characteristics of the pre existing rock by comparing this ferrimagnetic minerals fabric with the initial whole rock fabric we can distinguish cases where heating simply enhances pre existing fabric from those where thermal treatment induces a different fabric relative to the pre heating fabric this different fabric may simply be an inverse fabric or one whose principal susceptibility axes are oriented in a different direction related to petrostructural elements other than those defining the initial fabric

identification and correlation of visible tephras in the lake suigetsu sg06 sedimentary archive japan chronostratigraphic markers for synchronising of east asian west pacific palaeoclimatic records across the last 150 ka abstract the lake suigetsu sg06 sedimentary archive from honshu island central japan provides a high resolution palaeoenvironmental record including a detailed record of explosive volcanism from japan and south korea thirty visible tephra are recorded within the 73 m long sg06 core which spans the last 150 ka here we describe and characterise these tephras based on major element glass composition which is useful for the identification and correlation of these tephras and the age models of the records in which they are found utilising the large number of radiocarbon measurements n 600 from terrestrial plant macrofossils in the lake suigetsu sg06 record we are able to provide precise and accurate ages for the tephras from eruptions within the last 50 ka glass compositional data of some of the largest eruptions from japan k ah at aso 4 aso a aso d and ata sampled at proximal outcrops are also presented these data show that the major element glass chemistry is distinctive for many of the visible sg06 tephra units and allows some of the layers to be correlated to known eruptions from volcanoes in japan and south korea namely k ah sg06 0967 u oki sg06 1288 at sg06 2650 aso 4 sg06 4963 sg06 4979 k tz sg06 5181 aso abcd sg06 5287 and ata sg06 5181 the following ages were obtained for the sg06 tephra units 3 966 4 064 cal ka bp 95 4 probability range for the sg06 0588 tephra 10 242 10 329 cal ka bp 95 4 probability range for sg06 1293 19 487 112 sg06 2012 ka bp 2 for sg06 1965 28 425 194 sg06 2012 ka bp 2 for sg06 2504 28 848 196 sg06 2012 ka bp 2 for sg06 2534 29 765 190 sg06 2012 ka bp 2 for sg06 2601 29 775 191 sg06 2012 ka bp 2 for sg06 2602 43 713 156 sg06 2012 ka bp 2 for sg06 3485 46 364 202 sg06 2012 ka bp 2 for sg06 3668 49 974 337 sg06 2012 ka bp 2 for sg06 3912 50 929 378 sg06 2012 ka bp 2 for sg06 3974 and improved ages for two of the most important tephra markers across japan the k ah 7 165 7 303 cal ka bp at 95 4 probability range sg06 0967 and at tephra 30 009 189 sg06 2012 ka bp at 2 sg06 2650

reply to the discussion of deb 2013 on the paper of saha et al 2013 entitled tectono magmatic evolution of the mesoproterozoic singhora basin central india evidence for compressional tectonics from structural data ams study and geochemistry of basic rocks abstract we appreciate that our attempt to document deformation pattern within the mesoproterozoic singhora group india and to resolve some key stratigraphic issues in chhattisgarh geology patranabis deb and chaudhuri 2008 dhang and patranabis deb 2012 in recent times has attracted the attention of deb we whole heartedly welcome the keen interest shown by deb in our paper and discussions attempted by him on different aspects of the paper here we offer our strong rebuttal of his imaginative discussions principally because the claims made by deb are neither supported by outcrop based field data nor through any available subsurface geophysical data it appears that the key concern of deb 2013 was to force fit the structural grains of the sonakhan greenstone belt within the deformation pattern of singhora cover sediments upholding an unsubstantiated assumption that the sonakhan greenstones belt constitutes the basement for the singhora basin without citing any evidence outcrop geophysical or bore hole showing sonakhan metamorphics in the basement of the singhora basin he plotted the structural data of the sonakhan greenstone belt and attempted comparison of those with the bedding attitudes of the singhora cover sediments and claimed that the possible rejuvenation of basement faults triggered folding in the singhora cover sediments leaving aside the issues of lack of any field support available geophysical results 3 layer gravity survey by srinivas et al 2000 magnetic survey by srinivas et al 2004 and short borehole observations pers comm mukherjee a 2012 all clearly demonstrates unclassified archean paleoproterozoic granites and gneisses of the bastar craton as basement for the singhora basin not the sonakhan greenstones neither is the presence of any basin scale fault inferred from the basement of the singhora basin in any geophysical model the result of magnetic survey along the basna sohela transect carried out by srinivas et al 2004 which represents the singhora basement in particular clearly shows granites as immediate basement for the singhora as the very assumption of deb 2013 i e that the sonakhan represents the basement to the singhora basin does not stand either on his own field data or on any strong reasoning we refrain from any further discussion on this topic instead we frame our reply on the doubts raised by deb 2013 on the mapping field analysis and concepts used in our paper saha et al 2013

paleoenvironmental changes in the japan sea during the last 85 000 years five distinct changes in the paleoenvironment of the japan sea within the last 85 000 years are revealed from the sedimentary record of a piston core recovered from the oki ridge changes in both surface and deepwater conditions are registered by changes in lithology calcium carbonate content organic carbon content oxygen and carbon isotope ratios and microfossil assemblages including calcareous nannoplankton diatoms radiolaria and foraminifera between 85 and 27 ka the warm tsushima current did not flow into the japan sea and cold surface water conditions prevailed environments at the seafloor fluctuated between dysaerobic to weakly oxic conditions between 27 and 20 ka freshwater input to the japan sea probably from the huang ho river in china stratified the water column and the severe anoxic conditions eliminated most benthic fauna between 20 and 10 ka the cold oyashio current flowed into the japan sea through the tsugaru strait reestablishing deepwater ventilation shallow water benthic assemblages of the north pacific ocean subsequently colonized the japan sea and occupied the vacant niches of the deep basins between 10 and 8 ka the foraminifer compensation level fcl gradually rose to a depth shallower than 1000 m and bottom conditions changed from dysaerobic to oxic at 10 ka the warm tsushima current started to flow into the japan sea through the tsushima strait to establish the modern oceanographic regime which has existed since 8 ka the eustatic sea level during the last glacial maximum was above the sill depths 130 m of the tsushima and tsugaru straits assuming that tectonic movements at these straits were negligible for the last 20 ka

late pleistocene holocene paleoenvironmental changes inferred from the diatom record of the ulleung basin east sea sea of japan abstract the diatom floral record from two piston cores 00ghp 01 and 00ghp 07 taken from the southwestern margin of the ulleung basin east sea sea of japan reveals a series of well defined changes in glacio eustatic sea level and paleoceanographic conditions during the late pleistocene holocene six assemblage zones and two barren zones in 00ghp 01 and four assemblage zones in 00ghp 07 are erected respectively on the basis of frequency of variations in and occurrences of biostratigraphically significant diatom species all assemblage zones have been strongly influenced by the tsushima warm current twc the twc has an important affect on controlling the distribution and composition of diatom flora which in turn reveal the history of the twc in this area the distribution pattern of diatoms in the diatom assemblages reveals sea surface temperature and salinity affected by the sediments type and terrigenous material input diatom temperature td values show that the site of 00ghp 01 in the ulleung basin has been influenced by a relatively enhanced twc twice during the deposition of lowermost and uppermost intervals a relatively weak twc was recorded in the middle interval since the latest pleistocene the diatom assemblages of 00ghp 07 represent an apparently continuous late quaternary record spanning the last glacial maximum bolling allerod younger dyras and holocene high abundance of a low salinity coastal water diatom paralia sulcata may reflect the influx of the east china sea water through the korean strait to the east sea sea of japan during the last glacial maximum the sea level was low enough that selected basin with shallow sills along the margin of the east sea sea of japan became isolated from the pacific ocean salinity also decreased due to increased freshwater input from rivers draining the surrounding lands the density stratified water column may have prevented vertical mixing and resulted in anoxic bottom water conditions

fine structures of turbidite and associated muds in the ulleung tsushima basin east sea sea of japan abstract the ulleung basin is a presently tectonically inactive back arc basin it is a nonfan slope centered sedimentary basin in which up to 800 m of mostly fine grained turbidites have accumulated the precursors of these turbidity currents were slides slumps and debris flows on the slope and near the base of slope an ideal mud turbidite sequence identified in cores from the basin includes divisions of laminated mud e1 graded mud e2 and homogeneous mud e3 associated with convolute mud e4 bioturbated mud f1 bioturbated mud with authigenic pyrite f2 and indistinctly laminated mud g e1 through e4 muds are turbiditic in origin as evidenced by an absence of bioturbation preferred orientation of large sediment particles liquefaction and high organic carbon content all suggestive of rapid deposition from unidirectional flow the indistinctly laminated mud g is characterized by poorly defined laminae slight bioturbation intermediate organic carbon content and large amounts of skeletal debris in the silt fractions in contrast to both the turbiditic and bioturbated muds this mud is suggestive of deposition from bottom currents the bioturbated mud f1 resulted from slow particle by particle settling in the postglacial oxic environment whereas the bioturbated mud with pyrite filaments f2 is due to deposition in suboxic environment when the basin was isolated from the pacific during the last glacial period both bioturbated muds are low in organic carbon poorly sorted and characterized by random orientation of large sediment particles

partitioning of moderately siderophile elements among olivine silicate melt and sulfide melt constraints on core formation in the earth and mars abstract this study investigates the effects of variations in the fugacities of oxygen and sulfur on the partitioning of first series transition metals v cr mn fe co ni and cu and w among coexisting sulfide melt silicate melt and olivine experiments were performed at 1 atm pressure 1350 c with the fugacities of oxygen and sulfur controlled by mixing co2 co and so2 gases starting compositions consisted of a cao mgo al2o3 sio2 feo na2o analog for a barred olivine chondrule from an ordinary chondrite and a synthetic komatiite the f o 2 f s 2 conditions ranged from log f o 2 7 9 to 10 6 wi log f s 2 values ranging from 1 0 to 2 5 our experimental results demonstrate that the f o 2 f s 2 dependencies of sulfide melt silicate melt partition coefficients for the first series transition metals are proportional to their valence states the f o 2 f s 2 dependencies for the partitioning of fe co ni and cu are weaker than predicted on the basis of their valence states variations in f o 2 f s 2 conditions have no significant effect on olivine melt partitioning other than those resulting from f o 2 induced changes in the valence state of a given element the strong f o 2 f s 2 dependence for the olivine silicate melt partitioning of v is attributable to a change of valence state from 4 to 3 with decreasing f o 2 our experimentally determined partition coefficients are used to develop models for the segregation of sulfide and metal from the silicate portion of the early earth and the shergottite parent body mars we find that the influence of s is not sufficient to explain the overabundance of siderophile and chalcophile elements that remained in the mantle of the earth following core formation important constraints on core formation in mars are provided by our experimental determination of the partitioning of cu between silicate and sulfide melts when combined with existing estimates for siderophile element abundances in the martian mantle and a mass balance constraint from fe the experiments allow a determination of the mass of the martian core 17 to 22 wt of the planet and its s content 0 4 wt these modeling results indicate that mars is depleted in s and that its core is solid

slope stability change from late pleistocene to holocene in the ulleung basin east sea japan sea abstract a wide variety of mass movement deposits prevail along the entire margin of ulleung basin overlain by a hemipelagic mud unit 1 2 m thick the boundary between the lower turbidite sequence and the upper hemipelagic mud on the basin plain is distinct and approximately coincides with the well known basin wide ash layer ulleung ash of early holocene age in the absence of significant terrigenous sediment input the lithologic change from the turbidite to hemipelagic mud may reflect physical effects of glacio marine eustatic sea level change sea level lowering during the glacial period may have generated excess pore pressure within the sediments caused by reducing hydrostatic confining pressure and facilitated triggering of the deep water slope failure by earthquakes storm waves may also have affected the uppermost slope area to induce small scale slope instabilities during the lowered sea level stand these glacial factors destabilizing the slope appear to have enhanced large scale slope failures during the late pleistocene in contrast the topmost hemipelagic mud attests to a stable slope phase associated with raised sea level in the holocene consistent with the infinite slope stability analyses calculations of the sedimentation rates based on c 14 dates of several ash layers indicate that the pre holocene turbidites on the basin plain had accumulated at an average rate of 40 cm 1000 years with a minimum recurrence interval of 50 years during the late pleistocene mass flux estimations between the slumps and turbidites suggest a predominance of the nondisintegrative mode of slope failures in the ulleung basin in each event of slope failure most of the failed mass rested on the slope as slide slump blocks and only its meager portions were deposited on the basin plain as turbidite layers

gas hydrates in ocean bottom sediments gas hydrates belong to a special category of chemical substances known as inclusion compounds an inclusion compound is a physical combination of molecules in which one component becomes trapped inside the other in gas hydrates gas molecules are physically trapped inside an expanded lattice of water molecules the pressures and temperatures beneath arctic water depths greater than 1 100 ft 335 m and subtropical water depths greater than 2 000 ft 610 m are suitable for the formation of methane hydrate theoretical depths to the base of a gas hydrate layer in ocean bottom sediments are determined by assuming 1 a constant hydrostatic pressure gradient 2 two typical hydrothermal gradients 3 variable geothermal gradients and 4 pure methane hydrated with conna e seawater in addition to pressure and geothermal gradient other variables affecting the stability of gas hydrate are examined these variables are hydrothermal gradient sediment thermal conductivity heat flow hydrate velocity gas composition and connate water salinity if these variables are constant in a lateral direction and the above assumptions are valid a local geothermal gradient can be determined if the depth to the base of a gas hydrate is known the base of the gas hydrate layer is seen on seismic profiles as an anomalous reflection nearly parallel to the ocean bottom cross cutting geologic bedding plane reflections and generally increasing in sub ocean bottom time with increasing water depth the acoustic impedance is a result of the relatively fast velocity hydrate layer overlying slower velocity sediments in addition free gas may be trapped beneath the hydrate thereby enhancing the reflection

extensive ash falls in and around the sea of japan from large late quaternary eruptions abstract five widespread ashes of late quaternary age have been recognized on land and also in deep sea sediments in and around the sea of japan all are favorable for determining the magnitude and type of the great eruptions and for establishing a quaternary chronology around japan accurate determination of refractive indices of volcanic glass shards and phenocrysts together with chemical data have enabled successful characterization of the tephra layers and correlation between land and sea of the five tephras two are alkalic and are the products of major eruptions of two korean volcanoes the baegdusan tomakomai ash b tm and the ulreung oki ash u oki the b tm ash is recognized at the top of most cores in the northern part of the sea of japan and also on hokkaido and the northern part of honshu where a reliable archeological age is given around the 11th century the u oki ash occurs between the kikai akahoya and aira tn ashes in cores from adjacent to the ulreung do to central honshu where three radiocarbon ages of around 9300 yr b p were obtained the other three tephras are subalkalic and are correlated with large scale eruptions producing voluminous pyroclastic flows and calderas in kyushu the kikai akahoya k ah aira tn at and aso 4 ashes the former two have been well described already but their fallout areas are partly revised in this manuscript the at ash is the most prominent marker recognized not only on land of japan but also in cores from the whole area of the sea of japan and part of the pacific ocean the airfall aso 4 ash simultaneous with the aso 4 pyroclastic flow eruption is also described it mantles very extensive areas and serves as an important time marker about 70 000 years ago

depositional features of co genetic turbidite debrite beds and possible mechanisms for their formation in distal lobated bodies beyond the base of slope ulleung basin east sea japan sea abstract a detailed analysis of the mr1 11 12 khz sonar images chirp 2 7 khz profiles core sediments and 14 c ages from the latest quaternary lobated bodies lb on the deep 2100 m water depth basin plain of the western ulleung basin reveals depositional features and context of co genetic turbidite debrite beds in the lb on the distal setting and a plausible mechanism for generating these beds eight lb are present in the basin plain ca 30 60 km beyond the base of slope and were generally deposited retrogressively older and more distal lb 1 4 have large dimensions 27 km long 15 25 km wide in contrast younger and less distal lb 5 8 are small 8 8 31 5 km long 1 2 12 km the muddier larger lb 1 and 2 were most likely originated from the relatively large scale sediment failures on the muddy upper slopes 350 400 m water depth between 18 5 and 20 0 cal ka b p on other hand the sandier smaller lb 6 and 7 were deposited between 17 0 and 17 5 cal ka b p probably by the relatively small scale sediment failures on the sandy uppermost slope shallower than 350 400 m water depth in lb 1 a lower sandy mud turbidite is transitional upward into an upper mud matrix debrite having small rounded mud clasts in contrast lb 6 exhibits a gradual upward change from a lower clay poor sandy turbidite to an upper clay rich sand matrix debrite with large interlocking mud clasts each mixed bed in lb 1 and 6 can represent a co genetic or linked turbidite debrite bed formed by the down dip flow transformation from turbidity current to debris flow at a point during the same event the abundant large scale up to 20 25 m deep 3 5 km long erosions of fine grained substrates near the base of slope area suggest that the down dip transformation was driven by incorporation of mud via erosional bulking by turbidity currents reaching the base of slope area the different clay sand content and size shape of mud clasts in the co genetic turbidite debrite beds between lb 1 and 6 imply that the composition sandy or muddy and dimension of initial turbidity current approaching the base of slope the volume of eroded masses from the fine grained substrates and the transport distance of sediment gravity flows from the erosional areas of muddy substrates can be all important factors controlling the depositional styles of co genetic turbidite debrite beds

revisiting the origin of organic matter and depositional environment of sediment in the central ulleung basin east sea since the late quaternary abstract by analyzing sedimentary geochemical data from three piston cores in the central ulleung basin east sea we discuss the origin of organic matter and the depositional environment of sediments from marine isotope stage mis 3 to 1 downcore profiles show that the values of toc total organic carbon tn total nitrogen and 13corg are the lowest values during mis 2 and the highest during mis 1 the relationship between toc tn and 13corg shows that most data fall in the region of the marine algae irrespective of mis stage which illustrates that the organic matter has been predominantly produced by a marine source rather than by a terrestrial source since the late quaternary however depleted 13corg values are discretely observed during mis 2 and mis 3 particularly in dark laminated mud dlm which appears to reflect the influence of episodic event by the east asian monsoon rather than the organic matter source changing by lower sea level previous sedimentological studies in the ulleung basin reported that the depositional environment of sediment in mis 2 was more reducing than during mis 1 and mis 3 but our geochemical data do not support this interpretation the abundance of most redox sensitive trace elements e g mn v u and mo has not significantly varied from mis 3 to mis 1 in addition the ratios of redox sensitive trace elements e g ni co v cr v ni u th and v v ni indicate a predominantly oxic or suboxic environment the bottom water condition was similarly oxic to suboxic during times of sediment deposition since the late quaternary the sedimentary layers containing tephra and foraminiferal shell fragments illustrate abnormal element al ratios suggesting that these allochthonous sediment sources are one of important factors controlling the geochemical composition of sediments in the ulleung basin

application of proton microprobe data to trace element partitioning in volcanic rocks abstract in situ proton microprobe analyses are used to calculate partition coefficients d for mn fe cu zr ga rb sr y zr ba and pb and more restricted data for ni ge nb and as in pyroxenes olivines biotites hornblendes feldspars and fe ti oxides from 32 volcanic rocks all with glassy matrices these range from leucitite and picritic basalt to high silica and peralkaline rhyolites data for pigeonite aenigmatite allanite and leucite are included where these occur as additional phases coefficients have also been rayleigh fractionation corrected this correction being significant for those elements with high coefficients in specific mineral phases and where pronounced crystallisation has occurred partition coefficients are presented as plots vs nbo t ratios of coexisting glasses melts negative correlations are observed based on log transformed data for mn zn fe and y pyroxenes mn zn and fe olivines mn and zn fe ti oxides nb y sr and zr hornblendes sr plagioclase and ba cu zn and fe feldspars these element partition coefficients are not correlated with bulk mineral compositions zr and ga are not correlated with either glass or mineral compositions except zr in hornblende the correlations support the role of melt polymerisation in controlling element partitioning at least for those elements listed although possible effects of temperature cannot be uniquely isolated in the present data set the coefficients presented here are generally consistent with published values for equivalent rock compositions one difference being that some of the higher published coefficients e g sr in plagioclase are not matched in the present data set from a practical viewpoint the relative regularity of the coefficient data presented does facilitate choice of relevant coefficient values that are required for petrogenetic modelling procedures

sedimentary features of seismoturbidites triggered by the 1983 and older historical earthquakes in the eastern margin of the japan sea abstract both mass failure deposits and turbidites are widely distributed in the epicentral area of the 1983 earthquake mw 7 9 in the eastern margin of the japan sea this basin is semi enclosed with no active conduits for the entrance of coarse detrital sediments seismic reflection surveys and sediment cores reveal that mass failure deposits which are distributed on the continental slopes merge into turbidites in the basin plain hence the mass wasting process is a major transportation process in this region one gravity core gh93 816 was recovered from the southeastern margin of the japan basin close to the epicentral area of the 1983 japan sea earthquake sedimentological results show that five turbidite beds are intercalated in the top 68 cm of the column occurrence of the b tm tephra at the depth of 68 71 cm indicates that these turbidite beds were developed during the last 1000 years the high 137cs concentration in the top 20 cm of the core implies that the uppermost turbidite bed was deposited after 1954 based on these age limits for the top and the bottom of the studied interval we estimate the recurrence intervals of turbidites as 160 330 years we suggest that these turbidites were generated by submarine slides which were triggered by the 1983 and older historical earthquakes in this region these seismoturbidites are characterized by amalgamated beds irregular structure sequences grain size breaks fluctuations abrupt changes in composition within bed and variable composition among beds from these features we infer that deposition resulted from a series of turbidity currents associated with multiple or line sources for example multiple shallow slides that were regionally initiated by the same earthquake the sedimentary features described herein may be useful as criteria for identifying modern seismoturbidites in other settings as well as seismoturbidites in the geologic record however further study is needed for the distinction of this type of turbidites from other types e g tempestites reflected turbidites

discussion of saha et al 2012 precambrian research tectono magmatic evolution of the mesoproterozoic singhora basin central india evidence for compressional tectonics from structural data ams study and geochemistry of basic rocks abstract the discussion of saha et al precambrian research 2012 doi 101016 j precamres 2012 03 004 2012 tectono magmatic evolution of the mesoproterozoic singhora basin central india evidence for compressional tectonics from structural data ams study and geochemistry of basic rocks in precambrian research is placed within the broader context of what is known and what is unknown about the shallow crustal deformation structures and the interplay of deformation in the basement and cover rocks

post 19 ka b p eruptive history of ulleung island korea inferred from an intra caldera pyroclastic sequence ulleung island is a quaternary volcanic island located in the mid western part of the east sea sea of japan back arc basin which has erupted from the pliocene until the late holocene this study focuses on reconstructing the latest eruptive history of the island by describing the sedimentological and stratigraphic characteristics of the most recent trachytic phonolitic pyroclastic sequence named the nari tephra formation this formation is preserved as a succession of unwelded pyroclastic and epiclastic deposits within an embayed margin of the nari caldera the embayment acted as a topographic trap for proximal pyroclastic deposits and contains a complete record of the past 19 000 years of eruption history the formation includes evidence for five separate eruptive episodes member n 1 to n 5 with intervening weathered and or soil horizons indicating hundreds to thousands of years of repose between each eruption eruption styles and depositional mechanisms varied between and during individual episodes reflecting changing dynamics of the magma plumbing system magmatic gas coupling and a variable role of external water extra caldera sequences show that only a few of these eruptions generated sustained eruption columns or pyroclastic density currents pdcs large enough to overtop the caldera wall thus tephra sequences outside the caldera provide an underestimate of eruption frequency and care needs to be taken in the interpretation and correlation to distal tephra sequences recognized in marine and terrestrial records in addition topographic effects of caldera structures should be considered for the assessment of pdc related hazards in such moderately sized pyroclastic eruptions

role of naturally occurring gas hydrates in sediment transport naturally occurring gas hydrates have the potential to store enormous volumes of both gas and water in semi solid form in ocean bottom sediments and then to release that gas and water when the hydrate s equilibrium conditions are disturbed therefore hydrates provide a potential mechanism for transporting large volumes of sediments under the combined low bottom water temperatures and moderate hydrostatic pressures that exist over most of the continental slopes and all of the continental rises and abyssal plains hydrocarbon gases at or near saturation in the interstitial waters of the near bottom sediments will form hydrates the gas can either be autochthonous microbially produced gas or allochthonous catagenic gas from deeper sediments equilibrium conditions that stabilize hydrated sediments may be disturbed for example by continued sedimentation or by lowering of sea level in either case some of the solid gas water matrix decomposes released gas and water volume exceeds the volume occupied by the hydrate so the internal pressure rises drastically if large volumes of hydrate are decomposed part of the once rigid sediment is converted to a gas and water rich relatively low density mud when the internal pressure due to the presence of the compressed gas or to buoyancy is sufficiently high the overlying sediment may be lifted and or breached and the less dense gas cut mud may break through such hydrate related phenomena can cause mud diapirs mud volcanos mud slides or turbidite flows depending on s diment configuration and bottom topography

paleoseismicity along the southern kuril trench deduced from submarine fan turbidites abstract large m 8 damaging interplate earthquakes occur frequently in the eastern hokkaido region northern japan where the pacific plate is subducting rapidly beneath the okhotsk north american plate at approximately 8 cm yr 1 with the aim of estimating the long term recurrence intervals of earthquakes in this region seven sediment cores were obtained from a submarine fan located on the forearc slope along the southern kuril trench japan the cores contain a number of turbidites some of which can be correlated among the cores on the basis of the analysis of lithology chronology and the composition of sand grains foraminiferal assemblages and the composition of sand grains indicate that the upper middle slope 1000 m water depth is the source of the turbidites the deep sea origin of the turbidites is consistent with the hypothesis that they were derived from slope failures initiated by strong shaking associated with earthquake events the recurrence intervals of turbidite deposition are 113 439 yr for events that occurred over the past 7 kyr the short intervals are recorded in the cores obtained from levees on the middle fan although many large earthquakes 150 cm s 2 of peak ground acceleration at the inferred slump sources occurred during the 19th and 20th centuries the pilot core from the upper fan contains only three turbidites located stratigraphically above layers of 17th century volcanic ash the results of 210pbex and 137cs dating combined with simulations of the ground accelerations of historical earthquakes enable correlation of the three turbidites with known historical earthquakes the 1952 tokachi oki and the 1961 and 1973 nemuro oki earthquakes the turbidites within the sampled cores potentially record about half of the large earthquakes known to have occurred over the interval covered by the cores the fact that any single core records only a portion of the known seismic events suggests that the recurrence interval of earthquakes in this region is less than 113 yr during holocene

sedimentary and structural evolution of the eastern south korea plateau eskp east sea japan sea the east sea japan sea is a semi enclosed back arc basin that is thought to preserve a significant record of tectonic evolution and paleo climatic changes of eastern asia during the neogene we use here 2 d regional multi channel seismic reflection profiles and borehole data from expedition 346 of the integrated ocean drilling program iodp to provide new constraints on the geological history of the eastern south korea plateau eskp the eskp represents a structurally complex basement high in the southwestern east sea which formed during rifting of the back arc basin our new observations show that the eskp is composed of numerous horsts and grabens controlled by ne trending normal faults the acoustic basement is blanketed by oligocene to recent sediments that have preferentially accumulated in topographic lows up to 1 5 km thick and have been cored during expedition 346 at site u1430 close to the southern margin of the eskp seismic profiles in the eskp reveal three units separated by regional unconformities these seismic units closely correspond to iodp lithostratigraphic units defined at site u1430 where biostratigraphic data can be used to constrain the timing of three main evolutionary stages of the eskp stage 1 was related to rifting in the late oligocene and middle miocene terminated by a regional uplift leading to an erosional phase in the middle miocene stage 2 was associated with subsidence in the middle and late miocene and uplift and accompanying erosion or non deposition in the latest late miocene stage 3 pliocene to present recorded overall uniform hemipelagic pelagic subsidence of the eskp with short lived tectonically induced uplifts in the late middle miocene and latest miocene early pliocene the three stages of evolution of the eskp closely correlate to sedimentary changes since the oligocene and suggest a direct control of regional local tectonics on sedimentation patterns in the southwestern east sea with secondary influence of regional climatic and paleo oceanographic processes

the seismic stratigraphic record of lake level fluctuations in lake challa hydrological stability and change in equatorial east africa over the last 140 kyr abstract seismic reflection data from crater lake challa mt kilimanjaro equatorial east africa reveal a 210 m thick sedimentary infill containing distinct seismic stratigraphic signatures of late quaternary lake level fluctuations extrapolation of a well constrained age model on the cored upper part of the sequence suggests that these lake level fluctuations represent a detailed and continuous record of moisture balance variation in equatorial east africa over the last 140 kyr this record indicates that the most severe aridity occurred during peak penultimate glaciation immediately before 128 kyr bp coeval with heinrich event 11 and during a last interglacial megadrought period between 114 and 97 kyr bp in comparison last glacial maximum lgm aridity was modest it was preceded by 75 000 years of relatively stable and moist climate conditions interrupted by eleven short lived dry spells five of which match the timing of heinrich events 2 to 6 climate history near the east african equator reflects variation in the precessional forcing of monsoon rainfall modulated by orbital eccentricity but precession driven moisture fluctuations were less extreme than those observed in northern and southern tropical africa the near continuous moist climate from 97 to 20 5 kyr bp recorded in the lake challa record contrasts with the trend towards greater aridity after 70 kyr bp documented in equatorial west africa this long period of moist glacial climate and a short relatively modest lgm drought can be attributed to greater independence of western indian ocean monsoon dynamics from northern high latitude glaciation than those in the tropical atlantic ocean this rather persistent moist glacial climate regime may have helped maintain high biodiversity in the tropical forest ecosystems of the eastern arc mountains in tanzania

early diagenetic redistribution and burial of phosphorus in the sediments of the southwestern east sea japan sea this study was carried out in order to understand the early diagenetic redistribution of phosphorus and relevant mass balance in the sediments of the east sea in two cruises during may 1993 and october 1995 11 box cores were collected in the southwestern part of the east sea dissolved phosphorus and iron were analyzed in the porewater from the cores sediment samples were analyzed for solid phase p species and solid phase fe oxyhydroxide by sequential extraction phosphorus speciation results show that organic p is the major chemical form of phosphorus in young sediments within the upper 50 cm of sediment however the authigenic fraction of total p increases with depth indicating the precipitation of carbonate fluorapatite cfa in the sediments the authigenic cfa ca5 po4 2 6 co3 0 4f was formed and buried at rates of 11 110 mol cm 2 kyr 1 the main source of dissolved phosphorus for the precipitation of cfa is organic p dissolved phosphorus released from the decomposition of organic p diffuses upward to return to bottom water or is sorbed to iron oxides in the oxidized sediments as sedimentation proceeds the iron oxide bound p is released in the reduced layer and enters the dissolved phase which contributes p to the formation of cfa in addition to that contributed by the organic p the burial flux of reactive p iron oxide bound p authigenic p organic p is 0 09 0 53 g p m 2 yr 1 that accounts for 18 58 of the reactive p arriving at the sediment water interface the burial flux of reactive p is high in the upper and lower continental margin sediment the burial flux of reactive p in the ulleung basin sediment is less than those in the continental margin sites by a factor of 6 indicating that the reactive p burial flux is mainly dependent on sedimentation rate

physical properties and geoacoustic provinces of surficial sediments in the southwestern part of the ulleung basin in the east sea abstract a total of 157 piston and box core samples were collected and analyzed to characterize physical properties and geoacoustic provinces of surficial sediments in the southwestern part of the ulleung basin in the east sea the results and distribution patterns of surficial sediment texture physical and acoustic properties reflect well the sedimentary environment like distribution and composition of sediment in the study area the inner shelf and basin slope in this study are dominated by fine grained sediments and show high porosity and water content with low bulk density and velocity as well the trough of the korea strait and outer shelf which is composed of coarse grained sediments shows low porosity and water content and high bulk density and velocity based on in situ velocity and sediment properties the study area is divided into five provinces 1 province ia is hemi pelagic mud partially mixed with intermittent sandy sediments which are derived from the outer shelf due to slide slump or mass flows in situ velocity 1445 m s mean grain size 8 4 porosity 84 and bulk density 1 24 g cm3 2 province ib is covered with muddy sediments that were deposited during the holocene in situ velocity 1445 m s mean grain size 7 9 porosity 78 and bulk density 1 35 g cm3 3 province ii is marked by mixed recent and relict sediments in situ velocity 1477 m s mean grain size 6 1 porosity 68 and bulk density 1 53 g cm3 4 province iii is dominated by coarse grained relict sediments formed during the pleistocene in situ velocity 1564 m s mean grain size 3 8 porosity 54 and bulk density 1 77 g cm3 and 5 province iv consists of coarser sediments than province iii in situ velocity 1671 m s mean grain size 3 0 porosity 46 and bulk density 1 91 g cm3 the compressional wave velocity mean grain size and bulk density increase from province ia to province iv whereas the porosity and water content decrease from province ia to province iv variability of the physical and acoustic properties tends to follow the general trend of the mean grain size the classification of each province using the in situ velocity corrected with the temperature and pressure provides a better reflection of the sediment properties and sedimentary environment

surface water changes recorded in late quaternary marine sediments of the ulleung basin east sea japan sea abstract in order to reconstruct past sea surface temperature sst and salinity sss in the east sea japan sea this study investigated the oxygen isotopic composition of the planktonic foraminifer globigerina bulloides and the degree of unsaturation of alkenones in bulk sediments of core ty99pc18 recovered from the southeastern part of the ulleung basin east sea between 11 and 15 cal kyr bp the surface waters were 2 4 c cooler than today the surface salinity was 12 lower during 14 15 cal kyr bp than today then increased after 14 cal kyr bp but remained lower during 11 14 cal kyr bp than present values between 14 and 15 cal kyr bp the northern east china sea surface waters were likely to be greatly diluted by fresh water discharge from land and coastal waters would have flowed into the east sea through the korea strait during 11 14 cal kyr bp the southern input waters most likely changed from fresh water influenced coastal water to open ocean water the increased salinity probably enhanced active deep water convection at that time during 7 11 cal kyr bp the surface waters were warmer 1 c and more saline 1 3 than today indicating that the warm and saline kuroshio current became stronger and that one of its branches flowed into the east sea during this time interval the cold 2 c and less saline waters 1 at 3 6 cal kyr bp may indicate a suppression of the kuroshio current the sst and sss values are close to the present values at about 3 cal kyr bp suggesting that the physiological conditions of the east sea approached that of the present at this time

alternative modes of quaternary pelagic biosiliceous and carbonate sedimentation a perspective from the east sea japan sea abstract six piston cores 95pc 1 mb97pc 19 ty99 pc18 95pc 3 95pc 4 and 96ebp 4 from the east sea japan sea were examined to assess the fluctuations in carbonate and biogenic silica sedimentation data from four of these cores 95pc 1 mb97pc 19 ty99 pc18 and 96ebp 4 collected from depths above the present carbonate compensation depth ccd clearly show that carbonate content increased during glacial periods and decreased during interglacial periods whereas biogenic silica content shows the opposite pattern the two cores collected below the ccd also show glacial interglacial variations in carbonate and biogenic opal contents with patterns similar to the cores collected above the ccd this study provides strong evidence for cyclic variations of biogenic components corresponding to interglacial glacial cycles even though variations in carbonate and opal contents seem to be affected by dissolution and dilution the inverse correlation between carbonate and biogenic silica contents suggests that two mutually exclusive oceanic modes affected the biogenic sedimentation these modes may have resulted from sea level changes that led to water column stratification during glacial low stands and breakdown of water column stratification and consequent active vertical mixing during interglacial high stands

geotechnical characteristics and slope stability on the ebro margin western mediterranean abstract sedimentological and geotechnical analyses of core samples from the ebro continental slope define two distinct areas on the basis of sediment type physical properties and geotechnical behavior the first area is the upper slope area water depths of 200 500 m which consists of upper pleistocene prodeltaic silty clay with a low water content 34 dry weight average low plasticity and high overconsolidation near the seafloor the second area the middle and lower slope water depths greater than 500 m contains clay and silt size hemipelagic deposits with a high water content 90 average high plasticity and a low to moderate degree of overconsolidation near the sediment surface results from geotechnical tests show that the upper slope has a relatively high degree of stability under relatively rapid undrained static loading conditions compared with the middle and lower slopes which have a higher degree of stability under long term drained static loading conditions under cyclic loading which occurs during earthquakes the upper slope has a higher degree of stability than the middle and lower slopes for the surface of the seafloor calculated critical earthquake accelerations that can trigger slope failures range from 0 73 g on the upper slope to 0 23 g on the lower slope sediment buried well below the seafloor may have a critical acceleration as low as 0 09 g on the upper slope and 0 17 g on the lower slope seismically induced instability of most of the ebro slope seems unlikely given that an earthquake shaking of at least intensity vi would be needed and such strong intensities have never been recorded in the last 70 years other cyclic loading events such as storms or internal waves do not appear to be direct causes of instability at present infrequent particularly strong earthquakes could cause landslides on the ebro margin slope the columbretes slide on the southwestern ebro margin may have been caused by intense earthquake shaking associated with volcanic emplacement of the columbretes islands localized sediment slides on steep canyon and levee slopes could have been caused by less intense shaking in general the slope is stable under present environmental loading conditions and is fundamentally constructional nevertheless rapid progradation caused by high sedimentation rates and other processes acting during low sea level periods such as more intense wave loading near the shelfbreak may have caused major instability in the past

sediment failure and sedimentary framework of the wilmington geotechnical corridor u s atlantic continental margin abstract seaward of new jersey and the baltimore canyon trough a 7500 km2 corridor across the continental margin was studied in detail using geotechnical and geophysical techniques the objective of the study was to identify the sedimentary pattern and bottom processes which have occurred and are active on the continental margin delineation of a mid pliocene unconformity present throughout most of the corridor permits an evaluation of the quaternary sedimentation pattern and its variability sediment failure characterized by large slide blocks and thin layer slide deposits was found on the continental slope and rise within the quaternary sediments spencer and wilmington submarine canyons have been active in channeling large volumes of sediment to the lower slope and rise an increase in sediment thickness near wilmington canyon indicates the importance and activity of the delaware bay drainage system during the pleistocene although both spencer and wilmington are as old as late tertiary the wilmington valley on the lower slope and rise is a recent topographic feature based on geophysical data the numerous valleys that dissect the continental slope and rise appear to be active periodically in the seaward transport of sediment to the deep sea

thermal enhancement of magnetic fabrics in high grade gneisses the orientation distributions of ams and aarm ellipsoids are non coaxial in the kapuskasing zone granulites aarm is due to the preferred orientation of magnetite which mostly postdates the silicate fabric the ams orientation distribution combines susceptibility anisotropies of magnetite and the silicates whereas heating does not increase the bulk susceptibility it does improve the definition of the orientation distributions of both ams and aarm however the orientation distribution of aarm is most enhanced and therefore post heated samples emphasize the magnetite sub fabric thus heating does not clarify the interpretation of the silicate fabric in this study however it does change the samples ams fabric in such a way as to reveal the magnetite subfabric which can only otherwise be detected by more tedious aarm measurements

seismicity based earthquake forecasting techniques ten years of progress abstract earthquake fault systems interact over a broad spectrum of spatial and temporal scales and in recent years studies of the regional seismicity in a variety of regions have produced a number of new techniques for seismicity based earthquake forecasting while a wide variety of physical assumptions and statistical approaches are incorporated into the various methodologies they all endeavor to accurately replicate the statistics and properties of both the historic and instrumental seismic records as a result the last ten years have seen significant progress in the field of intermediate and short term seismicity based earthquake forecasting these include general agreement on the need for prospective testing and successful attempts to standardize both evaluation methods and the appropriate null hypotheses here we differentiate the predominant approaches into models based upon techniques for identifying particular physical processes and those that filter or smooth the seismicity comparison of the methods suggests that while smoothed seismicity models provide improved forecast capability over longer time periods higher probability gain over shorter time periods is achieved with methods that integrate statistical techniques with our knowledge of the physical process such as the epidemic type aftershock sequence etas model or those related to changes in the b value for example in general while both classes of seismicity based forecasts are limited by the relatively short time period available for the instrumental catalog significant advances have been made in our understanding of both the limitations and potential of seismicity based earthquake forecasting there is general agreement that both short term forecasting on the order of days to weeks and longer term forecasting over five to ten year periods is within reach this recent progress serves to illuminate both the critical nature of the different temporal scales intrinsic to the earthquake process and the importance of high quality seismic data for the accurate quantification of time dependent earthquake hazard

sediment failure on the korea plateau slope east sea sea of japan abstract high resolution 3 5 khz seismic profiles from the slope of the korea plateau east sea sea of japan show an extensive area of slide deposits with prominent slump scars the sediment displaced from the steep slope 5 7 is less expansive than massive failure deposits on gradual slopes 1 2 seaward of a large trough thick wavy stratified sediments cover the gentle slope cyclic loading by earthquakes is the most probable triggering mechanism for the slope instability in this area the topmost 2 3 m sediment is chiefly composed of hemipelagic mud with interbeds of turbidites and volcanogenic material these sediments are highly plastic and shear resistant over 4 kpa at the surface in both stable and failed areas grain size decreases seaward from sandy mud on the shelf to silty clay on the lower slope total organic matter and water contents are closely associated with sediment texture both increasing with clay amounts from 5 10 and from 50 up to 200 respectively

characteristics of the late quaternary tephra layers in the east japan sea and their new occurrences in western ulleung basin sediments abstract the lithologic characteristics stratigraphic relationships and areal distribution of late quaternary tephra layers have been determined based on four piston cores recovered from the western ulleung basin of east japan sea the results show that using morphological and major element compositional data volcanic glass shards dispersed in tephra layers are identical to those of fallout deposits of the ulleung oki ca 9 3 ka aira tanzawa ca 22 ka and ulleung yamato ca 33 ka the lapilli tephra layers ulleung oki and ulleung yamato originating from ulleung island consist predominantly of pumice type glass shards associated with minor amounts of alkali feldspar biotite and plagioclase on the other hand the ash layers including the aira tanzawa ash derived from the japanese islands are mainly composed of bubble wall and or plane type glasses that contain higher sio 2 and lower al 2 o 3 than the lapilli tephra layers the occurrence of tephra layers in the western ulleung basin and their stratigraphic correlation extend the distribution of pumice type glass shards about 50 100 km west of the previously known fallout zone

seismic reflection study of acoustic basement in the south korea plateau the ulleung interplain gap and the northern ulleung basin volcano tectonic implications for tertiary back arc evolution in the southern east sea abstract in order to understand the volcano tectonic evolution history of the east sea back arc basin this study focuses on the seismic characteristics of acoustic basement based on the multi channel seismic reflection data acquired from the south korea plateau the northern ulleung basin and the ulleung interplain gap according to the seismic reflection characteristics the acoustic basement in the study area can be classified into three types type a acoustic basement is a remnant of rifted continental crust comprising relatively shallow seated continental margin platforms elongated ridges and equidimensional blocks in the south korea plateau and its vicinities type b acoustic basement is volcanic sills flows sediments complexes infilling the rift controlled basement lows in the south korea plateau the ulleung interplain gap and the northern ulleung basin type c acoustic basement is a cluster or chain of volcanic edifices which shows internal facies variation from main body to apron slope facies volcanic activities identified in the types b and c acoustic basements can be classified into three stages based on the volcano stratigraphic correlation with the existing stratigraphic framework stage 1 volcanism is characterized by a fissure type eruption represented by scattering volcanic cones and mounds type c and volcanic sills and lava flows interlayering with syn rift sedimentary units type b early stage continental rifting prior to the middle miocene most likely controlled this volcanism stage 2 volcanism is characterized by ene wsw trending chain of volcanic edifices type c along the northern margin of the ulleung basin and ulleung interplain gap during the middle miocene the weakening of back arc extension might have resulted in limited volcanic eruption which formed elongate volcanic fields across the ulleung and yamato basins stage 3 volcanism is represented by highly peaked volcanic islands and seamounts type c showing vertically stacked apron slopes in seismic cross sections this vertical stacking pattern is indicative of multiple eruption events from a single eruption center at least from the late miocene to the quaternary expanded volcanic age control based on volcano stratigraphic and isotopic age dating reveals that the volcanic activities in the southwestern and southeastern east sea show similar spatio temporal variations this implies that the entire southern east sea has experienced almost same volcano tectonic evolution during the cenozoic back arc evolution especially the stage 2 volcanic chain along the northern ulleung basin and the yamato seamount chain in the yamato basin matches in their eruption timing ca 12 ma and geomorphic properties i e direction of the volcanic chains and distances from subduction zone which strongly suggests the existence of regional scale chain volcanism across the southern east sea considering the chemical properties of volcanic rock samples from the volcanic chain in association with the suggested tectonic frameworks during the tertiary the remnant magma source derived from the waning mantle convection most likely fed the volcanic chain in the terminal stage of back arc opening

paleoceanographic changes in the ulleung basin east japan sea during the last 20 000 years evidence from variations in element composition of core sediments a millennial scale paleoceanographic record of the ulleung basin in the southern part of the east japan sea es for the last 20 000 years was reconstructed based on variations in the element compositions of core sediment most of the elements showed relatively wide content ranges throughout the core largely because of different sediment types their grain size spectra biological components and geochemical conditions i e redox conditions in particular biogenic components ca sr ba and caco 3 and some minor elements cu mn mo u cd zn and v revealed three distinct intervals of major paleoceanographic changes interval 1 similar to 18 9 3 kyr bp is characterized by a rhythmic alternation of dark and light colored sediment bands distinctive differences in the abundance of organic carbon carbonate and redox elements between the dark and light colored sediment layers are probably attributable to especially those associated with bottom water redox variations combined with the enhanced primary productivity and water stratification in the ulleung basin

geochemical identification of cryptotephras using inaa from late quaternary hemipelagic sediments southwest japan abstract we present new compositional data on glass shards from cryptotephra layers in five marine sediment cores from the southern japan east sea the hand picked glass shards were extracted from cryptotephra horizons that were distinguished by sem eds for major elements and inaa for trace elements on individual shards most of the glass shards have alkaline and trachyte phonolite compositions and have major and trace element compositions similar to eruptive units on ulleung island stratigraphic inferences indicate the presence of at least four alkaline tephras u 3 post u oki u oki and pre u oki in the interval between the k ah rhyolitic tephra 7 3 cal ka bp and the tl1 regional dark sediment layer 11 8 cal ka bp the new trace elements on glass shards indicate minor compositional distinctions from one visible tephra and four cryptotephras that help to infer fine scale regional correlations the development of a more comprehensive alkaline tephrostratigraphical framework for this region will greatly aid in the reconstruction and chronology of regional stratigraphic variations the recognition of new alkaline cryptotephras in the marine sediments of the japan east sea also contributes towards a better understanding of the volcanic history of ulleung island and nearby seamounts

zoned facies of mass flow deposits in the ulleung tsushima basin east sea sea of japan abstract high resolution 3 5 khz reflection profiles in the ulleung tsushima basin made it possible to classify the uppermost ca 50 m thick sedimentary deposits into rock fall slide slump debris flow deposit debrite and turbidite in terms of their acoustic properties these deposits generally occur in a distinctive zonal facies slides and slumps on the slope debrites on the base of slope and turbidites on the basin floor the rock fall deposits occur along the bases of the korea plateau and ulleung and dok islands the zonal distribution of mass flow deposits suggests that they most likely are derived from a line source at the shelfbreak shelf sediments prograde toward the shelfbreak on the slope sediment masses move downslope mainly accompanied by progressive slumping upslope individual slides and slumps on the slope probably develop into debris flows on the base of slope and successively into turbidity currents on the basin floor mass flow processes on the ulleung basin slope played an important role in transporting a large volume of terrigenous sediments into the deep basin

paleomagnetism of the upper proterozoic and devonian rocks from the klodzko metamorphic complex in the west sudetes sw poland tectonic implications for the variscan belt of central europe abstract the klodzko metamorphic complex kmc consists of upper proterozoic metaigneous and metasedimentary rocks forming a stack pile thrusted over the givetian and overlain by frasnian fammenian sediments magnetomineralogical experiments show that the magnetic minerals are secondary the paleomagnetic experiments identified three components of the natural remanent magnetization labeled a1 a2 and m the mean pole positions calculated in situ correspond with the baltica upper devonian a1 plats 18 plonge 317 permo carboniferous a2 plats 39 plonge 2 and triassic jurassic m plats 60 c plonge 308 segments of the apparent polar wander path apwp for baltica this indicates that the region studied was situated close to the baltica plate at least since the upper devonian and was not folded after this period

intermediate term earthquake prediction in the area of greece application of the algorithm m8 the 3 strongest earthquakes m 7 0 which have occurred since 1973 in the area of greece were preceded by a specific increase of the earthquake activity in the lower magnitude range this activation is depicted by algorithm m8 this algorithm of intermediate term earthquake prediction was originally designed for diagnosis by times of increased probability tips of the strongest earthquake m 8 0 worldwide keilis borok andkossobokov 1984 at present the algorithm is retrospectively tested for smaller magnitudes in different seismic regions keilis borok andkossobokov 1986 1988 a tip refers to a time period of 5 years and an area whose linear size is proportional and several times larger than that of the incipient earthquake source altogether the tips diagnosed by the algorithm m8 in the area of greece occupy less than 20 and the times of expectation tes about 10 of the total space time domain considered also there is a current tip for the southeastern aegean sea and 1988 1992 it may specify the long term prediction given inwyss andbaer 1981a b

on the significance of sea level variations and shelf paleo morphology in governing sedimentation in the southern south china sea during the last deglaciation abstract deglacial sedimentation on the outer sunda shelf the shelf margin and slope shows a close correlation with the stages of flooding of the emerged shelf it is mainly controlled by the relationship between shelf paleo physiography and changes in sea level and sediment supply based on the sedimentological and geochemical variability at five sites along a transect across the outer shelf and the continental slope covering the last 20 000 years four intervals of significant depositional changes are identified the first reorganization in the sedimentation regime which was established during sea level lowstand is associated with the drowning of the lower course of the north sunda river between 16 5 and 14 5 ka during and following the rapid rise in sea level at 14 5 14 ka sedimentation on the slope is characterized by an accelerated decrease in the supply of terrigenous material associated with the flooding of the middle part of the paleo valley this abrupt change in sedimentation is followed by a period of gradual decrease of terrigenous supply to the slope when the surrounding plains of the river valley were flooded 14 8 5 ka the final change occurred between ca 8 5 and 6 ka when the coastline reached its modern position and modern sedimentary patterns are established this change probably marks the end of reworking by transgression given the synchroneity of sedimentological changes along the transect across the sunda shelf and into the deep sea with the environmental shifts on the central shelf sedimentation on the margin and slope appears to be mainly controlled by the interrelationship of sea level shelf paleo physiography and sediment supply moreover the records display lateral changes through time associated with stages of the deglacial transgression which mask any potential sedimentological variability due to changes in precipitation vegetation or atmospheric circulation this fact cautions the interpretation of near shore sedimentary records as unequivocal recorders of local climate change e g se asian monsoon and highlights the need to include variations in shelf physiography and sea level in future paleoceanographic studies

gas hydrates on the northern california continental margin the inner continental margin of northern california is underlain by a well defined and extensive acoustic reflector that crosses other reflectors and mimics the surface of the sea floor this bottom simulating reflector bsr lies at a typical subsurface depth of about 250 m and has been mapped continuously beneath the klamath plateau and upper slope water depths of 800 to 1200 m for a distance of more than 130 km it covers an area of at least 3000 km 2 limited data show that the bsr extends northward into oregon and seaward at least to the base of the slope 3000 m the water depths subsurface depths and pervasive nature of the bsr all suggest that it represents the base of a natural gas hydrate using standard phase boundary diagrams for hydrate stability we estimate the local geothermal gradient within the gas hydrate to be about 55 c km this value is higher than that of most subduction margins and may be a result of the youthfulness of the subducting oceanic crust this acoustically inferred gas hydrate is the first to be mapped on the western conterminous united states continental margin

toward establishing precise 40ar 39ar chronologies for late pleistocene palaeoclimate archives an example from the lake suigetsu japan sedimentary record the varved suigetsu sg06 sediment core is potentially one of the most important and well constrained mid latitude palaeoclimate archives recording continuous deposition during the last 150 kyrs numerous visible and non visible volcanic ash layers form unique age markers within sg06 these ash layers are too fine and crystal poor to be directly dated using the 40ar 39ar technique so the tephra were correlated to proximal volcanic deposits using their glass shard compositions a high precision 40ar 39ar sanidine age of 10 0 0 3 ka 1 n 34 mswd 0 71 p 0 89 was obtained for the sg06 1288 u oki proximal tephra ulleungdo u4 40ar 39ar yields a precision of 3 near the younger limit of the method with improved precision possible for older sg06 samples such 40ar 39ar ages for tephra layers can provide invaluable tie points within the lake suigetsu sg06 sequence giving independent verification of the core s varve chronology allowing for the calibration of cosmogenic nuclide production and providing a precise chronology beyond the varve limit

late quaternary tephrostratigraphy of baegdusan and ulleung volcanoes using marine sediments in the japan sea east sea abstract only ulleung and baegdusan volcanoes have produced alkaline tephras in the japan sea east sea during the quaternary little is known about their detailed tephrostratigraphy except for the u oki and b tm tephras trace element analysis of bulk sediments can be used to identify alkaline cryptotephra because of the large compositional contrast five sediment cores spanning the interval between the rhyolitic at 29 4 ka and aso 4 87 ka tephras were analyzed using an inaa scanning method source volcanoes for the five detected alkaline cryptotephra were identified from major element analyses of hand picked glass shards ulleung u ym and the newly identified u sado and baegdusan b j and the newly identified b sado and b ym the eruption ages of the u ym u sado b j b sado and b ym tephras are estimated to be 38 ka 61 ka 26 ka 51 ka 68 69 ka and 86 ka respectively based on correlations with regional scale tl thinly laminated layer stratigraphy produced by basin wide changes in bottom water oxygen levels in response to millennium scale paleoclimate variations this study has allowed construction of an alkaline tephrostratigraphical framework for the late quaternary linked to global environmental changes in the japan sea east sea and improves our knowledge of the eruptive histories of ulleung and baegdusan volcanoes

times of increased probability of earthquakes of ml 5 5 in greece diagnosed by algorithm m8 an attempt is made to explore the possibility of identifying the times of increased probability tips of occurrence of earthquakes with ml 5 5 by premonitory intermediate term seismic activation in lower magnitude ranges as defined in the algorithm m8 a tip refers to a 5 year period and an area whose length is several times greater than that of an incipient earthquake this algorithm has been already tested retrospectively for the strongest earthquakes of magnitude greater than or equal to 7 0 which have occurred in greece since 1973 in the present study the same algorithm is also applied retrospectively by considering smaller earthquakes of local magnitude ml greater than or equal to 5 5 the obtained results show that ten out of eleven events with m 5 5 which took place in greece and surrounding region from january 1 1977 till december 31 1990 occurred within the tips diagnosed by the algorithm m8 retrospectively only the thessaloniki earthquake of june 20 1978 did not occur within tip the m8 algorithm failed in four cases namely those that occurred in regions for which our catalogue was not complete altogether the tips occupy less than 25 and times expectation about 8 of the total space time considered there is also a current tip started at the end of 1986 or at the beginning of 1987 for the south southwestern part of thehellenic arc indicating that this area deserves particular attention if the algorithm m8 works reliably then this tip will be filled by the end of 1992 this result by no means constitute the definitive earthquake prediction but merely outline a territory for more detailed and comprehensive analysis

dependence of anisotropy of magnetic susceptibility of rocks on temperature abstract the influence of heating on the low field magnetic susceptibility k and its anisotropy ams has been studied in some sedimentary igneous and metamorphic rocks the results show that heating causes a better grouping of the anisotropy ellipsoid axes especially in sediments in all the rocks studied the ams is mainly due to the matrix i e paramagnetic and diamagnetic minerals rather than the ferromagnetic minerals the ams of the diamagnetic components is removed during heating an experiment involving thermal remagnetization of one sediment sample indicates that the processes of thermal magnetization do not influence the directions of anisotropy axes in this rock

provenance of late quaternary sediments on the southwestern slope of the ulleung basin east japan sea the provenance of fine grained sediments deposited since the late quaternary was recovered from drill site ubgh2 1 1 on the southwestern slope of the ulleung basin east japan sea based on geochemical analyses including rare earth elements rees the fine grained sediments could be interpreted as mixtures of sediments from china via various pathways and sediments discharged from the nakdong river nrs a comparison of variations in ree fractionation factor with marine isotope stages miss indicated that the provenance of the fine grained sediments on the southwestern slope of the ulleung basin was controlled by global eustatic sea level change during glacial periods most of the fine grained sediments were supplied via the atmospheric pathway by an intensified east asian winter monsoon and sediments from chinese rivers crs transported into the ulleung basin through the korea strait were limited due to the morphological characteristics of the korea strait and low sea level during interglacial periods the crs transported into the ulleung basin through the korea strait increased with sea level rise and eolian dust inputs decreased due to attenuated east asian winter monsoon simultaneously nrs also should have been deposited when sea level was higher than 40 m relative to present sea level during mis 1 and mis 5 in particular during mis 1 signals of nrs were revealed since 11 ka thus it can be suggested that the present coastal current system around the southeastern coast of korea became established by around 11 ka

slope stability and geotechnical properties of sediment of the southern margin of ulleung basin east sea sea of japan abstract ulleung basin a deep back arc basin in the sea of japan is tectonically active in relation to the subduction zone fronting the japanese islands cores and high resolution 3 5 khz seismic profiles were obtained from the southern margin of the basin based on the results of geotechnical tests pseudo static infinite slope stability analyses were carried out for the surficial slope sediments the shelf sediments are mostly massive medium to fine sand whereas the slope sediments are strongly bioturbated waterrich 170 200 water content and highly plastic 125 135 liquid limit 70 80 plasticity index silty clays these hemipelagic muds are slightly overconsolidated and highly compressible most geotechnical properties show distinctive downslope variations the amount of clay fraction water content and atterberg limits gradually increase downslope whereas calcium carbonate content decreases from 5 on the upper slope to nearly nil on the lower slope 1500 m total organic matter is somewhat consistent 8 14 throughout the slope shear strength displays no systematic variations downslope but gradually increases downcore in most places seismic data indicate that the slope surface is heavily moulded by mass movements a complex system of gullies and slump scars begins at the upper slope extending to the lower slope as slide slump and debris flow deposits the surficial sediments on the entire slope are quite stable statically under both undrained and drained conditions at present they appear to be least susceptible to slope failure by any probable earthquake loading associated with the regionally active tectonic regime

seismic quiescence in the western hellenic arc may foreshadow large earthquakes south of crete the seismicity rate was constant in space and time between 1950 and 1978 but in the western hellenic trench the rate was the same as that south of crete until 1962 whereupon it decreased by 80 we now suggest that the anomaly constitutes a warning of large earthquakes within the coming decade

correlating tephras and cryptotephras using glass compositional analyses and numerical and statistical methods review and evaluation abstract we define tephras and cryptotephras and their components mainly ash sized particles of glass crystals in distal deposits and summarize the basis of tephrochronology as a chronostratigraphic correlational and dating tool for palaeoenvironmental geological and archaeological research we then document and appraise recent advances in analytical methods used to determine the major minor and trace elements of individual glass shards from tephra or cryptotephra deposits to aid their correlation and application protocols developed recently for the electron probe microanalysis of major elements in individual glass shards help to improve data quality and standardize reporting procedures a narrow electron beam diameter 3 5 m can now be used to analyze smaller glass shards than previously attainable reliable analyses of microshards defined here as glass shards in part 2 of the review we describe critically assess and recommend ways in which tephras or cryptotephras can be correlated in conjunction with other information using numerical or statistical analyses of compositional data statistical methods provide a less subjective means of dealing with analytical data pertaining to tephra components usually glass or crystals phenocrysts than heuristic alternatives they enable a better understanding of relationships among the data from multiple viewpoints to be developed and help quantify the degree of uncertainty in establishing correlations in common with other scientific hypothesis testing it is easier to infer using such analysis that two or more tephras are different rather than the same adding stratigraphic chronological spatial or palaeoenvironmental data i e multiple criteria is usually necessary and allows for more robust correlations to be made a two stage approach is useful the first focussed on differences in the mean composition of samples or their range which can be visualised graphically via scatterplot matrices or bivariate plots coupled with the use of statistical tools such as distance measures similarity coefficients hierarchical cluster analysis informed by distance measures or similarity or cophenetic coefficients and principal components analysis pca some statistical methods cluster analysis discriminant analysis are referred to as machine learning in the computing literature the second stage examines sample variance and the degree of compositional similarity so that sample equivalence or otherwise can be established on a statistical basis this stage may involve discriminant function analysis dfa support vector machines svms canonical variates analysis cva and anova or manova or its two sample special case the hotelling two sample t2 test randomization tests can be used where distributional assumptions such as multivariate normality underlying parametric tests are doubtful compositional data may be transformed and scaled before being subjected to multivariate statistical procedures including calculation of distance matrices hierarchical cluster analysis and pca such transformations may make the assumption of multivariate normality more appropriate a sequential procedure using mahalanobis distance and the hotelling two sample t2 test is illustrated using glass major element data from trachytic to phonolitic kenyan tephras all these methods require a broad range of high quality compositional data which can be used to compare unknowns with reference training sets that are sufficiently complete to account for all possible correlatives including tephras with heterogeneous glasses that contain multiple compositional groups currently incomplete databases are tending to limit correlation efficacy the development of an open online global database to facilitate progress towards integrated high quality tephrostratigraphic frameworks for different regions is encouraged

identification of the late quaternary tephra layers in the ulleung basin of the east sea using geochemical and statistical methods abstract the late quaternary tephra layers discovered in piston cores from the ulleung basin of the east sea sea of japan were studied using x ray fluorescence spectrometry xrf inductively coupled plasma atomic emission icp aes and inductively coupled plasma mass spectrometer icp ms in order to identify and differentiate the tephra layers and to characterize their major and trace element compositions the morphology and geochemistry of glass shards combined with 14c dating and statistical methods confirm the ulleung and aira tanzawa eruptions as the origin of the tephra layers respectively the so called ulleung oki u oki 10 1 cal ka and ulleung yamato u ym 30 9 cal ka tephra layers consist predominantly of pumice type glass shards in contrast the aira tanzawa at 23 cal ka tephra layer consists mainly of plane type and or bubble wall glass shards the u oki and u ym tephra layers contain k rich glasses r k2o sio2 0 09 ranging from phonolitic to trachytic alkali compositions whereas the at tephra layer which contains k poor glasses r ca 0 04 is rhyolitic according to trace element content the relative amounts of the elements ti zr y nb and p from the tephra layers evidently indicate the different tectonic zones between the ulleung back arc and kyushu island arc islands especially the relatively depleted concentrations of feo v co and ni in the u oki tephra layer most likely reflect more fractional crystallization of olivine pyroxene hornblende and magnetite than those in the u ym tephra layer

geotechnical characterization of marine sediments in the ulleung basin east sea the geotechnical characteristics of ulleung basin sediments are explored using depressurized samples obtained at 2100 m water depth and 110 m below the sea floor geotechnical index tests x ray diffraction and sem images were obtained to identify the governing sediment parameters chemical composition and mineralogy we use an instrumented multi sensor oedometer cell to determine the small strain stiffness zero lateral strain compressibility and electromagnetic properties and a triaxial device to measure shear strength sem images show a sediment structure dominated by microfossils with some clay minerals that include kaolinite illite and chlorite the preponderant presence of microfossils determines the high porosity of these sediments defines their microstructure and governs all macroscale properties the shear wave velocity increases as the vertical effective stress increases on the other hand porosity permittivity electrical conductivity and hydraulic conductivity decrease with increasing confinement all these parameters exhibit a bi linear response with effective vertical stress due to the crushable nature of microfossils well established empirical correlations used to evaluate engineering parameters do not apply for these diatomaceous sediments which exhibit higher compressibility than anticipated based on correlations with index properties settlements will be particularly important if gas production is attempted using depressurization because this approach will cause both hydrate dissociation and increase in effective stress

an optimization of using the m8 algorithm for prediction of major m7 0 earthquakes in the iranian plateau the casualties and financial losses caused by large earthquakes have led to an awareness of prediction importance of such earthquakes the earthquake prediction is divided into four categories long term intermediate term short term and immediate the m8 algorithm is one of the intermediate term middle range prediction algorithms primarily used to predict earthquake of magnitude 8 or more and is applied later for smaller magnitudes the iranian plateau is less exposed to earthquake with magnitude 8 or more and it is observed that the seismicity rate in this region is generally low thus the original m8 is not suitable for applying in this region the objective of this study is to modify the m8 algorithm for prediction of major m7 0 earthquakes in the iranian plateau the major earthquake of magnitude 7 or more in the iranian plateau from 1975 to 2018 is considered as the target earthquakes the hit rate times 1 minus alarm rate is defined as objective function and the particles swarm optimization meta heuristic algorithm is used to maximize it the optimum m8 could predict 14 out of 17 large earthquakes in the iranian plateau while occupying 31 7 of the spatio temporal space as the alarm the results show that by employing an optimization algorithm we can modify the m8 algorithm for efficient prediction of the target magnitudes less than 8 in the regions with low seismicity rate

testing an earthquake prediction algorithm the 2016 new zealand and chile earthquakes the 13 november 2016 m7 8 54 km nne of amberley new zealand and the 25 december 2016 m7 6 42 km sw of puerto quellon chile earthquakes happened outside the area of the on going real time global testing of the intermediate term middle range earthquake prediction algorithm m8 accepted in 1992 for the m7 5 range naturally over the past two decades the level of registration of earthquakes worldwide has grown significantly and by now is sufficient for diagnosis of times of increased probability tips by the m8 algorithm on the entire territory of new zealand and southern chile as far as below 40 s the mid 2016 update of the m8 predictions determines tips in the additional circles of investigation cis where the two earthquakes have happened thus after 50 semiannual updates in the real time prediction mode we 1 confirm statistically approved high confidence of the m8 msc predictions and 2 conclude a possibility of expanding the territory of the global test of the algorithms m8 and msc in an apparently necessary revision of the 1992 settings

age dating and the orbital theory of the ice ages development of a high resolution 0 to 300 000 year chronostratigraphy using the concept of orbital tuning a continuous high resolution deep sea chronostratigraphy has been developed spanning the last 300 000 yr the chronology is developed using a stacked oxygen isotope stratigraphy and four different orbital tuning approaches each of which is based upon a different assumption concerning the response of the orbital signal recorded in the data each approach yields a separate chronology the error measured by the standard deviation about the average of these four results which represents the best chronology has an average magnitude of only 2500 yr this small value indicates that the chronology produced is insensitive to the specific orbital tuning technique used excellent convergence between chronologies developed using each of five different paleoclimatological indicators from a single core is also obtained the resultant chronology is also insensitive to the specific indicator used the error associated with each tuning approach is estimated independently and propagated through to the average result the resulting error estimate is independent of that associated with the degree of convergence and has an average magnitude of 3500 yr in excellent agreement with the 2500 yr estimate transfer of the final chronology to the stacked record leads to an estimated error of 1500 yr thus the final chronology has an average error of 5000 yr