earthquake swarms precursory to moderate to great earthquakes in the northeast india region abstract the northeast india region has seen ten m 7 1 2 earthquakes since 1897 including two great earthquakes of m 8 7 in 1897 and 1950 the last m 7 1 2 earthquake occurred on august 17 1952 with the exception of three earthquakes others are found to be associated with periods of background normal seismicity precursory swarms quiescence and mainshocks and the associated foreshocks and aftershocks the dataset has been critically examined for completeness considering the current capabilities for defining locations and also considering other parameters regression equations relating the mainshock magnitude mm the average magnitude of the largest two events in the swarm mp and the time interval mp between the beginning of the swarm and the mainshock have been developed these are mm 1 37mp 1 41 and mm 3log10tp 3 27 it is important to recognize precursory swarms and quiescence in real time indeed we believe we have recognized one such sequence in the vicinity of the arakan yoma fold belt on the basis of mp and tp values the lateral extent of swarm activity and the fact that no event of m 6 has occurred since 1975 in the preparation zone defined by the 1963 1965 swarm we estimate that an m 8 earthquake could occur at any time in the area bounded by 21 and 25 1 2 n and 93 and 96 e the focal depth of this impending earthquake is estimated to be 100 40 km in view of the focal depths of the other events in the swarm

a penultimate glacial monsoon record from hulu cave and two phase glacial terminations oxygen isotope records of three stalagmites from hulu cave china extend the previous high resolution absolute dated hulu asian monsoon record from the last to the penultimate glacial and deglacial periods the penultimate glacial monsoon broadly follows orbitally induced insolation variations and is punctuated by at least 16 millennial scale events we confirm a weak monsoon interval between 135 5 1 0 and 129 0 1 0 ka prior to the abrupt increase in monsoon intensity at asian monsoon termination ii based on correlations with both marine ice rafted debris and atmospheric ch 4 records we demonstrate that most of marine termination ii the full rise in antarctic temperature and atmospheric co 2 and much of the rise in ch 4 occurred within the weak monsoon interval when the high northern latitudes were probably cold from these relationships and similar relationships observed for termination i we identify a two phase glacial termination process that was probably driven by orbital forcing in both hemispheres affecting the atmospheric hydrological cycle and combined with ice sheet dynamics

the bering and okhotsk seas modern and past paleoceanographic changes and gateway impact abstract the high biological productivity and an efficient biological pumping in the subarctic pacific and adjacent seas make this region important to the modern carbon cycle and both modern and the past climate of the earth knowledge of the northern marginal seas of the pacific however is unsubstantial the bering sea is located between the pacific ocean and the arctic sea and plays an important role in ocean circulation involving balances of heat salt and various chemical properties thus it is necessary to unravel the geologic history of the bering sea as a gateway to the pacific and the arctic atlantic during the last 5 million years and beyond the okhotsk sea is considered a locus of north pacific intermediate water formation today the intermediate water formation is linked with seasonal sea ice cover diatom records from the okhotsk sea demonstrate that sea ice cover was distributed on the western side of the sea and the eastern part was open water during the last glacial maximum this configuration permitted a better ventilation of the glacial okhotsk sea through increased quantity of intermediate water presumably formed there at that time

effect of organic carbon flux and dissolved oxygen on the benthic foraminiferal oxygen index bfoi variations in oceanic primary productivity flux of organic carbon to the sediments and dissolved oxygen levels in the water column are thought to be important in the control of benthic foraminiferal test size wall thickness morphology and species composition of assemblages by many foraminiferal paleontologists aspects of these processes should be reflected by the benthic foraminiferal oxygen index bfoi based on these foraminiferal characteristics however analyses indicate that the bfoi correlates most strongly with dissolved oxygen levels in overlying water r2 0 81 weakly with oceanic primary productivity r2 0 55 and weakly with organic carbon flux to the sediments r2 0 51 although both dissolved oxygen and organic carbon flux are main controlling factors for benthic foraminiferal assemblages the bfoi is a useful indicator extracted from benthic foraminiferal assemblages for estimating the condition of dissolved oxygen in cretaceous and cenozoic oceans

earthquake prediction in northeast india a review a multidimensional geophysical approach is made to study earthquake precursors in northeast india resistivity gravity and seismological precursor anomalies for the two recent damaging earthquakes one on december 30 1984 magnitude 5 8 and the other on august 6 1988 magnitude 7 5 are very encouraging to intensify these studies in the region improved methods of magnetic and geohydrological precursor studies are suggested

last glacial holocene water structure in the southwestern okhotsk sea inferred from radiolarian assemblages abstract in order to reconstruct paleoceanographic conditions in the southwestern sw okhotsk sea radiolarian assemblages were analyzed from 10 surface sediments and 5 sediment cores obtained from various water depths ranging between 461 and 1348 m we also measured geochemical components such as biogenic opal calcium carbonate total organic carbon total sulfur and total nitrogen for one sediment core these data imply that the complicated water structure in the sw okhotsk sea changed with time from the last glacial to holocene the glacial surface water was characterized by low primary production in the summer and expanded sea ice coverage in the winter during this time the ventilation might have reached deeper than during the holocene during the major deglacial period including the melt water pulses 1a and 1b the deep sea oxygen content had declined with less ventilation and or more oxygen consumption with organic matter supply into the deeper depths the intermediate layer has been well ventilated and has supplied large amount of organic matter during the last 20 kyrs especially in the early mid holocene however such condition ceased during 3 to 2 ka the warm pacific deep water has been present since 9 ka the influence of warmer surface water such as the soya warm current swc increased in the coastal area during 7 to 4 ka and since 2 ka till present neritic derived productivity might be extended at 2 2 1 8 ka and since 1 2 ka till present

formation of 26 8 26 9 σθ water in the kuril basin of the sea of okhotsk as a possible origin of north pacific intermediate water by using all japanese hydrographic data obtained south of 55 n in latitude in the sea of okhotsk we compile a data set for this study our investigations with these data show that a large quantity of relatively cold fresh oxygen rich homogeneous intermediate water with a density range of 26 8 to 26 9 exists in the kuril basin we name this intermediate water the kuril basin intermediate water kbiw results of isosteric analyses show that a possible origin of kbiw is located in a region off the hokkaido coast in the southwestern sea of okhotsk we suggest that kbiw is produced by the isopycnal mixing of relatively dense soya warm water which appears only in early spring with the colder fresher water which originates from the northwestern okhotsk finally we demonstrate that kbiw may be a source water of the north pacific intermediate water npiw because it has the same density range and water properties

probabilistic earthquake expectancy in the northeast indian region abstract gumbel9s theory of extreme events has been applied to the prediction of earthquake recurrence rates in the northeast indian region using the largest annual earthquakes occurring between 1929 and 1978 a period for which records are relatively complete for the northeast indian region as a whole the average return periods for an earthquake of magnitude 8 or greater are found to be about 30 and 25 yr applying types i and iii distributions respectively the magnitudes of the largest annual earthquakes expected to occur in 25 50 and 100 yr for six different tectonic blocks of the region are also estimated

the production scheme of cycladophora davisiana radiolaria in the okhotsk sea and the northwestern north pacific implication for the paleoceanographic conditions during the glacials in the high latitude oceans 1 the sediment trap study clearly unraveled that the distinct peaks of c davisiana fluxes occurred during summer to autumn in both the okhotsk sea and the northwestern north pacific the production of c davisiana is closely related to the microbial production in the intermediate water in the okhotsk sea the distinct microbial biomass in the intermediate water which is associated with the seasonal sea ice rejected brine water during winter may support the high c davisiana abundance therefore the significantly high c davisiana abundance during the last glacial maximum lgm in the high latitude open oceans implies the distinct microbial biomass in the intermediate water caused by the seasonal sea ice coverage analogous to the present okhotsk sea

morphological signatures of fault lines in an earthquake prone zone of southern baromura hill north east india a multi sources approach for spatial data analysis this paper aims to assess the morphological signatures of tectonic features faults on the basis of multi sources spatial data analysis for that purpose the present authors selected the southern part of baromura hill of tripura which has been discussed very little in the scientific literatures an extensive field work was done in the assumed faulted areas to understand the geomorphic signatures of faulting in the field gps was used for fixing the ground control points scanned survey of india soi topographical sheets spot pan and land sat band 5 was used for digital analysis an old dem on irs liss iii fcc was also consulted for final mapping two clear lineaments faults were detected from field observation on southern baromura hill apart from these another one was found in the outer part of this hill range an attempt was made to explain the morphological signatures of those faults by density slicing on radiometric data based on emittance of different physical components finally a geomorphic map with main tectonic features of baromura was prepared for future disaster management planning

cycladophora davisiana abundances as a paleoceanographic and stratigraphic tool in high latitude siliciceous sediments abstract like the oxygen isotope curve the relative abundance curve for cycladophora davisiana hereafter c curve exhibits synchronous fluctuations between high latitude regions it was also thought that high abundances of c davisiana indicated glacial periods although numerous short c curves have been calibrated to oxygen isotope curves spanning the last 100 kyr only two longer c curves have been associated with oxygen isotopes spanning the last 0 425 myr in the southern ocean and 1 1 myr in the sea of okhotsk this lack of well established long c curve calibrations to the oxygen isotope curve decreases the reliability of the c curve for periods beyond 100 ka furthermore recent work indicates that high abundances of c davisiana do not necessary indicate glacial conditions this study sought to establish a long c davisiana curve by directly calibrating the c curve to oxygen isotope records measured from benthic foraminifera in the north pacific over the last 740 kyr to discuss the paleoceanographic significance of the c curve and to check the suitability of the c curve as a stratigraphic tool samples were obtained from core c9001c which was recovered at a water depth of 1180 m east of the shimokita peninsula in the tohoku region of japan the core contained a continuous stratigraphic succession down to marine isotope stage 18 740 ka abundance peaks exceeding 5 of the total radiolarian fauna were defined as davisiana event dae and a total of 20 daes were observed over the last 740 kyr the daes were generally near interglacial glacial period boundary whereas peaks in the radiolarian total abundance reflecting warm surface radiolarian productivity occur mainly within the interglacial intervals the daes appear to reflect hydrological and productivity events in the intermediate water masses of the studied site during climatic transition we correlated the occurrence of 20 daes in shimokita area with c curve davisiana events identified in previous studies the c curve fluctuations appear to be generally synchronized in the north pacific sea of okhotsk and southern ocean supporting the interpretation that daes are intermediate water changes possibly caused by ice cover fluctuations in high latitude regions on the background of the glacial interglacial cycling

a sequence of seismic activity in the kanto area precursory to the 1923 kanto earthquake the kanto earthquake m 7 9 that occurred along the sagami trough in the sagami bay on 1 september 1923 was one of the most disastrous earthquakes in japanese history the kanto area includes metropolitan tokyo and yokohama which are densely populated and hence it has been a matter of great concern from the viewpoints of earthquake prediction and disaster prevention whether or not the 1923 kanto earthquake was preceded by precursory seismicity a study using the most complete lists of earthquakes catalogued recently by utsu and the japan meteorological agency reveals that seismic activity in the kanto area was appreciably higher before and after the kanto earthquake and that the kanto earthquake was preceded by a sequence of anomalous seismic activity quiescence and foreshocks such higher activity before and after the kanto earthquake is contrasted with low seismicity during the recent 30 year period a model is proposed to explain the precursory seismic activity subsequent quiescence and foreshocks for the kanto earthquake in the model the transition from precursory seismic activity to quiescence is ascribed to time dependent fracture due to stress aided corrosion foreshocks are related to an acceleration of premonitory slip shortly before the mainshock slip

eemian interglacial reconstructed from a greenland folded ice core efforts to extract a greenland ice core with a complete record of the eemian interglacial 130 000 to 115 000 years ago have until now been unsuccessful the response of the greenland ice sheet to the warmer than present climate of the eemian has thus remained unclear here we present the new north greenland eemian ice drilling neem ice core and show only a modest ice sheet response to the strong warming in the early eemian we reconstructed the eemian record from folded ice using globally homogeneous parameters known from dated greenland and antarctic ice core records on the basis of water stable isotopes neem surface temperatures after the onset of the eemian 126 000 years ago peaked at 8 4 degrees celsius above the mean of the past millennium followed by a gradual cooling that was probably driven by the decreasing summer insolation between 128 000 and 122 000 years ago the thickness of the northwest greenland ice sheet decreased by 400 250 metres reaching surface elevations 122 000 years ago of 130 300 metres lower than the present extensive surface melt occurred at the neem site during the eemian a phenomenon witnessed when melt layers formed again at neem during the exceptional heat of july 2012 with additional warming surface melt might become more common in the future

dense water production on the northern okhotsk shelves comparison of ship based spring summer observations for 1996 and 1997 with satellite observations for the northern okhotsk sea polynyas five russian ctd surveys taken during 1995 to 1997 are used to examine the evolution of the polynya dense water the surveys show that consistent with other investigations the largest potential densities are 26 99 and the densest water occurs in sakhalin and shelikhov bays the surveys also suggest that the shelikhov water drains directly into the deep okhotsk while on the northern shelves gravity currents transport the dense water west to sakhalin bay for comparison determination of the polynya sizes and ice production from satellite passive microwave and meteorological observations shows that polynyas occur on the northwest shelf nws between ayan and okhotsk city on the northern shelf between okhotsk city and magadan and in shelikhov bay in contrast the observations show that sakhalin bay is a region of land fast ice with no polynyas so that the dense water observed here cannot form locally for all polynyas the satellite observations show that the nws contributes 60 to 70 of the total ice production and due to the warmer 1997 air temperatures the 1996 production is about 1 5 times the 1997 value an estimate of the ice production from the surveys shows a similar regional distribution and enhancement of the 1996 production with the satellite and ship estimates in agreement within their error bars finally analysis of the dense water outflow shows that the upper okhotsk sea mode water has a renewal time of about 4 years the lower part about 14 years

a pervasive link between antarctic ice core and subarctic pacific sediment records over the past 800 kyrs recently developed xrf core scanning methods permit paleoceanographic reconstructions on timescales similar to those of ice core records we have investigated the distribution of biogenic barium ba al opal and carbonate ca al in a sediment core retrieved from the abyssal subarctic pacific odp 882 50 n 167 e 3244 m over an interval that spans the full length of the epica dome c edc ice core record ba al and biogenic opal show a strong resemblance to the edc dd and co2 with generally high concentrations during interglacials and lower values during ice ages of the past 800 kyrs the sedimentary ba al and biogenic opal are most easily interpreted as indicating a reduced sinking flux of organic matter from the surface ocean during cold periods the ba al maxima during peak interglacials are accompanied by transient ca al peaks in these otherwise carbonate devoid sediments which are best explained by a deepening of the calcite lysocline presumably due to reduced storage of respired co2 in the deep north pacific for most of the luke warm interglacials noted between 420 and 750 ka in edc the ba al peaks in odp 882 are also lower further strengthening the evidence for a simple physical link between global climate and the biogeochemistry of the subarctic pacific

low b value prior to the indo myanmar subduction zone earthquakes and precursory swarm before the may 1995 m 6 3 earthquake abstract some 455 events mb 4 5 in the indo myanmar subduction zone are compiled using the isc ehb neic catalogues 1964 2011 for a systematic study of seismic precursors b value and swarm activity temporal variation of b value is studied using the maximum likelihood method beside cusum algorithm the b values vary from 0 95 to 1 4 for the deeper depth 60 km earthquakes and from 0 85 to 1 3 for the shallower depth

recent earthquake swarms in garhwal himalaya a precursor to moderate to great earthquakes in the region abstract himalayas one of the most seismically active belts have been formed due to continent continent collision and are probable locations for future moderate to great earthquakes it is of paramount importance to recognize precursory swarm activity considered to be long predictors of main events recently two earthquake swarms occurred across main central thrust mct in garhwal himalayan region in a time interval of nearly one month the first swarm of april 2009 had epicentral locations lying north of mct on hanging wall side which has shown less seismic activity in recent times while the second swarm occurred in may 2009 near gopeshwar having epicenters on active seismic zone located south of mct the approximate distance between the two swarms is about 50 km in present study preparation zone of 100 100 km 2 has been demarcated recognizing these swarms as precursors to moderate to great earthquake in the garhwal himalaya

woce section p1w in the sea of okhotsk 1 oceanographic data description we describe the results of a world ocean circulation experiment woce survey line p1w from the open pacific ocean through the bussol strait and across the sea of okhotsk observations are presented of distributions of temperature and salinity dissolved oxygen and nutrients and some derived quantities discussion centers on the distribution of the sea of okhotsk component of the north pacific intermediate water mass and its properties the sea of okhotsk has been suggested as the only location where deep convection may occur within the north pacific or its marginal seas our analysis suggests that the surface 26 85 has recently been ventilated and arguments might be made to suggest that ventilation has occurred to 27 05 this is discussed here but detailed evidence is covered in a companion paper analyzing cfc observations the okhotsk component of the north pacific intermediate water extends to substantially greater depths and densities and so some other process is needed to create the denser water mass

impact of faults on landslide in the atharamura hill along the nh 44 tripura the present study is aimed at assessing the relationship between existing faults and occurrence of landslides the geophysical techniques like geothermal imaging of fault zone soil electrical resistivity data and field verification identify the fault characteristic the present study reveals two prominent faults in the atharamura hill i e one north south extended faults and the other east west extended faults the change in the geothermal characteristic along the fault structural data dip strike and most significantly the locations of landslide close to faults provide strong correlation of the landslide and the existing faults the soil electrical resistivity data are low along the faults the subsurface resistivity profile clearly delineates the faults

seismic assessment in southern baromura hill northeast india considering geophysical aspects this paper aims to assess the geophysical signatures like morphology and structure of a fault line which is situated in a part of southern baromura hill of tripura northeast india in this work manual observations and technical applications were adopted for understanding the morphological and structural characters of the fault line as tectonic mapping is one of the main objectives of this study the remote sensing technique was used to prepare a tectonic map of the study area geothermal range of the area was measured by unsupervised classification of landsat tm thermal infrared band band 6 the classified thermal band was overlaid by another classified shortwave infrared band band 7 of landsat tm which explains the structural evidences of the study area in addition an automated digital elevation model dem was prepared to assess the morphological characters of the study area particularly near the confluence of r maharani and r gumti to analyse the structural condition of the faulted zone resistivity characters of the rocks were measured by vertical electrical sounding ves method the electrical resistivity character of this area strongly supports that a displacement occurred in this place finally an attempt was made to explain the character of faulting on the basis of morphological signatures and structural evidences for future disaster management planning

pleistocene and holocene distribution of the radiolarian amphimelissa setosa cleve in the north pacific and north atlantic evidence for water mass movement abstract the radiolarian amphimelissa setosa is one of the prominent species of the pleistocene radiolarian assemblages in the sea of okhotsk below the marine isotope stage mis boundary 5 4 and it represents one of the most abundant radiolarian species in holocene and modern environments of the nordic seas we studied the a setosa distribution in six cores from the sea of okhotsk and established morphometric measurements on a setosa specimens from two cores of the sea of okhotsk and one core from the labrador sea we further compared our data with other available studies from the subarctic pacific the labrador sea the north atlantic the norwegian sea and the iceland greenland seas in order to discuss the possible settling of the species from the north pacific via the arctic ocean into the iceland greenland seas a setosa exhibits a stable abundant population in the sea of okhotsk during most of the last ca 0 7 m y and might repeatedly extend its population into the north atlantic through the arctic ocean during the pleistocene interglacial optima the species declines from the sea of okhotsk and from the subarctic pacific at the end of mis 5 its final documented settling into the north atlantic is during mis 5 when a setosa appears in low numbers in sediments of the labrador sea however reaching significant percentages at the boundary of mis 5 4 based on the available information we propose that a setosa could migrate from the north pacific into the arctic ocean during the interglacial optimum mis 5e and then through the channels of the canadian arctic archipelago into the baffin bay and labrador sea a further migration step of a setosa occurs at the boundary of mis 5 4 when a setosa migrated from the labrador sea into the north atlantic probably related to a southward expansion of cold waters at the end of the mis 5 during the warming at termination i a setosa moved from the north atlantic into the nordic seas the abundant occurrence of a setosa in sediments south of iceland the norwegian and north seas within the younger dryas period points to a marked cooling and a southward movement of polar water masses restricted to this time interval

glacial holocene environment of the southeastern okhotsk sea evidence from geochemical and palaeontological data abstract environmental conditions and productivity changes in the southeastern okhotsk sea have been reconstructed for the last 20 ka using planktonic and benthic foraminiferal oxygen isotope records and calcium carbonate organic carbon and opal content data from two sediment cores species variability in benthic foraminiferal and diatom assemblages provides additional palaeoceanographic evidence ams radiocarbon dating of the sediments and oxygen isotope stratigraphy serve as the basis for the age models of the cores for the last 20 14 c kyr and for correlation between environmental variations in the okhotsk sea and regional and global climate changes benthic foraminiferal assemblages in the two cores depth 1590 and 1175 m varied with time so that we could recognise seven zones with different species composition changes in the benthic foraminiferal assemblages parallel major environmental and productivity variations during the last glaciation fluxes of organic matter to the sea floor showed strong seasonal variations indicated by the presence of abundant a weddellensis and infaunal uvigerina spp benthic foraminiferal assemblages changed with warming at 12 5 11 and 10 8 14 c kyr bp when productivity blooms and high organic fluxes were coeval with global meltwater pulses 1a and 1b younger dryas cooling caused a decline in productivity 11 10 kyr bp affecting the benthic faunal community subsequent warming triggered intensive diatom production opal accumulation and a strong oxygen deficiency causing significant changes in benthic fauna assemblages from 5 26 4 4 kyr bp to present time

searching for an earthquake precursor a case study of precursory swarm as a real seismic pattern before major shocks a long range correlation between earthquakes is indicated by some phenomena precursory to strong earthquakes most of the major earthquakes show prior seismic activity that in hindsight seems anomalous the features include changes in regional activity rate and changes in the pattern of small earthquakes including alignments on unmapped linear features near the future main shock it has long been suggested that large earthquakes are preceded by observable variations in regional seismicity studies on seismic precursors preceding large to great earthquakes with m 7 5 were carried out in the northeast india region bounded by the area 20 32 n and 88 100 e using the earthquake database from 1853 to 1988 it is observed that all earthquakes of m 7 5 including the two great earthquakes of 1897 and 1950 were preceded by abnormally low anomalous seismicity phases some 11 27 years prior to their occurrence on the other hand precursory time periods ranged from 440 to 1 768 days for main shocks with m 5 6 6 5 for the period from 1963 to 1988 furthermore the 6 august 1988 main shock of m 7 5 in the arakan yoma fold belt was preceded by well defined patterns of anomalous seismicity that occurred during 1963 1964 about 25 2 years prior to its occurrence the pattern of anomalous seismicity in the form of earthquake swarms preceding major earthquakes in the northeast india region can be regarded as one of the potential seismic precursors database constraints have been the main barrier to searching for this precursor preceding smaller earthquakes which otherwise might have provided additional information on its existence the entire exercise indicates that anomalous seismicity preceding major shocks is a common seismic pattern for the northeast india region and can be employed for long range earthquake prediction when better quality seismological data sets covering a wide range of magnitudes are available anomalous seismic activity is distinguished by a much higher annual frequency of earthquake occurrence than in the preceding normal and the following gap episodes

foreshock statistics and their possible relationship to earthquake prediction in the italian region this study focuses on the foreshocks of earthquake sequences recorded by the italian national seismological network between 1975 and 1991 we consider as foreshocks events exceeding a given threshold magnitude that follow a period of quiescence and come before a mainshock occurring within a given time distance range the total number of potential foreshocks identified by the algorithm depends on the size and the duration of the predefined quiescence area whereas the number of mainshocks preceded by foreshocks depends also on the size of the area in which the event is expected and the duration of the alarm period our aim was to optimize the choice of the parameters defining potential foreshocks as precursors of stronger earthquakes in order to improve their validity and reliability a preliminary investigation carried over the whole italian territory allowed the definition of zones where foreshocks mainshocks series are likely to occur one of these zones is an area of about 32 000 km2 in central italy including a total of 2671 events of m 2 5 where there is a significant tendency of moderate shocks to be followed at short distance and in short time by larger shocks our method would lead to issuing 63 alarms with the optimal definition of foreshocks as events of magnitude exceeding 3 0 after at least 80 days of quiescence in an area of 140 km radius the rate of occurrence for mainshocks of magnitude exceeding 4 0 during the following 48 hours in the specified area of 30 km radius is 6 of 23 events the corresponding probability gain is about 150 for comparison another larger zone po valley with 453 events of m 2 5 exhibits only a rate of 1 of 82 precursors in this area most events are single shocks our analysis shows that the foreshock activity can be regarded as a significant earthquake precursor so suggesting that real time observation of seismicity can be used to improve the quality of an earthquake prediction system

ice age terminations 230th dated oxygen isotope records of stalagmites from sanbao cave china characterize asian monsoon am precipitation through the ends of the third and fourthmost recent ice ages as a result am records for the past four glacial terminations can now be precisely correlated with those from ice cores and marine sediments establishing the timing and sequence of major events in all four cases observations are consistent with a classic northern hemisphere summer insolation intensity trigger for an initial retreat of northern ice sheets meltwater and icebergs entering the north atlantic alter oceanic and atmospheric circulation and associated fluxes of heat and carbon causing increases in atmospheric co2 and antarctic temperatures that drive the termination in the southern hemisphere increasing co2 and summer insolation drive recession of northern ice sheets with probable positive feedbacks between sea level and co2

geochemical multielement signatures of glacial and interglacial facies of the okhotsk sea deepwater sediments during the past 350 kyr a response to global climate changes at the orbital and millennial scales the previously dated deepwater sediment core mr06 04 pc 7r length 1723 cm 350 kyr recovered from the central okhotsk sea os was analyzed for biogenic compounds and for 63 chemical elements using the inductively coupled plasma mass spectrometry method with a high resolution 1 cm 200 years a one box model with two main members and mathematical methods based on multielemental composition of sediments for the calculation of weight fractions at each time slice of two main types of geochemical facies that dominate during considerably diverse climatic periods glacial maxima and interglacial optima were proposed and tested this model can be applied to other analogous natural systems whose sedimentation is driven by two main types of geochemical facies the application of the developed model to the studied core revealed that variations of weight fractions of the typical interglacial and glacial geochemical facies in the sediments along the core depth named as warm and cold covariators respectively change synchronously with global and regional climate variability profiles of warm and inversed cold covariators coincide tightly and their values increase during warm marine isotope stages and substages and decrease during cold ones over the last 350 kyr millennial scale changes in covariators had occurred simultaneously with abrupt variability in the os productivity and sediment lithology and with millennial global climate variability some discrepancies in the warm and inversed cold covariators calculated using specific mathematical treatments revealed the episodic influence of volcanogenic matter presented in the core by visible tephra layers and cryptotephras

earthquake swarms as a long range precursor to large earthquakes in turkey summary turkey has been the location of a series of major earthquakes during this century this study is an attempt to predict these in hindsight using swarms of weak earthquakes as a long range precursor as proposed by keilis borok some modifications of the swarm identification algorithm are made and statistical measures of success to judge the success of the prediction scheme were introduced the main measures of success are the percentage of large earthquakes predicted and the percentage of swarms that predicted large earthquakes the method was applied separately to earthquakes in the north anatolian fault zone and in western turkey the north anatolian fault was first considered in its entirety and then in segments prediction was attempted in each of these regions with a variety of parameters and the measures of success with confidence levels are computed the results obtained for prediction in turkey are promising the success of predicting large earthquakes m 7 was generally greater than 60 per cent the difficulties of this method arise from incomplete catalogues of seismicity and the use of many arbitrary parameters

glacial age hydrography of the far northwest pacific ocean stable isotope data on benthic foraminifera from more than 30 cores on the northern emperor seamounts and in the okhotsk sea are synthesized in paleohydrographic profiles spanning the depth range 1000 4000 m holocene core top benthic foraminiferal 18o and 13c data are calibrated to modern hydrographic properties through measurements of 13c of co2 and 18o of seawater cibicidoides stable isotope ratios are close to the 13c and equilibrium 18o of seawater whereas uvigerina 18o and 13c are variably offset from cibicidoides glacial maximum 13c of cibicidoides displays a different vertical profile than that of the holocene when results are adjusted by 0 32 to account for the secular change in 13c during the last glacial maximum the data coincide with the modern seawater and foraminiferal curves deeper than 2 km however at shallower depths 13c gradually increases by as much as 1 above the modern value furthermore above 2 km the benthic 18o decreases by 0 5 these results are consistent with a benthic front at 2 km in the north pacific see herguera et al 1992 but they differ from interpretations based on trace metal data which indicate a source of nutrient depleted deep water during glaciation the isotopic data suggest that during glaciation there was a better ventilated watermass at intermediate depths in the far northwestern pacific it was relatively fresher than deep waters there and deep waters were as nutrient rich as today

repeated pleistocene glaciation of the east siberian continental margin during glacial periods ice sheets covered continental margins through much of arctic north america greenland and western eurasia marine structures suggest that an ice sheet up to a kilometre in depth periodically covered the east siberian continental shelf as well

global ice volume fluctuations north atlantic ice rafting events and deep ocean circulation changes between 130 and 70 ka multiproxy data from north atlantic deep sea sediment core neap18k provide a detailed record of climate through oxygen isotope stage ois 5 seven distinct large scale episodes of ice rafting c25 c19 were identified between 126 and 70 ka global ice volume reconstructions based on high resolution benthic 18 o records indicate that major ice rafting events were not confined to ice volume maxima at ois 5d and 5b but also occurred during periods of ice sheet growth and disintegration however iceberg discharges were restricted to times when sea levels were 40 65 m below present values ice rafting episode c25 the first large scale cooling of mid atlantic surface waters after the last interglacial occurred during the gradual buildup of continental ice sheets at the ois 5e 5d transition major ice sheet collapses allied to ice rafting events c24 and c21 were associated with rapid sea level increases of 20 and 40 m respectively suborbital climatic fluctuations in the neap18k sedimentary record denoted by prominent 7 5 4 5 and 3 k y cyclicities appear to correlate with both greenland atmospheric temperatures and changes in thermohaline circulation patterns inferred from benthic 13 c values and hence provide clear evidence of a highly interconnected north atlantic climatic regime during ois 5

radiolarian based transfer function for the estimation of sea surface temperatures in the southern ocean atlantic sector a new radiolarian based transfer function for sea surface temperature sst estimations has been developed from 23 taxa and taxa groups in 53 surface sediment samples recovered between 35 and 72 s in the atlantic sector of the southern ocean for the selection of taxa and taxa groups ecological information from water column studies was considered the transfer function allows the estimation of austral summer sst december march ranging between 1 and 18 c with a standard error of estimate of 1 2 c sst estimates from selected late pleistocene squences were sucessfully compared with independent paleotemperature estimates derived from a diatom transfer function this shows that radiolarians provide an excellent tool for paleotemperature reconstructions in pleistocene sediments of the southern ocean

late quaternary changes in intermediate water oxygenation and oxygen minimum zone northern japan a benthic foraminiferal perspective 1 a strong oxygen minimum zone omz currently exists at upper intermediate water depths on the northern japanese margin nw pacific the omz results largely from a combination of high surface water productivity and poor ventilation of upper intermediate waters we investigated late quaternary history last 34 kyr of ocean floor oxygenation and the omz using quantitative changes in benthic foraminiferal assemblages in three sediment cores taken from the continental slope off shimokita peninsula and tokachi northern japan at water depths between 975 and 1363 m these cores are well located within the present day omz a region of high surface water productivity and in close proximity to the source region of north pacific intermediate water late quaternary benthic foraminiferal assemblages experienced major changes in response to changes in dissolved oxygen concentration in ocean floor sediments foraminiferal assemblages are interpreted to represent three main groups representing oxic suboxic and dysoxic conditions assemblage changes in all three cores and hence in bottom water oxygenation coincided with late quaternary climatic episodes similar to that known for the southern california margin these episodes in turn are correlated with orbital and millennial climate episodes in the greenland ice core including the last glacial episode bolling allerod b a younger dryas preboreal earliest holocene early holocene and late holocene the lowest oxygen conditions marked by dysoxic taxa and laminated sediments in one core occurred during the b a and the preboreal intervals suboxic taxa dominated mainly during the last glacial the younger dryas and most of the holocene dysoxic conditions during the b a and preboreal intervals in this region were possibly caused by high surface water productivity at times of reduced intermediate ventilation in the northwestern pacific remarkable similarities are evident in the late quaternary sequence of benthic foraminiferal assemblage change between the two very distant continental margins of northern japan and southern california the oscillations in omz strength reflected by these faunal changes were widespread and apparently synchronous over wide areas of the north pacific reflecting broad changes in intermediate water ventilation and surface ocean productivity closely linked with late quaternary climate change on millennial and orbital timescales

late pleistocene holocene radiolarian and pollen records from sediments in the sea of okhotsk in two cores with oxygen isotope stratigraphy from the southern okhotsk sea marine pollen and siliceous microfauna record concurrent late glacial through holocene variations in regional terrestrial and marine environments glacial vegetation around the southern okhotsk basin which resembles the present tundra steppe of the northwest coast of this marginal sea yields to spruce dominated boreal forests during the glacial interglacial transition temperate forest components such as oak peak during the mid holocene decreasing oak accompanied by increasing spruce reflects the effect of global cooling on local vegetation during the last 4 kyr although the radiolarian fauna in the okhotsk sea samples is similar to that present in the northwest pacific the dominant species in both regions differ concentrations of radiolarians are low in latest glacial samples with higher concentrations occurring above and below this interval cycladophora davisiana the dominant radiolarian species in the majority of holocene okhotsk sea sediments is present at lower percentages in late glacial samples from our two sites thus this species holocene latest pleistocene abundance pattern in sea of okhotsk sediments is the reverse of that recorded in high latitude open ocean sites the combined marine pollen and radiolarian records indicate changes in the sea of okhotsk s physical oceanographic conditions and surrounding vegetation during the late glacial which were associated with this region s response to global climate change

factors influencing the distribution patterns of recent deep sea benthic foraminifera east of new zealand southwest pacific ocean abstract this study investigates which combination of environmental factors most strongly influences the distribution patterns of benthic foraminferal tests 0 63 m in a region bisected by the subtropical front east of new zealand seafloor sample sites extend from outer shelf 90 m to abyssal 4700 m depths across substrates ranging from biogenic terrigenous gravelly sand to hemipelagic mud and occur under the influence of antarctic intermediate water aaiw and circumpolar deep waters as well as receiving detritus from both subtropical and subantarctic surface water masses elevated values of the planktic foraminiferal fragmentation index and reworked small paleogene planktic foraminifera at outer shelf and bathyal depths coincide with areas of strong bottom currents q mode cluster analysis on the census counts of 398 benthic species clusters the 66 samples into three large groups shallow bathyal abyssal and at a lower level 10 mappable associations are recognised a combination of canonical correspondence analysis and a correlation coefficient matrix was used to relate the faunal data to a set of measured environmental proxies these analyses show that factors that have a relationship with depth are the most significant in determining foraminiferal distribution the principal environmental factors which appear to most strongly influence this benthic foraminiferal distribution are dissolved oxygen content in bottom waters sustainability of organic carbon flux rates seasonality of food supply lateral advection of water masses bottom water carbonate corrosiveness energetic state at the benthic boundary layer grain size composition of substrate salinity and temperature of the bottom waters shallow water associations 90 1250 m dominated by cassidulina carinata and trifarina angulosa occur within coarse substrates under well oxygenated high energy regimes and sustained food input the occurrence of the bathyal associations 230 2840 m dominated by c carinata alabaminella weddellensis and abditodentrix pseudothalmanni closely mirrors the distribution of aaiw within a region of variable food supply the sustainability of food supply combined with bottom water type and associated ventilation and dissolution strongly influence the composition of abyssal associations 1200 4700 m mostly dominated by epistominella exigua and a weddellensis

preservation of elemental and isotopic source identification of sedimentary organic matter the amount and type of organic matter in the sediments of lakes and oceans contribute to their paleoenvironmental and paleoclimatological records only a small fraction of the initial aquatic organic matter survives destruction and alteration during sinking and sedimentation selective degradation modifies the character of the surviving small fraction of organic matter which becomes incorporated in bottom sediments organic matter alterations can continue to sub bottom depths of hundreds of meters corresponding to millions of years source and paleoenvironmental information nonetheless remains preserved in the molecular elemental and isotopic compositions of organic matter c n and 13c values of total organic matter in particular appear to retain paleoenvironmental information for multi myr time periods

strange attractor characteristics of earthquakes in shillong plateau and adjoining regions strange attractor dimensions were determined for two concentric areas of about 220 km 2 and 440 km 4 radii around wwssn station at shillong based on earthquake data during the period 1964 to 1992 existence of deterministic chaos for both the areas was supported by the same fractal dimension of 6 1 and positive value of the largest lyapunov exponent the results have provided justification for delineating precursory seismicity patterns based on earthquakes up to epicentral distance of 440 km on different fault systems conspicuous higher value of the strange attractor dimension in hindukush himalaya and northeast india than that in koyna region in the peninsular india suggests a new criteria for distinction between interplate and intraplate earthquakes differences with subduction zone in pacific vis a vis stress drop in great earthquakes m 8 and implications of the chaotic approach in earthquake hazard analysis have also been brought out

northeastern atlantic benthic foraminifera during the last 45 000 years changes in productivity seen from the bottom up we studied benthic foraminifera from the last 45 kyr in the 63 mu m size fraction in biogeochemical ocean flux studies bofs cores 5k 50 degrees 41 3 n 21 degrees 51 9 w depth 3547 m and 14k 58 degrees 37 2 n 19 degrees 26 2 w depth 1756 m at a time resolution of several hundreds to a thousand years the deepest site showed the largest fluctuations in faunal composition species richness and benthic foraminiferal accumulation rates the fluctuations resulted from changes in abundance of epistominella exigua and alabaminella weddellensis in the present oceans these species bloom opportunistically when a spring plankton bloom results in seasonal deposition of phytodetritus on the seafloor the phytodetritus species had very low relative abundances and accumulation rates during the last glacial maximum a strong increase in absolute and relative abundance of e exigua and a weddellensis during deglaciation paralleled the decrease in abundance of the polar planktonic foraminifer neogloboquadrina pachyderma s and the increase in abundance of warmer water planktonic species such as globigerina bulloides this strong increase in relative abundance of the phytodetritus species and the coeval increase in benthic foraminiferal accumulation rate were thus probably caused by an increase in the deposition of phytodetritus to the seafloor and thus probably of surface productivity when the polar front retreated to higher latitudes the abundance of phytodetritus species decreased during the younger dryas but not to the low levels of fully glacial conditions during heinrich events periods of excessive melt water formation and ice rafting benthic accumulation rates were very low as were the absolute and relative abundances of the phytodetritus species supporting suggestions that surface productivity was very low during these events in both cores pullenia and cassidulina species were common during isotope stages 2 3 and 4 as were bolivinid buliminid and uvigerinid species high relative abundances of these species have been interpreted as indicative either of sluggish deep water circulation or of high organic carbon fluxes to the seafloor in our cores relative abundances of these species are negatively correlated with benthic foraminiferal accumulation rates and we can thus not interpret them as indicative of increased productivity during glacials the percentage of these low oxygen species calculated on a phytodetritus species free basis decreased slightly at deglaciation at 5k but not at 14k this suggests that decreased production of north atlantic deep water during the last glacial might have slightly affected benthic foraminiferal faunas in the eastern north atlantic at 3547 m depth but not at 1756 m in conclusion major changes in deep sea benthic foraminiferal faunas over the last 45 000 years in our cores from the northeastern atlantic were the result of changes in surface water productivity not of changes in deep water circulation productivity was lower during the glacial probably because of extensive ice cover

occurrence of anomalous seismic activity preceding large to great earthquakes in northeast india region with special reference to 6 august 1988 abstract seismicity database from 1860 to 1985 of northeast india region bounded by the area 20 32 n and 82 100 e have been analyzed for the identification of precursory swarm anomalous seismic activity preceding large to great earthquakes with m 7 5 it is observed that with the exception of three earthquakes 1908 1912 and 1918 the large earthquakes of 1897 1946 1947 1950 and 1951 1952 were preceded by well developed epoch of swarm anomalous seismic activity in space and time well before their occurrence the seismicity is observed to fluctuate in the order of low high low ranging from 0 0 5 01 33 to 0 0 7 events year prior to these mainshocks during the epochs of normal background swarm anomalous and gap quiescence respectively the duration of precursory gap is observed to vary from 11 to 17 years for mainshocks of m 7 5 8 0 and from 23 to 27 years for m 8 7 and this period is dependent on the magnitude of the mainshocks using the values of magnitude of mainshock m m average magnitude of swarm m p and the precursory time gap t p the following predictive equations are established for the region m m 1 37 m p 1 40 m m 3 log t p 3 27 all the major earthquakes with m b 6 1 occurred during 1963 1988 have been investigated for their association with anomalous seismicity precursory swarms using the events with cutoff magnitude m b 4 5 eleven such events have occurred in the region during the period except one earthquake of 29 may 1976 all the remaining 10 earthquakes were associated in some forms of anomalous seismicity epochs well defined patterns of anomalous seismicity are observed prior to 1964 1965 12 august 1976 and 30 december 1984 m b 5 6 all these mainshocks are preceded by seismicity patterns in the order of low high low similar to that observed prior to the mainshocks from 1897 to 1962 the anomalous seismicity epoch is delineated with extremely high annual earthquake frequency which was preceded and followed by extremely low seismicity epochs of background and gap quiescence phases consequently seismicity rates during anomalous seismicity epoch have always been above normal 1 event year whereas it is always below normal during the preceding and the following epochs a prediction was made using the 1964 swarm based on the m p and t p values that a large earthquake with m 8 0 5 with focal depth 100 40 km could occur any time from 1986 to 1990 in an area bound by 21 25 5 n latitudes and 93 96 e longitude in arakan yoma fold belt it is interesting to note that the 6 august 1988 earthquake with magnitude 7 5 and focal depth 115 km had occurred within the delineated zone in addition three consecutive swarm activities are identified in a limited area within the eastern syntaxis and these were not followed by any mainshock till date and could be potential zone for future earthquake

environmental change in the sea of okhotsk during the last 1 1 million years on the basis of two sedimentary records from the central sea of okhotsk we reconstruct the closely coupled glacial interglacial changes in terrigenous flux marine productivity and sea ice coverage over the past 1 1 myr the correspondance of our sedimentary records to the china loess grain size record china loess particle timescale chiloparts suggests that environmental changes in both the sea of okhotsk area and in se asia were closely related via the siberian atmospheric high pressure cell during full glacial times our records point to a strong siberian high causing northerly wind directions the extension of the sea ice cover and a reduced amur river discharge deglacial maxima of terrigenous flux were succeeded by or synchronous to high productivity events marine productivity was strengthened during glacial terminations because of an effective nutrient utilization at times of enhanced water column stratification and high nutrient supply from fluvial runoff and sea ice thawing during interglacials se monsoonal winds prevailed analogous to today s summer situation of a pronounced mongolian heat low and a strong hawaiian high strong freshwater discharge induced by high precipitation rates in the amur drainage area and a seasonally reduced and mobile sea ice cover favored marine productivity although being considerably lower than during the terminations and a lowered flux of ice rafted detritus

spatiotemporal variations in the b value of earthquake magnitude frequency distributions classification and causes abstract interpretation of the b value of earthquake frequency magnitude distributions has received considerable attention in recent decades this paper provides a comprehensive review of previous investigations of spatial and temporal variations in b value including their classification and possible causes based on least squares regression of seismicity data compiled from the neic iris and isc catalogs we find an average value of 1 02 0 03 for the whole earth and its two hemispheres consistent with the general view that in seismically active regions the long term average value is close to unity nevertheless wide ranging b variations 0 3 b 2 5 have been reported in the literature this variability has been interpreted to arise from one or more of the following factors prevailing stress state crustal heterogeneity focal depth pore pressure geothermal gradient tectonic setting petrological environmental geophysical characteristics clustering of events incomplete catalog data and or method of calculation excluding the latter all of these factors appear to be linked directly or indirectly with the effective state of stress although time dependent changes in b value are well documented conflicting observations reveal either a precursory increase or decrease in b value before major earthquakes our compilation of published analyses suggests that statistically significant b variations occur globally on various timescales including annual monthly and perhaps diurnal taken together our review suggests that b variations are most plausibly linked with changes in effective stress

late quaternary changes of the oxygen conditions in the bottom and intermediate waters on the western kamchatka continental slope the sea of okhotsk microfossil data on the foraminifers and radiolarians in the sediment core komex lv28 44 3 the kamchatka slope in the eastern sea of okhotsk exhibit the changes in the water oxygen conditions during the last 146 ky the paleoenvironmental proxies are the radiolarian species cycladophora davisiana as indicator of the upper intermediate water ventilation and the benthic planktonic foraminifers as indicators of the bioproductivity and bottom water oxygenation in case of sediment core lv28 44 3 the bottom water represents the lower intermediate one so that conclusions on paleoenvironments are applicable for the most range of the local intermediate water the well oxygenated intermediate and near bottom waters existed in the area of study during the penultimate glaciation of mis 6 early weichselian initiation of the last glaciation within mis 5b d and last glacial stages of mis 3 2 the intervals of the short low o2 bottom events with suboxic conditions dissolved o2 in water 0 3 1 2 ml l occur during the last interglacial mis 5e eemian stage 125 to 113 ka and during the last deglaciation 17 5 to 6 5 ka eemian low o2 bottom events are associated with the high bioproductivity of the subsurface water but poor ventilation on the upper intermediate depths the low o2 bottom events during the last deglaciation occurred at the high bioproductivity of the subsurface water and active ventilation on the upper intermediate depths

comparison of radiolarian vertical distributions in the okhotsk sea near the kuril islands and in the northwestern north pacific off hokkaido island abstract the vertical distribution of radiolarians was investigated by using a closing type net with 63 m mesh in the okhotsk sea station nu 2 near bussol strait down to 1000 m depth and in the northwestern north pacific oyashio region station x down to 500 m depth both stations were sampled in september 1995 radiolarian standing stocks were high between 50 and 200 m at both stations and generally decreased with depth the depth integrated living total radiolarian standing stock from 0 to 500 m at station nu 2 was more than three times higher than that at station x the maximum standing stocks of polycystine radiolarians occurred in the 50 100 m depth interval but there were also significant abundance peaks of phaeodarian radiolarians in the 100 200 m interval at both stations the radiolarian production is likely to be associated with not only phytoplankton production in upper waters but also with microbial production in intermediate waters a total of 79 taxa were encountered 25 spumellaria 41 nassellaria and 13 phaeodaria five radiolarian groups were obtained based on r mode cluster analysis group a lower intermediate water dwellers 300 1000 m group b taxa with different distributions in the okhotsk sea 300 1000 m and in the oyashio region 0 100 m group c upper intermediate water dwellers 200 500 m group d surface subsurface water dwellers 0 200 m and group e taxa with pronounced 200 m

the b value before the 6th august 1988 india myanmar border region earthquake a case study abstract smith 1981 1986 and wyss et al 1990 have observed that intermediate term quiescence is often associated with an increasing b value this study pertains to the temporal behaviour of the b value before the earthquake of 6th august 1988 which occurred in the india myanmar border region the b value in the preparation zone of the earthquake 21 25 5 n 93 96 e as identified by gupta and singh 1986 1989 is found to have increased gradually from 1976 to a maximum value of 1 33 during july 1987 followed by a short term drop before the occurrence of the earthquake the quiescence period observed by gupta and singh 1986 1989 for this earthquake is better reflected by the intermediate term increase in the b value a drop in the mean magnitude since 1978 is supported by a cusum plot

high resolution paleoproductivity fluctuations during the past 24 kyr as indicated by benthic foraminifera in the marginal arctic ocean abstract analyses of benthic foraminifera in sediment cores taken at about 1000 m water depth at the yermak plateau and the barents sea slope adjacent to the position of the ice sheet edge during the last glacial maximum show that paleoproductivity was reduced to about a third of its present level during peak glacial stadials these reduced values are still higher than values for modern permanently ice covered regions suggesting that the core locations were at least partially ice free even during stadials paleoproductivity at the core locations was higher than or equal to that of today during initial deglaciations and warm substages peak paleoproductivity occurred in samples with low salinity surface waters as indicated by oxygen isotope values of planktonic foraminifera and slightly after increased abundance of atlantic species suggesting that enhanced advection of warmer waters from the atlantic supported the initial ice sheet retreat during the holocene climatic optimum productivity was much less than at present on the yermak plateau high at the barents sea site perhaps because of increased advection of atlantic water to the latter site and heavier ice coverage at the former after this optimum paleoproductivity at both sites was similar with slightly lower values during cold periods such as the little ice age

background seismicity rates and precursory seismic quiescence imperial valley california the problem of recognizing precursory seismicity rate changes consists of two steps first a background or normal rate must be determined and second anomalous rates must be recognized in this paper we address the first of these steps determining a background seismicity rate two problems must be dealt with if a meaningful background rate is to be determined first dependent events must be recognized and removed from consideration and second detection or reporting changes must be accounted for a number of techniques are available for recognizing dependent events we used the one developed by mcnally 1976 in this work the technique we used for recgonizing detection and reporting changes was developed by habermann 1983 we demonstrate these techniques on seismicity from the imperial valley region of california after a reasonable background rate is determined we examine seismicity rates in this region prior to the imperial valley earthquake of 15 october 1979 the source area of the earthquake shows a possible precursory quiescence which started during july 1979 the time of this rate decrease is close to the time of a change in the seismic instrumentation in the imperial valley which makes it difficult to determine whether the decrease is real or related to detection several other seismicity rate changes observed in the imperial valley appear to be related to changes in the operation of the network there these include quiescent periods which occur only if magnitude cutoffs are applied to the data and periods of low reporting of events with m 2 5 these observations suggest that magnitudes were not reported for some events during several time periods all of these observations indicate that determination of detection histories is crucial for meaningful seismicity studies

consistently dated records from the greenland grip gisp2 and ngrip ice cores for the past 104 ka reveal regional millennial scale δ18o gradients with possible heinrich event imprint abstract we present a synchronization of the ngrip grip and gisp2 ice cores onto a master chronology extending back to 104 ka before present providing a consistent chronological framework for these three greenland records the synchronization aligns distinct peaks in volcanic proxy records and other impurity records chemo stratigraphic matching and assumes that these layers of elevated impurity content represent the same instantaneous event in the past at all three sites more than 900 marker horizons between the three cores have been identified and our matching is independently confirmed by 24 new and previously identified volcanic ash tephra tie points using the reference horizons we transfer the widely used greenland ice core chronology gicc05modelext to the two summit cores grip and gisp2 furthermore we provide gas chronologies for the summit cores that are consistent with the gicc05modelext timescale by utilizing both existing and new gas data ch4 concentration and 15n of n2 we infer that the accumulation contrast between the stadial and interstadial phases of the glacial period was 10 greater at summit compared to at ngrip the 18o temperature proxy records from ngrip grip and gisp2 are generally very similar and display synchronous behaviour at climate transitions the 18o differences between summit and ngrip however changed slowly over the last glacial interglacial cycle and also underwent abrupt millennial to centennial scale variations we suggest that this observed latitudinal 18o gradient in greenland during the glacial period is the result of 1 relatively higher degree of precipitation with a pacific signature at ngrip 2 increased summer bias in precipitation at summit and 3 enhanced rayleigh distillation due to an increased source to site distance and a potentially larger source to site temperature gradient we propose that these processes are governed by changes in the north american ice sheet nais volume and north atlantic sea ice extent and or sea surface temperatures sst on orbital timescales and that changing sea ice extent and ssts are the driving mechanisms on shorter timescales finally we observe that maxima in the summit ngrip 18o difference are roughly coincident with prominent heinrich events this suggests that the climatic reorganization that takes place during stadials with heinrich events possibly driven by a southward expansion of sea ice and low ssts in the north atlantic are recorded in the ice core records

anomalous seismicity and earthquake forecast in western nepal himalaya and its adjoining indian region precursory swarms associated with major earthquakes in the western nepal himalaya and its adjoining region bounded by 28 0 31 0 n and 79 5 82 2 e have been studied using seismicity data from 1963 to 2006 the delineation of preparation zones for future seismic disturbances is carried out using the temporal and the spatial distribution of earthquakes considering the events with cutoff magnitude m b 4 3 in four anomalous episodes normal background n anomalous swarm a precursory gap g and main shock sequence m respectively five cases of anomalous seismicity have been identified including two cases for which quiescence episodes still continue three moderate earthquakes of 1980 m b 6 1 bajhang 1984 m b 5 6 bajura and 1999 m b 6 6 chamoli in western nepal and its adjoining indian region were preceded by well defined patterns of anomalous seismicity precursory swarm two additional cases of anomalous seismicity patterns were observed 1 1999 2006 and 2 2003 2006 in these two cases no main shock has yet occurred however the seismicity from 1999 onwards has fluctuated from low to high to low as in the precursory sequences for previous earthquakes the occurrence of the swarm sequence followed by a quiescence phase which is still continuing is an indication of a precursory seismicity gap in the region from the predictive equations developed for the himalayan frontal arc it is estimated that an earthquake of m 6 5 0 5 may occur at any time up to 2011 in an area bounded by 29 3 30 5 n and 81 2 81 9 e in the focal depth range 10 30 km

oceanographic conditions associated with high abundances of the radiolarian cycladophora davisiana abstract the cosmopolitan radiolarian cycladophora davisiana usually comprises less than 5 of the radiolarian fauna in holocene sediments in recent sediments from the sea of okhotsk however this species frequently represents more than 20 of the radiolarian assemblage at times during the late pleistocene abundances of this species in excess of 40 are recorded in marine sediments from high latitude oceans 40 of both hemispheres the sea of okhotsk apparently represents a modern analogue of climatic and oceanographic conditions that existed throughout large portions of high latitude oceans at times during the late pleistocene the near surface water structure of the sea of okhotsk is characterized by a low salinity surface layer with a strong temperature minimum near its base the low surface salinities are responsible for maintaining near freezing subsurface temperatures as well as establishing relatively stable temperatures and salinities at depths below the temperature minimum this water structure is produced at least in part by intense freezing of sea ice in winter with subsequent summer melting the physical characteristics of the upper water column affect the abundance and activity of shallow dwelling flora and fauna while providing a stable subsurface environment for deeper dwelling fauna

relation of subtropical atlantic temperature high latitude ice rafting deep water formation and european climate 130 000 60 000 years ago abstract a new high resolution record of sea surface temperature from the subtropical western north atlantic documents a series of abrupt coolings within marine isotope stage 5 which can be objectively correlated with marine core evidence for increased ice sheet discharge at subpolar latitudes and reduced north atlantic deep water formation these results indicate that ice sheet forcing of deep ocean circulation influenced surface temperatures over much of the north atlantic a proposed correlation to the pollen record of grande pile france indicates that each cold event seen in the pollen sequence has a unique counterpart in the record of subtropical ocean temperature if this correlation is correct it suggests that the warmest part of the european eemian ended suddenly in response to oceanographic changes and that the subsequent post temperate phase of the eemian extended well into the interval of ice sheet growth corresponding to marine isotope substage 5d

active faulting and tectonics of burma and surrounding regions this study of the active tectonics of burma and surrounding regions is based mostly on an interpretation of landsat imagery and on fault plane solutions for shallow and intermediate earthquakes fold axes in the indoburman ranges and an east dipping inclined zone of intermediate depth earthquakes suggest that a slab of oceanic lithosphere was recently subducted to the east under the indoburman ranges fault plane solutions of shallow earthquakes however do not show underthrusting at the present time instead p axes are oriented roughly north south parallel not perpendicular to the fold axes in the ranges p axes for fault plane solutions of intermediate shocks also trend north south parallel to the strike of the subducted slab and may indicate that the hanging slab is being dragged north by india through the surrounding asthenosphere the sagaing fault probably accommodates most of the right lateral slip of india past indochina but india s northward movement also causes internal deformation within burma thailand and yunnan differences between the tectonic fabric seen on the landsat images and the tectonic regime compatible with the fault plane solutions throughout the region imply major changes in the directions of relative motion in the orientations of strain and in the style of deformation in the late cenozoic presumably these changes reflect the transition from subduction to collision and strike slip motion as india penetrated into eurasia past burma large parts of burma and thailand may have rotated several tens of degrees clockwise in this process

okhotsk sea ice coverage and kamchatka glaciation over the last 350ka evidence from ice rafted debris and planktonic δ18o high resolution records of ice rafted debris ird and oxygen isotope records spanning an e w trending transect across the okhotsk sea unravel the marine and terrestrial cryogenic history of ne siberia over the last 350 kyr ird predominantly dispersed basin wide by sea ice shows lowest fluxes during interglacial periods implying a reduced and seasonal sea ice coverage highest ird accumulation rates are observed during glacial and deglacial periods with a more extended but highly dynamic ice cover although being rather synchronous ird fluxes are on average higher in the western okhotsk sea than in the eastern part pointing to a persistent but mobile particle supplying sea ice cover even during full glacial conditions presumably less dense in the eastern parts mis 6 is exceptional in this respect asynchronous fluxes of ird which vary spatially reflect rapid paleoclimatic and paleo glaciomarine changes ird accumulation rates were by factor 2 3 higher during mis 6 as compared to the last glacial maximum and the ird depositional center shifted from the western okhotsk sea early mis 6 toward kamchatka late mis 6 synchronous to a distinct change in the ird mineral composition both the characteristic composition of late mis 6 ird originating from the sredinny mountain range of kamchatka and their significantly enhanced accumulation rates refer to intensified iceberg dispersal across the eastern part of the okhotsk sea at 138 ka 135 ka 129 ka and 128 ka bp this scenario affords the presence of extended mountain glaciers protruding down to sea level on the western side of kamchatka anomalously light planktonic stable oxygen isotopes during mis 6 3 termination ii and mis 5 5 5 4 suggest significant freshwater supply related to the westward drainage of kamchatka glaciers the intensified kamchatka glaciation observed during late mis 6 was repeated during mis 3 iceberg discharges into the eastern okhotsk sea are observed at 60 ka 51 ka 42 ka 38 ka 36 ka and 31 ka and may partly correspond to n atlantic heinrich events

radiolarians under the seasonally sea ice covered conditions in the okhotsk sea flux and their implications for paleoceanography abstract four time series sediment traps at two stations and three piston cores from the okhotsk sea were quantitatively examined for coarse sized radiolarian shells 63 m traps were deployed at 300 m and 1550 m at station m4 53 01 n 145 30 e and at 300 m and 700 m at station m6 49 30 n 146 28 e during august 1998 through may 2000 the chronologies of the piston cores were established applying 18 o and paleomagnetic intensity variations they provide records extending back to marine isotope stage mis 5 51 the modern and past changes in radiolarian assemblages are associated with environmental and productivity changes radiolarian fluxes in the sediment traps exhibited significant summer to autumn flux peaks with suppressed values during the winter when sea ice covered the sea surface at the trap sites total radiolarian accumulation rate rar variations in each core tended to correspond to glacial interglacial cycles and increased during the last deglaciation in particular the temporal rar variation in core xp98 pc1 off kamchatka showed a similar trend with the climatic changes expressed by 18 o values during the glacial interglacial cycles for the last 125 kyr regional differences were also apparent rars showed extremely low values during 12 40 kyr and 63 70 kyr in core xp98 pc2 central okhotsk sea indicating the enhanced sea ice impact the sea ice coverage might have continued for a significant part of the year during the intervals since radiolarians did not appear to increase even during the summer to autumn rar variations in core xp98 pc4 off sakhalin showed higher values than xp98 pc2 during mis 2 and 4 thus in eastern sakhalin around site xp98 pc4 sea ice coverage might have been seasonal but not perennial even during mis 2 and 4 among the radiolarian taxa cycladophora davisiana was the most abundant species at the lower traps and in all cores the fluxes of c davisiana at lower traps showed much higher values than those of upper traps and also showed similar temporal patterns with the fluxes of aluminum and terrigenous materials therefore c davisiana fluxes may be associated with terrigenous organic materials increased nutrient supply from the continental shelves presumably transported by seasonal sea ice and released by sea ice melting might be mainly responsible for the high production of c davisiana in the okhotsk sea especially during the last deglaciation

living benthic foraminifera of the okhotsk sea faunal composition standing stocks and microhabitats live rose bengal stained benthic foraminifera were investigated in surface sediment samples from the okhotsk sea to reveal the relationship between faunal characteristics and environmental parameters live benthic foraminifera were quantified in the size fraction 125 m in the upper 8 cm of replicate sediment cores recovered with a multicorer at five stations along the sakhalin margin and at three stations on the southwestern kamchatka slope the stations are from water depths between 625 to 1752 m located close or within the present okhotsk sea oxygen minimum zone with oxygen levels between 0 3 and 1 5 ml l 1 at the high productivity and ice free kamchatka stations live benthic foraminifera are characterized by maximal standing stocks about 1700 3700 individuals per 50 cm2 strong dominance of calcareous species up to 87 91 of total live faunas and maximal habitat depths down to 5 2 6 7 cm depth vertical distributions of total faunal abundances exhibit a clear subsurface maximum in sediments at the sakhalin stations which are seasonally ice covered and less productive live benthic foraminifera show lower standing stocks about 200 1100 individuals per 50 cm2 lower abundance of calcareous species 10 64 of total live faunas and shallower habitat depths down to 2 5 5 4 cm depth faunal vertical distributions are characterized by maximum in the uppermost surface sediments it is suggested that 1 lower and strongly seasonal organic matter flux caused by the seasonal sea ice cover and seasonal upwelling 2 lower bottom water oxygenation 0 3 1 1 ml l 1 and 3 more pronounced influence of carbonate undersaturated bottom water along the sakhalin margin are the main factors responsible for the observed faunal differences according to species downcore distributions and average living depths common calcareous species were identified as preferentially shallow intermediate and deep infaunal foraminiferal microhabitat occupation correlates with the organic matter flux and the depth of the oxygenated layer in sediments

characteristics of earthquake sequence in northern himalayan region of south central tibet precursor search and location of potential area of future earthquake abstract this paper reports that three earthquake sequence occurred in 1996 m b 5 9 1998 m b 5 8 and 2004 2005 m b 6 2 6 3 were observed preceding the anomalous seismic activity the nature of anomalous seismicity associated with these earthquakes have been investigated considering earthquakes with m b 4 1 cut off magnitude for this region in four seismic episodes nagm normal background n anomalous swarm a precursory gap g and mainshock sequence m respectively it is established here that the anomalous seismicity swarm patterns follow episodes of relatively very low seismic activity and it is an important finding to visualize that an area might be preparing for the occurrence of a forthcoming mainshock such anomalous seismic patterns were observed prior to medium size mainshocks that occurred from 1963 to 2006 in south central tibet sct region to the north of central himalaya from these observations it may be inferred here that the patterns of anomalous seismicity earthquake swarms may be considered as an important parameter precursor for the forecasting of long range earthquake hazards in the sct region in consideration of spatial and the temporal clustering of swarm events that are prominent and confined in a vertical column of 10 45 km enabled to locate potential area enclosed by 29 6 30 1 n and 87 8 88 1 e where future earthquake of magnitude 6 0 and above in the depth range 25 15 km may be seated in view of this multi parameter short term precursory signals monitoring is suggested for the delineated preparatory area to make earthquake prediction forecasting programs more meaningful

a high resolution absolute dated late pleistocene monsoon record from hulu cave china oxygen isotope records of five stalagmites from hulu cave near nanjing bear a remarkable resemblance to oxygen isotope records from greenland ice cores suggesting that east asian monsoon intensity changed in concert with greenland temperature between 11 000 and 75 000 years before the present yr b p between 11 000 and 30 000 yr b p the timing of changes in the monsoon as established with 230th dates generally agrees with the timing of temperature changes from the greenland ice sheet project two gisp2 core which supports gisp2 s chronology in this interval our record links north atlantic climate with the meridional transport of heat and moisture from the warmest part of the ocean where the summer east asian monsoon originates

quantitative reconstruction of the last interglacial vegetation and climate based on the pollen record from lake baikal russia changes in mean temperature of the coldest t c and warmest month t w annual precipitation p ann and moisture index were reconstructed from a continuous pollen record from lake baikal russia the pollen sequence con01 603 2 53 57 n 108 54 e was recovered from a 386 m water depth in the continent ridge and dated to ca 130 114 8 ky bp this time interval covers the complete last interglacial li corresponding to mis 5e results of pollen analysis and pollen based quantitative biome reconstruction show pronounced changes in the regional vegetation throughout the record shrubby tundra covered the area at the beginning of mis 5e ca 130 128 ky consistent with the end of the middle pleistocene glaciation the late glacial climate was characterised by low winter and summer temperatures t c 38 to 35 c and t w 11 13 c and low annual precipitation p ann 300 mm however the wide spread of tundra vegetation suggests rather moist environments associated with low temperatures and evaporation reconstructed 1 tundra was replaced by boreal conifer forest taiga by ca 128 ky bp suggesting a transition to the interglacial taiga dominant phase lasted until ca 117 4 ky bp e g about 10 ky the most favourable climate conditions occurred during the first half of the li p ann reached 500 mm soon after 128 ky bp however temperature changed more gradually maximum values of t c 20 c and t w 16 17 c are reconstructed from about 126 ky bp conditions became gradually colder after ca 121 ky bp t c dropped to 27 c and t w to 15 c by 119 5 ky bp the reconstructed increase in continentality was accompanied by a decrease in p ann to 400 420 mm however the climate was still humid enough 0 9 to support growth of boreal evergreen conifers a sharp turn towards a dry climate is reconstructed after ca 118 ky bp causing retreat of forest and spread of cool grass shrub communities cool steppe dominated the vegetation in the area between ca 117 5 ky and 114 8 ky bp suggesting the end of the interglacial and transition to the last glacial mis 5d shift to the new glaciation was characterised by cool and very dry conditions with t c 28 to 30 c t w 14 15 c p ann 250 mm and 0 5

medium term forecast of the 1988 north east india earthquake abstract northeast india is seismically one of the most active intra continental regions in the world it has been a site of 10 earthquakes of magnitude m 7 5 during the last 100 years gupta and singh j geol soc india 28 1986 367 406 systematically analysed the time series of earthquakes associated with several main shocks in an area bound by 20 n and 32 n latitude and 87 e and 100 e longitude and concluded 1 moderate magnitude to great earthquakes in the north east india region are found to be preceded generally by well defined earthquake swarms and quiescence periods 2 on the basis of an earthquake swarm and quiescence period an area bound by 21 n and 25 5 n latitude and 93 e and 96 e longitude is identified to be the site of a possible future earthquake of m 8 0 5 with a focal depth of 100 40 km this earthquake should occur any time from now onwards should it not occur till the end of 1990 this forecast could be considered as a false alarm this medium term earthquake forecast came true with the occurrence of the m 7 3 earthquake on august 6 1988 within the specified spatial and temporal parameters the forecast of this earthquake was based on the concept of precursory swarms and quiescence preceding main shocks it is worthwhile noting that in the entire region under study the august 6 1988 earthquake was the largest since the august 17 1952 earthquake of m 7 5 this lends support to the worldwide effort to study and identify spatial and temporal variation of seismicity and recognise patterns that precede major earthquakes

similarities and dissimilarities between the last two deglaciations and interglaciations in the north atlantic region abstract sea surface temperatures ssts recorded by alkenones and oxygen isotopes in the alboran basin are used here to describe at an unprecedented fine temporal resolution the present interglaciation pig initiated at 11 7 ka bp the last interglaciation lig onset approximately at 129 ka and respective deglaciations similarities and dissimilarities in the progression of these periods are reviewed in comparison with ice cores and stalagmites cold spells coeval with the heinrich events h described in the north atlantic include multi decadal scale oscillations not previously obvious up to 4 c in less than eight centuries within the stadials associated with h1 and h11 ca 133 ka and 17 ka respectively these abrupt oscillations precede the accumulation of organic rich layers deposited when perihelion moves from alignment with nh spring equinox to the summer solstice a reference for deglaciations events observed during the last deglaciation at 17 ka 14 8 ka and 11 7 ka are reminiscent of events occurred during the penultimate deglaciation at ca 136 ka 132 ka and 129 ka respectively the sst trend during the pig is no more than 2 c from 20 c to 18 c up to 0 2 c ka the trend is steeper during the lig i e up to a 5 c change from the early interglaciation to immediately before the glacial inception from 23 c to 18 c up to 0 4 c ka events are superimposed upon a long term trend towards colder ssts beginning with sst maxima followed by temperate periods until perihelion aligned with the nh autumn equinox before ca 5 3 ka for the pig and 121 ka for the lig a cold spell of around eight centuries at 2 8 ka during the pig was possibly mimicked during the lig at ca 118 ka by a sst fall of around 1 c in a millennium these events led interglacial sst to stabilise at around 18 c the glacial inception barely evident at the beginning ca 115 ka north atlantic event c25 after perihelion passage in the nh winter solstice culminated with a sst drop of at least 2 c in two millennia event c24 ca 111 ka the little ice age 0 7 ka also occurred after the latest perihelion passage in the nh winter solstice and could be an example of how a glacial pre inception event following an interglaciation might be

sea level and deep water temperature changes derived from benthic foraminifera isotopic records we show that robust regressions can be established between relative sea level rsl data and benthic foraminifera oxygen isotopic ratios from the north atlantic and equatorial pacific ocean over the last climatic cycle we then apply these regressions to long benthic isotopic records retrieved at one north atlantic and one equatorial pacific site to build a composite rsl curve as well as the associated confidence interval over the last four climatic cycles our proposed reconstruction of rsl is in good agreement with the sparse rsl data available prior to the last climatic cycle we compute bottom water temperature changes at the two sites and at one southern indian ocean site taking into account potential variations in north atlantic local deep water 18o our results indicate that a last glacial maximum lgm enrichment of the ocean mean oxygen isotopic ratio of 0 95 is the lowest value compatible with unfrozen deep waters in the southern indian ocean if local deep water 18o did not increase during glacials with respect to present such a value of the lgm mean ocean isotopic enrichment would impose a maximum decrease in local bottom water 18o at the north atlantic site of 0 30 during glacials

linear trends in salinity for the world ocean 1955 1998 1 quality controlled oceanographic profile salinity measurements from the world ocean database 2001 wod01 were used to calculate linear trends of zonally averaged salinity anomalies for running five year periods from 1955 1959 through 1994 1998 for the world ocean and the atlantic pacific and indian ocean basins from the surface to 3000 meters depth each basin exhibits large scale coherent trends most of the pacific is freshening with the exception of the subtropical south pacific the atlantic exhibits a deep freshening in the subpolar gyre and a shallower more intense increase in salinity in the tropics and subtropics the indian ocean is becoming more saline at all latitudes in the upper 150 meter layer with a subsurface freshening between 40 s and the equator in the 250 1000 meter layer there is freshening in both the weddell and ross seas

stable isotope and lithologic evidence of late glacial and holocene oceanography of the northwestern pacific and its marginal seas abstract stable isotopes geochemical lithological and micropaleontological results from cores from the far northwest fnw pacific and the okhotsk and bering seas are used to reconstruct the regional environment for the last glaciation the deglacial transition and the holocene 18 o records of planktonic foraminifera of the region show two light shifts during deglacial time provoked by the freshening of the surface water and climate warming these north pacific terminal events t1anp and t1bnp with ages of 12 500 and 9300 yr b p respectively occur almost simultaneously with two episodes of accelerated glacier melting around the north atlantic along with the isotopic shifts the caco 3 content in regional sediments increased abruptly 1a and 1b carbonate peaks probably due to changes of productivity and pore water chemistry of surface sediments organic matter and opal concentration increased during the transition between t1anp and t1bnp events in the sediments of the fnw pacific and the southern part of the bering sea and opal content increased in the holocene in the bering and okhotsk seas 13 c records of cores from the okhotsk and bering seas and the fnw pacific do not contradict the hypothesis of increased intermediate water formation in the region during glaciation during deglaciation accumulation of the coarse terrigenous component decreased in sediments of the bering sea and the fnw pacific before the t1anp event probably as a result of rising sea level and opening of the bering strait

orbital and millennial scale environmental and hydrological changes of the central okhotsk sea over the last 136 kyr inferred from micropaleontological radiolarian and benthic foraminifera geochemical and lithological proxies and the mechanisms responsible for them abstract the response of benthic foraminifera bf and radiolarian production in the central okhotsk sea os to orbital and millennial changes of climate and environment over the last 136 kyr have been studied on the basis of the sediment core pc 7r with available productivity geochemical and lithological records and a modified age model we used the calculated accumulation rate of microfossils ar fluxes of the main ecological groups and species indicative of radiolarians and of bf as quantity responses in their production which is related to environmental and hydrological changes of the water column and surface sediment in the central os and to global and regional climate changes the responses of the opportunistic bf alabaminella weddellensis and the suboxic group during the last 136 kyr were mostly related to changes in organic fluxes from the surface sea ice cover and surface sediment oxygenation at both orbital and millennial time scales the ar of radiolarians from the surface dichothermal and mesopelagic groups significantly differed from the ar of bf the ar has a maximum during the middle and late marine isotope stage 5e and lower values during the earlier holocene while the minimum happened during cold marine isotope stages 6 4 and 2 with maximal ventilation of os intermediate water production of the mesopelagic radiolarian cycladophora davisiana in the os was mostly related to the lateral delivery of terrigenous material and om into the water column from the northwestern shelf and or from the western subarctic pacific due to the sensitivity of marine organisms to environmental conditions the production of radiolarians and bf sharply changed with the extinction of amphimelissa setosa since heinrich stadial 8 is related to the termination of global environment cooling and the hydrology changes of the early last glacial