environmental conditions for the presence of magnetofossils in the last glacial maximum inferred from magnetic parameters of sediments from the ulleung basin east sea abstract magnetic characterization of sediments from the ulleung basin in the east sea japan sea was carried out to decipher changes in environmental conditions over the last 39 000 years magnetic susceptibility intensities of natural remanent magnetization nrm anhysteretic remanent magnetization arm partial arm parm and saturation isothermal remanent magnetization sirm were measured for selected samples irm acquisition hysteresis and first order reversal curve forc measurements were made the ratios of rock magnetic parameters such as arm sirm arm and s ratio were determined to identify magnetic grain size and mineralogical variations along with electron microscope observations of magnetic mineral extracts down core variations in rock magnetic parameters for the 5 21 m long sediment core reveal distinct intervals with different grain size concentration and composition of magnetic minerals the uppermost portion and the high magnetic intensity zone hiz in marine isotope stage mis 2 are characterized by higher concentrations of fine grained magnetite whereas the mis 1 and 3 intervals contain lower concentrations of coarser grained magnetic minerals with increasing influence of hematite and or iron sulphide minerals the hiz interval is inferred to contain high occurrences of fine grained bacterial magnetosomes based on geochemical proxies east sea conditions for the hiz interval coincident with the last glacial maximum lgm can be summarized as having low total organic carbon toc enhanced eolian contributions from terrestrial organic particles and iron bearing minerals under the influence of an intensified east asian winter monsoon along with iron reducing but not sulphidic conditions that favoured growth and preservation of magnetotactic bacteria the delicate balance between reductive dissolution of magnetofossils under sulphidic conditions and production and preservation of magnetotactic bacteria in overlying iron reducing sediments for the hiz interval is responsible for the resultant abundance variations of magnetosomes in the studied sediments

environmental magnetic implications of magnetofossil occurrence during the middle eocene climatic optimum meco in pelagic sediments from the equatorial indian ocean abstract magnetic properties of pelagic marine sediments that record the middle eocene climatic optimum meco at 40 ma provide information about major environmental changes the main variations observed during this transient warming event reflect a bacterial magnetofossil signal but the cause of the linkage between bacterial production and climate remains unclear we present an environmental magnetic study of middle eocene deep sea sediments from the northern edge of madingley rise ocean drilling program hole 711a equatorial indian ocean to investigate the origin of the increased magnetic mineral concentration concomitant with subchron c18n 2n which corresponds to the meco interval in odp hole 711a this magnetic mineral peak also coincides with a change in lithofacies from calcareous nannofossils to radiolarian ooze and a slight increase in clay concentration magnetite is the main magnetic mineral in the meco sediments which occurs as magnetically non interacting single domain biogenic particles the increased magnetic mineral concentration across the meco event is likely to have been caused by increased eolian iron fertilization this is interpreted to have given rise to increased surface ocean productivity where increased delivery of iron and nutrients to the seafloor enhanced magnetotactic bacterial populations during the meco event

characterizing magnetofossils from first order reversal curve forc central ridge signatures the central ridge structure of a first order reversal curve forc distribution is indicative of uniaxial noninteracting single domain magnetic particles which provides the opportunity to identify and characterize biogenic magnetic mineral remains magnetofossils in sediments recent studies have shown that magnetofossils are widespread in the geological record and that they carry useful environmental information and contribute to paleomagnetic recording which makes it essential to quantify how these biogenic components contribute to the magnetic properties of sediments we present results from six sedimentary sequences whose magnetic mineral assemblages contain a significant magnetofossil contribution using principal component analysis we find that the central ridge properties exhibit both intra sequnce and inter sequence variability that may be ascribed to external environmental factors while samples from individual sediment sequences tend to cluster together there is a continuum of inter sequence behavior that appears to be related to a variety of magnetofossil properties we demonstrate the complexity of biogenic magnetic components in sedimentary environments but also the power and potential of forc central ridges for understanding magnetic mixtures and unraveling environmental information

characterization and quantification of magnetofossils within abyssal manganese nodules from the western pacific ocean and implications for nodule formation this work was supported financially by southern university of science and technology sustech grant y01316111 to y m c the national key r d program of china 2016yfa0601903 to q s l the national natural science foundation of china 41430962 to q s l the australian research council dp160100805 and dp200100765 to a p r and the 13th five year plan project of international maritime resources investigation and development dy135 c1 1 06 and dy135 r2 1 01 to x m s and the guangdong provincial key laboratory of marine resources and coastal engineering we thank the guangzhou marine geological survey for supplying the samples

rock magnetic artifacts on long term relative paleointensity variations in sediments 1 long term changes of geomagnetic field intensity including possible dependence on lengths of polarity intervals provide fundamentally important information for understanding the geodynamo a positive correlation between paleointensity and polarity interval length was previously suggested from an oligocene ca 23 34 ma relative paleointensity record at deep sea drilling program site 522 in the atlantic ocean which is the only continuous paleointensity data set published so far for this age interval we have conducted a paleomagnetic study of eocene to oligocene sediments at three sites in the eastern equatorial pacific ocean our objectives include revisiting the issue of the paleointensity polarity length correlation magnetic properties of the sediments meet the frequently used criteria for reliable relative paleointensity estimation although short wavelength normalized remanence intensity fluctuations associated with polarity boundaries and possible geomagnetic excursions agree among the three sites long term changes are inconsistent apparent positive correlation between normalized intensity and polarity length was observed but the normalized intensity has an obvious anti correlation with the ratio of anhysteretic remanent magnetization arm to isothermal remanent magnetization irm which is mainly controlled by the relative abundance of biogenic and terrigenous magnetic minerals furthermore the normalized intensity correlates with sedimentation rate these facts indicate a lithological contamination on the normalized intensity records the dependence on arm irm and sedimentation rate is also evident at site 522 it is inferred that variations in sedimentation rate and the relative abundance of biogenic magnetite on depositional remanent magnetization acquisition efficiency may not be well compensated by the normalization it is therefore premature to conclude that stronger geomagnetic fields were recorded during longer polarity intervals from currently available normalized intensity records

estimating small permanent rotation from strong motion records what is comparison with external measurements telling us abstract modern strong motion accelerometers record instruments translational accelerations as well as their rotation based on a detailed analysis of the low frequency content of acceleration records javelaud et al 2011 removed the permanent tilt information from strong motion records the accuracy of permanent rotation angles derived from acceleration time histories can be checked by comparison with external rotation information in practice this can be done at exceptional sites that experience earthquake induced permanent rotation and where the permanent rotation is recorded by various instruments situated above a hidden fault and located 4 km from the epicenter during the 2000 m j 7 3 western tottori earthquake in japan kasho dam experienced very strong shaking and a homogeneous tectonic rotation of about 1 5 10 4 rad over the dam and its reservoir areas because the dam is well instrumented plumb line strong motion seismometers pre and post earthquake ground surveys it makes an ideal site to check the accuracy of tectonic permanent rotation estimated from records of the strong motion seismometer located at the dam s foundation as a result of this benchmark the permanent rotation obtained from the analysis of strong motion acceleration time histories is consistent with external measurements which validates the methodology used and that strong motion time histories can be used to estimate permanent rotation

past environmental and circulation changes in the south china sea input from the magnetic properties of deep sea sediments abstract the south china sea located at the transition between the pacific and the indian ocean receives every year mainly during the rain season enormous amounts of river sediments originating from the erosion weathering of rocks in the catchment basins at sea these sediments are carried by different water masses to their deposition site and they constitute a unique archive for past environmental studies in this region the magnetic fraction of deep sea sediments though forming a minority in volume provides incredibly valuable information for paleoceanographic reconstructions as long as its provenance and source to sink processes are well constrained after a brief description of the climatic sedimentological and oceanographic context of the south china sea scs a review of the information available so far in the literature about the magnetic properties of scs sediments is presented it shows a large variety of interpretations conclusions that finally results in a rather unclear picture because in such a context the characterization of the sediment at the source is critical the magnetic properties recently obtained from a set of samples from rivers and marine surface sediments are summarized to describe the present day situation they are then used to interpret paleorecords from a set of seven marine cores distributed from the southern to the northern basins at different water depths and all covering at least the last climatic cycle the results reported here for the first time suggest that the magnetic mineralogy remains rather stable in time on land and that its time and spatial distribution at sea is an interplay of changes in sea level and deep sea circulation during low sea level periods bottom deep sea circulation is weak and the deposited sediment originates from the proximal rivers on the contrary during high sea level the circulation is enhanced transporting more sediment most likely from taiwan and luzon to the northwestern part of the scs and also in smaller proportion to the southern basin where it mixes with the local river borne sediment by comparing the two longest records we observe that this pattern is repeated over the last 900 ka superimposed to the 100 kyr cyclicity we also observe a longer term evolution with a maximum in the bottom current strength around 500 ka coinciding with global changes in the deep ocean circulation and carbon cycle these new results based on a wide spectrum of magnetic properties of numerous marine sedimentary cores from the scs show that the magnetic fraction yields important insights into past changes of the sedimentary pathways in particular the dynamic of the deep sea circulation depending on the global climatic context

a quantitative approach for estimating coseismic displacements in the near field from strong motion accelerographs the translational accelerations recorded by strong motion seismometers are often contaminated by baseline offsets that prevent recovering theground displace ments by double integration detailed analysis of the k net95 strong motion seis mometer and the improvement of the visual display of the recorded accelerations fourier transform by addition of long zero pads to the acceleration records made it possible to distinguish the origins of the long period noise that contaminate the translational accelerations recorded in the near field of two studied earthquakes the 2004 niigata ken chuetsu earthquake and the 2007 niigata ken chuetsu oki earthquake japan they are the residual rotation of the instrument residual tilt or the 1 f digital semiconductor noise the quantification of these two terms allows us to discuss the low frequency content of the records and to describe when it is possible to obtain realistic displacement time histories it happens when the residual tilt is removed in the time domain or when the 1 f semiconductor noise overshadows the translational acceleration records up to sufficiently small frequencies as a check of the method displacement time histories obtained from acceleration records are compared with nearby 1 hz gps data good similitudes are obtained in the near field for collocated instruments online material figures showing acceleration velocity and displacement time series and acceleration spectra for 18 records

micromorphological changes as an indicator of the transition from glacial to glaciofluvial quartz grains evidence from svalbard abstract the micromorphology of quartz grains in a sedimentary environment is determined by the transport mechanism and the nature of weathering both these aspects change during the transport history of grains thus important questions include how are quartz grains affected by possible changes in the transport medium and how quickly do the different micromorphological features develop or disappear the main goal of this study was to characterize the changes in the micromorphological features of quartz grains during the transition from a glacial to a glaciofluvial environment and to identify a set of diagnostic microtextures that can be used to distinguish between glacial and glaciofluvial quartz grains the samples came from the moraines of the bertilbreen and horbyebreen glaciers svalbard and from the sediments of glacier fed rivers in the forelands of these glaciers a total of 30 different micromorphological features was observed on 800 different quartz grains from 13 samples of glaciofluvial sediment and 3 samples of glacial sediment it was found that the frequency of rounded grains v shaped pits meandering ridges and cemented microblocks on glaciofluvial grains increased significantly with increasing length of fluvial transport whereas the frequency of angular grains straight steps straight and curved grooves adhering particles pitting and oriented etch pits decreased significantly different types of micromorphological features of quartz grains change with fluvial transport at different rates adhering particles after the first kilometer of fluvial transport straight steps and meandering ridges after the second kilometer of fluvial transport and v shape pits angular shape and straight grooves after the third kilometer of fluvial transport are reliable mechanical micromorphological features for distinguishing between glacial and glaciofluvial quartz grains

magnetic mineral diagenesis abstract reduction oxidation redox reactions occur during burial because sediments contain reactive mixtures of oxidised and reduced components diagenetic chemical reactions represent the approach of all sedimentary components toward equilibrium and control the long term stability of sedimentary iron bearing minerals magnetic minerals are sensitive indicators of sedimentary redox conditions and of changes in these conditions through time with diagenetic effects ranging from subtle to pervasive despite the importance of magnetic mineral diagenesis in paleomagnetism rock magnetism and environmental magnetism and the usefulness of these subjects in the earth and environmental sciences there is no systematic single published treatment of magnetic mineral diagenesis this paper is an attempt to provide such a treatment for the full range of diagenetic environments magnetic mineral diagenesis during early burial is driven largely by chemical changes associated with organic matter degradation in a succession of environments that range from oxic to nitrogenous to manganiferous to ferruginous to sulphidic to methanic where the free energy yielded by different oxidants decreases progressively in each environment in oxic environments the most important diagenetic processes involve surface oxidation of detrital minerals and precipitation of fe3 bearing minerals from solution in ferruginous environments the most reactive detrital and authigenic iron oxides undergo dissolution often mediated by dissimilatory iron reducing bacteria which releases fe2 that becomes available for other reactions the fe2 in solution can diffuse upward where it is oxidised to form new authigenic iron oxyhydr oxide minerals or it can become bioavailable to enable magnetotactic bacteria to biomineralise magnetite generally at the base of the overlying nitrogenous zone alternatively dissimilatory iron reducing bacteria can produce extracellular magnetite within ferruginous environments in sulphidic environments iron bearing detrital mineral assemblages undergo more radical alteration hydrogen sulphide which is a byproduct of bacterial sulphate reduction or of anaerobic oxidation of methane reacts with the fe2 released from iron mineral dissolution or directly with solid iron oxyhydr oxide minerals to form iron sulphide minerals mackinawite greigite and pyrite authigenic growth of ferrimagnetic greigite has important implications for paleomagnetic recording secondary iron sulphide formation can also occur as a result of anaerobic oxidation of methane methane migration through sediments in association with biogenic or thermogenic methane production or in association with gas hydrate dissociation can disrupt the diagenetic steady state and give rise to greigite and monoclinic pyrrhotite formation that remagnetises sediments most of the above described diagenetic processes occur below 50 c with continuing burial above 50 c but at sub metamorphic temperatures magnetic minerals can undergo further thermally induced chemical changes that give rise to a wide range of mineralogical transformations that affect the magnetic record of the host sediment these changes include remagnetisations magnetic analysis can provide much valuable information concerning diagenesis in environmental processes the range of processes discussed in this paper should assist researchers in analysing sediment magnetic properties for which the assessment of diagenetic effects has become a necessary component

enhanced primary productivity and magnetotactic bacterial production in response to middle eocene warming in the neo tethys ocean abstract earth s climate experienced a warming event known as the middle eocene climatic optimum meco at 40 ma which was an abrupt reversal of a long term eocene cooling trend this event is characterized in the deep southern atlantic pacific and indian oceans by a distinct negative 18 o excursion over 500 kyr we report results of high resolution paleontological geochemical and rock magnetic investigations of the neo tethyan monte cagnero mca section northeastern apennines italy which can be correlated on the basis of magneto and biostratigraphic results to the meco event recorded in deep sea sections in the mca section an interval with a relative increase in eutrophic nannofossil taxa and decreased abundances of oligotrophic taxa spans the culmination of the meco warming and its aftermath and coincides with a positive carbon isotope excursion and a peak in magnetite and hematite goethite concentration the magnetite peak reflects the appearance of putative magnetofossils while the hematite goethite apex is attributed to an enhanced detrital mineral contribution likely as aeolian dust transported from the continent adjacent to the neo tethys ocean during a drier more seasonal climate during the peak meco warming based on our new geochemical paleontological and magnetic records the meco warming peak and its immediate aftermath are interpreted as a period of high primary productivity sea surface iron fertilization is inferred to have stimulated high phytoplankton productivity increasing organic carbon export to the seafloor and promoting enhanced biomineralization of magnetotactic bacteria which are preserved as putative magnetofossils during the warmest periods of the meco event in the mca section together with previous studies our work reinforces the connection between hyperthermal climatic events and the occurrence or increased abundance of putative magnetofossils in the sedimentary record

oligocene miocene magnetic stratigraphy carried by biogenic magnetite at sites u1334 and u1335 equatorial pacific ocean 1 sediments from the equatorial pacific ocean at the integrated ocean drilling program sites u1334 and u1335 record reliable magnetic polarity stratigraphies back to 26 5 ma late oligocene at sedimentation rates usually in the 5 20 m myr range putative polarity subchrons that do not appear in current polarity timescales occur within chrons c5acr c5adn and c5bn 1r at site u1335 and within chrons c6aar 2r c6br c7ar and c8n 1n at site u1334 subchron c5dr 1n 17 5 ma is recorded at both sites supporting its apparent recording in the south atlantic ocean and has an estimated duration of 40 kyr the oligocene miocene calcareous oozes have magnetizations carried by submicron magnetite as indicated by thermal demagnetization of magnetic remanences the anhysteretic remanence to susceptibility ratio and magnetic hysteresis parameters transmission electron microscopy of magnetic separates indicates the presence of low titanium iron oxide magnetite grains with size 50 100 nm and shape similar to modern and fossil bacterial magnetite supporting other evidence that biogenic submicron magnetite is the principal remanence carrier in these sediments in the equatorial pacific ocean low organic carbon burial arrests microbial pore water sulfate reduction thereby aiding preservation of bacterial magnetite

magnetic parameters indicate the intensity of chemical weathering developed on igneous rocks in china abstract continental weathering plays a key role in earth surface processes by linking earth s spheres and producing material for cycling previous studies have proposed numerous weathering indices for the evaluation of chemical weathering intensity however few research efforts are devoted to the changes of sediment physical properties during weathering processes and on the correlations between weathering and mineralogical chemical alteration this study investigates mineral transformation and magnetic properties of two weathering profiles developed on granodiorite and basalt in china the notable differences in magnetic properties between the two profiles i e magnetic susceptibility percentage frequency dependent susceptibility fd anhysteretic remanent magnetization arm and saturation isothermal remnant magnetization sirm are ascribed to the combined effects of parent rock lithology and climate conditions on the formation and alteration of magnetic components during weathering pedogenesis parent rock lithology e g fe bearing basalts and relatively fe poor granites determines the initial magnetic susceptibilities warm and humid climate favors rock weathering and thus enhances the magnetic intensity whereas changes in redox conditions lead to inhomogeneous degree of chemical weathering and thus alter the spatial distribution of magnetic minerals this study further suggests that the weathering intensity in geologic profiles can be evaluated by magnetic indicators such as fd and arm sirm based on their positive correlations with the chemical index of alteration cia the research findings may shed new light on the constraints on continental weathering and detrital sediment cycling in the east asian continental margin

reliable displacement response spectra at long periods in the near field of large earthquakes displacement response spectra defined up to long periods are needed for the design of large structures and to design structures according to displacement based methods the spectra can theoretically be retrieved in the near field of large earthquakes from accelerations recorded by modern strong motion accelerometers difficulties exist due to instrumental limitations long period noise that contaminates the acceleration time histories and record of the tilt simultaneously to the translational accelerations original in this work the effect of the instrument s permanent tilt is investigated and the improvement of the spectra at long periods when the residual tilt is removed from accelerations recorded by modern strong motion seismometers is checked against 1 hz global positioning system gps measurements records of five strong motion accelerometers situated in the near field of the m w 6 8 japanese 2007 niigata ken chuetsu oki earthquake are analyzed in terms of fourier content and displacement response spectra and are then compared to their closest 1 hz gps data the results show that the uncorrected acceleration time histories obtained by simply removing the preevent mean from the raw accelerations recorded by modern strong motion seismometers provide reliable displacement response spectra at periods over 20 s corrected acceleration time histories obtained by removing the permanent tilt from the uncorrected records using the javelaud et al 2011 method may provide reliable response spectra at very long periods until they reach the theoretical peak ground displacement

on baseline corrections and uncertainty in response spectrafor baseline variations commonly encounteredin digital accelerograph records most digital accelerograph recordings are plagued by long period drifts best seen in the velocity and displacement time series obtained from integration of the acceleration time series these drifts often result in velocity values that are nonzero near the end of the record this is clearly unphysical and can lead to inaccurate es timates of peak ground displacement and long period spectral response the source of the long period noise seems to bevariations in the acceleration baseline in many cases these variations could be due to true ground motion tilting and rotation as well as local permanent ground deformation instrumental effects or analog to digital con version very often the trends in velocity are well approximated by a linear trend after the strong shaking subsides the linearity of the trend in velocity implies that no vari ations in the baseline could have occurred after the onset of linearity in the velocity time series this observation combined with the lack of any trends in the pre event motion allows us to compute the time interval in which any baseline variations could occur we then use several models of the variations in a monte carlo procedure to derive a suite of baseline corrected accelerations for each noise model using records from the 1999 chi chi earthquake and several earthquakes in turkey comparisons of the mean values of the peak ground displacements spectral displacements and resid ual displacements computed from these corrected accelerations for the different noise models can be used as a guide to the accuracy of the baseline corrections for many of the records considered here the mean values are similar for each noise model giving confidence in the estimation of the mean values the dispersion of the ground motion measures increases with period and is noise model dependent the dispersion of in elastic spectra is greater than the elastic spectra at short periods but approaches that of the elastic spectra at longer periods the elastic spectra from the most basic proces sing in which only the pre event mean is removed from the acceleration time series do not diverge from the baseline corrected spectra until periods of 10 20 sec or more for the records studied here implying that for many engineering purposes elastic spec tra can be used from records with no baseline correction or filtering

magnetotaxis and acquisition of detrital remanent magnetization by magnetotactic bacteria in natural sediment first experimental results and theory 1 the widespread occurrence of magnetotactic bacteria mtb in several types of marine and freshwater sediment and the role of fossil magnetosomes magnetofossils as main remanent magnetization carriers therein has important paleomagnetic and paleoenvironmental implications despite numerous studies on mtb biology and on magnetofossil preservation in geological records no detailed information is yet available on how magnetotaxis i e the ability to navigate along magnetic field lines is performed in sedimentary environments and on how magnetofossils possibly record the earth magnetic field we provide for the first time experimental evidence for these processes mtb living in sediment are poorly aligned with the geomagnetic field contrary to what is observed in water this can explain the seemingly excessive magnetic moment of most mtb the observed alignment is sufficient for supporting magnetotaxis across the typical thickness of chemical gradients experiments with magnetofossil rich sediment suggest that a natural remanent magnetization nrm is acquired by magnetofossils in the so called benthic mixed layer where natural mtb populations usually occur the acquired nrm is proportional to the applied field at least up to 160 t and its intensity is compatible with values observed in nature for same sediment types therefore if fossil magnetosome chains are not subjected to further alteration by early diagenetic processes they can provide useful relative paleointensities we propose a preliminary model to explain early stages of magnetofossil nrm acquisition as the result of a dynamic equilibrium between magnetic torques and randomizing forces due to sediment mixing

magnetic properties of pelagic marine carbonates abstract pelagic carbonates are deposited far from continents usually at water depths of 3000 6000 m at rates below 10 cm kyr and are a globally important sediment type recent advances with recognition of widespread preservation of biogenic magnetite the inorganic remains of magnetotactic bacteria have fundamentally changed our understanding of the magnetic properties of pelagic carbonates we review evidence for the magnetic minerals typically preserved in pelagic carbonates the effects of magnetic mineral diagenesis on paleomagnetic and environmental magnetic records of pelagic carbonates and what magnetic properties can tell us about the open ocean environments in which pelagic carbonates are deposited we also discuss briefly late diagenetic remagnetisations recorded by some carbonates despite recent advances in our knowledge of these phenomena much remains undiscovered we are only at early stages of understanding how biogenic magnetite gives rise to paleomagnetic signals in sediments and whether it carries a poorly understood biogeochemical remanent magnetisation recently developed techniques have potential for testing how different magnetotactic bacterial species which produce different magnetite morphologies respond to changing nutrient and oxygenation conditions future work needs to test whether it is possible to develop proxies for ancient nutrient conditions from well calibrated modern magnetotactic bacterial occurrences a tantalizing link between giant magnetofossils and paleogene hyperthermal events needs to be tested much remains to be learned about the relationship between climate and the organisms that biomineralised these large and novel magnetite morphologies rather than being a well worn subject that has been studied for over 60 years the magnetic properties of pelagic carbonates hold many secrets that await discovery

comparisons of ground motions from colocated and closely spaced one sample per second global positioning system and accelerograph recordings of the 2003 m 6 5 san simeon california earthquake in the parkfield region the 2003 san simeon california earthquake m 6 5 generated a set of colocated and closely spaced high rate 1 sample per second global positioning system gps positions and ground motions from digital accelerographs in the park field region at epicentral distances of 50 to 70 km the waveforms of displacements derived from the 13 gps receivers in the region have dominant periods between about 7 and 18 sec the waveforms are similar in shape with a systematic change in waveform as a function of distance from the source the gps motions are smaller than the accelerograph motions for periods less than about 2 sec from this we conclude that the 1 sample per sec gps receivers provide a good representation of ground motion at periods longer than about 2 sec perhaps more important for earth quake engineering is that the accelerograph data are similar to the gps data for periods as long as 30 sec if not longer this means that data from digital accelero graphs can provide reliable relative displacement response spectra at the periods needed in the design of large structures at least for earthquakes with magnitudes of 6 5 or above at distances within 70 km we combine the colocated or very closely spaced gps and accelerograph data sets in the frequency domain to obtain a single broadband time series of the ground motion at each accelerograph station these broadband ground motions may be useful to seismologists in unraveling the dynamic process of fault rupture and to engineers for designing large structures with very long period response

quantifying magnetite magnetofossil contributions to sedimentary magnetizations under suitable conditions magnetofossils the inorganic remains of magnetotactic bacteria can contribute to the natural remanent magnetization nrm of sediments in recent years magnetofossils have been shown to be preserved commonly in marine sediments which makes it essential to quantify their importance in palaeomagnetic recording in this study we examine a deep sea sediment core from offshore of northwestern western australia the magnetic mineral assemblage is dominated by continental detritus and magnetite magnetofossils by separating magnetofossil and detrital components based on their different demagnetization characteristics it is possible to quantify their respective contributions to the sedimentary nrm throughout the brunhes chron in the studied core the contribution of magnetofossils to the nrm is controlled by large scale climate changes with their relative importance increasing during glacial periods when detrital inputs were low our results demonstrate that magnetite magnetofossils can dominate sedimentary nrms in settings where they are preserved in significant abundances

a geomagnetic paleointensity record of 0 6 to 3 2 ma from sediments in the western equatorial pacific and remanent magnetization lock in depth