rate of dune reddening in a humid tropical climate the formation of red beds has long interested geologists and pedologists1 3 it has been suggested that the nature and degree of reddening in dune sands can be a useful indicator of the relative age and environmental history of the sands several authors have concluded that dune sands undergo progressive reddening with time4 7 and james and stanley8 considered that coastal dunes might actually be mapped on the basis of colour however quantitative data regarding the rate of reddening in different environmental conditions are generally lacking i present here radiocarbon evidence from north east australia which suggests that red weathering profiles have developed in stabilized dunes of holocene age in humid tropical conditions within the past 7 500 yr

a predictable amo like pattern in the gfdl fully coupled ensemble initialization and decadal forecasting system the decadal predictability of sea surface temperature sst and 2 m air temperature t2m in the geophysical fluid dynamics laboratory gfdl decadal hindcasts which are part of the fifth coupled model intercomparison project experiments has been investigated using an average predictability time apt analysis comparison of retrospective forecasts initialized using the gfdl ensemble coupled data assimilation system with uninitialized historical forcing simulations using the same model allows identification of the internal multidecadal pattern imp for sst and t2m the imp of sst is characterized by an interhemisphere dipole with warm anomalies centered in the north atlantic subpolar gyre region and north pacific subpolar gyre region and cold anomalies centered in the antarctic circumpolar current region the imp of t2m is characterized by a general bipolar seesaw with warm anomalies centered in greenland and cold anomalies centered in antarctica the retrospective prediction skill of the initialized system verified against independent observational datasets indicates that the imp of sst may be predictable up to 4 10 yr lead time at 95 90 significance level and the imp of t2m may be predictable up to 2 10 yr at the 95 90 significance level the initialization of multidecadal variations of northward oceanic heat transport in the north atlantic significantly improves the predictive skill of the imp the dominant roles of oceanic internaldynamicsin decadalpredictionare furtherelucidated byfixed forcing experimentsin which radiative forcing is returned abruptly to 1961 values these results point toward the possibility of meaningful decadal climateoutlooksusingdynamicalcoupledmodelsiftheyareappropriatelyinitializedfromasustainedclimate observing system

orthogonal relation between wavefield polarization and fast s wave direction in the val d agri region an integrating method to investigate rock anisotropy 1 wavefield polarization is investigated using 200 seismograms recorded by a network of 20 stations installed on rock outcrops in the val d agri region that hosts the largest oil fields in the southern apennines italy polarization is assessed both in the frequency and time domains through the individual station horizontal to vertical spectral ratio and covariance matrix analysis respectively we find that most of the stations show a persistent horizontal polarization of waveforms with a ne sw predominant trend this direction is orthogonal to the general trend of quaternary normal faults in the region and to the maximum horizontal stress related to the present extensional regime according to previous studies in other areas such a directional effect is interpreted as due to the presence of fault related fracture fields polarization being orthogonal to their predominant direction a comparison with s wave anisotropy inferred from shear wave splitting indicates an orthogonal relation between horizontal polarization and fast s wave direction this suggests that wavefield polarization and fast velocity direction are effects of the same cause the existence of an anisotropic medium represented by fractured rocks where shear wave velocity is larger in the crack parallel component and compliance is larger perpendicularly to the crack strike the latter is responsible for the observed anisotropic pattern of amplitudes of horizontal ground motion in the study area

how the amoc affects ocean temperatures on decadal to centennial timescales the north atlantic versus an interhemispheric seesaw this study investigates how variations of the atlantic meridional overturning circulation amoc affect sea surface temperature sst within the simulations of the coupled model intercomparison project phase 5 in particular we explore whether the sst response is interhemispheric in nature specifically as reflected in the atlantic sst dipole index or whether the response is localized more in the north atlantic ocean in the absence of direct observational data this dipole index has been proposed to approximate amoc variations over the duration of the instrumental temperature record we find that typically on timescales between decadal and centennial the sst dipole index correlates with the amoc with coefficients ranging from 0 2 to 0 7 typically with a 0 6 year lag and thus explains less than half of the amoc variance in just two models this value slightly exceeds 50 even for the models with the highest correspondence between the amoc and the dipole index the correlation between the two variables is controlled mainly by sst variations in the north atlantic not the south atlantic both for the model control and historical simulations consequently in nearly all models the north atlantic sst provides a better indicator of amoc variations than the atlantic dipole thus on decadal to centennial timescales amoc variability affects mainly the north atlantic ocean with the sensitivity of the north atlantic sst between 40 and 60 n given by the multi model average of about 0 3 c per 1 sv of amoc change explaining roughly one third of the sst variance

does external forcing interfere with the amoc s influence on north atlantic sea surface temperature abstractnumerous studies have suggested that variations in the strength of the atlantic meridional overturning circulation amoc may drive predictable variations in north atlantic sea surface temperature nasst however two recent studies have presented results suggesting that coupled models disagree on both the sign and the phasing of the correlation between amoc and nasst indices these studies analyzed linearly detrended output from twentieth century historical simulations in phases 3 and 5 of the coupled model intercomparison project cmip3 and cmip5 the present study argues that the apparent disagreement among models arises from a comingling of two processes 1 a bottom up effect in which unforced amoc changes lead to nasst changes of the same sign and 2 a top down effect in which forced nasst changes lead to amoc changes of the opposite sign linear detrending is not appropriate for separating these two effects because the time scales of forced and unforced variations are not well separated

evidences for strong directional resonances in intensely deformed zones of the pernicana fault mount etna italy 1 in this paper we investigate ground motion properties in the western part of the pernicana fault this is the major fault of mount etna and drives the dynamic evolution of the area in a previous work rigano et al 2008 showed that a significant horizontal polarization characterizes ground motion in fault zones of mount etna both during earthquakes and ambient vibrations we have performed denser microtremor measurements in the ne rift segment and in intensely deformed zones of the pernicana fault at piano pernicana this study includes mapping of azimuth dependent horizontal to vertical spectral ratios along and across the fault frequency wave number techniques applied to array data to investigate the nature of ambient vibrations and polarization analysis through the conventional covariance matrix method our results indicate that microtremors are likely composed of volcanic tremor spectral ratios show strong directional resonances of horizontal components around 1 hz when measurements enter the most damaged part of the fault zone their polarization directions show an abrupt change by 20 to 40 at close measurements between the northern and southern part of the fault zone recordings of local earthquakes at one site in the fault zone confirm the occurrence of polarization with the same angle found using volcanic tremor we have also found that the directional effect is not time dependent at least at a seasonal scale this observation and the similar behavior of volcanic tremors and earthquake induced ground motions suggest that horizontal polarization is the effect of local fault properties however the 1 hz resonant frequency cannot be reproduced using the 1 d vertically varying model inferred from the array data analysis suggesting a role of lateral variations of the fault zone although the actual cause of polarization is unknown a role of stress induced anisotropy and microfracture orientation in the near surface lavas of the pernicana fault can be hypothesized consistently with the sharp rotation of the polarization angle within the damaged fault zone

directivity of slope dynamic response to seismic shaking 1 a four year long accelerometric monitoring of a landslide prone slope area in italy provided evidence of amplifications with systematic directional differences in shaking energy by a factor of 2 3 apparently correlated with the directions of local topographic features the examination of regional scale data revealed similar site response directivity phenomena also on some steep rock slopes not affected by amplification the spectral properties of the site responses were investigated using hvsr analysis and a new approach based on the multiplication of spectra from several events the results suggest that such phenomena are caused by a directional redistribution of spectral energy controlled by a combination of interrelated topographic and geologic factors acting in similar directions

does the atlantic multidecadal oscillation get its predictability from the atlantic meridional overturning circulation abstractthis paper investigates the predictive relation between the atlantic multidecadal oscillation amo and atlantic meridional overturning circulation across different climate models three overturning patterns that are significantly coupled to the amo on interannual time scales across all climate models are identified using a statistical optimization technique including these structures in an autoregressive model extends amo predictability by 2 9 years relative to an autoregressive model without these structures

thermoluminescence dating of quaternary red sand beds a case study of coastal dunes in sri lanka red sand beds that occupy extensive tracts of coastal humid tropics have conventionally been considered undatable results of a first successful attempt to provide an absolute chronology to these sediments based on thermoluminescence dosimetry are presented along with a discussion on the importance of an understanding of ambient geochemistry in the application of the thermoluminescence technique the results on the sri lankan coastal region indicate that the sea level in the region may have been affected by regional tectonics during the past 70 000 years based on in situ finds of geometric microliths in the red sands a date of ca 25 000 years is ascribed to them suggesting them to be substantially older than believed so far

simulated variability of the circulation in the north atlantic from 1953 to 2003 abstract the variability of the circulation in the north atlantic and its link with atmospheric variability are investigated in a realistic hindcast simulation from 1953 to 2003 the interannual to decadal variability of the subpolar gyre circulation and the meridional overturning circulation moc is mostly influenced by the north atlantic oscillation nao both circulations intensified from the early 1970s to the mid 1990s and then decreased the monthly variability of both circulations reflects the fast barotropic adjustment to nao related ekman pumping anomalies while the interannual to decadal variability is due to the baroclinic adjustment to ekman pumping buoyancy forcing and dense water formation consistent with previous studies an original characteristic of the oceanic response to nao is presented that relates to the spatial patterns of buoyancy and wind forcing over the north atlantic anomalous ekman pumping associated with a positive nao phase first induces a decrease of the southern sub

interdecadal variations of the thermohaline circulation in a coupled ocean atmosphere model abstract a fully coupled ocean atmosphere model is shown to have irregular oscillations of the thermohaline circulation in the north atlantic ocean with a time scale of approximately 50 years the irregular oscillation appears to be driven by density anomalies in the sinking region of the thermohaline circulation approximately 52 n to 72 n combined with much smaller density anomalies of opposite sign in the broad rising region the spatial pattern of see surface temperature anomalies associated with this irregular oscillation bears an encouraging resemblance to a pattern of observed interdecadal variability in the north atlantic the anomalies of sea surface temperature induce model surface air temperature anomalies over the northern north atlantic arctic and northwestern europe

observed decadal north atlantic tripole sst variability part ii diagnosis of mechanisms abstractin part i of this study the atmospheric weather noise for 1951 2000 was inferred from an atmospheric analysis in conjunction with sst forced agcm simulations and used to force interactive ensemble coupled gcm simulations of the north atlantic sst variability here results from those calculations are used in conjunction with a simple stochastically forced coupled model of the decadal time scale north atlantic tripole sst variability to examine the mechanisms associated with the tripole sst variability the diagnosed tripole variability is found to be characterized by damped delayed oscillator dynamics similar to what has been found by other investigators however major differences here affecting the signs of two of the crucial parameters of the simple model are that the atmospheric heat flux feedback damps the tripole pattern and that a counterclockwise intergyre gyre like circulation enhances the tripole pattern delayed oscillator dynamics are still obtained because the sign of the dynamic

hydrodynamic and suspended sediment transport controls on river mouth morphology 1 river mouths building into standing bodies of water have strikingly varied growth habits this presents a compelling pattern formation problem that is also of great practical relevance for subsurface prediction and managing coastal wetlands here we present a generalized 2 5 dimensional potential vorticity pv theory that explains sedimentation patterns of a sediment laden stationary jet by coupling an understanding of vorticity with suspended sediment concentration fields we explore the physical meaning of this new sediment pv definition and its impact on outflow depositional patterns by analyzing data from a shallow wall bounded plane jet experiment and by discussing new theoretical insights a key result is that lateral advection and diffusion of suspended sediment are directly proportional to jet vorticity a feature that reveals the mechanistic process that forms elongated channels by focused levee deposition the new pv theory constitutes a more generalized mathematical framework that expands the rouse theory for the equilibrium of suspended sediment

the little red hill seismic experimental study topographic effects on ground motion at a bedrock dominated mountain edifice the kinematic response of a bedrock dominated mountain edifice to seismic shaking near lake coleridge in the southern alps of new zealand was examined a small elongated and bedrock dominated mountain ridge little red hill was equipped with a seismic array seven earss instruments mark l 4 3d seismometers were installed along the ridge crest the flank and at the base of the 210 m high 500 m wide and 800 m long mountain edifice from february to july 2006 seismic records of local and regional earthquakes were used to provide information on amplification and deamplification effects as well as on the frequency response at different parts on the edifice the ground motion records were analyzed using three different methods comparisons of peak ground accelerations power spectral density analysis and standard spectral ratio analysis time and frequency domain analyses show that site amplification is concentrated along the elongated crest of the edifice where amplifications of up to 1100 were measured relative to the motion at the flat base the field experiment also highlighted the extreme variations in amplification with regard to closely located sites but at contrasting topographic locations theoretical calculations and frequency analyses of field data indicate a maximum response along the ridge crest of little red hill for frequencies of about 5 hz which correlate to wavelengths approximately equal to the half width or height of the edifice the consequence of amplification effects on the stability and degradation of rock masses can be seen areas showing high amplification effects overlap with the spatial distribution of seismically generated block fields at little red hill it is concluded that topography geometry and distance to the seismic source play key roles in causing amplification effects of seismic ground motion and supporting dilation and degradation of rock mass across bedrock dominated mountain edifices

horizontal polarization of ground motion in the hayward fault zone at fremont california dominant fault high angle polarization and fault induced cracks summary we investigate shear wave polarization in the hayward fault zone near niles canyon fremont ca waveforms of 12 earthquakes recorded by a seven accelerometer seismic array around the fault are analysed to clarify directional site effects in the fault damage zone the analysis is performed in the frequency domain through h v spectral ratios with horizontal components rotated from 0 to 180 and in the time domain using the eigenvectors and eigenvalues of the covariance matrix method employing three component records the near fault ground motion tends to be polarized in the horizontal plane at two on fault stations where the local strike is n160 ground motion polarization is oriented n88 19 and n83 32 respectively at a third on fault station the motion is more complex with horizontal polarization varying in different frequency bands however a polarization of n86 7 similar to the results at the other two on fault stations is found in the frequency band 6 8 hz the predominantly high angle polarization from the fault strike at the hayward fault is consistent with similar results at the parkfield section of the san andreas fault and the val d agri area a quaternary extensional basin in italy in all these cases comparisons of the observed polarization directions with models of fracture orientation based on the fault movement indicate that the dominant horizontal polarization is near orthogonal to the orientation of the expected predominant cracking direction the results help to develop improved connections between fault mechanics and near fault ground motion

effects of realistic surface topography on seismic ground motion in the yangminshan region of taiwan based upon the spectral element method and lidar dtm we combine light detection and ranging lidar digital terrain model dtm data and an improved mesh implementation to investigate the effects of high resolution surface topography on seismic ground motion based upon the spectral element method in general topography increases the amplitude of shaking at mountain tops and ridges whereas valleys usually have reduced ground motion as has been observed in both records from past earthquakes and numerical simulations however the effects of realistic topography on ground motion have not often been clearly characterized in numerical simulations especially the seismic response of the true ground surface here we use lidar dtm data which provide two meter reso lution at the free surface and a spectral element method to simulate three dimensional 3d seismic wave propagation in the yangminshan region in taiwan incorporating the effects of realistic topography a smoothed topographic map is employed beneath the model surface in order to decrease mesh distortions due to steep ground surfaces numerical simulations show that seismic shaking in mountainous areas is strongly affected by topography and source frequency content the amplification of ground motion mainly occurs at the tops of hills and ridges whilst the valleys and flat topped hills experience lower levels of ground shaking interaction between small scale to pographic features and high frequency surface waves can produce unusually strong shaking we demonstrate that topographic variations can change peak ground accel eration pga values by 50 in mountainous areas and the relative change in pga between a valley and a ridge can be as high as a factor of 2 compared to a flat surface response this suggests that high resolution realistic topographic features should be taken into account in seismic hazard analysis especially for densely populated moun tainous areas

interdecadal variations in north atlantic sea surface temperature and associated atmospheric conditions abstract evidence is presented for a distinct pattern of ocean atmosphere relationship associated with interdecadal variability in the north atlantic region using a century of surface marine observations it is shown that middle and high latitude sea surface temperature sst display a long term fluctuation with negative anomalies before 1920 and during the 1970s and 1980s positive sst conditions prevailed from about 1930 to 1960 the pattern of interdecadal sst variability is constructed by subtracting the average field during 15 cold years from that during a similar interval of warm years the early century warming and the more recent cooling display a similar spatial pattern in both cases the pattern is basin scale and largely of one polarity with maxima in the vicinity of iceland in the labrador sea and northeast of bermuda the corresponding differences in surface atmospheric conditions are determined by averaging and subtracting in the same manner fields of sea level pressure slp and surf

ground motion amplitude across ridges abstract local amplification and wave diffraction on an elongated ridge near sourpi in central greece were studied by the analysis of seismic records of local and regional earthquakes data were obtained during field work especially designed for this purpose these data were analyzed in the frequency and time domains in the frequency domain spectral ratios show amplifications of 1 5 to 3 at the ridge top relative to the base of the ridge the horizontal components of motion are more amplified than the vertical component and the observed spectral ratios seem stable for different earthquake locations theoretical spectral ratios calculated by the indirect boundary element method are dependent on earthquake location but are in general agreement with the observed spectral ratios another dataset from mont st eynard in the french alps showed similar characteristics with spectral amplitudes on the top of the ridge up to four times those on the flank these relative amplifications are within the range predicted by numerical simulations the numerical simulations also show that the topographic effect involves the emission of diffracted waves propagating from the top toward the base of the ridge the use of a seven station array on the ridge at sourpi made it possible to identify such waves the analysis was performed with wave separation methods using singular value decomposition and spectral matrix filtering our results show agreement between experimental data and theoretical results supporting the use of numerical simulations for estimation of purely topography induced amplification on ridge tops our results also show that such amplification is moderate for the ridges under study

an experimental approach for estimating seismic amplification effects at the top of a ridge and the implication for ground motion predictions the case of narni central italy abstract from march to september 2009 a velocimetric network was installed in narni central italy a village on the top of a limestone ridge the aim was to investigate local site effects due to the 220 m high ridge which is characterized by slopes ranging from 22 to 35 to investigate amplification without and with a reference site three stations were installed at the base of the hill and seven at the crest the network recorded 702 earthquakes many of them from the 2009 l aquila sequence to determine the dependence of amplification on the morphological features the spectra were computed for horizontal components rotated into a range of azimuths both the ratio of the horizontal to vertical component spectra and the ratio of the spectra at the ridge crest with respect to a reference station at the base of the ridge showed amplification by a factor of circa 4 5 for frequencies between 4 hz and 5 hz the highest amplifications were seen for the directions of the ground motion perpendicular to the main elongation of the ridge finally considering events with an epicentral distance less than 30 km empirical ground motion models were calibrated for maximum horizontal peak ground acceleration pga velocity and acceleration response spectra 5 damping up to 1 s to estimate the site corrective coefficients for topographic amplification the data show corrective coefficients between 0 35 and 0 48 log 10 scale amplification 2 2 3 0 for the spectral ordinates between 0 2 s and 0 3 s

north atlantic climate model bias influence on multiyear predictability abstract the influences of north atlantic biases on multiyear predictability of unforced surface air temperature sat variability are examined in the kiel climate model kcm by employing a freshwater flux correction over the north atlantic to the model which strongly alleviates both north atlantic sea surface salinity sss and sea surface temperature sst biases the freshwater flux corrected integration depicts significantly enhanced multiyear sat predictability in the north atlantic sector in comparison to the uncorrected one the enhanced sat predictability in the corrected integration is due to a stronger and more variable atlantic meridional overturning circulation amoc and its enhanced influence on north atlantic sst results obtained from preindustrial control integrations of models participating in the coupled model intercomparison project phase 5 cmip5 support the findings obtained from the kcm models with large north atlantic biases tend to have a weak amoc influence on sat and exhibit a smaller sat predictability over the north atlantic sector

assessment of site effects in alpine regions through systematic site characterization of seismic stations abstract in the framework of the renewal project of the swiss strong motion network ssmnet a procedure for site characterization has been established the aim of the procedure was to systematically derive realistic 1d velocity profiles at each station it is mainly based on the analysis of surface waves particularly from passive experiments and includes cross checks of the derived amplification functions with those obtained through spectral modeling of recorded earthquakes the systematic use of three component surface wave analysis allowing the derivation of both rayleigh and love dispersion curves also contributes to the improvement of the quality of the retrieved profiles the procedure is applied to the 30 ssmnet stations installed on various site types within the project covering different aspects of seismic risk the characterization of these 30 sites gives an overview of the variety of possible effects of surface geology on ground motion in the alpine area such effects ranged from deamplification at hard rock sites to amplification up to a factor of 15 in lacustrine sediments with respect to the swiss reference rock velocity model the derived velocity profiles are shown to reproduce observed amplification functions from empirical spectral modeling although many sites are found to exhibit 1d behavior the procedure allows the detection and qualification of 2d and 3d effects the sites are therefore classified with respect to the occurrence of 2d 3d resonance and edge generated surface waves in addition to the large and deeply incised alpine valleys of the rhone the rhine and the aar smaller structures such as local alpine valleys and alluvial fans are shown to exhibit 2d 3d behavior

localized damage caused by topographic amplification during the 2010 m 7 0 haiti earthquake microzonation maps use local geological conditions to characterize seismic hazard but do not generally consider topography ground motions during the haiti earthquake are found to have been significantly amplified along a high topographic ridge which caused substantial structural damage indicating that topography can play an important role in seismic hazard local geological conditions including both near surface sedimentary layers1 2 3 4 and topographic features5 6 7 8 9 are known to significantly influence ground motions caused by earthquakes microzonation maps use local geological conditions to characterize seismic hazard but commonly incorporate the effect of only sedimentary layers10 11 12 microzonation does not take into account local topography because significant topographic amplification is assumed to be rare here we show that although the extent of structural damage in the 2010 haiti earthquake was primarily due to poor construction topographic amplification contributed significantly to damage in the district of petionville south of central port au prince a large number of substantial relatively well built structures situated along a foothill ridge in this district sustained serious damage or collapse using recordings of aftershocks we calculate the ground motion response at two seismic stations along the topographic ridge and at two stations in the adjacent valley ground motions on the ridge are amplified relative to both sites in the valley and a hard rock reference site and thus cannot be explained by sediment induced amplification instead the amplitude and predominant frequencies of ground motion indicate the amplification of seismic waves by a narrow steep ridge we suggest that microzonation maps can potentially be significantly improved by incorporation of topographic effects

a tree ring based reconstruction of the atlantic multidecadal oscillation since 1567 a d 1 we present a tree ring based reconstruction of the atlantic multidecadal oscillation amo which demonstrates that strong low frequency 60 100 yr variability in basin wide 0 70 n sea surface temperatures ssts has been a consistent feature of north atlantic climate for the past five centuries intervention analysis of reconstructed amo indicates that 20th century modes were similar to those in the preceding 350 yr and wavelet spectra show robust multidecadal oscillations throughout the reconstruction though the exact relationships between low frequency sst modes higher frequency 7 25 yr atmospheric modes e g north atlantic oscillation arctic oscillation and terrestrial climates must still be resolved our results confirm that the amo should be considered in assessments of past and future northern hemisphere climates

atlantic multidecadal oceanic variability and its influence on the atmosphere in a climate model the mechanisms controlling the decadal to multidecadal variability of the atlantic meridional overturning circulation moc and its influence on the atmosphere are investigated using a control simulation with the ipsl cm4 climate model the multidecadal fluctuations of the moc are mostly driven by deep convection in the subpolar gyre which occurs south of iceland in the model the latter is primarily influenced by the anomalous advection of salinity due to changes in the east atlantic pattern eap which is the second mode of atmospheric variability in the north atlantic region the north atlantic oscillation is the dominant mode but it plays a secondary role in the moc fluctuations during summer the moc variability is shown to have a significant impact on the atmosphere in the north atlantic european sector the moc influence is due to an interhemispheric sea surface temperature sst anomaly with opposite signs in the two hemispheres but largest amplitude in the northern one the sst pattern driven by the moc mostly resembles the model atlantic multidecadal oscillation amo and bears some similarity with the observed one it is shown that the amo reflects both the moc influence and the local atmospheric forcing hence the moc influence on climate is best detected using lagged relations between climatic fields the atmospheric response resembles the eap in a phase that might induce a weak positive feedback on the moc

early silica diagenetic fabrics in late quaternary sediments south india late pleistocene aeolian and marine sediments on the coastal plain of south india show extensive evidence of very early diagenetic change that has involved the leaching of original carbonates and subsequent lithification of the sediments by opal a the diagenesis is closely associated with both intense pedological weathering of the sands in the vadose environment and the former presence of roots silica rhizoliths petrifactions and micro petrifactions are major components of the diagenetic fabric together with pore filling opaline silica precipitates three distinct fabric types can be identified within the diagenetic profile an upper deeply weathered fabric with a matrix of clays and iron oxides and limited preservation of silica petrifactions and clay root cutans tubules a mid profile mottled fabric having a distinctive high porosity and in which well preserved silica petrifactions and micro petrifactions are best developed together with opaline silica cements and clay root cutans and a lower profile fabric in which less common silica petrifactions occur within carbonate cemented sediments the early diagenetic fabrics the first described of their kind provide evidence of widespread and rapid silicification of organic matter in a vadose seasonally moist tropical weathering environment as such they have potentially important implications for the interpretation of silica diagenesis in the terrestrial geological record

a decadal prediction case study late twentieth century north atlantic ocean heat content an ensemble of initialized decadal prediction dp experiments using the community climate system model version 4 ccsm4 shows considerable skill at forecasting changes in north atlantic upper ocean heat content and surface temperature up to a decade in advance coupled model ensembles were integrated forward from each of 10 different start dates spanning from 1961 to 2006 with ocean and sea ice initial conditions obtained from a forced historical experiment a coordinated ocean ice reference experiment with interannual forcing core ia which exhibits good correspondence with late twentieth century ocean observations from the north atlantic subpolar gyre spg region north atlantic heat content anomalies from the dp ensemble correlate highly with those from the core ia simulation after correcting for a drift bias in particular theobservedlarge rapid rise in spgheatcontentin themid 1990sis successfullypredicted in the ensemble initialized in january of 1991 a budget of spg heat content from the core ia experiment sheds light on the origins of the 1990s regime shift and it demonstrates the extent to which low frequency changes in ocean heat advection related to the atlantic meridional overturning circulation dominate temperature tendencies in this region similar budgets from the dp ensembles reveal varying degrees of predictive skill in the individual heat budget terms with large advective heat flux anomalies from the south exhibiting the highest correlation with core ia the skill of the dp in this region is thus tied to correct initialization of ocean circulation anomalies while external forcing is found to contribute negligibly and for incorrect reasons to predictive skill in this region over this time period

instrumental evidence of normal mode rock slope vibration summary a unique field experiment was performed to constrain the seismic response of a large potentially unstable rock slope in the southern swiss alps small aperture seismic arrays were deployed to record ambient vibrations both inside and outside of the mapped instability boundary the recordings were analysed by means of the high resolution f k method site to reference spectral ratios and time frequency dependent polarization analysis all three methods indicated that the wavefield within the potentially unstable rock mass is dominated by normal mode motion standing waves rather than horizontal propagation of seismic waves both fundamental frequency and relative amplification could be recovered from ambient noise data the observed amplification is strongly directional and the maximum amplification is oriented perpendicular to open tension cracks mapped at the ground surface our results highlight site response characteristics relevant for analysis of earthquake triggered rock slope failures

topographic effects on the hill of nocera umbra central italy summary during the m w 5 7 and 6 0 umbria marche earthquakes of 1997 september 26 the historical centre of nocera umbra suffered mcs intensity vii viii the zone is located on the top of a hill a condition potentially favourable to ground motion amplification however also vulnerability is higher on the hill because of the ancient age of buildings a temporary array of eight seismological stations was installed across the hill to quantify the amplification effect due to topography waveforms of 14 aftershocks 2 6 m l 4 1 are selected for the analysis during each earthquake the largest amplitudes are observed on the hilltop spectral ratios are computed using rotated horizontal components to search for directional effects amplifications are found in two separate frequency bands one in the range 2 4 hz where the increase of amplitude is moderate never exceeding a factor of 4 and the polarization is transversal to the hill major axis the second above 10 hz where amplifications are larger and reach values as high as 25 hz high frequency polarization varies for different sites and frequencies suggesting that smaller scale complexities control the high frequency response synthetic seismograms of 2 d models confirm the occurrence of amplification although not all details are fit by numerical simulations and the agreement between observations and models is significant only in terms of the fundamental resonance frequency around 3 hz in the models amplifications are much smaller than the observed ones we conclude that topography could have been responsible for a small increase of damage in the hill zone but the most significant role on damage was played by the locally higher vulnerability

soil chronosequence development in dunes on the southeast african coastal plain maputaland south africa abstract dunes have accreted on the southeast african coastal plain in coast parallel patterns of degraded whaleback ridges sand megaridges and extended parabolic dunes since the pliocene in the maputaland dune field relative dating is complicated by soil degradation erosion and vegetation cover this project assessed alternative relative and numeric dating techniques that can be used to differentiate dune systems and eolian sand bodies soil profile characteristics were used to calculate soil development indices sdi for soil horizons sampled from hand augered holes and rare exposures infrared stimulated luminescence irsl dating of representative dunes and sand units helped define the pedogenesis achieved since deposition the quartzose dune sands have weathered to form very deep soil profiles enhanced sdi values for horizons or sampled intervals down the profile reflect ph decrease advanced rubification or distinct mottling clay increase and harder consistency with depth the youngest holocene profiles exhibit decreasing horizon index values with depth below the a horizon whereas late pleistocene profiles display sdi values increasing with depth within the upper 3 m of the profile within some mid to late pleistocene eolian sands greater profile horizonation and catena complexity manifests as complex soil profiles or distinctly mottled clay enriched horizons at depths of 2 5 m below the surface the sdi profiles from specific dune systems or stratigraphic units cluster well and effectively characterize soil development in dune sand units of different ages depositional age plotted against sampled horizon index values makes it possible to determine generalized rates of soil profile development and to compare pedogenic processes on the high rainfall coastal barrier dunes to those found in the drier interior sampled horizon index values distinguish buried soil profiles and highlight possible localized surficial reworking

multidecadal north atlantic sea surface temperature and atlantic meridional overturning circulation variability in cmip5 historical simulations received 22 may 2013 revised 4 september 2013 accepted 8 september 2013 published 23 october 2013 1 in this paper simulated variability of the atlantic multidecadal oscillation amo and the atlantic meridional overturning circulation amoc and their relationship has been investigated for the first time climate models of the coupled model intercomparison project phase 5 cmip5 provided to the intergovernmental panel on climate change fifth assessment report ipcc ar5 in historical simulations have been used for this purpose the models show the most energetic variability on the multidecadal timescale band both with respect to the amo and amoc but with a large model spread in both amplitude and frequency the relationship between the amo and amoc in most of the models resembles the delayed advective oscillation proposed for the amoc on multidecadal timescales a speed up slow down of the amoc is in favor of generating a warm cold phase of the amo by the anomalous northward southward heat transport in the upper ocean which reversely leads to a weakening strengthening of the amoc through changes in the meridional density gradient after a delayed time of ocean adjustment this suggests that on multidecadal timescales the amo and amoc are related and interact with each other

frequency domain multimodel analysis of the response of atlantic meridional overturning circulation to surface forcing the dynamics of the atlantic meridional overturning circulation amoc vary considerably among different climate models for example some models show clear peaks in their power spectra while others do not to elucidate these model differences transfer functions are used to estimate the frequency domain relationship between surface forcing fields including sea surface temperature salinity and wind stress and the resulting amoc response these are estimated from the outputs of the coupled model intercomparison project phase 5 cmip5 and phase 3 cmip3 control runs for eightdifferent models with a specificfocus on geophysical fluid dynamics laboratory climate model version 2 1 gfdl cm2 1 and the community climate system model version 4 ccsm4 which exhibit rather different spectral behavior the transfer functionsshowvery littleagreement amongmodelsforany ofthe pairsofvariablesconsidered suggestingthe existence of systematic model errors and that considerable uncertainty in the simulation of amoc in current climate models remains however a robust feature of the frequency domain analysis is that models with spectral peaks in their amoc correspond to those in which amoc variability is more strongly excited by high latitude surface perturbations that have periods corresponding to the frequency of the spectral peaks this explains why different models exhibit such different amoc variability these differences would not be evident without using a method that explicitly computes the frequency dependence rather than a priori assuming a particular functional form finally transfer functions are used to evaluate two proposed physical mechanisms for model differences in amoc variability differences in labrador sea stratification and excitation by westward propagating subsurface rossby waves

a predictability study of simulated north atlantic multidecadal variability the north atlantic is one of the few places on the globe where the atmosphere is linked to the deep ocean through air sea interaction while the internal variability of the atmosphere by itself is only predictable over a period of one to two weeks climate variations are potentially predictable for much longer periods of months or even years because of coupling with the ocean this work presents details from the first study to quantify the predictability for simulated multidecadal climate variability over the north atlantic the model used for this purpose is the gfdl coupled ocean atmosphere climate model used extensively for studies of global warming and natural climate variability this model contains fluctuations of the north atlantic and high latitude oceanic circulation with variability concentrated in the 40 60 year range oceanic predictability is quantified through analysis of the time dependent behavior of large scale empirical orthogonal function eof patterns for the meridional stream function dynamic topography 170 m temperature surface temperature and surface salinity the results indicate that predictability in the north atlantic depends on three main physical mechanisms the first involves the oceanic deep convection in the subpolar region which acts to integrate atmospheric fluctuations thus providing for a red noise oceanic response as elaborated by hasselmann the second involves the large scale dynamics of the thermohaline circulation which can cause the oceanic variations to have an oscillatory character on the multidecadal time scale the third involves nonlocal effects on the north atlantic arising from periodic anomalous fresh water transport advecting southward from the polar regions in the east greenland current when the multidecadal oscillatory variations of the thermohaline circulation are active the first and second eof patterns for the north atlantic dynamic topography have predictability time scales on the order of 10 20 y whereas eof 1 of sst has predictability time scales of 5 7 y when the thermohaline variability has weak multidecadal power the hasselmann mechanism is dominant and the predictability is reduced by at least a factor of two when the third mechanism is in an extreme phase the north atlantic dynamic topography patterns realize a 10 20 year predictability time scale additional analysis of sst in the greenland sea in a region associated with the southward propagating fresh water anomalies indicates the potential for decadal scale predictability for this high latitude region as well the model calculations also allow insight into regional variations of predictability which might be useful information for the design of a monitoring system for the north atlantic predictability appears to break down most rapidly in regions of active convection in the high latitude regions of the north atlantic

azimuth dependent amplification of weak and strong ground motions within a fault zone nocera umbra central italy 1 during three moderate magnitude earthquakes occurred in september october 1997 in the central apennines italy accelerations larger than 0 5 g were recorded in the town of nocera umbra 10 to 15 km n nw of the epicenters the accelerograph is sited in a fault zone close to a n30 e tectonic contact six temporary seismological stations installed across the fault recorded 82 aftershocks occurred in two seismogenic zones the colfiorito sellano area s se of the array and the gualdo tadino area to the north the array data reveal large variations in terms of both peak ground motions and spectral amplitudes within the fault zone amplifications show a strong dependence on the source azimuth at the accelerograph site the effects are particularly large for events from s se peak ground motions are a factor of 14 larger than those of a reference site and conventional spectral ratios attain amplitudes as large as 50 at 7 hz along the n30 e direction of motion parallel to the strike of the fault nineteen strong motion accelerograms were then used to compare ground motion properties between weak and strong events up to m 0 1 2 x 10 25 dyn cm a particle motion analysis shows that the directional effect is also present in the strongest motions even though the amplification of peak ground motion decreases when m 0 increases results from stochastic simulations indicate that such a behavior is not due to nonlinearity applying the empirical weak motion transfer functions in a purely linear model the observed peak ground motions of the largest events are fit satisfactorily

high accelerations produced by the western nagano prefecture japan earthquake of 1984 many boulders were thrown out of their former sockets by the western nagano prefecture japan earthquake of 1984 mjma 6 8 the anomalous high accelerations of 4 16 g were estimated from the displacement of thrown out boulders assuming that the seismic waves had a frequency range of 5 10 hz almost all of the thrown out boulders were found on the mountain tops ridges and saddles the topographic amplifications of seismic waves were estimated using five aftershocks recorded on the mountain top and at the foot average amplitude ratios mountain top foot of seismic waves are 2 7 in the frequency range concerned the high acceleration area defined by the distribution of thrown out boulders is very small 1 3 km compared with the length 12 km of the assumed main fault many cracks were also found in this limited small area which is characterized by extremely low activity of aftershocks and relatively large dislocation

reddening of dune sands evidence from southeast india thin section sem and tem analyses have indicated that the red teri sands of southeast india have formed from weathering in situ of coastal dune sands the data does not support a detrital origin for the red sands c14 dates indicate that dune deposition and weathering to a maximum depth of 10 m leading to the formation of a hematite koalinite and illite rich matrix has taken place rapidly over the past 25 000 years it is postulated that garnet was a major source of hematite ferric oxide

off fault ground ruptures in the santa cruz mountains california ridge top spreading versus tectonic extension during the 1989 loma prieta earthquake the ms 7 1 loma prieta earthquake of 18 october 1989 produced abundant ground ruptures in an 8 by 4 km area along summit road and skyland ridge in the santa cruz mountains predominantly extensional fissures formed a left stepping crudely en echelon pattern along ridges of the hanging wall block southwest of the san andreas fault about 12 km northwest of the epicenter the fissures are subparallel to the san andreas fault and appear to be controlled by bedding planes faults joints and other weak zones in the underlying tertiary sedimentary strata of the hanging wall block the pattern of extensional fissures is generally consistent with tectonic extension across the crest of the uplifted hanging wall block also many displacements in laurel creek canyon and along the san andreas and sargent faults are consistent with right lateral reverse faulting inferred for the mainshock additional small tensile failures along the axis of the laurel anticline may reflect growth of the fold during deep seated compression however the larger ridge top fissures commonly have displacements that are parallel to the north northeast regional slope directions and appear inconsistent with east northeast extension expected from this earthquake measured cumulative displacements across the ridge crests are at least 35 times larger than that predicted by the geodetically determined surface deformation these fissures also occur in association with ubiquitous landslide complexes that were reactivated by the earthquake to produce the largest concentration of co seismic slope failures in the epicentral region the anomalously large displacements and the apparent slope control of the geometry and displacement of many co seismic surface ruptures lead us to conclude that gravity is an important driving force in the formation of the ridge top fissures shaking induced gravitational spreading of ridges and downslope movement may account for 90 or more of the observed displacements on the linear fissures similar fissures occurred in the same area and elsewhere near the san andreas fault during the predominantly right lateral 1906 san francisco earthquake and suggest that the loma prieta ground ruptures may in large part be independent of fault kinematics

fracture related wavefield polarization and seismic anisotropy across the greendale fault we investigate seismic signatures of fracturing in a newly ruptured strike slip fault by determining the wavefield polarization in the new zealand canterbury plains area and across the greendale fault which was responsible for the 3 september 2010 darfield mw 7 1 earthquake previous studies suggested that fractured rocks in fault damage zones cause directional amplification and ground motion polarization in the fracture perpendicular direction as an effect of stiffness anisotropy and cause velocity anisotropy with shear wave velocity larger in the fracture parallel component an array of 14 stations was installed following the darfield earthquake we assess polarization both in the frequency and time domains through the individual station horizontal to vertical spectral ratio and covariance matrix analysis respectively and compare the results to previously reported anisotropy measurements from shear wave splitting stations installed in the canterbury plains have an amplification peak between 0 1 and 0 3 hz for both earthquakes and ambient noise we relate the amplification to the resonance of a considerable thickness c 1 km of soft sediments lying over the metamorphic bedrock analysis of seismic events revealed the existence of another peak in amplification between 2 and 5 hz at two on fault stations which was not visible in the noise analysis in contrast to the lower frequency peak the ones between 2 and 5 hz are more strongly anisotropic attaining amplitudes up to a factor of 4 in the n52 direction to interpret this effect we model the fracture pattern in the fault damage zone produced by the fault kinematics we conclude that the horizontal polarization is orthogonal to extensional fractures which predominate in the shallow layers 2 km expected in n101 direction on the basis of the model thus different fracture distribution at different depths may explain different results for amplification compared to anisotropy we propose polarization amplification analysis as a complementary method to s wave splitting analysis polarization analysis is rapidly computed and robust and it can be applied to either earthquakes or ambient noise recordings giving useful information about the predominant fracture patterns at various depths

ground motion in the presence of complex topography earthquake and ambient noise sources to study the influence of topography on ground motion eight seismic recorders were deployed for a period of one year over poverty ridge on the east side of the san francisco bay area california this location is desirable because of its proximity to local earthquake sources and the significant topographic relief of the array 439 m topographic amplification is evaluated as a function offrequency using a variety of methods including reference site based spectral ratios and single station horizontal to vertical spectral ratios using both shear waves from earthquakes and ambient noise field observations are compared with the predicted ground motion from an accurate digital model of the topography and a 3d local velocity model amplification factors from the theoretical calculations are consistent with observa tions the fundamental resonance of the ridge is prominently observed in the spectra of data and synthetics however higher frequency peaks are also seen primarily for sources in line with the major axis of the ridge perhaps indicating higher resonant modes excitations of lateral ribs off of the main ridge are also seen at frequencies consistent with their dimensions the favored directions of resonance are shown to be transverse to the major axes of the topographic features

global scale modes of surface temperature variability on interannual to century timescales using 100 years of global temperature anomaly data we have performed a singular value decomposition of temperature variations in narrow frequency bands to isolate coherent spatio temporal modes of global climate variability statistical significance is determined from confidence limits obtained by monte carlo simulations secular variance is dominated by a globally coherent trend with nearly all grid points warming in phase at varying amplitude a smaller but significant share of the secular variance corresponds to a pattern dominated by warming and subsequent cooling in the high latitude north atlantic with a roughly centennial timescale spatial patterns associated with significant peaks in variance within a broad period range from 2 8 to 5 7 years exhibit characteristic el nino southern oscillation enso patterns a recent transition to a regime of higher enso frequency is suggested by our analysis an interdecadal mode in the 15 to 18 years period range appears to represent long term enso variability this mode has a sizeable projection onto global average temperature and accounts for much of the anomalous global warmth of the 1980s a quasi biennial mode centered near 2 2 years period and a mode centered at 7 to 8 years period both exhibit predominantly a north atlantic oscillation nao temperature pattern a potentially significant decadal mode centered on 11 to 12 years period also exhibits an nao temperature pattern and may be modulated by the century scale north atlantic variability

directional resonance variations across the pernicana fault mt etna in relation to brittle deformation fields summary the pernicana fault pf is the main structural element of mt etna and the northern boundary of a section sliding to the southeast observed ground motion records in the damage zone of the pf show strong variations of directional resonance in the horizontal plane the observed resonance directions exhibit an abrupt rotation of azimuth by about 30 across the fault varying from n166 on the north side to n139 on the south we interpret the directional resonance observations in terms of changes in the kinematics and deformation fields on the opposite sides of the fault the northern side is affected primarily by the left lateral strike slip movement whereas the southern side that is subjected also to sliding is under a dominant extensional stress regime brittle deformation models based on the observed kinematic field predict different sets of fractures on the opposite sides of the fault synthetic cleavages and extensional fractures are expected to dominate in the northern and southern sides respectively these two fracture fields have different orientations n74 and n42 respectively and both show a near orthogonal relation 88 in the northern sector and 83 to the south with the azimuth of the observed directional resonance we conclude that the direction of the largest resonance motions is sensitive to and has transversal relationship with the dominant fracture orientation the directional amplification is inferred to be produced by stiffness anisotropy of the fault damage zone with larger seismic motions normal to the fractures

site effects in unstable rock slopes dynamic behavior of the randa instability switzerland we evaluate the dynamic response of the large around five million cubic meters unstable rock slope at randa switzerland based on ground motion recordings during small earthquakes seismic measurements revealed strong polarization of the wavefield in the direction of maximum slope displacement with spectral amplification factors 5 within the unstable area results further highlighted resonant frequencies of both the large unstable rock mass and individual blocks within it block vibration was confirmed by phase analysis of in situ displacement measurements from two bounding tension fractures during a small earthquake numerical simulation using a discontinuous elastic model showed that the presence of steeply dipping compliant fractures is crucial for recreating the observed site response such fractures are common in rock slope instabilities and are here shown to contribute to polarization and amplification of seismic shaking site effects that are rarely considered for hard rock slopes and which may influence the potential for earthquake triggered failure

directional topographic site response at tarzana observed in aftershocks of the 1994 northridge california earthquake implications for mainshock motions abstract the northridge earthquake caused 1 78 g acceleration in the east west direction at a site in tarzana california located about 6 km south of the mainshock epicenter the accelerograph was located atop a hill about 15 m high 500 m long and 130 m wide striking about n78 e during the aftershock sequence a temporary array of 21 three component geophones was deployed in six radial lines centered on the accelerograph with an average sensor spacing of 35 m station c00 was located about 2 m from the accelerograph we inverted aftershock spectra to obtain average relative site response at each station as a function of direction of ground motion we identified a 3 2 hz resonance that is a transverse oscillation of the hill a directional topographic effect the top base amplification ratio at 3 2 hz is about 4 5 for horizontal ground motions oriented approximately perpendicular to the long axis of the hill and about 2 for motions parallel to the hill this resonance is seen most strongly within 50 m of c00 other resonant frequencies were also observed a strong lateral variation in attenuation probably associated with a fault caused substantially lower motion at frequencies above 6 hz at the east end of the hill there may be some additional scattered waves associated with the fault zone and seen at both the base and top of the hill causing particle motions not spectral ratios at the top of the hill to be rotated about 20 away from the direction transverse to the hill the resonant frequency but not the amplitude of our observed topographic resonance agrees well with theory even for such a low hill comparisons of our observations with theoretical results indicate that the 3d shape of the hill and its internal structure are important factors affecting its response the strong transverse resonance of the hill does not account for the large east west mainshock motions assuming linear soil response mainshock east west motions at the tarzana accelerograph were amplified by a factor of about 2 or less compared with sites at the base of the hill probable variations in surficial shear wave velocity do not account for the observed differences among mainshock acceleration observed at tarzana and at two different sites within 2 km of tarzana

remanence acquisition in red beds from the coal measures of central england the magnetic mineralogy palaeomagnetism and magnetic fabric of a carboniferous mudstone dominated red bed sequence and associated sandstones are described natural remanent magnetization nrm is carried by hematite both as relatively coarse particles and as pigmentary material magnetite and goethite also contribute to the remanence of some mudstones the magnetization of red sandstones is carried exclusively by hematite magnetic carriers have been identified using a combination of rock magnetic measurements x ray diffraction and 57 fe mossbauer spectroscopy both sandstones and mudstones carry a primary style magnetic fabric apparently related to the deposition of hematite particles the reddening is associated with areas which developed better drainage and is genetically related to complex palaeosols in the mudstones a feature indicating that it and the magnetization must have been approximately contemporaneous with sediment deposition

evidence for ground motion polarization on fault zones of mount etna volcano 1 during local and regional earthquakes an evident amplification of horizontal ground motion is observed at two seismological stations near the tremestieri fault on the southeastern flank of mount etna volcano rotated component spectral ratios show a narrow spectral peak around 4 hz along a n40 e direction a conventional polarization analysis using the eigenvectors of the covariance matrix confirms the very stable directional effect enhancing the approximately ne sw elongation of the horizontal ground motion in the fault zone the effect is evident during the entire seismogram and independent of source back azimuth as well as distance and depth of earthquakes the same polarization is observed in ambient noise as well this consistency allowed us to use microtremors for checking ground motion polarization along and across the tremestieri fault zone with a high spatial resolution the result is a stable polarization of horizontal motion in the entire area that can be observed in a broad frequency band to check whether this ground motion property is recurrent and to understand a possible relationship with fault strike faulting style or orientation of fractures ambient noise was recorded on other mapped faults of the mount etna area the moscarello acicatena and pernicana faults the latter in particular is characterized by different strike and faulting style a systematic tendency of ambient noise to be polarized is found in all of the faults a picture emerges where normal faults of the eastern flank show an e w to ne sw polarization that changes on the pernicana fault which develops approximately e w and is characterized by a prevailing nw se to n s polarization directions of polarization were never parallel to the fault strike moreover polarization persists too far away from the fault trace excluding an effect limited to a narrow low velocity zone hosted between harder wall rocks both these observations rule out an interpretation in terms of fault trapped waves the cause of observed polarizations will be the subject of future studies however the consistency with recent results of velocity anisotropy in a part of the investigated area suggests a possible role of attenuation anisotropy on horizontal amplitude variations versus azimuth