tentative correlation of pollen records of the last interglacial at grande pile and ribains with marine isotope stages eemian lake deposits in grande pile and ribains france correlate with marine isotope substages mis 5e and 5d as delimited in two pollen bearing deep sea cores off portugal the eemian forests in france lasted for approximately 20 millennia from at least 126 000 to ca 107 000 yr b p oscillatory climate deteriorations began about 115 000 yr ago an intense cold spell affected the region approximately 110 000 yr ago

observed evolution of linear and nonlinear effects at the dahan downhole array taiwan analysis of the september 21 1999 m 7 3 chi chi earthquake sequence in this paper the site characteristics of the dahan downhole array are studied by analyzing the september 21 1999 m 7 3 chi chi earthquake sequence including the main shock and some aftershocks the four level array 0 m 50 m 100 m and 200 m is located to the north of hualien city in eastern taiwan polarization analysis is used to check the orientation errors of the seismometers at different levels of depth if the surface instrument is chosen as reference the angle between the major polarization axes of the surface and any downhole records is the orientation error that must be corrected for the downhole accelerographs the orientation errors at depths of 50 m 100 m and 200 m are 32 120 and 84 after the corrections the coherency between the surface and downhole records is substantially improved spectral ratio analysis shows that the predominant frequency of the chi chi main shock shifts to a lower frequency we also simulate ground motions at different depths by using the haskell method with a linear velocity structure model the record at surface is chosen as the input motion compared with the observed data ground acceleration can be well reproduced for the aftershocks weak motion events of the september 21 1999 m 7 3 chi chi earthquake however for the chi chi main shock the synthetic waveform cannot match well with the observation neither in amplitude nor in phase this indicates that large ground shaking probably induced the nonlinear site effect at that time and the model used cannot support it

a comparison and test of various site response estimation techniques including three that are not reference site dependent abstract we compare various site response estimation techniques using after shock data of the 1989 loma prieta earthquake collected in oakland california because of recent interest in comparing results from weak and strong motion to infer any nonlinearity and between direct s and coda waves we pay particular attention to the uncertainties first sediment to bedrock spectral ratio estimates between pairs of sites are compared with those obtained from various generalized inversion approaches where the source and site effects of multiply recorded events are solved for simultaneously we find that the site amplification factors are very similar among these approaches but that the uncertainties can be significantly different depending on how the data are weighted we also examine and test three site response estimation techniques that do not rely on a reference site to estimate source and path effects the first involves a parameterized source and path effects inversion even when the bedrock data are excluded from consideration this approach is found to reveal the frequency dependence of site response at each of the sediment sites the second technique involves taking horizontal to vertical component spectral ratios receiver function type estimates of shear wave aftershock data these are also found to reveal the frequency dependence of site response at the sediment sites and the results for the bedrock site are relatively flat and near unity the third estimate is formed by taking horizontal to vertical component ratios of ambient seismic noise and these are shown to reveal the fundamental resonant frequency of the sediment sites unfortunately discrepancies exist among all of the site response estimates and with one dimensional predictions with respect to a frequency independent scaling factor nevertheless the highly frequency dependent character of site response is well constrained and the fact that non reference site dependent methods are capable of revealing this is promising for site specific hazard assessments in regions that lack adequate reference sites

formal subdivision of the quaternary system period past present and future abstract the quaternary system period represents the past 2 58 million years and is officially subdivided into the pleistocene and holocene series epochs with the base of the holocene assigned an age of 11 700 calendar years before ad 2000 the two lowest stages of the pleistocene the gelasian base 2 58 ma and the calabrian base 1 80 ma have been ratified and these effectively constitute the lower pleistocene subseries all other official subdivisions are pending for the middle pleistocene subseries three candidate global boundary stratotype sections and points gssps are under consideration the valle di manche in calabria and montalbano jonico in basilicata both in southern italy and the chiba section in japan the matuyama brunhes chron boundary 773 ka serves as the principal guide for the base of the middle pleistocene the base of the upper pleistocene subseries is generally agreed to coincide approximately with that of the last interglacial marine isotope substage 5e 130 ka the fronte section near taranto in southern italy represents a possible candidate gssp but an antarctic ice core might also serve this purpose a tripartite subdivision of the holocene with subseries stage boundaries at 8200 and 4200 years b p is also under consideration additional fine scale formal subdivision of the quaternary is being explored with the last glacial maximum serving as a test case the anthropocene is both an informal and undefined interval of time that includes the present day its duration formal informal status rank and method of definition are all under debate with one suggestion that it be defined as a formal unit beginning with the world s first nuclear bomb explosion on july 16th 1945 suggested and proposed gssps are compared and critiqued the history leading to ratification of the quaternary period in 2009 is examined drawing upon published and unpublished material

nonlinear behavior of soil sediments identified by using borehole records observed at the ashigra valley japan abstract we evaluate the nonlinear behavior of soil sediments during strong ground shaking based on the identification of their s wave velocities and damping factors for both the weak and strong motions observed on the surface and in a borehole at kuno in the ashigara valley japan first we calculate spectral ratios between the surface station ks2 and the borehole station kd2 at 97 6 m below the surface for the main part of weak and strong motions the predominant period for the strong motion is apparently longer than those for the weak motions this fact suggests the nonlinearity of soil during the strong ground shaking to quantify the nonlinear behavior of soil sediments we identify their s wave velocities and damping factors by minimizing the residual between the observed spectral ratio and the theoretical amplification factor calculated from the one dimensional wave propagation theory the s wave velocity and the damping factor h 2 q 1 of the surface alluvial layer identified from the main part of the strong motion are about 10 smaller and 50 greater respectively than those identified from weak motions the relationships between the effective shear strain 65 of the maximum shear strain calculated from the one dimensional wave propagation theory and the shear modulus reduction ratios or the damping factors estimated by the identification method agree well with the laboratory test results we also confirm that the soil model identified from a weak motion overestimates the observed strong motion at ks2 while that identified from the strong motion reproduces the observed thus we conclude that the main part of the strong motion whose maximum acceleration at ks2 is 220 cm sec 2 and whose duration is 3 sec has the potential of making the surface soil nonlinear at an effective shear strain on the order of 0 1 the s wave velocity in the surface alluvial layer identified from the part just after the main part of the strong motion is close to that identified from weak motions this result suggests that the shear modulus recovers quickly as the shear strain level decreases

the paleoclimatology of lake baikal a diatom synthesis and prospectus abstract the paleoclimatic archive held in lake baikal sediments is of significant importance given the lake s position in one of the world s most continental regions where there are few continuous high quality records spanning the quaternary here i review diatom and associated biogenic silica records from lake baikal sediments and provide a paleoclimatic synthesis of changes at various timescales over the quaternary i initially highlight major climatic and hydrological aspects of lake baikal as understanding the contemporary system both regionally and within the lake are fundamental to understanding past change interpreted from the sedimentary archive in this respect special attention is given to factors that can affect the integrity of the diatom record most notably dissolution processes these mechanisms are likely to have had a relatively greater impact on the preservation of diatom valves during glacial periods because of overall lower diatom productivity lower diatom numbers and relative increased dissolution during cold periods explains the lack of diatoms and low biogenic silica concentrations found in the lake sediments during glacial periods the biogenic record highlights the nature of the 100 ka cycle especially during the last 800 ka although there is also a strong precessional component further work is needed to reassess biological responses in lake baikal with respect to different orbital forcing mechanisms together with their impacts on evolution and speciation of diatoms the biological record from lake baikal confirms that the last interglacial in central asia lasted approximately 10 5 ka productivity in the lake as inferred from diatom biovolume accumulation rates exhibits millennial scale variability with the occurrence of centennial scale reductions in diatom biomass throughout the last interglacial period the most severe reduction in diatom biomass at c 120 ka bp is concurrent with millennial scale cooling in the north atlantic region links to changes in north atlantic ocean thermohaline circulation via teleconnections are also evident in the nature of the abrupt ecological changes in the lake throughout the last 60 ka linked to ice rafting into the north atlantic otherwise known as heinrich events new robust radiocarbon chronologies for sediments deposited during the late glacial and holocene in lake baikal allow detailed multi decadal records to be constructed for the last 14 000 years cooling events associated with millennial scale cycles are also apparent in the lake baikal record and both the diatom record and oxygen isotope record of the diatom silica highlight that biological responses to these abrupt events are almost simultaneous comparisons made between lake baikal records with others worldwide highlights that many of the holocene cooling events are associated with melt water outburst from the laurentide ice sheet and changes in solar insolation during the last 1000 years snow cover on lake baikal has been inferred from past diatom assemblages and is closely linked to weakening of the north atlantic oscillation allowing increasing intensity of the siberian high to develop and during the 17th and 18th centuries in the last 150 years diatom species have been shown to be sensitive indicators of recent warming however impacts from future global warming will be complex and are likely to impact not only on the balance between endemic and cosmopolitan diatoms throughout the lake but on the balance between siliceous and non siliceous algae and sources of primary productivity

last interglacial climates the last interglacial commonly understood as an interval with climate as warm or warmer than today is represented by marine isotope stage mis 5e which is a proxy record of low global ice volume and high sea level it is arbitrarily dated to begin at approximately 130 000 yr b p and end at 116 000 yr b p with the onset of the early glacial unit mis 5d the age of the stage is determined by correlation to uranium thorium dates of raised coral reefs the most detailed proxy record of interglacial climate is found in the vostok ice core where the temperature reached current levels 132 000 yr ago and continued rising for another two millennia approximately 127 000 yr ago the eemian mixed forests were established in europe they developed through a characteristic succession of tree species probably surviving well into the early glacial stage in southern parts of europe after ca 115 000 yr ago open vegetation replaced forests in northwestern europe and the proportion of conifers increased significantly farther south air temperature at vostok dropped sharply pulses of cold water affected the northern north atlantic already in late mis 5e but the central north atlantic remained warm throughout most of mis 5d model results show that the sea surface in the eastern tropical pacific warmed when the ice grew and sea level dropped the essentially interglacial conditions in southwestern europe remained unaffected by ice buildup until late mis 5d when the forests disappeared abruptly and cold water invaded the central north atlantic ca 107 000 yr ago

characteristics and genesis mechanism of ground fissures in taiyuan basin northern china abstract since the 1980s ground fissures in the taiyuan basin have experienced blowouts resulting in a significant but hidden danger to cities in the basin this paper describes the plane and damage characteristics of the ground fissures based on the findings of field investigations and mapping most ground fissures in the basin were determined as linear with pinch out reappearances on the surface they were characterized by both horizontal tension with maximum widths and vertical offsets of up to 40 and 15 cm respectively the ground fissure strikes in the basin were observed to be consistent with those of nearby active faults and the long axis direction of the groundwater depression funnel the roads and houses that lie across the fissures were determined to be the most affected by ground fissure disasters in the basin the primary damage modes for the roads were vertical offset and surface collapse whereas buildings experienced foundation failure and tensile damage profiles obtained through geological drilling and trench exploration further revealed obvious tension and synsedimentary characteristics of the ground fissures correlated with existing faults correlation analysis shows that the formation of ground fissures in taiyuan basin is mainly related to faults and excessive groundwater extraction theoretical analysis revealed that the size and activity of ground fissures in the basin were positively correlated with four factors the dip of faults in an area regional tensile stress difference between the thicknesses of aquifers on either side of a fault and groundwater exploitation the significant increase in ground fissure activity since the 1980s mainly reflects uncontrolled groundwater discharge hence prevention of excessive groundwater exploitation in the basin would mitigate the destructive effects of the ground fissures

nonlinear ground motion amplification by sediments during the 1994 northridge earthquake it has been known since at least 1898 ref 1 that sediments can amplify earthquake ground motion relative to bedrock for the weak ground motion accompanying small earthquakes the amplification due to sediments is well understood in terms of linear elasticity hooke s law 2 but there has been a long standing debate regarding the amplification associated with the strong ground motion produced by large earthquakes the view of geotechnical engineers based largely on laboratory studies is that hooke s law breaks down at larger strains causing a reduced nonlinear amplification seismologists on the other hand have tended to remain sceptical of this nonlinear effect mainly because the relatively few strong motion observations seemed to be consistent with linear elasticity although some recent earthquake studies have demonstrated nonlinear behaviour under certain circumstances3 4 the significance of nonlinearity for the type of stiff soil sites found in the greater los angeles region remains unresolved5 here we report that ground motion amplification due to sediments for the main shock of the 1994 northridge earthquake was up to a factor of two less than the amplification observed for its aftershocks these observations imply significant nonlinearity in such amplification and bring into question the use of measurements of weak ground motion to predict the strong ground motion at sedimentary sites

the eemian interglaciation in northwestern germany abstract hundreds of small lakes became filled with eemian deposits following the retreat of saalian ice in northwestern germany weakly expressed climate oscillations have been inferred from some local pollen records of late saalian sediments sea level stood 7 m below the current northwest german sea level datum nn during the interglacial climate optimum and decreased afterward a uniform vegetational succession of the eemian mixed forests correlated with marine isotope stage mis 5e terminated with the demise of boreal woodlands marked by a steep increase in nonarboreal pollen this is the onset of the early weichselian herning stade correlated with mis 5d no sharp climate oscillations during the eemian have been documented in the ending phase of the interglaciation the climate deteriorated gradually dominant heath and grass tundras point to a substantial decline of summer temperature during the herning stade sea level then stood at 40 m nn sedimentological considerations supported by counts of partly varved deposits indicate that the eemian lasted about 10 000 11 000 yr and the herning for several millennia

dilatancy induced p waves as evidence for nonlinear soil behavior a much discussed topic in seismology deals with how and under which loading conditions soil shows nonlinear behavior and how this can be verified from seismograms seismologists have been seriously searching for signatures of nonlinear soil response to earthquakes for about two decades a mechanism explaining the dispersion in the p wave spectra due to the interaction between compressional p and shear s waves is presented shear waves in granular materials induce longitudinal dilatancy waves so called waves with approximately double frequency this can be explained with dilatancy and contractancy which is characteristic of granulates under shear deformations the predicted dispersion is observed in laboratory experiments and verified by comparing accelerograms from hard rock and soil stations from the vrancea region romania the arrival time difference between waves and s waves may theoretically be indicative of the thickness of nonsaturated granular layers these results modeled with nonlinear constitutive relations of the rate type show a specific type of nonlinearity in granular sediments also for earthquakes of moderate magnitudes

reconstruction of the grande pile eemian using inverse modeling of biomes and δ13c abstract a new method to reconstruct past climatic conditions between 130 and 100 ka bp from pollen and isotopic data is applied to a previously unanalyzed grande pile core gpxxi we applied the inverse mode to the biome4 vegetation model the method utilizes 13 c measured in parallel to the pollen samples as a constraint for the model first the biomes and the 13 c simulated by the model are compared with the biome allocation of the pollen data the 13 c to be simulated takes into account the degradation effect on the preserved organic matter this procedure allows the reconstruction of the mean annual temperature and precipitation as well as the mean temperatures of the warmest and coldest months we show that during the eemian sensu stricto the reconstructed precipitation is similar to modern values with low variability the cold stadials and the penultimate glaciation are characterized by very low precipitation amounts the temperature estimates however indicate differences with several oscillations identified the peak values are reached at about 124 125 ka bp but two other warm intervals are also identified the variations in temperature appear to be related to sea surface temperature oscillations in the north atlantic region and are also in agreement with the timing of ice sheet build up in the northern hemisphere seasonal variations are also identified in the estimated temperatures of the warmest and coldest months

site response in southern california for probabilistic seismic hazard analysis this study determines site response factors that can be applied as cor rections to a rock attenuation relationship for use in probabilistic seismic hazard analysis the site response factors are amplitude and site class dependent these amplification factors are determined by averaging ratios between observed and pre dicted ground motions for peak ground acceleration pga and for 5 damped re sponse spectral acceleration at 0 3 1 0 and 3 0 sec oscillator periods the observa tions come from the strong motion database of the southern california earthquake center scec and the predictions are based on the sadigh 1993 rock attenuation relation when separated and averaged according to surface geology significantly different site response factors are found for quaternary and mesozoic units but a subclassification of quaternary is generally not justified by the data the low input motion amplification factors are consistent with those obtained from independent aftershock studies at the pga and 0 3 second period an observed trend of decreasing quaternary site amplification with higher input motion is consistent with nonlinear soil behavior however the trend exists for mesozoic sites as well implying that this may be an artifact of the sadigh relationship there is a correlation between larger site response factors and lower average shear wave velocity in the upper 30 m for low predicted pga input motions with an increase in the correlation with increasing period the 0 3 sec site response factors for quaternary data in southern california determined in this study are consistent with 0 3 sec nehrp site response correction factors however at 1 0 sec period some inconsistencies remain a trend is also seen with respect to sediment basin depth where deeper sites have higher average site response factors these results constitute a customized attenuation relationship for southern california the implication of these customized attenuation models with respect to probabilistic hazard analysis is examined in field and petersen 2000

nonlinear sediment response during the 1994 northridge earthquake observations and finite source simulations we have addressed the long standing question regarding nonlinear sediment response in the los angeles region by testing whether sediment amplification was similar between the northridge earthquake and its aftershocks comparing the weak and strong motion site response at 15 sediment sites we find that amplification factors were significantly less for the main shock implying systematic nonlinearity the difference is largest between 2 and 4 hz a factor of 2 and is significant at the 99 confidence level between 0 8 and 5 5 hz the inference of nonlinearity is robust with respect to the removal of possibly anomalous sediment sites and how the reference site motion is defined furthermore theoretical ground motion simulations show no evidence of any bias from finite source effects during the main shock nonlinearity is also suggested by the fact that the four sediment sites that contain a clear fundamental resonance for the weak motion exhibit a conspicuous absence of the peak in the strong motion although we have taken the first step of establishing the presence of nonlinearity it remains to define the physics of nonlinear response and to test the methodologies presently applied routinely in engineering practice the inference of nonlinearity implies that care must be exercised in using sediment site data to study large earthquakes or predict strong ground motion

variability in nonlinear sediment response during the 1994 northridge california earthquake abstract spectral ratios between sediment sites and rock sites for strong and weak ground motion are compared to infer the extent of nonlinear sediment response in the los angeles area during the 1994 northridge earthquake northridge mainshock records form the strong motion database and aftershock records form the weak motion database the degree of nonlinearity is evaluated at 25 locations in and around the san fernando and los angeles basins based on the ratio of weak to strong spectral amplification factors wsaf values of wsaf vary greatly from site to site and for a given site from one frequency band to another over the range from 0 75 to 20 hz this complexity is attributed to differences in several factors material properties under the sites and the amplitude and frequency content of the input ground motions given these observations it is not possible to assign an acceleration or velocity level at which nonlinearity initiates for all the stiff soil sites analyzed however no nonlinearity is seen below a peak acceleration of about 200 to 300 cm sec 2 or peak velocity of 20 to 30 cm sec nonlinearity is seen at all sites in or near the san fernando valley nonlinearity in the los angeles basin is limited to a few isolated sites for the northridge earthquake even sites with strong nonlinearity still show amplification levels greater than 1 0 relative to rock sites for frequencies below 10 hz

climatic variability of marine isotope stage 7 direct land sea ice correlation from a multiproxy analysis of a north western iberian margin deep sea core abstract the direct land sea ice correlation performed in the north western iberian margin core md01 2447 shows that marine isotope stage 7 mis 7 is marked by an alternation of five warm and cold periods this climatic variability is in general synchronously detected in marine and terrestrial realms by our record termination iii is marked by three cold episodes the last one interrupts the forest development in north western iberia related to the deglacial climatic amelioration it begins in the middle of termination iii but the maximal cold conditions occur at the beginning of low ice volume conditions mis 7 is characterised by three periods of very low ice volume associated with marine and continental high temperatures in and off north western iberia the correlation of our record with odp site 980 shows that the climatic variability detected in the north western iberian region has also an imprint in northern north atlantic it also highlights that most of the cold periods are associated with iceberg discharges in the north atlantic the comparison of the north western iberian margin sequence with the long european pollen records has allowed refining the correlation of the marine and continental stratigraphy for mis 7

a comparison of observations of ground response to weak and strong ground motion at coalinga california abstract measurements of the response to earthquake motion of an unsaturated soil in coalinga california indicate that this response is linear within the limits of random errors for frequencies below 10 hz and for accelerations up to 0 7 g the response of the soil site relative to a bedrock site was determined by dividing the amplitude spectrum of the soil site ground motion for a given event by the amplitude spectrum of the bedrock site ground motion for the same event the relative response of this pair of sites to 23 regional and small local earthquakes is the same in the 1 to 10 hz band as the response to seven strong motion events within a random error of a factor of 1 3 at 10 to 11 hz the relative response to strong motion is significantly reduced by as much as a factor of 2 from the relative response to the 23 regional and small local earthquakes at the 95 per cent confidence level suggesting the possibility of nonlinear response the response of the soil site is a factor of 2 to 3 times larger than that of the bedrock site the variation in the spectral ratios for strong motion events and for regional and small local events about their respective averages has a standard deviation of about a factor of 2

engineering implications of ground motions from the northridge earthquake the magnitude duration and frequency content of ground motions from the northridge earthquake are analyzed and compared to predictive relationships typically used in engineering design and to the 1994 uniform building code ubc a relationship between maximum horizontal acceleration on soil versus maximum horizontal acceleration on rock is presented based on strong motion recordings at free field sites the effect of geologic conditions on localized damage patterns is shown to be important for this earthquake although many of the sites within the affected region are stiff soil sites classified as s1 or s2 sites by the ubc the results of preliminary seismic site response analyses performed at two deep alluvial sites indicate that much of the observed site amplification can be captured by one dimensional wave propagation analyses

climate variations in europe over the past 140 kyr deduced from rock magnetism rapid shifts in climate during the last glacial are now well documented particularly from the oxygen isotope records of the two greenland ice cores grip1 2 and gisp23 in the grip record1 2 these climate events are also seen during the preceding eemian interglacial which may be an analogue for the future climate warmed by the greenhouse effect but these shifts are not found in the eemian section of the gisp2 core3 casting doubt on whether the rapid shifts in the grip oxygen isotope record really do represent a climate signal here we present magnetic susceptibility pollen and organic carbon records from maar lake deposits in the massif central france these data provide an independent record of past climate and we find that they correlate well with the ice core records during the last glacial during the eemian two rapid cooling events seen in our record also correlate with those seen in the grip ice core supporting the idea that rapid climate change did occur in the eemian interglacial and demonstrating that it extended to continental europe

direct terrestrial marine correlation demonstrates surprisingly late onset of the last interglacial in central europe an interdisciplinary study of a small sedimentary basin at neumark nord 2 nn2 germany has yielded a high resolution record of the palaeomagnetic blake event which we are able to place at the early part of the last interglacial pollen sequence documented from the same section we use this data to calculate the duration of this stratigraphically important event at 3400 350 yr more importantly the neumark nord 2 data enables precise terrestrial marine correlation for the eemian stage in central europe this shows a remarkably large time lag of ca 5000 yr between the mis 5e peak in the marine record and the start of the last interglacial in this region

an analysis of eemian climate in western and central europe on the basis of 31 pollen diagrams and additional data for botanical macrofossils an analysis is made of the last interglacial eemian climatic history in western and central europe the main tool for this analysis is the climatic indicator species method only selected woody species are used for the quantification of data partial climatic range diagrams are presented for abies alba acer monspessulanum acer tataricum buxus sempervirens tilia tomentosa the problem of time correlation and pollen zonation of the eemian is discussed the climatic analysis itself is based on an improved version of the indicator species method in this version not every site is analysed for its climatic values instead maps and tables on the migrational history of hedera ilex buxus abies and species of acer tilia and abies are the basis for climatic maps showing respectively january and july isotherms for the periods of the corylus zone e4a and the carpinus zone e5 it is concluded that mean january temperatures were as much as 3 c higher at amsterdam the netherlands than at present and mean temperatures in july were 2 c higher however the thermal maximum in winter was later zone e5 than the summer thermal maximum zone e4a winter temperatures changed parallel to rise and fall of global sea level precipitation changes are more difficult to estimate in the first part of the eemian precipitation must have been relatively low but from zone e4b onward it increased to higher values reaching 800 mm and probably substantially more in zones e5 and e6 hence the eemian climate was in its beginning relatively more contintental and later from e4b onward more oceanic however as compared with the holocene the eemian climate was generally speaking more oceanic

evidence for early warming and cooling in north atlantic surface waters during the last interglacial in depth analysis of planktic foraminiferal census data paired with 18o records of specific indicator species provides new insight into the surface ocean evolution of the northeast atlantic during the previous interglacial warm period oxygen isotope stage ois 5e full interglacial conditions existed at the study site for a maximum of only 8 kyr between 125 and 117 ka highest sea surface temperatures ssts occurred during early ois 5e concomitant with high summer insolation but after the main phase of ice sheet melting of the preceding glaciation saalian this early peak sst interval is marked by the appearance of tropical subtropical species and lasted for 4 kyr until 121 ka as corroborated by a major change in planktic 18o relative stability in global ice volume continued for another 3 4 kyr before ssts dropped further toward the next stadial during early ois 5e the situation of the surface water vertical structure appears to have been different from the early holocene for ois 5e it is therefore suggested that the particular melting history of late saalian ice had a long lasting and profound effect on both postdeglacial surface water mass configuration in the north atlantic and heat moisture transfer into europe

using microtremors to assess potential earthquake site response a case study in flushing meadows new york city abstract we have used portable 5 sec period seismometers to record ambient noise across a glacially cut valley filled with unconsolidated holocene sediments the valley located in flushing meadows new york city is surrounded by a densely populated urban environment microtremors were recorded at several sites on and adjacent to the valley while some raw spectra of valley site microtremors exhibit no predominant peaks spectral ratios taken with respect to recordings made at a reference station outside the valley show a sharp peak near 0 8 hz a secondary peak near 2 4 hz is also visible in some of the spectral ratios the frequency of the predominant peak remains constant across the valley width while the relative amplitude decreases systematically from a maximum at the valley center to background levels near the valley edge resonant frequencies predicted by one dimensional modeling of the valley center site response show excellent agreement with observations the 0 8 hz spectral ratio peak is interpreted as the fundamental resonance mode and the 2 4 hz peak is interpreted as the first harmonic of the region above the base of an organic clay layer observed in borehole data the amplification factors implied by the observed spectral ratios are unrealistically high up to 100 which can be attributed to the close proximity of microtremor sources an experiment involving the use of a pile driver source located outside the valley was also performed signals obtained at valley sites during times when the pile driver was in operation show a two fold increase in the amplitude of a spectral peak when compared to signals obtained when the pile driver was turned off this observation gives additional evidence that observed spectral peaks represent soil layer resonances in the valley based on the results of this and other previous studies we conclude that easily obtained microtremor measurements can contribute valuable microzonation and site response information to a study of regional earthquake hazard

distribution and mechanism of the ground fissures in wei river basin the origin of the silk road wei river basin wrb is the origin of the ancient and new silk road and it is located in southern fen wei graben system china since 1950s hundreds of ground fissures have formed in this affluent basin and these ground fissures have become the main geohazard in wrb this paper used a series of geological investigations such as site investigation trench excavation geological drilling and geophysical survey to understand the distribution and mechanism of formation of the ground fissures in wrb the results are 1 212 ground fissures in wrb were located in xi an xianyang weinan city and they have clear orientations mainly distributed from nee to sww nw to se and e to w moreover the ground fissures are accompanied by active faults along the same directions 2 ground fissures in wrb can be divided into two types some ground fissures display obvious horizontal and vertical separations on the earth surface whereas others only display obvious horizontal separations on the earth surface 3 ground fissures in wrb are triggered by four factors viz basin structure active fault human activities and loess erosion 4 the mechanism for the formation of ground fissures has also been proposed tectonic faulting is the fundamental cause of ground fissures in the wei river basin and imbalances in the man land caused by human actives accelerated the ground fissures activities 5 many effective measures have also been proposed to mitigate the hazards of ground fissures in wrb such as planning engineering measures controlling the exploitation of groundwater and monitoring this research will be helpful in safeguarding the sustainable development of the silk road economic belt

was the climate of the eemian stable a quantitative climate reconstruction from seven european pollen records the aim of the present study is to estimate the range of the climatic variability during the eemian interglacial which lasted about 10 000 years marine isotopic stage 5e the modem pollen analogue technique is applied to seven high resolution pollen records from france and poland to infer the annual precipitation and the mean temperature of the coldest month the succession of pollen taxa and the reconstructed climate can be interpreted coherently the warmest winter temperatures are centred in the first three millennia of the eemian interglacial during the mixed oak forest phase with quercus and corylus as dominant trees a rapid shift to cooler winter temperatures of about 6 degrees to 10 degrees c occurred between 4000 and 5000 years after the beginning of the eemian related to the spread of the carpinus forest this shift is more obvious for the reconstructed temperatures than for precipitation and is unique and irreversible for the whole eemian period following this climatic shift of the eemian variations of temperature and precipitation during the fast 5000 years were only slight with an amplitude of about 2 degrees to 4 degrees c and 200 to 400 mm yr the estimated temperature changes were certainly not as strong as those reconstructed for the stage 6 5e termination or the transition 5e 5d this is consistent with the constantly high ratio of tree pollen throughout the eemian indicative of a succession of temperate forest types this gradual transition between different forest landscapes can be related to intrinsic competition between the species rather than to a drastic climatic change c 1998 elsevier science b v all rights reserved

site amplification of coda waves from local earthquakes in central california the goals of this study are two fold 1 to examine the site effect of coda waves believed to be the average site effect of shear waves in order to understand its spatial and frequency dependent behavior and 2 to learn what we can about the processes that generate the coda itself we use digital data from over 90 earthquakes each recorded by a subset of some 150 stations in the coast ranges of central california between san francisco and san luis obispo results from the band 1 5 to 24 hz indicate that site amplification depends strongly on surface geology and frequency at low frequencies 1 5 to 3 0 hz changes in amplification up to a factor of 20 are observed amplification generally varies inversely with deposit age at sediment sites and is lowest at granite and franciscan basement sites at high frequencies 6 to 24 hz the pattern changes many granite sites the majority in the gabilan range exhibit increasing amplification with frequency relative to the average station this behavior differs strikingly from that observed at sediment and franciscan sites which roll off at an intermediate rate and many sediment sites adjacent to the san andreas fault zone which decay away even more rapidly with frequency these results can be explained qualitatively by appealing to variable near site impedance and attenuation however complicating phenomena such as mode excitation in valley sediments must exist at low frequencies peaked behavior at a few hard rock sites at high frequency 12 hz currently lacks explanation at a few sediment sites the low frequency excitation is so strong that the coda envelopes begin to take on different shapes this contradicts the assumption based on previous observations that the coda shape is independent of source receiver location thus some site measurements may be artificially high the working model of coda waves as body wave energy backscattered from randomly distributed inhomogeneities must be modified to include the possibility of efficient near site resonance excited by incident direct and coda wave energy

pollen analysis of a long upper pleistocene continental sequence in a velay maar massif central france abstract a new 20 m sequence is presented which is based on 279 spectra derived from a coring at le bouchet lake massif central france the vegetational history of this region is described back to the end of the last interglacial ribains interglacial the two preglacial early glacial forested interstadials st geneys 1 and st geneys 2 are evidence for the first time in the massif central in spite of the altitude of the site 1200 m they suggest a quite temperate vegetation with the same mesophilous character as during the holocene the pleniglacial appears to be threefold with two cold episodes lower and upper pleniglacial divided by a long complex period of moderate climatic improvement the vegetation history of this mountain region is compared with that evidenced for the same period on the basis of the sequence of les echets at a lower altitude 267 m botanical and climatic inferences are discussed

simultaneous study of the source path and site effects on strong ground motion during the 1989 loma prieta earthquake a preliminary result on pervasive nonlinear site effects we considered the effects of source propagation path and local site conditions on strong ground motion from the loma prieta earthquake in the following steps first the local site effect was removed from the strong motion records applying the weak motion amplification factors estimated from nearby stations of usgs regional network using the coda method then we confirmed the approximate validity of the 1 r law of geometrical spreading factor for the crustal model applicable to the region and we determined the attenuation parameter q f and source spectrum s f empirically from the site effect corrected spectral amplitude both q f and s f are consistent with the results obtained earlier for major california earthquakes we then synthesized the time history of ground acceleration by applying the stochastic simulation technique the agreement between the observed and predicted records was good for duration and spectral content we found however a strong systematic discrepancy with regard to peak acceleration namely for distances less than 50 km the predicted peak acceleration consistently overestimated the observed for sediment sites and underestimated it for the franciscan formation sites since the above systematic discrepancy applies to all the available stations within about 50 km from the hypocenter it is unlikely that the effect is due to the radiation pattern near source structure or topography it appears that the strong difference in the amplification factor between the franciscan and the sediment sites observed for weak motion disappears at acceleration levels higher than about 0 1 to 0 3 g if this is due to the nonlinear response of the sediment sites it is in the range expected from geotechnical engineering studies

last interglacial eemian hydrographic conditions in the southwestern baltic sea based on dinoflagellate cysts from ristinge klint denmark a dinoflagellate cyst record with strong mediterranean lusitanian affinities is described from marine deposits of eemian age last interglacial late pleistocene at ristinge klint denmark revealing new information about the hydrographic evolution of the southwestern baltic sea a revised correlation of the pollen record at ristinge klint with that of the annually laminated site at bispingen in northern germany provides temporal control approximately the first quarter of eemian time is represented a marine ingression into a lake took place during the quercus rise about 300years into the interglacial and is marked by low c 3 psu salinities at the base of the cyprina clay that increased progressively an abrupt and significant rise in the inflow of warm saline waters from the north sea occurred at about 750 years into the interglacial the corylus rise and at about 1900 years into the interglacial strongly stratified waters developed higher in the cyprina clay and continuing to its top at nearly 3000 years into the interglacial more open marine waters are indicated although fully marine conditions were not reached the dinoflagellate record throughout the cyprina clay at ristinge klint is therefore one of increasing marine influence summer sea surface temperatures approached and may have exceeded 26 28 c during early eemian time indicating temperatures at least 5 c warmer than at present these warm conditions persisted to the top of the record at ristinge klint no evidence exists at ristinge klint for the influence of arctic watermasses and the paucity of cold water species throughout the section reflects mild winter temperatures in the southwestern baltic sea the new species spiniferites ristingensis is formally described and the name operculodinium centrocarpum var cezare de vernal goyette rodrigues 1989 is validated

vegetation and climate in southern hemisphere mid latitudes since 210 ka new insights from marine and terrestrial pollen records from new zealand abstract paleo vegetation records developed from marine sedimentary sequences offer considerable potential for examining changes in terrestrial climate beyond the range of 14 c dating because they can be independently dated by 18 o stratigraphy here we present the first pollen record of vegetation from a marine core site in the tasman sea tan0513 14 42 18 s 169 53 e 110 km west of new zealand s south island an independent chronology provided by correlating the globigerina bulloides 18 o record at tan0513 14 to a global isotope stack shows that the record extends back to 210 ka glacial to interglacial changes in palynomorph content are characterised by shrub and podocarp broadleaf forest taxa respectively and are correlated with similar changes in the ca 150 kyr long terrestrial pollen record from okarito pakihi bog 110 km to the south southeast both records are placed on the same timescale by matching variations in dacrydium cupressinum and fuscospora between sites with a unique tie point provided by the ca 25 4 ka kawakawa tephra our southern hemisphere mid latitude vegetation records show forest extent is greatest during periods of low ice volume high mean annual sea surface temperature masst and anti phased with local insolation intensity however there are several features not attributable to changes in mean annual temperature first a fundamental change in forest composition occurred at termination ii tii with a loss of southern beech nothofagus from the study area second the amplitude of masst change through mis 5 is not reflected in corresponding changes in forest extent suggesting other feature s of regional climate seasonality frostiness ice cover exert important controls over vegetation patterns at these latitudes

how long and how stable was the last interglacial abstract surface ocean indicators in the north atlantic during marine isotope stage mis 5 correlate closely with the vegetational succession in northeastern france the melisey i silty layer which marks the end of the last interglacial biozone in la grande pile pollen record appears coeval with the polar front advance c24 registered in the core v29 191 by a sharply increased presence of ice rafted detritus and the cold water foraminifer neogloboquadrina pachyderma sinistral since this event is younger than the peak of mis 5d the last interglacial as recognized in northern france correlates not only with the mis 5e but also with a substantial part of mis 5d the last interglacial in la grande pile was twice as long as the holocene and the climate in its first half was apparently not less stable than during the current interglacial if the future natural climates were to develop as analogs of the past then the onset of the next glacial environments on land would be still many millennia ahead

nonlinearity at california generic soil sites from modeling recent strong motion data the average strong to weak motion amplification ratios during the 1989 loma prieta and 1987 whittier narrows earthquakes in california are estimated by modeling strong ground motions at soil sites in the linear response assumption and comparing the simulated and observed records the linear amplification function used to synthesize ground motions is the generic transfer function developed for california soil the database consists of 22 and 80 soil stations for the loma prieta and whittier narrows events respectively a statistically significant at 95 confidence reduction in amplification for the loma prieta event within 40 km from the fault is observed between approximately 1 and 3 hz examining individual strong to weak motion amplifications as a function of peak acceleration at the base of soil within this frequency range shows that detectable reduction in amplification occurs at accelerations above about 200 cm sec2 the strong motion amplification is reduced by a factor of 1 7 2 on average relative to a generic weak motion response the results of this study suggest the magnitude of the reduction in amplification caused by soil nonlinearity at large strain that can be expected on average at california soil sites

the origin and impact of the shizhuang ground fissure yingxian area datong basin china abstract the datong basin is part of the regionally extensive fenwei graben system a major tectonic zone impacted by active tectonics and the resulting damage to life and infrastructure the basin also contains the shizhuang ground fissure system in this study the likely origin surface extent and fissure subsurface characteristics are explored by traditional methods surveying mapping trenching drilling and seismic exploration the shizhuang ground fissure is located at the intersection of the xiaoshikou fault and the southern liuleng margin fault in yingxian county it has a length of 2 1 km excellent continuity and semi elliptical surface morphology the dislocation of strata induced by the fissure increases significantly as the depth increases the strata bend downward and form typical traction structures near the fissure plane indicating that the fissure has prominent synsedimentary fault characteristics the fissure causes serious damage to houses farmlands roads and public facilities featuring large tensile cracks and vertical dislocations the resulting data and interpretations indicate that 1 the ground fissures connect to two major subsurface active faults which lay the tectonic foundation for the fissure 2 accelerated groundwater extraction has reactivated the underlying faults and exacerbated fissure development and 3 mitigation is best achieved by cessation of excessive groundwater pumping appropriate engineering design and local avoidance for placement of critical structures this paper provides a heretofore generally unknown example promotes research on the mechanisms of fissures and has guiding significance for disaster prevention and reduction in this area

a tentative reconstruction of the last interglacial and glacial inception in greenland based on new gas measurements in the greenland ice core project grip ice core parameters the grip d 18 oice chronological sequence is obtained by comparing a new set of d 18 o of atmospheric o2 and ch4 measurements from the bottom section of the grip core with their counterpart in the vostok antarctic profiles this comparison clearly identifies ice from the penultimate glacial maximum mis 6 190 130 kyr b p in the grip core further it allows rough reconstruction of the last interglacial period and of the last glacial inception in greenland which appears to lay its antarctic counterpart our data suggest that while antarctica is already entering into a glaciation greenland is still experiencing a warm maximum during mis 5e index terms 1040 geochemistry isotopic composition chemistry 1827 hydrology glaciology 1863 3344 meteorology and atmospheric dynamics paleoclimatology keywords interglacial ice cap firn

tectonic geomorphology in the shanxi graben system northern china abstract the shanxi graben system is composed of a series of normal fault controlled basins which are arranged in an s shaped curve over a distance of about 1200 km active faults mainly trending nne ssw ne sw or ene wsw caused blocks to become rotated and tilted and river courses and terraces to become deformed volcanoes in the datong basin indicate that the formation of the shanxi graben system has a relationship to upper mantle activity and that the tectonic activity was intense during the middle pleistocene arrangement and movement of the faults indicates there has been right lateral shear in this area which may have resulted from the northward push of the qinghai tibet plateau

readjustment of leveling networks to account for vertical coseismic motions abstract in tectonically active regions the geodesist is confronted with the problem of updating heights where the earth s surface has been vertically deformed by an earthquake dislocation theory can be used as a basis for modeling coseismic elevation changes and be incorporated within a general least squares adjustment scheme to correct a network of old leveling measurements and heights that are within the deformed area releveling and information obtained from seismologists about the general nature of the earthquake serve as input to the modeling process fundamental equations and considerations are presented in this paper to develop dislocation models of vertical coseismic motions leveling data sets corresponding to the fairview peak nevada coalinga california and borah peak idaho earthquakes are analyzed these examples show potential for the method when applied in other areas even when the physical setting is made complex by ongoing subsidence the primary benefit of modeling coseismic motion is to avoid the cost of releveling for some lines in a deformed region rough modeling prior to any resurveying helps to select the lines to relevel that are most critical to a successful final model a good model for coseismic motion cannot restore geodetic levelings to their original reliability but corrected heights can be used in applications not requiring accuracy better than a few centimeters

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

characteristics of land subsidence earth fissures and related disaster chain effects with respect to urban hazards in xi an china the ancient capital of xi an is a typical city in china with a shortage of water resources with an urban population of 7 million its domestic and industrial use of water depends almost entirely on groundwater large scale long term extraction of groundwater has caused severe land subsidence and triggered the reactivation of active normal faults in the quaternary under consolidated sediments underlying the city this has further led to ground ruptures that have gradually evolved into earth fissure zones during this process there has been a close spatiotemporal relationship between land subsidence and the formation of earth fissures from field monitoring data the subsidence bowls are typically located in loess depressions between earth fissure zones within structural blocks of sediment cut by active quaternary faults and preexisting fault planes the subsidence bowls are generally elliptical in shape with the long axes consistent with the preferred orientation of the earth fissures the underlying quaternary active faults and preexisting fault planes predispose the intervening sediment blocks to formation of earth fissures and intense groundwater extraction has led to accelerated subsidence and earth fissuring during the past 50 years mining groundwater land subsidence and earth fissures occur in a sequence and constitute a disaster chain with respect to urban hazards in xi an thus it is important to understand the relationships between these events this paper summarizes the characteristics of land subsidence and earth fissures in xi an and discusses the chain of relationships that connects them

a nonlinear modeling and forecasting system of earth fractures based on coupling of artificial neural network and geographical information system exemplified by earth fractures in yuci city shanxi china earth fracturing or fissuring is a natural phenomenon and a major geohazard in many countries the factors that cause the earth to fracture were analyzed in yuci city in shanxi province of china using the geographical information system gis a nonlinear simulation and assessment model of earth fracturing was established using the artificial neural network ann technology to simulate the structure and function of the neural network nn of the human brain with engineering technology the developed nonlinear modeling and forecasting system was used to assess and forecast the earth fracture hazard in yuci city the results of this study provided useful and essential information for scientific policy making in the areas of city planning environmental protection and land development

the classic marine isotope substage 5e since its identi cation nearly fty years ago marine iso tope stage 5 mis 5 has been placed onto absolute time scaleson the basis of three independent approaches cesare emiliani who set up the isotope stages emiliani 1955 depended onuranium series dating of the sediments a method that today isregarded as not generally capable of yielding useful precisionor accuracy broecker and van donk 1970 pioneered the ap proach of correlating to radiometrically dated marine coral ter races thishasbeenmuchaidedinrecentyearsbyimprovementsin the precision and accuracy of these age determinations thathave owed from the development of thermal ionization massspectrometry tims for uranium series dating edwards

the last interglacial climate during the last 10 000 years the holocene has been relatively mild and stable in contrast the climate during the last interglacial is often portrayed as more variable but as kukla discusses in this perspective evidence for a more stable last interglacial is emerging furthermore the transition to the next glacial proceeded in stages and was not uniform across europe

distribution and generative mechanisms of ground fissures in china abstract in this study 5002 ground fissures in more than 1500 localities across 22 provinces in china are investigated and mapped to reveal their spatial distribution the distribution of these ground fissures in china exhibits six regular patterns assemblages in north china syngenesis in extensional basins clustering along fault zones distributing along geomorphic boundaries developed on the edge of subsidence areas and clustering in large and medium sized cities combined with regional gps numerical simulations physical model test and in sar monitoring the generative processes of ground fissures are analyzed and discussed in relationship to four mechanisms 1 deep dynamic tectonism controls on the location of ground fissures 2 intracontinental dynamic tectonism resulting in ground fissure assemblages 3 fault stress inducing formation of ground fissures and 4 groundwater overmining resulting in the reactivation and expansion of ground fissures the geological environment is thus responsible for the establishment and appearance of ground fissure more importantly ground fissure propagation in china is the result of the synergistic effects of internal geological dynamic including in deep tectonism intracontinental tectoniim and fault movement coupled with anthropomorphic stress this genetic model can be summarized as one that is tectonically controlled stress driven and affected by regional hydrodynamic

urban seismology northridge aftershocks recorded by multi scale arrays of portable digital seismographs we deployed portable digital seismographs in the san fernando valley sfv the los angeles basin lab and surrounding hills to record aftershocks of the 17 january 1994 northridge california earthquake the purpose of the deployment was to investigate factors relevant to seismic zonation in urban areas such as site amplification sedimentary basin effects and the variability of ground motion over short baselines we placed seismographs at 47 sites not all concurrently and recorded about 290 earthquakes with magnitudes up to 5 1 at five stations or more we deployed widely spaced stations for profiles across the san fernando valley as well as five dense arrays apertures of 200 to 500 m in areas of high damage such as the collapsed interstate 10 overpass sherman oaks and the collapsed parking garage at calstate northridge aftershock data analysis indicates a correlation of site amplification with mainshock damage we found several cases where the site amplification depended on the azimuth of the aftershock possibly indicating focusing from basin structures for the parking garage array we found large ground motion variabilities a factor of 2 over 200 m distances for sites on the same mapped soil unit array analysis of the aftershock seismograms demonstrates that sizable arrivals after the direct s waves consist of surface waves traveling from the same azimuth as that of the epicenter these surface waves increase the duration of motions and can have frequencies as high as about 4 hz for the events studied here we do not observe large arrivals reflected from the southern edge of the san fernando valley

the last interglacial glacial cycle mis 5 2 re examined based on long proxy records from central and northern europe abstract current multi proxy studies on a long sediment sequence preserved at sokli n finland i e in the central area of fennoscandian glaciations are drastically changing classic ideas of glaciations vegetation and climate in northern europe during the late pleistocene the sediments in the sokli basin have escaped major glacial erosion due to non typical bedrock conditions in this review the sokli record is compared in great detail with other long proxy records from central temperate and northern boreal europe these comprise the classic records of la grande pile e france and oerel n germany and more recently obtained records from horoszki duze e poland and lake yamozero nw russia the focus of the review is on pollen lithology and macrofossil and insect based temperature inferences the long records are further compared with recent proxy data from nearby terrestrial sites as well as with the rapidly accumulating high resolution proxy data from the ocean realm the comparison allows a re examination of the environmental history and climate evolution of the last interglacial glacial li g cycle mis 5 2 it shows that environmental and climate conditions during mis 5 ca 130 70 ka bp were distinctly different from those during mis 4 2 ca 70 15 ka bp mis 5 is characterized by three long forested intervals broadly corresponding to mis 5e 5c 5a both in temperate and northern boreal europe these mild periods were interrupted by two short relatively cold and dry intervals mis 5d and 5b with mountain centered glaciation in fennoscandia millennial scale climate events were superimposed upon these longer lasting climate fluctuations the time interval encompassing mis 4 2 shows open vegetation it is characterized by two glacial maxima mis 4 and 2 with sub continental scale glaciation over northern europe and dry conditions in strongly continental eastern european settings high amplitude climate oscillations of millennial duration characterized the climate variability of mis 3 mild climate conditions in early mis 3 caused large scale deglaciation of the fennoscandian ice sheet and ice free conditions with betula dominated vegetation including tree birch persisted over large parts of fennoscandia possibly interrupted by glaciation during major part of mis 3 till ca 35 ka bp overall mis 5 was mostly mild with warmest or peak interglacial conditions at the very start during mis 5e mis 4 2 was mostly cold with most extreme or peak glacial conditions in the closing phase during mis 2 this points to a subdivision of the last climate cycle into an early overall mild interglacial half and a late overall cold glacial half each with duration of ca 50 ka this review also shows that the climate variability in central and northern europe during the li g cycle was mostly in degrees of continentality with major shifts in winter temperature and precipitation values summer temperatures on the other hand remained largely unchanged it points to the waxing and waning of sea ice over the north atlantic ocean as a possible characteristic feature of the late pleistocene the present compilation based on long terrestrial sequences high resolution multi proxy data from the oceans and quantified paleo climate data strongly favors a definition of entire marine oxygen isotope stage 5 as the last interglacial similar as in the original marine stratigraphy and the stratigraphy at la grande pile in france the proxy based climate data places the start of the last glacial at the base of mis 4 and the northwest european pleniglacial it shows that the division between the eemian mis 5e and the early weichselian mis 5d a is not useful as not relevant from a climate point of view

signatures of the seismic source in emd based characterization of the 1994 northridge california earthquake recordings in this article we use empirical mode decomposition emd to charac terize the 1994 northridge california earthquake records and investigate the sig natures carried over from the source rupture process comparison of the current study results with existing source inverse solutions that use traditional data processing suggests that the emd based characterization contains information that sheds light on aspects of the earthquake rupture process we first summarize the fundamentals of the emd and illustrate its features through the analysis of a hypothetical and a real record typically the northridge strong motion records are decomposed into eight or nine intrinsic mode functions imf s each of which emphasizes a different oscillation mode with different amplitude and frequency content the first imf has the highest frequency content frequency content decreases with an increase in imf component with the aid of a finite fault inversion method we then examine aspects of the source of the 1994 northridge earthquake that are reflected in the second to fifth imf components this study shows that the second imf is predominantly wave motion generated near the hypocenter with high frequency content that might be related to a large stress drop associated with the initiation of the earthquake as one progresses from the second to the fifth imf component there is a general migration of the source region away from the hypocenter with associated longer period signals as the rupture propagates this study suggests that the different imf components carry information on the earthquake rupture process that is expressed in their different frequency bands

increasing vegetation and climate gradient in western europe over the last glacial inception 122 110 ka data model comparison high resolution terrestrial pollen and marine planktic and benthic isotopes coarse fraction and n pachyderma s analyses have been performed in the marine isotope stage mis 5 interval of images core md99 2331 retrieved in the northwestern iberian margin this study shows the occurrence of a zeifen interstadial stadial succession on land and in the ocean during the first part of mis 5e in northwestern iberia the eemian is marked from 126 to 122 ka by the development of deciduous quercus forest at the same time as mediterranean forest colonised southern iberia and deciduous quercus corylus forest occupied northernmost european regions from 121 to 115 ka carpinus betulus forest developed in nw iberia indicating a winter cooling by 2degreesc on land and an increase in annual precipitation by 100 200 min along with a sea surface temperature sst decreasing trend off iberia a similar cooling has been documented at the same time in northern germany 52degreesn by the replacement of deciduous forest by coniferous abies picea formations implying a southward displacement of the deciduous tree line between similar to60degreesn and 50degreesn as early as 120 ka the southward migration of the tree line between 72degreesn and 58degreesn simulated by the earth model of intermediate complexity mobidic from 122 and 120 ka and considered as a major process to initiate the last glaciation is therefore compatible with data between 115 and 110 ka the substantial ice accumulation in northern high latitudes mis 5e 5d transition was synchronous with successive drops c26 and c25 in northeastern atlantic sst in northwestern iberia abies pinus trees developed at the expense of quercus carpinus forest a tundra like environment occupied northern germany marking the end of the interglacial in northwestern europe at 115 ka and boreal forest likely colonised northeastern france the first displacement of the vegetation belts at 121 ka was enhanced at 115 ka indicating an amplification of the vegetation and climate gradients in northeastern atlantic and european borderlands probably related with the well developed ice caps at that time the comparison between the general trend in the estimated and simulated mobidic winter and summer temperatures for latitudes between 35 and 45degreesn shows that both follow quite straightforwardly the precession signal although the simulated and reconstructed temperatures agree better in the south than north of 40degreesn annual precipitation is exhibiting opposite trend in the data and in the model this contradiction is likely the fact that the zonal climate simulated by the model may not accurately represent the regional climate features as reconstructed from the pollen c 2004 elsevier b v all rights reserved

site response for urban los angeles using aftershocks of the northridge earthquake ground motion records from aftershocks of the 1994 northridge earthquake are used to estimate site response in the urban los angeles area over 1300 shear wave records from 61 sources and 90 sites are used in a linear inversion for source and site response spectra the methodology makes no assumptions about the shape of the source spectrum to obtain a stable unique inverse a q model and geometrical spreading factor are assumed in addition the site response at a hard rock site is constrained to be approximately 1 0 with a kappa of 0 02 the site response spectra compare favorably with the results of previous and on going investigations in los angeles a couple of first order effects are lower site response in the surrounding mountains dominated by mesozoic and tertiary rocks and higher values in the san fernando and los angeles basins containing surficial pleistocene and holocene alluvial deposits results show good correlation of high site response spectral values with localized areas of severe damage interstate 10 collapse sherman oaks northridge interstate 5 14 collapse however widespread trends in site response across the sedimentary basins are not obvious the data suggest that site responses are lower near the southern margin of the san fernando valley for sources to the north due to north dipping sedimentary structures but the general pattern of site response is characterized by high variability on length scales less than a kilometer variations of a factor of 2 in site response are observed over the length scale of 200 m and for the same surficial geologic unit for some of the alluvial basin sites surface wave generation is a significant contributor to elevated site response at lower frequencies below 2 hz the total damage pattern for the northridge earthquake is influenced by strong source directivity to the north and strong local site effects the correlation of weak motion site response estimates with areas of significant damage demonstrates the value of these field measurements in future urban planning and in the reduction of seismic risk in urban areas

stochastic finite fault modeling of ground motions from the 1999 chi chi taiwan earthquake application to rock and soil sites with implications for nonlinear site response the stochastic method for simulating strong ground motions from finite faults is applied to the records of the 1999 chi chi taiwan earthquake the method involves discretization of the fault plane into smaller subfaults each of which is assigned an x 2 spectrum the contributions from all subfaults are empirically atten uated to the observation site and summed to produce the synthetic acceleration time history the method is initially calibrated against the data recorded at 24 rock sites located within 7 120 km from the mainshock hypocenter and providing a broad azimuthal coverage of the fault plane the accuracy of the simulations is quantified through the model bias defined as the logarithm of the ratio of the observed to simulated spectrum averaged over all stations the calibrated model for the chi chi event has a near zero average bias in reproducing the ground motions at rock sites in the frequency range from 0 1 to 20 hz an unusually low value is found for the radiation strength factor s controlling the high frequency radiation level and directly related to the maximum slip velocity on the fault compared with the mean value found for north american earthquakes this result reflects the observed low peak ground ac celerations of the chi chi mainshock and physically its lower than usual slip ve locities the calibrated model is then used to simulate soil site site class d records using the linear response assumption the simulated soil site input motions are amplified by the weak motion amplification functions estimated by the spectral ratio technique from available aftershock records this analysis reveals an average reduction in strong motion amplification to about 0 5 0 6 of that in weak motions with an ac celeration threshold for detectable nonlinearity near 200 300 cm sec 2 however the derivation of soil site specific weak motion amplification was limited by the amount of aftershock data available further improvement in the quantification of nonlinear soil response during the chi chi earthquake may be possible with the release of additional aftershock datasets

modern ground failure in the garlock fault zone fremont valley california modern ground failures ranging from renewed displacement on 2 5 km long fault scarps to 1 km long tension cracks occur in fremont valley california most of the failures formed along pre existing holocene fault scarps that are part of the tectonically active garlock fault system the failures began to form in the 1960s and currently affect an area of 17 km 2 that is coincident with ground water level decline induced by pumping for crop irrigation several observations indicate that these failures were caused by water level decline rather than natural tectonism first modern ground failure began after water level started to decline and was restricted to the area affected by decline land subsidence was associated with this decline and appears to be caused by aquifer compaction second geodetic monitoring from 1977 to 1982 of faults near the center of the cone of depression demonstrated that fault creep occurred during periods of seasonal water level decline and stopped during periods of seasonal water level recovery by contrast faults near the margin of the cone of depression where water levels declined at a constant rate moved at a steady rate third surface strain fields near failures suggest that subsurface fault associated deformation was restricted to aquifer level depths and fourth seasonal rebound of the land surface across one fault was caused by elastic expansion of the aquifer system that was induced by large seasonal water level recovery

site amplification at avcilar istanbul avcvlar is the suburb of istanbul that was most heavily damaged during the august 17 1999 mw 7 4 izmit earthquake strong ground motion caused fatalities and damage in avcvlar despite being 90 km from the epicenter we deployed five portable seismograph stations equipped with reftek 24 bit recorders and l4c 3d seismometers for 2 months in order to understand why the local site response was different from elsewhere in istanbul a reference station was placed on a hard rock site and the remaining four stations were placed on other geological units in areas that had experienced varying levels of damage we calculated frequency dependent ground amplification curves by taking the ratios of the spectra at soft and hard rock sites we obtained similar site response curves for most earthquakes at each site in the frequency range of 0 3 1 6 hz and observed no significant site amplification beyond 2 0 hz at any site the overall characteristics of the recorded s waveforms and our modeling of the calculated site amplification curves are consistent with amplification as a result of trapping of seismic energy within a 100 150 m thick low velocity subsurface layer we also review the applicability of microtremor measurements to estimate local site effects at avcvlar for these data we used ratios of spectra of horizontal to vertical components to obtain each site response these results are compared with standard spectral ratios these microtremor measurements provide consistent estimates of the amplification at most sites at the higher end of the frequency band namely above 1 hz the results from both methods indeed agree well in this part of the frequency band however the microtremor method fails to detect amplification at lower frequencies namely b1 0 hz d 2004 elsevier b v all rights reserved

properties of vertical ground motions a typical engineering approach to developing site specific design vertical ground motions starts with rock outcrop horizontal motions converts them into the vertical component using an empirical vertical to horizontal v h ratio for response spectra and propagates the resulting motion through the soil column as a vertically incident p wave in the absence of data on strain dependent soil properties in compressional deformation strain compatible shear wave properties from the horizontal component analyses are utilized this approach makes two assumptions 1 that the vertical motions are primarily composed of compressional waves and 2 that strain dependent material properties in shear deformation can be extrapolated to compressional deformation our study deals with the empirical validation of both assumptions first we investigated the ratio of sv to p wave spectra of the vertical component of ground motions from significant recent events in california to find which wave type predominantly contributed to vertical motions in the frequency range of 0 5 25 hz the results indicate that shear waves dominate the vertical motions at frequencies up to approximately 10 hz above which the contribution of compressional deformation is about as strong or greater this result holds for both soil and rock sites second using the data from the kik net borehole arrays in japan we estimated the nonlinearity in compressional deformation by studying p wave amplification at variable amplitude levels frequency shifts and in some instances reduced amplification compatible with the hysteretic softening type of nonlinearity known for shear waves is found as the amplitude of compressional strain increases a tentative curve of constrained modulus reduction is also similar to the existing shear modulus reduction curves the results of this study suggest that for most practical applications vertical motions can be modeled as nonvertically propagating sv waves this could be implemented through conventional one dimensional horizontal component modeling using shake and the application of empirical depth dependent v h correction factors to account for the inclined propagation path at high frequencies vertical motions may have to be modeled as near vertically propagating p waves with strain dependent properties specifically developed for compressional deformation however these frequencies may be of lesser importance for design applications manuscript received 11 january 2002

millennial and orbital scale climate variability in southeastern united states and in the subtropical atlantic during marine isotope stage 5 evidence from pollen and isotopes in odp site 1059 abstract we present directly correlative high resolution pollen and isotopic data from marine isotope stage mis 5 from a marine core taken on the continental margin off the southeastern united states 31 40 n 75 24 w 2985 m these data provide the first chronostratigraphically controlled pollen data for the last interglacial from this region comparison of the pollen and benthic isotope stratigraphies demonstrate that vegetation and climate development in southeastern united states did not always coincide with global ice volume changes deglacial terrestrial climate amelioration which was nearly synchronous with ice decay peaked slightly before the ice volume minimum in mis 5e cooling in the latter part of the last interglacial began at c27 prior to ice growth vegetation and climate were not stable during mis 5e suborbital climate oscillations persisted throughout mis 5 both onshore and in the subtropical atlantic offshore the largest correlative suborbital oscillations in the pinus pine and quercus oak forests of coastal georgia and south carolina and sea surface variability correspond to stadial interstadials documented in greenland ice cores however coupled oscillations also occur more frequently

development characteristics and mechanisms of the taigu qixian earth fissure group in the taiyuan basin china since the 1980s increasing human activity and continuing over exploitation of groundwater resources have caused the earth fissures in the rift basin in shanxi china to enter an active phase buildings along these earth fissures have been seriously damaged four massive earth fissures that developed in the taigu and qixian areas of the eastern taiyuan basin endanger the operational safety of the high speed railway that passes through this region using field observations measurements and exploration we determined that the four earth fissures are parallel to each other have a northeast trend and are separated by approximately equal distances the rupture zones of these earth fissures are generally 10 50 m wide and are formed by the main fissures and secondary fissures the width of the zone affected by the earth fissures is 20 50 m based on deformation and the damage done to buildings these fissures formed on the earth s surface their hanging walls are lower than their foot walls forming normal faults and the ground surface around the fissures exhibits ridges and depressions the fissures are connected to deep hidden faults the fault displacement increases with increasing depth which is characteristic of syn sedimentary faults these earth fissures are characterized by vertical displacement and their average annual activity rate is 1 3 cm we believe that the formation of this large scale fissure group may be related to the tectonic structure of the hidden faults in the basin and may also be affected by the continuous regional extensional stress of the basin the current increased level of activity could be caused by the over exploitation of groundwater in the area

stochastic finite fault modeling of ground motions from the 1994 northridge california earthquake ii widespread nonlinear response at soil sites on average soil sites behaved nonlinearly during the m 6 7 1994 north ridge california earthquake this conclusion follows from an analysis that combines elements of two independent lines of investigation first we apply the stochastic finite fault simulation method calibrated with 28 rock site recordings of the north ridge mainshock to the simulation of the input motions to the soil sites that recorded this event the calibrated model has a near zero average bias in reproducing ground motions at rock sites in the frequency range from 0 1 to 12 5 hz the soil sites selected are those where there is colocation of strong motion acce lerographs and temporary instruments from the northridge aftershock observation network at these sites weak motion amplification functions based on numerous aftershock records have been empirically determined in three separate investigations reported in the literature these empirical weak motion amplification factors can be applied to the simulated input rock motions at each soil site to determine the ex pected motions during the mainshock i e neglecting nonlinearity these expected motions can then be compared to the actual recordings during the mainshock this analysis shows that the recorded strong motion spectra are significantly over estimated if weak motion amplifications are used the null hypothesis stating that the inferred differences between weak and strong motion amplifications are statis tically insignificant is rejected with 95 confidence in the frequency range from approximately 2 2 to 10 hz on average the difference between weak and strong motion amplifications is a factor of 2 nonlinear response at those soil stations for which the input peak acceleration exceeded 150 to 200 cm sec 2 contributes most to this observed average difference these findings suggest a significant nonlinear re sponse at soil stations in the los angeles urban area during the northridge main shock the effect is consistent with the increase in damping of shear waves at high levels of strain which is well known from geotechnical studies of soil properties

magnitude of nonlinear sediment response in los angeles basin during the 1994 northridge california earthquake the study of nonlinear site response has practical difficulties due to large ambiguities in isolating local response from other competing effects we chose a sedimentary site lf6 in los angeles basin that 1 has the closest reference rock sites available compared to other stations allowing an accurate estimation of local amplification and 2 illustrates clear resonance in the near surface in our opinion this case represents the least ambiguity in the identification of possible nonlinearity the site responses during the northridge the 1987 whittier narrows events and the northridge aftershocks are compared the station shows a fundamental resonance frequency change between the higher and lower amplitude motions in the entire ensemble of 17 events used the net shear modulus reduction during the northridge event is a factor of 1 3 to 1 4 compared to the whittier narrows event and is a factor of 1 7 compared to the aftershocks this result provides guidance of what to expect at other sites in the basin where the nonlinear response is less easy to characterize

high resolution palynological record off the iberian margin direct land sea correlation for the last interglacial complex abstract we present high resolution pollen dinocyst and isotopic data for the last interglacial complex from marine core md952042 southwestern margin of the iberian peninsula 37 48 n 10 10 w 3148 m direct land sea correlation from this core indicates that during this period north atlantic sea surface temperatures were in phase with iberian climate our palynological analysis suggests a younger dryas like event at the marine isotope stage mis 6 5 transition the analysis also indicates that the eemian spans from the lightest isotopic values of mis 5e ca 126 ky bp to the heavier isotopic values towards the mis 5e 5d transition therefore the eemian is not entirely equivalent to mis 5e pollen analysis identifies four climatic phases of low amplitude during the eemian a mediterranean climate in southwestern europe is gradually replaced by oceanic conditions the middle of the eemian is characterized by an increase in precipitation on the land and ocean associated with a slight cooling this seems to be the result of a displacement of the polar front as far south as southern europe during this period after the eemian three relatively short climatic phases on land melisey i st germain ia and montaigu cold event occurred contemporaneously with three shifts of sea surface temperatures the montaigu event first identified in terrestrial pollen sequences is therefore also recorded in core md952042 on the basis of pollen dinocyst and planktonic isotopic data our results also show that the warm periods of mis 5 are not characterized by similar climatic conditions on land

millennial scale climate variability during the last interglacial recorded in a speleothem from south western france abstract a stalagmite bdinf recovered from an archaeological cave bourgeois delaunay la chaise de vouthon in sw france provides a rare high resolution precisely dated continental palaeoclimate record covering the warmest part of the last interglacial 128 1 121 1 ka the growth interval spans the pluvial period recorded in soreq and peqiin cave speleothems during sapropel event s5 suggesting that the eastern mediterranean and western europe experienced relatively wet conditions simultaneously during this part of the last interglacial stable oxygen and carbon isotope ratios from bdinf show prominent millennial scale variations which are interpreted respectively in terms of changes in the amount of rainfall reaching the cave and soil biological activity the timing of the oxygen isotope changes agrees with similar excursions recorded in speleothems from corchia cave italy where close coupling between rainfall amount and regional sea surface temperatures has been demonstrated three warmer wetter periods are interspersed with four cooler drier periods the first warmer wetter period is the most prominent as is the case at corchia and coincides with the sst optimum off western europe this is followed by a prominent cooler drier excursion centred on 126 ka which can be linked to a period of increased loess deposition recorded in annually laminated lake sediments from eifel germany although there is already ample evidence for last interglacial climate instability we show for the first time that specific climatic events occurred more or less synchronously between southwestern europe central mediterranean italy and northern europe germany

a comparative ground response study near los angeles using recordings of nevada nuclear tests and the 1971 san fernando earthquake a comparative ground response study at sites in the los angeles region is based on the extensive strong motion data set recorded in the 1971 san fernando earthquake and 159 three component recordings of distant nuclear tests in nevada amplitude spectral ratios computed for the nuclear test data over those frequency bands for which there is an adequate signal to noise ratio provide statistically stable estimates of the local ground response related to the type of local geologic conditions comparison of the strong motion data recorded from the 1971 san fernando earthquake with that recorded at 28 of the same sites for the nuclear tests show that the corresponding amplitude spectral ratios are statistically equivalent for most sites provided reference stations are chosen to minimize effects on the earthquake data of azimuthal source variations and crustal propagation path statistical equivalence of the spectral ratios for the two types of data sources suggests that amplitude spectral ratios computed with respect to the appropriate reference station provide a first order estimate of local ground response

ground cracks in ethiopian rift valley facts and uncertainties abstract no accurate relationship has been obtained in this study between ground cracks in ethiopian rift valley and the most common causes of earth fissures such as aquifer system compaction and increased horizontal seepage stresses this is due to the fact that the level of groundwater withdrawal responsible for these processes is still negligible in ethiopia if aquifer system compaction and increased horizontal seepage stresses have a certain role then it should be through the long term effect of groundwater flow from basins to neighboring lakes the ground cracks appeared also not to have a direct link with active faulting or distant earthquakes structurally the ethiopian rift valley is dominated by ne sw trending tensional faults but no evidence is obtained in this study to associate the process of surface cracking with major tectonics however an aseismic elastic strain which originates at depth and propagates upward through sediments without the formation of bedrock faults could result in conditions conducive to the development of cracks then fissures might ultimately be created after heavy rainfalls by near surface processes such as piping and hydrocompaction along water line sources

nonlinear soil response a reality geotechnical models consistently indicate that the stress strain relationship of soils is nonlinear and hysteretic especially at shear strains larger than 10 5 to 10 4 nonlinear effects such as an increase in damping and reduction in shear wave velocity as excitation strength increases are commonly recognized in the dynamic loading of soils on the other hand these effects are usually ignored in seismological models of ground motion prediction because of the lack of compelling corroborative evidence from strong motion observations the situation is being changed by recently obtained data explicit evidence of strong motion deamplification accompanied by changes in resonant frequencies are found in the data from the 1985 michoacan mexico and the 1989 loma prieta california earthquakes the events recorded by the vertical and surface accelerograph arrays in taiwan as well as a number of other events throughout the world evidence of nonlinear behavior becomes apparent beyond a threshold acceleration of 100 to 200 gal nonlinearity is considerable in cohesionless soil but may be negligible in stiff soils the findings of recent years indicate that nonlinear site effects are more common than previously recognized in strong motion seismology

diatom responses to limnological and climatic changes at ribains maar french massif central during the eemian and early wurm abstract high resolution diatom analysis was carried out to assess the limnological and climatic changes that took place at ribains maar french massif central during the late pleistocene 131 105 ka bp with a focus on the eemian interglacial in particular numerical analyses were used to show that most of the variability in the fossil diatom assemblages was due to climate independently from the changes in the lake catchment vegetation as represented by pollen data diatom based quantitative reconstructions of the past limnological conditions as well as a comprehensive literature review on the auto ecological requirements for the principal diatom taxa were used to interpret the record an absolute time scale for the sequence was derived by matching the major pollen shifts with the radiometrically dated changes in oxygen isotopes observed in italian stalagmites this study shows that at ribains maar the transition from the riss saalian glacial to the eemian interglacial was marked by a gradual increase in the contribution of spring blooming diatom species indicating a longer growing season and milder winter spring conditions at that time a short cooling event interrupts this trend and may correspond to a stadial at the start of the eemian a peak in benthic taxa and the suppression of spring blooming flora probably reflects the effects of deglaciation on the catchment during the eemian interglacial itself three main phases were distinguished within the diatom record the first phase 8000 years in duration was dominated by stephanodiscus minutulus which suggests that intense mixing in the water column took place during spring the pollen record was simultaneously dominated by quercus and corylus that typify this phase as the climatic optimum of the eemian the second phase almost equal in duration to the first phase 7000 years is generally dominated by cyclotella taxa and suggests a less productive lake and much reduced period of spring mixing compared with the first phase in the pollen diagram this corresponds to an interval dominated by carpinus picea abies that indicates a cooler and wetter climate the third and last phase of the eemian 2000 year long saw the return to stephanodiscus dominated assemblages indicating a warming that may correspond to the dansgaard oeschger event 25 identified in the greenland ice core record in the early stage of the wurm glacial weichselian assemblages in the melisey i stadial 3000 year long were dominated by either aulacoseira subarctica or asterionella formosa which suggest colder spring conditions than during the late eemian but not as cold as the ones indicated by the pollen record stephanodiscus spp again dominate during the saint germain ia interstadial 5000 year long suggesting a return to the conditions that prevailed before the melisey stadial in agreement with the pollen record the record ends with the montaigu cold event which is characterised by a pinus peak in the pollen record and corresponds to a large abundance of a subarctica in the diatom sequence throughout the eemian the abundance of stephanodiscus spp which is thought to be driven by winter conditions show cyclic fluctuations that most likely match the cooling events identified in a pollen record from germany variation in insolation throughout the eemian may have been the driving factor behind the species succession observed in the diatom sequence while this study demonstrates that diatom analysis of lake sediment can provide very detailed information on long term climate change a review of the few other diatom investigations published on european eemian deposits shows that this technique has been so far seldom used to its full potential in this context in central and southern europe

finite difference modeling of two aftershocks of the 1994 northridge california earthquake recent evidence for nonlinear behavior of strong motions generated by the northridge california earthquake relies explicitly on the analysis of aftershock data thus correcting these observations for propagational and source effects becomes a crucial step in these studies here we demonstrate that the dipping structure near the edges of the san fernando valley can strongly alter the local site responses especially for shallow events we model two aftershocks with similar epicenters but with shallow 4 km and deep 16 km hypocentral depths waveforms from 12 portable instruments deployed across the basin and recording these events were processed and studied in the 0 3 4 hz bandpass for the shallow event distinctive features are a broad direct s phase and large amplitude surface waves at the basin stations and high frequency s phases at stations in the santa monica mountains the deep event is less strongly affected by the basin but displays strong evidence of the source radiation pattern an array analysis indicates 2d propagation for most of the strong arrivals some of these features are explained by a simple 2d basin model containing a strong shallow contrast a factor of 2 jump in seismic velocity at a depth of 1 km within the basin and a moderate deeper gradient

some fluidized landslides triggered by the 2011 tohoku earthquake mw 9 0 japan abstract the 2011 tohoku earthquake off the pacific coast of japan generated a large tsunami and many landslides resulting in a great number of casualties although almost all casualties resulted from the tsunami some long travel fluidized small scale landslides also killed 13 people after the earthquake we surveyed seven of these catastrophic landslides triggered by the earthquake we found that most of them have nearly identical geological features with slopes consisting of pyroclastic deposits formed at different times and with a palaeosol layer that outcropped in most cases after the landslide above the palaeosol there are layers of pumice and scoria the palaeosol had a natural moisture content of 160 and the pumice and scoria had a moisture content of 145 from field observations we concluded that the sliding surface originated in the very upper part of palaeosol and liquefaction occurred in both layers resulting in the fluidization of displaced landslides to examine the trigger and movement mechanism of these landslides we monitored the ground motion of one landslide area during the many aftershocks and compared the results with records obtained by a national seismic station nearby we inferred that strong seismic motion occurred in the landslide area during the main shock we sampled the palaeosol and pyroclastic deposits and performed undrained static cyclic shear tests on the materials both in a saturated state and at natural moisture content the results indicate that high pore water pressure was generated resulting in decreased shear strength even in samples with the natural moisture content the shear strength of the palaeosol lowered to a very small value with continuous increase of shear rate enabling the high mobility of the displaced landslide materials

palynostratigraphy of the last interglacial glacial cycle in germany abstract the last interglacial glacial cycle comprises the eemian and the weichselian in the area of the scandinavian glaciation respectively the riss wurm and the wurm in southern germany drastic changes of the vegetation have occurred several times during this period in europe the best known in germany is the development of the forests of the last interglacial stage and of the two succeeding early glacial interstadial phases the brorup and the odderade above the odderade sediments of two more middle weichselian interstadials the oerel and the glinde with a shrub tundra vegetation have been found at one site in northern germany in southern germany the palynological record ends somewhat earlier i e with the equivalent of the oerel interstadial which here in the south had a forest vegetation numerous single occurrences of interstadial sediments of different age and vegetation have been studied but unfortunately their stratigraphic position is most frequently unclear therefore a general survey can only rely on few but long sequences their comparison shows that vegetational gradients of different steepness existed at different times which mirror the changing climatic gradients of this period the main points of the vegetational zonation as far as it is known from germany for the cycle are summarized

the last climatic cycle at la grande pile vosges france a new pollen profile a new pollen diagram has been made from an old unanalyzed core from la grande pile gp xx correlations with the previous work of woillard 1975 1978 leads to the following conclusions the end of the eemian was marked by a minor climatic change prior to the melisey i stadial the ognon ii and ognon iii interstadials are not consistent and correspond to the level of reworking of mesophilous taxa during the last pleniglacial the limitations of the botanical interpretation of pollen spectra from the last pleniglacial are underlined lastly bruckenthalia and larix are identified for the first time at la grande pile the respective roles of these taxa following the eemian are additional arguments for correlating the st germain i and ii with the early weichsel interstadials in the north of middle europe

rissian eemian and wurmian coleoptera assemblages from la grande pile vosges france abstract the grande pile peat bog sequence is one of the few west european sites that cover the entire time span of the last major climatic cycle 140 000 years a recent program of coring has provided material for insect analysis the aim of this palaeoentomological study is to interpret the environmental and climatic evolution from the end of the rissian glaciation to the holocene using subfossil coleoptera the studied samples yielded 394 taxa of coleoptera half of them identified to species level 19 of which do not belong to the present day french fauna the large number of taxa suggests a wide variety of habitats and provides much detailed palaeoecological evidence for the period studied the lowermost sediments of the sequence corresponding to the end of the rissian glaciation were deposited under very cold conditions in a tundra environment this is succeeded by a forest period in which two cool interludes of grassland environment occur although these periods are decidedly poor in tree dependent coleoptera they do not contain any really cold adapted taxa they divide the forest phase into three periods the first one corresponding to the eemian interglacial shows an early stage in which the beetle fauna is characterized by species dependent on deciduous trees a later stage in which this fauna is mixed with many conifer dependent elements some of which e g platypus oxyurus suggest warmer and perhaps wetter climatic condition than today the two later woodland periods yielded coleopteran assemblages rather similar to those recorded in the second part of the eemian i e with both deciduous and conifer dependent taxa there is some evidence to suggest that these two periods were slightly cooler than the eemian proper marked climatic deterioration becomes obvious in the upper half of the sedimentary sequence attributed to the last glacial period wurm with the reappearance of tundra beetle assemblages sediment and insect evidence suggest that the climate was extremely cold and continental at la grande pile at about 30 000 b p a comparison of the insect analysis with previous palynological works enables precise correlation between the results provided by these two independent approaches however large numbers of running water coleoptera in the forest periods replaced by standing water coleoptera in cold periods raise questions concerning the lacustrine origin of the sedimentation at la grande pile

problems of the duration of the eemian interglacial in europe north of the alps abstract suggestions that the duration of the eemian interglacial was about 11 000 yr based on annually laminated sediment sequences in germany have been challenged in favor of a much longer interval however biostratigraphic evidence demonstrates why the eemian sequences at grande pile and ribains cannot be reliably used for alignment with the marine sequence as applied by kukla et al 2002 this issue to estimate the duration of this interglacial the long chronology they propose would imply not just coniferous but for up to 5000 yr fully temperate forest in central france coexisting with treeless heath and steppe tundra conditions in northwestern europe an unlikely climatic and ecological scenario the proposal that the eemian interglacial in western europe lasted for 17 000 or even 23 000 yr is rejected a duration of no more than 13 000 yr is preferred at least for sites north of the alps and pyrenees the duration of temperate conditions in the mediterranean region is less certain

a study of the symbiotic relationship between tectonic fissures and faults in the fenwei graben system china the fenwei graben system is an important extensional fault depression zone which is the tectonic boundary between the ordos block and the south china block and the north china block the graben system presents an s shape with a total length of 1200 km and a width of 30 60 km and an overall strike of nne due to complex tectonic background and active faults nearly 612 ground fissures develop in these basins and more than 90 of these ground fissures are tectonic fissures which are closely associated with fault activities to reveal the plane symbiotic phenomena profile symbiotic modes and symbiotic mechanism between tectonic fissures and faults in the fenwei graben system the developmental characteristics were investigated in detail by surveying mapping trenching and drilling in the study area the main conclusions are as follows 1 the tectonic fissures of the fenwei graben system are mainly distributed along the margin faults of basins the boundary faults between blocks and the hidden faults within blocks causing serious damages to farmlands houses and roads the symbiosis between these fissures and faults is obvious on the surface 2 the profile symbiotic morphology includes vertical extension type syncline and anticline y type and stepped type 3 the symbiotic mechanisms include vertical growth lateral rupture and clustery derivation 4 the activities of underlying faults give impetus to the formation and expansion of tectonic fissures the exposure of the fissures makes underlying faults continue to develop in the form of surface fractures

evidence for general instability of past climate from a 250 kyr ice core record recent results1 2 from two ice cores drilled in central greenland have revealed large abrupt climate changes of at least regional extent during the late stages of the last glaciation suggesting that climate in the north atlantic region is able to reorganize itself rapidly perhaps even within a few decades here we present a detailed stable isotope record for the full length of the greenland ice core project summit ice core extending over the past 250 kyr according to a calculated timescale we find that climate instability was not confined to the last glaciation but appears also to have been marked during the last interglacial as explored more fully in a companion paper3 and during the previous saale holstein glacial cycle this is in contrast with the extreme stability of the holocene suggesting that recent climate stability may be the exception rather than the rule the last interglacial seems to have lasted longer than is implied by the deep sea specmap record4 in agreement with other land based observations5 6 we suggest that climate instability in the early part of the last interglacial may have delayed the melting of the saalean ice sheets in america and eurasia perhaps accounting for this discrepancy

north atlantic current and european environments during the declining stage of the last interglacial this paper provides a tentative reconstruction of environmental shifts in europe associated with changes of the north atlantic current and related meridional sea surface temperature sst gradients during most of the eemian interglacial ca 126 115 ka the north atlantic current extended far north into the nordic seas and european environments were comparable to those of the holocene however ca 115 ka an sst drop in the nordic seas marked a southward displacement of the north atlantic current this hydrographic shift was associated with substantial cooling in northern europe and drier conditions in the mediterranean region the polar timberline retreated southward from 69 n in northernmost scandinavia to 52 n in central europe and thermophilous deciduous trees became extinct north of the 48th parallel woodlands persisted in southern europe for another 5 k y well into marine isotope substage 5d these conditions indicate steep vegetation and climate gradients at the inception of the last glacial

surface and near surface effects on seismic waves theory and borehole seismometer results a simple plane wave model is adequate to explain many surface versus borehole seismometer data sets using such a model we present a series of examples which demonstrate the effects of the free surface near surface velocity gradients and low impedance surface layers on the amplitudes of upcoming body waves in some cases these amplitudes are predictable from simple free surface and impedance contrast expressions however in other cases these expressions are an unreliable guide to the complete response and the full plane wave calculation must be performed large surface amplifications are possible even without focusing due to lateral heterogeneities or nonlinear effects both surface and borehole seismometer site responses are almost always frequency dependent ocean bottom versus borehole seismic data from the 1983 ngendei seismic experiment in the southwest pacific are consistent with both a simple plane wave model and a more complete synthetic seismogram calculation the borehole seismic response to upcoming p waves is reduced at high frequencies because of interference between the upgoing p wave and downgoing p and sv waves reflected from the sediment basement interface however because of much lower borehole noise levels the borehole seismometer enjoys a p wave signal to noise advantage of 3 to 7 db over nearby ocean bottom instruments

nonlinear soil response in the vicinity of the van normal complex following the 1994 northridge california earthquake ground motion recordings obtained at the van norman complex from the 1994 northridge california mainshock and its aftershocks constitute an excellent data set for the analysis of soil response as a function of ground motion amplitude we searched for nonlinear response by comparing the fourier spectral ratios of two pairs of sites for ground motions of different levels using data from permanent strong motion recorders and from specially deployed portable instruments we also compared the amplitude dependence of the observed ratios with the amplitude de pendence of the theoretical ratios obtained from 1 d linear and 1 d equivalent linear transfer functions using recently published borehole velocity profiles at the sites to provide the low strain material properties one pair of sites was at the jensen filtra tion plant jfp the other pair was the rinaldi receiving station r n and the los angeles dam lad most of the analysis was concentrated on the motions at the jensen sites portable seismometers were installed at the jfp to see if the motions inside the structures housing the strong motion recorders differed from nearby flee field motions we recorded seven small earthquakes and found that the high fre quency low amplitude motions in the administration building were about 0 3 of those outside the building this means that the lack of high frequencies on the strong motion recordings in the administration building relative to the generator building is not due solely to nonlinear soil effects after taking into account the effects of the buildings however analysis of the suite of strong and weak motion recordings indicates that nonlinearity occurred at the jfp as predicted by equivalent linear analysis the largest events the mainshock and the 20 march 1994 aftershock show a significant deamplification of the high frequency motion relative to the weak mo tions from aftershocks occurring many months after the mainshock the weak mo tion aftershocks recorded within 12 hours of the mainshock however show a relative deamplification similar to that in the mainshock the soil behavior may be a con sequence of a pore pressure buildup during large amplitude motion that was not dissipated until sometime later the motions at r n and lad are from free field sites the comparison among spectral ratios of the mainshock weak motion coda waves of the mainshock and an aftershock within ten minutes of the mainshock indicate that some nonlinearity occurred presumably at rin because it is the softer site the spectral ratio for the mainshock is between that calculated for pure linear response and that calculated from the equivalent linear method using commonly used modulus reduction and damping ratio curves in contrast to the jensen sites the ratio of motions soon after the high amplitude portion of the mainshock differs from the ratio of the mainshock motions indicating the mechanical properties of the soil returned to the low strain values as the high amplitude motion ended this may indicate a type of nonlinear soil response different from that affecting motion at the jensen administration building

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

a method to predict the group fissuring and faulting caused by regional groundwater decline ground fissuring is a recurrent problem in many countries where water extraction surpasses the natural recharge of aquifers due to differential settlement the soil layer undergoes deformation and cracks with serious consequences for civil infrastructure here we propose an approximate analysis of the fissuring process that can be used to predict the location of cracks which increasingly affect some middle and large sized cities in the world for that purpose the ground loss theory is applied to sediments overlying a sinusoidal shaped graben this analysis shows the existence of a tensile zone at the border of the graben with maximal values on its shoulder where tension cracks are more likely to appear it also shows that soil deformation under differential settlement may evolve into ground faulting if water withdrawal continues finally when a crack has completely developed the tensile zone shifts towards the center of the graben creating a new area for potential cracking and faulting

origin of ground fissures in the shanxi graben system northern china abstract since the 1950s hundreds of ground fissures have occurred in the shanxi graben system in northern china the fissures and related subsidence and differential settlement have caused and are causing substantial damage to homes agricultural land roads canals and other infrastructure although generally similar in appearance the fissures have different origins 1 some fissures coincide with northeast trending faults trenching shows that the fissures extend into the near surface faults increasing vertical offset clay beds and other stratigraphic markers at depth and therefore are probably the surface expression of fault movements 2 some fissures are demonstrably related to accelerated groundwater withdrawal this is particularly apparent in xi an city where groundwater levels have declined by about 15 m within 4 years 3 other fissures owe their origin to the well known process of soil collapse this is particularly common in the silty loessial sediments that occur within most of the valleys that comprise the shanxi graben system

direct land sea correlations in the last interglacial complex isotopic and pollen analyses of an eastern atlantic core permit the first direct correlation of substages 5e and 5c of the marine climatostratigraphical system with the eemian and st germain i respectively of the classical grande pile pollen sequence north east france the vegetational sequences during the warm intervals of the last interglacial complex 125 000 75 000 yr bp indicate that climatic deterioration occurred late on the mid european continent after the initiation of glaciation over continental masses in high latitudes