upper bound solution for seismic bearing capacity of shallow foundations near slopes an upper bound technique of limit analysis is used to determine the bearing capacity of a shallow strip foundation near a slope the approach used is pseudo static and the seismic forces consist of a horizontal load applied to the foundation and the inertia of the soil mass the failure mechanism is composed of an active wedge a passive wedge and a shear transition zone between the two wedges the results are compared with those of other investigators

seismic bearing capacity of foundations on cohesionless slopes by applying the lower bound theorem of limit analysis in conjunction with finite elements and nonlinear optimization the bearing capacity factor n has been computed for a rough strip footing by incorporating pseudostatic horizontal seismic body forces as compared with different existing approaches the present analysis is more rigorous because it does not require an assumption of either the failure mechanism or the variation of the ratio of the shear to the normal stress along the footing soil interface the magnitude of n decreases considerably with an increase in the horizontal seismic acceleration coefficient kh with an increase in kh a continuous spread in the extent of the plastic zone toward the direction of the horizontal seismic body force is noted the results obtained from this paper have been found to compare well with the solutions reported in the literature c 2013 american society of civil engineers

mass balance of two high arctic plateau ice caps mass balance measurements have been renewed on two small ice caps on north eastern ellesmere island original stake networks were established in 1972 and 1976 since then both ice caps have experienced significant mass losses averaging 70 to 140 kg m2 a i they have also decreased in area the equilibrium line in this area has averaged around 1150 m for the last decade or so the ice caps are remnants of former climatic conditions and are out of equilibrium with contemporary climate

geomorphological evidence of holocene climatic change from northwest ellesmere island canadian high arctic proxy data from the northern coast of ellesmere island are used to reconstruct holocene palaeoclimate and appear to corroborate the ice core record from the canadian and greenland high arctic despite some regional variation geomorphological evidence indicates that deglaciation was associated with a marked climatic amelioration in the late pleistocene early holocene 10 ka bp this contrasts with glaciers on the south side of grant land mountains which started to retreat at 7 5 ka bp perhaps due to significant differences in glacioclimatic regime and the influence of the arctic ocean indicators of sea ice conditions on northern ellesmere island suggest that the early holocene was a period of considerable open water radiocarbon dates on driftwood collected from behind the north coast ice shelves suggest that the ice shelves formed during a mid holocene climatic deterioration geomorphic evidence shows that the ice shelves are presently breaking up and melting in response to recent warming glaciers hav

effect of wind scouring on climatic records from ice core oxygen isotope profiles removal of winter snow by wind explains why the annual mean oxygen isotope ratio at an ice divide is 2 5 less negative than it is 1 2 km downslope cores from two sites on an ice cap ellesmere island canada show past variations in the difference depending on where the ice originated relative to the scoured zone some ice core climatic records may need correction for scouring

attenuation of coda waves in new england abstract seismic wave attenuation was measured in new england from the time domain decay of coda wave amplitudes on narrow bandpass filtered seismograms of local earthquakes the frequency band of interest was 0 75 to 10 hz q c f was found to increase with frequency across this band but there was also a difference between the q c f values for short t t 100 sec lapse times of coda wave propagation for the short lapse time data corresponding to wave paths primarily in the upper crust q c f increases from 400 at 3 hz to 1300 at 10 hz for the large lapse time data corresponding to wave paths in the lower crust and upper mantle q c f was found to vary from 660 at 1 hz to 1500 at 10 hz if we interpret this dataset in terms of a model incorporating both scattering and anelastic attenuation we find that the mean free path of seismic waves over this frequency band is 80 km for short lapse times and 400 km for long lapse times if we assume that scattering is entirely responsible for the observed attenuation we find that the minimum mean free path for short lapse times is about 75 km over all frequencies whereas for long lapse times the minimum mean free path decreases from 400 km at 0 75 hz to 90 km at 10 hz

displacement based seismic design of a shallow strip footing positioned near the edge of a rock slope abstract this paper presents a displacement based dynamic design of shallow strip footings located close to the edge of homogeneous and isotropic rock slopes the analysis is conducted using the generalized tangential technique in which the hoek brown strength is replaced by an optimal tangential mohr coulomb domain within the framework of the kinematic approach of limit analysis theory in order to better understand the influence of these factors including geometrical features rock strength parameters and seismic loading a parametric study is carried out an expression is derived and used to obtain a least upper bound solution for the bearing capacity of a footing on a rock slope considering a kinematically admissible log spiral failure mechanism in addition a similar expression of the horizontal yield seismic coefficient is derived for a given load acting on the foundation the assessment of earthquake induced permanent displacement is performed by a simplified procedure this requires the knowledge of a ground motion parameter that can be evaluated by site specific seismic hazard analyses or ground motion prediction equations and that considers the actual sliding surface the calculated displacement should not be greater than a selected limiting tolerable displacement for the specific case an example is presented illustrating the application of the design procedure for the bridge foundations

topoclimatic studies of a high arctic plateau ice cap meteorological observations on and around a small exposed plateau ice cap on north eastern ellesmere island n w t canada were carried out in the northern summers of 1982 and 1983 the objective was to assess the effect of the ice cap on local climate as the melt season progressed in 1982 seasonal net radiation totals were lowest on the ice cap and greatest at the site farthest from the ice cap the ice cap site received only 35 of net radiation totals on the surrounding tundra this reflects a gradient in albedo albedo changed most markedly away from the ice cap as the summer progressed a thermal gradient was observed along a transect perpendicular to the ice cap edge this gradient was greatest at low levels i5 cm and was maximized under cloud free conditions the cooling effect of the ice cap was less at the start of the ablation season than later low level inversions occurred more frequently over the ice cap than over the snow free tundra overall melting degree days on the ice cap were only 40 i5 of those on the adjacent tundra a model of interactions between the atmosphere and a snow and ice cover or a snow free tundra felsenmeer surface is proposed observations indicate that the ice cap has a cooling effect on the lower atmosphere relative to the adjacent snow free tundra this effect is absent when snow cover is extensive as in 1983

mass balance of white glacier axel heiberg island n w t canada 1960 91 white glacier is a valley glacier at 79 5 n with an area of 38 7 km 2 its mass balance has been measured over 32 years with a 3 year gap by standard techniques using the stratigraphic system with a stake density of the order of one stake per km 2 errors in stake mass balance are about 200 250 mm due largely to the local unrepresentativeness of measurements errors in the whole glacier mass balance b are of the same order as single slake errors however the lag 1 autocorrelation in the time series of b is effectively zero so it consists of independent random samples and the error in the long term balance normal b is noticeably less b is 100 48 mm the equilibrium line altitude ela averages 970 m with a range of 470 1400 m mass balance is well correlated with ela but detailed modelling shows that the equilibrium line is undetectable on visible band satellite images a reduced network of a few stakes could give acceptable but less accurate estimates of the mass balance as could estimates based on data from a weather station 120 km away there is no evidence of a trend in the mass balance of white glacier to detect a climatologically plausible trend will require a ten fold reduction of measurement error a conclusion which may well apply to most estimates of mass balance based on similar stake densities

attenuation seismic moments and site effects for weak motion events application to the pyrenees we derive attenuation models site response functions and source parameters from small magnitude events recorded at a regional scale our data set consists of 45 pyrenean events with magnitude 2 7 to 5 4 recorded at distances from 15 to 200 km for which about 600 displacement spectra could be computed we assume that the far field displacement spectrum is the product of source propagation and site effects s wave displacement spectra are computed for accelerometric and velocimetric records using fast fourier transforms by integration in the frequency domain for 0 5 15 hz owing to the velocimeter response the spectra may be unreliable below 1 hz a brune type source is assumed attenuation is decomposed into a frequency dependent term anelastic attenuation and a non frequency dependent term geometric attenuation adapting a process proposed by scherbaum and wyss 1990 we invert the data with a two step regression the first step recovers the geometric attenuation the seismic moment and a frequency independent scaling factor the second step gives the corner frequency the anelastic attenuation and a frequency dependent site effect our results show that the propagation term includes a slightly superspheric geometric attenuation that varies as 1 r 1 2 and an anelastic attenuation that cannot be safely resolved with a linear approach computed moment magnitudes are generally 0 5 to 1 unit smaller than local magnitudes corner frequencies decrease linearly with magnitude and the stress drops obtained appear to be nearly constant whatever the magnitude finally robust site responses are computed that are compatible with those derived with other methods

frequency dependence and spatial distribution of seismic attenuation in france experimental results and possible interpretations campillo m and plantet j l 1991 frequency dependence and spatial distribution of seismic attenuation in france experimental results and possible interpretations phys earth planet inter 67 48 64 we processed digital records from 431 earthquakes at 25 stations of the laboratoire de detection geophysique network in france we computed spectral amplitudes of pg and lg in different group velocity windows this large data set aliowed us to compute a map of mean crustal attenuation through simultaneous consideration of source amplitude site response and apparent q our inversion procedure combines an iterative reconstruction technique with an adjustment of source amplitudes and site responses at each step the stability of the result is tested with different subsets of data and the resolution is evaluated maps of apparent attenuation at frequencies between 1 5 and 10 hz were computed from pg lg and early coda of lg these results are in a good agreement with the predictions of the singie scattering model both for frequency dependence and for qs qp ratios the comparison between the attenuation anomaly found in the yariscan belt and results from a deep reflection seismic profile confirms the prominent part played by scattering in the apparent attenuation of seismic waves in the crust

mw estimation from crustal coda waves recorded on analog seismograms abstract accurate magnitude determinations are important issues when producing seismicity catalogs aimed at assessing seismic hazard especially in moderate seismicity regions when only a few seismic stations are available the stability of coda wave amplitudes presents great advantages as compared to s lg wave amplitudes for estimating magnitude we develop a method for processing coda waves to determine the moment magnitude m w that is valid both for recent digital short period records and old analog short period seismograms because spectral analyses of paper records are most often not possible we fit the coda envelopes of the raw time signal our empirical representation of the coda envelope is tested with synthetics and its parameters are determined using 109 earthquakes digitally recorded at 12 stations of the laboratoire de detection et de geophysique ldg french velocimetric network between 1997 and 2013 the coda parameters are adapted to the four broad geological zones that can be defined in france within each zone this model matches the observed coda wave envelope for m w between 3 4 and 5 3 synthetic coda signals computed from the regional quality factors q c f within the 0 3 7 hz frequency band of the instrument show that the frequency and regional variation of q c are enough to explain the coda shape of the raw signal this empirical coda model is only valid for events with corner frequency larger than the 1 hz cutoff frequency of the ldg instrument when applying this raw signal envelope model to actual data the site effect at each station must be accounted for from this empirical coda model we obtain stable corrected coda amplitudes that can be directly converted into m w by linear regression

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

ultimate seismic bearing capacities and failure mechanisms for strip footings placed adjacent to slopes assessment of the ultimate bearing capacity of foundations adjacent to slopes is complex as it is highly dependent on the slope geometry and soil properties seismic loading may impact both the cri

seismic bearing capacity factors for spread foundations the effect of horizontal earthquake body forces on the bearing capacity of foundations has been examined computationally in a rigorous manner by employing the method of stress characteristics the bearing capacity factors n c n q and n y due to the components of soil cohesion ground surcharge pressure and soil unit weight respectively have been plotted as a function of earthquake acceleration coefficient a h for different values of soil friction angle phi the inclusion of earthquake body forces causes a considerable reduction in the bearing capacity factors the bearing capacity factors n c and n q are seen to be approximately of the same magnitude as those reported in the literature on the basis of different solution methods however the obtained values of n y are found to be significantly smaller than the available results the nature of the pressure distribution along the footing base and the geometry of the observed failure patterns vary with the consideration of earthquake body forces

seismic bearing capacity of foundations on slopes the effect of pseudo static horizontal earthquake body forces on the bearing capacity of foundations on sloping ground has been assessed using the method of stress characteristics two failure mechanisms were considered based on the extension of the characteristics from the ground surface towards the footing base from either one side or both sides the magnitude of n gamma based on the both sides failure mechanism for smaller values of earthquake acceleration coefficient alpha h has been found to be significantly smaller than that obtained using the single side mechanism however in the presence of alpha h the both sides mechanism becomes kinematically inadmissible in many cases for higher values of phi only the single side mechanism was found statically admissible for computing the bearing capacity factors n c and n q on sloping ground all the bearing capacity factors reduce considerably with increase in ah for various ground inclinations

spatial variations of seismic attenuation and heterogeneity in the pyrenees coda q and peak delay time analysis abstract lateral variations of seismic attenuation in the pyrenees are explored from the analysis of local earthquake records scattering loss and intrinsic absorption both control the propagation of short period s waves through the crust the role of intrinsic and scattering attenuation is analyzed in two steps firstly the coda quality factor q c which quantifies the energy decay of coda waves is estimated at large lapse time in five frequency bands and interpreted as intrinsic absorption next we systematically measure the peak delay time defined as the time lag from the direct s wave onset to the maximum amplitude arrival this parameter quantifies the strength of multiple forward scattering due to random inhomogeneities along the seismic ray path comparison of coda q and peak delay time measurements allows a qualitative interpretation of the origin of seismic attenuation scattering absorption in the pyrenean crust at low frequency coda q variations mainly depend on the tectonic units of the pyrenees with stronger absorption in sedimentary basins and smaller absorption in paleozoic basements at high frequency coda q is low at the location of neogene structures in the eastern pyrenees a more enigmatic low q c anomaly is also observed at the location of the maladeta massif in the central pyrenees in all frequency bands peak delay time measurements systematically show stronger scattering in the western pyrenees in the labourd mauleon area absorption and scattering are both important at low frequency the western pyrenees also correspond to a high velocity density anomaly revealed from tomography and gravity data analysis this suggests that the high level of inhomogeneities and absorption may be related to intrusion of mantle and or lower crustal materials in the eastern pyrenees absorption appears dominant over scattering at high frequency we hypothesize that the strong absorption observed in this area may be related to volcanic structures

seismic bearing capacity of soils this paper derives the seismic bearing capacity factors for a c phi soil within the framework of the mohr coulomb theory horizontal and vertical accelerations and the effects of a inertia forces of the soil both below and above the footing and b the applied loads are all taken into consideration the method is used to derive the ultimate seismic bearing capacity for a square footing 2 5m wide founded 1 0m below a homogeneous soil with c soil cohesion parameter 7 kpa phi 25 degrees and a unit weight of 18 kn per cubic metre the results indicate that the horizontal accelerations as well as soil cohesion and vertical accelerations affect the bearing capacity coefficients considerably

source spectra and site response estimates using the coda of lg waves in western europe source spectra are investigated by using regional events recorded by the ldg french short period seismic network empirical relations describing the lg coda envelope allow us to separate source site and propagation effects 28 events recorded by 14 stations of the ldg network are selected for this study source spectra and site response are determined in the frequency band of 1 16 hz a lg coda magnitude can be defined from these source spectra magnitudes obtained by this technique are strongly correlated to local magnitudes given by the ldg bulletin but the standard deviation is reduced by a factor 3 other parameters such as siteresponse corner frequency and coda q are determined very accurately