new relationships between vs thickness of sediments and resonance frequency calculated by the h v ratio of seismic noise for the cologne area germany noise measurements were carried out in the cologne area germany and the resonance frequency of each site was estimated from the main peak in the spectral ratio between the horizontal and vertical component for 32 of these sites the thickness of the sedimentary cover was known from boreholes and a clear correlation between resonance frequency and sediment thickness was observed a formula that correlates cover thickness with frequency of the main peak in the horizontal to vertical spectral ratio was derived in addition a best fitting shear wave velocity distribution with depth vs z as well as a relationship between average shear wave velocity vs and thickness of the sedimentary cover was calculated by using all of the noise measurements and applying the derived relationships we obtained a subsoil classification for the cologne area

scandinavian caledonide metallogeny in a plate tectonic perspective caledonian metallogeny has endowed scandinavia with abundant metalliferous mineral resources of several genetical and compositional types many of which have been exploited at various scales from the seventeenth century onwards because of this long history of exploration exploitation coupled with excellent exposures the caledonian orogen in scandinavia can be taken as a model to illustrate the relationship between metallogenic evolution and plate tectonics its orogenic and metallogenic development can be related to a period of plate movements which started about 700 600 ma ago with rifting and break up of a proterozoic megacontinent rodinia followed by the opening up of a wide ocean iapetus and ending with collision between the laurentian and baltic continents the climactic scandian phase of orogeny in silurian times fragments of this sedimentary magmatic and tectonic history are recorded in various autochthonous and allochthonous units which were ultimately thrusted eastwards above the baltic plate margin

investigation of site properties in adapazari turkey using microtremors and surface waves determination of suitable areas for new residential buildings is crucial to increase the resilience of buildings against earthquake hazards after the 1999 izmit earthquake mw 7 4 the city of sakarya has been expanding rapidly in terms of both the population and number of superstructures despite the fact that sakarya suffered several large earthquakes in the last two decades the geophysical properties of the region have not been adequately investigated in this study the site properties of sakarya university esentepe campus and its surrounding serdivan district which is one of the important parts of the city are determined using microtremor measurements and surface wave analysis nakamura s spectral ratio method spectral ratio between the horizontal and vertical components h v or hvsr was used to determine the fundamental frequency and site amplification values the shear wave velocity profiles of the studied sites were determined using the multichannel analysis of surface waves method seismic measurements were performed at 34 locations to record the surface waves in the area the fundamental frequency and site amplification values are determined as 1 02 11 68 and 1 33 5 96 hz respectively from the microtremor measurements the fundamental frequency is between 4 0 and 11 5 hz in the campus area and between 1 3 and 2 0 hz near the d 100 intercity highway the site amplification was determined to be 1 2 5 in the campus area the greatest site amplification 6 is obtained at thick alluvium deposits in the valley between hills the average shear wave velocity values are within the range of 300 and 1120 m s some parts located on the hill area have better soil condition b categories according to the national earthquake hazard reduction program and have comparatively high shear wave velocities in the range of 740 1080 m s whereas low velocity values are found at the thick alluvium deposits d we found that the geological properties and topographies play very important roles on the shear wave velocity and the amplification factors in the investigated area

comparison of site classification from vs30 vs10 and hvsr in italy the aim of this work is to verify if 1 the average of shear wave velocity from the surface to 30 m depth vs30 is a good proxy of site amplification in a country with complex geology like italy 2 the grouping of vs30 in different soil classes and relevant spectra in the italian seismic codes is adequate and 3 shallow shear wave profiles vs10 could be a more economical tool for site classification to answer the first two questions we examined 40 estimates of vs30 derived from microzonation projects we performed in italy 27 obtained with downhole measurements plus 13 ve locity profiles obtained with surface techniques in all the sites we installed seismic instrumentation to record earthquakes and to estimate site response using horizontal to vertical spectral ratios hvsr the comparison between hvsr and vs30 showed in about one third of the sites that vs30 is not a good proxy of observed amplification effects if the site does not have a monotonically increasing velocity profile the reason vs30 does not provide satisfactory estimates in italy is linked to peculiar geological settings that are widespread in the country we then compared the observed ampli fications from earthquake hvsr data with the ones provided by the italian seismic code noting a substantial underestimation by the code a somewhat unsettling situa tion because hvsr is usually considered to be a lower bound for amplification es timated with other techniques finally we studied 45 vs downhole profiles to 30 m depth performed also at sites where earthquake recordings are not available on this data set we noticed that vs10 could predict site classification with the same performances of vs30 we consider al ternative soil classification schemes that include soil frequency besides the velocity profile in this two parameter approach vs10 could be substituted for vs30

sea surface temperature in the north tropical atlantic as a trigger for el nino southern oscillation events the el nino southern oscillation in the pacific ocean influences temperature in other tropical ocean basins reanalysis data and model simulations suggest that temperature anomalies in the north tropical atlantic may also influence the development of la nina events

site response shallow shear wave velocity and damage in los gatos california from the 1989 loma prieta earthquake aftershock records of the 1989 loma prieta earthquake are used to calculate site response in the frequency band of 0 5 10 hz at 24 locations in los gatos california on the edge of the santa clara valley two different methods are used spectral ratios relative to a reference site on rock and a source site spectral inversion method these two methods complement each other and give consistent results site amplification factors are compared with surficial geology thickness of alluvium shallow shear wave velocity measurements and ground deformation and structural damage resulting from the loma prieta earthquake higher values of site amplification are seen on quaternary alluvium compared with older miocene and cretaceous units of monterey and franciscan formation however other more detailed correlations with surficial geology are not evident a complex pattern of alluvial sediment thickness caused by crosscutting thrust faults is interpreted as contributing to the variability in site response and the presence of spectral resonance peaks between 2 and 7 hz at some sites within the range of our field measurements there is a correlation between lower average shear wave velocity of the top 30 m and 50 higher values of site amplification an area of residential homes thrown from their foundations correlates with high site response this damage may also have been aggravated by local ground deformation severe damage to commercial buildings in the business district however is attributed to poor masonry construction

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

s wave site response estimates using horizontal to vertical spectral ratios we tested the hypothesis involved in determining the dynamic response of soils using spectral ratios between horizontal and vertical components of ground motion this hypothesis proposes that the vertical component of motion contains mainly the source effect and is approximately insensitive to site amplifications we used the vertical component of strong motion records from earthquakes of the region of friuli italy to evaluate the site response for different geologic conditions s wave source functions of the events used were first retrieved from the acceleration records using a generalized inversion in the frequency domain then an average site response was calculated for each site analyzed the resulting site functions show small vertical amplifications for most of the sites within a factor of 2 this result confirms the validity of the method to estimate s wave site responses however when the s wave arrivals are contaminated by surface waves the vertical amplification may exceed the uncertainty expected by the spectral ratio technique

evaluation of methods for estimating linear site response amplifications in the los angeles region we have evaluated two methods of estimating linear site response amplifications and the standard index for classifying sites by comparing the results of each technique to observed ground motions at 33 sites in the los angeles region using velocity and density profiles from 33 boreholes we evaluated the use of the average 30 m shear wave velocity and associated site classifications the quarter wavelength method and the haskell propagator matrix method we correlated the average 30 m shear wave velocity and nehrp site classification at the borehole sites colocated within 290 m of a site with observed ground motion the observed data follow the expected trend of higher ground motion amplifications for lower average shear wave velocities but there is a significant degree of variability also there is a great deal of scatter in the observed amplifications within each national earthquake hazards reduction program nehrp class we used the velocity and density information in the database to calculate the average frequency dependent site response in the frequency ranges 1 3 hz 3 5 hz and 5 7 hz for a one dimensional flat layered structure using the haskell propagator matrix method and the quarter wavelength method there is a general correlation with the ground motion data however once again there is a great degree of scatter although slightly less for the quarter wavelength method we note that both the observed and predicted amplifications can change dramatically over a distance as small as 1 km or less even though all techniques considered give results that follow the expected trend of higher amplifications for softer sediments the predicted site response at any particular site with the current level of information may not be representative of the shaking that will actually occur during an earthquake the disparity between observed and predicted amplifications appears to be a result of oversimplification inherent in the amplificationestimation methods such as the use of average or assumed values for the site conditions in the absence of measured values the smoothing effect of using an average velocity limiting the properties considered to the uppermost 30 m of material and complexities in the wave propagation that are not addressed by these methods

site amplification effects based on teleseismic wave analysis the case of the pellice valley piedmont italy the investigation of local amplification phenomena by seismic signal analysis is a fundamental step in carefully defining the seismic response of an area in this study we investigate the use of teleseismic recordings in assessing seismic wave amplification in the pellice valley northwestern alps italy assuming that teleseismic p waves are sensitive to the deep structure of a basin we deal with the computation of horizontal to vertical spectral ratios hvsrs and with the estimate of teleseismic p wave arrival time delays and p wave amplifications with respect to a reference site the reliability of the hvsr results obtained by considering teleseismic signals is confirmed by the agreement with the results coming from both the hvsr of noise and hvsr of s wave of local events methods strong correlation between the p wave arrival time delays and the relative p wave amplifications with respect to thickness of the low velocity layers and the geometry of the bedrock is found

northeast china summer temperature and north atlantic sst a previous study revealed a close relationship between interannual variations ofnortheast china nec summer temperature and a tripole sea surface temperature sst anomaly pattern in the north atlantic in preceding spring the present study investigatesthe change in the above relationship and the plausible causes for the change a tripole sstindex is defined with its positive value corresponding to positive sst anomalies in thetropics and midlatitudes and negative sst anomalies in the subtropics the tripole sstanomaly pattern has a weak correlation with nec summer temperature during the 1950sthrough the mid 1970s in sharp contrast to the 1980s and 1990s this change is related tothe difference in the persistence of the tripole sst pattern before the late 1970s thetripole sst pattern weakened from spring to summer and thus the spring north atlantictripole sst pattern had a weak connection with nec summer temperature on thecontrary after the late 1970s the tripole sst pattern displayed a tendency of persistencefrom spring to summer contributing to circulation changes that affected nec summertemperature there are two factors for the persistence of the tripole sst pattern fromspring to summer one is the north atlantic air sea interaction and the other is thepersistence of sst anomalies in the eastern equatorial pacific during the decay ofel nino southern oscillation enso it is shown that the north atlantic sst anomaliescan have an impact on nec summer temperature independent of enso

interannual and interdecadal variations of the east asian summer monsoon and tropical pacific ssts part i roles of the subtropical ridge the interannual relationship between the east asian summer monsoon and the tropical pacific ssts is studied using rainfall data in the yangtze river valley and the ncep reanalysis for 1951 96 the datasets are also partitioned into two periods 1951 77 and 1978 96 to study the interdecadal variations of this relationship a wet summer monsoon is preceded by a warm equatorial eastern pacific in the previous winter and followed by a cold equatorial eastern pacific in the following fall this relationship involves primarily the rainfall during the pre mei yu mei yu season may june but not the post mei yu season july august in a wet monsoon year the western north pacific subtropical ridge is stronger as a result of positive feedback that involves the anomalous hadley and walker circulations an atmospheric rossby wave response to the western pacific complementary cooling and the evaporation wind feedback this ridge extends farther to the west from the previous winter to the following fall resulting in an 850 hpa anomalous anticyclone near the southeast coast of china this anticyclone 1 blocks the pre mei yu and mei yu fronts from moving southward thereby extending the time that the fronts produce stationary rainfall 2 enhances the pressure gradient to its northwest resulting in a more intense front and 3 induces anomalous warming of the south china sea surface through increased downwelling which leads to a higher moisture supply to the rain area a positive feedback from the strong monsoon rainfall also appears to occur leading to an intensified anomalous anticyclone near the monsoon region this sst subtropical ridge monsoon rainfall relationship is observed in both the interannual timescale within each interdecadal period and in the interdecadal scale the sst anomalies sstas change sign in northern spring and resemble a tropospheric biennial oscillation tbo pattern during the first interdecadal period 1951 77 in the second interdecadal period 1978 96 the sign change occurs in northern fall and the tbo pattern in the equatorial eastern pacific sst is replaced by longer timescales this interdecadal variation of the monsoon sst relationship results from the interdecadal change of the background state of the coupled ocean atmosphere system this difference gives rise to the different degrees of importance of the feedback from the anomalous circulations near the monsoon region to the equatorial eastern pacific in a wet monsoon year the anomalous easterly winds south of the monsoon enhanced anomalous anticyclone start to propagate slowly eastward toward the eastern pacific in may and june apparently as a result of an atmosphere ocean coupled wave motion these anomalous easterlies carry with them a cooling effect on the ocean surface in 1951 77 this effect is insignificant as the equatorial eastern pacific sstas already change from warm to cold in northern spring probably as a result of negative feedback processes discussed in enso mechanisms in 1978 96 the equatorial eastern pacific has a warmer mean sst a stronger positive feedback between ssta and the walker circulation during a warm phase tends to keep the ssta warm until northern fall when the eastward propagating anomalous easterly winds reach the eastern pacific and reverse the ssta

site classification for earthquake hazard and risk assessment in australia while site response phenomena are well recognized globally the influence of regolith properties on ground motion has not previously been investigated for much of australia in an effort to characterize the regolith in terms of its ability to modify earthquake ground shaking this validation study assesses the national site classification map of australia which has been developed for application in first order earthquake hazard and risk assessment in the absence of regolith thickness and fundamental period data site classes are assigned based on a method developed in california that uses the relationship between geological material and the shear wave velocity of the upper 30 m v s 30 the classification scheme is then adjusted to suit the australian geological environment including a correction for the presence of weathered in situ regolith commonly encountered in this stable tectonic setting the results are validated using geophysical and geotechnical data from a variety of quaternary sedimentary environments in the newcastle sydney and perth urban areas and from bedrock dominated environments at a range of sites across australia the results of these analyses demonstrate the utility but also highlight the limitations of applying a depth limited shear wave velocity method in site classification for seismic hazard assessment

noninvasive techniques for site characterization of alberta seismic stations based on shear wave velocitynoninvasive techniques for site characterization of alberta seismic stations based on shear wave velocity

analysis and modeling of hvsr in the presence of a velocity inversion the case of venosa italy the aim of this work is to check the stability of the horizontal to vertical spectral ratios hvsrs calculated at the venosa station site italy this site lies over a layer of anthropogenic fill 4 m thick a rigid layer of conglomerates 15 m thick and a thick layer of clays about 300 m thick above the seismic bedrock the velocity inversion which takes place at the conglomerates clays interface is of main importance for the amplification behavior of this site we have analyzed nearly 2 years of data composed of 244 triggered noise records and 44 earthquakes the results obtained by the two data sets show different site response characteristics in particular the earthquake hvsr is not deamplified in the frequency range 1 8 hz like the triggered noise hvsr to find out the origin of this difference we modeled both the triggered noise and the earthquakes taking advantage of an improved ver sion of the thompson haskell propagation matrix method the differences between triggered noise and earthquake amplification functions might be explained by the difference in composition and propagation of the seismic wave fields moreover we show that the nonlinear behavior of the anthropogenic fill might explain the presence of the misfit of the resonance frequency attributed to this layer between triggered noise and earthquakes

faster better shear wave velocity to 100 meters depth from refraction microtremor arrays current techniques of estimating shallow shear velocities for assessment of earthquake site response are too costly for use at most construction sites they require large sources to be effective in noisy urban settings or specialized independent recorders laid out in an extensive array this work shows that microtremor noise recordings made on 200 m long lines of seismic refraction equipment can estimate shear velocity with 20 accuracy often to 100 m depths the combination of commonly available equipment simple recording with no source a wavefield transformation data processing technique and an interactive rayleigh wave dispersion modeling tool exploits the most effective aspects of the microtremor spectral analysis of surface wave sasw and multichannel analysis of surface wave masw techniques the slowness frequency wavefield transformation is particularly effective in allowing accurate picking of rayleigh wave phase velocity dispersion curves despite the presence of waves propagating across the linear array at high apparent velocities higher mode rayleigh waves body waves air waves and incoherent noise two locations illustrate the application of this technique in detail coincident with a large accelerometer microtremor array in reno nevada and atop a borehole logged for shear velocity in newhall california refraction equipment could duplicate microtremor results above 3 hz but could not estimate velocities deeper than 100 m refraction microtremor cannot duplicate the detail in the velocity profile yielded by a suspension logger but can match the average velocity of 10 to 20 m depth intervals and suggest structure below the 100 m logged depth of the hole eight additional examples from southern california and new zealand demonstrate that the refraction microtremor technique quickly produces good results from a wide range of hard and soft sites

uncertainty of linear earthquake site amplification via bayesian inversion of surface seismic data abstractwe examine uncertainty in predicted linear 1d site amplification due to uncertainty in shear wave velocity vs structure quantified from bayesian probabilistic inversion of microtremor array dispersion data based on a sample of vs profiles drawn from the posterior probability density of the microtremor inversion probability distributions are computed for common predictors of site amplification including vsz traveltime average vs to a depth z and amplification spectra based on seismic impedance variations and full transverse shear wave effects these methods are applicable for any site but the resulting probabilistic site amplification analyses are specific to the two sediment sites studied here with strongly contrasting geology in high population centers of british columbia canada the site amplification probability distributions for the two sites are shown to be more informative than amplification estimated for a single best fit vs profile by characterizing the uncertainty and therefore

on the association between spring arctic sea ice concentration and chinese summer rainfall 1 a statistical relationship between spring arctic sea ice concentration sic and chinese summer rainfall is identified using singular value decomposition svd results show that decreased increased spring sic in the arctic ocean and the greenland sea corresponds to increased decreased summer rainfall in northeast china and central china between the yangtze river and the yellow river 28 36 n and decreased increased rainfall in south china corresponding summer 500 hpa height anomalies show a eurasian wave train structure which originates in northern europe and extends southeastwards to northeast china and a south north dipole structure over east asia south to lake baikal such a spatial distribution of 500 hpa height anomalies and corresponding summer rainfall anomalies cannot be entirely attributed to the impact of east asian summer monsoon easm variability the spring arctic sic provides a complementary precursor for chinese summer rainfall variability the combined impacts of both spring arctic sic and eurasian snow cover on the eurasian wave train may explain their statistical linkage

an empirical site classification method for strong motion stations in japan using h v response spectral ratio having a reliable site classification scheme is vital for the development of robust strong motion attenuation models we discuss a promising empirical site classification scheme based on strong motion data from japan we assigned site classes according to the site classification defined in engineering design codes in japan for those k net sites where boreholes reached either to rock or to stiff soils with shear wave velocity of 600 m sec or larger using four site classes defined by dominant site period the average response spectral ratios of the horizontal and vertical components h v of earthquake records for all site classes were found not to be strongly affected by japan meteorological agency jma magnitude hypocentral distance and focal depth for all site classes we used h v ratios for records from the classified k net sites to establish a site classification index using the mean spectral ratios over a wide range of spectral period using the index we were able to classify both k net stations with soil layers thicker than 20 m and other strong motion stations in japan the peak period of the h v spectral ratio can also be used to identify soft soil sites the site amplification factors calculated from the site class terms based on the new site classification are consistent with the period bands defined for these site classes

inversion of surface wave data for subsurface shear wave velocity profiles characterized by a thick buried low velocity layer the study formed part of the simit project integrated italy malta cross border system of civil protection b1 2 19 11 part financed by the european union under the italiamalta cross border cooperation programme 2007 2013

comparison of empirical and numerical site responses at the tito test site southern italy the town of potenza southern italy is one of the test sites for preparing ground motion scenarios within the framework of the italian dipartimento protezione civile instituto nazionale di geofisica e vulcanologia dpc ingv 2004 2006 pro jects an area in the neighboring village of tito was selected to evaluate different techniques for estimating site effects involving a 40 m deep instrumented borehole this two sensor vertical array records teleseismic regional and local seismicity close to the borehole three seismological microarrays utilizing short period sen sors and digitizers with a high dynamic range were installed in may 2005 to record seismic noise differing acquisition geometries allowed the checking of any depen dency in the derived dispersion curves based on the adopted analysis method ex tended spatial autocorrelation esac and frequency wave number f k in gen eral the esac method appears to provide more reliable results in the low frequency range furthermore the soil velocity profiles obtained from the microarray data were compared with the s wave velocity profile derived from down hole measurements a good agreement was observed in the depth range well constrained by the data finally empirical site responses were compared with those calculated numerically from the s wave velocity profiles obtained from the microarray data although this comparison did not resolve a preference among the derived models it showed the importance of downgoing waves in modifying the site response at the tito site

site response attenuation and source spectra of s waves along the guerrero mexico subduction zone acceleration spectra from nine earthquakes and up to 11 stations per earthquake are inverted to find the source spectra the site response and the quality factor q of s waves this method is applied to moderate earthquakes 4 0 0 8 hz does not follow a simple linear relation as observed in previous studies of attenuation in other regions when the source spectra are interpreted in terms of brune s model the stress drops obtained are less than 20 bars for the four larger events analyzed the site functions obtained indicate that although all the stations used are on rock the effect of the near surface geology caused important amplifications at some stations

on the role of stiff soil deposits on seismic ground shaking in western liguria italy evidences from past earthquakes and site response abstract in this work we analyze the macroseismic fields of the main historical earthquakes occurred in western liguria northwestern italy in order to identify possible relations between the isoseismal patterns and the local geological setting anomalies in the spatial distribution of macroseismic intensities are often attributed to site effects we observed that in the region of study such anomalies are mainly located in areas characterized by outcropping pliocene soil deposits mainly made up of stiff silty and marly clays to investigate the influence of such deposits on ground response both horizontal to vertical spectral ratio measurements and numerical site response analyses were carried out for all sites analyzed the spectral ratio curves show marked amplification peaks between 2 and 5 hz following such empirical evidence equivalent linear ground response analyses were performed in order to examine the relation between the measured resonance frequencies and the response of a set of soil columns presenting pliocene marly clayey deposits at their top to this end a database of geotechnical and geophysical properties including 50 reference soil profiles was compiled this database was used to define alternative numerical models considering three different ranges of thickness of the pliocene marly clayey deposits between 5 and 35 m 30 and 65 m 60 and 105 m results show marked amplification effects in the ranges 1 3 hz 2 5 hz and 3 10 hz depending on the thickness of the investigated soil deposits these frequency ranges are in agreement with those observed from the experimental measurements which are therefore proved adequately representative of the resonance frequencies of the pliocene marly clayey deposits therefore based on our findings such deposits can be considered an essential factor in producing the anomalies observed in the isoseismal patterns of the macroseismic fields of the historical earthquakes occurred in western liguria

local site response in an alpine valley from recorded earthquakes and ambient noise analysis local response is estimated within the sediment fill of the tagliamento river valley thv northeastern italy using about 90 weak to medium local and regional earthquakes ground motion is recorded at six stations deployed in a linear array across the valley site amplification factors are determined using the standard spectral ratio the generalized inversion technique and evaluations of receiver functions results obtained from earthquake data are then compared with ambient noise analysis azimuthal effects in the seismic response are observed locally for waves coming from the east southeast aligned with the longitudinal axis of the valley the seismic responses evaluated at the mid valley and at the valley edge are then convolved with the 1976 m w 6 4 friuli mainshock recorded at accelerometric station tlm1 located close to the array the local response at the valley edge in the town of cavazzo carnico is responsible for an enhancement of the input motion of an average factor of about 4 in the frequency range from 2 to 8 hz the elastic demand from the current national regulation for a 475 year return period and specific for cavazzo carnico is overcome by the 5 damped pseudoacceleration response spectrum estimated at the valley edge the underestimation of the italian code is mostly due to a 2d amplification effect at the valley edge rather than a simple inadequacy of the v s 30 site classification online material figures showing locations of historical earthquakes distribution of fundamental frequency of vibration waveforms of the m d 5 1 kobarid earthquake s wave velocity versus depth and git and rf amplification median values and spectra tables of seismic station locations and soil type and of local and regional earthquakes

amplification factors for spectral acceleration in tectonically active regions empirical relationships are developed to predict amplification factors for 5 damped response spectral acceleration period range t 0 01 5 sec as a function of site category we evaluate amplification factors by normalizing response spectral accelerations computed from recordings by reference spectral accelerations derived from a modified attenuation relationship for active regions strong motion sites are categorized according to several schemes which are based on surface geology age only age depositional environment and age material texture shallow 30 m shear wave velocity and geotechnical data criteria for selection of the optimal classification scheme are that the amplification models for categories within the scheme 1 minimize the global dispersion of prediction residuals and 2 are significantly distinct across a broad period range the results of the regressions indicate that the greatest levels of distinction in amplification levels across categories occur for the shallow shear wave velocity scheme but that the dispersion of residuals for this scheme are relatively high for soil sites although not for rock sites conversely schemes based on detailed surface geology generally have the smallest dispersion for soil sites but amplification levels across quaternary categories are only significantly distinct at small periods these findings suggest that detailed surface geology provides an effective means of soil site categorization at small periods whereas shallow shear wave velocity provides an effective means for rock site categorization at small periods at longer periods none of the schemes are optimized relative to both the dispersion and distinction criteria the principal application of the amplification factors is as a modifier of attenuation relations much like a site term the present results significantly reduce the bias associated with the site terms in a widely used attenuation relationship for rock and soft soil site conditions manuscript received 25 february 2002

microtremor measurements used to map thickness of soft sediments the observations about the behavior of microtremor spectra presented here show that noise measurements can be used as a powerful tool to determine the thickness of soft cover layers the most suitable method for this determination is nakamura s technique which is the ratio of the horizontal component noise spectrum and that of the vertical component i i v spectrum the frequency of the main peak in these spectral ratios correlates well with the sediment thickness at the site using an extensive database of microtremor measurements carried out in the western lower rhine embayment germany it was possible to show that this correlation is clearly valid for a wide range of thickness namely from tens of meters to more than 1000 m a simple formula was derived that for the sediments to be found in the area investigated directly calculates the cover thickness from the frequency of the main peak in the h v spectrum a comparison with calculated resonant frequencies sug gests the relation derived from the noise measurements depending on the velocity depth function of the shear wave classical spectral ratios are shown to be strongly influenced by the noise level and are therefore less reliable in determining the res onant frequency of the subsoil the practical relevance of the investigation is illus trated by means of cross sections constructed from results of the microtremor anal yses which provide a convincing image of the surficial structure of the areas investigated

early summer southern china rainfall variability and its oceanic drivers rainfall in southern china reaches its annual peak in early summer may june with strong interannual variability using a combination of observational analysis and numerical modeling the present study investigates the leading modes of this variability and its dynamic drivers a zonal dipole pattern termed the southern china dipole scd is found to be the dominant feature in early summer during 1979 2014 and is closely related to a low level anomalous anticyclone over the philippine sea psac and a eurasian wave train pattern over the mid high latitudes linear regressions based on observations and numerical experiments using the cam5 model suggest that the associated atmospheric circulation anomalies in early summer are linked to decaying el nino southern oscillation like sea surface temperature sst anomalies in the tropical pacific basin scale sst anomalies in the tropical indian ocean and meridional tripole like sst anomalies in the north atlantic in the previous winter to early summer the tropical pacific and indian ocean sst anomalies primarily exert an impact on the scd through changing the polarity of the psac while the north atlantic tripole like sst anomalies mainly exert a downstream impact on the scd by inducing a eurasian wave train pattern the north atlantic tripole like sst anomalies also make a relatively weak contribution to the variations of the psac and scd through a subtropical teleconnection modeling results indicate that the three basin combined forcing has a greater impact on the scd and associated circulation anomalies than the individual influence from any single oceanic basin

can seismic waves be trapped inside an inactive fault zone the case study of nocera umbra central italy in march 1998 a small aperture 350 m linear array of five broadband stations was installed across a pliocene strike slip fault crossing the town of nocera umbra central italy three component seismograms of local earthquakes recorded during the umbria marche seismic sequence have shown that the degradation of mechanical properties in damaged rock causes a significant amplification of ground motion within the fault zone marra et al 2000 during the operation of the array an m w 5 3 subcrustal earthquake occurred at a depth of 48 km and an epicentral distance of 10 km from nocera umbra the near vertical incidence of this event offers a unique opportunity for constraining the 2d geometry of the laterally heterogeneous low velocity structure responsible for the large amplification across the fault based on the observed symmetry of the amplification pattern a 2d wedge shaped model of the fault zone is used for the computation of antiplane sh synthetic waveforms to be compared with observations along the array two parameters of the wedge model can be constrained by independent geophysical and geological data 1 shear wave velocity in pristine rock outside the fault zone v s 2200 m sec and 2 the lateral extent of the damaged rock zone l 160 m the other two model parameters namely the wedge depth h and shear wave velocity of the fault zone v f s are varied computer simulations show that trapped waves which have been observed so far for earthquakes occurring inside the fault zone can develop inside a 2d wedge model when struck by external vertically incident seismic radiation results of numerical modeling indicate that in spite of its extreme simplicity such an idealized model is successful in reproducing many of the essential characters of ground motion within the fault zone of nocera umbra even though the best fit solution is not unique and the model parameters trade off each other a study of parameter sensitivity comparing synthetics with recorded data indicates that the variability of h and v f s can be restricted to a limited range of values the quality of fit is optimal when the shear velocity reduction lies in the range of 40 50 and the depth of the trapping zone is comprised between 1 and 2 km

impact of the indian ocean sst basin mode on the asian summer monsoon 1 following an el nino event a basin wide warming takes place over the tropical indian ocean peaks in late boreal winter and early spring and persists through boreal summer our observational analysis suggests that this indian ocean warming induces robust climatic anomalies in the summer indo west pacific region prolonging the el nino s influence after tropical east pacific sea surface temperature has returned to normal in response to the indian ocean warming precipitation increases over most of the basin forcing a matsuno gill pattern in the upper troposphere with a strengthened south asian high near the ground the southwest monsoon intensifies over the arabian sea and weakens over the south china and philippine seas an anomalous anticyclonic circulation forms over the subtropical northwest pacific collocated with negative precipitation anomalies all these anomaly patterns are reproduced in a coupled model simulation initialized with a warming in the tropical indian ocean mixed layer indicating that the indian ocean warming is not just a passive response to el nino but important for summer climate variability in the indo west pacific region the implications for seasonal prediction are discussed