reservoir assessment using non invasive geophysical techniques this paper describes the use of three geophysical techniques to detect potential seepage that could jeopardise the integrity of reservoir embankments could induce partial or total collapse and pose a risk to the population nearby a fast scanning geophysical technique using two dipole electromagnetic em profile apparatus gem2 provided the first step to detect the weakest points on the selected dams in order to proceed to a more detailed analysis and visualisation of the soil erosion fissuring or piping using electrical resistivity tomography ert finally self potential surveys were carried out to relate to the em and ert anomalies that could be pathways for seepage and changes of the water displacement inside the embankment the three geophysical techniques used were evaluated in one case study of reservoir in a location relevant to flooding issues in czech republic a risk approach based on the geophysical results was undertaken for the reservoir embankment the three techniques together were compared for the same problematic section and confirmed seepage by showing similar results conclusions were also drawn on the efficiency of using these three techniques as a package to give a comprehensive non invasive assessment to be used as common practice by local authorities and environment agencies whereby remedial action could be recommended to protect assets and civilians

horizontal to vertical spectral ratio and geological conditions the case of garner valley downhole array in southern california the aim of the present article is to further check the use of the hori zontal to vertical h v spectral ratio which has been recently suggested as an indi cator of site effects the data set consists of 1 t0 three component high sensitivity accelerograms recorded at five different depths by the garner valley downhole array gvda in southern california with peak ground accelerations 0 0002 g ag 0 04 g magnitudes 3 0 ml 4 6 and hypocentral distances 16 km r 107 km first the stability of the h v spectral ratio is investigated by computing the mean for the whole data set in different depths the h v spectral ratio on the surface is compared with the surface to depth standard spectral ratio with theoretical s wave transfer functions derived from the vertical geotechnical profile as well as with the h v spectral ratio of synthetic accelerograms generated by the discrete wavenumber method both theoretical and experimental data show a good stability of the h v spectral ratio shape which is in good agreement with the local geological structure and is insensitive to the source location and mechanism however the absolute level of the h v spectral ratio depends on the wave field and is different from the surface to depth spectral ratio consequently the h v spectral ratio tech nique provides only partially the information that can be obtained from a downhole array but surface to depth ratios may also be misleading because they combine effects at surface and at depth

extension controls quaternary tectonics geomorphology and sedimentation of the n appennies foothills and adjacent po plain italy abstract in the middle pleistocene thrusting in the n apennine fold and thrust belt came to an end and foredeep sedimentation in the adjacent po plain basin ceased a new tectono sedimentary regime was installed extensional faults were activated in the foothills and are limited to the northeast by a major sw dipping normal fault the bologna fault for which a vertical displacement of 1000 m is estimated the region northeast of the fault i e its footwall was progressively tilted towards the po plain the sw sectors of the tilting region were progressively uplifted above sea level subjected to erosion thereby feeding a deltaic system which prograded towards the northeast in the subsiding regions compressional structures without major deformation are recorded in the zone of maximum curvature all these features are explained by the onset of extensional deformation along the bologna fault and consequent flexural unloading of its footwall the evidence therefore shows that the transition region between the n apennine foothills and po plain has been under a tensional stress regime since the middle pleistocene

origin and emplacement of an inferred late jurassic subduction accretion complex euboea eastern greece in northern euboea central eastern greece an up to 3 km thick polygenetic melange pagondas complex is structurally interleaved between a triassic jurassic carbonate platform pelagonian zone and an overriding harzburgitic ophiolite the melange mainly comprises late triassic shallow water limestone and calciturbidites radiolarites triassic jurassic tholeiites alkaline basalts and minor andesites the units concerned range from kilometre sized thrust sheets and detached blocks to broken formation and structureless or bedded matrix supported conglomerates diamictite the melange includes remnants of neotethyan oceanic lithosphere overlain by radiolarites hemipelagic carbonates and distal calciturbidites derived from a mesozoic carbonate platform tholeiites were erupted at a triassic jurassic spreading axis whilst within plate type alkali basalts are interpreted mainly as seamounts kilometre scale detached blocks of shallow water coralline limestone are identified as collapsed atolls formed within an ocean and or along the rifted continental margin volcaniclastic sediments are locally interbedded with radiolarite and reflect post volcanic erosion of the ocean floor intra oceanic convergence began apparently in late early jurassic time giving rise to the euboea ophiolite above an inferred westwards dipping subduction zone the pagondas complex then developed as an accretionary prism the subduction trench later collided with the pelagonian passive margin driving the hot euobea ophiolite over the accretionary complex to produce amphibolites and greenschists of the metamorphic sole trench margin collision then drove the entire supra subduction zone complex apparently eastwards downflexing the pelagonian carbonate platform to form a foredeep in which late jurassic kimmeridgian tithonian radiolarian sediments accumulated during emplacement the accretionary complex was disrupted and partly resedimented as debris flows turbiditic volcaniclastic sandstone and shale in a foredeep or foreland basin setting

deformation of western greece during neogene clockwise rotation and collision with apulia following an early miocene phase of n s extension affecting the entire hellenides 50 clockwise rotation affected western greece modern gps analyses show rapid southwestward motion in southwestern greece over subducting oceanic lithosphere and no motion in the northwest where greece collided with apulia we aim to identify the deformation history of western greece associated with the rotation and the collision with apulia the timing of the various phases of deformation is constrained via detailed analysis of vertical motions based on paleobathymetry evolution of sedimentary sequences overlying the evolving structures the results show that accompanying the onset of rotation compression was re established in western greece in the early langhian around 15 ma subsequently western greece collided with the apulian platform leading in the late miocene to a right lateral strike slip system running from the aliakmon fault zone in northern greece via the kastaniotikos fault and the thesprotiko shear zone to the kefallonia fault zone offshore western greece ne sw compression and uplift of the ionian islands was accompanied by ne sw extension in southwestern greece associated with faster southwestward motion in the south than in the north this led in the middle pliocene around 3 5 ma to collision without further shortening in northwestern greece from then onward nw se to n s extension east of apulia and gradually increasing influence of e w extension in the south accommodated motion of the hellenides around the apulian platform as a result curved extensional basin systems evolved including the gulf of amvrakikos sperchios basin gulf of evia system and the gulf of corinth saronic gulf system

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

high frequency site effects at two parkfield downhole and surface stations abstract using stacked ratios of microearthquake source spectra recorded at the surface and 200 m downhole we have established the p and s wave site effect at two locations in parkfield california the frequency responses of both sites are bimodal being completely dominated by multiples and amplification below 10 hz and by attenuation above 30 hz the low frequency amplification factors show roughly three to five times more uphole motion compared to that downhole the multiples produce peaks with a maximum of nearly 10 times more uphole motion above 50 hz the downhole motion is always larger approaching a factor of 5 at the high frequency limits of our study when fit with a linear attenuation model the high frequency ratios yield compressional and shear q values between 6 and 19 the data were divided into subsets based on event location and time of year statistical comparison of these subsets shows no systematic variation with azimuth or season the results of our study accounts for the lack of high frequency surface reflections in the parkfield downhole data but not for the lack of source scaling of parkfield microearthquakes

tectonostratigraphic models of the alpine terranes and subduction history of the hellenides abstract the tectonostratigraphy of the hellenic terranes is related to their paleogeodynamic and paleogeographic evolution which comprises three major stages i continental rifting in the northern margin of gondwana characterised by volcanosedimentary complexes of late paleozoic triassic ii continental drifting and contemporaneous oceanic opening of tethyan basins in between the continental terranes during triassic paleogene with shallow water carbonate platforms on the continental terranes and ophiolite suites interlayered with pelagic sediments within the tethyan basins iii accretion of the tectonostratigraphic terranes with docking along the active european margin characterised by flysch melange sedimentation along the trenches from early jurassic to neogene two tectonostratigraphic models can be distinguished one for the continental terranes carbonate platforms and another for the oceanic basins the duration of each geodynamic stage for each terrane is obtained from the chronology of the tectonostratigraphic facies change the general trend is younger ages observed in the southern terranes and older ages towards the northern terranes the two alternative tectonostratigraphic models are applied in the two groups of terranes and the chronology of the geodynamic paleogeographic stages is estimated the hellenic subducted slab as shown in the seismic tomographic images is correlated to the terrane paleogeography using the estimated widths and the average subduction rates the upper 1700 km of the slab correspond to the three southern more external terranes whereas the remainingpart of the slab may represent the other more internal terranes a palinspastic model of the hellenides is presented taking into account the chronology of each stage for every terrane obduction of ophiolites over the southern platforms is observed in all four oceanic basins blueschist exhumation formation of core complexes and tectonic windows through extensional detachments occur after micro collision of continental terranes platforms and their isostatic uplift within the upper plate after their detachment from the subducting slab

investigation of rate of erosion of soils in embankment dams the slot erosion test and the hole erosion test have been developed to study the erosion characteristics of soil in cracks in embankment dams the erosion characteristics are described by the erosion rate index which measures the rate of erosion and the critical shear stress which represents the minimum shear stress when erosion starts values of the erosion rate index span from 0 to 6 indicating that soils can differ in their rates of erosion by up to 10 6 times the rate of erosion is shown to be dependent on the soil fines and clay sized content plasticity and dispersivity compaction water content density and degree of saturation and clay mineralogy and possibly the presence of cementing materials such as iron oxides coarse grained noncohesive soils in general erode more rapidly and have lower critical shear stresses than fine grained soils knowledge of the erosion characteristics of the soil in the core of an embankment dam aids in the assessment of the likelihood of dam failure due to piping erosion

seismic noise based strategies for emphasizing recent tectonic activity and local site effects the ferrara arc northern italy case study during the seismic crisis of may june 2012 that strongly affected the central sector of the ferrara arc relevant coseismic effects were observed such as ground deformations and amplification phenomena due to low quality mechanical characteristics of the shallow subsurface i e few hundreds of meters this portion of the subsurface is not investigated by neither hydrocarbon explorations too deep nor geotechnical surveys too shallow furthermore direct analysis is not cost effective to carry out over such a wide area to overcome these limitations we exploited seismic noise based strategies which are not invasive and do not require expensive equipment we carried out several single station and array measurements i e esac re mi and hvsr across some of the major tectonic structures of the eastern po plain belonging to the most advanced buried sector of the northern apennines such investigations were performed along two profiles about 27 km long and oriented ssw nne i e almost perpendicular to the regional trend of the ferrara arc structures our results clearly document lateral shear wave velocity variations and the occurrence of resonance phenomena between 0 52 and 0 85 hz additionally based on inversion procedures we were able to infer the depth of the resonant interface s and we associated such interface s to the major known stratigraphic discontinuities thus emphasizing the recent tectonic activity of the blind thrusts affecting this sector of the ferrara arc

mapping the palaeo piniada valley central greece based on systematic microtremor analyses the application of seismic noise based techniques has become particularly popular in the last decades as they are not invasive and do not require large teams or expensive equipments the horizontal to vertical spectral ratio hvsr is commonly used not only in seismic microzoning studies as far as from noise recording constraining the fundamental resonant frequency but it is also possible to infer the depth of the bedrock knowing the average shear wave velocity of the overlying sedimentary cover or viceversa i e resonance equation for the purposes of the present research more than 300 single station noise measurements were carried out across the piniada valley central greece along and between several transects planned roughly perpendicular to the mean valley trend to understand the palaeogeographic and tectonic evolution of this area we needed an estimation of the geometry at depth of the bedrock underlying the fluvial deposits of the present day pinios river as a result for each measured site we calculated the depth of the bedrock and afterwards such values were opportunely interpolated for obtaining a 3d model of the palaeo piniada valley documenting for the first time the recent late quaternary inversion of the topographic gradient

evaluation of local site effects and their removal from borehole records observed in the sendai region japan abstract we present results from a borehole observation network composed of 12 borehole sites deployed in a 20 20 km area in the sendai region japan the subsurface quaternary layers vary with each site but a pliocene layer is commonly underlying at a depth of 0 to 80 m throughout the sendai region we define this pliocene layer whose s wave velocity is larger than 500 m sec and whose n value of the standard penetration test is greater than 50 as an engineering bedrock in the region once we characterize ground motions at the engineering bedrock we can either use these motions directly in the response analysis of whole soil building systems or use them in the nonlinear analysis of soft soil layers as an input the purpose of this study is to evaluate the local site effects due to surface layers overlying the engineering bedrock and to remove them by using one dimensional 1d soil models whose properties are determined by weak motion records of 18 events first we identify s wave velocities and frequency dependent quality factors q from amplification factors between surface records and borehole records observed at 10 sites at depths of several tens of meters the identified s wave velocities are very close to s wave logging values the identified q values show strong frequency dependence proportional to f 0 46 to 1 16 where f is frequency we confirm that the observed amplification factors in the frequency range from about 0 1 to 20 hz can be explained well by the theoretical ones based on the 1d wave propagation theory with the identified s wave velocities and q then we estimate the so called engineering bedrock waves which are supposed to be observed on the outcrop of the engineering bedrock from borehole records by using the 1d models with these identified soil constants we confirm that local site effects due to surface layers overlying the engineering bedrock are properly removed so that we have similar characteristics in the resultant engineering bedrock waves from records at different sites

the pumpellyite actinolite and contiguous facies in part of the phyllite quartzite series central northern peloponnesus greece variations in assemblage and composition of the constituent minerals in basic and intermediate metavolcanics encountered in the zarouchla group of the phyllite quartzite series are consistent with a progressive sequence corresponding to temperature conditions estimated at 290 380 c minimum values under a total pressure greater than 3 5kbar and possibly as high as 5 kbar in the absence of more critical evidence the parageneses recorded in the metavolcanic rocks are interpreted as belonging to a prograde facies series from the lawsonite albitechlorite facies through the pumpellyite actinolite facies to the greenschist facies the present distribution of mineral assemblages does not show a simple increase of metamorphic grade in a given direction but is apparently related to the tectonic evolution of the metamorphic sequence

triassic shoshonites and andesites lakmon mountains western continental greece differences in primary geochemistry and sheet silicate alteration products abstract shallow marine lavas and pyroclastic rocks several tens of metres thick outcrop at the base of thrust slices in the pindos nappe in the lakmon mountains of western continental greece these volcanic rocks are basalts and andesites formed during mid triassic subduction geochemically on the basis of the potassium content shoshonitic and calc alkalic groups are distinguished principally the shoshonitic rocks contain primary k feldspar the calc alkalic rocks contain complexly zoned feldspars and are depleted in intermediate ree this depletion could reflect a small degree of partial melting of amphibole or possibly phlogopite during petrogenesis these two characteristics are found in other examples of minor calc alkalic rocks associated with shoshonites described in the literature a petrogenetic model is developed involving deeper mantle enrichment in lile and partial melting of this enriched mantle rock containing amphibole calc alkalic rocks are the result of initial partial melting and may be mixed with small amounts of magma of deeper origin further partial melting produces the more voluminous shoshonites celadonite developed as a secondary mineral during burial beneath about 1 km of mesozoic to early tertiary sediments during nappe emplacement vermiculite formed in the calc alkalic rocks in contrast smectite developed in the shoshonites because the potassium was sufficient to immobilize all available fe in celadonite

near surface attenuation and site effects from comparison of surface and deep borehole recordings abstract near surface attenuation and site effects are investigated using the seismograms of 17 local earthquakes recorded at depths of 0 0 3 1 5 2 5 and 2 9 km in the cajon pass borehole southern california the borehole penetrates 500 m of miocene sandstone and then crystalline granitic basement rock previous estimates of site response have been limited to shallower holes where the surface reflection interferes with the upgoing direct wave and the deepest sensor is not below the severe near surface effects in bedrock spectral ratios of the direct p and s waves for each earthquake between the different recording levels are well modeled with frequency independent q and amplification at the borehole q p 27 8 and q s 21 7 in the upper 2 9 km increasing from q p 26 and q s 15 in the upper 300 m to q p 133 and q s 47 between 1 5 and 3 km one event was also recorded at a surface granite site less than 1 5 km from the wellhead comparison of the 2 9 km recording with that at this granite site gives q p 50 and q s 23 the similarity of these values with those of previous studies at a wide range of sites suggests that q is very low in the near surface independent of rock type near surface amplification appears considerably more site dependent at the wellhead the amplifications at 1 hz of the direct p and s waves are 12 7 and 13 7 respectively these values include the free surface effect and are in reasonable agreement with the impedance contrast from the borehole logs at the granite site amplification of both p and s waves is less than four direct wave amplification at the wellhead is therefore at least three times that of the granite site the spectra of the direct and coda waves of the one earthquake recorded at both the wellhead and granite sites are compared with the corresponding 2 9 km recording coda wave amplification is in good agreement with the direct wave at the rock site but at the borehole the coda wave amplification factor overestimates the direct wave amplification by a factor of 3

on the characteristics of local geology and their influence on ground motions generated by the loma prieta earthquake in the san francisco bay region california strong ground motions recorded at 34 sites in the san francisco bay region from the loma prieta earthquake show marked variations in characteristics dependent on crustal structure and local geological conditions peak horizontal acceleration and velocity inferred for sites underlain by rock generally occur on the transverse component of motion they are consistently greater with lower attenuation rates than the corresponding mean value predicted by empirical curves based on previous strong motion data theoretical amplitude distributions and synthetic seismograms calculated for 10 layer models suggest that bedrock motions were elevated due in part to the wide angle reflection of s energy from the base of a relatively thin 25 km continental crust in the region characteristics of geologic and geotechnical units as currently mapped for the san francisco bay region show that average ratios of peak horizontal acceleration velocity and displacement increase with decreasing mean shear wave velocity ratios of peak acceleration for sites on soil alluvium fill bay mud are statistically larger than those for sites on hard rock sandstone shale franciscan complex spectral ratios establish the existence of predominant site periods with peak amplifications near 15 for potentially damaging levels of ground motion at some sites underlain by alluvium and fill bay mud average spectral amplifications inferred for vertical and the mean horizontal motion are respectively 1 1 for sites on the franciscan complex kjf 1 4 1 5 for sites on mesozoic and tertiary rocks tmzs 2 1 2 0 for sites on the santa clara formation qts 2 3 2 9 for sites on alluvium qal and 2 1 4 0 for sites on fill bay mud qaf qhbm these mean values are not statistically different at the 5 significance level from those inferred from previous low strain data analyses suggest that soil amplification and reflected crustal shear energy were major contributors to levels of ground motion sufficient to cause damage to vulnerable structures at distances near 100 km in the cities of san francisco and oakland

desiccation of a sensitive clay field experimental observations an excavation with three different levels was exposed to continuous evaporation during 35 days in order to observe and document the formation of shrinkage cracks in an intact and weathered sensitive marine clay desiccation of the intact saint alban clay under restrained conditions at an average evaporation rate of 0 018 cm h and an initial moisture content of 103 produced visible primary cracks after 17 h with an average spacing of 20 to 24 cm secondary cracks within each original polygon appeared after about 70 h of evaporation subhorizontal cracks at a depth of 6 to 8 cm were also created owing to differential strains induced by differential shrinkage of the soil polygons further evaporation resulted in the formation of a new set of vertical cracks after about 150 h of evaporation in the soil below the subhorizontal shear plane the shrinkage induced volume change associated with these different sets of cracks produced polygons with a protuberance at their bottom part indicating that the depth of crack propagation below the subhorizontal shear plane was about 3 to 4 cm in weathered clay at an initial moisture content of about 50 the average spacing was 10 to 12 cm indicating that spacing between primary cracks is related to soil type in the cohesionless topsoil no cracks were observed

the use of hvsr measurements for investigating buried tectonic structures the mirandola anticline northern italy as a case study the mirandola anticline represents a buried fault propagation fold which has been growing during quaternary due to the seismogenic activity of a blind segment belonging to the broader ferrara arc the last reactivation occurred during the may 2012 emilia sequence in correspondence with this structure the thickness of the marine and continental deposits of the po plain foredeep is particularly reduced in order to better define the shallow geometry of this tectonic structure and hence its recent activity we investigated in a depth range which is intermediate between the surficial morphological observations and seismic profiles information in particular we carried out numerous passive seismic measurements single station microtremor for obtaining the horizontal to vertical spectral ratio the results of a combined analysis of the peak frequency and its amplitude nicely fit the available geological information suggesting that this low cost geophysical technique could be successfully applied in other sectors of wide morphologically flat alluvial plains to investigate blind and completely buried potential seismogenic structures

triassic mid ocean ridge basalts from the argolis peninsula greece new constraints for the early oceanization phases of the neo tethyan pindos basin

analysis of borehole broadband recordings test site in the po basin northern italy we analyze the broadband recordings from a borehole station installed in the bedrock underneath the po basin northern italy and from a second station temporarily deployed on the surface at the same site to determine the surface sedimentary layer response and test the robustness of the different empirical techniques used to estimate local site effects we investigate the site amplification by evaluating the surface to downhole spectral ratios and the horizontal to vertical spectral ratios on both weak motion events and microtremors all the different empirical methods except the horizontal to vertical spectral ratios on weak motions reveal the main amplification peak at about 0 8 hz although the amplification factors are not always in agreement the 0 8 hz peak is the fundamental mode of the site due to the upper 130 m quaternary alluvium column v s 300 m sec we compare these experimental spectral functions with the theoretical 1d site response including and not including the borehole site response first we evaluate the theoretical transfer function at the surface then at depth and take the smoothed ratio the shallow velocity and attenuation structure at this site is assumed from previous studies we attempt to account for the effect of the reflected wave field in the borehole recordings in two different ways first we include the reflected wave field in the theoretical response function taking the theoretical transfer function9s ratio hst hbt and comparing it to the experimental earthquake ratios of horizontal components recorded at surface and at depth hs hb alternatively we multiply the hs hb earthquake ratio by the coherence and compare it to the surface response function this second approach does not provide a good fit to the amplitude of model response even if the shape of the ratio is in agreement with the theoretic response suggesting that multiplying by the coherence is not a good way to correct for the effect of reflected phases to further understand the goodness of our theoretical 1d model hst hbt theoretical evaluations we simulate the propagation through the shallower soil structure of the seismic waveforms recorded by the borehole sensor for a couple of events obtaining reasonably good agreement with the surface time histories both in phase and amplitude this test site and the results of this study are useful for understanding the influence of sedimentary layers on the ground shaking in the po basin the largest and most populated alluvial basin in italy

underthrusting and exhumation a comparison between the external hellenides and the hot cycladic and cold south aegean core complexes greece 1 after their emplacement in the course of the late mesozoic and the cenozoic the hellenic nappes became fragmented during late orogenic extension since the late eocene here we focus on the transition of underthrusting during nappe emplacement to exhumation during late orogenic extension to this end we compared previously published data on the structural geological and metamorphic history of the underthrusted parts of the tripolitza and ionian nappes which were exhumed in the cycladic and south aegean windows with newly obtained data on the sedimentary stratigraphic and structural development of the part of these nappes in the foreland in front of the subduction thrust the results allow the identification of two major events event 1 took place around the eocene oligocene transition and marks the onset of underthrusting of the tripolitza nappe below the pindos nappe and the ionian nappe below the tripolitza nappe respectively this led to the uplift and erosion of the pindos unit and the onset of deposition of the tripolitza and ionian flysch in front of the pindos thrust together with the formation of mylonites at the base of the metamorphosed portions of the pindos unit related to the underthrusting of the tripolitza unit event 2 occurred in the latest oligocene to earliest miocene and marks the decoupling of the ionian unit from the underthrusting plate the accretion of the tripolitza and ionian units to the overriding plate and the onset of late orogenic extension and exhumation in the overriding plate this led to the formation of the south aegean and cycladic core complexes and the subsidence of the klematia paramythia half graben throughout the early miocene

array estimators and the use of microseisms for reconnaissance of sedimentary basins a natural field seismic technique is possible to attain by observing microseisms with a suitably designed array and by digitally processing the data to obtain estimates of the phase velocities of rayleigh waves wavelengths of interest in detecting depth to the basement of sedimentary basins are in the range 2 to 20 km and correspond to wave periods from 1 to 7 s an array of five or seven seismometers deployed as an expanding cross configuration simplifies field procedures and is adequate for phase velocity measurements of rayleigh waves in the required wavelength range provided high resolution frequency wavenumber spectral analysis is used this analysis can be implemented on a minicomputer in the field results obtained from observation in a sedimentary basin of known structure show predominantly fundamental mode rayleigh wave propagation the scatter of velocity estimates is small enough to allow inversion by curve matching and depth to the basement can be computed to an accuracy of 30 percent w

overview of tectonic settings related to the rifting and opening of mesozoic ocean basins in the eastern tethys oman himalayas and eastern mediterranean regions

recent and active tectonics of the external zone of the northern apennines italy we present a comprehensive study of the recent and active tectonics of the external part of the northern apennines italy by using morphotectonic geological structural and stratigraphic analysis compared with the current seismicity of the region this analysis suggests that the external part of the northern apennines is characterised by presence of three major systems of quaternary compressive structures corresponding to 1 the apenninic watershed 2 the apennines po plain margin pede apenninic thrust front and 3 the emilia ferrara and adriatic fold systems buried below the po plain geological data and interpreted seismic sections indicate a roughly n s quaternary deformation direction with rates 2 5 mm year the shortening decreased since the pliocene when our data indicate compression in a nnw sse direction and rates up to 7 mm year the trend and kinematics of the structures affecting the apennines po plain margin and the po plain subsoil fit well the pattern of the current seismicity of the area as well as recent gps and geodetic levelling data pointing to a current activity of these thrust systems controlled by an overall compressive stress field close to the apenninic watershed earthquake focal mechanisms indicate that shallow extension is associated to deep compression the extensional events may be related to a secondary extensional stress field developing on the hangingwall of the thrust system affecting the apenninic watershed alternatively this thrust system may have been recently deactivated and overprinted by active normal faulting deeper compressive events are related to the activity of both a major basement thrust that connects at surface with the pede apenninic thrust front and a major moho structure

shear wave velocity structure of sediments from the inversion of explosion induced rayleigh waves comparison with cross hole measurements rayleigh waves generated by a 10 kg dynamite explosion were recorded along a dense linear array of 47 seismic stations the array had a total length of 1 4 km and it was deployed on the sediments of the po river floodplain near the city of ferrara northern italy the recorded signals were dominated by fundamental mode rayleigh waves several techniques including multiple filter analysis phase velocity stacking and single station cross correlation were used to obtain group and phase velocity dispersion from subsets for the data set synthetic seismograms were computed for one velocity structure showing a good match to the recorded waveforms late rayleigh wave codas were characterized by persistent monochromatic ringing interpreted as due to surface waves scattered by weak lateral heterogeneities scattering within the alluvium of the great po river valley likely occurred across a reticular system of ancient secondary river beds compared to the rest of the floodplain these preferential directions of local drainage are characterized by different sedimentary environments the availability of in situ cross hole measurements of shear wave velocities allowed the comparison with our results from surface observations demonstrating that the analysis of explosion induced rayleigh waves can be used for the geophysical characterization of flat layered structures at a local scale for seismic engineering purposes

flood risk assessment in the kosi megafan using multi criteria decision analysis a hydro geomorphic approach abstract floods are one of the most devastating natural events that lead to enormous and recurring loss of life properties and resources around the globe in india floods remain a major hazard during the monsoon season in many parts of the country but most seriously in the flat and monotonous gangetic plains in the himalayan foreland one of the most flood prone rivers in india is the kosi in north bihar eastern india which also forms the largest active megafan in the world the kosi river is known as the sorrow of bihar because of its anomalous behavior and the damage it causes due to frequent floods in this region this study evaluates the flood hazard and flood vulnerability as separate entities and combines them to assess the flood risk in the kosi megafan region geomorphological hydrological and socio economic data have been integrated in a gis framework using a multi criteria decision tool called the analytical hierarchy process ahp to generate a process based flood risk map for 105 blocks administrative units of both nepal and india bihar such maps should encourage soft engineering solutions for flood mitigation aimed at minimizing the consequences of flooding and reducing flood risks this study has significant implications for developing measures and plans that will help government and relief agencies in the identification of flood prone areas and for planning emergency management strategies in this region

predicting fractures in glacially related fine grained materials and a synthetic soil of bentonite and sand using soil texture abstract scientists and engineers from many disciplines have been studying the formation of fractures in fine grained natural geologic materials and fill naturally occurring fractures in the fine grained materials can create preferential flow paths which can allow water to infiltrate quickly resulting in recharge to underlying aquifers but also allowing contaminants to pass through to aquifers potentially threatening ground water drinking water sources they can also create zones of weakness that allow piping in dams and slip zones in fill materials glacially related fine grained materials are widely distributed across the northern hemisphere including the u s states of minnesota wisconsin michigan iowa illinois indiana and ohio canada and much of northern europe it has been difficult to predict the presence of these fractures the objective of this research was to analyze soil textures of fractured soils and determine boundary conditions for predicting the likelihood of fractures in similar materials graphically representing the predictive model on the usda soil texture ternary diagram an extensive midwestern u s data set 275 data points including ohio iowa michigan and wisconsin soil samples was studied the texture data of those glacially related fine grained materials containing fractures indicate that those with 6 5 clay can be predicted to support fractures an auxiliary experiment using bentonite suggests that this predictive model may be applicable beyond the clay mineralogies common to the u s midwest this is a promising method of predicting which soil textures are most likely to form fractures and can be a useful field tool for engineering geologists soil scientists and other environmental professionals it is immediately applicable to the u s midwestern sites and with additional analyses using other soils could be used more widely across glaciated north america and northern europe

measurement of q 1 for s waves in mudstone at chikura japan comparison of incident and reflected phases in borehole seismograms seismograms from small events in the southern kanto region have been recorded by a seismometer installed in a 732 m deep borehole at chikura observatory japan where mudstone of early pliocene age is found from the ground surface to the bottom of the borehole strong phases occurring 1 5 1 6 sec after the s wave arrival were interpreted as reflections at the ground surface ray path directions of the incident s waves were determined from the minimum principal axis of the three dimensional trajectory ellipsoid which represents the particle motion for a head wave of s phase transverse horizontal sh components were used to estimate the q 1 value for s waves assuming the free surface acted as an 100 reflector for the sh waves and the incident sh phase as an input and the reflected phase as an output we calculated system functions the q 1 value was measured from the transfer characteristics between the incident and the reflected phases in a single seismogram thus no corrections were necessary for source or site including instrument effects if we applied a power law model the following relationship was obtained from the regression analyses of 20 events log 10 q 1 0 52 0 48 log 10 f 1 28 0 22 1 0 f 5 0 hz where f is frequency in hz and error values are the 95 confidence levels of the regression coefficients

magmatic evolution of the tethysides a guide to reconstruction of collage history abstract the magmatic evolution of the tethyside super orogenic complex is reviewed in five time frames and magmatic products are displayed on corresponding non palinspastic suture maps on these maps a one to one relationship between suture zones drawn mostly using non magmatic criteria such as stratigraphy and structural style except for ophiolites and plate boundary magmatism is seen subduction related magmatism is most persistent both spatially and temporally and forms the best magmatic guide to former sutures post collisional magmatism is the next in abundance but is less helpful in delineating sutures in detail ophiolites come third in abundance magmatism associated with the rifting is very sparse along the tethyside sutures taken all together magmatic rocks along the tethysides record continuous tectonic evolution and form superb guides to the detection of the primary orogenic collage components in the tethysides and to their distinction from the secondary orogenic collage components that form through intracontinental deformation it is surprising how well even the smallest of the primary orogenic collage components are delineated by magmatic arc rocks this contrasts with a common interpretation of the north american cordilleran orogenic collage

the structure and regional significance of the talea ori crete abstract on the basis of detailed geological mapping in the talea ori of crete metamorphic rocks previously interpreted as basement to the plattenkalk series are re interpreted as down faulted parts of the overlying phyllite quartzite series nappe a supposed unconformity separating these two units is shown to be a high angle fault the phyllite quartzite series and overlying nappes were affected by two major deformational phases whereas the plattenkalk series has a simpler structural history and was folded and imbricated by southwards directed overthrusting which emplaced the phyllite quartzite series nappe and other overlying nappes in the oligocene we reject previous models of a huge inversion of the plattenkalk series and we also consider that considerable local inversion by tight to isoclinal folding and thrusting means that the stratigraphic thickness is much less than previously appreciated the differences between the structural and sedimentological histories of the plattenkalk series and the overlying nappes implies that they were separated by a major crustal discontinuity such as a transform or transcurrent fault before the oligocene overthrusting

the effect of lateral heterogeneity on horizontal to vertical spectral ratio of microtremors inferred from observation and synthetics abstract horizontal to vertical h v spectral ratios of microtremors hvrm have been traditionally interpreted as representing either the s wave amplification directly or the rayleigh wave ellipticity for a horizontally layered structure however based on the diffuse field theory we have derived an alternative theoretical basis that hvrm corresponds to the square root of the ratio between the imaginary part of the horizontal green s function and that of the vertical one under that condition the 1d horizontal layering assumption is not needed to interpret hvrm as observational evidence of such non 1d hvrm we discovered significant directional dependency at a site on the uji campus kyoto university japan the observed microtremor north south vertical spectral ratios are quite stable and have only one peak around 0 5 hz on the other hand the east west vertical spectral ratios are smaller in amplitude and have higher peak frequencies and sometimes two separated peaks the directional dependency of observed hvrm is aligned to the axis of the 2d basin structure we performed numerical analyses by spectral element method using a unit load on the surface to examine the effect of the 2d basin structure on the imaginary parts of the green s functions we found that the 2d basin structure clearly changes the characteristics of the h v spectral ratios in both perpendicular and parallel directions relative to the basin axis thus we succeeded in theoretically simulating the qualitative difference between the h v spectral ratios for two orthogonal horizontal components of the hvrm observed on the uji campus online material snapshots and animations of wave propagation

geochemistry tectonic setting and metamorphism of mid triassic volcanic rocks of greece abstract mid triassic volcanic rocks are preserved in about eight localities in the nappes of the external hellenides and are also widespread in the pelagonian zone of central greece most have suffered low grade metamorphism immobile trace elements from 35 samples 80 major element analyses and pyroxene analyses show that these rocks are the product of an eastward dipping subduction zone the subducted ocean was perhaps analogous to the pennine zone of the alps the othris and pindos ophiolites are probably contemporaneous products of related back arc extension metamorphic mineral assemblages in volcanic rocks of the phyllite series of the external hellenides indicate high pressure low temperature conditions probably related to a second subduction that occurred prior to the main phase of hellenide nappe emplacement in the miocene

from obduction to continental collision new data from central greece the aim of this paper is to contribute to deciphering the evolutionary history of the hellenides by the study of a large sector of the chain located between the front of the ophiolitic units and the external zones classically attributed to the continental margin of adria in particular the tectonic units located in boeotia a key area located in central greece at the boundary between the internal and external hellenides were studied from structural stratigraphic and biostratigraphic points of view addressing the main debated aspects concerning the origin of the ophiolite nappe s the tectonic evolution of the hellenic orogen was revised with a particular emphasis on the period between obduction and continental collision new findings were compared with consolidated data concerning the main metamorphic events recorded in the more internal hellenides geochemistry and age of the ophiolites and main stratigraphic constraints obtained in other sectors of the belt finally a new reconstruction of the tectonic evolution of this area was introduced and in the context of the dispute concerning the origin of the ophiolitic belts as a possible record of multiple oceanic basins we put forward for consideration a single ocean tectonic model spanning from triassic up to tertiary times and valid for the whole hellenic albanian sector

late carboniferous plutonism within the pre alpine basement of the external hellenides kithira greece evidence from u pb zircon dating in memory of theodor doutsos for his invaluable contribution to the understanding of geology of greece u pb zircon dating of three granitic orthogneisses sampled from kithira island sw greece provide the first reliable evidence for carboniferous plutonism within the pre alpine basement of the external hellenides concordant zircons from two samples yielded ages at 324 2 ma and 323 3 ma whereas the third sample yielded a lower intercept age at 320 1 2 ma the concordant ages are interpreted to date the emplacement of the igneous protolith ages of inherited zircons of two orthogneisses range from 2 5 to 2 4 ga indicating late archaean early proterozoic crustal components in combination with published ages for other aegean metagranitoids the new u pb ages provide additional evidence of a temporally restricted period of plutonism in the pre alpine aegean region from 325 to 300 ma comparing the post neoproterozoic evolution of the investigated basement with that of the cycladic and pelagonian basements and of the continental massifs of ne greece and turkey we argue that all these crustal blocks were part of the gondwana derived cimmerian terrane based on the spatial and temporal distribution of late carboniferous aegean plutonism we suggest that this period of magmatic events results from the southward subduction of palaeotethys beneath the marginal fragments of northern gondwana

cohesive slope surface failure and evaluation this paper highlights the mechanism of slope surface failure that occurs on highway embankments with cohesive soils based on systematic instrumentation in the field the major reason for such surface failures is ascribed to the reduction of soil strength due to the seasonal variation of moisture content in embankment soils shrinkage cracks develop in an embankment during dry seasons a great amount of rainfall then infiltrates into embankment soils through these cracks in subsequent wet seasons as such the shear strength of embankment soils progressively decreases as soils swell until a surface failure occurs this surface failure mechanism was indirectly studied through a series of shrinkage and unconfined compressive tests on cohesive soil similar to that at the highway embankment a limit equilibrium analysis method was also suggested accordingly for the back calculation of slope stability finally a rehabilitation technique using nonwoven geotextile was recommended for highway maintenance engineers to repair such slope surface failures

the water retention properties of a natural unsaturated loess from northern france the water retention properties of a natural loess from northern france were investigated on intact block samples that were excavated along a high speed train line tgv that experienced stability problems during heavy rain episodes suction measurements were made by using the filter paper method and an in house constructed high capacity tensiometer hct so as to determine the water retention curve of the loess the results showed that an alternative approach using a previously wetted filter paper could fruitfully be used with suction values reasonably compatible with the hct measurements the water retention curve obtained exhibited a peculiar form with no hysteresis observed around the natural water content 14 4 and two hysteresis loops on both the wet and dry sides of the curve it is hypothesised that this zone with no hysteresis corresponds to the natural variations of the water content under seasonal changes providing a range of natural suction between 20 and 80 kpa and it is suggested that th

ocean ridge origin and tectonic setting of mesozoic sulphide and oxide deposits of the argolis peninsula of the peloponnesus greece abstract metal oxide and sulphide deposits chemically similar to the hydrothermal deposits of modern and ancient oceanic spreading axes occur in two areas of the argolis peninsula of the peloponnesus greece in the first in northeastern and central argolis manganese ores immediately overlie morb type extrusives of mid jurassic age after triassic rifting this oceanic crust formed during jurassic time and was then tectonically emplaced over the adjacent continental margin in the late jurassic the manganese ores palea epidavros were precipitated from low temperature hydrothermal vent waters on the axis of a relatively unrifted ocean ridge which was possibly slow spreading the deep sea sediment cover comprises pelagic carbonate accumulated on the ridge flanks then ribbon radiolarites deposited on the abyssal plain below the ccd located close enough to a continental margin to allow deposition of shallow water derived calciturbidites in the second area ermioni in the southern argolis peninsula adheres massive sulphides and metalliferous oxide sediments occur with mafic extrusives and terrigenous turbidites although previously regarded as a single stratigraphical succession shale sandstone formation the mafic lavas and metal deposits are interpreted here as ophiolitic slices that were incorporated into the turbidites by thrusting possibly as a trench accretionary complex the massive sulphides were precipitated from high temperature vents sited near the axis of a relatively unrifted spreading ridge which was possibly fast spreading ferruginous ochres and ferromanganiferous umbers oxide sediments were dispersed around these vents whereas strongly fractionated manganese ores precipitated from separate low temperature hydrothermal sites alternative tectonic scenarios are discussed

triassic shoshonites from the dolomites northern italy alkaline arc rocks in a strike slip setting triassic igneous rocks of the dolomites are typical shoshonites with high k2o sio2 and k2o na2o ratios and low fe contents they have mid ocean ridge basalt like abundances of high field strength elements but are highly enriched in large ion lithophile lil elements rb sr ba k the effects of crustal contamination and fractional crystallization have been superimposed on initial lil element enrichment lavas of similar composition occur in papua new guinea fiji the absaroka mountains and the eolian islands these suites are all associated with destructive plate margins but were not erupted until after subduction had ceased examination of mediterranean paleogeography indicates that no subduction event which could have given rise to the shoshonites of the dolomites occurred during the triassic in fact the tectonic setting at the time of eruption of the lavas was probably one of strike slip faulting the suite may have inherited its arc signature from permo carboniferous subduction of the ocean between laurasia and gondawanaland prior to the hercynian orogeny

hvsr deep mapping tested down to 1 8 km in po plane valley italy abstract the horizontal to vertical spectral ratio hvsr of seismic noise is extensively used in seismic microzonation for its capability to provide a good approximation to the subsoil main resonance frequencies of geotechnical and seismic engineering interest this implies in turn that it has also an approximate passive subsoil mapping capability independent of the level of noise illumination albeit limited to relatively shallow depths since tilt sensitivity makes hvsr unreliable below 0 1 hz however we have experimentally verified that hvsr subsoil mapping capability extends to depths in the kilometer range by applying it to the largest sedimentary basin of italy the po plain valley there we were able to resolve the major stratigraphic discontinuities down to the sediment bedrock interface for which we estimated a depth of 1 6 km with a 25 uncertainty while the surface mapped from oil exploration indicates a depth of 1 8 km quarter of an hour recordings gave always stable signals that fitted to synthetic curves using as a constraint the parameters of the shallow subsoil provided a stratigraphic map consistent with the independent survey this candidates hvsr as a fast and inexpensive first order subsoil mapping tool down to depths of geological and exploration interest

rapid exhumation of high pressure metamorphic rocks in kythera peloponnese greece revealed by apatite u th he thermochronology abstractapatite u th he and apatite fission track cooling ages from high pressure hp metamorphic rocks in the south aegean forearc along the kythera strait kythera and southeastern peloponnese suggest rapid exhumation during middle to late miocene times hp rocks from the kythera strait exhibit two perpendicular extensional structures samples with arc normal or arc parallel extensional fabrics yielded apatite u th he cooling ages of 8 10 ma the more precise u th he ages are consistent with previously reported apatite and zircon fission track ages obtained from the same rock units the less precise but still accurate fission track data provided a reference for u th he dating on relatively young uranium poor apatites the combined data therefore precisely and accurately constrain the exhumation history of hp rocks and indicate that localized arc parallel extension in the kythera strait was active for an 5 m yr interval during the regional arc expansion

early mesozoic oceanic subduction related volcanic rocks pindos basin greece abstract small outcrops of volcanic rocks of mid triassic to early jurassic age in the deep water mesozoic pindos basin have been systematically sampled and analysed geochemically to interpret the tectonic environment in which these rocks formed associated sediments indicate a rifting environment the volcanic rocks include all the main types found in modern back arc basins shoshonites with clinopyroxenes of calc alkaline affinity occur at the basin margin minor enriched type morb contains clinopyroxene typical of morb minor basalts that resemble oib with some subduction related characteristics contain clinopyroxene typical of alkahne rocks thick andesites and pyroclastic rocks with morb like trace elements except for some lile enrichment are associated with cumulate gabbro and oceanic type plagiogranite these thick andesites and pyroclastic rocks formed at an intra backarc ocean ocean subduction zone the supra subduction zone ophiolites of the eastern margin of the pindos basin which are of similar age are probably related to the same subduction zone the overall volcanic assemblage is related to formation of a back arc basin associated with the subduction of paleo tethys the hypothesis that late triassic eariy jurassic rifting formed only small pull apart basins by transtension is inconsistent with the range of volcanic products and the evidence for significant intra back arc subduction

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

a study of the correlation between electrical resistivity and matric suction for unsaturated ash fall pyroclastic soils in the campania region southern italy in the territory of the campania region southern italy critical rainfall events periodically trigger dangerous fast slope movements involving ashy and pyroclastic soils originated by the explosive phases of the mt somma vesuvius volcano and deposited along the surrounding mountain ranges in this paper an integration of engineering geological and geophysical measurements is presented to characterize unsaturated pyroclastic samples collected in a test area on the sarno mountains salerno and avellino provinces campania region the laboratory analyses were aimed at defining both soil water retention and electrical resistivity curves versus water content from the matching of the experimental data a direct relationship between electrical resistivity and matric suction is retrieved for the investigated soil horizons typical of an ash fall pyroclastic succession the obtained relation turns out to be helpful in characterizing soils up to close saturation which is a critical condition for the trigger of slope failure in such a regime the water content and the matric suction have small variations while electrical resistivity variations can be appreciated in a larger range of values for this reason besides suction measurements on very small soil volumes through classical tensiometers our analyses suggest the direct monitoring of in situ electrical resistivity values as an effective tool to recognise the hydrological state of larger and more representative soil volumes and to improve early warning of dangerous slope movements

a new active tectonic model for the construction of the northern apennines mountain front near bologna italy 1 we integrate existing and new geologic data retreating trench extension and accretion tectonics retreat project particularly on the origin growth and activity of the mountain front at bologna italy into a new model that explains apennine orogenesis in the context of a slab rollback upper plate retreat process the bologna mountain front is an actively growing structure driving rock uplift 1 mm year cored by a midcrustal flat ramp structure that accommodates ongoing shortening driven by adria subduction at a rate of 2 5 mm year the data we use are assembled from river terraces and associated pleistocene growth strata geodesy including releveling surveys reinterpretation of published reflection lines and a new high resolution reflection line these data constrain a simple trishear model that inverts for blind thrust ramp depth dip and slip apennine extension is recognized both in the foreland as high angle normal faults and modest stretching in the carapace of the growing mountain front and in the hinterland with larger normal faults that accomplish some crustal thinning as the upper plate retreats this coevolution of extension and shortening shares some notable characteristics with other basement involved collisional orogens including the early tertiary laramide orogeny in the american west and the oligocene to miocene evolution of the alps we propose a possible relationship between underplating and the development of the po as a sag basin as a quaternary phenomenon that may also apply to past periods of apennine deformation tortonian continued shortening on the structure beneath the bologna mountain front represents by far the most important and underappreciated seismogenic source in the front of the northern apennines

a general inversion scheme for source site and propagation characteristics using multiply recorded sets of moderate sized earthquakes abstract we derive an inversion scheme that fits the logarithms of seismic body wave spectra to 2 source shapes conditioned by anelastic attenuation with a frequency independent q the residuals from this fit are then projected onto the set of sources and sites with the source terms damped to estimate residual source spectra and site response spectra this two part inversion process is iterated until the square of the residuals summed over frequency for all recordings is minimized the absolute amplitudes of the source and site spectra are determined by fitting the site response spectra to estimates of the site amplification derived from geotechnical data we apply this inversion process to three sets of recordings of loma prieta aftershocks the first data set contains s waves recorded both in the marina district and at nearby hard rock stations we constrain the site response using the s wave velocity measured in a nearby borehole the absolute site amplifications for the marina stations are 15 to 20 at 1 hz and 10 at 2 5 hz the other two data sets comprise the p and s wave recordings from 28 aftershocks ranging in size from m d 2 1 to 4 6 obtained at accelerograph sites near the epicentral area the p and s wave attenuations determined from the inversions are q 414 and 380 while the average near site attenuations are t 0 012 and 0 026 sec respectively the average ratio of the s to p wave seismic moments is 1 1 0 1 the ratio of the p to s wave corner frequencies is 1 24 0 11 and the ratio of s to p wave radiated energy is 13 9 3 2 the brune stress drops for these aftershocks range from 8 to 800 bars the largest earthquakes exhibit the largest stress drops but there is no apparent dependence of stress drop on seismic moment for earthquakes with 10 19 m 0 21 dyne cm

assessment of liquefaction potential for two liquefaction prone areas considering the may 20 2012 emilia italy earthquake abstract on the 20th and 29th of may 2012 two earthquakes occurred in emilia romagna region northern italy triggering extensive liquefaction of the subsoil units the consequences of liquefaction have been observed and reported by several agencies in a widespread area the most impressive liquefaction manifestations were documented in a zone 3 4 km long and 1 km wide where the villages of sant agostino san carlo and mirabello are located the existing post earthquake reports and the availability of geotechnical data provided by in situ tests consist the basic ingredients for a computation of the liquefaction potential parameters within this zone in particular the liquefaction potential index lpi and liquefaction severity number lsn indexes were evaluated and then correlated by considering liquefaction phenomena either observed on site or not thus the existing classifications of the lpi and lsn were evaluated and compared with the observed liquefaction induced deformations the latter was applied and validated for the first time within a liquefiable area using post earthquake data after the development by tonkin and taylor 2013 the outcome of this study shows that a threshold value of lpi around 13 or 14 is better to be taken into account instead of 5 for discriminating sites where liquefaction surface evidences should be expected from the non liquefied ones moreover from the correlation of the lsn values with the cases of liquefaction induced ground disruption it is concluded that the proposed threshold value of 10 fits statistically well with our dataset in addition a preliminary correlation of lpi and lsn indicates a trend that could be useful in future studies for delineating sites likely to liquefaction

the influence of wind on measurements of seismic noise summary the horizontal to vertical spectral ratio hvsr technique of microtremor measurement is widely applied in microzonation and site response studies given the small amplitude of the measured signal unwanted disturbances may adversely affect the results we analysed the influence of local wind on microtremor measurements as follows first we studied variation in hvsr at a permanent three component seismological station under various wind patterns second we conducted an experiment under controlled condition in a wind room equipped with a laser particle image velocimeter analysing the effect of increasing wind speed on various sensor digitizer configurations third we undertook numerical modelling to explain the observed data our main conclusions are that wind increases the amplitude of all components of the microtremor wavefield but does not affect hvsr however certain sensor digitizer configurations can be adversely affected by instrumental noise due to turbulence at the air instrument ground interface

telluric and magnetotelluric study of the ferrara high northern italy abstract a telluric survey and several magnetotelluric mt soundings have been carried out across the ferrara high northern italy in a geothermal area previously explored in detail during a search for oil the aim was to compare telluric mt and gravimetric data with a structural model derived from a seismic investigation in a region of fairly well known geology the comparison between observed and predicted telluric pseudo sections reveals a much better agreement than expected especially since the gravimetric field data clearly show that the structure is effectively 3 d whereas the comparison was restricted to a single profile with 2 d interpretations the 3 d character seems to appear most clearly in the telluric parameters at periods 10 s in the search for a 2 d interpretation of the telluric and mt data an attempt was made to reduce the family of possible models by imposing external constraints it was gratifying to find that the best fit with the seismic 2 d model was obtained when a uniform resistivity was required for each of the separate formations revealed by the seismic sounding

the middle triassic magmatic tectonic arc development in the southern alps abstract the geodynamic meaning of the middle triassic magmatic and tectonic events in the southern alps is still uncertain the main problem is the significance of the compressional tectonic structures recognized in the central dolomites in fact these structures are incompatible with the extensional geodynamic interpretation crustal rifting assumed by several authors therefore the compressional tectonic elements of the dolomites have been mostly ignored or not seriously taken into account or considered as local phenomena due to the volcanic tectonic interplay other more modern interpretations are founded on regional transcurrent and or transpressive tectonics recent discovery of a middle triassic thrust system located in the piave river area some tens of kilometres east of the central dolomites lends more credence to the compressional middle triassic event the magmatic series of volcanic and plutonic middle triassic rocks display an orogenic character with typical calc alkaline trends recognized across the whole southern alps as well as in the dinaric and hellenic domains such a character is rather uncommon in the crustal evolution by rifting but is more in accord with a compressional geodynamic setting furthermore the time space distribution of the south alpine magmatic rocks coupled with their petrochemical affinity are close to the modern volcanic arcs nevertheless the general geodynamic context of the southern alps owing to their pronounced ensialic character does not fit the oceanic model

the seismotectonics of the po plain northern italy tectonic diversity in a blind faulting domain we present a systematic and updated overview of a seismotectonic model for the po plain northern italy this flat and apparently quiet tectonic domain is in fact rather active as it comprises the shortened foreland and foredeep of both the southern alps and the northern apennines assessing its seismic hazard is crucial due to the concentration of population industrial activities and critical infrastructures but it is also complicated because a the region is geologically very diverse and b nearly all potential seismogenic faults are buried beneath a thick blanket of pliocene pleistocene sediments and thus can be investigated only indirectly identifying and parameterizing the potential seismogenic faults of the po plain requires proper consideration of their depth geometry kinematics earthquake potential and location with respect to the two confronting orogens to this end we subdivided them into four main homogeneous groups over the past 15 years we developed new strategies for coping with this diversity resorting to different data and modeling approaches as required by each individual fault group the most significant faults occur beneath the thrust fronts of the ferrara romagna and emilia arcs which correspond to the most advanced and buried portions of the northern apennines and were the locus of the destructive may 2012 earthquake sequence the largest known po plain earthquake however occurred on an elusive reactivated fault cutting the alpine foreland south of verona significant earthquakes are expected to be generated also by a set of transverse structures segmenting the thrust system and by the deeper ramps of the apennines thrusts the new dataset is intended to be included in the next version of the database of individual seismogenic sources diss http diss rm ingv it diss version 3 2 0 developed and maintained by ingv to improve completeness of potential sources for seismic hazard assessment

polarization and coherence of 5 to 30 hz seismic wave fields at a hard rock site and their relevance to velocity heterogeneities in the crust abstract except for its very onset the p wave of earthquakes and chemical explosions observed at two narrow aperture arrays on hard rock sites in the adirondack mountains have a nearly random polarization the amount of energy on the vertical radial and transverse components is about equal over the frequency range 5 to 30 hz for the entire seismogram the spatial coherence of the seismograms is approximately exp cf x where c is in the range 0 4 to 0 7 km 1 hz 1 f is frequency and x is the distance between array elements vertical radial and transverse components were quite coherent over the aperture of the array indicating that the transverse motion of the compressional wave is a property of relatively large 10 6 m 3 volumes of rock and not just an anomaly caused by a malfunctioning instrument poor instrument rock coupling or out crop scale effects the spatial coherence is approximately independent of component epicentral azimuth and range and whether p or s wave coda is being considered at least for propagation distances between 5 and 170 km these results imply a strongly and three dimensionally heterogeneous crust with near receiver scattering in the uppermost crust controlling the coherence properties of the waves

synthesis of the tectonic sedimentary evolution of the mesozoic early cenozoic pindos ocean evidence from the nw peloponnese greece

tectono stratigraphy and evolution of the mesozoic pindos ophiolite and related units northwestern greece the northwest pindos mountains expose mesozoic and tertiary thrust sheets which include the jurassic pindos ophiolite composed of ultramafic and mafic oceanic crustal rocks the tectono stratigraphy of these units is i mainly ultramafic ophiolitic thrust sheet and basal metamorphic sole dramala complex and loumnitsa unit ii late cretaceous platformal limestones orliakas group iii dismembered intrusive and extrusive ophiolitic rocks aspropotamos complex iv tectonic melange and olistostromes dominated by triassic jurassic volcanic and sedimtntary rocks avdella melange v coherent thrust sheets of late jurassic late cretaceous deep water sediments dio dendra group vi early tertiary flysch pindos flysch immobile trace element studies indicate that triassic and jurassic extrusives of the volcanic sedimentary melange formed mainly at within plate and or mid ocean ridge settings by contrast structurally overlying ophiolitic extrusives include boninitic volcanics and island arc tholeiites of supra subduction zone origin initial ophiolite displacement c 165 ma is recorded in metamorphic sole formation including basal peridotite mylonite amphibolites and greenschists the sole rocks have morb and wpb chemical affinities in our favoured model the pindos ophiolite formed above a mid jurassic westerly dipping intra oceanic subduction zone accompanied by accretion to form melange followed by collision and emplacement with the pelagonian margin final suturing of the pindos ocean however did not take place until early tertiary times

neotethyan evolution of eastern greece pagondas melange evia island inferred from radiolarian biostratigraphy and the geochemistry of associated extrusive rocks this paper presents new radiolarian biostratigraphic and igneous metamorphic geochemical data for a mesozoic volcanic sedimentary melange on the island of evia euboea or evvoia eastern greece this melange includes dismembered thrust sheets and blocks of radiolarian chert and basalt biostratigraphic age data show that radiolarites interbedded with basalt derived coarse clastic sediments near the base of a coherent succession were deposited in middle and late triassic time late ladinian carnian norian geochemical evidence shows that associated extrusive rocks of inferred triassic age range from enriched alkaline basalts to transitional basalts and more depleted mid ocean ridge type basalts amphibolite facies meta basalts from the metamorphic sole of the over riding evia ophiolite exhibit similar chemical compositions both the basalts and the meta basalts commonly show an apparent subduction related influence e g relative nb depletion that may have been inherited from a previous subduction event in the region the basalts are interpreted to have erupted during middle late triassic time late ladinian carnian related to initial opening of a neotethyan ocean basin adjacent to a rifted continental margin radiolarites located stratigraphically higher in the coherent succession studied are dated as middle jurassic late bathonian early callovian similar aged radiolarites are depositionally associated with ophiolitic rocks including boninites in some other areas of greece and albania during initial ocean basin closure bajocian bathonian the adjacent shallow water carbonate platform pelagonian zone disintegrated to form basins in which siliceous sediments were deposited and highs on which shallow water carbonates continued to accumulate this facies differentiation is seen as a response to crustal flexure as the neotethyan ocean began to close the over riding pagondas melange and other similar units in the region are interpreted as accretionary prisms related to subduction of neotethyan oceanic crust in middle late jurassic time these melanges were emplaced probably diachronously during oxfordian kimmeridgian time when the passive margin collapsed creating a foredeep ahead of advancing thrust sheets of melange and ophiolites

site effect evaluation using spectral ratios with only one station the spectral ratio technique is a common useful way to estimate empirical transfer function to evaluate site effects in regions of moderate to high seismicity the purpose of this paper is to show that it is possible to estimate empirical transfer function using spectral ratios between horizontal and vertical components of motion without a reference station the technique originally proposed by nakamura to analyze rayleigh waves in the microtremor records is presented briefly and it is discussed why it may be applicable to study the intense s wave part in earthquake records results are presented for three different cities in mexico oaxaca oax acapulco gro and mexico city these cities are very different by their geological and tectonic contexts and also by the very different epicentral distances to the main seismogenic zones affecting each city each time we compare the results of nakamura s technique with standard spectral ratios in all three cases the results are very encouraging we conclude that if site effects are caused by simple geology a first estimate of dominant period and local amplification level can be obtained using records of only one station

what is a reference site many methods for estimating site response compare ground motions at sites of interest to a nearby rock site that is considered a reference motion the critical assumption in these methods is that the surface rock site record reference is equivalent to the input motion at the base of the soil layers data collected in this study show that surface rock sites can have a site response of their own which could lead to an underestimation of the seismic hazard when these sites are used as reference sites data were collected from local and regional earthquakes on digital recorders both at the surface and in boreholes at two rock sites and one basin site in the san jacinto mountains southern california the two rock sites keenwild and pinon flat are located on granitic bedrock of the southern california peninsular ranges batholith the basin site garner valley is an ancestral lake bed with watersaturated sediments on top of a section of decomposed granite which overlies the competent bedrock ground motion is recorded simultaneously at the surface and in the bedrock at all three sites when the surface rock sites are used as the reference site i e the surface rock motion is used as the input to the basin the computed amplification underestimates the actual amplification at the basin site for frequencies above 2 to 5 hz this underestimation by a factor of 2 to 4 depending on frequency and site results from the rock sites having a site response of their own above the 2 to 5 hz frequencies the near surface weathering and cracking of the bedrock affects the recorded ground motions at frequencies of engineering interest even at sites that appear to be located on competent crystalline rock the bedrock borehole ground motion can be used as the reference motion but the effect of the downgoing wave field and the resulting destructive interference must be considered this destructive interference may produce pseudo resonances in the spectral amplification estimates if one is careful the bedrock borehole ground motion can be considered a good reference site for seismic hazard analysis even at distances as large as 20 km from the soil site

the mid triassic volcanic rocks of lakonia greece thick subaerial volcanic sequences of probable mid triassic age rest unconformably on permo carboniferous limestones in the phyllite series within the gavrovo tripolitsa zone of the external hellenide nappes the volcanic rocks are varied in character pyroclastic rocks often reddened predominate but minor basalt or andesite and rhyolitic hypabyssal intrusions and flows are also found the rocks have experienced low grade metamorphism and the only relict primary minerals are pyroxene and rare plagioclase in basic rocks and potash feldspar in acid rocks the most important metamorphic phases are albite chlorite potassium mica epidote hematite quartz and pumpellyite twenty seven whole rock major element analyses suggest that there has been some exchange of na 2 o and k 2 o for cao during metamorphism but that other elements have been relatively stable a genetic interpretation of the rocks is attempted using published geochemical discriminator diagrams the basic rocks are tholeiitic in major element chemistry and pyroxene composition trace element hf ta th ce yb distribution suggests magma generation at a destructive plate margin

zircon geochronology of basement rocks from the pelagonian zone greece constraints on the pre alpine evolution of the westernmost internal hellenides the pelagonian zone of greece is the westernmost segment of the internal hellenides comprising widespread crystalline basement exposures of granites and orthogneisses we dated these basement rocks in order to identify the major crust forming episodes and to understand the evolutionary history of the area in our study we investigated granites gneisses meta rhyolites and mylonites from the major occurrences of the pelagonian zone we applied single zircon dating techniques such as pb pb evaporation conventional u pb and shrimp the majority of the basement rocks gave permo carboniferous intrusion ages thus emphasizing the importance of this crust forming event for the internal hellenides of greece triassic intrusion ages were obtained however for a meta rhyolite from the western pelagonian zone and two mylonites from the eastern pelagonian zone these ages are interpreted to reflect magmatism accompanying early rifting that led to the subsequent opening of the pindos ocean to the west and the meliata ocean to the east of the pelagonian zone the geochronological results demonstrate that the magmatic episodes during which most of the pelagonian zone crystalline basement formed are predominantly pre alpine in age

site amplification in the san fernando valley california variability of site effect estimation using the s wave coda and h v methods during the months that followed the 17 january 1994 m 6 7 northridge california earthquake portable digital seismic stations were deployed in the san fernando basin to record aftershock data and estimate site amplification factors this study analyzes data recorded on 31 three component stations from 38 aftershocks ranging from m 3 0 to m 5 1 and depths from 0 2 to 19 km site responses from the 31 stations are estimated from coda waves s waves and ratios of horizontal to vertical h v recordings for the coda and the s waves site response is estimated using both direct spectral ratios and a generalized inversion scheme results from the inversions indicate that the effect of qs can be significant especially at high frequencies site amplifications estimated from the coda of the vertical and horizontal components can be significantly different from each other depending on the choice of the reference site the difference is reduced when an average of six rock sites is used as a reference site in addition when using this multi reference site the coda amplification from rock sites is usually within a factor of 2 of the amplification determined from the direct spectral ratios and the inversion of the s waves however for nonrock sites the coda amplification can be larger by a factor of 2 or more when compared with the amplification estimated from the direct spectral ratios and the inversion of the s waves the h v method for estimating site response is found to extract the same predominant peaks as the direct spectral ratio and the inversion methods the amplifications determined from the hiv method are however different from the amplifications determined from the other methods finally the stations were grouped into classes based on two different classifications general geology and a more detailed classification using a quaternary geology map for the los angeles and san fernando areas average site response estimates using the site characterization based on the detailed geology show better correlation between amplification and surface geology than the general geology classification

garner valley downhole array of accelerometers instrumentation and preliminary data analysis the garner valley downhole array gvda in southern california 33 41 60 n 116 40 20 w is a five element array of three component dual gain force balance accelerometers that are capable of measuring accelerations from 3 10 6 to 2 0 g over a frequency range from 0 0 to 100 hz the accelerometers are placed at depths of 0 6 15 22 and 220 m the lithostratigraphy is 19 m of soil overlying a 24 m layer of weathered granite below which is granite tonalite the array only 7 km from the san jacinto fault is located at the northern end of the anza seismic gap on the san jacinto fault where an m 6 5 or greater earthquake can be expected it is only 35 km from the indio segment of the san andreas fault which last ruptured with an m 8 earthquake around 1700 a d from its installation in july 1989 through july 1991 gvda has recorded 280 earthquakes with magnitudes ranging from 1 2 to 4 7 and epicentral distances ranging from from 0 to 110 km the maximum acceleration recorded was 89 cm sec 2 from an m l 4 2 earthquake 15 8 km hypocentral distance from gvda the average amplification of the apparent seismic moment between 220 m depth and the surface is about 13 for over five orders of magnitude in the size of the recorded earthquakes the spectral ratio 0 220 of horizontal acceleration amplitude spectrum shows a mean amplification of about 10 for the frequency range of 2 0 to 30 hz for 17 events resonance peaks exist at about 1 7 3 0 and 12 0 hz where the spectral ratio 0 220 is nearly 40 analysis of the acceleration spectra of two specific earthquakes that have nearly the same hypocenter but with different magnitudes m 4 2 and 2 5 shows that the weathered granite zone beneath the soil strongly attenuates the spectral amplitudes for frequencies greater than 40 hz the impedance of the soil relative to the weathered granite amplifies all frequencies by about a factor of 3 leading to spectral levels that are greater at the surface than at 22 m depth near the top of the weathered granite the acceleration spectra at each depth show resonant peaks at the same frequencies the spectra at each depth are well correlated for both earthquakes the acceleration spectrum at 220 m is nearly constant for frequencies less than 60 hz which implies that there is little or no attenuation

deep water basins within the mesozoic carbonate platform of argolis greece in the past the classic argolis area of the central southern hellenides was interpreted as comprised of essentially in situ carbonate platforms and basins or alternatively of far travelled thrust sheets derived from a mesozoic ocean basin sited well to the east vardar ocean our fieldwork however demonstrates that at two key localities an important unit of middle triassic early jurassic deep water redeposited carbonates asklipion unit passes laterally into shallow water platform carbonates pantakrator unit the deep water limestones represent basins within the platform rather than far travelled thrust sheets while other slices of deep water limestone record a platform margin further east the basins originated during middle triassic ladinian rifting of the neotethys and are floored by extrusive rocks of intermediate composition highly condensed ammonitico rosso pelagic limestones accumulated on an inferred volcanic seamount during the mid late triassic anisian carnian the platforms slowly subsided in early jurassic time while the basins partly filled with redeposited carbonates adhami limestone shallow water carbonates locally transgressed the margins of the deeper water basins the platforms were submerged in the mid jurassic toarcian bathonian with the deposition of pink pelagic ammonitico rosso followed by marked subsidence and ribbon radiolarite deposition below the carbonate compensation depth e g koliaki chert in early late jurassic time kimmeridgian the area was regionally compressed eohellenic phase and the intraplatform basins founded on thinned continental crust were inverted and thrust up to several kilometres over the adjacent platform units the deformed continental margin then flexurally subsided ahead of emplacing jurassic ophiolites largely olistostromes migdhalitsa unit after taking account of up to 90 degrees clockwise palaeorotation of assumed neotectonic age kinematic indicators and facies trends suggest the ophiolite was derived from a pindos ocean basin originally sited to the west early cretaceous transgression resulted in the deposition of shallow water limestone and was followed by late cretaceous deep water limestone then terrigenous flysch accumulation in a foreland basin related to final suturing of the neotethyan ocean later the area was dissected by a series of mainly e w trending high angle neotectonic normal faults related to the aegean back arc extensional system

tectonostratigraphic evolution of the jurassic extensional basins of the eastern southern alps and adriatic foreland based on an integrated study of surface and subsurface data successions that characterize the eastern southern alps have been compared with coeval units drilled in the alpine foreland po and veneto plains northern adriatic sea the eastern southern alps are composed of a carbonate platform plateau drowned in the early jurassic trento platform and plateau a basin formed in the early jurassic belluno basin and a carbonate platform that lasted from the jurassic to the cretaceous friuli platform integration of stratigraphic and geophysical data illustrates the extensional architecture of the alpine foreland subsurface at the beginning of the jurassic peritidal successions were widespread everywhere except for the belluno basin a reorganization of the early jurassic paleogeography affected the southern alps around the sinemurian pliensbachian boundary the pliensbachian successions were deposited in the central western areas of the trento platform whereas elsewhere in the same platform and in the northern friuli platform pliensbachian units are missing replaced by an unconformity surface covered by crinoidal sands that have also been found in the subsurface the belluno basin is recognizable in seismic profiles under the veneto plain southward northern adriatic sea and po plain the basin between the trento and the friuli platforms here called the northern adriatic basin possesses a stratigraphy different from that of the belluno basin the northern adriatic basin drowned later and seismic profiles indicate that it was wider and bounded by groups of small synsedimentary faults instead of the major faults displacing the belluno basin the northern adriatic basin can be interpreted as the northeastern extension of the umbro marchean basin of central italy

extension and exhumation of the hellenic forearc ridge in kythera abstract detailed mapping and new structural observations on kythera demonstrate that there is a major detachment fault here termed the potamos detachment fault pdf exposed on the northern part of the island and bordering the domed structure of a metamorphic core complex the detachment forms the contact of contrasting metamorphic and nonmetamorphic units and both ductile and brittle structures are found related to its extensional development the earliest potamos mylonites as well as some other early ductile structures near the mapped detachment fault indicate initiation of the pdf under ne trending extension in mid to late miocene time later ductile ductile brittle and some brittle structures in the metamorphic unit near the detachment indicate in contrast a significant nw se extension along the forearc ridge the younger brittle structures indicate return to ne sw extension late miocene pliocene strata cover the detachment unconformably and are affected only by the late faults trench r

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

ground motion amplification in the marina district abstract following the 18 october 1989 loma prieta earthquake triggered seismographs were deployed in and around the marina district to investigate site amplification in the 3 weeks after the mainshock 16 aftershocks were recorded by two or more of these stations two additional stations deployed in march 1990 recorded three earthquakes that occurred in contra costa county by recasting the method of spectral ratios into a generalized inverse problem we combine the shear wave spectra from these 19 aftershocks to estimate the relative site amplification as a function of frequency all five stations located in the marina district are amplified by factors of 6 to 10 at 1 hz and 2 to 4 at 3 hz relative to a station located on franciscan sandstone at fort mason irrespective of whether they are sited on artificial fill or beach sand two stations located on dune sand just outside the marina district are amplified by factors of 2 to 4 for frequencies above 1 hz four stations located on franciscan sandstone in pacific heights nob hill rincon hill and diamond heights show little relative amplification conditional estimates of the mainshock spectra can be determined at stations that only recorded aftershocks if they can be linked to stations that recorded the mainshock these estimates are predicated on the assumption that the ground behaved linearly in the mainshock an assumption that is clearly violated for those sites where there was ground failure using this method of extrapolation for a site in the marina district that showed no evidence of ground failure yields mainshock spectra that are slightly greater than the mainshock spectra from the outer harbor wharf in oakland and near the pacific park plaza in emeryville and that significantly exceed the mainshock spectra from all the free field accelerograms located in san francisco

novel approach for health monitoring of earthen embankments abstractthis paper introduces a novel modular approach for the monitoring of desiccation induced deterioration in earthen embankments levees which are typically used as flood defense structures the approach is based on the use of a combination of geotechnical and noninvasive geophysical probes for the continuous monitoring of the water content in the ground the level of accuracy of the monitoring is adaptable to the available financial resources the proposed methodology was used and validated on a recently built 2 km long river embankment in galston scotland united kingdom a suite of geotechnical probes was installed to monitor the seasonal variation of water content over a 2 year period most devices were calibrated in situ a novel procedure to extrapolate the value of water content from the geotechnical and geophysical probes at any point of the embankment is shown desiccation fissuring degrades the resistance of embankments against several failure mechanisms an index of susceptibility is

three dimensional simulation of the near fault ground motion for the 1995 hyogo ken nanbu kobe japan earthquake abstract the 17 january 1995 hyogo ken nanbu earthquake is a typical example showing that the ground motions along basin edge faults can be very destructive in this study we simulate the near fault ground motion from this earthquake based on a kinematic fault model and a simplified 3d velocity structure of the kobe area the kinematic earthquake rupture and the wave propagation are modeled using a 3d finite difference method fdm our simulation identifies the basin edge effect as an important factor that influenced the ground motion amplification pattern in the kobe area we found that the coupling of the source directivity and basin edge effects causes impulsive ground motions with extremely high amplitude at periods greater than 1 sec and in a narrow zone offset less than 1 km from the basin edge the combination of these effects acted to create a fairly continuous band of amplification that extends about 30 km in an elongated zone parallel to the basin edge boundary in some areas localized site effects might have been as important as the abovementioned effects but they cannot explain the continuity of the extended east west zone of damage

determination of shallow shear wave velocity profiles in the cologne germany area using ambient vibrations summary we have used both single station and array methods to determine shallow shear velocity site profiles in the vicinity of the city of cologne germany from ambient vibration records based on fk analysis we assume that fundamental mode rayleigh waves dominate the analysed wavefield in the frequency range of 0 7 2 2 hz according to this view a close relation exists between h v spectral ratios and the ellipticity of the contributing rayleigh waves the inversion of the shape of h v spectral ratios then provides quantitative information concerning the local shear wave velocity structure however based on tests with synthetic data believed to represent a typical situation in the lower rhine embayment dispersion curves were found to provide stronger constraints on the absolute values of the velocity depth model than the ellipticities the shape of the ellipticities was found to be subject to a strong trade off between the layer thickness and the average layer velocity we have made use of this observation by combining the inversion schemes for dispersion curves and ellipticities such that the velocity depth dependence is essentially constrained by the dispersion curves while the layer thickness is constrained by the ellipticities in order to test this method in practice we have used array recordings of ambient vibrations from three sites where the subsurface geology is fairly well known and geotechnical information is at least partially available in order to keep the parameter space as simple as possible we attempted to fit only a single layer over a half space model however owing to earlier studies from the region we assume a power law depth dependence for sediment velocities for all three sites investigated the inversion resulted in models for which the shear wave velocity within the sediment layer both in absolute value at the surface and in depth dependence are found to be remarkably similar to the results obtained by budny from downhole measurements this is strong support for the interpretation of h v spectral ratios as rayleigh wave ellipticities for all three sites the predicted sh wave site amplification factors at the fundamental frequency are of the order of 5 6 with a slightly smaller value south of cologne

shallow slides in compacted high plasticity clay slopes shallow slide failures in embankments constructed of high plasticity clays create costly maintenance problems on highway projects and can threaten the integrity of water retaining earth structures this paper investigates the mechanisms of stability degradation that lead to these slope failures the failure mechanism involves moisture infiltration into the slope surface that leads to decreases in suction and soil shear strength both the degree and time rate of strength loss are investigated based on stability and moisture diffusion analyses respectively stability analyses indicate that the failures are associated with destabilizing hydraulic gradients in the pore water and the suction level at the surface of the slope declines to a limiting suction of about u 2 pf when exposed to moisture moisture diffusion analyses indicate that the time rate of strength degradation is controlled by the depth and spacing of desiccation cracks that form in the soil mass and the moisture diffusion properties of the soil the stability and moisture diffusion models described above were evaluated in light of 34 documented shallow slides in texas high plasticity clays

sedimentary evidence from the south mediterranean region sicily crete peloponnese evia used to test alternative models for the regional tectonic setting of tethys during late palaeozoic early mesozoic time

gravity tectonics driven by quaternary uplift in the northern apennines insights from the la spezia reggio emilia geo transect abstract the neotectonics of the northern apennines is illustrated using a crustal scale geoseismic cross section based on seismic profiles and field mapping the geological profile crosses a variety of tectonic settings from the val di vara and val magra vv vm grabens in the inner side of the apennines to the pede apennine thrust fronts ptf and finally to the external fronts of the apennines both the vv vm extensional system and the ptf show evidence of early pleistocene tectonic activity whereas thrusting in the external apennine ended by late pliocene the sole decollement of the external thrusts cuts down westwards into the basement to a depth of about 15 km whereas the ptf joins a shallower detachment surface that follows the top of the basement this basal surface also represents the basal detachment of the vv vm extensional system with the vv vm and ptf defining a large scale gravitational spreading system we hypothesise that the regional quaternary uplift that affected the internal sector of the apennines promoted a gravitational spreading in the upper part of the orogenic wedge accounting for the coeval extension in the vv vm and shortening at the ptf and applicable to a 100 km long sector of the northern apennines