geometry of ripples and dunes a kinematic theory for lower regime bedform shape is presented and examined in the light of extensive bedform data observed in large prototype channels depending upon the extent of bedform maturity the theory predicts uniquely defined nondimensional shapes for upstream faces these shapes are borne reasonably well by the observed data in spite of large variation in bedform size the length of upstream face relative to the wavelength is randomly distributed with most probable value of 0 614 which is close to the value 0 667 predicted by the theory for mature ripples and dunes

modeling offset dependent reflectivity for time lapse monitoring of water flood production in thin layered reservoirs the objective of this case study is to predict whether 5 years of water flood production from a thinly layered gulf of mexico reservoir will change its seismic amplitude variation with offset avo response in a detectable manner density and velocity profiles were computed from in situ wireline logs for 100 oil gas and brine saturations and for a 5 year prediction that was based on a fluid flow and production simulation analytical avo curves for simple half space models did not match avo curves extracted from synthetic seismograms computed with a full waveform layer stack algorithm several different amplitude corrections were tried to reduce the avo curves from the synthetic data to the analytical ones but ultimately none was deemed satisfactory instead avo change attributes based on relative changes polarity changes or ratios were used attributes based on the change of avo gradient were perceived to be most diagnostic of the water flood but they were also overly sensitive to interference noise and amplitude correction errors for field data from the study area a large decrease in intercept magnitude may be the best indicator of the waterfront

fault generated mountain fronts in the central apennines central italy geomorphological features and seismotectonic implications the morphotectonic framework of the central apennines is given by faulted blocks bounded by normal faults mostly trending nw se nnw sse and ne sw which cut previous compressive structures such a structural setting is consistent with the lbcal mechanisms of the earthquakes which often occur in this area in this paper three lithologically different normal fault generated mountain fronts are analysed in order to assess the relations between their geomorphic features and active tectonics they border the norcia depression sibillini mts umbria the amatrice ampotosto plateau laga mts lazio and the fucino basin marsica mts abruzzi the norcia depression is bounded by a n20 w trending normal fault to the east and by a parallel antithetic fault to the west the main fault has a 1000 m throw and gives rise to a wide fault escarpment characterized by l sharp slope breaks due to low angle gravity faults 2 important paleolandslides and 3 several fault scarplets on the piedmont belt affecting quaternary deposits the amatrice ampotosto plateau is delimited by the western slope of mt gorzano which runs along a n20 w trending normal fault having a 1500m throw minor parallel faults dislocate quaternary landforms large scale massmovements also occur here e the fucino basin was struck by th e 1915 avezzano earthquake 0 xi mcs which produced extensive surface faulting along two parallel nw trending normal fault escarpments on the eastern border of the basin there is paleoseismrc evidence including buried gravity graben in late glacial gravels and tectonic dip slip striations on holocene calcitic crusts covering bedrock normal fault planes these data suggest that active extensional tectonics plays a major role in the slope morphogenesis of the central apennines and they indicate the importance of geomorphic analysis in seismic zonation of this area

site amplifications observed in the gubbio basin central italy hints for lateral propagation effects abstract in this study we investigate the site amplification effects observed in the gubbio plain central italy the recordings of 140 local earthquakes 1 2 ml 4 7 observed by two linear arrays installed along the longitudinal and perpendicular basin axis are analyzed both in the time and frequency domains to determine the spatial variation of the local site effects in the basin the time series recorded in the gubbio plain are characterized by locally generated surface waves which cause a significant increase in both ground motion duration and amplitude with respect to a nearby reference station on a rock site in the middle of the basin where the sedimentary cover is thickest ca 600 m the peak ground velocity is amplified on average by a factor of 5 with respect to the reference station installed on rock and the duration is increased by a factor of about 2 the analyses in the frequency domain show that the spectral energy of the basin generated waves is mainly distributed over the range 0 4 2 hz and affects both horizontal and vertical components the site responses estimated by applying two reference site methods show that the overall shape of the amplification functions is similar for the sites located inside the basin with a difference in the amplification levels which can reach values as high as 30 in the middle of the valley amplifications up to a factor of 10 affect the vertical component of ground motion over a broad frequency range for nearly all basin sites with the maximum amplifications occurring at around 1 hz finally although the horizontal to vertical spectral ratios were found to provide a reliable estimation of the fundamental resonance frequency of the site they fail to estimate the shape of the site transfer function

building a three dimensional model of the active plio quaternary basin of argostoli cephalonia island greece an integrated geophysical and geological approach abstract this work is a multidisciplinary approach from geological and geophysical surveys to build a 3d geological model of argostoli basin cephalonia island greece aiming to be used for computational 3d simulation of seismic motion cephalonia island is located at the north western end of the aegean subduction frontal thrust that is linked to the dextral cephalonia transform fault west of cephalonia where the seismic hazard is high in terms of earthquake frequency and magnitude the plio quaternary koutavos argostoli basin site was selected within the french research agency pia sinaps project www institut seism fr projets sinaps last accessed on november 25th 2019 to host a vertical accelerometer array the long term goal is to validate three dimensional nonlinear numerical simulation codes to assess the site specific amplification and nonlinearity herein the geological and geophysical surveys carried out from 2011 to 2017 are presented and in particular the complementary investigations that led to the identification of the main stratigraphic units and their structures in addition coral debris sampled from the vertical array deep borehole cores were used for 230th 234u measurements which confirmed the pleistocene age of the koutavos basin the characterization of the three dimensional structure of the stratigraphic units was achieved by coupling geological cross sections i e depth geometry and geophysical surveys based of surface wave analysis

numerical simulations of glacial valley longitudinal profile evolution glaciers shape alpine landscapes they broaden valley bottoms enhance local valley relief generate multiple steps overdeepen valley floors and cause tributary valleys to hang these distinctive glacial signatures result from 10 4 10 5 yr of erosion during which swings in climate drive advances and retreats of alpine glaciers we use a numerical model of glacial erosion to explore the development of the longitudinal profiles of glaciated valleys the model is driven by the past 400 k y of variable climate because both sliding speed which dictates abrasion rate and water pressure fluctuations which strongly modulate quarrying rate should peak at the equilibrium line altitude ela we expect the locus of most rapid erosion to follow the transient ela simulations of a single glacial valley show rapid flattening of the longitudinal profile inclusion of a tributary glacier creates a step immediately downvalley of the tributary junction that persists over multiple glaciations and commonly leaves the tributary valley hanging steps and overdeepenings result from an increase in ice discharge immediately below the tributary junction which is accommodated primarily by increased ice thickness and hence sliding rate the size of the step increases with the ratio of tributary to trunk ice discharge while the height of a hanging valley reflects the difference in the time integrated ice discharge in tributary and trunk valleys and therefore increases as the discharge ratio decreases

unique problems associated with seismic analysis of partially gas saturated unconsolidated sediments abstract gas hydrate stability conditions restrict the occurrence of gas hydrate to unconsolidated and high water content sediments at shallow depths because of these host sediments properties seismic and well log data acquired for the detection of free gas and associated gas hydrate bearing sediments often require nonconventional analysis for example a conventional method of identifying free gas using the compressional shear wave velocity v p v s ratio at the logging frequency will not work unless the free gas saturations are more than about 40 the p wave velocity dispersion of partially gas saturated sediments causes a problem in interpreting well log velocities and seismic data using the white j e 1975 computed seismic speeds and attenuation in rocks with partial gas saturation geophysics 40 224 232 model for partially gas saturated sediments the difference between well log and seismic velocities can be reconciled the inclusion of p wave velocity dispersion in interpreting well log data is therefore essential to identify free gas and to tie surface seismic data to synthetic seismograms

shear wave velocity and attenuation structure of ischia island using broad band seismic noise records abstract in volcanic areas accurate localization of earthquakes requires detailed velocity and possibly attenuation models taking into account wide lithological variability and high geothermal gradients ischia island campania region italy is a seismically active volcano recently affected by a mw 3 9 event casamicciola august 21 2017 1 km depth due to the lack of a specific velocity model the earthquakes occurred on the island were localized using the one developed for the nearby campi flegrei caldera the aim of this work is the definition of a mean representative 1d shear wave velocity vs and attenuation q model of the shallower crust up to 2 km depth of ischia seismic noise array and spectral ratios techniques were applied to broad band seismic signals recorded by temporary and permanent networks updated after the august 2017 earthquake the values of both shear wave velocity vs and quality factor q are realistic with q values comparable with those obtained for campi flegrei and stromboli volcanic areas by taking into account stratigraphic information from deep wells and ultrasonic measurements of velocity on granite and trachytic lava samples a geological interpretation of the resulting velocity model is provided such a model can have significant implications for understanding the dynamics of a volcano mainly those leading to seismic activity

local site effects on weak and strong ground motion abstract this is a review of the current state of the art in characterizing effects of local geology on ground motion a new horizon is clear in this aspect of strong motion studies non linear amplification at sediment sites appears to be more pervasive than seismologists used to think several recent observations about the weak motion and the strong motion suggest that the non linear amplification at sediment sites may be very common first on average the amplification is always greater at the younger sediment sites for all frequencies up to 12 hz in the case of weak motion while the relation is reversed for frequencies higher than 5 hz in the case of strong motion secondly the application of the amplification factor determined from weak motion overestimates significantly the strong motion at sediment sites observed during the loma prieta earthquake within the epicentral distance of about 50 km thirdly the variance of peak ground acceleration around the mean curve decreases with the increasing earthquake magnitude finally the above non linear effects are expected from geotechnical studies both in the magnitude of departure from the linear prediction and in the threshold acceleration level beyond which the non linearity begins

extensional basins in the tectonically bimodal central apennines fold thrust belt italy response to corner flow above a subducting slab in retrograde motion the apennines fold thrust belt has developed over the past 20 m y in response to southeastward retrograde migration of the adriatic trench in a region of ongoing subduction but little plate convergence the orogenic belt is characterized by a gently sloping southwestern flank in a state of regional extensional collapse and a steeply sloping northeastern flank in regional contraction in any given area in the central apennines the chronologies of thrusting and subsequent extension provide an estimate of the time required for attainment of high elevation 2 5 3 0 km the time between initial extension and eruption of local ultramafic lavas provides an estimate of the time required to collapse by regional crustal thinning these estimates suggest that the northeastern contractional flank of the range is rising at least twice as fast as the southwestern flank is collapsing we propose that the bimodal state of stress in the apennines is maintained by corner flow in the mantle wedge beneath the crest of the range

structural styles chronology rates of deformation and time space relationships in the umbria marche thrust system central apennines italy structural interpretation of geological and geophysical data available for the central apennines italy allowed us to draw balance and restore three geological profiles across the external zones of the umbria marche thrust system and to evaluate the timing and rates of deformation in a roughly 4 ma time window from late messinian to late pleistocene time from this data set we established a general correlation between spacing l and thickness d of the thrust sheets which was used as a depth correction factor for deriving local versus regional depths to the sole thrust and a time space relationship between the closing time of activity of each thrust and the distance x from a reference point within the system

analytical study on steepness of ripples and dunes the mechanics of the limiting equilibrium profiles of ripples and dunes are presented the analysis is based on low sediment transport rates in which the sediment essentially moves as bedload the sediment transport rate is taken as proportional to some power m of the local velocity a two dimensional flow is assumed in which velocities are computed on the basis of a discontinuous potential flow model and on the basis of an incompressible rotational inviscid flow model a family of curves representing the relationship between the limiting steepness of bedforms and the relative depth of flow for various values of m is presented the analytical results are compared with the observed data and the comparison shows a fair agreement

characterization of shallow geology by high frequency seismic noise tomography summary to study the applicability of the passive seismic interferometry technique to near surface geological studies seismic noise recordings from a small scale 2 d array of seismic stations were performed in the test site of nauen germany rayleigh wave green s functions were estimated for different frequencies a tomographic inversion of the traveltimes estimated for each frequency from the green s functions is then performed allowing the laterally varying 3 d surface wave velocity structure below the array to be retrieved at engineering geotechnical scales furthermore a 2 d s wave velocity cross section is obtained by combining 1 d velocity structures derived from the inversion of the dispersion curves extracted at several points along a profile where other geophysical analyses were performed it is shown that the cross section from passive seismic interferometry provides a clear image of the local structural heterogeneities that are in excellent agreement with georadar and geoelectrical results such findings indicate that the interferometry analysis of seismic noise is potentially of great interest for deriving the shallow 3 d velocity structure in urban areas

extrapolation of irregular subsurface structures using the horizontal to vertical spectral ratio of long period microtremors one of the key problems in modeling the 3d subsurface structure of sedimentary basins is extrapolation and or interpolation from 2d models constructed from reflection and refraction surveys the use of microtremor horizontal to vertical h v spectral ratios allowing simple and quick microtremor measurements may be suitable for this purpose the validity and usefulness of long period microtremor h v spectral ratios are investigated as a possible tool for extrapolation in 3d basin structure modeling three component microtremor observations were conducted at 51 stations in the northern section of the osaka basin which encompasses the most complex geological structures in the basin the microtremor h v spectral ratios were measured in the range 1 to 5 sec to reproduce these observations three 2d finite element models have been developed that account for the irregular shape of subsurface structures deduced from seismic reflection studies microtremor array studies and deep drilling data the 3d model obtained by combining the 2d models is consistent with geological information for the area such as surface geology and the location of active faults furthermore compared with the basement structure derived from the gravity prospecting this 3d model is more detailed and offers higher resolution than the gravitational method therefore the microtremor h v spectral ratio represents a useful technique of extrapolation and interpolation for modeling 3d basin structures

identifying 2d resonance in microtremor wave fields to predict local site effects during earthquakes we must know the geometrical and mechanical properties of local sedimentary structures and their resonance behavior we present a concept to identify resonance modes for 2d structures this is done for synthetic as well as measured microtremor wave fields the microtremor data were investigated by using the reference station and horizontal to vertical h v methods analyzing the synthetic microtremor data in profiles across 2d structures the reference station method rsm turned out to be much more suitable for the detection of 2d resonances than the h v method we therefore focused on rsm when analyzing the measurement data from two test sites in switzerland the st jakob tullingen trough near basel in the north and a site in the rhone valley near the village vetroz in the south the results of these two test sites led to different conclusions whereas the spectral peaks in data of the st jakob tullingen trough were not well developed and could only tentatively be interpreted those from the rhone valley clearly exhibited 2d resonance effects the sh 00 and the sv fundamental mode could be successfully identified at 0 32 0 03 and 0 35 0 03 hz respectively

geometry and evolution of a fault controlled quaternary basin by means of tdem and single station ambient vibration surveys the example of the 2009 l aquila earthquake area central italy we applied a joint survey approach integrating time domain electromagnetic soundings and single station ambient vibration surveys in the middle aterno valley mav an intermontane basin in central italy and the locus of the 2009 l aquila earthquake by imaging the buried interface between the infilling deposits and the top of the pre quaternary bedrock we reveal the 3 d basin geometry and gain insights into the long term basin evolution we reconstruct a complex subsurface architecture characterized by three main depocenters separated by thresholds basin infill thickness varies from 200 300 m in the north to more than 450 m to the southeast our subsurface model suggests a strong structural control on the architecture of the basin and highlights that the mav experienced considerable modifications in its architecture over time the buried shape of the mav suggests a recent and still ongoing predominant tectonic control by the nw se trending paganica san demetrio fault system psdfs which cross cuts older ca ene and nne trending extensional faults furthermore we postulate that the present day arrangement of the psdfs is the result of the linkage of two previously isolated fault segments we provide constraints on the location of the southeastern boundary of the psdfs defining an overall 19 km long fault system this allows for earthquakes larger than m6 5 this study emphasizes the benefit of combining two easily deployable geophysical methods for reconstructing the 3 d geometry of a tectonically controlled basin our joint approach provided us with a consistent match between these two independent estimations of the basin substratum depth within 15

geometry segmentation pattern and displacement variations along a major apennine thrust zone central italy abstract hundreds of kilometres long arc shaped continuous thrust faults commonly imply very large displacements by detachment dominated thrusting therefore their occurrence has a large impact on fold thrust belt structure one of the major thrust faults of the central northern apennines the umbria marche sabina thrust zone is traditionally believed to represent one such feature characterised by displacements of several tens of kilometres however detailed studies of this structure revealed that it is actually composed of a series of partially overlapping fault segments rather than consisting of a single continuous thrust cross section balancing and restoration carried out by the integration of surface geological data with available sub surface information points out relatively limited amounts of thrust displacement

passive seismic imaging with directive ambient noise application to surface waves and the san andreas fault in parkfield ca summary this study deals with surface waves extracted from microseismic noise in the 0 1 0 2 hz frequency band with passive seismic correlation techniques for directive noise we explore the concept of passive seismic noise tomography performed on three component sensors from a dense seismic network from the nine component correlation tensor a rotation algorithm is introduced that forces each station pair to re align in the noise direction a necessary condition to extract unbiased traveltime from passive seismic processing after rotation is performed the new correlation tensor exhibits a surface wave tensor from which rayleigh and love waves can be separately extracted for tomography inversion methodological aspects are presented and illustrated with group speed maps for rayleigh and love waves and ellipticity measurements made on the san andreas fault in the parkfield area california usa

surface faulting in norcia central italy a paleoseismological perspective we carried out paleoseismological analyses in norcia one of the oldest town of central italy four trenches were dug in late pleistocene holocene deposits across an unmapped antithetic splay of the norcia fault system the investigated fault runs through the recent settlement of the town brushing against the middle age city walls we found evidence of repeated surface ruptures in the past 20 ky the last one dated to a period fitting with the 1703 ad catastrophic earthquake m 6 8 our data i show definitively the late pleistocene holocene activity of the norcia fault system ii strengthen the historical accounts describing surface ruptures during the 1703 event in norcia iii cast light on the seismogenic behavior of the 70 km long fault system between l aquila and norcia central italy and iv predict the occurrence of normal surface faulting inside the municipality of norcia during future mz6 earthquakes d 2005 elsevier b v all rights reserved

high resolution field mapping and analysis of the august october 2016 coseismic surface faulting central italy earthquakes slip distribution parameterization and comparison with global earthquakes

insights into bedrock paleomorphology and linear dynamic soil properties of the cassino intermontane basin central italy abstract seismic amplifications are dictated by the depth of the bedrock and the stratigraphy and dynamic properties of the soil deposits quantifying these properties together with their uncertainty is a necessary task to perform a reliable assessment of the seismic risk at an urban scale in this paper a multidisciplinary analysis is presented where information of different nature is combined borehole logs geophysical geological and geotechnical surveys are interpreted with the aid of analytical numerical and geostatistical techniques to characterise the complex shape of the bedrock and the linear dynamic properties of the sedimentary deposits filling the cassino basin a quaternary intermontane basin located in central italy the regional and local seismic hazard is firstly identified with geological surveys that reveal an active seismogenic fault capable of producing earthquakes with estimated magnitudes up to 6 7 6 8 boreholes reaching depths variable up to a maximum of 180 m and microtremor measurements revealing the sharp impedance contrast at the transition between the sedimentary arenaceous bedrock and the soft quaternary infilling are combined to identify the depth of the bedrock and the linear dynamic properties of soil deposits these are one of the key factors governing the propagation to the ground level of seismic waves and their assessment represents the first step for the seismic hazard characterisation of the plain

low shear velocity in a normal fault system imaged by ambient noise cross correlation the case of the irpinia fault zone southern italy we extracted the green s functions from cross correlation of ambient noise recorded at broadband stations located across the apennine belt southern italy continuous records at 26 seismic stations acquired for 3 years were analyzed we found the emergence of surface waves in the whole range of the investigated distances 10 140 km with energy confined in the frequency band 0 04 0 09 hz this phase reproduces rayleigh waves generated by earthquakes in the same frequency range arrival time of rayleigh waves was picked at all the couples of stations to obtain the average group velocity along the path connecting the two stations the picks were inverted in separated frequency bands to get group velocity maps then used to obtain an s wave velocity model penetration depth of the model ranges between 12 and 25 km depending on the velocity values and on the depth of the interfaces here associated to strong velocity gradients we found a low velocity anomaly in the region bounded by the two main faults that generated the 1980 m 6 9 irpinia earthquake a second anomaly was retrieved in the southeast part of the region and can be ascribed to a reminiscence of the adria slab under the apennine chain

seismic site characterization of an urban sedimentary basin livermore valley california site response basin edge induced surface waves and 3d simulations thirty two accelerometers were deployed in the livermore valley california for approximately one year to study sedimentary basin effects many local and near regional earthquakes were recorded including the 24 august 2014 m w 6 0 napa california earthquake the resulting ground motion data set is used to quantify the seismic response of the livermore basin a major structural depression in the california coast range province bounded by active faults site response is calculated by two methods the reference site spectral ratio method and a source site spectral inversion method longer period 1 s amplification factors follow the same general pattern as bouguer gravity anomaly contours site response spectra are inverted for shallow shear wave velocity profiles which are consistent with independent information frequency wavenumber analysis is used to analyze plane wave propagation across the livermore valley and to identify basin edge induced surface waves with back azimuths different from the source back azimuth finite element simulations in a 3d velocity model of the region illustrate the generation of basin edge induced surface waves and point out strips of elevated ground velocities along the margins of the basin online material figures comparing 5 damped acceleration response spectra for data and synthetics

bed form geometry in sand bed flows a new method is proposed for predicting relative bed form height h d in sand bed flows the proposed method is based on the concept of relating energy loss due to form drag to the head loss across a sudden expansion in open channel flows a unique feature of the proposed method is that it can be applied to various bed forms i e ripples dunes antidunes standing waves and transitional bed regimes that occur in alluvial flows the relation thus developed was applied to a large number 251 flows 14 different data sets of laboratory and river data and was found to give good agreement with the observed h d values in a comparison of prediction accuracies with seven existing relationships the proposed method was found to give significantly better agreements with the observed data future improvements in the prediction of h d will depend on improved formulations of the two parameters incorporated in the present relation i e energy loss coefficient k and the relative bed form length l d for various b

holocene paleoseismology of the norcia fault system central italy abstract we investigated the late quaternary activity of the norcia fault system one of the most hazardous seismogenic structures of italy responsible over the centuries for nucleating several mw 6 earthquakes possibly up to mw 6 9 as on 14th january 1703 this fault is located only 10 km away from the mount vettore fault system which was responsible for the deadly mw 6 6 central italy earthquake in 2016 using evidence gathered from ten paleoseismological trenches we reconstructed the history of the strongest earthquakes sourced by the norcia faults during the past 4 ky and in previous time windows back to 20 ka in particular we found indications of the historical 1703 and 99 bce events as well as a previously unknown one in the bronze age we also obtained a robust estimate of the slip rate for the post last glacial maximum period 1 0 2 mm yr and a rough 1 8 ky recurrence time for mw 6 9 events during the late holocene

1 d and 2 d resonances in an alpine valley identified from ambient noise measurements and 3 d modelling summary h v spectral ratios are regularly used for estimating the bedrock depth in 1 d like basins exhibiting smooth lateral variations in the case of 2 d or 3 d pronounced geometries observational and numerical studies have shown that h v curves exhibit peculiar shapes and that the h v frequency generally overestimates 1 d theoretical resonance frequency to investigate the capabilities of the h v method in complex structures a detailed comparison between measured and 3 d simulated ambient vibrations was performed in the small size lower romanche valley french alps which shows significant variations in geometry downstream and upstream the sechilienne basin analysing the h v curve characteristics two different wave propagation modes were identified along the valley relying on previous geophysical investigation a power law relationship was derived between the bedrock depth and the h v peak frequency which was used for building a 3 d model of the valley geometry simulated and experimental h v curves were found to exhibit quite similar features in terms of curve shape and peak frequency values validating the 3 d structure this good agreement also evidenced two different propagation modes in the valley 2 d resonance in the sechilienne basin and 1 d resonance in the external parts this study underlines the interest of h v curves for investigating complex basin structures

the impact of common offset migration on porosity estimation by avo inversion the impact of prestack time migration on porosity estimation has been tested on a 2 d seismic line from the valhall hod area in the north sea porosity is estimated in the cretaceous chalk section in a two step procedure first p wave and s wave velocity and density are estimated by amplitude variation with offset avo inversion these parameters are then linked to porosity through a petrophysical rock data base based on core plug analysis the porosity is estimated both from unmigrated and prestack migrated seismic data for the migrated data set a standard prestack kirchhoff time migration is used followed by simple angle and amplitude corrections compared to modern high cost true amplitude migration methods this approach is faster and more practical the test line is structurally fairly simple with a maximum dip of 5 but the results differ significantly depending on whether migration is applied prior to the inversion the maximum difference in estimated porosity is of the order of 10 about

quaternary basin evolution and present tectonic regime in the area of the 1997 1998 umbria marche seismic sequence central italy abstract geological and geomorphological surveys have been performed in the area affected by the 1997 1998 umbria marche seismic sequence m max 6 0 aimed at defining the quaternary tectonic history and the characteristics of the present tectonic regime data have been collected from 1 the analysis of the remnant landsurfaces by means of aerial photos and field surveys 2 geological surveys in the cesi san martino basin and in the easternmost sector of the colfiorito basin in order to identify deformative features affecting the quaternary deposits 3 the analysis of boreholes and geo electrical data derived from previous surveys performed in the 1960s in order to reconstruct the top of the pre quaternary substratum in the colfiorito basin two different successions of remnant landsurfaces have been identified along the faults bounding the basins to the east in the hangingwall and the footwall respectively the difference accounts for a fault controlled evolution of the landscape at least during the upper pliocene early pleistocene the deformation affecting the quaternary deposits and landforms in the investigated basins indicates a decreasing tectonic activity along the master faults since the middle pleistocene surface deformation due to tectonics is faint and displayed by gentle warping of the landforms during the late quaternary as for the basin geometry subsurface data show that two minor depressions formed in the colfiorito basin during the quaternary the oldest one close to the fault bounding the basin while the youngest and deepest formed in the inner portion of the basin therefore the present geometry is different from that of other fault bounded quaternary depressions of the central apennines typically half graben basins showing the maximum depth of the substratum in the area close to the master fault tectonic history may be summarised as follows 1 origin of the quaternary fault bounded colfiorito and cesi san martino basins 2 evolution of the basins with a half graben style 3 significant reduction of tectonic activity since the middle pleistocene during the third phase the evolution of the basins is no longer related to a half graben style in the case of the colfiorito basin a new depression is superimposed to on the previous half graben whose evolution is related to the lowering of the inner portion of the basin through warping moreover present activity does not result in fault related surficial displacements but only in continuous deformation spread over the basins these conclusions have fundamental implications for the seismotectonic framework of the 1997 1998 earthquake sequence this deformation style is indeed in agreement with the coseismic deformation modelled by means of the sar interferometry analyses carried out by other institutions during the seismic sequence and with the lack of evident surface faulting related to the mentioned events in the investigated area this evidence indicates that the evolution of the investigated area since the middle pleistocene resulted from the summation of deformative episodes similar to that which occurred during the recent seismic sequence as a consequence no earthquakes with magnitude larger than 6 are expected in the area

surface wave dispersion measurements from ambient seismic noise analysis in italy summary we present the surface wave dispersion results of the application of the ambient noise method to broad band data recorded at 114 stations from the istituto nazionale di geofisica e vulcanologia ingv national broad band network some stations of the mediterranean very broadband seismographic network mednet and of the austrian central institute for meteorology and geodynamics zamg vertical component ambient noise data from 2005 october to 2007 march have been cross correlated for station pairs to estimate fundamental mode rayleigh wave green s functions cross correlations are calculated in 1 hr segments stacked over periods varying between 3 months and 1 5 yr rayleigh wave group dispersion curves at periods from 8 to 44 s were determined using the multiple filter analysis technique the study region was divided into a 0 2 0 2 grid to invert for group velocity distributions checkerboard tests were first carried out and the lateral resolution was estimated to be about 0 6 the resulting group velocity maps from 8 to 36 s show the significant difference of the crustal structure and good correlations with known geological and tectonic features in the study region the po plain and the southern alps evidence lower group velocities due to soft alluvial deposits and thick terrigenous sediments our results also clearly showed that the tyrrhenian sea is characterized with much higher velocities below 8 km than the italian peninsula and the adriatic sea which indicates a thin oceanic crust beneath the tyrrhenian sea

spectral amplification in a sediment filled valley exhibiting clear basin edge induced waves various site response estimates are presented for a linear array deployed in the coachella valley california during the 1992 landers big bear aftershock sequence this systematic comparison is unique in that the response of the site is clearly dominated by basin edge induced waves average sediment to bedrock spectral ratios for long s wave windows which include the basin edge induced waves exhibit amplification factors as high as 18 below 7 hz the deep basin structure which gives rise to the obvious multi dimensional effects produces a fundamental resonant peak that shifts between basin sites from 0 23 to 0 48 hz as the depth to bedrock changes above 0 6 hz where the largest amplifications occur the response is remarkably similar between sites and appears to be dominated by a near surface layer that is relatively uniform across the valley the apparent fundamental resonant frequency of this layer is between 0 8 and 1 hz sediment to bedrock spectral ratios computed using shorter windows that exclude the basin edge induced waves imply that the multi dimensional effects are significant only below 4 hz where they increase amplifications by an approximate factor of 2 spectral ratios computed using coda windows taken at twice the s wave travel time exhibit amplifications that are an average factor of 1 7 greater between 1 and 4 hz than those of the s wave estimates this discrepancy does not improve by taking coda windows later at four times the s wave travel time horizontal to vertical component s wave spectral ratios do not agree with the sediment to bedrock ratios however they do exhibit a clear peak at the fundamental resonant frequency of the deep basin structure sediment to bedrock spectral ratios of ambient seismic noise are also inconsistent with the s wave estimates however horizontal to vertical noise ratios exhibit clear peaks near the fundamental resonant frequencies of both the deep basin structure below 0 6 hz and the suspected near surface layer between 0 8 and 1 hz therefore ambient noise data appear to provide valuable constraints on the basin structure ongoing efforts involve multi dimensional modeling of the observed basin edge induced phases and resonant frequencies

investigation of the norcia basin central italy through ambient vibration measurements and geological surveys abstract during the 2016 2017 a seismic sequence struck the central italy involving four regions umbria marche abruzzo and lazio and causing important damages and victims in inhabited areas such as norcia and amatrice towns the strongest event of the seismic sequence was a mw 6 5 event with epicenter at about 5 km far from the norcia area which is an intermontane basin prone to ground motion amplification the historical town of norcia and the surrounding hamlets were recently investigated by the microzonation activity but information on the geometry and velocity are still partial considering the entire basin indeed past studies aimed at reconstructing the elastic and geometrical properties focusing mainly on the northern part of the basin specifically in this paper we integrated seismic and geological data to get a better knowledge of the properties of the quaternary norcia basin a geological survey was carried out to provide a geological map and three geological cross sections we analyzed new seismic ambient vibrations data collected by single seismic stations to infer the distribution of resonant frequency f0 for the entire basin we used passive arrays of seismic stations to better define the velocity profiles of the area in the northern part of the basin two 2d arrays with elliptical like shapes were deployed showing strong discrepancies of the elastic soil properties in proximity of norcia town we found shear wave velocities of the near surface profile of about 300 400 and 500 800 m s in presence of lacustrine and alluvial fan deposits respectively further the values of f0 are abruptly varying from 0 5 hz in the sw sector of norcia village up to 2 hz in its ne sector ambient vibration data reveal less pronounced variation of f0 in the southern part of the basin with resonant values that are almost in the range 1 1 3 hz in the southern sector a 1d array was arranged along a 5 km line and was analyzed by means of seismic noise cross correlation analysis suggesting the presence of a deeper seismic contrast the integration of geophysical and geological results has allowed to infer insights on the subsurface geometry of the basin

sediment convection diffusion and bedform length in connection with the mechanics of ripples and dunes the governing equations of convection diffusion of suspended sediment in two dimensional flow fields over ripples or dunes are solved by the finite element method the role of suspended sediment in determining the steady bedform length is theoretically investigated the postulate that in the case of steady bedforms the diffusive flux vector at any point on the stoss must point into the interior of the flow region divides mathematically acceptable solutions into two categories 1 physically acceptable solutions and 2 physically unacceptable solutions the marginal solutions which lie on the common boundary between the two classes in the solution space are of special interest they represent steady bedforms with minimum length under the prevailing flow conditions and they are conjectured to correspond to the steady bedforms occurring in nature finally the theory is compared with the physical observations made in flumes canals and rivers t

sedimentary structures sorby and the last decade henry clifton sorby pioneered in the last century the description and especially the hydrodynamic interpretation of sedimentary structures together with their use as palaeocurrent indicators research completed since the last syntheses were published a decade ago shows that work along these lines continues to be necessary and relevant particularly as regards the physical explanation of structures and to present significant challenges and opportunities perhaps the most pressing needs are for a better understanding of 1 bedforms in gravels silts and carbonate sediments 2 tidal and especially sand wave bedding 3 hummocky and swaley cross stratification and 4 soft sediment and dewatering structures in turbidites many sedimentary structures present a little exploited opportunity to quantify process rates and define short time periods from the rock record

s wave velocity profiling by joint inversion of microtremor dispersion curve and horizontal to vertical h v spectrum a joint inverse analysis using both microtremor dispersion curve and horizontal to vertical h v spectrum is proposed for estimating the s wave velocity vs profiles of subsurface soils in the inversion both microtremor dispersion and h v data are assumed to be the rayleigh wave dispersion curve and the surface both rayleigh and love wave h v spectrum that have been theoretically derived by taking into account the effects of their fundamental and higher modes the proposed joint inversion as well as the conventional one using dispersion data alone is per formed at four sites where shallow vs profiles down to engineering bedrock are available the vs profiles estimated by the proposed joint inversion are more con sistent with available down hole velocity logs than those by the conventional method in particular the proposed inversion shows significant improvement in estimating bedrock vs structures compared to the conventional inversion sensitivity analyses indicate that the surface wave h v ratio is sensitive to the bedrock vs structure more than the rayleigh wave phase velocity confirming that the proposed joint inversion including h v spectrum is promising

the effect of quaternary alluvium on strong ground motion in the coyote lake california earthquake of 1979 abstract the effect of alluvium on strong ground motion can be seen by comparing two strong motion records of the coyote lake california earthquake of 6 august 1979 m l 5 9 one record at a site on franciscan bedrock had a peak horizontal acceleration of 0 13 g and a peak horizontal velocity of 10 cm sec the other at a site 2 km distant on 180 meters of quaternary alluvium overlying franciscan had values of 0 26 g and 32 cm sec amplifications by factors of 2 and 3 horizontal motions computed at the alluvial site for a linear plane layered model based on measured p and s velocities show reasonably good agreement in shape with the observed motions but the observed peak amplitudes are greater by a factor of about 1 25 in acceleration and 1 8 in velocity about 15 per cent of the discrepancy in acceleration and 20 per cent in velocity can be attributed to the difference in source distance the remainder may represent focusing by refraction at a bedrock surface concave upward there is no clear evidence of nonlinear soil response fourier spectral ratios between motions observed on bedrock and alluvium show good agreement with ratios predicted from the linear model in particular the observed frequency of the fundamental peak in the amplification spectrum agrees with the computed value indicating that no significant nonlinearity occurs in the secant shear modulus computations show that nonlinear models are compatible with the data if values of the coefficient of dynamic shear strength in terms of vertical effective stress are in the range of 0 5 to 1 0 or greater the data illustrate that site amplification may be less a matter of resonance involving reinforcing multiple reflections and more the simple effect of the low near surface velocity application of traditional seismological theory leads to the conclusion that the site amplification for peak horizontal velocity is approximately proportional to the reciprocal of the square root of the product of density and shear wave velocity

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

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

sediment entrainment in channel with rippled bed an expression for the entrainment in a channel with rippled bed has been developed considering the entrainment mechanism the flow structure behind the ripple has been modeled on an eye shaped line vortex afterwards the pickup rate of the sediment particle and its motion has been calculated under the vortex activity the ripple characteristics such as configuration frequency of formation and the shear stress due to the vortex on the sand surface have been obtained as functions of the bulk parameters combining these characteristics the entrainment rate at the lee side of the ripple has been calculated also the entrainment rate from the stoss side has been taken as a basis for the calculations concerned with the total entrainment rate then the ratio of the lee side entrainment to the total value has been obtained as a function of the ripple characteristics described above it can be concluded that the results have been found to be satisfactory when compared with former investigations and experim

real time monitoring of relative velocity changes using ambient seismic noise at the piton de la fournaise volcano la reunion from january 2006 to june 2007 we present the results of a real time method based on coda wave interferometry from seismic noise cross correlation functions for relative seismic velocity variations monitoring on a volcanic edifice the ambient seismic noise at the piton de la fournaise volcano on la reunion island is analyzed from january 2006 to june 2007 during this period five eruptions occurred showing a great diversity in eruption duration intensity and eruptive fissure location two different methods are used to compute the velocity variations in order to compare their stability in quasi real time routine we compare the obtained velocity variations with the surface deformation observed by gps and extensometers networks this allows us to identify and quantify three major processes at the origin of seismic wave velocity variations in the edifice firstly the observed pre eruptive summit inflation is accompanied by a decrease in seismic velocity secondly the edifice deflation following the opening of an eruptive fissure is characterized by an increase of the velocity finally the summit caldera collapse generates a strong velocity drop coda wave interferometry from seismic noise cross correlation functions in quasi real time may allow us to forecast eruption and constrain the processes taking place in the volcanic plumbing system

geometry and structure of a fault bounded extensional basin by integrating geophysical surveys and seismic anisotropy across the 30 october 2016 mw 6 5 earthquake fault central italy the pian grande di castelluccio basin

spatial and temporal variations in growth rates along active normal fault systems an example from the lazio abruzzo apennines central italy abstract the geometry kinematics and rates of active extension in lazio abruzzo italian apennines have been measured in order to gain a better understanding of the spatial and temporal variations in fault growth rates and seismic hazards associated with active normal fault systems we present fault map traces throws throw rates and slip directions for 17 parallel en echelon or end on active normal faults whose 20 40 km lengths combine to form a soft linked fault array ca 155 km in length and ca 55 km across strike throw rates derived from observations of faulted late glacial features and holocene soils show that both maximum throw rates and throw rate gradients are greater on centrally located faults along the strike of the array total throws and throw gradients show similar spatial variations but with weaker relationships with distance along strike when summed across strike throw rates are increasingly high towards the centre of the array relative to summed throws we interpret the above to suggest that throw rates have changed in the recent past ca 0 7 ma from spatially random fault growth rates initiating at 2 5 3 3 ma to growth rates that are greater on centrally located faults we interpret this as evidence for fault interaction producing throw rate variations that drive throw profile readjustment on these crustal scale soft linked faults the results are used to discuss seismic hazards in the region which are quantified in a second paper in this issue

issues in rock physics and implications for dhi interpretation seismic techniques for direct hydrocarbon indication rely on the changes in seismic character which accompany changes in pore fluid content interpretation and modeling of direct hydrocarbon indicators dhis require an understanding of the factors affecting seismic velocities and reflection coefficients which are in turn dependent on pore fluid properties rock frame properties and fluid substitution within a given rock frame recent developments in rock physics have greatly increased our general understanding in these areas but have also revealed complications that require further research