laboratory investigation into off fault seismic activity abstract the off fault pattern of weak seismic activity which was observed in the laboratory around fault pairs with already generated tensile cracks led to the comparison with similar patterns observed in nature in some seismoactive regions on the basis of the results of the laboratory model experiments the off fault seismic activity can be attributed to fault segments oriented obliquely or roughly perpendicular to the main fault system these fault segments may have originated as tensile fractures during one of the foregoing strong earthquakes to study the off fault foreshock and aftershock occurrences a method of laboratory seismology physical modeling was employed the use of this method is based on the assumption that the obtained information on the seismic regime of fault models is relevant to the seismic manifestation of faults in the earth the results of laboratory experiments can thus be used to analyze the pattern of seismic energy release in selected seismoactive fault regions

potential of ambient seismic noise techniques to monitor the st gallen geothermal site switzerland the failures of two recent deep geothermal energy projects in switzerland basel 2006 st gallen 2013 have again highlighted that one of the key challenges for the successful development and operation of deep underground heat exchangers is to control the risk of inducing potentially hazardous seismic events in st gallen after an injection test and two acid injections that were accompanied by a small number of micro earthquakes ml 0 2 operators were surprised by an uncontrolled gas release from the formation gas kick the killing procedures that had to be initiated following standard drilling procedures led to a ml3 5 earthquake with ambient seismic noise cross correlations from nine stations we observe a significant loss of waveform coherence that we can horizontally and vertically constrain to the injection location of the fluid the loss of waveform coherence starts with the onset of the fluid injections 4 days prior to the gas kick we interpret the loss of coherence as a local perturbation of the medium we show how ambient seismic noise analysis can be used to assess the aseismic response of the subsurface to geomechanical well operations and how this method could have helped to recognize the unexpected reservoir dynamics at an earlier stage than the microseismic response alone allowed

fault interaction and seismicity laboratory investigation and its seismotectonic interpretation systems of two parallel linear faults of the same length with the angle of inclination 45 were investigated under uniaxial linearly increasing load perspex plates were used as models for each treated fault configuration the morphology of tensile cracks and the sequence of seismoacoustic events of shear and tensile origin were studied

seismic evidence of longitudinal extension in the southern apennines chain italy the 1997 1998 sannio matese seismic sequence 1 we present evidence of longitudinal extension in the apennines based on data from the 1997 1998 sannio matese seismic sequence the earthquakes occurred between the nw se faults responsible for larger historical earthquakes inversion of focal mechanisms indicates a stress field with a prevailing normal stress characterized by a nnw sse sub horizontal 3 this stress regime is consistent with normal movements along ne sw faults these features suggest that the ne sw faults located in between the nw se faults cannot be interpreted as transfer faults or old faults reactivated during the eastward migration of the chain we propose that the deformation due to the eastward chain migration concentrates along nw se normal faults which are responsible for the largest earthquakes whereas the deformation related to the chain curvature concentrates along ne sw normal faults which are responsible for the lower energy seismic sequences

spatial and temporal analysis of a seismic series using a new version of the three point method application to the 1989 antequera spain earthquakes abstract the three point method tpm has been successfully applied to several seismic series and has provided information about the spatial characteristics azimuth and dip of the fault planes activated in the rupture process a new development of the tpm to determine temporal characteristics is presented to obtain the evolution of the fracturing process of an active fault system for the analysis of the 158 microearthquakes and earthquakes that took place in the seismic series of antequera in june 1989 the choice of a threshold magnitude m u 2 5 has permitted the events related to the most relevant fractures to be distinguished secondly only the events between two concentric spheres here named spatial crown with respect to a given earthquake have been used in order to avoid taking into account earthquakes that are too close to each other together with the very distant events that have little relation to the event analysed the spatial crown has permitted some clear results in the antequera series where we have found that the fracturing process began fundamentally with n 80 e planes and evolved to n 65 w planes finally an error analysis enables an estimation of the uncertainty in the results to be obtained from the errors in the data

inversion for parameters of tensile earthquakes the tensile source model generalizes the shear source model by assuming that the slip vector can be arbitrarily oriented with respect to the fault and is not constrained to lie within the fault plane the proposed inversion for the parameters of tensile sources is based on the evaluation of the isotropic iso compensated linear vector dipole clvd and double couple dc components in seismic moment tensors the most significant parameters inverted are the ratio at the fault denoted as the parameter and the inclination of the slip vector from the fault the parameter is significant for discriminating noisy moment tensors of shear earthquakes from those of tensile earthquakes the inclination can be accurately determined from the dc component in the moment tensor because the dc component rapidly decreases with increasing for example the inclination of 20 causes dc being 50 60 only the inversion is applied to earthquakes which occurred in january 1997 in west bohemia czech republic it is shown that some of these earthquakes display tensile faulting the parameter is 0 1 the inclination of the slip from the fault attains values of up to 20 this inclination is a result of tensile traction and reduced shear traction along the fault and high fluid pressure in the region

distribution and characteristics of mixed transitional mid permian late artinskian ufimian marine faunas in asia and their palaeogeographical implications abstract the permian marine biogeography of the asian region is characterised by the development of three broad realms boreal tethyan and gondwanan in the early early permian asselian to early artinskian there seems to have existed sharp biogeographical boundaries with no transitional zones between the realms presumably due to the effect of gondwanan glaciation and sharp climatic zonation the mid permian late artinskian to ufimian of the asian region is distinguished by the rise of two broad transitional zones in which mixed marine faunas flourished the northern transitional zone north and northeast china sikhote alin central and northeast japan is characterised by an admixture of both warm water cathaysian and cold temperate boreal genera the southern transitional zone arabian peninsula iran afghanistan the karakorum southeast and central pamir salt range central and northwest tibet shan thai terrane timor and western irian jaya on the other hand is distinguished by incorporating faunal elements of both gondwanan and cathaysian origin the mixed faunas of both transitional zones share several antitropically distributed genera e g monodiexodina lytvolasma and spiriferella and are succeeded by palaeotropical tethyan faunas of late permian age it has been postulated that the mixed mid permian fauna of the northern transitional zone was probably formed in an epicontinental sea which was connected to both the asian tethys and the arctic which facilitated the migration of cathaysian and boreal forms into the epicontinental sea and subsequent faunal mixing the formation of the mixed faunas of the southern transitional zone on the other hand is probably related to the breaking off of the cimmerian blocks from northern gondwana and subsequent drifting into a lower latitudinal zone with geographical proximity to both gondwana and cathaysia during the mid permian

seismic ambient noise analysis in southern italy abstract we studied the ambient noise recorded at irpinia seismic network isnet a seismic network installed along the campania lucania apenninic chain southern italy with the aim of characterizing the noise spectrum for each station as a function of time and the detection threshold of the network for the latter purpose we proposed a mixed indirect approach based on the signal to noise ratio snr in the time domain with parameterization in the frequency domain the source signature is represented by the convolution of the brune source time function with the azimi attenuation curve we found that 1 3 is the minimum magnitude an event should have to be detected at least at five stations with an snr larger than five wherever it occurs we observed a space variability of the detection threshold as large as 0 3 units ascribed to both the geometrical configuration of the network and the differences in the noise levels at the different stations a sensitivity study indicates that the estimation of the detection threshold is robust for changes in the focal depths and stress drop while it is strongly affected by the anelastic attenuation in our case changes of the reduced time t in the range 0 015 0 035 s generate changes in the completeness threshold of 0 5 units noise levels were obtained by a statistical analysis on the power spectral density curves along almost three years of continuous data from 22 stations we found that at short periods major time variations are generated by diurnal changes in the wind intensity and other meteorological factors at longer periods we retrieved the microseismic peak resulting from the constructive interference of oceanic waves we also found an additional peak between 2 and 4 s correlated with the sea wave height along the tyrrhenian coast

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

detecting young slow slipping active faults by geologic and multidisciplinary high resolution geophysical investigations a case study from the apennine seismic belt italy 1 the southern apennines range of italy presents significant challenges for active fault detection due to the complex structural setting inherited from previous contractional tectonics coupled to very recent middle pleistocene onset and slow slip rates of active normal faults as shown by the irpinia fault source of a m6 9 earthquake in 1980 major faults might have small cumulative deformation and subtle geomorphic expression a multidisciplinary study including morphological tectonic paleoseismological and geophysical investigations has been carried out across the extensional monte aquila fault a poorly known structure that similarly to the irpinia fault runs across a ridge and is weakly expressed at the surface by small scarps warps the joint application of shallow reflection profiling seismic and electrical resistivity tomography and physical logging of cored sediments has proved crucial for proper fault detection because performance of each technique was markedly different and very dependent on local geologic conditions geophysical data clearly 1 image a fault zone beneath suspected warps 2 constrain the cumulative vertical slip to only 25 30 m 3 delineate colluvial packages suggesting coseismic surface faulting episodes paleoseismological investigations document at least three deformation events during the very late pleistocene 20 ka and holocene the clue to surface rupturing episodes together with the fault dimension inferred by geological mapping and microseismicity distribution suggest a seismogenic potential of m6 3 our study provides the second documentation of a major active fault in southern italy that as the irpinia fault does not bound a large intermontane basin but it is nested within the mountain range weakly modifying the landscape this demonstrates that standard geomorphological approaches are insufficient to define a proper framework of active faults in this region more in general our applications have wide methodological implications for shallow imaging in complex terrains because they clearly illustrate the benefits of combining electrical resistivity and seismic techniques the proposed multidisciplinary methodology can be effective in regions characterized by young and or slow slipping active faults

a study of the seismic response of the city of benevento southern italy through a combined analysis of seismological and geological data abstract a previous analysis improta l g di giulio and a rovelli 2005 variations of local seismic response in benevento southern italy using earthquakes and ambient noise recordings j seism 9 191 210 of small magnitude earthquakes recorded at 12 sites within the city of benevento has stressed the significant role played by near surface geology in causing variability of the ground motion in this paper we extend the study of the seismic response from 12 sites to the entire urban area based on inferences from the comparison at the 12 sites between earthquake and ambient vibration results we have collected ambient noise at about 100 sites within the city intensifying measurements across the main shallow geological variations we use borehole data to interpret ambient noise h v spectral ratios in terms of near surface geology comparing h v curves to theoretical transfer functions of 1d models along five well constrained profiles on the basis of geological geotechnical and seismic data we identify three main typologies of seismic response in the city each type of response is associated to zones sharing common soil conditions and similar soil classes according to building codes for seismic design moreover we find that the spatial variation of the seismic response in the ancient town area is consistent with the damage pattern produced by a very destructive well documented historical earthquake that struck the city in 1688 causing mcs intensity of ix x in benevento finally we use ground motions recorded during the experiment by improta et al improta l g di giulio and a rovelli 2005 variations of local seismic response in benevento southern italy using earthquakes and ambient noise recordings j seism 9 191 210 to generate synthetic seismograms of moderate to strong mw 5 7 molise 2002 and ms 6 9 1980 irpinia earthquakes we calibrate the random summation technique by ordaz et al ordaz m j arboleda and s k singh 1995 a scheme of random summation of an empirical green s function to estimate ground motions for future large earthquakes bull seism soc am 85 1635 1647 using recordings of these earthquakes available in benevento after a satisfactory fit between observed and synthetic seismograms we compute response spectra at different sites and speculate on effects of the geology class at large level of shaking including soil nonlinearity we find that large discrepancies from design spectra prescribed by seismic codes can occur for a wide sector of benevento especially for periods

palaeomagnetism and palaeogeography of mongolia in the cretaceous permian and carboniferous preliminary data abstract the paper reports on the results of palaeomagnetic stability tests of oriented samples of lithologically different types of cretaceous permian and carboniferous rocks from northern and southern mongolia the permian andesites and tuffites from three localities barun buren tel tin gol and chulut tsagan del have yielded interesting results groups of normally and reversely polarized andesite tuffs were found even within a single outcrop by means of thermal field demagnetization and multicomponent analysis of the magnetization with a view to the number of samples 177 suitable for analysis and the number of localities 9 the reported palaeomagnetic data should be considered as preliminary the interpreted results indicate a different palaeogeographic evolution of northern and southern mongolia relative to the siberian platform and north china in the permian and carboniferous on the other hand similar apparent polar wander paths for north china lin et al 1985 and the studied regions of northern and southern mongolia indicate similar palaeogeographic evolution in the permian to carboniferous

surface wave array tomography in se tibet from ambient seismic noise and two station analysis i phase velocity maps summary empirical green s functions egfs between pairs of seismographs can be estimated from the time derivative of the long time cross correlation of ambient seismic noise these egfs reveal velocity dispersion at relatively short periods which can be used to resolve structures in the crust and uppermost mantle better than with traditional surface wave tomography we combine rayleigh wave dispersion estimates from egfs and from traditional two station ts analysis into a new approach to surface wave array tomography with data from dense receiver arrays we illustrate the methodology with continuous broad band recordings from a temporary seismographic network on the southeastern part of the tibetan plateau in sichuan and yunnan provinces sw china the egfs are robust under temporal changes in regional seismicity and the use of either ambient noise approximated by records without signal from events with magnitude mb 5 or 4 or surface wave coda produces similar results the egfs do not strongly depend on the presence of large earthquakes but they are not reciprocal for stations aligned in the n s direction this directionality reflects the paucity of seismicity to the north of the array using a far field representation of the surface wave green s function and an image transformation technique we infer from the egfs the rayleigh wave phase velocity dispersion in the period band from 10 30 s a classical ts approach is used to determine rayleigh wave phase velocity dispersion between 20 120 s together they constrain phase velocity variations for t 10 120 s which can be used to study the structure from the crust to the upper mantle beneath se tibet short and intermediate period 10 80 s phase velocities are prominently low suggesting that the crust and upper mantle beneath se tibet is characterized by slow shear wave propagation

deep characterization of the santiago basin using hvsr and cross correlation of ambient seismic noise abstract continuously recorded seismic ambient noise is used to investigate the intermediate and deep structure of the santiago basin for seismic site response evaluation single station h v spectral ratios hvsr were used as a proxy to identify zones with high stiffness soils and low impedance contrast with the underlying bedrock as a complement of available surface geology information frequency domain cross correlation of the vertical components of ambient noise were calculated and used to estimate phase velocity dispersion curves associated to station pairs over different soil deposits in addition noise correlation functions ncfs calculated from time domain cross correlation of the vertical seismic noise records were used to estimate group velocity dispersion curves and to verify results from the spectral method data processing from both methods resolves a frequency band between 0 1 and 8 0 hz a critical band for civil infrastructure that is difficult to determine with traditional local scale passive surface wave methods station pairs with high signal correlation over stiff soils in the center south and east part of the basin mainly associated to flat hvsr response yielded robust phase velocity dispersion curves that vary approximately from 3 5 km s at 0 1 hz to 1 km s at 4 hz shear wave velocity profiles inverted from the dispersion curves show high average shear wave velocities that also have a pronounced increase rate with depth and a lack of clear soil bedrock interface at depths predicted by available gravimetric data

fault geometries from the space distribution of the 1990 1997 sannio benevento earthquakes inferences on the active deformation in southern apennines in this study we analyze the recent 1990 1997 seismicity that affected the northern sector sannio benevento area of the southern apennines chain we applied the best estimate method bem which collapses hypocentral clouds to the events of low energy md max 4 1 seismic sequences in order to constrain the location and geometry of the seismogenetic structures the results indicate that earthquakes aligned along three main structures two sub parallel structures striking nw se 1990 1992 benevento sequence and one structure striking ne sw 1997 sannio sequence the southernmost nw se structure which dips towards ne overlies the fault that is likely to be responsible for a larger historical earthquake io max xi mcs 1688 earthquake the northernmost nw se striking structure dips towards sw the ne sw striking structure is sub vertical and it is located at the northern tip of the fault segment supposed to be responsible for the 1688 earthquake the spatio temporal evolution of the 1990 1997 seismicity indicates a progressive migration from se benevento to nw sannio associated to a deepening of hypocenters i e from about 5 to 12 km hypocenters cluster at the interface between the major structural discontinuities e g pre existing thrust surfaces or within higher rigidity layers e g the apulia carbonates available focal mechanisms from earthquakes occurred on the recognized nw se and ne sw faults are consistent with dip slip normal solutions this evidences the occurrence of coexisting nw se and ne sw extensions in southern apennines

a geological transect from kun lun to karakorum sinkiang china the western termination of the tibetan plateau preliminary note a geological geophysical expedition ev k2 cnr 1988 visited the area from west kun lun to karakorum k2 gasherbrum seven tectonic units including sedimentary magmatic and metamorphic rocks were distinguished in this area the northernmost are suggested to belong to the kun lun and qiangtang microplates the sedimentary sequence of shaksgam is proved to extend from the permian to the jurassic with carboniferous and cretaceous ages more doubtful this sequence shows intermediate affinities between the karakorum and the qiangtang the two southernmost units belong to the karakorum microplate the karakorum fault zone comprises a complex pattern of faults and thrusts with brittle deformation and uplifting of granitoid bodies

spatio temporal seismicity patterns using mutual information application to southern iberian peninsula spain earthquakes abstract a quantitative method to characterize the spatio temporal evolution of the seismic activity of a region for a given time interval is proposed in this paper the epicentral region is divided in equal area parallelograms that we call cells a probability p i is assign to every cell depending on its seismic activity level the evolution of the mutual information based on these probabilities allows us to fit the optimal value for p i s the analysis results show that is possible to monitor the change of seismic activity quantitatively we show that a propagation model based on cross template model ct model give us a criteria whether or not an area whose size is determined by the model mathematically is going to be considered seismically activated in a period of time whose value is also the result of the application of the method our method is applied to the data of southern iberian peninsula seismicity including more than 10 000 earthquakes data available from the andalusian seismic network is used from 1985 to 1995

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

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

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

the north karakorum side of the central asia geopuzzle an italian geological team visited a remote and in part never studied area in the northern hunza region pakistan which represents the link between the karakorum and pamir ranges the north karakorum sequence commences in the permian with terrigenous sediments followed by shallow to deep marine carbonates deposited on a newly formed passive margin deep water sedimentation continued till the end of the middle triassic when carbonate platform conditions resumed an episode of deltaic red sandstones with orogenic provenance is interbedded in the liassic and it is transgressed by a middle to upper jurassic shallow water marine unit eventually all of the sequence was faulted and folded with weak metamorphic imprint before fluviatile red polygenic conglomerates sealed the succession in a spectacular unconformity the north karakorum provides an example of a microplate that rifted away from gondwana in the permian reached deep marine conditions in the early triassic and marginally recorded compressive movements in the liassic a subsequent orogenic episode points to a reorganization of the southern asian margin possibly around middle cretaceous time finally the north karakorum was affected by strong fold thrust deformation and low to very low grade metamorphism in the cainozoic related to the india asia collision

a review of indian phanerozoic palaeomagnetism implications for the india asia collision abstract an overview is presented of the indian apparent polar wander path apwp for the phanerozoic and in particular for post late palaeozoic times this apwp is compiled on basis of data available at october 1981 from peninsular and extrapeninsular indo pakistan and from dsdp cores from the indian plate one of the more important and newly recognized features of this apwp is a large scale triassic jurassic loop this loop indicates a changeover from a late palaeozoic early mesozoic northwards and counter clockwise rotational movement with greater india reaching moderately low southern latitudes into a southwards and clockwise rotational movement during the early to middle jurassic recognizable likewise in apwp s from other gondwana continents this loop reflects the opening of the neotethys studies of extrapeninsular regions up to and north of the indus tsangpo suture zone have shown wide spread presence of magnetic overprints which delineate two regionally confined age groups younger overprints 20 40 m y predominate in the more external thrust zones older overprints 50 60 m y in contrast are found in the more internal zones both north and south of the indus tsangpo suture zone the latter are interpreted to reflect a late phase of relaxation in the early tertiary collision of greater india with south central asia or off shore island arcs which occurred at equatorial to low northern palaeolatitudes 0 10 n subsequent northwards movement over 2500 3000 km or more and impingement of greater india into southern asia resulted into large scale underthrusting of greater india along the main central thrust beneath southern tibet and to clockwise rotation of thrust units in the western himalaya a discrepancy between indian palaeomagnetic data and results available todate from southern tibet is discussed

the september 27 2012 ml 4 1 benevento earthquake a case of strike slip faulting in southern apennines italy abstract on september 27 2012 at 01 08 utc a m l 4 1 earthquake started a seismic sequence approximately 10 km east of the city of benevento in southern apennines italy during the following four days about 40 events with m l ranging between 1 3 and 4 1 were detected in the same area where the seismic hazard is one of the largest of the italian peninsula and where several historical and destructive events took place in order to investigate the seismicity spatio temporal pattern and to identify the seismogenic source geometry a detailed analysis was performed integrating data recorded at three different seismic networks the earthquakes were relocated using the double difference technique and focal mechanism solutions were obtained by the moment tensor inversion also to better understand the rupture process seismic source parameters were estimated and apparent source time functions were inverted to retrieve the slip distribution for the largest magnitude event our results show the existence in the study area of roughly e w striking fault plane with a right lateral strike slip kinematics seated at mid crustal depths 10 20 km revealing a characteristic seismicity quite different from that typically associated to the outcropping nw se striking active normal faults that are responsible of moderate to large earthquakes in the southern apennines axial sector in this work we address questions concerning i the presence in the benevento area of a mid crust seismogenic strike slip fault previously unrecognized ii its link to the regional seismotectonic setting and iii the existence of a strike slip tectonic regime that uniformly extends in the footwall of the apennines thrust at relevant depth not only in the apulian foreland as demonstrated to date but also under the mountain chain axial zone

dispersed remnants of a northeast pacific fringing arc upper paleozoic terranes of permian mccloud faunal affinity western u s two fragmentary subparallel belts of terranes within the western north american cordillera contain upper paleozoic rocks and are characterized by contrasting lithotectonic assemblages and contrasting permian faunal affinity these two belts are a volcanic arc related successions of permian mccloud faunal affinity mccloud belt and b subduction related accretionary complexes of permian tethy an faunal affinity cache creek belt this paper supports the hypothesis that the fragmentary terranes of the mccloud belt once constituted parts of a northeast pacific fringing arc system and in constrast to some earlier interpretations concludes that the volcanic arc evolved above an eastward dipping subduction zone the absolute distance between this arc and western north america during the late paleozoic cannot be constrained however there is little evidence to suggest closure of a major 10 km ocean basin or protracted periods of westward dipping subduction parts of devonian to permian volcanic island arc sequences of the western u s cordillera are represented in the northern sierra eastern klamath bilk creek grindstone and chilliwack terranes these scattered volcanic arc remnants share several fundamental characteristics 1 the sequences were constructed across continental affinity basement assemblages 2 they underwent similar tectonic evolution during late paleozoic time such as coeval pulses in volcanism and related depositional histories 3 they contain early permian mccloud type fauna of distinctive biogeographic affinity 4 mccloud belt terranes are spatially and possibly genetically related to westward lying accretionary complexes of the cache creek belt which contain fragments of upper triassic blueschist and permian limestone blocks bearing tethyan permian fusulinids and corals based on the presence of distinctive early permian mccloud fauna the island arc remnants discussed in this paper are referred to as the mccloud belt the similarities between mccloud belt terranes suggest that they were once parts of a long lived late paleozoic volcanic arc complex the stratigraphy of these terranes records the tectonic evolution of the volcanic arc volcanism within the paleozoic arc began as early as the early devonian and was succeeded or accompanied by carbonate and epiclastic sedimentation during the middle and late devonian an influx of detritus derived from sedimentary and metasedimentary rocks during the late devonian and mississippian records the uplift and erosion of arc basement sequences an event that was at least locally accompanied by ongoing volcanism a pulse in volcanism during the pennsylvanian and coeval uplift led to the establishment of shallow marine and deltaic volcanogenic and carbonate sedimentation and locally subaerial exposure which persisted into the early early permian elsewhere during the early permian shallow water carbonate deposition was established with only minor influx of volcanogenic debris during the late permian and locally as early as late early permian a major pulse in volcanism occurred and is now represented by voluminous sequences of volcanogenic debris and lavas most of these sequences are overlain by upper triassic carbonate platformal sequences arc volcanism was recorded at least locally until the middle jurassic paleomagnetic data are used to constrain a schematic pre cretaceous reconstruction of these volcanic arc sequences and their associated subduction assemblages the inferred paleogeography of island arc sequences and the adjacent accretionary terranes suggests that volcanism occurred above an east dipping subduction zone with a long lived paleogeographic relation to north america the current structural position of these terranes is largely the result of mesozoic and locally younger deformation

a seismotectonic analysis of the anza seismic gap san jacinto fault zone southern california small earthquake epicenters near the anza seismic gap define a 20 km quiescent segment of fault bounded to the northwest and southeast by areas of relatively high seismicity recent moderate earthquakes on and near the san jacinto fault in the gap and their relatively depressed aftershock activity indicate that the fault is seismogenic and highly stressed but locked by some mechanism the locked nature of the fault may be due to relatively high compressive stress normal to the fault resulting from the convergent geometries of the local active discontinuous faults and the oblique orientation of the regional maximum compressive stress strain is not being relieved by aseismic fault creep a swarm of small earthquakes in the crustal block 13 km southwest of the anza gap beneath the cahuilla valley recently released stress in an area which was previously highly active before the 1918 m 6 8 and 1937 m l 6 0 earthquakes the occurrence of these periods of increased seismicity near cahuilla in the years immediately before the nearby closer than 35 km large earthquakes and the recent swarm suggest that the ground beneath cahuilla may be acting as a stress meter signaling the presence of high stresses before large local earthquakes the length of the quiescent fault segment suggests potential for about an m 6 5 earthquake if the entire segment ruptures at once

local site effects in the town of benevento italy from noise measurements the study of ground motion amplification produced by surface geology is extremely interesting in the benevento area southern italy as it is characterized by high seismic hazard the present moderate to low seismicity makes the noise method appropriate to estimate the seismic site response in the area the three components of seismic noise have been recorded in five sites in the benevento metropolitan area characterized by different surface geology in order to estimate the seismic site response in evaluating site amplification effects we used the direct interpretation of amplitude spectra and standard spectral ratio techniques evaluating sediment to bedrock sediment to average and h v spectral ratios the temporal evolution of the noise spectra is analysed within one day in order to assess the stationarity of the noise signal the noise wavefield properties have been studied through polarization analyses in selected bands of frequency where spectral peaks are observed to dominate to better understand the real nature of those peaks results give evidence of low amplification levels missing any correlation between spectral amplitudes and sediment thickness over the basement we interpret this result as due to the poor impedance contrast between sediments and basement which is characterized by low values of shear waves velocity moreover sharp amplitude peaks are observed in the raw spectra of the sediment sites in the 2 4 hz frequency band a numerical simulation interprets this effect as possibly associated with a wide scale structure invoking the presence of a sharper impedance contrast at greater depth at high frequencies the action of ambient noise sources mainly active on horizontal components of motion is retained dominant to generate the prominent peaks observed in the h v spectral ratios in some cases the presence of a near surface low velocity layer can contribute to amplify the seismic motion generated at these frequencies

s waves profiles from noise cross correlation at small scale abstract cross correlations of ambient seismic noise recordings are studied to infer shear wave velocities vs profiles versus depth experiments are performed over inter station distances ranging from 60 m to about 400 m in the crowded and noisy historical centre of napoli where the conditions for the use of active controlled source seismic spreadings are prohibitive even for just one receiver from the noise cross correlation group velocity dispersion curves are extracted with ftan method and their non linear inversion supplies vs profiles versus depth the information of nearby stratigraphies and the range of vs variability for samples of neapolitan soils and rocks confirms the validity and reliability of the results obtained with our expeditious procedure if successfully tested in other geological settings the proposed approach is a low cost methodology to get reliable vs velocity profiles versus depth

tectonic stress orientation and the seismic regime of a single fault abstract the seismic regime of tectonic faults was studied by the method of physical modelling this method is based on the assumption that the physical processes in actual seismo active fault zones can be scaled in laboratory conditions the results of our laboratory experiments on plate models proved the great importance of tectonic stress orientation on the seismic regime of tectonic faults changes in the fault inclination led to distinct changes both in the recurrence time intervals between individual seismic events and in the amount of seismic energy released for some fault inclinations the seismic activity of faults vanished altogether only a limited zone in the fault plane was found to participate in the process of seismic energy release the extent of this so called seismo active zone depends not only on the contact conditions but also on the value of the acting load and on the fault inclination this presumption is supported by the fact that for each inclination there exists an upper limit to the seismic energy that can be released in one seismic event

palaeontology of the 1985 tibet geotraverse lhasa to golmud palaeontological collections made on the 1985 geotraverse are used to date the associated strata and provide information about palaeoenvironments a biostratigraphical and palaeoenvironmental framework for the tibetan plateau is constructed the crucial stratigraphical and palaeontological evidence for dating volcanic sequences flysch basins open oceanic sediments latest marine sediments and terrestrial red beds in each terrane is reviewed a quantitative palaeobiogeographical analysis from the carboniferous to early triassic is presented for the tibetan fauna and flora to establish the biotic relationships between the various terranes this is based largely on coral brachiopod and fusulinid distributional data but other groups have also been analysed including the permian terrestrial flora this analysis demonstrates a clear diversity gradient from equatorial or sub equatorial biotas in the north to temperate biotas in the south during the late palaeozoic no suture line consistently m arks the position of a faunal floral break during the late palaeozoic and there appears to have been no physical barrier such as a large ocean to biotic dispersal between tibetan terranes at this time climate is seen as the most likely factor dominating biotic distribution in this region and the early permian glaciation had a profound effect on marine faunal distributions in tibet

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

influence of parameterization on inversion of surface wave dispersion curves and definition of an inversion strategy for sites with a strong vs contrast inversion of the fundamental mode of the rayleigh wave dispersion curve does not provide a unique solution and the choice of the parameterization number of layers range of velocity and thickness values for the layers is of prime importance for obtaining reliable results we analyzed shear wave velocity profiles derived from borehole tests at 10 sites where soil layers overlay bedrock in various geologic contexts one to three seismic layers with linear velocity laws could model all of them three synthetic models defined from this preliminary study were used to understand the influence of parameterization on the dispersion curve inversion this analysis resulted in the definition of a two step inversion procedure for sites exhibiting a strong impedance con trast in the first step the dispersion curve is inverted with an increasing number of layers over half space the evolution of the minimum misfit and bedrock depth with number of layers allows the estimation of the true bedrock depth range in the

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

seismic regime of a single fault model a special experimental technique enabled us to study in detail seismic events on a fault model in a uniaxial stress field the recording system used made it possible to investigate the radiation pattern for all the events observed including the precise determination of the dislocation origin

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