contemporaneous extension and compression in the northern apennines from earthquake fault plane solutions summary the northern apenninic arc belongs to the deformation zones surrounding the adriatic plate which behaves as a rigid block it is a ne verging fold and thrust belt which developed since the miocene with the migration of an extensional compressional pair previous seismological data are roughly in agreement with this deformation picture although the outer compressional front was not clearly defined by the few available solutions in this work we confirm the existence of two adjacent zones of contemporaneous extension and compression in the northern apennines defining the extent of these two zones and their interim1 deformation better than was previously done this is accomplished through the analysis of 125 new focal mechanisms of earthquakes 2 6 md 4 8 recorded by the national network of the lstituto nazionale di geofisica in the period 1988 1995 the two deformation zones are clearly separated and lie very close to each other with a partial overlapping in the emilian tuscan apennines strikeslip events are scattered in most of the study area thrust faulting earthquakes are located in the internal part of the most recently active thrust front middle upper pleistocene there is a general trend of the compressional p axes of thrust fault and strike slip solutions to be perpendicular to the apenninic direction in the external zone while the tensional axes of the normal fault and strike slip solutions in the belt do not show a uniform orientation however clearly evident is the ene direction of extension in the peri tyrrhenian region consistent with the direction of shmln in the quaternary volcanoes of this region inferred from borehole breakouts and microearthquake fault plane solutions we determined the orientation of the stress tensor in the two main deformation zones by inversion of the 125 fault plane solutions determined in this study we found that the external belt is characterized by ne sw compression ol horizontal oriented n45 e while a normal faulting regime with o3 e w oriented is characteristic of the umbria tuscany back arc region

modelling coseismic displacements during the 1997 umbria marche earthquake central italy summary we propose a dislocation model for the two normal faulting earthquakes that struckthe central apennines umbria marche italy on 1997 september 26 at 00 33 mw 5 7 and 09 40 gmt mw 6 0 we t coseismic horizontal and vertical displacements resulting from gps measurements at several monuments of the igmi istituto geogra co militare italiano by means of a dislocation model in an elastic homogeneous isotropic half space our best tting model consists of two normal faults whose mechanisms and seismic moments have been taken from cmt solutions it is consistent with other seismological and geophysical observations the rst fault which is 6 km long and 7 km wide ruptured during the 00 33 event with a unilateral rupture towards the se and an average slip of 27 cm the second fault is 12 km long and 10 km wide and ruptured during the 09 40 event with a nearly unilateral rupture towards the nw slip distribution on this second fault is non uniform and is concentrated in its se portion maximum slip is 65 cm where rupture initiated the 00 33 fault is deeper than the 09 40 one the top of the rst rupture is deeper than 1 7 km the top of the second is 0 6 km deep in order to interpret the observed epicentral subsidence we have also considered the contributions of two further moderate magnitude earthquakes that occurred on 1997 october 3 mw 5 2 and 6 mw 5 4 immediately before the gps survey and were located very close to the 09 40 event of september 26 we compare the pattern of vertical displacements resulting from our forward modelling of gps data with that derived from sar interferograms the t to sar data is very good con rming the reliability of the proposed dislocation model

a numerical method for determining the state of stress using focal mechanisms of earthquake populations application to tibetan teleseisms and microseismicity of southern peru the numerical method described in this paper enables the study in terms of stress of the kinematics of seismic faults provided by focal mechanisms this method assumes a mean state of stress in the source region and is based on the simple mechanical model used for fault population analysis which supposes slip in the direction of the resolved shear stress acting on the fault plane the proposed algorithm first defines compressional and tensional zones resulting from superimposition of the compressional and tensional quadrants limited by the nodal planes this enables one to test the data homogeneity furthermore this restricts the space where the principal stress axes have to be searched then for each principal stress reference whose location is constrained by above confined zones the r value chosen equal to 2 1 3 1 is computed which fits the slip vector on each nodal plane this permits one to select a set of preferred seismic fault planes from a set of auxiliary planes finally a state of stress is computed from the preferred seismic fault plane set using the non linear simplex method already applied to fault populations this algorithm is constructed so as to avoid two major difficulties misleading estimation of the deviatoric stress tensor which may result from excessive emphasis by minimizing the residuals by a least squares method if some of the data are wrong and a lengthy prospection of the stress references over all the space of directions this calculation does not take into account possible changes of the strike and dip of the nodal planes however we use rotations of nodal planes in agreement with the first arrival data to test the compatibility of these data with the computed state of stress tibetan teleseisms and southern peruvian microseisms are analyzed and results are compared with kinematics of superficial recent and active faults measured in field in the same regions this suggests that major seismic events may give a good evaluation of the regional mean state of stress focal mechanisms of the small events are also modelled by a mean stress deviator but this differs significantly from the regional state of stress in southern peru deduced from quaternary faulting this may be due to imprecise location of the small events however some movements are strongly different from those predicted by the computed mean stress deviator this suggests that small fault kinematics surely depend on the regional state of stress but that local effects may control the small deformations

spatial variation in stresses in peninsular italy and sicily from background seismicity abstract we have retrieved the stress tensor orientation in the italian region applying the fmsi technique gephart j 1990b fmsi a fortran program for inverting fault slickenside and earthquake focal mechanism data to obtain the regional stress tensor comput geosci 16 953 989 to fault plane solutions of 298 small earthquakes 2 5 m d istituto nazionale di geofisica in the period 1988 1995 first we verified that the stress inversion procedure generally applied to a large number of focal mechanisms of earthquakes recorded in a local seismic network could be successfully used in italy using background seismicity recorded over large 100 200 km regions then comparing the stress inversion results with other stress indicators we find that they are geologically sound for many regions in italy even if the misfit values are relatively large we also find that the largest misfit values are determined by a few earthquakes only 10 20 of the total number excluding these earthquakes from inversion the average misfit becomes much lower by 30 40 the results obtained in this study confirm the large variations of the stress field over a relatively short distance in italy but also confirm the existence of regions extending for a few hundred kilometres within which the stress is homogeneous among these most of the apennines are dominated by extension perpendicular to the trend of the mountain belt only in the northern apennines is there any clear distinction between an area of extension in the inner portion of the belt and an area under horizontal compression along the adriatic margin of the belt more rapid variations occur around calabria and sicily as expected because of the complexities linked with the tyrrhenian subduction and with active volcanism in the ionian calabrian coastal region there are hints of active nw se compression although constrained by a few data whereas in the messina strait we observe e w extension and a vertical 1 in northern and western sicily our results indicate n s to nw se compression roughly consistent with the general convergence between the european and the african plates

the 1997 umbria marche italy earthquake sequence a first look at the main shocks and aftershocks a long sequence of earthquakes six with magnitudes between 5 and 6 struck central italy starting on september 26 1997 causing severe damages and loss of human lives the seismogenic structure consists of a nw se elongated fault zone extending for about 40 km the focal mechanisms of the largest shocks reveal normal faulting with ne sw extension perpendicular to the trend of the apennines consistently with the quaternary tectonic setting of the internal sector of the belt and with previous earthquakes in adjacent regions preliminary data on the main shocks and aftershocks show that extension in this region of the apennines is accomplished by normal faults dipping at low angle 40 to the southwest and confined in the upper 8 km of the crust these normal faults might have reactivated thrust planes of the pliocene compressional tectonics the aftershock distribution and the damage patterns also suggest that the three main shocks ruptured distinct 5 to 15 km long fault segments adjacent and slightly offset from one another

models of the complex source of the el asnam earthquake abstract the el asnam earthquake of 10 october 1980 was originated by a thrust across a sw ne oriented fault 36 km long and 15 km wide it is a complex event with a rupture propagating from the sw to the ne fault mapping hypocenter distribution and b factor studies indicate fault branching to the ne a dislocation model is used to explain the branch with normal faulting at beni rached as a consequence of the thrust across a main fault that changes orientation the mechanism of the 1954 earthquake must be similar even though only normal faulting was observed at the surface

spectral characterization of igneous rocks in the 8 to 12 μm region variation in the spectral response of silicates in the thermal infrared tir from 8 to 12 m is the foundation for potentially important applications in the lithologic characterization of terrestrial and extraterrestrial surfaces the purpose of this study is to elucidate the crystallo chemical basis for the variation in spectral behavior in terms which may be useful in remote sensing this has led to the definition of a new parameter scfm which is defined as the ratio sio2 sio2 cao feo mgo in minerals and rocks this parameter reflects the degree of depolymerization of the silica tetrahedra and is therefore highly correlated with the structure of tir reflectance spectra of major silicate minerals in both fine and coarse grained igneous rocks it is also a good numerical descriptor of igneous rock composition thus scfm is proposed as a very useful determinant for spectral identification of igneous rocks the scfm parameter was used to assess the effect of variations in location number and width of bands in discriminating rock composition an unfortunate ambiguity exists in the use of the term band which in spectroscopy indicates a feature in a spectrum and in remote sensing signifies a specific wavelength increment or channel the latter definition is used in this paper spectra of coarse particulate mineral and solid rock samples were acquired in the laboratory a regression analysis of bands varying in width from 0 2 to 1 4 m versus scfm results in coefficients of determination correlation coefficients r2 ranging from 0 88 for two 1 2 m wide bands to 0 97 for seven 0 2 m wide bands deletion of bands in the ozone absorption region 9 4 10 2 m results in a decrease in r2 by only 0 01 stimulation of system noise by addition of 5 random counts to the bands decreases r2 by only 0 03 because spectra structure is modified by weathering alteration and texture of the samples the validity of these results is limited to fresh igneous rocks with this constraint it is concluded that accurate spectral identification of igneous rock composition is not greatly affected by bandwidth or system noise it is the overall spectral envelope rather than the fine structure in the tir which contains most of the information diagnostic of igneous rock composition this permits design of remote sensing systems with broad bands and corresponding higher signal to noise which can be traded off against the important requirement for higher spatial resolution

stereo cloud heights from multispectral ir imagery via region of interest segmentation multispectral thermal imagery acquired from low earth orbit was used to develop a method of cloud height determination that applies image brightness temperature histograms and region of interest roi image segmentation as a processing step prior to stereo height retrieval the national aeronautics and space administration s infrared spectral imaging radiometer isir acquired all imagery during the august 1997 sts 85 mission of the space shuttle discovery isir the first earth observing spectroradiometer to employ an uncooled large format microbolometer array focal plane provided continuous coverage in four spectral bands along track in an 80 km wide swath roi segmentation created binary cloud masks ranging over brightness temperatures in the imagery for which the parallax was determined by a two dimensional correlation method allowing stereo heights to be determined using the standard parallax equations a subpixel parallax algorithm allowed stereo heights to be determined with a precision of roughly plusmn0 39 km for clouds in the observed altitude range of 0 5 10 km

the deep seismicity of the tyrrhenian sea summary l he study reappraises the deep seismicity of the tyrrhenian sea careful examination of the quality of reported hypocentres shows that the earthquakes define a zone dipping nw about 200 km along strike 50 km thick and reaching a depth of about 500 km the zone is slightly concave to the nw at a depth of 300 km but contrary to many previous reports is not tightly concave nor are there significant spatial gaps in the seismicity which is effectively continuous with depth seismicity is however concentrated in the depth interval 250 300 km where the dip of the seismic zone changes from 70 above 250 km to a more gentle dip of 45 at greater depths seven fault plane solutions are available for the largest earthquakes in this depth interval all of them consistent with a p axis down the dip of the seismic zone and all of them requiring movement on faults out of the plane of the subducting slab two deep earthquakes near naples lie well outside the main zone of activity for one of which a fault plane solution is available that has ap axis not aligned with the dip of the seismic zone the tightly concave slabgeometry favoured by other reports is supported mainly by the location of these events near naples which we think may represent deformation in a separate probably shallower dipping piece of subducted lithosphere the lack of shallow seismicity and particularly of thrust faulting earthquakes at the surface projection of the benioff zone suggests that active subduction has ceased estimates of the convergence rate responsible for subduction in the last 10 myr far exceed the present convergence rate of africa and eurasia suggesting that the subduction was related instead to the stretching and thinning of the crust in the tyrrhenian sea

dynamic modelling of stress accumulation in central italy role of structural heterogeneities and rheology summary recent efforts to relate the style of seismicity in the central apennines to the stress build up induced by active geodynamic processes by means of simple viscoelastic dynamic models have shown that seismicity in this region is likely to be controlled by two major processes the westward underthrusting of the adriatic plate under the apennines and the asthenospheric upwelling underneath tuscany in this work using these results as a starting point we evaluate by means of 2 d dynamic models the effects of structural heterogeneities major crustal scale faults this improvement is made possible by the recent publication of the results of the crop 03 seismic line and of temperature dependent rheologies within the crust and the lithospheric mantle on the stress field induced by the two processes mentioned above modelling results are compared with detailed seismicity data we show that for all models the predicted stress fields are controlled at large wavelengths by an upward state of flexure in tuscany and a downward state of flexure in the apenninic foredeep in agreement with previous studies when activating crustal scale discontinuities however strong local rotations of the major axes of the stress tensor occur in the proximity of the faults generating complex local stress fields characterized by the coexistence of compressive and tensional styles this could explain the coexistence as observed within certain regions of central italy of compressive and extensional events when detailing the rheology using plastic behaviour for the lithospheric portions of the models a complex profile of yield stresses is considered the materials characterized by higher strength being the sedimentary cover and the lithospheric mantle model predicted stress concentrates in these materials the lateral variability of the thickness of the sedimentary cover induces strong local rotations at shallow depths of the stress eigenvectors all of the models predict a stress field roughly compatible with the distribution and style of seismicity of the region the use of progressively more realistic rheologies and geometries however gives slightly better results when compared to seismicity data this paper shows that sensible results may be obtained by combining active and natural source seismicity with finite element modelling

analysis of seismological and geological observations formoderate size earthquakes the colfiorito fault system central apennines italy to contribute to the understanding of the relationships between moderate earthquakes and the faults that are recognisable in the geological record we analysed seismological and geological data related to the 1997 98 umbria marche central italy earthquake swarm the seismological recordings collected by local networks allowed accurate location of about 1000 events whereas the geological field observations provided a picture of the structural features and the ground surface deformations we also re examined and utilised some already published data and results mostly about the fault plane solutions and the geology on the basis of earthquake locations fault plane solutions and geological mapping we explored the possible correlation between the earthquake causative fault planes and the normal faults exposed in the area our results show that the two mainshocks that occurred on september 26 1997 mw 5 7 and mw 6 0 originated on the same structure reactivating at depth the colfiorito normal faults both ruptures did not propagate up to the ground surface but triggered gravitational sliding that occurred along pre existing fault scarps the earthquake that occurred on october 14 1997 mw 5 6 originated on another fault branch at a much shallower depth in spite of the lower magnitude this earthquake produced tectonic ruptures where the fault plane projects to the surface in an area where no faults were previously mapped by comparing the paleostress reconstruction based on slickenside lineations analysis and the focal mechanism solutions we also suggest a possible correlation between the long term early middle pleistocene cumulative effects of the colfiorito fault system and the short term behaviour of the fault planes observed during this earthquake swarm favouring the idea of a seismogenic source producing clustered moderate size earthquakes rather than large events scattered in time our results suggest that the integration of geological and seismological observations can constrain the seismotectonic interpretations in regions of low level seismicity and that this integration can pose a reliable basis in the seismic hazard assessment

the 1997 umbria marche italy earthquake sequence relationship between ground deformation and seismogenic structure a field survey performed during the 1997 umbria marche earthquake sequence led us to recognize ground and pavement ruptures associated with the three largest shocks mw 5 7 the ruptures are concentrated in narrow bands that in part are on and near previously mapped high angle normal faults the geometry of the ground deformation is consistent with the ne trending extension indicated by cmt focal solutions of the mainshocks the distribution of aftershocks suggests that the three mainshocks occurred on 40 sw dipping normal faults geological investigations modelling of expected coseismic elevation changes and seismic data suggest that the surface deformation is not the direct result of primary rupture of faults at depth

the development and behaviour of low angle normal faults during cenozoic asymmetric extension in the northern apennines italy abstract movements on low angle normal faults lanf are not predicted by traditional anderson byerlee frictional fault mechanics our investigations centre on three normal fault systems active at distinct times during the regional extension of the northern apennines with each showing different degrees of crustal exhumation these are from e to w the altotiberina fault system umbria the radicofani fault system tuscan mainland and the zuccale fault system isle of elba regional extension has been a continuous process since middle miocene migrating progressively from west to east with deformation accommodated by a set of e to ne dipping lanf and more steeply sw dipping antithetic structures the lanf acted as regional detachments accommodating a majority of the extension in the northern apennines with individual faults exhibiting several kilometres of displacement regionally the stress field has been characterised by a vertical 1 and a ne sw tuscan mainland and umbria to e w elba trending 3 where exposed at the surface the main lanf detachments possess a well developed fault core of foliated fault rocks in which fluids have played a key role in weakening due to reaction softening and the onset of stress induced solution precipitation mechanisms we speculate that the e dipping normal faults initiated with relatively low angles of dip due to differential drag generated by mantle flow following slab retreat and roll back beneath the apennine chain

varnish sediment and rock controls on spectral reflectance of outcrops in arid regions field observations in the meatiq dome eastern desert egypt show that amphibolite weathers to form massive outcrops and dense desert pavements that are extensively varnished laboratory based reflectance spectra of representative samples covering 5 cm 2 and spectra extracted from landsat thematic mapper data covering 2 25 x 10 4 m 2 confirm that varnish dominates the reflectance properties of amphibolite outcrops field laboratory and landsat data indicate that granite gneiss weathers to expose mainly bare rock whereas granitic out crops evolve to a mix of rock and locally generated sediment penetrative foliation in quartz phyllonite leads to production of slab shaped clasts that cover the surface the data show that mass wasting of the slabs results in a mix of rock varnish and sediment exposures outcrop reflectance properties for arid regions are thus dependent on both rock mineralogy and texture because both parameters modulate bedrock weathering and erosion

the perugia italy earthquake of 29 april 1984 a microearthquake survey a field study after the perugia earthquake of 29 april 1984 provided more than 300 well recorded events concentrated within two parallel clusters separated by 2 km and trending along the apenninic direction the length of the aftershock area is 14 km focal depths being shallower than 8 km relocation of the main event places the epicenter at the southern end of the aftershock zone suggesting a rupture propagation from se to nw most focal mechanisms are consistent with normal faulting the spatial distribution of seismicity suggests that the gubbio normal fault was activated during the main shock this earthquake together with the norcia 1979 and the abruzzi 1984 shocks is typical of the extension in the high apennines generated by the flexure of the mountain chain in response to regional compression the parma 1983 event a thrust belongs to the compres sion zone at the eastern flank of the chain these results are consistent with the ew continental collision along the apennines

split window retrieval of particle size and optical depth in contrails located above horizontally inhomogeneous ice clouds multichannel radiometer measurements of a newly formed contrail taken from a nasa er 2 aircraft over northern oklahoma during the fire cirrus ii experiment are used in a split window retrieval of the contrail s particle size and optical depth the effect of horizontal inhomogeneity in an underlying cirrus layer on the contrail retrieval is studied through the use of multi dimensional radiative transfer model simulations estimates of the contrail s effective radius are significantly smaller 5 7 m than those in the underlying cirrus 21 m the effect of horizontal inhomogeneity in the underlying cirrus on contrail particle size and optical depth retrievals is generally smaller than the corresponding effects of particle shape or spectral variations in surface emissivity on the retrievals the differences in particle size retrievals are 10 percent or less as a result of the inhomogeneity while they are from 10 to 40 percent for ice cylinders and range from 1 to 40 percent for ice spheroids horizontal inhomogeneity affected the optical depth retrievals by only one or two percent while surface emissivity variations affected the retrievals by 12 to 24 percent and particle shape produced differences as large as 9 percent

statistical occurrence analysis and spatio temporal distribution of earthquakes in the apennines italy abstract we present two examples of statistical analysis of seismicity conducted by integrating geological geophysical and seismological data with the aim to characterize the active stress field and to define the spatio temporal distribution of large earthquakes moreover our data will help to improve the knowledge of the seismogenic behavior of the areas and to provide useful information for seismic hazard evaluation the earthquakes are described by two non parametric statistical procedures integrating also tectonic physical parameters to study the spatio temporal variability the results show that the areas are characterized by 1 a stress regime with mainly extensional kinematics 2 tectonic structures mainly oriented with the active stress field s hmin n44 18 in the southern apennines and s hmin n50 17 in the central apennines 3 cluster distribution of seismicity and 4 a high probability of earthquake occurrence m 5 5 in the next 10 years

viscoelastic relaxation and long lasting after slip following the 1997 umbria marche central italy earthquakes summary we combine global positioning system gps measurements with forward modelling of vis coelastic relaxation and after slip to study the post seismic deformation of the 1997 umbria marche central apennines moderate shallow earthquake sequence campaign gps mea surements spanning the time period 1999 2003 are depicting a clear post seismic deformation signal our results favour a normal faulting rupture model where most of the slip is located in the lower part of the seismogenic upper crust consistent with the rupture models obtained from the inversion of strong motion data the preferred rheological model obtained from viscoelastic relaxation modelling consists of an elastic upper crust underlain by a transition zone with a viscosity of 10 18 pa s while the rheology of deeper layers is not relevant for the observed time span shallow fault creep and after slip at the base of the seismogenic upper crust are the first order processes behind the observed post seismic deformation the deep after slip below the fault zone at about 8 km depth acting as a basal shear through localized time dependent deformation identifies a rheological discontinuity decoupling the seismogenic upper crust from the low viscosity transition zone

active tectonics in central italy constraints from surface wave tomography and source moment tensor inversion abstract we investigate the lithosphere asthenosphere structure and active tectonics of central italy with emphasis on the umbria marche area by means of surface wave tomography and seismic moment tensor inversion the data include a large number of short period local and regional group velocity measurements sampling the umbria marche apennines and the adria margin respectively incorporation of published phase velocity measurements sampling italy and surroundings results from deep seismic soundings which go through the umbria marche area the local group velocity maps covering the area reactivated by the 1997 1998 umbria marche earthquake sequence suggest an intimate relationship between the lateral earth structure variations and the distribution of the active fault systems and related sedimentary basins the upper crustal models reveal the importance of inherited compressional tectonics on the recent extensional deformation and associated seismic activity source inversion studies of the main events of the 1997 earthquake sequence show the dominance of normal faulting mechanisms whereas selected aftershocks between the fault segments at the step over reveal that the prevailing deformation is of strike slip faulting type at the regional scale the crust exhibits clear layering and varies in thickness from about 25 km below the tuscan metamorphic complex tmc to about 30 km below the val tiberina extensional thick sedimentary basin and reaches about 35 km below the umbria marche geological domain umd the lithospheric mantle lid is thin about 30 km below tmc while it is about 70 km thick below umd a lithospheric root about 120 km wide between the tmc and umd reaches a depth of at least 130 km a low velocity zone defined mantle wedge vs less than 4 2 km s in the uppermost mantle overlying the high velocity lid is detached this wedge is about 20 km thick and decouples the underlying lid from the crust the retrieved crust and upper mantle structure beneath central italy is in agreement with bouguer anomaly and heat flow data and supports a delamination process the high velocity upper mantle underlying the mantle wedge is inferred to be subcrustal lithospheric material delaminated from the overlying crust

stress changes due to recent seismic events in the central apennines italy the central apennines italy are characterized by moderate seismic activity on normal faults oriented in directions parallel to the apenninic chain the subject of this study is the umbria marche apennines a segment approximately 200 km long where three main seismic events occurred in the last three decades the 1979 norcia earthquake was a mw 5 8 event taking place at the south end of the considered segment the 1984 gubbio earthquake was a mw 5 6 event which took place at the north end the 1997 1998 colfiorito sequence constituted 8 main shocks with magnitudes mw between 5 and 6 and epicenters located between the gubbio and the norcia earthquake areas a model made of an elastic half space is considered in which the seismic sources are represented by rectangular dislocations which have the appropriate values of source parameters and in which the static stress field produced by each event is calculated the analysis of the coulomb stress change c as a function of time shows that the coseismic stress transfer and fault interaction played an important role in the region during the past three decades 7 earthquakes of the 9 considered took place where c 0 such an interaction has been confirmed by the analysis of the aftershocks in the colfiorito zone post september 26 1997 about the 61 of the aftershocks considered took place where c 0 the comparison between the cs due to the coseismic stress transfer and the rate t due to the tectonic stress allows us to quantify the time advance of the earthquakes the cs pattern shows positive values in two areas that can be regarded as historical seismic gaps

geodetic and seismologic evidence for slip variability along a blind normal fault in the umbria marche 1997 1998 earthquakes central italy summary we analysed elevation changes induced by the 1997 1998 umbria marche central apennines italy earthquakes we employed data from a first order geodetic levelling line measured in 1951 1992 and 1998 the line bears a record of pre seismic and coseismic strains associated with the causative fault of the 1997 september 26 09 40 mainshock mw 6 0 a first level analysis performed under the assumption of slip homogeneity of coseismic slip shows misfits that cannot be reduced simply by altering the fault size and geometry a more detailed analysis based on a distribution of coseismic slip obtained from broad band seismograms provides a better fit and is in agreement with 1951 1992 elevation changes interpreted as precursory slip by previous investigators the levelling data sets new constraints on the location extent dip and depth of the fault in full agreement with seismological evidence and images from sar interferometry the data show no evidence for slip in the uppermost 3 km of the crust suggesting that a major and widely recognized normal fault that exists in the area is no longer active and showing a tendency of present tectonic strains to revert the current topographic setting

anatomy of late orogenic extension the northern apennines case abstract late orogenic extensional structures overprint the compressional structures of the northern apennines fold and thrust belt the tyrrhenian sea is the result of major continental extension and rifting which started in the thickened zone of the apulian corso sardinian collision it is believed to have commenced as early as in the late oligocene or early miocene in the corsica basin extension post dates the collision by approximately 20 ma the extensional stress field observed in the internal part of the northern apennines co exists with compression in the foreland part of the belt field borehole and refraction and reflection data were used to investigate the geometry of extension and how it affected the compressional abric in the northern apennines analysis of the collected data has revealed a complex geometry for the extension across the belt a geological cross section from the island of elba to the west of the italian peninsula to ancona in the east as well as a geodynamic model for the evolution of the northern apennines is presented and discussed from the early miocene stretching of the collision thickened crust created a n s rift which evolved into the present northern tyrrhenian sea typically two sets of extensional faults a low angle e dipping and a w dipping one are observed across the chain usually the w dipping faults have similar attitudes to those of the older reverse faults reactivating some of the thrusts as normal faults the e dipping normal faults however cut down section through the pre existing thrusts and in the internal part of the belt accommodate most of the displacement associated with extension a change in fault polarity occurs in the tuscan region and major faults dip towards the west a type subduction of the apulian crust under the corso sardinian block occurred after collision leading to the delamination of the apulian lithospheric mantle away from the crust collision induced delamination of the mantle lithosphere away from the zone of collision resulted in mechanical thinning of the lithosphere beneath the orogenic belt this process induced late orogenic crustal stretching in the internal zone of the northern apennines as the convergence between the apulian and corso sardinian blocks continued the extensional and compressional fronts accompanied by the delamination migrated from the hinterland towards the foreland of the orogen

imaging the complexity of an active normal fault system the 1997 colfiorito central italy case study 1 six moderate magnitude earthquakes 5 mw 6 ruptured normal fault segments of the southern sector of the north apennine belt central italy in the 1997 colfiorito earthquake sequence we study the progressive activation of adjacent and nearby parallel faults of this complex normal fault system using 1650 earthquake locations obtained by applying a double difference location method using travel time picks and waveform cross correlation measurements the lateral extent of the fault segments range from 5 to 10 km and make up a broad 45 km long nw trending fault system the geometry of each segment is quite simple and consists of planar faults gently dipping toward sw with an average dip of 40 45 the fault planes are not listric but maintain a constant dip through the entire seismogenic volume down to 8 km depth we observe the activation of faults on the hanging wall and the absence of seismicity in the footwall of the structure the observed fault segmentation appears to be due to the lateral heterogeneity of the upper crust preexisting thrusts inherited from neogene s compressional tectonic intersect the active normal faults and control their maximum length the stress tensor obtained by inverting the six main shock focal mechanisms of the sequence is in agreement with the tectonic stress active in the inner chain of the apennine revealing a clear ne trending extension direction aftershock focal mechanisms show a consistent extensional kinematics 70 of which are mechanically consistent with the main shock stress field

the sequence of moderate size earthquakes at the junction of the ligurian basin and the corsica margin western mediterranean the initiation of an active deformation zone revealed a new seismically active zone is found in the southern part of the ligurian basin 80 km west of corsica western mediterranean the activity began in february 2011 with a foreshock ml 4 and a mainshock ml 5 3 5 days later followed by numerous aftershocks we first analyze the fore and mainshock in detail we compare the results obtained using classical methods linear location in a 1d medium and focal mechanisms from p and s polarities and new approaches non linear location in a 3d medium and waveform modeling for determining the seismic moment and the focal mechanism both methods provided similar results for location depth in the range of 6 13 km and focal mechanisms which reveal reverse faulting with nodal planes oriented n s and ne sw we then locate 27 of the aftershocks in the 3d model and find a 10 km long ne sw alignment with a depth between 7 and 16 km in 2012 and 2013 three other moderate size events ml 3 8 4 and 4 5 occurred and confirm that this zone is still active the epicentral area is located in the oceanic domain of the ligurian basin from analysis of the bathymetry and high resolution multi channel seismic profiles no morphologic anomaly at surface and no inherited fault in the shallow 4 km depth were imaged which suggest that no significant deformation occurred in the area since 5 ma thus the structure s activated during the 2011 2013 sequence remain unknown in light of these results we point out a notable difference on both sides of the ligurian basin the northern margin close to the alpine chain suffered strong earthquakes and large cumulated deformation since 5 ma while the southern margin close to the corsica sardinia continental block is poorly deformed since 5 ma

mineralogic information from a new airborne thermal infrared multispectral scanner a new six channel aircraft multispectral scanner has been developed to exploit mineral signature information at wavelengths between 8 and 12 micrometers preliminary results show that igneous rock units can be identified from their free silica content and that carbonate as well as clay bearing units are readily separable on the digitally processed images

the development and structure of an oceanic squall line system during the south china sea monsoon experiment abstract a primary goal of the south china sea monsoon experiment scsmex a major field campaign of the tropical rainfall measuring mission trmm is to define the initiation structure evolution and dynamics of precipitation processes associated with the onset of the south china sea scs summer monsoon in this study dual doppler and dual polarimetric radar analysis techniques are used to investigate the development and structure of a squall line system observed on 24 may 1998 the focus is the linkage between the airflow and the microphysical fields through the system the squall line system including three distinct lines persisted from 1200 utc 24 may to the following day a detailed study was performed on the structure of the second and most intense line lasting for over 10 h compared to tropical squall lines observed in other regions this narrow squall line system had some interesting features including 1 maximum reflectivity as high as 55 dbz 2 relatively little stratiform rainfall th

quaternary extension in southern tibet field observations and tectonic implications we summarize evidence for quaternary and active faulting collected in the field during three sino french expeditions to southeastern tibet 1980 1982 detailed mapping of quaternary and active faults as well as microtectonic measurements indicate that normal faulting has been the dominant tectonic regime north of the himalayas in the last 2 0 5 m y the maximum horizontal principal stress in south tibet appears to be only the intermediate principal stress 2 1 being vertical south of the chord joining the eastern and western syntaxes of the himalayan arc extensional strains are principally localized within seven regularly spaced rift zones three of which have been studied in some detail the extension direction is determined to be n96 e 7 mainly from statistical averaging of strikes of newly formed normal faults throw rates on normal faults are evaluated for different time spans 2 0 5 m y 60 40 kyr and 10 2 kyr b p using structural and topographic reliefs as well as synglacial and postglacial vertical offsets the rate of quaternary extension is about 1 m y 1 along an 1100 km long ese traverse across south tibet this corresponds to a spreading rate of 1 0 6 cm yr this rate and the divergent horizontal projections of slip vectors of earthquakes along the himalayan front constrain the rate at which rigid india underthrusts southern tibet to be 2 1 cm yr although most of the normal faults appear to be independent of and nearly orthogonal to the e w mesozoic tertiary tectonic fabric the yadong gulu rift appears to be guided for over 130 km by the older oblique ne sw nyainqentanglha range and fault zones along it this reactivated zone is the most prominent left lateral strike slip fault system in se tibet excepting this zone and the vicinity of the se extremity of the karakorum fault quaternary strike slip faulting is rare in south tibet i e south of the chord between the syntaxes of the himalayan arc north of the chord the tectonic style is different there minor conjugate strike slip faulting is widespread and appears to control quaternary normal faulting which is more diffuse and subdued than in south tibet along the chord the presence of a major zone of active right lateral en echelon strike slip faults karakorum jiali fault zone probably reflects the greater facility of eastward extrusion in north central tibet in response to the northward push of india the eastern himalayan syntaxis may be an obstacle to such extrusion movements south of the chord

architecture and seismotectonics of a regional low angle normal fault zone in central italy information from surface geology subsurface geology boreholes seismic reflection and refraction profiles and seismicity are used to depict the geometry and the possible seismogenic role of the altotiberina fault af a low angle normal fault in central italy the af extends along the inner umbria region for a length of 70 km with an average dip of 30 and an horizontal displacement up to 5 km it emerges west of the inner border of the tiber basin and deepens beneath the umbria marche carbonate fold and thrust belt to a depth of 12 14 km close to the af surface trace low angle synthetic east dipping normal faults extensively outcrop whereas high angle antithetic west dipping normal faults prevail farther east integrating geological and seismologic information it can be stated that the af behaves as an active extensional fault zone and represents the basal detachment of the west dipping seismogenic normal faults of the umbria marche region the af belongs to a regional ne dipping low angle normal fault system etrurian fault system efs which extends for 350 km from northwestern tuscany to southern umbria early preliminary considerations suggest that the efs may play an important role in controlling active extension and related seismicity in northern central italy

a low angle normal fault in the umbria region central italy a mechanical model for the related microseismicity abstract in the northern apennines the upper crust is thinned by a set of east dipping low angle normal faults lanfs the easternmost and more recent of these lanfs is the altotiberina fault atf located in northern umbria the geometry of the atf has been reconstructed matching surface geology with seismic reflection profiles and borehole data the fault whose average dip is 20 borders the upper pliocene quaternary tiber basin and has a displacement of about 8 km the deeper portion of the atf is located below the axial zone of the northern apennines where the strongest instrumental and historical seismicity is recorded the microseismicity of the region m 1 to evaluate the boundary conditions for the brittle activity of the atf the fault can be reactivated for low values of differential stress 1 3 t 10 mpa and tensile fluid overpressure p f 3 e g v 0 93 in the peculiar situation of the northern apennines the deep emissions of large amounts of co 2 documented in the area can be entrapped in their ascent by structural seals e g atf favouring localised fluid overpressures the impossibility of sustaining p f 3 for wide fault portions counteracted by hydraulic fracturing increased permeability under low effective stress and load weakening behaviour for normal faulting would prevent the nucleation of moderate ruptures along the fault the short lived attainment of p f 3 along small fault portions can account for the microseismic activity located along the atf which occurs on rupture surfaces in the range of 10 1 10 3 km 2

three dimensional kinematic and microphysical evolution of florida cumulonimbus part ii frequency distributions of vertical velocity reflectivity and differential reflectivity abstract high resolution radar data collected in florida during the convection and precipitation electrification experiment are used to elucidate the microphysical and kinematic processes occurring during the transition of a multicellular storm from convective to stratiform stages a statistical technique is employed to examine the evolving properties of the ensemble small scale variability of radar reflectivity vertical velocity and differential reflectivity over the entire storm differential radar reflectivity data indicate that the precipitation at upper levels was nearly glaciated early in the storm s lifetime dual doppler radar data show that throughout the storm s lifetime both updrafts and down drafts were present at all altitudes and that most of the volume of the radar echo contained vertical velocities incapable of supporting precipitation size particles thus the ensemble microphysical properties of the storm were increasingly dominated by particles falling in an environment of weak vertic

two types of precipitation particle distribution in convective cells accompanying a baiu frontal rainband around okinawa island japan 1 polarimetric radar variables and ground based raindrop size distributions dsds of two convective cells in a baiu frontal rainband over the okinawa region were analyzed to clarify the precipitation particle distributions in convective cells with low echo top heights one cell existed in the stratiform rain zone and the other was in the convective rain zone of the rainband both cells had echo top 30 dbz heights of approximately 5 5 km above sea level with large radar reflectivity z h greater than 50 dbz in each core for the cell in the stratiform rain zone polarimetric variables indicated that small raindrops predominated differential reflectivity z dr was smaller than 1 5 db and the correlation coefficient hv was greater than 0 98 with large z h 40 dbz the dsd showed high number densities of small raindrops with diameters of 1 2 mm for the other cell polarimetric variables indicated the presence of large raindrops z dr greater than 1 5 db and hv smaller than 0 98 predominated in large z h 40 dbz the dsd for this cell showed lower number densities of raindrops with diameters of 1 2 mm and higher number densities of raindrops exceeding 3 mm the significance of these distributions was confirmed by the z dr and hv for 25 cells in the stratiform rain zone and for 28 cells in the convective rain zone it is notable that different precipitation particle distributions in convective cells were found in the stratiform and convective rain zones of a baiu frontal rainband with common characteristics of low echo top heights and large z h

analysis of small magnitude seismic sequences along the northern apennines italy article i nfo we analyze the seismicity of a small sector of the northern apennines merging data from the italian seismic bulletin with original data collected by temporary seismic networks our attention is focused on the region enclosed between the apenninic watershed and the adriatic sea this portion of belt is interested by the occurrence of diffuse crustal seismicity and small to moderate earthquakes in this paper we study the five small sequences with mainshock having mwb4 7 that in the past 15 years hit the area our interest is addressed to better understand the relationship between these events and the regional seismotectonic setting in terms of seismicity distribution and stress field two regions with different behavior in the seismic release can be distinguished i along the watershed where seismicity is clustered at shallow depths b15 km and where strong earthquakes occurred in the past ii an eastern portion where the seismicity is distributed across all of the crustal volume locally reaching depths down to 30 km the focal mechanism of the seismic sequences shows mainly normal fault kinematics coherent with the regional stress field detailed stress field analysis suggests a rotation of the principal stress axis moving from the axial part of the chain toward the adriatic sea to the east

effects of surficial modification processes on thermal infrared signatures in the arid southwestern united states thermal infrared spectra from both laboratory and remote sensing instruments were used to distinguish different age lava flows with varying amounts of surficial modification at cima and lunar crater volcanic fields the modification processes affecting the lava flows cause spectral differences that can be seen in remotely sensed emittance spectra from the thermal infrared multispectral scanner important influences on the thermal infrared spectra include aeolian mantling vegetation lava flow roughness and rock varnish laboratory thermal infrared reflectance spectra of the subaerially exposed surfaces of 1 15 cm basalt fragments at cima volcanic field show a feature attributable to rock varnish on the younger flows 0 14 0 75 m y that is lacking on the older flows 0 8 m y this suggests that rock varnish is thinner on the older flows at cima volcanic field scanning electron microscope images and thin sections of the different age flows at cima volcanic field support the conclusion that rock varnish is thinner and may be eroding on the older flow surfaces

complex normal faulting in the apennines thrust and fold belt the 1997 seismic sequence in central italy a long sequence of moderate magnitude earthquakes 5 m 6 struck central italy in september and october 1997 at the end of the sequence a year later the seismogenic area extends for about 60 km along the apennines the analysis of historical seismicity suggests that this seismic sequence filled a 700 year gap in this portion of the chain other historical sequences in the same area are characterized by prolonged seismic release on adjacent fault segments probably due to the in volvement of shallow and complex structures inherited by the compressive tectonics the distribution of seismicity and the fault plane solutions show that the extension in this region is accomplished by normal faults dipping at relatively low angles 40 to the southwest the focal mechanisms of the largest shocks reveal normal faulting with extension perpendicular to the apenninic chain northeast southwest consistently with the quaternary tectonics of the internal sector of the northern apen nine belt and with previous earthquakes in adjacent regions three mainshocks oc curred on distinct 5 to 10 km long fault segments adjacent and slightly offset be tween each other high quality aftershock locations show that seismicity is confined within the sedimentary mesozoic cover in the upper 8 km of the crust and that most of the aftershocks are shallower than the largest shocks which nucleated at 6 km depth faults evidenced by aftershock locations have a planar geometry and show increased complexity toward the surface most of the aftershock focal mechanisms are dominated by normal faulting several strike slip events occurred at shallow depths reactivating portions of pre existing thrust planes that segment the normal fault system the spatiotemporal evolution of seismicity shows a peculiar migration of hypocenters along the strike of the main faults with multiple ruptures and the activation of fault segments before the occurrence of the main rupture episodes

seismological geological and geophysical constraints for the gualdo tadino fault umbria marche apennines central italy abstract the april 3 1998 mw 5 1 gualdo tadino earthquake central italy was the last significant event in the 6 month long umbria marche seismic crisis this event and its aftershocks occurred in an area where active faulting produces no striking geological and geomorphological effects in this study we investigated the ruptured fault using detailed seismological data and a re processed and re interpreted seismic reflection profile aftershock location and focal mechanisms were used to constrain the geometry and kinematics of the ruptured fault and a comparison was made with the subsurface image provided by the seismic profile we found that the 1998 gualdo tadino earthquake occurred on a wsw dipping normal fault with a length of about 8 km and a relatively gentle dip 30 40 confined between 3 5 and 7 km in depth kinematics of the mainshock and aftershocks revealed a ne trending extension in agreement with the regional stress field active in the northern apennines belt the mw 5 1 earthquake originated above the top of the basement and ruptured within the sedimentary cover which consists of an evaporites carbonates multilayer we hypothesised that the active fault does not reach the surface blind normal fault

very detailed seismic pattern and migration inferred from the april 2010 pietralunga northern italian apennines micro earthquake sequence abstract we propose a very detailed picture of seismicity that occurred in the proximity of the alto tiberina fault atf northern italian apennines a low angle normal fault by presenting the pattern and evolution of a seismic sequence on the hanging wall of the atf in the first months of 2010 that was characterized by about 1000 events with m l ranging from 0 7 to 3 8 to capture the rupture kinematics of the investigated area a cross correlation technique was initially applied to calculate very accurate time shifts among the events of the sequence and then to relocate them the whole sequence was relocated with the double difference method which includes both absolute travel time measurements and cross correlation differential travel times the new locations confirm that the seismic activity was mainly arranged along a nw se oriented structure that ranged in depth from 4 km to 6 km with dipping towards ne at an angle of ca 65 in comparison with geological data the position of the seismic sequence is compatible with the evaporite triassic layer the main nodal planes are consistent with the spatial evolution of the aftershocks and with the tensional state of stress in the area an analysis of waveform similarity was performed at a reference station by merging the capability of the cross correlation technique and the bridging algorithm the detected mutiplets allow us to emphasize the anisotropic spatial and temporal migrations of the seismicity that occurred along a 307 n strike direction with an averaged propagation velocity of ca 0 4 km day we explain the highlighted anisotropic behavior of the migration with the hypothesized presence of overpressured fluids and with physical properties of triassic evaporites this suggests the importance of such very detailed relocation of weak and micro seismicity for improvement of our knowledge of fault system geometry and its evolution

detailed study of the potentino seismic zone in the southern apennines italy abstract most relevant macroseismic and instrumental data concerning past and current seismic activity of the potentino southern italy have been collected in order to study the seismic behaviour of this area ten among the most important recent and historical earthquakes occurred in the area from 1826 to 1990 have been studied by means of macroseismic methodologies macroseismic fields for all the events indicate a general isoseismal lengthening in the direction of the apennines chain northwest southeast a rapid attenuation of intensity westward of the studied area and a strong propagation eastwards this configuration is strongly dependent on the source mechanisms of the seismic events and the geological dishomogeneities of the concerned areas as regards earthquakes which have been instrumentally recorded in the campania basilicata area from 1980 to 1991 more than 1300 accurate hypocentral locations have been computed for events with m d 2 5 using data from osservatorio vesuviano o v and istituto nazionale di geofisica i n g seismic networks special emphasis is put on the potenza may 5 1990 earthquake m s 5 4 neic national earthquake information center i vii msk which was the strongest recent event in the area and was felt in a large sector of southern italy as regards the seismic sequence following this event about 110 aftershocks with m d 1 9 have been located very close to the town of potenza northeast of it with a clustering type space distribution the occurrence of the events is strongly time concentrated in so defining a main shock aftershocks typical sequence moreover the macroseismic investigation of the main event has allowed to map out isoseismal lines bounding vii vi v and iv msk areas the isoseismals pattern shows that attenuation and amplification of intensity are observed in the same areas as for the previous events beginning from may 26 1991 an increase of seismicity initiated by an earthquake of m l 4 7 neic and i vi vii msk was observed nearly in the same area as the 1990 sequence accurate locations of 84 events with m d 1 9 have been computed however this sequence seems to have a slightly different character from the 1990 one in that events are scattered in time and seismic energy release is comparable to a swarm type seismic sequence as regards the previous sequences fault plane solutions for the highest magnitude events and for appropriate groups of events have been worked out the mechanisms indicate normal faulting motion with t axes oriented orthogonal to the apenninic chain in conclusion detailed analyses on the historical and recent seismicity of the potentino area and adjacent ones have allowed to identify at least four seismogenic zones which show activity with different features such zoning represents a contribution to the seismic hazard assessment in the southern apennines on a regional scale

anomalies of mantle derived helium during the 1997 1998 seismic swarm of umbria marche italy more than 100 he 4he isotope ratios were measured in co2 dominated gas samples collected during the 1997 1998 seismic crisis that shook the umbria marche central apennines italy although the gas emissions were located in a typical crustal environment the measured values delineate variable mixing proportions between mantle derived and crustal helium during the monitoring period anomalous he 4he ratios were observed together with a significant increase of fluid outflows the observed he 4he anomalies appear to be driven by stress induced crustal deformations affecting micro fracturing and bulk permeability and in turn by a seismogenic induced modification of the crustal permeability of rocks since crustal deformations can also occur aseismically the geochemical anomalies must be considered indicators of processes occurring below the surface which could eventually help to estimate the probability increase of an impending earthquake instead of pure empirical precursors

emissivity of terrestrial materials in the 3 5 μm atmospheric window remotely sensed infrared radiance emitted by a surface is a function both of its kinetic temperature and its spectral emissivity consequently assumptions are usually made about the emissivity of earth surface materials to allow their temperatures to be determined or vice versa to increase the accuracy of these assumptions the directional hemispherical spectral reflectance of a wide range of natural earth surface materials has been measured and is summarized here these include igneous metamorphic and sedimentary rocks desert varnish soils vegetation water and ice kirchhoff s law can be used to predict directional spectral emissivity from these data

preseismic creep strains revealed by ground tilt measurements in central italy on the occasion of the 1997 umbria marche apennines earthquake sequence daily averaged tilt component data from four sites of the central apennines italy revealed intermediate term tilts of a few months as possible precursors of the seismic sequence occurred in the umbria marche region during 1997 a change was also observed in the secular tectonic trend recorded at one site and referred to the same seismic sequence the observed intermediate term preseismic tilts are considered as the manifestation of aseismic creep episodes in the fault materials close to the tilt sites the mechanism refers to a strain field slowly propagating from the dilatancy focal area to the tiltmeters through rigid crustal blocks separated by weak transition zones with viscoelastic rheology this propagation is thought to be the cause of the local aseismic fault slip recorded by tiltmeters in one case such creep strains revealed to have larger amplitude and higher frequency content than those accepted for fault materials and this was attributed to an amplified response of the heterogeneous ground surface at the site the existence of a propagating strain field is confirmed by the different onset time delays in the preseismic tilt signals recorded at different distances from the same earthquake in particular the onset time delays observed at each tilt site appear to increase with increasing distance of such site from the epicentral area at greatest distances where the preseismic strain becomes negligible the characteristic intermediate term ground tilts vanish completely

rupture depths and source processes of the 1997 1998 earthquake sequence in central italy abstract the focal depths and the rupture processes of four moderate earthquakes which occurred in central italy during 1997 and 1998 are investigated using broadband teleseismic data the earthquakes the largest with m w 6 0 caused significant damage in the epicentral area and are part of an unusual sequence of moderate sized earthquakes to strike the central apennines for three of the events the waveforms are found to be consistent with seismic ruptures confined to the top 5 to 7 km of the crust directivity effects are evident in the waveforms of the largest earthquake and waveform inversion suggests an upward rupture with a horizontal component oriented toward the north one earthquake m w 5 2 is confirmed from waveform modeling to have occurred at 50 km depth this is the first event of this magnitude to have been located in the mantle beneath the apennines

the rocks of gusev crater as viewed by the mini tes instrument 1 the miniature thermal emission spectrometer mini tes on board the mars exploration rover spirit is part of a payload designed to investigate whether a lake once existed in gusev crater mini tes has observed hundreds of rocks along the rover s traverse into the columbia hills yielding information on their distribution bulk mineralogy and the potential role of water at the site although dust in various forms produces contributions to the spectra we have established techniques for dealing with it all of the rocks encountered on the plains traverse from the lander to the base of the columbia hills share common spectral features consistent with an olivine rich basaltic rock known as adirondack class beginning at the base of the west spur of the columbia hills and across its length the rocks are spectrally distinct from the plains but can be grouped into a common type called clovis class these rocks some of which appear as in place outcrop are dominated by a component whose spectral character is consistent with unaltered basaltic glass despite evidence from other rover instruments for significant alteration the northwest flank of husband hill is covered in float rocks known as wishstone class with spectral features that can be attributed uniquely to plagioclase feldspar a phase that represents more than half of the bulk mineralogy rare exceptions are three classes of basaltic exotics found scattered across husband hill that may represent impact ejecta and or float derived from local intrusions within the hills the rare outcrops observed on husband hill display distinctive spectral characteristics the outcrop called peace shows a feature attributable to molecular bound water and the outcrop that hosts the rock called watchtower displays a dominant basaltic glass component despite evidence from the rover s payload for significant alteration of some of the rocks no unambiguous detection of crystalline phyllosilicates or other secondary silicates has been observed by mini tes the mineralogical results supplied by mini tes provide no clear evidence that a lake once existed in gusev crater

intermittent slip along the alto tiberina low angle normal fault in central italy the alto tiberina normal fault atf in central italy is a 50 km long crustal structure that deepens at a low angle 15 20 events on the fault plane are about ten times less than those located i

thermal infrared 2 5 13 5 μm spectroscopic remote sensing of igneous rock types on particulate planetary surfaces fundamental molecular vibration bands are significantly diminished by scattering thus such bands in spectra of fine particulate regoliths i e dominated by 5 m particles or regoliths displaying a similar scale of porosity are difficult to use for mineralogical or rock type identification consequently other spectral features have been sought that may be more useful in spectroscopic remote sensing of composition we find that mineralogical information is retained in overtones and combination tones of the fundamental molecular vibrations in the 3 0 to 7 0 m region but that relatively few minerals have a sufficiently distinctive band structure to be unambiguously identified with currently available techniques more significantly identification of general rock type as defined by the scfm chemical index scfm sio2 sio2 cao feo mgo is possible using spectral features associated with the principal christiansen frequency and with a region of relative transparency between the si o stretching and bending bands however environmental factors may affect the appearance and wavelengths of these features finally prominent absorption bands may result from the presence of relatively small amounts of water hydroxyl or carbonate because absorption bands exhibited by these materials in the 2 7 to 4 0 m region where silicate spectra are otherwise featureless increase strongly in spectral contrast with decreasing particle size such materials are thus detectable in very small amounts in a particulate regolith composed predominantly of silicate minerals

analysis of the 9 september 1998 mw 5 6 mercure earthquake sequence southern apennines italy a multidisciplinary approach abstract the mercure earthquake mw 5 6 of september 9 1998 and the associated aftershocks occurred in a small pleistocene holocene continental basin of the southern apennines in a region of low instrumental and moderate historical seismicity seismological photogeological and field survey data were analyzed and integrated in order to identify the likely seismogenic structure to depict its 3 d geometry and kinematics and to provide further constraints to the seismogenic potential of the rupture processes in the study area the mainshock occurred at the nw edge of the seismic sequence 40 03 n and 15 95 at a depth of 10 5 1 5 km the aftershocks volume was determined from the relocation of about 200 events 1 1 ml 3 9 registered by local networks from september 10 to october 12 1998 the relocation procedure was based on choosing p and s waves for all the events and the definition of ten 9 layers velocity models appropriate for the different stations the kinematics of the seismogenic deformation was defined through the computation of 36 well constrained focal mechanisms the seismological and geological stress tensors were determined through inversion of focal mechanisms and fault slip data both of them resulted in the tensional type with ene wsw and ne sw trending 3 axis respectively the map and the section distribution of the aftershocks sequence depicts an average nw se striking and 60 sw dipping seismogenic volume most of the events 80 were located at depths between 3 and 8 km in the footwall of the mercure basin mbb boundary fault but along the possible down dip continuation of a previously unidentified n120 e striking and wsw dipping holocene normal fault alignment which extends from castello seluci to piana perretti and timpa della manca cpst fault a small percentage of events 10 were located at depths between 10 and 12 km where the cpst seismogenic fault may detach the reconstructed rupture area ra of the mercure 1998 earthquake has an along strike length l of about 9 km and a down dip width w of about 9 km yielding a total area of approximately 81 km 2 on the other hand the l and w dimension of the entire individual seismogenic structure identified as responsible for the earthquake e g the cpst fault are about 19 and 12 km respectively with a consequent ra of about 230 km 2 this may imply a maximum magnitude mw equal to 6 3 which lead us to compare the mercure area in terms of seismogenic hazard to the adjacent pollino castrovillari area where strong paleoseismological events are documented

a low magnitude seismic sequence near isernia molise central italy in january 1986 following the increase in seismic activity which occurred near isernia molise central italy in january 1986 a digital seismic network of four stations with three component short period seismometers was installed in the area by the osservatorio vesuviano the temporary network had an average station spacing of about 8 10 km and in combination with permanent local seismic stations allowed the accurate determination of earthquake locations during an operating period of about one month among the 1517 detected earthquakes 170 events were selected with standard errors on epicentre and depth not greater than respectively 0 5 and 1 5 km the most frequent focal depths ranged between 4 and 8 km while the epicentres distribution covered a small area ne of isernia of about 10 km2 a main rupture zone could not be clearly identified from the spatial distribution of the earthquakes suggesting a rupture mechanism involving heterogeneous materials the activity was characterized by low energy levels the largest earthquake on january 18 1986 havingmd 4 0 the time sequence of events and pattern of seismic energy release revealed a strong temporal clustering of events similar to the behaviour commonly associated with seismic swarms

stochastic simulation of strong motion records from the 26 september 1997 mw 6 umbria marche central italy earthquake we simulated the strong motion time histories recorded during the main shock m w 6 0 of the umbria marche seismic sequence central italy of september october 1997 ground motion waveforms were computed using the stochastic modeling technique proposed by beresnev and atkinson 1997 1998 for finite faults in this approach the high frequency amplitudes are simulated as a summation of stochastic point sources we used the finsim code beresnev and atkinson 1998 which incorporates regional attenuation and frequency dependent site amplification factors we divided the fault plane into 60 elements whose length and width are 1 2 km and 1 5 km respectively the resulting subfault corner frequency and rise time are 0 91 hz and 0 5 sec we found that the site amplification functions play an important role in the simulation process improving the fit to the observed time histories and spectra the strong motion waveforms recorded at the nocera noc station located at the northern end of the causative fault show an important directivity effect thus to fit the observed ground motions we used an inhomogeneous slip distribution weighting the slip on the fault heavier toward the north we tested two models one that simulates a fault rupture with two main slip patches and a second model that ruptures northward with a less heterogeneous slip distribution where slip is mostly concentrated near the rupture nucleation at the southern edge of the fault plane the simulated low frequency amplitudes at noc however require an additional frequency dependent directivity correction e g bernard et al 1996 in conclusion we found that stochastic finite fault simulations calculated using adequate site amplification functions and crustal attenuation reproduce reasonably well the ground motions from the m w 6 0 umbria marche earthquake

a decade of passive seismic monitoring experiments with local networks in four italian regions we report on four seismic monitoring experiments that in the past ten years we carried out with dense local networks in seismically active italian areas where for at least a year tens of three component seismic stations were set up to record microseismicity the areas observed are alpago cansiglio located in the venetian alps citta di castello in the northern apennines marsica in the central apennines and val d agri located in the southern apennines we produced homogeneous catalogues regarding earthquake locations and local magnitudes to investigate seismicity patterns during an inter seismic period the four regions are characterised by different kinematics strain rates and historical recent seismicity we investigate earthquake distribution in space time and size obtaining reference seismic rates and parameters of the gutenberg and richter law we declustered the catalogues to look for coherent signs in the background seismic activity despite a difference in the catalogues magnitudes of completeness due both to the diverse detection threshold of the local networks and different seismic release we detect and observe two common main behaviours a the alpago cansiglio and marsica regions are characterised by a relatively lower rate of seismic release associated to the episodic occurrence of seismic sequences with the largest event being 3 ml 4 in these areas the seismicity is not localised around the main faults b the citta di castello and val d agri regions have a relatively high rate of seismicity release almost continuously with time and the increase in earthquake production is not clearly related to seismic sequences in these areas the seismicity nucleates around defined fault systems and is usually lower than ml 3 we suggest that the presence of over pressured fluids in the citta di castello and val d agri uppermost crustal volume may favour and mould the higher rate of microseismic release

the inverse problem in microtectonics and the separation of tectonic phases abstract the algorithm of inverse problems is applied to three cases in microtectonics a collection of striations measured on pre existing faults may be processed automatically and interpreted in terms of tectonic stress a comparison is made between two different methods formerly proposed by the authors both methods are tested with field data the theoretical results agree with independent field criteria for a separation of tectonic phases

seismic moment summation for historical earthquakes in italy tectonic implications tectonic deformation rates in and around the apennine mountains of italy are studied using seismic moments estimated from macroseismic effects of historical earthquakes northeastward extension in the northern apennines north of 42 5 n accompanies shortening along their northeast flank since the seventeenth century the sparse seismicity in these two zones has included no earthquake with magnitude 6 5 or seismic moment above 6 1018 n m their spatially averaged deformation rates are only 0 3 mm yr 1 but are equal such that the extension and shortening balance with no relative motion between their external surroundings in contrast the numerous historical earthquakes in the central and southern apennines with magnitude 7 and seismic moment 20 1018 n m require northeastward relative velocity across the deforming zone up to 5 mm yr 1 matching the expected relative motion of their surroundings this relative velocity is taken up in part by extension and in part by strike slip depending on the trend of the deforming zone and is not accompanied by en echelon shortening elsewhere in italy the northern apennines thus show different senses and rates of deformation from localities farther south and are thus technically distinct at present in contrast with previous interpretations

fault fragment control in the 1997 umbria marche central italy earthquake sequence the umbria marche region in central italy experienced a sequence of shallow earthquakes in late 1997 including three mainshocks on september 26th ms 5 5 and 5 9 and october 14th ms 5 5 this seismic sequence illustrates the relationships between small scale active faults and moderate magnitude earthquakes we suggest that a small scale active fault corresponds to a fault fragment and that it refers to the fault area required for producing a coseismic deformation at the ground surface the seismic activity and related three mainshocks occurred along three fault fragments which total 25 km in length and show a listric geometry at depth fault fragments are laterally controlled by pre existing transverse fold and thrust structures and may constitute a major component of the seismic strain release in active continental regions

empirical relationships between aftershock area dimensions and magnitude for earthquakes in the mediterranean sea region fault dimension estimates derived from the aftershock area extent of 36 shallow depth v31 km earthquakes that occurred in the mediterranean sea region have been used in order to establish empirical relationships between length width area and surface wave moment magnitude this dataset consists of events whose aftershock sequence was recorded by a dense local or regional network and the reported location errors did not exceed on average 3 5 km surface wave magnitudes for these events were obtained from the neic database and or published reports while moment magnitudes as well as focal mechanisms were available from the harvard usgs catalogues contrary to the results of some previously published studies we found no evidence in our dataset that faulting type may have an effect on the fault dimension estimates and therefore we derived relationships for the whole of the dataset comparisons by means of statistical f tests of our relationships with other previously published regional and global relationships were performed in order to check possible similarities or differences most such comparisons showed relatively low significance levels b95 since the differences in source dimension estimates were large mainly for magnitudes lower than 6 5 becoming smaller with increasing magnitude some degree of similarity however could be observed between our fault length relationship and the one derived from aftershock area lengths of events in greece while a difference was found between our regional and global fault length relationships a calculation of the ratio defined as the fault length derived from our relationships to the length estimated from regional empirical relationships involving surface ruptures showed that it can take a maximum value of about 7 for small magnitudes while it approaches unity at ms 7 2 when calculating the same ratio using instead global empirical relationships we see the maximum value not exceeding 1 8 while unity is reached at mw 7 8 indicating the existence of a strong regional variation in the fault lengths of earthquakes occurring in the mediterranean sea region also a relationship between the logarithms of the rupture area and seismic moment is established and it is inferred that there is some variation of stress drop as a function of seismic moment in particular it is observed that for magnitudes

comparison between reprocessed seismic profiles seismologic and geologic data a case study of the colfiorito earthquake area seismic reflection data are used to reconstruct the subsurface geologic structures below the umbria marche region in italy a highly seismogenic area with a recent history of seismic activity the 1997 1998 colfiorito sequence we reprocess three vibroseis seismic profiles acquired in the early 1980s for hydrocarbon exploration whose stacked sections were optimized for relatively deep oil targets on the reprocessed seismic profile closest to the epicentral area we construct the main reflectors to a depth of about 4 s two way time and compare this interpretation with the available hypocenters of the 1997 earthquakes the improvements in visualizing the shallow and deep reflections provide a better correlation between the reflectors and the observed surface structures as well as a better delineation of the basement rock geometry we find that part of the colfiorito sequence is localized around some of the reflectors in the reflection profile which we interpret as related to the active normal faults

connecting seismically active normal faults with quaternary geological structures in a complex extensional environment the colfiorito 1997 case history northern apennines italy 1 the northern apennines of italy are characterized by a complex tertiary tectonic history where superposed compressional and extensional deformation occurred in such regions characterized by low active extensional strain rate the coseismic surface ruptures are rare and often a matter of much debate resulting in a difficult connection between geological faults i e faults which can be mapped at the surface and seismological faults i e faults which actually generate earthquakes the availability of detailed geological mapping and high resolution seismological data for the colfiorito area struck in 1997 by a sequence of six 5 mw 6 normal faulting earthquakes allow us to compare and verify the existence of geometric and kinematic correspondence between the mapped geological quaternary faults and the activated structures in map view the earthquakes distribution reflects the fault pattern mapped at the surface the length of activated and mapped faults is quite similar 7 10 km the coseismic subsided region imaged by interferometric synthetic aperture radar data is located in the hanging wall of the mapped normal faults that bound the quaternary basins in section view there is a geometric connection between mapped normal faults and the aftershock alignments used to image fault geometry at depth comparison of striated fault planes and aftershock focal mechanism solutions show a strong kinematic consistency this study points out that the quaternary tectonosedimentary evolution and the present day geological and geomorphologic setting of the colfiorito area can be interpreted as the result of repeated extensional earthquakes similar to the 1997 events occurring on nw se trending normal faults our data also show that the main shocks of the colfiorito sequence nucleated close to the intersections between the normal faults and the preexisting compressional transpressional structures which in 1997 acted as lateral barriers to rupture propagation and consequently constrained the fault size

the gubbio normal fault central italy geometry displacement distribution and tectonic evolution abstract normal faults within orogenic belts can be pre syn or post orogenic features we studied the gubbio normal fault central italy which is an example of a pre orogenic fault reactivated in a post orogenic stage the gubbio fault is a 22 km long fault bordering a quaternary basin and part of an active faults system in the umbria marche region central italy the interpretation of a set of seismic profiles enables us to reconstruct the fault geometry in detail and to measure displacement and throw distributions along the fault strike seismic data indicate that the gubbio fault represents an example of multiple reactivation at least a portion of the fault was active in the miocene and only a part of the total displacement was achieved in the quaternary the reconstruction of the fault geometry at depth shows that the fault is characterised by listric geometry the fault is also characterised by a bend along strike and structure contours show that this geometry is maintained at depth as the fault is commonly addressed as presently active the maximum fault dimensions are correlated to the maximum expected earthquake and the presence of the fault bend is discussed as a possible barrier to seismic ruptures propagation

spectral reflectance characterization 0 4 to 2 5 and 8 0 to 12 0 mu m of phanerozoic strata wind river basin and southern bighorn basin areas wyoming abstract reflectance spectroscopy a useful analytical tool available to geologists for over 100 years has not been widely used in petrologic or stratigraphic studies of sedimentary rocks we are routinely using laboratory spectral reflectance data covering the 0 4 to 12 0 m wavelength interval in an investigation of the stratigraphic and structural evolution of the wind river and bighorn basin areas wyoming two types of laboratory spectral reflectance measurements were made on 192 weathered outcrop bedrock and core samples 1 hemispherical reflectance from 0 4 to 2 5 m 229 spectra and 2 biconical reflectance from 8 0 to 12 0 m 84 spectra results show stratigraphic variations in the spectral properties of sedimentary rocks as encountered in the field sample mineralogy was determined using x ray diffraction and interpretation of spectra the mineralogy lithology and stratigraphic distribution of samples are diverse and representative of phanerozoic siliciclastic and carbonate strata encountered in foreland sedimentary basins spectra were sorted into 36 distinct groups according to the presence or absence of 68 visible and infrared reflectance features many spectral features can be assigned to specific molecular phenomena and allow rapid determination of specific minerals minerals detectable spectrally include gypsum kaolinite smectite analcime goethite jarosite calcite dolomite and feldspar results are contributing to our understanding of the depositional history of the wind river and bighorn basin areas more importantly results suggest that laboratory field and remote reflectance spectroscopy have more general geologic applicability in studies of sedimentary rocks reflectance spectroscopy can augment conventional laboratory and field methods for petrologic analysis correlation interpretation of depositional environments and construction of facies models

insights on the seismogenic layer thickness from the upper crust structure of the umbria marche apennines central italy 1 we reconstruct the subsurface geology in a region of the northern apennines central italy where a protracted extensional sequence occurred in 1997 1998 with maximum magnitude m 6 0 our study is mainly based on the interpretation of three reprocessed seismic reflection profiles crossing the epicentral area which constrain the subsurface geometry to a depth of about 12 km where most of the shallow seismicity occurs comparing the subsurface setting with accurately determined earthquake locations we find that the seismicity is located entirely within the sedimentary cover and does not penetrate the underlying basement this is explained by considering that the sedimentary cover is rather thick and composed of relatively strong lithologies platform carbonates and evaporites while the upper part of the basement consists of weak phyllites and siliciclastic rocks this weak horizon is also evidenced by the low vp values measured in deep wells of the region its effect is to decouple the sedimentary cover from the crystalline basement where only microseismicity occurs our study indicates that local structure and stratigraphy can significantly influence the distribution of seismicity within the upper crust particularly in complex geological environments such as thrust and fold belts

inversion of source parameters from near and far field observations an application to the 1915 fucino earthquake central apennines italy we use a nonlinear inversion approach for determining source parameters of the fucino m s 6 9 earthquake that occurred along central apennines italy in 1915 taking into account both near field surface deformations and far field first motion polarities this event was one of the most destructive in italy this century causing over 30 000 casualties altitude and leveling measurements were performed before 1862 and after 1917 the event along a circular route consisting of 18 benchmarks polarities of first arrivals do not constrain a unique fault plane solution while the one obtained by inverting geodetic data with relevant constraints provided by neotectonic data disagrees with p wave polarities our joint inversion based on a robust fitting technique has resulted in only one well defined solution satisfying geophysical data as well as surface faulting distribution and paleoseismological information

vertical distribution of precipitation particles in baiu frontal stratiform intense rainfall around okinawa island japan the vertical distribution of precipitation particles in an intensely precipitating stratiform cloud associated with the baiu front around okinawa island was observed x band polarimetric radar disdrometer and hydrometeor videosonde data were used to examine the precipitation processes the cloud top was approximately 12 km above sea level as convection was depressed while stratiform regions developed near okinawa island in the rain region below 3 km the mean median volume diameter of the raindrop size distribution dsd estimated from the radar variables was 1 55 mm and the mean normalized intercept parameter was 104 12 mm 1 m 3 with a mean radar reflectivity of 40 5 dbze the dsd indicates that the stratiform precipitation was characterized by higher number concentrations of smaller drops than observed previously in convective cells in a baiu frontal convective precipitation region around okinawa island the dsd also suggests the presence of larger raindrops than in convective cells embedded in a baiu frontal stratiform precipitation region around okinawa island in the ice region at 5 6 km just above the melting layer and 6 km below the cloud top the differential reflectivity and specific differential phase showed positive values and videosonde measurements revealed that the number concentration of column plate and capped column like crystals maximum dimensions of 0 1 mm was 112 l 1 the high number concentration of these crystals contributed to the intense stratiform rainfall associated with the baiu front

regional patterns of tectonic stress in europe nearly 1500 stress orientation determinations are now available for europe the data come from earthquake focal mechanisms overcoring measurements well bore breakouts hydraulic fracturing measurements and young fault slip studies and sample the stress field from the surface to seismogenic depths three distinct regional patterns of maximum compressive horizontal stress shmax orientation can be defined from these data a consistent nw to nnw shmax stress orientation in western europe a wnw ese shmax orientation in scandinavia similar to western europe but with a larger variability of shmax orientations and a consistent e w shmax orientation and n s extension in the aegean sea and western anatolia the different stress fields can be attributed to plate driving forces acting on the boundaries of the eurasian plate locally modified by lithospheric properties in different regions on average the orientation of maximum stress in western europe is subparallel to the direction of relative plate motion between africa and europe and is rotated 17 clockwise from the direction of absolute plate motion the uniformly oriented stress field in western europe coincides with thin to medium lithospheric thickness approximately 50 90 km and high heat flow values 80 m w m2 in western europe a predominance of strike slip focal mechanisms implies that the intermediate principal stress is vertical the more irregular horizontal stress orientations in scandinavia coincide with thick continental lithosphere 110 170 km and low heat flow 50 m w m2 the cold thick lithosphere in this region may result in lower mean stresses associated with far field tectonic forces and allow the stress field to be more easily perturbed by local effects such as deglaciation flexure and topography the stress field of the aegean sea and western anatolia is consistent with n s extension in a back arc setting behind the hellenic trench subduction zone the stress field is influenced in places by regional geologic structures e g in the western alps where shmax directions show a slight tendency toward a radial stress pattern not all major geologic structures however appear to affect the shmax orientation e g in the vicinity of the rhine rift system horizontal stress orientations are continuous

contemporary crustal extension in the umbria marche apennines from regional cgps networks and comparison between geodetic and seismic deformation abstract here we report the results of the analysis of a gps velocity field in the umbria marche apennines central italy obtained from the integration of diverse geodetic networks the velocity field obtained shows a high degree of consistency both spatially and in terms of comparison with independent information despite the limited time span of some gps stations starting from the velocity field we derive a continuous strain rate field applying a spline interpolation technique which provide a smooth estimate of the deformation field the main feature of the resulting strain rate field is a continuous high 50 nanostrain year strain rate belt coincident with the area of largest historical and instrumental seismic release the model directions of the principal axes agree with geological and seismological information indicating ne sw extension we transform the strain rate field into geodetic moment rate using the kostrov formula to evaluate the potential seismic activity of the region and compare it with actual seismic release in the last 720 years from mw 5 5 earthquakes this comparison highlights a large possible deficit in the seismic release with respect to the overall potential seismic activity particularly concentrated in the northern part of the study area this discrepancy can be resolved with either a large amount of seismicity to be released in the near future or significant aseismic slip and deformation

is the adriatic an african promontory seismicity patterns and fault plane solutions for the largest recent earthquakes in the adriatic region are used to test the hypothesis that the adriatic is a promontory of the african continental mass the horizontal projections of the slip vectors for the 24 best constrained focal mechanisms trend at a high angle to those predicted for the africa eurasia collision and so the adriatic cannot be thought of as a promontory of africa the slip vectors define an instantaneous pole of rotation that describes anticlockwise rotation of the adriatic relative to eurasia the adriatic is a stable continental block moving within the broad zone of deformation between africa and eurasia