early holocene greenland ice mass loss likely triggered earthquakes and tsunami abstract due to their large mass ice sheets induce significant stresses in the earth s crust stress release during deglaciation can trigger large magnitude earthquakes as indicated by surface faults in northern europe although glacially induced stresses have been analyzed in northern europe they have not yet been analyzed for greenland we know that the greenland ice sheet experienced a large melting period in the early holocene and so here we analyze glacially induced stresses during deglaciation for greenland for the first time instability occurs in southern greenland where we use a combined analysis of past sea level indicators and a model of glacially induced fault reactivation to show that deglaciation of the greenland ice sheet may have caused a large magnitude earthquake or a series of smaller magnitude earthquakes around 10 600 years ago offshore south western greenland the earthquake s may have shifted relative sea level observations by several meters if the earthquake induced stress release was created during a single event it could have produced a tsunami in the north atlantic ocean with runup heights of up to 7 2 m in the british isles and up to 7 8 m along canadian coasts

temporal changes of shallow seismic velocity around the karadere duzce branch of the north anatolian fault and strong ground motion we analyze temporal variations of seismic velocity along the karadere duzce branch of the north anatolian fault using seismograms generated by repeating earthquake clusters in the aftershock zones of the 1999 mw7 4 izmit and mw7 1 duzce earthquakes the analysis employs 36 sets of highly repeating earthquakes each containing 4 18 events the events in each cluster are relocated by detailed multi step analysis and are likely to rupture approximately the same fault patch at different times the decay rates of the repeating events in individual clusters are compatible with the omori s law for the decay rate of regional aftershocks a sliding window waveform cross correlation technique is used to measure travel time differences and evolving decorrelation in waveforms generated by each set of the repeating events we find clear step like delays in the direct s and early s coda waves sharp seismic velocity reduction immediately after the duzce main shock followed by gradual logarithmic type recoveries a gradual increase of seismic velocities is also observed before the duzce main shock probably reflecting post seismic recovery from the earlier izmit main shock the temporal behavior is similar at each station for clusters at various source locations indicating that the temporal changes of material properties occur in the top most portion of the crust the effects are most prominent at stations situated in the immediate vicinity of the recently ruptured fault zones and generally decrease with normal distance from the fault a strong correlation between the co seismic delays and intensities of the strong ground motion generated by the duzce main shock implies that the radiated seismic waves produced the velocity reductions in the shallow material

seismic guided waves trapped in the fault zone of the landers california earthquake of 1992 a mobile seismic array of seven stations was deployed at 11 sites along the fault trace of the m7 4 landers earthquake of june 28 1992 with a maximum offset of 1 km from the trace we found a distinct wave train with a relatively long period following the s waves that shows up only when both the stations and the events are close to the fault trace this wave train is interpreted as a seismic guided wave trapped in a low velocity fault zone to study the distribution of amplitude of the guided waves with distance from the fault trace and also their attenuation with travel distance along the fault zone we eliminated source and recording site effects by the coda normalization method the normalized amplitudes of guided waves show a spectral peak at 3 4 hz which decays sharply with distance from the fault trace spectral amplitudes at high frequencies 8 15 hz show an opposite trend increasing with distance from the fault trace the normalized amplitudes of guided waves at 3 4 hz also show a systematic decrease with hypocentral distance along the fault zone from which we infer an apparent q of 50 in order to confirm the existence of the guided waves a dense array of 31 stations was deployed at one of the 11 sites the resultant records revealed unequivocal evidence for the existence of guided waves associated with the fault zone by modeling the waveforms as s waves trapped in a low velocity waveguide sandwiched between two homogeneous half spaces with velocity vs 3 0 km s we infer a waveguide width of about 180 m a shear velocity of 2 0 2 2 km s and a q of 50 hypocenters of aftershocks with clear guided waves show a systematic distribution both laterally and with depth delineating the extent of the low velocity fault zone in three dimensions we find that the zone extends to a depth of at least 10 km this zone apparently continues to the south across the pinto mountain fault because guided waves are observed at stations north of the pinto mountain fault for earthquakes with epicenters south of it on the other hand the zone appears to be discontinuous at the fault bend located about 20 km north of the mainshock epicenter guided waves were observed for stations and epicenters which are located on the same sides of the fault bend but not for those on the opposite sides

geological observations of damage asymmetry in the structure of the san jacinto san andreas and punchbowl faults in southern california a possible indicator for preferred rupture propagation direction we present new in situ observations of systematic asymmetry in the pattern of damage expressed by fault zone rocks along sections of the san andreas san jacinto and punchbowl faults in southern california the observed structural asymmetry has consistent manifestations at a fault core scale of millimeters to meters a fault zone scale of meters to tens of meters and related geomorphologic features the observed asymmetric signals are in agreement with other geological and geophysical observations of structural asymmetry in a damage zone scale of tens to hundreds of meters in all of those scales more damage is found on the side of the fault with faster seismic velocities at seismogenic depths the observed correlation between the damage asymmetry and local seismic velocity structure is compatible with theoretical predictions associated with preferred propagation direction of earthquake ruptures along faults that separate different crustal blocks the data are consistent with a preferred northwestward propagation direction for ruptures on all three faults if our results are supported by additional observations asymmetry of structural properties determined in field studies can be utilized to infer preferred propagation direction of large earthquake ruptures along a given fault section the property of a preferred rupture direction can explain anomalous behavior of historic rupture events and may have profound implications for many aspects of earthquake physics on large faults

wavefield polarization in fault zones of the western flank of mt etna observations and fracture orientation modelling ambient noise measurements performed on the western flank of mt etna are analyzed to infer the occurrence of directional amplification effects in fault zones the data were recorded along short 500 m profiles crossing the ragalna fault system ambient noise records were processed to compute the horizontal to vertical noise spectral ratio as a function of frequency and direction of motion wavefield polarization was investigated in the time frequency domain as well peaks of the spectral ratios generally fall in the frequency band 1 0 6 0 hz pointing out directional amplifications that are also confirmed by the results of the time frequency analysis the largest amplification occurring with high angle to the fault strike a variation of the frequency of the spectral peak is observed between the two sides of the fault possibly related to a damage fault asymmetry measurements performed several kilometers away from the fault zone do not show behavior that is as systematic as in the fault zone and this suggests that the observed directional effects can be ascribed to the fault fabric we relate the polarization effect to compliance anisotropy in the fault zone where the presence of predominantly oriented fractures makes the normal component of ground motion larger than the transversal one in order to test the direction and the type of fractures that are expected in the fault zone we modeled the brittle deformation pattern of the investigated fault theoretical results are in good agreement with field observations of the fracture strike

wet fault or dry fault a laboratory approach to remotely monitor the hydro mechanical state of a discontinuity using controlled source seismics stress variation and fluid migration occur in deformation zones which are expected to affect seismic waves reflected off or propagating across such structures we developed a basic experimental approach to monitor the mechanical coupling with respect to seismic coupling across a single discontinuity between a granite sample in contact with a steel platen piezoceramics located on the platen were used to both generate and record the p and s wave fields reflected off the discontinuity at normal incidence this way normal b n and tangential b t compliances were calculated using schoenberg s linear slip theory schoenberg j acoust soc am 68 1516 1521 1980 when the roughness the effective pressure p eff up to 200 mpa and the nature of the filling gas or water vary we observe that increasing the effective pressure decreases b n and b t which is interpreted as the effect of the closure of the voids at the interface permitting more seismic energy to be transmitted across the interface values of b n are significantly higher than those of b t at low p eff 60 80 mpa in dry conditions and significantly drop under water saturated conditions the water filling the voids therefore helps to transmit the seismic energy of compressional waves across the interface these results show that the assumption b n b t commonly found in some theoretical approaches does not always stand the ratio b n b t actually reflects the type of saturating fluids and the effective pressure in agreement with other experimental studies however we illustrate that only the relative variations of this ratio seem to be relevant not its absolute value as suggested in previous studies consequently the use of b n against b t plots may allow effective pressure variation and the nature of the pore fluid to be inferred in this respect this experimental approach at sample scale helps to pave the way for remotely monitoring in the field the hydro mechanical state of deformation zones such as seismogenic faults fractured reservoirs or lava conduits

evidences for strong directional resonances in intensely deformed zones of the pernicana fault mount etna italy 1 in this paper we investigate ground motion properties in the western part of the pernicana fault this is the major fault of mount etna and drives the dynamic evolution of the area in a previous work rigano et al 2008 showed that a significant horizontal polarization characterizes ground motion in fault zones of mount etna both during earthquakes and ambient vibrations we have performed denser microtremor measurements in the ne rift segment and in intensely deformed zones of the pernicana fault at piano pernicana this study includes mapping of azimuth dependent horizontal to vertical spectral ratios along and across the fault frequency wave number techniques applied to array data to investigate the nature of ambient vibrations and polarization analysis through the conventional covariance matrix method our results indicate that microtremors are likely composed of volcanic tremor spectral ratios show strong directional resonances of horizontal components around 1 hz when measurements enter the most damaged part of the fault zone their polarization directions show an abrupt change by 20 to 40 at close measurements between the northern and southern part of the fault zone recordings of local earthquakes at one site in the fault zone confirm the occurrence of polarization with the same angle found using volcanic tremor we have also found that the directional effect is not time dependent at least at a seasonal scale this observation and the similar behavior of volcanic tremors and earthquake induced ground motions suggest that horizontal polarization is the effect of local fault properties however the 1 hz resonant frequency cannot be reproduced using the 1 d vertically varying model inferred from the array data analysis suggesting a role of lateral variations of the fault zone although the actual cause of polarization is unknown a role of stress induced anisotropy and microfracture orientation in the near surface lavas of the pernicana fault can be hypothesized consistently with the sharp rotation of the polarization angle within the damaged fault zone

influence of outcrop scale fractures on the effective stiffness of fault damage zone rocks we combine detailed mapping and microstructural analyses of small fault zones in granodiorite with numerical mechanical models to estimate the effect of mesoscopic outcrop scale damage zone fractures on the effective stiffness of the fault zone rocks the bear creek fault zones were active at depths between 4 and 15 km and localize mesoscopic off fault damage into tabular zones between two subparallel boundary faults producing a fracture induced material contrast across the boundary faults with softer rocks between the boundary faults and intact granodiorite outside the boundary faults using digitized fault zone fracture maps as the modeled fault geometries we conduct nonlinear uniaxial compression tests using a novel finite element method code as the experimental laboratory apparatus map measurements show that the fault zones have high nondimensional facture densities 1 and damage zone fractures anastamose and intersect making existing analytical effective medium models inadequate for estimation of the effective elastic properties numerical experiments show that the damage zone is strongly anisotropic and the bulk response of the fault zone is strain weakening normal strains as small as 2 can induce a reduction of the overall stiffness of up to 75 fracture induced effective stiffness changes are large enough to locally be greater than intact modulus changes across the fault due to juxtaposition of rocks of different lithologies therefore mesoscopic fracturing is as important as rock type when considering material or bimaterial effects on earthquake mechanics these results have important implications for earthquake rupture mechanics models because mesoscopic damage zone fractures can cause a material contrast across the faults as large as any lithology based material contrast at seismogenic depths and the effective moduli can be highly variable during a single rupture event

evidence of multiple strain fields beneath the eastern flank of mt etna volcano sicily italy deduced from seismic and geodetic data during 2003 2004 we carried out a study of the seismicity and ground deformation occurring on mt etna volcano after the end of the 2002 2003 eruption and before the onset of the 2004 2005 eruption data were recorded by the permanent local seismic network run by istituto nazionale di geofisica e vulcanologia sezione di catania and by geodetic surveys carried out in july 2003 and july 2004 on the gps network most earthquakes were grouped in two main clusters located in the northeastern and southeastern sectors of the volcano the areal distribution of seismic energy associated with the recorded earthquakes allowed us to highlight the main seismogenic areas of mt etna in order to better understand the kinematic processes of the volcano 3d seismic locations were used to compute fault plane solutions and a selected dataset was inverted to determine stress and strain tensors the focal mechanisms in the northeastern sector show clear left lateral kinematics along an e w fault plane consistent with events occurring along the pernicana fault system the fault plane solutions in the southeastern sector show mainly right lateral kinematics along a nne and ene fault plane and left lateral kinematics along nw fault planes that together suggest roughly e w oriented compression surface ground deformation affecting mt etna measured by gps surveys highlighted a marked inflation during the same period and exceptionally strong seawards motion of its eastern flank the 2d geodetic strain tensor distribution was calculated and the results show mainly ene wsw extension coupled with wnw ese contraction indicating right lateral shear along a nw se oriented fault plane the different deformation of the eastern sector of the volcano as measured by seismicity and ground deformation must be interpreted by considering the different depths of the two signals seismic activity in the southeastern sector of volcano is located between 3 and 8 km b s l and can be associated with a very strong additional e w compression induced by a pressurizing source just westwards and at the same depth located by inverting gps data ground deformation in contrast is mainly affected by the shallower dynamics of the fast moving eastern flank which produces a shallower opposing e w extension the entire dataset shows that two different processes affect the eastern flank at the same time but at different depths the boundary is clearly located at a depth of 3 km b s l and could represent the decollement surface for the mobile flank

large amplitude variations recorded by an on fault seismological station during the l aquila earthquakes evidence for a complex fault induced site effect 1 a station fagn installed on a segment of the fault system that generated the april 2009 l aquila earthquakes shows larger ground motions compared to nearby stations spectral ratios using 304 earthquakes result in a station amplification significantly varying event by event in the frequency band 1 8 hz the resulting pattern of amplitude dependence on causative earthquake location reveals that the strongest up to a factor of 10 amplifications occur for tightly clustered aftershocks aligned with the fault dip beneath fagn thus indicating a fault guided effect fault models are investigated in a grid search approach by varying velocity q width and depth of the fault zone although the problem solution is not unique and there are strong trade offs among the model parameters constraints from observations yield a deep trapping structure model where the most likely values of velocity reduction q and damage zone width are 25 20 and 280 m respectively

seismic trapped modes in the oroville and san andreas fault zones three component borehole seismic profiling of the recently active oroville california normal fault and microearthquake event recording with a near fault three component borehole seismometer on the san andreas fault at parkfield california have shown numerous instances of pronounced dispersive wave trains following the shear wave arrivals these wave trains are interpreted as fault zone trapped seismic modes parkfield earthquakes exciting trapped modes have been located as deep as 10 kilometers as shallow as 4 kilometers and extend 12 kilometers along the fault on either side of the recording station selected oroville and parkfield wave forms are modeled as the fundamental and first higher trapped sh modes of a narrow low velocity layer at the fault modeling results suggest that the oroville fault zone is 18 meters wide at depth and has a shear wave velocity of 1 kilometer per second whereas at parkfield the fault gouge is 100 to 150 meters wide and has a shear wave velocity of 1 1 to 1 8 kilometers per second these low velocity layers are probably the rupture planes on which earthquakes occur

structural assessment of mount etna volcano from permanent scatterers analysis a study of the deformation pattern of mount etna volcano based on the results from the permanent scatterers ps technique is reported ground motion data provided by the interferometric synthetic aperture radar insar ps technique from 1995 to 2000 are compared and validated by gps data an analysis of the ascending and descending line of sight los components of ground velocities has yielded detailed ground deformation maps and cross sections this analysis allows detection and constraint of discontinuities in the surface velocity field los velocities have then been combined to calculate the vertical and horizontal e w ground velocities a wide inflation of the edifice has been detected on the western and northern flanks over an area of about 350 km2 a seaward motion of the eastern and southern flanks has also been measured ps data allows the geometry and kinematics of the several blocks composing the unstable flanks to be defined even in the highly urbanized areas and their displacement rates have been measured with millimeter precision this analysis reveals the extension of some features beyond their field evidences and defines new important features the results of this work depict a new comprehensive kinematic model of the volcano highlighting the gravitational reorganization of the unbuttressed volcanic pile on its slippery clay basement on the southern flank but an additional drag force due to a strong subsidence of the continental margin facing the etna volcano is necessary to explain the ps velocity field observed on the eastern flank

location and orientation of eruptive fissures and feederdykes at mount etna influence of gravitational and regional tectonic stress regimes abstract lava extrusion from fissures on the flanks of the etna volcano is a common feature of recent activity as evidenced by the eruptions of 1971 1981 1983 and 1985 and was of similar importance during prehistoric times we propose here a model within which the location and orientations of the large majority of historic eruptive fissures on etna s flanks together with their feeder dykes are explained within the framework of a gravitational stress regime stress orientations within this regime are controlled largely by the gross morphology of the volcano but are significantly modified by local topographic anomalies we propose that the gravitational stress regime largely supercedes an earlier developed regional tectonic stress regime which still operates in the sub volcanic basement and may remain the dominant control of eruptive fissure and feeder dyke disposition at lower altitudes on the flanks the proposed model is supported by 1 detailed examination of fissure locations and orientations and the relationship between fissure azimuths and topography 2 precise horizontal distance measurement and vertical ground deformation studies of a recent eruption and 3 qualitative physical modelling experiments in which coloured water is injected into solidified gelatine solutions representing variously shaped volcanic constructs a cautious approach is advocated when extrapolating trends of spatially limited fissure segments for the purpose of locating potential sites of magma ascent and implications of the model for hazard analysis are outlined

deformation and eruptions at mt etna italy a lesson from 15 years of observations this work was partly funded by ingv and the italian dpc and was supported by asi the preview project and crdc amra dpc ingv flank project providing the funds for the publication fees

barium and the late paleocene δ13c maximum evidence of increased marine surface productivity deep sea sediment ba ba al2o3 sample 15 ba aluminosilicate records show increasing values synchronous with the evolution of the late paleocene global 13c maximum reflecting an increase in marine surface primary production and biogenic barite formation at this time at two oligotrophic locations deep sea drilling project dsdp sites 384 and 527 in the north and south atlantic respectively ba increases from 160 360 ppm in the early paleocene to 1100 3000 ppm during the 13c maximum at equatorial dsdp site 577 positioned within or near the high productivity zone ba increases from 15 500 ppm in the early paleocene to 25 400 ppm in conjunction with late paleocene maximum 13c values linear fitted correlation plots of sediment ba content versus surface water 13c in all three regions support barite originating in the euphotic zone the early to late paleocene relative increase in ba illustrates how burial rates of corg relative to al2o3 accelerated by a factor of 1 8 and 6 0 in the eutrophic and oligotrophic areas respectively a tentative estimate weighing our result for the entire ocean suggests that accumulation rates of organic carbon increased by a factor of 2 during the late paleocene 13c maximum

active spreading and regional extension at mount etna imaged by sar interferometry abstract large flank instability has been proposed by most recent authors as a major process in the dynamics of mount etna however several aspects of the models are still disputed such as the boundaries of the moving area and the driving force for the instability in this paper we present synthetic aperture radar interferometric data which allow us to identify two main sectors of active instability where the deformational process differs an eastern sector is bounded to the north by the pernicana provenzana fault to the west by the north rift zone and the south rift zone and to the south by the mascalucia tremestieri trecastagni fault system interferograms provide new data on the activity and extent of the southern boundary which was previously underestimated in this sector the structural features indicate an eastward sliding driven by e w regional extension which can be interpreted as a result of the retreating slab of the ionian subduction a second collapsing sector exists along the southern flank of mount etna where the interferograms show the presence of an active anticlinal ridge this ridge is interpreted as the result of southward gravity spreading over a basal decollement between etna and its plio quaternary basement and the hyblean platform the two sectors first became active in summer 1996 after the beginning of a new cycle of eruptive activity at the summit the activity was ongoing until january 1998 with the deformation rate ranging from 4 6 mm yr for the mascalucia tremestieri trecastagni faults to 12 mm yr for the anticlinal ridge

instrumental evidence of normal mode rock slope vibration summary a unique field experiment was performed to constrain the seismic response of a large potentially unstable rock slope in the southern swiss alps small aperture seismic arrays were deployed to record ambient vibrations both inside and outside of the mapped instability boundary the recordings were analysed by means of the high resolution f k method site to reference spectral ratios and time frequency dependent polarization analysis all three methods indicated that the wavefield within the potentially unstable rock mass is dominated by normal mode motion standing waves rather than horizontal propagation of seismic waves both fundamental frequency and relative amplification could be recovered from ambient noise data the observed amplification is strongly directional and the maximum amplification is oriented perpendicular to open tension cracks mapped at the ground surface our results highlight site response characteristics relevant for analysis of earthquake triggered rock slope failures

the role of the pernicana fault system in the spreading of mt etna italy during the 2002 2003 eruption flank instability and collapse are observed at many volcanoes among these mt etna is characterized by the spreading of its eastern and southern flanks the eastern spreading area is bordered to the north by the e w trending pernicana fault system pfs during the 2002 2003 etna eruption ground fracturing along the pfs migrated eastward from the ne rift to as far as the 18 km distant coastline the deformation consisted of dextral en echelon segments with sinistral and normal kinematics both of these components of displacement were one order of magnitude larger 1 m in the western previously known portion of the pfs with respect to the newly surveyed 9 km long eastern section 0 1 m this eastern section is located along a pre existing but previously unknown fault where displaced man made structures give overall slip rates 1 1 9 cm year only slightly lower than those calculated for the western portion 1 4 2 3 cm year after an initial rapid motion during the first days of the 2002 2003 eruption movement of the western portion of the pfs decreased dramatically while parts of the eastern portion continued to move these data suggest a model of spreading of the eastern flank of etna along the pfs characterized by eruptions along the ne rift instantaneous short lived meter scale displacements along the western pfs and more long lived centimeter scale displacements along the eastern pfs the surface deformation then migrated southwards reactivating one after the other the nnw sse trending timpe and trecastagni faults with displacements of 0 1 and 0 04 m respectively these structures along with the pfs mark the boundaries of two adjacent blocks moving at different times and rates the new extent of the pfs and previous activity over its full length indicate that the sliding eastern flank extends well below the ionian sea the clustering of seismic activity above 4 km b s l during the eruption suggests a deep decollement for the moving mass the collected data thus suggests a significant movement volume 1 100 km3 of the eastern flank of etna both on shore and off shore

actively growing anticlines beneath catania from the distal motion of mount etna s decollement measured by sar interferometry and gps we used sar interferometry and gps to measure the rise of an anticline beneath the urban area of catania italy which originates from outward thrusting above the basal decollement of etna volcano the anticline grows at a rate of over 0 015 m a 1 of se thrusting and about 0 007 m a 1 of relative uplift by relating this growth to the simultaneous extension measured at the summit of the volcano we demonstrate the occurrence of active volcanic spreading this process may exert a control on eruptions earthquakes sector collapses and landslides

directional topographic site response at tarzana observed in aftershocks of the 1994 northridge california earthquake implications for mainshock motions abstract the northridge earthquake caused 1 78 g acceleration in the east west direction at a site in tarzana california located about 6 km south of the mainshock epicenter the accelerograph was located atop a hill about 15 m high 500 m long and 130 m wide striking about n78 e during the aftershock sequence a temporary array of 21 three component geophones was deployed in six radial lines centered on the accelerograph with an average sensor spacing of 35 m station c00 was located about 2 m from the accelerograph we inverted aftershock spectra to obtain average relative site response at each station as a function of direction of ground motion we identified a 3 2 hz resonance that is a transverse oscillation of the hill a directional topographic effect the top base amplification ratio at 3 2 hz is about 4 5 for horizontal ground motions oriented approximately perpendicular to the long axis of the hill and about 2 for motions parallel to the hill this resonance is seen most strongly within 50 m of c00 other resonant frequencies were also observed a strong lateral variation in attenuation probably associated with a fault caused substantially lower motion at frequencies above 6 hz at the east end of the hill there may be some additional scattered waves associated with the fault zone and seen at both the base and top of the hill causing particle motions not spectral ratios at the top of the hill to be rotated about 20 away from the direction transverse to the hill the resonant frequency but not the amplitude of our observed topographic resonance agrees well with theory even for such a low hill comparisons of our observations with theoretical results indicate that the 3d shape of the hill and its internal structure are important factors affecting its response the strong transverse resonance of the hill does not account for the large east west mainshock motions assuming linear soil response mainshock east west motions at the tarzana accelerograph were amplified by a factor of about 2 or less compared with sites at the base of the hill probable variations in surficial shear wave velocity do not account for the observed differences among mainshock acceleration observed at tarzana and at two different sites within 2 km of tarzana

evidence for ground motion polarization on fault zones of mount etna volcano 1 during local and regional earthquakes an evident amplification of horizontal ground motion is observed at two seismological stations near the tremestieri fault on the southeastern flank of mount etna volcano rotated component spectral ratios show a narrow spectral peak around 4 hz along a n40 e direction a conventional polarization analysis using the eigenvectors of the covariance matrix confirms the very stable directional effect enhancing the approximately ne sw elongation of the horizontal ground motion in the fault zone the effect is evident during the entire seismogram and independent of source back azimuth as well as distance and depth of earthquakes the same polarization is observed in ambient noise as well this consistency allowed us to use microtremors for checking ground motion polarization along and across the tremestieri fault zone with a high spatial resolution the result is a stable polarization of horizontal motion in the entire area that can be observed in a broad frequency band to check whether this ground motion property is recurrent and to understand a possible relationship with fault strike faulting style or orientation of fractures ambient noise was recorded on other mapped faults of the mount etna area the moscarello acicatena and pernicana faults the latter in particular is characterized by different strike and faulting style a systematic tendency of ambient noise to be polarized is found in all of the faults a picture emerges where normal faults of the eastern flank show an e w to ne sw polarization that changes on the pernicana fault which develops approximately e w and is characterized by a prevailing nw se to n s polarization directions of polarization were never parallel to the fault strike moreover polarization persists too far away from the fault trace excluding an effect limited to a narrow low velocity zone hosted between harder wall rocks both these observations rule out an interpretation in terms of fault trapped waves the cause of observed polarizations will be the subject of future studies however the consistency with recent results of velocity anisotropy in a part of the investigated area suggests a possible role of attenuation anisotropy on horizontal amplitude variations versus azimuth