seismic and aseismic slip indicators in serpentinite gouge structures observed within experimentally deformed serpentinite gouges provide information that may be used to identify the seismic behavior of natural fault zones in laboratory friction experiments serpentinite exhibits two modes of behavior one can only result in stable fault creep and the other may result in stable slip but has the potential for earthquakes the microstructures that form during these experiments reflect the deformation style of the serpentinite distributed deformation results from aseismic fault creep and localized deformation results from conditions favorable for seismic slip distributed deformation produces a crystallographic preferred orientation of the serpentine grains s foliation localized deformation forms riedel shears similar structures occur within a natural serpentinite shear zone from monterey county california and suggest a history of stable fault creep with intermittent seismic events

from a deformed peri tethyan carbonate platform to a fold and thrust belt an example from the central apennines italy abstract in the central apennines of italy the relationships between the foreland deformation of a peri tethyan carbonate platform lazio abruzzi domain and the subsequent contractional pattern have been clearly documented by means of stratigraphic and structural evidence stratigraphic and structural data point out the occurrence of pre thrusting normal fault systems and allow us to define their relationships with contractional structures miocene normal faults are particularly well documented by thickness and facies variation of foredeep deposits and by structural evidence these faults controlled sedimentation during tortonian early messinian times foredeep stage and produced most of the accommodation space for clastic deposits in their hanging walls on the contrary the subsequent positive inversion appears to be quite limited and generally the hanging wall sequences are not uplifted above the regional clear evidence that normal faults formed first and were later cut and or rotated during thrusting is supported by analyses carried out along the main fault surfaces the restoration of a balanced geological section across the study area based on the inference of an extended foreland affected by later contraction provided a total small shortening value this is lower than the previous estimated by several authors for the same foreland fold and thrust belt

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

quaternary stratigraphy of the buried valleys of the lower red deer river alberta canada the quaternary fills of the buried valleys of southern alberta and saskatchewan have provided a wealth of information for the reconstruction of the glacial interglacial record of the western plains of canada and this paper reports on the previously unstudied stratigraphy of the buried calgary valley and its former tributaries in the lower red deer river area we attempt to differentiate empress group sediments which potentially relate to pre glacial interglacial interstadial and post glacial lake and river deposition using sedimentology stratigraphy and palaeoecology twenty nine stratigraphical logs indicate that empress group sediments have infilled a considerably large area of badlands and tributary coulees that once drained into the calgary valley located 15 km to the north of dinosaur provincial park radiocarbon dates of 52 4 ka 27 4 ka and 42 4 ka and glacially modified quartz grains suggest that at least some of the valley fills date to interglacial or interstadial periods and may be mid wisconsinan in age however outcrops of an older till overlying other valley fills suggest that the buried valleys were only partially excavated during interglacials interstadials and that older even pre glacial sediments could have survived subglacial channels recognisable on air photographs largely coincide with buried valley positions due to the preferential excavation of the quaternary sediment by meltwater and are filled with post glacial lake sediment from which a radiocarbon date of 16 ka bp was obtained pre glacial and glacial post glacial empress group sediments are lithologically indistinct but cover a large time span in southern alberta

shallow subduction beneath italy three dimensional images of the adriatic european tyrrhenian lithosphere system based on high quality p wave arrival times 1 this paper presents a velocity model of the italian central mediterranean lithosphere in unprecedented detail the model is derived by inverting a set of 166 000 pg and pn seismic wave arrival times restricted to the highest quality data available the tomographic images reveal the geometry of the subduction collision system between the european adriatic and tyrrhenian plates over a larger volume and with finer resolution than previous studies we find two arcs of low vp anomalies running along the alps and the apennines describing the collision zones of underthrusting continental lithospheres our results suggest that in the apennines a significant portion of the crust has been subducted below the mountain belt from the velocity model we can also infer thermal softening of the crustal wedge above the subducting adriatic plate in the tyrrhenian back arc region strong and extensive low vp anomalies depict upwelling asthenospheric material the tomographic images also allow us to trace the boundary between the adriatic and the tyrrhenian plates at moho depth revealing some tears in the adriatic ionian subducting lithosphere the complex lithospheric structure described by this study is the result of a long evolution the heterogeneities of continental margins lithospheric underthrusting and plate indentation have led to subduction variations slab tears and asthenospheric upwelling at the present day the high resolution model provided here greatly improves our understanding of the central mediterranean s structural puzzle the results of this study can also shed light on the evolution of other regions experiencing both oceanic and continental subduction

fault scarps and deformation rates in lazio abruzzo central italy comparison between geological fault slip rate and gps data abstract we compare new and literature data concerning the integrated deformation rate since 18 ka for the central apennines with deformation rate data derived from a 6 year gps campaign we constructed topographic profiles across the majority of the active faults in the area we derived deformation rate data from displaced post glacial sediments and slopes associated with the last major glacial retreat that occurred in the region about 18 kyr ago paleoseismic investigations in this region clearly show that offset of these features is the cumulative effect of repeated surface faulting earthquakes with magnitudes in the range 5 5 ms 7 0 a cumulative throw rate diagram incorporating both our values and the values extracted from the literature i e previously published trenching studies scarp profiles and offset terraces is presented providing a regional picture of the spatial deformation rate distribution in the central apennines during the latest pleistocene and holocene by converting cumulative throw rates into heave rates we calculate maximum extension rates of ca 2 mm year at the location of the same transect where 6 2 mm year has been measured with gps over 6 years this discrepancy between geodetic and geological fault slip rate data implies that we have to be cautious whenever we use gps data for seismic hazard assessment purposes or when attempting to reconstruct the tectonic processes in an area because geodetic data may be unrepresentative of the longer term deformation rates on the other hand this discrepancy may provide insights into the mechanics of the seismic cycle we discuss various scenarios that may explain the mis match between long term and short term measurements

finite fault inversion of dinsar coseismic displacement of the 2009 l aquila earthquake central italy 1 we define the geometric and kinematic characteristics of the fault activated during the mw 6 3 6 april 2009 l aquila earthquake from the modeling of envisat and cosmo skymed the first ever x band interferogram inverted for a coseismic dislocation study dinsar interferograms our best fit solution for the main shock is represented by a normal fault 16 km long and 12 km wide with a small right lateral component dipping 47 sw with a maximum slip of 90 cm although the seismic dislocation probably ended at 1 km depth the updip projection of the fault plane corresponds to the northern segment of the mapped paganica s demetrio fault where alignment of surface breaks was observed in the field the absence of this fault in existing seismic source catalogues suggests that an improved approach involving detailed surface and subsurface geological and geophysical investigations is needed for a better assessment of the seismic hazard at the local scale

variance estimate in frequency domain deconvolution for teleseismic receiver function computation summary in this study the problem of estimating the receiver function variance is discussed the receiver function computation is performed through a frequency domain deconvolution oldenburg 1981 of the vertical seismogram from the radial and tangential seismograms this technique requires a knowledge of the noise contaminating the seismic signals and provides an estimate of the receiver function variance oldenburg 1981 modelled this noise as additive amnion 1992 proposed to estimate the noise level from the power spectral density in a pre signal time window in this paper this approach is used jointly with an additional inversion which yields a sequence of spikes as a model for the true receiver function the resulting residual in a time window preceding the direct p pulse is used in order to evaluate the receiver function variance and the actual noise level involved in the frequency domain deconvolution this variance estimate is compared with the one provided by oldenburg s original method the application of this method to teleseismic recordings of earthquakes 5 1 mb 6 1 with similar backazimuths and distances shows that considering the additive noise only is not sufficient to explain the uncertainty measured from the pre signal in the receiver function moreover the estimated uncertainty seems to be independent of the seismic event magnitude suggesting a signal generated noise affecting the receiver function the proposed approach provides a variance estimate for a single receiver function allowing one to assess the statistical accuracy of its amplitudes in agreement with the uncertainty involved in a stacking procedure this is particularly useful when poor quality waveforms from relatively small earthquakes mb 5 1 are analysed and data from nearly co located events are not available for stacking

the arcuate shape of the umbria marche sabina apennines central italy abstract the umbria marche belt constitutes the most southern and external portion of the northern apennine arc typically convex to the northeast within this the central part the umbria marche sabina apennines is the most elevated and is characterized by a locally more pronounced curvature the umbria marche belt is a thrust belt built mainly by thrust faults affecting a multilayer sedimentary series characterized by levels with markedly different competence the main thrust the m sibillini thrust produced the tectonic superposition of the umbria marche sabina apennines over the most external units represented by the lazio abruzzi platform to the south and the marche abruzzi domain to the north farther north it joins the thrusts buried under the po plain the most important of the more internal thrusts is that of the valnerina the pronounced local curvature of the umbria marche sabina apennines may be due to accentuation of an original arcuate shape this accentuation is probably caused by differential displacement along the two main thrusts during the initial stage of the evolution of the belt late messinian early pliocene at that time this displacement was more important in the northern part where the thrust fronts show a nw se trend than in the southern portion where they are n s trending on account of the lazio abruzzi carbonate platform which perhaps represented a local obstacle to thrusting as for the initial curvature we think that this is determined by older discontinuities which controlled thrust development the final arcuate shape was not substantially changed during the subsequent compressional history of the belt early pliocene middle pliocene

a new view of italian seismicity using 20 years of instrumental recordings in this paper we show the seismicity of the past 20 years that occurred in italy and surrounding regions hypocentral locations have been obtained by using p and s wave arrival times from the ingv national and several regional permanent seismic networks more than 48 000 events selected from an original data set of about 99 780 are used to reconstruct the most complete seismic picture of the italian region so far the seismicity distribution allows inference on seismotectonics of this complex region of subduction versus continental collision our results clearly reveal the geometry of the adria and the ionian subduction and a continuous normal fault belt in the upper crust following the apennines mountain range the depth of the seismogenic layer is computed from the cut off of seismicity at depth and shows large variations along and across the seismic active regions earthquakes are generated by the different velocity of slab retreat and the subsequent asthenospheric upwelling d 2004 elsevier b v all rights reserved

earthquake locations and three dimensional crustal structure in the coyote lake area central california previous work on the simultaneous inversion method has been improved and extended to incorporate iterative solution for earthquake locations and laterally heterogeneous structure approximate ray tracing and parameter separation are important elements of the improved method application of the method to p wave arrival time data recorded by stations of the u s geological survey central california network yields a three dimensional model for the velocity structure of the upper crust in an area encompassing the rupture zone of the coyote lake earthquake of august 1979 very strong correlations between the velocity model and the geology and gravity and magnetic anomalies are observed improved estimates of the locations of earthquakes in the study area are also determined the relocation of explosions indicates epicentral accuracies of the order of a kilometer or better based on the revised hypocentral locations it is concluded that the san andreas fault is vertical in this area with no actual offset between the epicenters and the fault trace in contrast the calaveras has two or more active fault surfaces one nearly vertical and another dipping 75 to the northeast

crustal fabric in the tibetan plateau based on waveform inversions for seismic anisotropy parameters 1 the tibetan plateau has the thickest continental crust on earth and fabrics within the crust that are anisotropic to seismic waves may provide clues to how it reached such extreme proportions and how it is currently deforming waveform modeling using a global minimization inversion technique applied to receiver functions computed from 11 stations spanning the north south length of the eastern plateau has yielded a suite of crustal models that include anisotropy these models suggest that the tibetan crust contains 4 14 anisotropy at different depths that is likely a result of both fossil fabrics and more recent deformation all models contain anisotropy in the surface layer and for most stations the alignment of the slow symmetry axis suggests a relationship with crustal fabrics associated with e w trending thrust faults or sutures middle to lower crustal anisotropy is present at most stations with a fast axis trending n s to nw se in the south nearly e w in the central plateau and n s to ne sw in the northern plateau this pattern appears consistent with recent ductile deformation due to both topographically induced flow and to boundary forces from subducting lithosphere at the northern and southern margins of the plateau the orientations of crustal anisotropy determined for most stations in this study are significantly different from shear wave splitting fast polarization directions implying distinct deformation in the crust and mantle

subduction zone anisotropy beneath corvallis oregon a serpentinite skid mark of trench parallel terrane migration 1 we studied the back azimuth dependence of ps converted phases at gsn station cor corvallis oregon using broadband p receiver functions computed from 602 teleseismic earthquakes the amplitudes and polarities of the transverse ps phases are largely two lobed which indicates anisotropy with a tilted symmetry axis a double peaked ps conversion at 4 5 6 5 s delay has the moveout of a dipping slab but is not consistent with simple deflection of the ps converted phase by the dipping interface a polarity flip on the transverse receiver function near north south back azimuth indicates an anisotropic symmetry axis aligned north south far from the convergence direction n68 e the ps phase is modeled using reflectivity synthetics with a highly anisotropic layer of depressed wave speed vp 6 0 6 5 km s near 40 km depth at the slab interface with the overriding north american plate one dimensional modeling suggests 10 anisotropy in the supraslab layer with a slow symmetry axis oriented n5 w at a 60 tilt from the vertical adjustments for the effect of slab interface dip on ps amplitude suggest a somewhat lower 7 anisotropy we infer a thin 7 km anisotropic detachment zone for the northward slippage of the siletz forearc terrane along the top of the descending slab a motion consistent with gps measurements and models of regional lithospheric dynamics serpentinite is a likely constituent for the deep anisotropic layer owing to its reduced vp and high poisson ratio the ductile rheology and hydrated composition of serpentinite make it a plausible lithology for a mechanical detachment zone

crustal structure of northern latium central italy from receiver functions analysis new evidences of a post collisional back arc margin evolution abstract the crustal velocity structure in a region of central apennines of italy at the hinge between the highly stretched portion of the monte argentario promontory and the magmatic province of the tolfa domes complex northern latium is discussed in this study s wave velocities at depth have been constrained by the modeling of p wave receiver functions rf from both temporary and permanent broadband seismic stations the computer 3d vs models show a thin crust 19 25 km made of a shallow and thin sedimentary cover a very high velocity and anisotropic layer related to a metamorphic basement and a low vs anisotropic layer in the middle lower crust above a shallow moho discontinuity modeled at about 20 km depth the volcano tectonic evolution of this portion of tyrrhenian back arc margin has been strongly influenced by its peculiar crustal architecture the low vs layer acted as a shear zone in the middle lower crust during the tyrrhenian extension also helping the development of plio quaternary magmatism our findings potentially give new constraints on the evolution of the area and to the general comprehension of back arc development in collisional regions

velocity and anisotropy structure at the hikurangi subduction margin new zealand from receiver functions summary we examine seismic velocity and anisotropy at the interface between the australian and the subducting pacific plate in southern north island new zealand using receiver functions from teleseismic earthquakes recorded on two l shaped seismic arrays iris station snzo makes up the corner of the southern array velocity models are tested with a ray theoretical method that allows both dipping boundaries and anisotropy assuming a 2 d structure beneath each array the strongest arrival on the northern array consistently appears at 2 s the arrival is modelled by a jump in velocity at a flat boundary at 12 km which may be caused by a change in metamorphic grade this prominent arrival correlates with a weaker arrival at 1 5 s 7 km at station snzo isotropic layers dipping with the slab can explain many features in the first 20 s of the records but anisotropy is needed to explain both the transverse receiver functions and a change in the polarity of a prominent ps arrival at 3 s delay relative to p o nthe radial component this arrival is consistent with a change between an upper layer that is either isotropic or anisotropic with a horizontal symmetry axis and a supraslab metasediment layer having anisotropy with av ertical slow axis of symmetry there is tradeoff between boundary dip the plunge of the axis of symmetry layer thickness and the amount of anisotropy a dip of 20 shallowing to 15 under the tararua array thickness of 4 km and a vertical symmetry axis fits the backazimuth variation of the amplitudes and polarities of the arrivals with anisotropy of 4 6 per cent observed layer multiples are smaller than synthetic predictions to explain this discrepancy either layer boundaries are rough attenuation is strong or the layer boundaries are more gradational at the periods 1 s used in this study compared to previous studies 5 s

inferences on the upper crustal structure of southern apennines italy from seismic refraction investigations and subsurface data abstract this paper presents an interpretation of crustal seismic refraction data from the northern sector of the southern apennines thrust belt a region that in historical times experienced large destructive earthquakes the data were acquired in 1992 along a seismic line 75 km long and parallel to the apenninic chain in order to determine a detailed 2 d p wave velocity model of the upper crust in an area that had not been deeply investigated by geophysical methods previously we have used a 2 d ray tracing technique based on asymptotic ray theory to model travel times of first and reflected p wave arrivals synthetic seismograms have been produced by finite difference simulations in order to check the reliability of the velocity model inferred by ray tracing modelling the interpretation of the velocity model is constrained by stratigraphic and sonic velocity logs from wells for oil exploration located close to the seismic line gravity data modelling allows to check the velocity model and to extend the structural interpretation in 3 d in the shallow crust up to a depth of 3 4 km strong lateral variations of the modelled velocities are produced by the overlapping of thrust sheets formed by 1 cenozoic flyschoid cover and basinal successions that underlie the seismic profile with p wave velocities in the 2 8 4 1 km s range and thicknesses varying between 0 5 and 4 5 km 2 mesozoic basinal sequences with a velocity of 4 8 km s and a depth of 1 5 2 1 km in the northern part of the profile 3 mesozoic limestones of the western carbonate platform with a velocity of 6 0 km s and a depth of 0 1 0 8 km in the southern part of the profile at a greater depth the model becomes more homogeneous a continuous seismic interface 3 0 4 5 km deep with a velocity of 6 0 km s is interpreted as the top of the meso cenozoic carbonate multilayer of the apulia platform characterized by an increase in seismic velocity from 6 2 to 6 6 km s at depths of 6 7 km a lower p wave velocity about 5 0 km s is hypothesized at depths ranging between 9 5 and 11 km as inferred by commercial seismic lines and data from two deep wells located in the apulia foreland and bradano foredeep this low velocity layer can be related to permo triassic clastic deposits drilled at the bottom of the apulia platform seismic data do not allow us to identify possible deeper seismic interfaces that could correspond to the top of the paleozoic crystalline basement this is probably due to the low velocity layer at the bottom of the carbonate multilayer that reflects and attenuates a great part of the seismic energy the joint interpretation of seismic refraction and well data in accordance with gravity data provides the first detailed p wave velocity model of the upper crust of the northern sector of the southern apennines which differs considerably from previous 1 d velocity models used to study the seismicity of the region and reveals new information about the structure of the thrust belt

thrust tectonics thin skinned or thick skinned and the continuation of thrusts to deep in the crust abstract the paper analyses the geometry of thin skinned thrust zones where the thrusts shallow out at depth and of thicker skinned fault zones where much of the crust is involved and where the thrusts are frequently observed to become steeper downwards in the interiors of many orogenic belts the steep dip of faults is not original but due to the folding above lower decoupling zones the energy involved in the internal deformation of hanging wall rocks may prohibit many faults becoming more shallow upwards such shallowing upwards faults may occur in more ductile rocks to maintain compatibility between zones which have experienced different deformation intensities but displacements on the faults are unlikely to be large another mechanism for producing faults which steepen downwards is proposed for the major thrusts which form the southern margin to the himalayas these carry large thicknesses 30 to 100 km of crustal and upper mantle rocks to the south causing flexuring and isostatic depression of the indian plate the steeply dipping thrusts are not footwall ramps these may be some distance behind the steepened zone this thrust induced isostatic bending of the crust has important implications when considering regional seismic interpretations as well as thrust mechanics and kinematics

the 1995 kobe earthquake seismic image of the source zone and its implications for the rupture nucleation in order to understand what may have triggered the 1995 kobe japan earthquake and how the rupture proceeded after initiation we determined high resolution three dimensional 3 d p and s wave velocity and poisson s ratio structures in the kobe epicentral area and relocated the aftershocks with the obtained 3 d velocity model we used 64 337 p and 49 200 s wave high quality arrival times from 3634 kobe aftershocks and local microearthquakes recorded by both permanent seismic networks and portable stations that were set up following the kobe mainshock significant velocity variations of up to 6 are revealed in the aftershock area we found that areas with high aftershock activity are generally associated with low poisson s ratio which may be the strong and competent parts of the fault zone and were apt to generate aftershocks the kobe mainshock hypocenter is located in a distinctive zone characterized by low p and s wave velocities and a high poisson s ratio this anomaly exists in the depth range of 16 to 21 km and extends 15 to 20 km laterally this anomaly may be due to a fluid filled fractured rock matrix that contributed to the initiation of the kobe earthquake our interpretation has been supported by many pieces of evidence from hydrological geochemical seismological and geophysical investigations conducted at the kobe earthquake region

fault zone architecture and deformation processes within evaporitic rocks in the upper crust 1 recently in the northern apennines geophysical data have identified the triassic evaporites te anhydrites and dolomites as the source region of the major extensional earthquakes of the area m 6 in order to characterize fault zone architecture and deformation processes within the te we have studied exhumed evaporite bearing normal faults within the upper crust the structure of large displacement 100 m normal faults is given by 1 a zoned fault core with a wider portion of fault parallel foliated ca sulphates ductile deformation overprinted by an inner fault core ifc of localized brittle deformation and 2 wide dolostones to absent ca sulphates damage zones of fault fracture patterns fault rock assemblage within the ifc is characterized by fault breccia gouge and cataclasites of different grain size most of the deformation within the ifc is localized along thin and fault parallel principal slip surfaces pss made of dolomite rich fine grained cataclasite sem analyses show an evolution from ca to st to gypsum rich mineralization due to episodic fluid flow events channeled along the fault zones during different stages of fault exhumation the development of the observed fault geometry can be explained by a mechanical fault evolution model where initial faulting occurs along broad and ductile shear zones within the anhydrites and causes fracturing within the dolostones progressive deformation within the fault core leads to the development of fault parallel dolomite rich cataclastic layers their reactivation coupled with transient fluid overpressures can produce embrittlement and localization of brittle deformation within the ifc

stuck at the bar larger than average grain lag deposits and the spectrum of particle mobility larger than average grain deposits in gravel bed rivers potentially exert a distinctive influence upon fluvial morphodynamics and flow resistance they are products of historical contingency sourced from rare events that supply atypically coarse material larger than average grain lag deposits are emblematic attributes of the tongariro river new zealand they are deposited on bar edges and heads derived from lahar valley floor deposits that subsequently became terraces these materials are less likely to be reworked across a range of flows compared to other bar material conceptual models that consider channel configuration and incorporate distributions of particle mobility and flood flows are necessary to assess the role of larger than average grain deposits on river morphodynamics

a critical assessment of subglacial mega floods a case study of glacial sediments and landforms in south central alberta canada the existing subglacial megaflood explanation of glacial sediment deposition and landform production in south central alberta relies upon four sets of observations and associated interpretations 1 a subglacial genesis for all glacilacustrine sediments lying stratigraphically below a local melt out till or ice stagnation facies 2 a melt out genesis for the ice stagnation facies 3 a syn depositional status for the glacitectonic disturbance visible in most exposures due to periodic ice bed re coupling and 4 a subglacial megaflood origin for a truncation surface and clast lag that occurs at the top of the sedimentary exposures and the carving of hummocky terrain and flutes in the area we provide alternative interpretations of the sediment landform assemblages of the area and demonstrate that alternative simpler interpretations of the evidence can be proposed specifically we propose 1 a proglacial rather than subglacial origin of glacilacustrine sediments 2 a glacilacustrine origin for the melt out till and its subsequent glacitectonic disturbance by minor glacier readvances 3 postdepositional rather than syn depositional glacitectonic disturbance due to a significant advance by glacier ice after the accumulation of a thick sequence of glacilacustrine sediments 4 that some linear chains of hummocks are the morphological expression of glacitectonic folding and thrusting 5 that the use of the truncation surfaces to propose a subglacial fluvial origin for hummocky moraine is flawed logic because they do not constitute the tops of hummocks but rather occur on the interfluves that separate the numerous small coulees incised into the valley sides during postglacial time truncation surfaces and clast lags occur locally on the beds of spillway tracts and can be explained as the products of erosion by subaerial spillway water the mega flood explanation of flutings and hummocky moraine in the region is also questioned because these landforms record a regional ice flow imprint of mis aligned and cross cutting flow sets terminating at series of inset and locally cross cutting and lobate transverse ridges moraines these landform associations preclude a subglacial flood origin for the flutings and demonstrate that the transverse ridges are more appropriately interpreted as recessional push moraines the similarity of the glacial landforms of this region to the active temperate glacial landsystem produced by historical glacier recession in modern glacierized catchments where sheetfloods have not been influential in subglacial landform production allows us to apply a modern analogue to landscape interpretation that does not include subglacial sheetflooding

crustal structure in the area of the 2002 molise earthquake clues for the evolution of the southern apennines the apennines is a mountain belt with paired extension and compression that are explained by the subduction and delamination of the ionian adria lithosphere during the belt formation the adria crust is flexed downward and then incorporated into the wedge after peeling off along some weak level whose origin is still discussed in southern apennines this process seems to have stopped at about 0 7 ma by the development of a tear in the subducting lithosphere and consequent extension that spread along the mountain range seismological data acquired after the 2002 mw 6 0 molise strike slip earthquake yield modeling the structure of the adria crust as congealed close to the leading edge of the belt tomography images show inverted normal faults within the sedimentary cover apulian units fault inversion incomplete close to the compressional front testifies for a final squeezing of the entire previously flexed apulian continental margin pronounced high vp and low vp vs anomalies are observed at depth greater than 12 km and undoubtfully attributed to heterogeneities of the basement solving the long lasting contention on the nature of similar high speed bodies observed beneath the apennines beneath these bodies we observe a strong reflectivity suggesting the presence of a fluid filled layer in the middle lower crust that may act as a decoupling level in the apennines tectonics the deep fluids are also favoring the rupture of strike slip earthquakes like those that occurred in 2002 and the intermediate depth seismicity diffused in the apulian region

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

the 2009 l aquila earthquake italy what s next in the region hints from stress diffusion analysis and normal fault activity abstract this work aims at defining the contribution in terms of earthquake probability assessment of the integration of coulomb stress diffusion analysis related to an earthquake with geological studies on fault activities investigating the case of the april 6 2009 l aquila central italy earthquake mw 6 3 the analysis of the coulomb stress diffusion induced by this earthquake has revealed a stress increase along two poorly investigated active normal faults in the apennines the subequana fault and the middle aterno valley fault no strong seismic events have been attributed to these tectonic structures over the past 800 1000 yr and they have therefore been considered as probable seismic gaps geological and paleoseismological investigations have since indicated that these tectonic structures belong to the same 25 30 km long fault system that ruptured twice during the late holocene the last activation occurred between the 4th 1st century b c and the past millennium probably during the 2nd 1st century b c with the penultimate between 6381 30 bp and 3511 37 bp the data obtained indicate that this fault system might rupture in up to magnitude 6 8 earthquakes and that the 2009 seismic event has brought these tectonic structures about 200 yr closer to failure

an upper bound on the rate of strain in the central apennines italy from triangulation measurements between 1869 and 1963 italy is covered by a first order triangulation network that was established between 1869 and 1908 and re measured in patches between 1936 and 1963 we analyse the measurements made in the central part of italy to form an estimate of the rate of strain in the central apennines we conclude that the rate of strain in this region is too small to detect from the repeated triangulation measurements this result places an upper bound of about 10 7 yr on the strain rate of the central apennines and implies that the maximum rate of extension across the region is no higher than about 3 mm yr

refined rupture velocity estimation of the 2009 l aquila earthquake mw 6 3 central italy derived from apparent source time functions in this paper we obtain an accurate estimation of the rupture velocity of the 6 april 2009 mw 6 3 l aquila earthquake central apennines by analyzing its apparent source time functions astfs these astfs have been extracted by deconvolv ing an empirical green s function egf at seismic stations located 200 800 km from the earthquake from the study of duration shape and directivity of astfs at numerous and well distributed stations we show that the area between the two main slip patches of the earthquake ruptured at a relatively slow velocity 1 6 km s we next validate simulta neously the astfs and the slip model independently obtained through the joint inversion of strong motion broadband teleseismic global positioning system and interferometric synthetic aperture radar data the good agreement in shape and duration between the observed and theoretical astfs is an indication for the reliability of the inferred source model and for the robustness of the rupture velocity estimations of this study

the holocene paleoearthquakes on the 1915 avezzano earthquake faults central italy implications for active tectonics in the central apennines abstract extensive paleoseismological research was conducted in the fucino plain central italy in order to better understand the seismogenic characteristics of the fault responsible for the 1915 avezzano earthquake ms 7 0 and improve the general knowledge regarding active tectonics in the central apennines evidence for late pleistocene holocene surface faulting events was obtained through the study of thirteen sites across four different fault branches the paleoseismological analysis outlined the occurrence of ten surface faulting events in the past 33 000 years seven of which occurred during the holocene radiocarbon thermoluminescence and archaeological dating permitted the definition of an event chronology and the estimation of a recurrence interval for surface faulting events ranging between 1400 and 2600 years on the basis of the observed offsets it was possible to calculate vertical slip rates for the individual fault branches ranging between 0 24 mm yr 1 and 0 5 mm yr 1 and an extension rate across the fucino plain ranging between 0 6 and 1 mm yr 1 the chronology of surface faulting events appears linearly distributed in time and the observed recurrence times are similar to those inferred by other paleoseismological studies along different active apennine faults the general consequence of the large time span between strong earthquakes is that even a 2000 year long historical record such as the italian earthquake catalogue does not cover the entire seismic cycle of all the active apennine faults a comparison of the extension rate across the fucino plain with that across the entire central apennines as inferred from the sum of seismic moments of earthquakes which occurred in the interval 1000 1992 shows a seismicity deficit in the period indicated this confirms that a number of seismogenic faults were not active during the past 1000 years

sedimentary and tectonic evolution of plio pleistocene alluvial and lacustrine deposits of fucino basin central italy abstract the fucino basin was the greatest lake of the central italy which was completely drained at the end of 19th century the basin is an intramontane half graben filled by plio quaternary alluvial and lacustrine deposits located in the central part of the apennines chain which was formed in upper pliocene and in quaternary time by the extensional tectonic activity the analysis of the geological surface data allows the definition of several stratigraphic units grouped in lower units and upper units the lower units upper pliocene are exposed along the northern and north eastern basin margins they consist of open to marginal lacustrine deposits breccia deposits and fluvial deposits the upper units lower pliocene holocene consist of interbedded marginal lacustrine deposits and fluvial deposits thick coarse grained fan delta deposits are interfingered at the foot of the main relief with fluvial lacustrine deposits most of the thickness of the lacustrine sequences more than 1000 m thick is buried below the central part of the fucino plain the basin is bounded by e w wsw ene and nw se fault systems velino magnola fault e w and tremonti celano aielli fault wsw ene and s potito celano fault nw se in the north the trasacco fault the pescina celano fault and the serrone fault nw se in the south east the geometry and kinematic indicators of these faults indicate normal or oblique movements the study of industrial seismic profiles across the fucino basin gives a clear picture of the subsurface basin geometry the basin shows triangular shaped basin fill geometry with the maximum deposits thickness toward the main east boundary fault zones that dip south westward serrone fault trasacco fault pescina celano fault on the basis of geological surface data borehole stratigraphy and seismic data analysis it is possible to recognize and to correlate sedimentary and seismic facies the bottom of the basin is well recognized in the seismic lines available from the good and continuous signals of the top of meso cenozoic carbonate rocks the shape of sedimentary bodies indicates that the filling of the basin was mainly controlled by normal slip along the nw se boundary faults in fact the continental deposits are frequently in on lap contact over the carbonate substratum several disconformable contacts occurred during the sedimentary evolution of the basin the main faults with antithetic and synthetic fault planes displace the whole sedimentary sequence up to the surface indicating a recent faults activity 1915 avezzano earthquake ms 7 0 the stratigraphic and tectonic setting of the fucino basin and neighboring areas indicates that the extensional tectonic events have had an important role in driving the structural sedimentary evolution of the plio quaternary deposits the geometry of the depositional bodies of the fault planes and their relationships indicate that the fucino basin was formed as a half graben type structure during plio quaternary extensional events some internal complexities are probably related to the fold and thrust structures of the apenninic orogeny formed in messinian time in this area and to a different activity timing of the e w and wsw ene fault systems and the nw se fault systems we believe based on the similarity of the surface characteristics that the structural setting of the fucino basin can be extrapolated to the other great intramontane basins in central italy e g rieti l aquila sulmona sora isernia basins

the frictional behavior of serpentinite implications for aseismic creep on shallow crustal faults serpentine is common in many active faults and may be responsible for aseismic creep along segments of these faults to test this we have conducted a series of velocity stepping experiments to determine the frictional velocity dependence of serpentinite we slid initially bare rough surfaces of antigorite serpentinite at room temperature with velocities from 0 0032 to 10 0 m s 1 0 102 to 3 2 105 mm yr and normal stresses from 25 to 125 mpa we find that the velocity dependence of serpentinite undergoes a transition from velocity weakening at fast loading velocities to velocity strengthening at slow velocities and that this change is accompanied by other changes in the constitutive behavior these results suggest that serpentinite should not be the site of instability initiation during sliding at plate velocities but may permit propagation of unstable slip initiated elsewhere

p wave tomography of the mantle under the alpine mediterranean area 1 we study the upper mantle p wave velocity structure below the euro mediterranean area down to 1000 km depth by seismic travel time tomography we invert summary residuals constructed with both regional and teleseismic first arrival data reported by the international seismological centre isc 1964 1995 introducing some alternative strategies in the travel time tomographic approach and a new scheme to correct teleseismic data for global mantle structure our high resolution model pm0 5 is parameterized with three dimensional 3 d linear splines on a grid of nodes with 0 5 spacing in both horizontal directions and 50 km vertical spacing we obtain about 26 root mean square rms reduction of residuals by inversion in addition to roughly 31 reduction after summary rays formation and selection sensitivity analyses are performed through several test inversions to explore the resolution characteristics of the model at different spatial scales the distribution of large scale fast anomalies suggests that two different stages of a convection process presently coexist in very close regions the mantle dynamics of western central europe is dominated by blockage of subducted slabs at the 660 km discontinuity and ponding of seismically fast material in the transition zone contrarily in the eastern mediterranean fast velocity material sinks into the lower mantle suggesting that the flow of the cold downwelling here is not blocked by the 660 km discontinuity on a smaller scale the existence of tears in the subducted slab lithospheric detachment all along both margins of the adriatic plate as proposed by some authors is not supported by our tomographic images

till stratigraphy and sedimentology at the margins of terrestrially terminating ice streams case study of the western canadian prairies and high plains complex glacigenic sediment sequences arranged in large arcuate assemblages and demarcating the lobate termini of fast ice flow corridors in western canada represent the terrestrial equivalents of the trough mouth fans of the marine palaeo ice stream record intensive sedimentological and stratigraphic investigations at a regional scale are employed in the interpretation of thick units or sequences of diamicton and two depositional scenarios are proposed first glacier marginal till thickening and the stacking of till wedges takes place in areas where an ice stream margin was stationary for short periods of time stacks of subglacial traction tills potentially record annual sub marginal incremental thickening at ice stream margins especially in areas where densely spaced recessional push moraines appear to record seasonal climatic forcing second proglacial lake and valley infilling with glacilacustrine rhythmites and mass flow diamictons is associated with the advection of sub marginal till into preglacial bedrock depressions and records ice stream marginal oscillations and debris influx into discontinuous proglacial lakes which act as subaqueous sediment sinks for materials that would otherwise have been used to construct sub marginal till wedges and moraines glacial overriding modifies the deposits produced in both scenarios through deformation and the dislocation and entrainment of bedrock and sediment rafts at the margins of bedrock valley walls resulting in the widespread development of glacitectonites and megablocks the occurrence of the thickest deposits as preglacial valley fills may be significant in groundwater siphoning away from subglacial deforming layers and the promotion of sticky spots

the 2009 l aquila central italy mw6 3 earthquake main shock and aftershocks 1 a m w 6 3 earthquake struck on april 6 2009 the abruzzi region central italy producing vast damage in the l aquila town and surroundings in this paper we present the location and geometry of the fault system as obtained by the analysis of main shock and aftershocks recorded by permanent and temporary networks the distribution of aftershocks 712 selected events with m l 2 3 and 20 with m l 4 0 defines a complex 40 km long nw trending extensional structure the main shock fault segment extends for 15 18 km and dips at 45 to the sw between 10 and 2 km depth the extent of aftershocks coincides with the surface trace of the paganica fault a poorly known normal fault that after the event has been quoted to accommodate the extension of the area we observe a migration of seismicity to the north on an echelon fault that can rupture in future large earthquakes

the 1984 abruzzo earthquake italy an example of seismogenic process controlled by interaction between differently oriented synkinematic faults the evolution of the seismogenic process associated with the ms 5 8 sangro valley earthquake of may 1984 abruzzo central italy is closely controlled by the quaternary extensional tectonic pattern of the area this pattern is characterised by normal faults mainly nnw striking whose length is controlled by pre existing mio pliocene n100f10j left lateral strike slip fault zones these are partly re activated as right lateral normal oblique faults under the quaternary extensional regime and behave as transfer faults integration of re located aftershocks focal mechanisms and structural features are used to explain the divergence between the alignment of aftershocks wsw ene and the direction of seismogenic fault planes defined by the focal mechanisms nnw sse of the main shock and of the largest aftershock ms 5 3 the faults that appear to be involved in the seismogenic process are the nnw sse barrea fault and the e w m greco fault there is field evidence of finite quaternary deformation indicating that the normal barrea fault re activates the m greco fault as right lateral transfer fault no surface faulting was observed during the seismic sequence the apparently incongruent divergence between aftershocks and nodal planes may be explained by interpreting the m greco fault as a barrier to the propagation of earthquake rupturing the rupture would have nucleated on the barrea fault migrating along strike towards nnw the sharp variation in direction from the barrea to the m greco fault segments would have represented a structural complexity sufficient to halt the rupture and subsequent concentration of post seismic deformation as aftershocks around the line of intersection between the two fault planes fault complexities similar to those observed in the sangro valley are common features of the seismic zone of the apennines we suggest that the zones of interaction between nw se and nnw sse plio quaternary faults and nearly e w transfer faults extending for several kilometres in the same way as m greco does might act as barriers to the along strike propagation of rupture processes during normal faulting earthquakes this might have strong implications on seismic hazard especially for the extent of the maximum magnitude expected on active faults during single rupture episodes d 2002 elsevier science b v all rights reserved

the athabasca fluting field alberta canada implications for the formation of large scale fluting erosional lineations abstract current drumlin and fluting hypotheses centred on processes of formation erosion and deposition by subglacial deformation accretion by lodgement glacial erosion and meltwater erosion and deposition rarely receive comprehensive field testing this paper documents the morphology internal structure and landscape associations of the athabasca fluting field alberta and discusses how well these characteristics are explained by postulated fluting forming processes fluting hypotheses are comprehensively tested by this approach and their rejection or acceptance are firmly based on field observation and knowledge of processes using multiple criteria fluting is shown to be erosional and not to be a product of pervasive subglacial deformation or accretion by lodgement morphology landscape associations bed truncation plus glaciofluvial lags and gravel on fluting ridges are inferred to support erosion by meltwater intact primary bedding synsedimentary faults and injection structures very close to the landsurface showing no sign of shear deformation are used to reject erosion by subglacial deformation fluting is shown to be closely associated with tunnel channels and indicates that these channels were overtopped by broad floods that formed the fluting field and eroded anabranching tracts over the length of the alberta plains prior to fluting formation sequences with melt out and lodgement till conduit sediment and boulder lags record net deposition over an extended time period diapirism prior to fluting formation marks a period of extreme pressure gradients which are related to bed separation following fluting formation there was only minimal landscape modification dominated by glaciofluvial and glaciolacustrine deposition not glacial processes this progression is presented as evidence for two very different glacial regimes separated by a short period with diapirism and extensive landscape modification by meltwater erosion we note that the study area was glaciated only once during the late wisconsinian and it follows that glacial sedimentation and landscape modification were confirmed to this single glacial episode

the anatomy of the 2009 l aquila normal fault system central italy imaged by high resolution foreshock and aftershock locations 1 on 6 april 01 32 utc 2009 a mw 6 1 normal faulting earthquake struck the axial area of the abruzzo region in central italy we study the geometry of fault segments using high resolution foreshock and aftershock locations two main sw dipping segments the l aquila and campotosto faults forming an en echelon system 40 km long nw trending the 16 km long l aquila fault shows a planar geometry with constant dip 48 through the entire upper crust down to 10 km depth the campotosto fault activated by three events with 5 0 mw 5 2 shows a striking listric geometry composed by planar segments with different dips along depth rather than a smoothly curving single fault surface the investigation of the spatiotemporal evolution of foreshock activity within the crustal volume where the subsequent l aquila main shock nucleated allows us to image the progressive activation of the main fault plane from the beginning of 2009 the foreshocks activated the deepest portion of the fault until a week before the main shock when the largest foreshock mw 4 0 triggered a minor antithetic segment seismicity jumped back to the main plane a few hours before the main shock secondary synthetic and antithetic fault segments are present both on the hanging and footwall of the system the stress tensor obtained by inverting focal mechanisms of the largest events reveals a ne trending extension and the majority of the aftershocks are kinematically consistent deviations from the dominant extensional strain pattern are observed for those earthquakes activating minor structures

quaternary geology and geomorphology of the dinosaur provincial park area and surrounding plains alberta canada the identification of former glacial lobes drainage diversions and meltwater flood tracks abstract the quaternary geology and geomorphology of the lower red deer river drainage basin centred on the dinosaur provincial park badlands provides information on pre late wisconsinan drainage patterns and the dynamics of former lobes of the laurentide ice sheet in western canada patterns of deglaciation proglacial lake evolution and spillway incision are also reconstructed based upon the distribution of surface materials and glacial glaciofluvial landforms the empress group fluvial and glaciolacustrine sediments which could be as young as 27 ka bp infill the precursor red deer river and its tributaries and document the initial advance of glacier ice into southern alberta glaciotectonic disturbance of older sediments and bedrock the production of deformation tills and the construction of a megafluting complex and cupola hills record the advances of a glacier lobe centred over the study area stratified inter and intra till beds record pulses of subglacial meltwater between phases of subsole deformation the thickening of tills towards the margin of the lobe represents a till wedge an expected product of sediment advection by glaciers moving over deformable beds the eastern margin of the glacier lobe is demarcated by the interlobate suffield hummocky moraine belt which contains overprinted thrust ridges which record diachronous oscillations of neighbouring lobes within the ice sheet proglacial and glaciofluvial sediments were deposited in the area in association with proglacial lake bassano patricia which drained eastwards when the suffield moraine was dissected by spillways changes in the size of glacial lake bassano patricia are clearly documented by a sequence of spillway incisions which culminated in the erosion of scabland topography and the initiation of a new course for the red deer river a 15 km southward diversion of the main channel in distinct contrast to the documented incision histories of other small rivers in alberta one tree creek and little sandhill creek did not start major incisions of the quaternary sediments over buried valley positions until the late holocene when environmental conditions were characterized by higher precipitation

growth processes and melange formation in the southern apennines accretionary wedge abstract the southern apennines owe their present geometry to the subduction of an apulian continental lithospheric slab and are thus best interpreted as an accretionary wedge southward the apenninic thrust front branches on to the still active ionian wedge which is related to the present calabro sicilian subduction the interpretation of conventional seismic reflection profiles and exploration wells combined with geologic field studies biostratigraphy and structural geology provide constraints for a geodynamic model for the post messinian growth of the apenninic prism our model for the apennines is a good analogy for submerged oceanic accretionary prisms in both instances features such as out of sequence thrusts underplating and duplexes are viewed as processes to explain the thickening of accretionary wedges syntectonic terrigenous deposits have accumulated in the synclines developed above the flats of pliocene thrust faults these depocenters represent piggy back basins younger accretion at the eastern border of the accretionary wedge has led to a progressive uplifting and tilting of the already emplaced thrust sheets including a continous westward migration of the depocenters in the piggy back basins during pliocene and early quaternary times a contrary west to east migration of the depocenters locally occurred where preexisting flats of pliocene thrust faults have been refolded rather than only being rotated dewatering processes and effects of overpressures on undercompacted sediment deformations can also be studied in the southern apennines melanges and broken formations form an important component of the trench apparently restricted to the base of tectonic nappes listric normal faults are a major structural element which preserves in combination with the erosion of topographic highs and resedimentation in the piggy back basins a uniform geometric shape critical taper for the prism the age and location of these distensive or gravitational effects are also discussed

the 1992 landers earthquake sequence earthquake occurrence and structural heterogeneities the june 28 1992 mw 7 3 landers earthquake occurred in the southeastern mojave desert california over 10 000 aftershocks of the earthquake were recorded by the caltech usgs southern california seismic network scsn in 1992 to investigate the relationship between complexities in the crustal structure and variations in seismicity we have used a tomographic method to invert 145 098 p wave arrival times from 3740 landers earthquake aftershocks and 1148 other events recorded by 60 permanent and temporary scsn stations we determined a detailed p wave tomographic image with a spatial resolution of about 5 km and relocated the hypocenters with the obtained 3 d velocity model the results show a correlation between seismicity patterns and velocity patterns and a tendency for regions rich in seismicity to be associated with higher velocities the higher velocity areas are considered to be strong and brittle parts of the fault zone which are apt to generate earthquakes in contrast low velocity areas are probably more ductile and weaker allowing aseismic slippage

first results from the crop 11 deep seismic profile central apennines italy evidence of mid crustal folding the crop 11 deep seismic profile across the central apennines italy reveals a previously unknown mid crustal antiform here interpreted as a fault bend fold like structure the seismic facies and gravity signature suggest that this structure consists of low grade metamorphic rocks geomorphological stratigraphic and tectonic evidence in the overlying shallow thrusts suggests that this structure developed in early to mid messinian time and grew out of sequence in late messinian pliocene time the out of sequence growth may reflect a taper subcriticality stage of the apenninic thrust wedge which induced renewed contraction in the rear

active crustal extension in the central apennines italy inferred from gps measurements in the interval 1994 1999 we present the first gps estimate of crustal extension in the central apennines italy through the analysis of the deformation of a sub network of the national gps geodetic network igm95 in the interval 1994 1999 the selected sub network spans the entire active deformation belt perpendicularly to its axis and allows the evaluation of 1 the total extension rate absorbed in this sector of the apennines and 2 the seismogenic potential of the normal faults active in the late pleistocene holocene interval within the network results of this reoccupation are consistent with an extensional strain rate of 0 18 10 6 yr 1 concentrated in an area of about 35 km width giving an average extension rate of 6 2 mm yr across the central apennines the pattern of active deformation suggests active elastic strain accumulation on the westernmost of the two fault systems active in the late pleistocene holocene interval and may also suggest the presence of another active fault system not recognized so far

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

structural constraints on the tertiary plate tectonic evolution of italy abstract eight cross sections six of which were balanced and restored using the principles of thin skinned tectonics demonstrate the reinterpretation of the apennine and sicilian mountains as a detached fold and thrust belt the thin skinned interpretation constrains the extent of the restored continental margins and the amount percentage direction and timing of tectonic shortening allowing the development of a plate tectonic model late cretaceous and paleogene subduction to the north beneath the corsica sardinia calabria csc microplate causes rifting from se france and the development of oceanic crust between the two in the oligo miocene the late oligocene collision of adria and northernmost csc pins the northern edge of the csc plate causing its counter clockwise rotation and its mid miocene suturing between italy and sicily the n s convergence of africa and europe with counter clockwise rotation of italy causes shortening in the nne ssw direction in italy and sicily from 20 10 ma the n s compression extrudes calabria to the se causing mio pliocene compression in southern italy and eastern sicily at the same time as extension and alkaline volcanism in central italy

controlled source nonlinear tomography a powerful tool to constrain tectonic models of the southern apennines orogenic wedge italy the anatomy of the southern apennines is a matter of compelling debate both thick and thin skinned tectonic models are proposed due to paucity of deep seismic constraints we present new and well defined information on the velocity structure of the mountain range by using an innovative nonlinear tomographic technique applied to refraction wide angle reflection data the velocity interface model shows a high velocity region with values exceeding 7 km s at 8 9 km depth such large velocities cannot be related to sedimentary rocks and imply the presence of shallow crystalline rocks i e the basement involvement in the thrust belt the integration of our results with other geophysical data local earthquake tomography bouguer and magnetic anomalies confirms this interpretation which strongly supports thick skinned tectonics and has significant implications for the seismotectonics and hydrocarbon potential of the southern apennines our inversion approach can be effective in other orogenic wedges when seismic reflection profiling fails to uniquely resolve deep complex structures

a transient analysis of slope stability following drawdown after flooding of a highly plastic clay the stability of slopes at bridge abutments across the carrot river in east central saskatchewan was not influenced significantly by drawdown after flooding in the spring of 1995 traditional metho

comment on an alternative view on the origin of chemical and isotopic patterns in groundwater from the milk river aquifer canada by m j hendry and f w schwartz wrr 1988 24 10 1747 1763

holocene geomorphology and stratigraphy of the lower falcon valley dinosaur provincial park alberta canada a tributary of the red deer river in dinosaur provincial park southern alberta contains evidence of a sequence of valley cutting and the deposition of three alluvial fills and one eolian deposit with the exception of the eolian deposit and minor amounts of shield and cordilleran rocks the sediments are derived from local bedrock incision of the bedrock valley occurred in the early postglacial period about 14 000 12 000 bp by rapid drainage of proglacial lakes and meltwaters the valley was subsequently partly infilled as locally fed stream discharges declined during the early to middle holocene by 6000 5000 bp alluvial fans had formed along the base of the valley walls fan development was followed by two phases of stream entrenchment and alluvial deposition including the most recent phase of cutting and filling that began approximately 800 bp the erosional and depositional events may reflect climatic changes as inferred in lacustrine deposits in southern alberta and in valleys elsewhere in the

thick skinned tectonics in the external apennines italy new evidence from magnetic anomaly analysis 1 we discuss the tectonic implications of a new residual magnetic map of the apennine belt adriatic apulian foreland obtained by integrating ground and offshore data sets chiappini et al 2000a negative anomalies are documented over the adriatic apulian foreland areas whereas the external apennine belt is characterized by a ubiquitous low amplitude 30 nt long wavelength positive anomaly in the central northern apennines three 100 km wide more intense 100 200 nt round shaped anomalies are superimposed to the long wavelength feature finally in the tyrrhenian sea and margins high intensity short wavelength positive negative couplets coincide with magmatic outcrops or bodies at shallow depth the low amplitude anomaly pattern over italy suggests that the magnetic basement beneath the triassic evaporites is ubiquitously incorporated in the external belt compressive fronts implying a thick skinned tectonic style for the external apennines the new residual magnetic map resolves the inconsistency between previous aeromagnetic data agip spa italia 1981 which suggested a lack of basement involvement in the apennine belt and recent seismic data which imaged deep reflectors penetrating the basement two magnetic models along ne sw transects in the northern and southern apennines suggest consistent structural styles in the northern apennines positive anomalies roughly coincide with the external compressive fronts although there are local second order differences between the belt front and the edges of the anomaly here the magnetic data show that the basement rises southwestward along the thrust fronts from 6 7 km depth in the adriatic foreland to 2 3 km depth in the axial belt where some exploration wells have penetrated basement within the belt front basement exhumation is inferred to occur along high angle low displacement thrust faults inverting preexisting normal faults in the southern apennines a remarkable positive magnetic anomaly is parallel with and tens of kilometers southwest of the belt front seismic data and oil wells show that the basement surface cannot be shallower in the belt than in the foreland therefore the observed magnetic anomaly is produced by strongly magnetic basement beneath the belt likely an internal crustal wedge tectonically interposed between the apulian carbonate sequences and basement

three dimensional earthquake locations and upper crustal structure of the sannio matese region southern italy abstract the sannio matese region is one of the most seismically active regions of italy and has been struck by large historical earthquakes at present the area is characterized by low magnitude background seismicity and small seismic sequences following m 4 main events in this paper we show vp and vp vs models and 3d locations for a complete set of earthquakes occurring in the period 1991 2001 we observe a significant crustal heterogeneity with large scale east verging high vp fault related folds stacked by the pliocene compression the relocated earthquakes cluster along a 70 east dipping nw striking plane located at the border of the high vp thrust units normal fault earthquakes related to the young and active extension occur within these high vp zones interpreted as high strength material we expect large future earthquakes to occur within these high vp zones actually characterized by low magnitude seismicity at their borders

seismic waves velocities and anisotropy in serpentinized peridotites from xigaze ophiolite abundance of serpentine in slow spreading ridge the effect of serpentinization on seismic wave velocity and anisotropy has been analysed in 6 peridotite samples of the xigaze ophiolite having harzburgitic composition and a degree of serpentinization ranging from 3 to 70 we found i p and s wave velocities are linearly correlated with serpentine content ii anisotropy of p and s waves decreases with increasing serpentinization while in fresh peridotites anisotropy is of the order of 6 for 70 of serpentinization it drops to 1 for p waves and to 2 for s waves comparison of published laboratory velocity data in oceanic lithologies like gabbros and dolerites with serpentinized peridotite data shows the difficulty of distinguishing between gabbros and peridotites having a percentage of serpentine between 10 and 40 by seismic waves velocities only this comparison suggests that seismic velocity data are consistent with the existence of partialy serpentinized peridotites up to 40 of serpentinization in the oceanic crust formed at slow spreading ridges in accordance with geological observation

deep structure of the southern apennines italy thin skinned or thick skinned 1 the deep structure of the southern apennines sa accretionary wedge is still debated since industrial seismic reflection and well data provide reliable constraints only to a depth of about 10 km as a consequence two directly linked questions regard 1 the shortening in the accretionary prism particularly within the buried apulian thrust units and 2 the degree of involvement of the lower plate basement i e the apulian crystalline basement to address these issues we have constructed a regional section along a recently released deep seismic reflection profile crop 04 which intersects the entire sa the resulting cross section adequately constrained to a depth of about 15 km has been framed in a geodynamic scenario characterized by the eastward roll back of the westward subducting apulo adriatic lithosphere on the basis of this section we speculate on the deep structure building both thin and thick skinned thrust models a cross check of these end members models against documented tectonic geophysical and geochemical features shows that the thin skinned model is generally more consistent with the available data the development of basement slices with thicknesses of tens of kilometers is unlikely while it remains possible that the apulian basement could have been involved with its upper few kilometers in the thin skinned model the total shortening of the allochthonous units i e apennine and apulian carbonate platforms and lagonegro basin is estimated to be greater than 280 300 km some 90 km of shortening can be attributed to the apulian thrust units

structural control on fault geometry example of the grevena ms 6 6 normal faulting earthquake in this paper we present a three dimensional velocity structure of the kozani grevena region a relatively low seismicity area of the western margin of the internal hellenides which was struck by a ms 6 6 earthquake on may 13 1995 p wave arrival times from 656 aftershocks are inverted to resolve the velocity structure of the upper 12 km of the crust the 1995 ruptured fault dheskati fault lies at the southeastern end of a 35 km long normal fault the servia fault the crustal heterogeneities identified by tomography help to constrain the geometry and structure of the 1995 fault and the rupture evolution during the mainshock the aftershocks and the velocity structure define a fault dipping 35 toward nw which from 5 km depth splays upward into two nearly parallel shallow faults the slip during the mainshock and the aftershocks all were concentrated along the deeper portion of the fault while the limited slip observed at the surface occurred on the northern of the two shallower splays the paleochori fault it appears that the lithological heterogeneities of the shallow crust are responsible for the splaying of the main fault upward our work stresses the importance of crustal structure in determining fault geometry and segmentation and rupture evolution

landform and sediment imprints of fast glacier flow in the southwest laurentide ice sheet evidence for former fast glacier flow ice streaming in the southwest laurentide ice sheet is identified on the basis of regional glacial geomorphology and sedimentology highlighting the depositional processes associated with the margin of a terrestrial terminating ice stream preliminary mapping from a digital elevation model of alberta identifies corridors of smoothed topography and corridor parallel streamlined landforms megaflutes to mega lineations that display high levels of spatial coherency ridges that lie transverse to the dominant streamlining patterns are interpreted as a series of minor recessional push moraines b thrust block moraines or composite ridges hill hole pairs constructed during readvances surges and c overridden moraines cupola hills apparently of thrust origin together these landforms demarcate the beds and margins of former fast ice flow trunks or ice streams that terminated as lobate forms localised cross cutting and or misalignment of flow sets indicates temporal separation and the overprinting of ice streams lobes the fast flow tracks are separated by areas of interlobate or inter stream terrain in which moraines have been constructed at the margins of neighbouring competing ice streams outlet glaciers this inter stream terrain was covered by more sluggish non streaming ice during full glacial conditions thin tills at the centres of the fast flow corridors in many places unconformably overlying stratified sediments suggest that widespread till deformation may have been subordinate to basal sliding in driving fast ice flow but the general thickening of tills towards the lobate terminal margins of ice streams outlet glaciers is consistent with subglacial deformation theory in this area of relatively low relief we speculate that fast glacier flow or streaming was highly dynamic and transitory sometimes with fast flowing trunks topographically fixed in their onset zones and with the terminus migrating laterally the occurrence of minor push moraines and flutings and associated landforms because of their similarity to modern active temperate glacial landsystems are interpreted as indicative of ice lobe marginal oscillations possibly in response to seasonal climatic forcing in locations where meltwater was more effectively drained from the glacier bed further north the occurrence of surging glacier landsystems suggests that persistent fast glacier flow gave way to more transitory surging possibly in response to the decreasing size of ice reservoir areas in dispersal centres and also locally facilitated by ice bed decoupling and drawdown initiated by the development of ice dammed lakes copyright 2008 john wiley sons ltd

mantle exhumation at passive margins abstract laboratory models of lithosphere necking have been used to study the modes of passive margin formation and related mantle exhumation at continent ocean boundary four layer models were constructed with sand and silicone putty to represent the brittle and ductile layers respectively of both crust and mantle it is shown that necking of the whole lithosphere model is nearly symmetrical pure shear but that asymmetrical structures simple shear develop internally due to heterogeneous boudinage and or faulting of brittle layers relative movements between brittle layers is accommodated by layer parallel shear in the ductile layers defining a set of conjugate shear zones with increasing stretching lower crust and mantle shear zones become juxtaposed as the lower ductile mantle layer rises up through the separation zone of boudins in the brittle layer the experimental results are used to propose a general model of passive margin formation leading to mantle exhumation they are also compared to the situation observed on the west iberia margin the exhumation of lithosphere mantle is the result of a bulk pure shear at lithospheric scale shearing of exhumed mantle rocks does not correspond to detachment faults cross cutting the whole lithosphere at the onset of rifting but results from heterogeneous stretching and boudinage of the high strength sub moho mantle

depth localized azimuthal anisotropy from sks and p receiver functions the tien shan summary shear wave splitting in the seismic sks phase provides a unique possibility to judge on deformations at depths inaccessible for direct observations fast s wave polarization direction in collisional belts is often parallel to the trend of the belt although deformations of the mantle lithosphere in low angle thrusts would lead to the fast polarization direction normal to the trend of the belt these considerations suggested that the upper mantle in collisional belts is decoupled from the crust however sks technique is notable by a poor depth resolution and usually it assumes that the fast polarization direction is the same at any depth which is hard to justify here to investigate depth dependent azimuthal anisotropy in the mantle we invert jointly p receiver functions and sks particle motions at a number of seismograph stations the technique involves azimuthal filtering of the receiver functions and provides a criterion to discriminate between the effects of azimuthal anisotropy and lateral heterogeneity of isotropic medium a search for the optimum models is conducted with a technique similar to simulated annealing testing with synthetics demonstrates that this approach is robust the results for 10 seismograph stations in the tien shan the world s most active intracontinental collisional belt in central asia reveal a pronounced change in the patterns of azimuthal anisotropy at a depth around 100 km in the mantle lithosphere at depths less than 100 km anisotropy is relatively weak and fast wave polarization direction varies laterally in a broad range this layer is not necessarily decoupled from the crust its anisotropy can be a combined effect of present day thrusting and of deformations of the geologic past in the lower layer asthenosphere the average azimuth of fast wave polarization is close to the trend of the belt whereas magnitude of s wave anisotropy is stable and large between 5 and 6 per cent this anisotropy is a likely result of recent uniaxial shortening at right angle to the trend of the belt at some stations the data require anisotropy in the crust there is no evidence for anisotropy at depths exceeding 150 250 km

glacial geomorphology of terrestrial terminating fast flow lobes ice stream margins in the southwest laurentide ice sheet glacial geomorphological mapping of southern alberta canada reveals landform assemblages that are diagnostic of terrestrial terminating ice streams fast flowing outlet glaciers with lobate snouts spatial variability in features that comprise the landform assemblages reflects changes in a palaeo ice stream activity switch on off and b snout basal thermal regimes associated with climate sensitive steady state flow palaeo ice stream tracks reveal distinct inset sequences of fan shaped flowsets indicative of receding lobate ice stream margins former ice lobe margins are demarcated by a major often glacially overridden transverse moraine ridges commonly comprising glacitectonically thrust bedrock and b minor closely spaced recessional push moraines and hummocky moraine arcs details of these landform types are well exhibited around the former southern margins of the central alberta ice stream where larger scale more intensive mapping identifies a complex glacial geomorphology comprising minor transverse ridges mtr types 1 3 hummocky terrain ht types 1 3 flutings and meltwater channels spillways the mtr type 1 constitute the summit corrugation patterns of glacitectonic thrust moraines or major transverse ridges and have been glacially overrun and moderately streamlined the mtr type 2 sequences are recessional push moraines similar to those developing at modern active temperate glacier snouts the mtr type 3 document moraine construction by incremental stagnation because they occur in association with hummocky terrain the close association of hummocky terrain with push moraine assemblages indicates that they are the products of supraglacial controlled deposition on a polythermal ice sheet margin where the ht type 3 hummocks represent former ice walled lake plains the ice sheet marginal thermal regime switches indicated by the spatially variable landform assemblages in southern alberta are consistent with palaeoglaciological reconstructions proposed for other ice stream fast flow lobes of the southern laurentide ice sheet where alternate cold polythermal and temperate marginal conditions associated with climate sensitive steady state flow sequentially gave way to more dynamic streaming and surging activity

diffusion as the main process for mass transport in very low water content argillites 2 fluid flow and mass transport modeling 1 on the basis of chloride concentrations of pore water in the tournemire massif part 1 a conceptual model for mass transport in argillites by diffusion is proposed from this conceptual model and current knowledge of the geological history of the massif one dimensional numerical simulations are formulated for chloride transport in tournemire massif over the past 53 ma good agreement between experimental data and calculated values for both diffusion coefficients and concentrations of chloride confirms that diffusion is the main process for mass transport in the massif this model is also tested using deuterium contents of pore water applying variable concentrations to meteoric water circulating in system boundary layers based on the thermal dependency of its isotopic composition these simulations reveal the likely important role of lithologic heterogeneities such as fractures in the horizontal distribution of tracer concentrations

continental subduction and three dimensional crustal structure the northern south island new zealand the three dimensional vp and vp vs structure of a region where subduction transitions to oblique transform faulting has been determined using arrival times from 579 local earthquakes recorded during a temporary deployment and 3146 earthquakes have been relocated between 40 km and 100 km depth the subducted plate is imaged as a relatively low velocity feature in the uppermost mantle reflecting the continental nature of the subducted crust in this region an increase in amplitude of this low velocity feature from northeast to southwest can be related to an increase in the thickness of the crust of the subducted plate in this direction velocity variations within the subducted and overlying plates show some spatial correlation this suggests an interaction between the plates which extends well beyond the plate interface and is consistent with other geophysical and geological evidence that the plate interface beneath marlborough is currently not accommodating much active subduction in the overlying plate the awatere fault is a major structural feature associated with a low velocity zone extending to 23 km depth there is a marked change in structure near this fault with seismic velocities being lower to the southeast a relatively high level of seismicity occurs in this region of lower seismic velocities suggesting a relationship between the two a possible explanation for this is elevated pore pressures caused by fluids derived from dehydration of the continental subducted crust the low velocity region in the overlying plate coincides with the region of most intense active deformation suggesting it is relatively weak

trench investigations of the 1915 fucino earthquake fault scarps abruzzo central italy geological evidence of large historical events earthquake hazard analyses in italy are mainly based on historical seismic catalogs however the completeness of the italian catalog which spans more than 2000 years progressivcly decreases going back in time in the fucino basin historical research has not produced evidence of large earthquakes before the january 13 1915 event m s 7 0 33 000 people killed this event generated surface faulting along at least two parallel quaternary normal faults bounding the eastern side of the basin the celano gioia and parasano cerchio faults over an end to end length of about 23 km with a downthrow of 30 90 cm toward southwest to improve geological aspects of the seismic history of this area we trenched onc of the coseismic scarps along the celano gioia fault at a trench site near the village of san benedetto de marsi the fault traverses the area formerly covered by the fucino lake drained for farming in 1875 a d the evidence collected in the trenchcs suggests at least two large events in historical times before 1915 radiocarbon dates constrain the age of event b between the 6th and the 9th centuries a d possibly coinciding with the cvent felt in rome in 801 a d molin arid guidoboni 1989 event a probably occurred after the 10th ccntury a d and almost certainly before the 1349 a d earthquake because historical studies show 1 that event a was not produced during the earthquake sequence that occurred in central italy in 1349 a d molin and guidoboni 1989 and 2 that the post 1349 seismic catalog can be regarded as complete for surface faulting earthquakes surface displacements determined for events a and b compared to the 1915 surface faulting indicate that m 6 5 earthquakes were associated with each rupturc these obscrvations suggest that the return period for large earthquakes in the fucino basin is shorter than that indicated by the historical record alone the fucino example clearly shows that thc cxceptionally long historical record in italy is still inadequate for a comprehcnsive seismic hazard characterization

slip history of the magnola fault apennines central italy from 36cl surface exposure dating evidence for strong earthquakes over the holocene to better understand the mechanics of deformation in the mediterranean and the role that the convergence between africa and europe plays it is necessary to know the deformation field at different time scales here we use in situ 36 cl surface exposure dating of exposed bedrock fault scarps to determine earthquake time slip histories and to quantify slip rates over the last several thousand years this information allows us to delineate the seismic history of normal faulting within the mediterranean area over that time period we have studied the limestone scarp produced by the magnola fault in the central apennines italy the magnola fault in the fucino area is an active 15 km long normal fault striking wnw and dipping ssw the range front morphology characterised by steep triangular facets separated by v shaped valleys and wine glass canyons suggests that the magnola fault has been active for at least the last several hundred thousand years at the base of the facets the fault cuts limestone bedrock to produce a well preserved normal fault scarp 10 to 12 m high the distribution of 36 cl concentration versus the height along that scarp is best explained by a minimum of five and a maximum of seven successive earthquake exhumations with slips varying between 1 5 and 3 m an age of 5 ka at the base of the scarp and of 12 ka at the top yields a slip rate of 0 8 mm year the absence of any event on this fault during the last 5000 years suggests either that a future event is imminent on the magnola fault or that the fault has entered a quiescent period with

tomographic inversion of local earthquake data from the hengill grensdalur central volcano complex iceland parameters is generally low however a quantitative analysis of resolution provides an unambiguous assessment of well resolved volumes within the better resolved regions of the model the averaging volumes are 1 2 km and 2 4 km in vertical and horizontal extent respectively results of tomographic inversion image three distinct bodies of anomalously high velocity two of these extend from near the surface to a depth of about 3 km these high velocity volumes are located directly beneath the surface expressions of the extinct grensdalur volcano and the extinct husmuli basalt shield the third high velocity structure occurs in the depth range of 3 4 km but does not extend to the surface these three high velocity bodies are interpreted to be solidified magmatic intrusions relatively low velocities underlay limited portions of the trace of the present accretionary axis and a low velocity body is imaged in the roots of the active hengill volcano the volume of lower velocities located beneath the surface expression of the hengill volcano is interpreted to be a region of partial melt

active tectonics of the adriatic region from gps and earthquake slip vectors 1 to investigate the kinematics of the adriatic region we integrate continuous and episodic gps measurements with mw 4 5 earthquake slip vectors selected from the regional centroid moment tensor catalogue coherent motion of gps sites in the po valley in apulia and in the hyblean plateau allows us to estimate geodetically constrained angular velocities for these regions the predictions of the gps inferred angular velocities are compared with the earthquake slip vectors showing that the seismically expressed deformation at the microplate boundaries is consistent with the observed geodetic motion the remarkable consistency between geodetic seismological and geological evidence of active tectonics suggests that active deformation in the central adriatic is controlled by the relative motion between the adria and apulia microplates the microplates angular rotation rates are then compared with the rotation rates calculated with a simple block model supporting the hypotheses 1 that apulia forms a single microplate with the ionian sea and possibly with the hyblean region and 2 that adria and apulia rotate in such a way as to accommodate the eurasia nubia relative motion we suggest that the present day microplate configuration follows a recent fragmentation of the adriatic promontory that during the neogene rigidly transferred the africa motion to the orogenic belts that now surround the adriatic region

upper crustal structure of the benevento area southern italy fault heterogeneities and potential for large earthquakes summary the benevento region is part of the southern apennines seismogenic belt which experienced large destructive seismic events both in historical and in recent times the study area lies at the northern end of the irpinia fault which ruptured in 1980 with a ms 6 9 normal faulting event which caused about 3000 casualties the aims of this paper are to image lateral heterogeneities in the upper crust of the benevento region and to try to identify the fault segments that are expected to generate such large earthquakes this work is motivated by the recognition that lithological heterogeneities along major fault zones inferred from velocity anomalies reflect the presence of fault patches that behave differently during large rupture episodes in this paper we define the crustal structure of the benevento region by using the background seismicity recorded during 1991 and 1992 by a local seismic array these data offer a unique opportunity to investigate the presence of structural discontinuities of a major seismogenic zone before the occurrence of the next large earthquake the main result that we obtained is the delineation of two nw trending high velocity zones hvzs in the upper crust beneath the matese limestone massif these high velocities are interpreted as high strength regions that extend for 30 40 km down to at least 12 km depth the correspondence of these hvzs with the maximum intensity regions of historical earthquakes 1688 ad 1805 ad suggests that these anomalies delineate the extent of two fault segments of the southern apenninic belt capable of generating m 6 5 7 earthquakes the lateral offset observed between the two segments from tomographic results and isoseismal areas is possibly related to transverse right lateral faults

paleoseismicity of the ovindoli pezza fault central apennines italy a history including a large previously unrecorded earthquake in the middle ages 860 1300 a d geomorphic and trenching investigations along the ovindoli pezza fault show that this normal fault is one of the major seismogenic faults in the central apennines we found clear geological evidence for three holocene surface faulting earthquakes on this fault the most recent earthquake occurred in the middle ages between 860 and 1300 a d the penultimate occurred about 1900 b c or shortly after and the oldest probably occurred between 3300 and 5000 b c although the most recent surface faulting earthquake occurred during historical time no evidence for it have been found in the historical record slip per event ranges between 2 and 3 m and the length of the rupture is at least 12 20 km suggesting m 6 5 7 0 for the paleoearthquakes the dip slip rate determined from trenching is 0 7 1 2 mm yr and is consistent with the long term slip rate of 0 9 2 5 mm yr lower values preferred obtained from displaced geomorphic features trench data combined with long term slip rate estimates suggest the recurrence interval is longer than a millennium and possibly as long as 3300 years the time elapsed since the most recent earthquake is 700 1130 years the seismic behavior of the ovindoli pezza fault is consistent with other well known seismogenic faults of the central and southern apennines the lack of mention or mislocation of the most recent event on the ovindoli pezza fault in the historical record of the past two millennia should be attributed mainly to the unsettled cultural and social conditions and poor economic state that characterized the middle ages especially in thinly populated regions such as the central apennines this example highlights an intrinsic limit of the historical data and raises the possibility that other regions considered seismically quiet on the basis of a long historical record may in reality have had large earthquakes that were not recorded

structural architecture of the central apennines interpretation of the crop 11 seismic profile from the adriatic coast to the orographic divide 1 we present an interpretation of the eastern half portion of the crop 11 line a deep reflection seismic profile 265 km long that cuts across the central apennines from the tyrrhenian coast to the adriatic coast in the study area the line cuts across a pile of thrust sheets that underwent tectonic transport between the messinian and the pleistocene in its easternmost part the line runs through the plio pleistocene deposits of the adriatic foredeep in the foreland region the crop 11 line integrates previous information on the crustal structure derived from petroleum exploration and from deep seismic sounding refraction experiments in particular the crop 11 line confirms the existence of a very thick sedimentary sequence underlying the mesozoic tertiary carbonates of the apulia platform interpreted as the paleozoic triassic sedimentary cover of a pre cambrian crystalline basement in the mountain chain where the base thrust of the orogenic wedge reaches a depth of about 25 km this sedimentary sequence appears to be the deepest geological unit incorporated in the thrust system this interpretation of the crop 11 profile suggests an unusual thin skin tectonic style implying the detachment from the original basement and the incorporation in the post tortonian tectonic wedge of a very thick paleozoic triassic sedimentary sequence possibly affected by low grade metamorphism in the lower part other new suggestions from the crop 11 seismic data concern the origin of the fucino basin one of the most remarkable plio pleistocene intramontane basins the normal faults bordering this structural depression as other important normal faults present in the central apennines e g the caramanico fault system in the majella region seem to have been controlled by gravitational collapse processes driven by uplift during crustal shortening rather than by a generalized extension subsequent to the apennine compression as usually reported in the geological literature if this interpretation is correct the strong seismic activity in correspondence to the apennine watershed may be related to the very recent increase in the structural relief caused by an out of sequence propagation of the active thrusts

seismic properties of the upper crust in the central friuli area northeastern italy based on petrophysical data abstract the compressional and shear wave velocities have been measured at room temperature and pressure up to 450 mpa on 5 sedimentary rock samples representative of the most common lithologies of the upper crust in the central friuli area northeastern italy at 400 mpa confining pressure the triassic dolomitic rock shows the highest velocities vp 7 km s vs 3 6 km s the jurassic and triassic limestones samples intermediate velocities vp 6 3 s vs 3 5 km s and the cenozoic and paleozoic sandstones the lowest velocities vp 6 15 km s vs 3 35 km s the paleozoic sandstone sample is characterized by the strongest anisotropy 10 and significant birefringence 0 2 km s is found only on the cenozoic sandstone sample we elaborated the synthetic profiles of seismic velocities density elastic parameters and reflection coefficient related to 4 one dimensional geological models extended up to 22 km depth the synthetic profiles evidence high rheological contrasts between triassic dolomitic rocks and the soft sandstones and the jurassic limestones the vp profiles obtained from laboratory measurements match very well the in situ vp profile measured by sonic log for the limestones and dolomitic rocks supporting our one dimensional modelling of the calcareous carbonatic stratigraphic series the vp and vs values of the synthetic profiles are compared with the corresponding ones obtained from the 3 d tomographic inversion of local earthquakes the laboratory vp are generally higher than the tomographic ones with major discrepancies for the dolomitic lithology the comparison with the depth location of seismicity reveals that the seismic energy is mainly released in correspondence of high contrast rheological boundaries

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

seismicity in central and northern apennines integrating the italian national and regional networks abstract in this paper we present and discuss an improved picture of the seismicity distribution of the umbria marche abruzzi apennines as obtained through the integration of the national and the regional seismic networks operating from 2002 to 2006 during this period both the istituto nazionale di geofisica e vulcanologia ingv national seismic network and the regional networks have been greatly improved we compare the results of the integrated catalogue obtained in this study with the catalogue of the italian seismicity between 1981 and 2001 castello b selvaggi g chiarabba c amato a 2006 csi catalogo della sismicita italiana 1981 2002 versione 1 1 ingv cnt roma http legacy ingv it csi confirming the basic known features of the seismic activity in the region but also evidencing some original and interesting results in particular the new data set allows us to better define the geometry and kinematics of the crustal seismicity which is confined to the upper 20 km and shows a clear general deepening from west to east in the crust we find additional evidence of extensional seismicity below the central portion of the belt and thrust reverse faulting mechanisms at the outer fronts of the apennines looking at the seismicity along the belt it is also possible to observe aseismic regions which could be due to either locked or creeping portions of the apenninic fault system at greater depth the west dipping seismicity distribution down to about 70 km confirms the hypothesis of a slab of adriatic lithosphere subducted below the apennines but also suggests that there are strong lateral heterogeneities and possibly tears in the slab

vp and vp vs images in the mw 6 0 colfiorito fault region central italy a contribution to the understanding of seismotectonic and seismogenic processes 1 in 1997 the umbria marche apennines central italy was struck by a series of moderate magnitude normal faulting earthquakes accompanied by a prolonged sequence of aftershocks seismological analysis revealed a 40 km long nw trending structure composed by several low angle normal fault segments in this paper we present the three dimensional 3 d vp and vp vs structure of the fault zone determined by the inversion of p and s wave arrival times from 1982 aftershocks the high resolution tomographic images reveal strong heterogeneity along and across the fault zone and allow us along with the 3 d location of earthquakes to define the fault geometry at depth and to improve our understanding on the seismotectonics of this part of the northern apennines thrust and fold belt the relocated aftershocks suggest that the main ruptures occurred on planes slightly steeper than previously hypothesized and at depths shallower than those evidenced by 1 d locations we find that the preexisting structure which developed during the neogene compressional tectonics plays an important role in the earthquake generation and rupture evolution of the normal faulting events we propose that the main shocks whose hypocenters are all located at 6 km depth originated along a shallow decollement of the meso cenozoic cover thrust over the metamorphic basement geometrical discontinuities and lateral steps along the inherited structures control the lateral fault extent and determine fault segmentation this study offers a good example of how lithological heterogeneities and the complexity of the upper crust structure strongly affect the faulting process

tomographic constraints on the geodynamic evolution of the italian region in this paper we present p wave tomographic images of the mantle beneath italy obtained by inverting 6000 teleseismic p and pkp wave arrival times accurately repicked recorded in the time period 1988 1994 by the stations of the national seismic network of the istituto nazionale di geofisica we pay great attention in the data selection and picking procedure of seismic phases to obtain a very high quality data set the data were inverted with the well established aki christofferson husebye tomographic technique different reference models and residuals computation have been tried to verify the stability of the results the high quality of the repicked arrival times allows us to enhance the definition of the deep structures beneath both the alps and the apennines looking for their lateral and vertical continuity down to 800 km depth the main finding of this study is a continuous high velocity body located between 250 and 670 km depth beneath the entire apenninic system dipping toward the tyrrhenian area which continues upward segmented in two main anomalies in the northern apenninic and the calabrian arcs we interpret this high velocity feature as the subducted oceanic lithosphere between the eurasian and african plates dipping down to the upper lower mantle boundary beneath the tyrrhenian sea the retrieved images of the lithosphere subducting beneath apennines are reliable in terms of thickness about 80 90 km and p wave velocity contrast 2 4 higher than the normal mantle furthermore our tomographic images which focus on the deep geometry and continuity of the velocity structures provide new keys to understanding the geodynamic evolution of the italian region the segmentation of the high velocity slab upward suggests a complex evolution of the arc trench system and the initially continuous subduction of the ionian adriatic plate progressively developed in subordinate arcs probably due to lateral heterogeneity of the subducting lithosphere

a gravel diamicton lag on the south albertan prairies canada evidence of bed armoring in early deglacial sheet flood spillway courses a clast supported massive diamicton to poorly sorted massive gravel gm dcm bed in the area around dinosaur provincial park southern alberta canada provides a means of identifying early deglacial flood courses this is especially useful where flood and spillway courses have very subtle geomorphic definition and are difficult to map from aerial photographs the gm dcm bed conformably overlies a brown late wisconsinan till and rarely overlies bedrock and lacustrine sediments the geographic distribution of the bed is restricted to flat to gently undulating prairie on either side of the red deer river where shallow floods and spillway melt waters were concentrated upon deglaciation the bed has also been observed along the banks of the south saskatchewan river at medicine hat 90 km to the south and is therefore regionally extensive because the gm dcm bed has none of the attributes of supraglacial sediment and possesses a clast fabric and sphericity very similar to those of underlying till it is interpreted as a winnowed gravel diamicton lag which was produced by low competence melt water floods along shallow depressions in the prairie surface after the drainage of local proglacial lakes after enough of the fine grained matrix of the late wisconsinan till was removed to create a lag

nondilatant brittle deformation of serpentinites implications for mohr coulomb theory and the strength of faults we conducted deformation experiments to investigate the strength deformation processes and nature of the brittle ductile transition of lizardite and antigorite serpentinites a transition from localized to distributed deformation occurs as confining pressure increases from 200 to 400 mpa at room temperature deformation in both brittle localized and ductile distributed regimes is accommodated by shear microcracks which form preferentially parallel to the 001 cleavage axial microcracks mode i are infrequently observed volumetric strain measurements demonstrate that brittle deformation is mostly nondilatant consistent with the shear dominated microcracking three observations indicate that deformation in the ductile regime is accommodated by cataclastic flow 1 a lack of evidence for crystal plastic deformation 2 a positive pressure dependence of the maximum differential stress and 3 abundant evidence for brittle microcracking the weakness of serpentinites relative to other brittle rocks is explained by a low fracture strength along the 001 cleavage combined with the low pressure dependence of strength the transition from brittle to ductile deformation occurs at the crossover between the strength of intact serpentinite and the friction law unique to each type of serpentinite rather than the more general byerlee s law if brittle deformation regimes are defined based on the mode of microcracking and on the occurrence of crystal plasticity serpentinites define an end member style of nondilatant brittle deformation this deformation style may result in extremely weak faults in nature and it may also strongly influence the tectonic evolution of the oceanic lithosphere where serpentinite is present

background seismicity in the central apennines of italy the abruzzo region case study abstract we investigate background seismic activity of the abruzzo region a 5000 km2 area located within the central apennines of italy where in the past 600 years at least 5 large earthquakes i xi x have occurred between april 2003 and september 2004 a dense temporary seismic network composed of 30 digital three component seismic stations recorded 850 earthquakes with 0 9 the seismicity occurs at a low and constant rate of 2 6 e 04 events day km2 and is sparsely distributed within the first 15 km of the crust minor increases in the seismicity rate are related to the occurrence of small and localised seismic sequences that occur at the tip of major active normal faults along secondary structures we observe that during the 16 months of study period the fucino fault system responsible for the 1915 fucino earthquake ms 7 0 and the major normal faults of the area did not produce significant seismic activity fault plane solutions evaluated using p wave polarity data show the predominance of normal faulting mechanisms 55 with ne trending direction of extension coherent with the regional stress field active in this sector of the apennines around 27 of the focal solutions have pure strike slip mechanisms and the rest shows transtensional faulting mechanisms that mainly characterise the kinematics of the secondary structures activated by the small sequences we hypothesize that the largest known nw trending normal faults are presently locked and we propose that in the case of activation the secondary structures located at their tips may act as transfer faults accommodating a minor part of the extensional deformation with strike slip motion

active oblique extension in the central apennines italy evidence from the fucino region the fucino basin is a flat quaternary depression within the central apennines it is surrounded by active normal faults with small oblique slip components surface faulting was observed along the east side of the basin during the ms 7 0 avezzano earthquake of 1915 in order to understand the kinematics of recent strain better and to assess the seismic hazard of this region we carried out a detailed geomorphic and structural study of the faults around the basin fault scarp heights were accurately measured with total station profiles and vertical slip rates were estimated assuming slope offsets to post date the end of periglacial abrasion 14 4 kyr bp to the north the most prominent fault the magnola fault appears to have an average postglacial throw rate of 0 7 0 3 mm yr 1 and together with the velino fault to be capable of generating earthquakes of maximum magnitudes of 6 9 7 3 with recurrence intervals of 1000 3000 yr east of the basin the serrone parasano and ventrino faults form a right stepping horsetail of the giovenco fault current vertical slip rates on the three former faults appear to be between 0 5 and 1 4 0 5 and 1 0 and 0 3 and 1 1 mm yr 1 respectively infrequent maximum magnitude earthquakes on them may also exceed 7 particularly in the case of coupled rupture with loosely constrained recurrence intervals up to several thousand years the right lateral slip components implied by the most recent slickensides and by geomorphic offsets on the nw se trending normal faults of the area suggest that the blocks they bound rotate counterclockwise consistent with oblique left slip on the nnw sse trending giovenco and ovindoli faults to the east sinistral shear parallel to the latter faults the maximum relief across the magnola fault and the postglacial slope offsets measured suggest that the extension rate across the central apennines might be of the order of 6 3 mm yr 1 in a n20 10 e direction more northerly than hitherto inferred

upper mantle stratification by p and s receiver functions summary seismic stratification of the upper mantle is investigated by applying two complementary techniques to the records of the graefenberg array in southern germany the anisotropic p receiver function technique kosarev et al 1984 vinnik montagner 1996 is modified by using summary seismic events instead of individual events and different weighting functions instead of the same function for the harmonic angular analysis of the sv and t components of the pds phases the summary events provide better separation of the second azimuthal harmonic than the individual events the parameters of the second harmonics of sv and t thus evaluated should be similar if they reflect the effects of azimuthal anisotropy this can be used as a criterion to identify the anisotropy to detect the sdp phases and their azimuthal variations caused by azimuthal anisotropy we have developed a stacking technique which can be termed the s receiver function technique it includes axis rotation to separate interfering p and s arrivals determination of the principal m component of the s wave motion deconvolution of the p components of many recordings by their respective m components and stacking of the deconvolved p components with weights depending on the level of noise and the angle between the m direction and the backazimuth of the event both techniques yield consistent results for the graefenberg array as indicated by the p receiver functions the upper layer of the mantle between the moho and 80 km depth is anisotropic with dvs vs around 0 03 and the fast direction close to 20 clockwise from north the fast direction of anisotropy below this layer is around 110 the boundary between the upper and the lower anisotropic layers is manifested by the detectable pds and sdp converted phases shear wave splitting in sks is strongly dominated by azimuthal anisotropy in the lower layer asthenosphere

deep structural heterogeneities and the tectonic evolution of the abruzzi region central apennines italy revealed by microseismicity seismic tomography and teleseismic receiver functions abstract the crustal structure of central apennines italy is still poorly defined leaving uncertainties on the tectonic style thin or thick skinned responsible for the development of the thrust and fold belt the today active extension which replaced compression since early quaternary is presumably influenced by the pre existing structure that yields location and segmentation of the fault system to focus on such issues we computed p and s wave velocity models of the crust by using the independent methodologies of local earthquakes tomography and teleseismic receiver function we document strong lateral and vertical heterogeneities that define shallow imbricate sheets of the mesozoic cover that overlay exceptionally high vp and high vs bodies these bodies can be interpreted as either dolomitic or partially hydrated mafic rocks the two alternative interpretations respectively imply an ultra thick deposition of dolomitic rocks in the hanging wall of triassic normal fault or a deep exhumation of the pre mesozoic basement during the early mesozoic sin rift tectonic in both cases these bodies influenced the evolution of the thrust and fold belt very remarkably active normal faults like those ruptured during the still ongoing 2009 l aquila sequence concentrate at the border of these bodies suggesting that they have an active role in the segmentation of the normal fault system the rheological behavior of such high vp high vs bodies weak or strong is still uncertain but of utmost importance to understand the risk of future normal faulting earthquakes

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