evidence of large scale deformation patterns from gps data in the italian subduction boundary abstract we present the velocity field in italy derived from over 300 continuous gps stations operated in the 1998 2009 time span the gps network maps the whole country with a mean inter site distance of about 50 km and provides a valuable source of data to study the ongoing deformation processes in the central mediterranean the estimated horizontal and vertical velocity fields show major significant features and also less known second order kinematic features a general uplift characterizes the whole apennines and alpine belts that follow the topographic ridge whereas the po plain shows a gradually increasing subsidence from west to east the apennines belt displays a distinctive extension 50 80 10 9 yr 1 while compressive tectonic regimes characterize northern sicily eastern alps and the northeast front of the northern apennines 25 50 10 9 yr 1 second order deformation patterns on large scale wavelength 100 km have been detected on the accretionary prism of central and southern apennines that are highly correlated with other geophysical data vp anomalies seismic anisotropy etc and related to deep rooted sections 70 100 km marked by different subduction regimes apparently at this scale length the observed deformations are governed by the lithosphere as a whole we interpret these deformations as a result of different subduction mechanisms such as variations of the subduction rollback velocity affecting different segments of the subduction zone and or to mantle flows in proximity of the slab edges further south in central southern sicily we detect a contraction of 1 1 0 2 mm yr that probably accommodates part of the africa eurasia convergence on the outer thrust front of the apennines maghrebides belt this hypothesis agrees with an independent analysis of the seismicity associated to the sicilian basal thrust thought to be still active the itrf2005 estimates of the new gps velocity field are available also in sinex format as supplementary file s1

the relationships between regional quaternary uplift deformation across active normal faults and historical seismicity in the upper plate of subduction zones the capo d orlando fault ne sicily in order to investigate deformation within the upper plate of the calabrian subduction zone we have mapped and modelled a sequence of late quaternary palaeoshorelines tectonically deformed by the capo d orlando normal fault ne sicily which forms part of the actively deforming calabrian arc in addition to the 1908 messina strait earthquake mw 7 1 this region has experienced damaging earthquakes possibly on the capo d orlando fault however it is not considered by some to be a potential seismogenic source uplifted quaternary palaeoshorelines are preserved on the hangingwall of the capo d orlando fault indicating that hangingwall subsidence is counteracted by regional uplift likely because of deformation associated with subduction collision we attempt to constrain the relationship between regional uplift crustal extensional processes and historical seismicity and we quantify both the normal and regional deformation signals we report uplift variations along the strike of the fault and use a synchronous correlation technique to assign ages to palaeoshorelines facilitating calculation of uplift rates and the fault throw rate uplift rates in the hangingwall increase from 0 4 mm yr in the centre of the fault to 0 89 mm yr beyond its sw fault tip suggesting 0 5 mm yr of fault related subsidence which implies a throw rate of 0 63 0 02 mm yr and significant seismic hazard overall we emphasise that upper plate extension and related vertical motions complicate the process of deriving information on the subduction collision process such as coupling and slip distribution on the subduction interface parameters that are commonly inferred for other subduction zones without considering upper plate deformation

three dimensional instantaneous mantle flow induced by subduction 1 we conduct three dimensional subduction experiments by a finite element approach to study flow around slabs which are prescribed based on a transient stage of upper mantle subduction from a laboratory model instantaneous velocity field solutions are examined focusing on the toroidal vs poloidal components as a function of boundary conditions plate width and viscosity contrast between slab and mantle we show how the slab to mantle viscosity ratio determines the strength of toroidal flow and find that the toroidal flow component peaks for slab mantle viscosity ratios 100 independent of slab width or geometry

a recent tectonic reorganization in the south central mediterranean abstract new geodetic data combined with seismicity geologic and geochemical information document a major tectonic reorganization in the central mediterranean around 0 8 0 5 ma when rapid trench migration and consequent tyrrhenian back arc extension which dominated the region s evolution since the tortonian 10 8 ma essentially stopped in response the african convergence in sicily was transferred to a back thrust in the southern tyrrhenian characterized by frequent m5 6 earthquakes in the last 20 years a diffuse transform boundary formed across northeastern sicily to connect the sicilian and calabrian plate boundaries causing opening of the messina straits home to large historical earthquakes and unusual volcanism in the aeolian island arc and the intraplate mount etna a divergence of the ionian region from the main part of africa with northeastward motions that reflect the joint influence of african push and hellenic slab pull and are transmitted to calabria and adria could explain motions observed in the sicily channel calabria and apulia as well as the high level of southeastern sicilian seismic activity

seismic potential in italy from integration and comparison of seismic and geodetic strain rates abstract seismological and geodetic data provide key information about the kinematics and active tectonics of plate margins focal solutions enable the determining of the directions in which the current tectonic stress acts when fault rupturing occurs gps measurements provide information on the crustal velocity field and on current interseismic strain rates the comparison of the strain rates resulting from the two datasets provides further insight into how large an area is affected by aseismic deformation which is a valuable indicator for seismic hazard mitigation and estimation of the seismic potential in this work we investigate both seismic and geodetic strain rates and the combined field resulting from the joint inversion of the geodetic and seismic datasets providing a picture of the overall deformation field and its variation during the last decades in this way we try to give an overview of the seismic potential distribution across the apennines and southern italy as a qualitative analysis of space time variations in the released seismic strain rate compared to the space time distribution of the cumulated geodetic strain rate the results show a variable distribution of the seismic efficiency over italy the southern apennines shows the greatest seismic potential highlighting a significantly lower seismicity in the last two decades over an area affected by the highest total strain rates the messina straits and eastern sicily have a significant seismic potential together with the calabrian arc from the tindari letojanni and central aeolian islands to the mt pollino area as a result of seismic gaps with respect to the combined strain rates in the investigated period this long gap highlights the longer recurrence periods for the strongest earthquakes on this area the central northern apennines and off shore northern sicily show a lower seismic potential than central southern apennines probably due to the more recent seismicity affecting these areas

structural styles and regional tectonic setting of the gela nappe and frontal part of the maghrebian thrust belt in sicily the gela nappe of south central sicily provides an example of a curved segment of an orogenic front that can be examined both onshore and offshore for deformational style and amount of shortening synorogenic sediments allow the deformation to be dated two distinct structural styles are observed in the gela nappe the central salient part of the nappe caltanissetta basin consists of a single thrust sheet containing a train of continuously tightening folds and the reentrant margins of the nappe sciacca and monte judica consist of a stack of several thrust sheets these different structural styles correspond to the pretectonic mesozoic stratigraphy of the foreland plate carbonate platforms exist on the adventure bank and hyblean plateau ahead of sciacca and monte judica respectively while the caltanissetta basin region appears to have accumulated basinal clay facies where the resistant carbonate stratigraphy provides a buttress to the propagation of the thrust front deformation is taken up by imbrication on steep ramps through the carbonates generating a relatively thick orogenic wedge in the basinal setting where no strong rheology exists the low angle of friction on the clay detachment levels requires the growing thrust wedge to be much thinner with a very low foreland dip hence the thrust front propagates much farther forward into the basin than it does in the adjacent platformal areas producing a nonlinear thrust front in the basinal region accretion of foreland material to the nappe by imbrication was only prominent during the messinian when subaerial exposure prevented low friction transport of the nappe across the highest levels of the stratigraphy a steady thickening of the nappe by internal folding suggests an increase in friction along the basal detachment possibly due to progressive compaction of the clays

test of source parameter inversion of the intensities of a 54 000 death shock of the seventeenth century in southeast sicily we inverted the macroseismic intensity data set felt reports of the m 5 4 earthquake of 1990 in se sicily and retrieved source parameters that were compatible with those obtained independently by other authors who treated instrumental observations our technique uses voronoi polygons and our kinematic function kf after this validation we attempted the inversion of the macroseismic intensity data set of one of the strongest earthquakes that has ever struck the mediterranean basin in 1693 in southeast sicily 54 000 casualties it was possible to invert the regional intensity patterns of these two earthquakes because their data sets are sufficiently uncontaminated by local site responses and retain regional traces of source effects the 1693 source constrained by our inversion is a nne oriented fault approximately 60 km long dipping from 90 to 54 80 with positive error of 10 and negative error of 26 toward ese 50 strike slip and 50 dip slip which crosses se sicily from the hyblean plateau to the coast of the ionian sea south of the city of catania the nucleation is 37 08 n 14 93 e this source best fits the regional distribution of damage observed in the field at the limit of the negative error of the dip angle a value of 54 makes our line source at depth compatible with the trace of the scicli active transcurrent fault which is 12 14 km to the west the retrieved source is also compatible with the orientation of the maximum horizontal geodynamical compressive stress confidently measured in the area as well as with an authoritative tectonic interpretation independent from this study the combined use of tessellation and of our kf model is promising for inverting intensity data sets of preinstrumental earthquakes

block modeling with connected fault network geometries and a linear elastic coupling estimator in spherical coordinates geodetic observations of interseismic deformation provide constraints on the partitioning of fault slip across plate boundary zones the spatial distribution of both elastic and inelastic strain accumulation and the nature of the fault system evolution here we describe linear block theory which decomposes surface velocity fields into four components 1 plate rotations 2 elastic deformation from faults with kinematically consistent slip rates 3 elastic deformation from faults with spatially variable coupling and 4 homogeneous intrablock strain elastic deformation rates are computed for each fault segment in a homogeneous elastic half space using multiple optimal planar cartesian coordinate systems to minimize areal distortion and triangular dislocation elements to accurately represent complex fault system geometry block motions fault slip rates elastic coupling and internal block strain rates are determined simultaneously using a linear estimator with constraints from both geodetically determined velocity fields and geologic fault slip rate estimates we also introduce algorithms for efficiently implementing alternative fault network geometries to quantify parameter sensitivity to nonlinear perturbations in model geometry

a revision of the 1693 eastern sicily earthquake and tsunami the 1693 earthquake was a disastrous event affecting eastern sicily southern italy where it caused over 60 000 victims and total destruction of several villages and towns in the districts of siracusa ragusa and catania the earthquake was followed by a tsunami that struck the ionian coasts of sicily and the messina strait and was probably observed even in the aeolian islands historical documents on sea waves and flooding though not abundant allow us to form a picture of the tsunami first attack and inundation the first water movement all along the sicilian coastline was a strong sea withdrawal followed by a violent sea return and coastal flooding the main purpose of this research is to put constraints on the focal mechanism of this earthquake on the basis of the available documents on the tsunami 1 by simulating tsunami from different possible sources via numerical modeling based on finite element technique and shallow water approximation and 2 by choosing the source best fitting the tsunami data as the most plausible cause for this tsunami the relevance of this study should also be evaluated in light of the circumstance that no certain indication on the earthquake fault can be deduced from the available macroseismic data alone solving the source problem for this event one of the largest occurring in southeastern sicily in historical times is a significant contribution to understanding the seismotectonic regime of the region and to assessing the related earthquake and tsunami hazard risk with implications on mitigation policies

kinematics of the western africa eurasia plate boundary from focal mechanisms and gps data summary the western mediterranean displays a complex pattern of crustal deformation distributed along tectonically active belts developed in the framework of slow oblique plate convergence we used earthquake and global positioning system gps data to study the present day kinematics and tectonics of the africa eurasia plate boundary in this region crustal seismicity and focal mechanisms analysed in terms of seismic moment release and seismic deformation outline the geometry of major seismic belts and characterize their tectonics and kinematics continuous gps data have been analysed to determine euler vectors for the nubian and eurasian plates and to provide the global frame for a new mediterranean gps velocity field obtained by merging continuous and campaign observations collected in the 1991 2005 time span gps velocities and displacements predicted by the nubia eurasia rotation pole provide estimates of the deformation accommodated across the tectonically active belts the rather simple deformation occurring in the atlantic region characterized by extension about perpendicular to the middle atlantic and terceira ridges and right lateral motion along the gloria transform fault turns into a complex pattern of deformation occurring along broader seismic belts where continental lithosphere is involved our analysis reveals a more complex fragmentation of the plate boundary than previously proposed the roughly e w trending mainly compressive segments i e southwestern iberia northern algeria and southern tyrrhenian where plate convergence is largely accomodated across rather localized deformation zones and partially transferred northward to the adjacent domains i e the algero balearic and tyrrhenian basins are interrupted by regions of more distributed deformation i e the rif alboran betics tunisia libya and eastern sicily or limited seismicity i e the strait of sicily which are characterized by less homogeneous tectonics regimes mainly transcurrent to extensional in correspondence of the observed breaks tectonic structures with different orientation interfere and we find belts with only limited deformation i e the high and middle atlas the tunisian atlas and the offshore tunisia libya belt that extends from the plate boundary into the nubian plate along pre existing tectonic lineaments our analysis suggest that the sicilian pelagian domain is moving independently from nubia according to the presence of a right lateral and extensional decoupling zone corresponding to the tunisia libya and strait of sicily deformation zone despite the space variability of active tectonic regimes plate convergence still governs most of the seismotectonic and kinematic setting up to the central aeolian region in general local complexities derive from pre existing structural features inherited from the tectonic evolution of the mediterranean region on the contrary along calabria and the apennines the contribution of the subducted ionian oceanic lithosphere and the occurrence of microplates i e adria appear to substantially modify both tectonics and kinematics finally gps data across the gibraltar arc and the tyrrhenian calabria domain support the hypothesis that slab rollback in these regions is mostly slowed down or stopped

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

statistical tests of additional plate boundaries from plate motion inversions we have investigated the application of the f ratio test a standard statistical technique to the results of relative plate motion inversions the method tests whether the improvement in fit of the model to the data resulting from the addition of another plate to the model is greater than that expected purely by chance this approach appears to be useful in determining whether additional plate boundaries are justified we confirm previous results favoring separate north american and south american plates with a boundary located between 30 n and the equator using chase s global relative motion data we show that in addition to separate west african and somalian plates separate west indian and australian plates with a best fitting boundary between 70 e and 90 e can be resolved these results are generally consistent with the observation that the indian plate s internal deformation extends somewhat westward of the ninetyeast ridge the relative motion pole is similar to minster and jordan s and predicts the nw se compression observed in earthquake mechanisms near the ninetyeast ridge

the ionian and alfeo etna fault zones new segments of an evolving plate boundary in the central mediterranean sea highlights plate boundary re organization in the central mediterranean sea segmentation of the subduction complex along lithospheric transverse faults step faults in the ionian sea pleistocene active faulting and mt etna formation abstract the calabrian arc is a narrow subduction rollback system resulting from africa eurasia plate convergence while crustal shortening is taken up in the accretionary wedge transtensive deformation accounts for margin segmentation along transverse lithospheric faults one of these structures is the nnw sse transtensive fault system connecting the alfeo seamount and the etna volcano alfeo etna fault aef a second nw se crustal discontinuity the ionian fault if separates two lobes of the ca subduction complex western and eastern lobes and impinges on the sicilian coasts south of the messina straits analysis of multichannel seismic reflection profiles shows that 1 the if and the aef are transfer crustal tectonic features bounding a complex deformation zone which produces the downthrown of the western lobe along a set of transtensive fault strands 2 during pleistocene times transtensive faulting reactivated structural boundaries inherited from the mesozoic tethyan domain which acted as thrust faults during the messinian and pliocene 3 the if and the aef and locally the malta escarpment accommodate a recent tectonic event coeval and possibly linked to the mt etna formation regional geodynamic models show that whereas aef and if are neighboring fault systems their individual roles are different faulting primarily resulting from the ese retreat of the ionian slab is expressed in the northwestern part of the if the aef on the other hand is part of the overall dextral shear deformation resulting from differences in africa eurasia motion between the western and eastern sectors of the tyrrhenian margin of northern sicily and accommodating diverging motions in the adjacent compartments which results in rifting processes within the western lobe of the calabrian arc accretionary wedge as such it is primarily associated with africa eurasia relative motion

fast geodetic strain rates in eastern sicily southern italy new insights into block tectonics and seismic potential in the area of the great 1693 earthquake abstract along the 500 km long sicily calabria segment of the nubia eurasia plate boundary gps data highlight a complex and debated kinematic pattern we focus on eastern sicily where the style of crustal deformation rapidly changes in the space of few tens of kilometers in southeastern sicily struck by the 1693 m w 7 4 earthquake gps measurements highlight a steep velocity gradient with 2 4 mm yr of n s shortening in 10 km changing to broader extension 3 mm yr in 60 km in northern sicily and shortening in the southern tyrrhenian sea gps data and kinematic elastic block models highlight a complex fragmentation of the sicilian domain into three tectonic blocks which move independently from nubia describing an overall clockwise rotation of this crustal domain with respect to eurasia shortening in southeastern sicily is associated with a system of high angle reverse faults resulting from tectonic inversion of extensional faults at the northern tip of the hyblean plateau extension in northern sicily occurs on a broader deformation belt developed on the former kumeta alcantara line extending west of mount etna toward the southwestern tyrrhenian sea accommodating the faster rotation of the northeastern sicily block with respect to central sicily although the seismic potential of inland faults is not negligible our results strengthen the hypothesis that the malta escarpment is the likely source of the large 1693 earthquake and tsunami the observed kinematics appears only subordinately driven by the nubia eurasia convergence and the dynamics of the mediterranean subduction system is likely playing a major role in governing block motions and active tectonics in sicily

on the reactivation of extensional fault systems in terranes that have undergone substantial extension three sets of faults dominate a shallow to steep dipping commonly rotational normal faults b a really extensive shallow dipping normal detachment faults and c steep dipping transfer faults that strike at high angles to the normal faults these fault systems may extend through a large fraction of the crust reactivation of these fault systems will depend primarily on the relative strengths of the faults shear zones and their host rock and their orientation in the prevailing stress field it is concluded that reactivation is generally mechanically favoured but that it will probably only take place when the fault shear zones are in near ideal orientations consideration of the tectonic setting of extended terranes and of the limited number of well described examples suggests that reverse thrust reactivation of the normal and detachment faults and wrench reactivation of transfer faults are the most likely styles examples of these styles are described from the bass strait basins of southeastern australia because extended terranes commonly underlie sedimentary basins for example on passive continental margins reactivation of extensional faults may be a key control on the tectonic evolution of such basins i e basin inversion

new empirical relationships among magnitude rupture length rupture width rupture area and surface displacement source parameters for historical earthquakes worldwide are compiled to develop a series of empirical relationships among moment magnitude m surface rupture length subsurface rupture length downdip rupture width rupture area and maximum and average displacement per event the resulting data base is a significant update of previous compilations and includes the additional source parameters of seismic moment moment magnitude subsurface rupture length downdip rupture width and average surface displacement each source parameter is classified as reliable or unreliable based on our evaluation of the accuracy of individual values only the reliable source parameters are used in the final analyses in comparing source parameters we note the following trends 1 generally the length of rupture at the surface is equal to 75 of the subsurface rupture length however the ratio of surface rupture length to subsurface rupture length increases with magnitude 2 the average surface displacement per event is about one half the maximum surface displacement per event and 3 the average subsurface displacement on the fault plane is less than the maximum surface displacement but more than the average surface displacement thus for most earthquakes in this data base slip on the fault plane at seismogenic depths is manifested by similar displacements at the surface log linear regressions between earthquake magnitude and surface rupture length subsurface rupture length and rupture area are especially well correlated showing standard deviations of 0 25 to 0 35 magnitude units most relationships are not statistically different at a 95 significance level as a function of the style of faulting thus we consider the regressions for all slip types to be appropriate for most applications regressions between magnitude and displacement magnitude and rupture width and between displacement and rupture length are less well correlated and have larger standard deviation than regressions between magnitude and length or area the large number of data points in most of these regressions and their statistical stability suggest that they are unlikely to change significantly in response to additional data separating the data according to extensional and compressional tectonic environments neither provides statistically different results nor improves the statistical significance of the regressions regressions for cases in which earthquake magnitude is either the independent or the dependent parameter can be used to estimate maximum earthquake magnitudes both for surface faults and for subsurface seismic sources such as blind faults and to estimate the expected surface displacement along a fault for a given size earthquake

source of the 1693 catania earthquake and tsunami southern italy new evidence from tsunami modeling of a locked subduction fault plane 1 the 1693 catania earthquake which caused 60000 deaths in eastern sicily and generated a 5 10 m high tsunami is investigated gps data indicate ese wnw convergence in the calabrian arc at 4 5 mm yr new high resolution seismic data image active compression at the toe of the accretionary wedge the lack of instrumentally recorded thrust earthquakes suggests the presence of a locked subduction fault plane thermal modeling is applied to calculate the limits of the seismogenic zone tsunami modeling is performed to test the hypothesis that the 1693 earthquake occurred on the subduction fault plane 160 120 km in size with 2 m of mean co seismic slip this source successfully reproduces historical observations with regard to polarity and predicts 1 3 m high amplitudes it is likely that only the sw segment of the subduction fault plane ruptured in 1693 and 1169 implying a recurrence interval of roughly 500 years for similar events

mantle dynamics in the mediterranean the mediterranean offers a unique opportunity to study the driving forces of tectonic deformation within a complex mobile belt lithospheric dynamics are affected by slab rollback and collision of two large slowly moving plates forcing fragments of continental and oceanic lithosphere to interact this paper reviews the rich and growing set of constraints from geological reconstructions geodetic data and crustal and upper mantle heterogeneity imaged by structural seismology we proceed to discuss a conceptual and quantitative framework for the causes of surface deformation exploring existing and newly developed tectonic and numerical geodynamic models we illustrate the role of mantle convection on surface geology a coherent picture emerges which can be outlined by two almost symmetric upper mantle convection cells the downwellings are found in the center of the mediterranean and are associated with the descent of the tyrrhenian and the hellenic slabs during plate convergence these slabs migrated backward with respect to the eurasian upper plate inducing a return flow of the asthenosphere from the backarc regions towards the subduction zones this flow can be found at large distance from the subduction zones and is at present expressed in two upwellings beneath anatolia and eastern iberia this convection system provides an explanation for the general pattern of seismic anisotropy in the mediterranean first order anatolia and adria microplate kinematics and may contribute to the high elevation of scarcely deformed areas such as anatolia and eastern iberia more generally the mediterranean is an illustration of how upper mantle small scale convection leads to intraplate deformation and complex plate boundary reconfiguration at the westernmost terminus of the tethyan collision

insights into present day crustal motion in the central mediterranean area from gps surveys summary in this paper we present observations of crustal motion related to a large gps network located in the central western mediterranean area velocities are obtained by the analysis of more than 30 observing sites at which at least three different gps campaigns were carried out in the time span 1991 1999 the results are presented both in the itrf96 reference frame and with respect to a eurasian fixed reference frame the sites located along the northern african margin in sicily and southern italy show prevalent northeastward movements with a mean velocity of roughly 0 7 cm yr 1 the relatively dense network available in the southern apennines led us to try a tentative estimate of the average strain rate in this zone resulting in a maximum extension of 0 021 0 006 10 6 yr 1 normal to the chain in ionian greece the two sites located south of the kephallinia discontinuity lefkas and kastro ilias consistently indicate a south to southwestward motion at an average rate of roughly 15 mm yr 1

the australian stress map knowledge of the in situ stress field of the australian continent has increased greatly since compilation of the world stress map in 1992 principally by analysis of borehole breakouts and drilling induced tensile fractures in petroleum wells stress orientations are variable across the australian continent as a whole however within 15 of 16 individual stress provinces defined in the australian continent of one to a few hundred kilometres scale mean stress orientations are statistically significant the stress provinces and stress trajectory mapping reveal that there are systematic continental scale rotations of stress orientation within australia unlike many other continental areas stress orientations do not parallel the direction of absolute plate motion nonetheless the regional pattern of stress orientation is consistent with control by plate boundary forces if the complex nature of the convergent northeastern boundary of the indo australian plate and stress focusing by collisional segments of the boundary is recognized

structural and tectono stratigraphic review of the sicilian orogen and new insights from analogue modeling abstract the apennines sicilian maghrebian fold and thrust belt originated from the subduction of the alpine tethys and the later collision of drifted continental blocks against the african and apulian paleomargins from north to south the sicilian fold and thrust belt sftb is divided in four main tectono stratigraphic domains 1 the calabro peloritani terrane drifted from the european margin 2 the remnants of the alpine tethys accretionary wedge atw related to the subduction of the tethys 3 the folded and thrusted platform panormide and deep water imerese sicanian series of the offscrapped african margin and 4 the african foreland hyblean unfortunately scarce quality seismic lines and outcrops of key tectono stratigraphic units make the structure and dynamic evolution of the central eastern part of the sftb controversial first this study outlines through a review of the tectono stratigraphic evolution of the central eastern sector of the sicilian orogen the major remaining issues concerning 1 the occurrence of inferred alpine tethys units far from the region where the remnants of the atw outcrop nebrodi mountains both in a forearc position above the peloritani block to the north and in an active foreland context along the present day southern front of the belt and 2 the diverging tectonic styles from stacked large scale tectonic nappes to foreland imbricated thrust systems rooted into a main basal decollement secondly new constraints are given using analogue modeling to test mechanically the hypothesized structural and tectono stratigraphic evolution of the sftb the experiment simulates the orogenic evolution of the sftb at crustal scale from the oligocene tethys subduction to the middle miocene late pliocene continental collision between the european and african paleomargins the tectono stratigraphic synthesis is used to model the first order mechanical stratigraphy of the sedimentary units involved in the sicilian belt as well as the imprint of the african margin structural inheritance the experiments succeed in reproducing the general structure and tectono stratigraphic evolution of the sftb in particular the models support field observations hypothesing a gravity driven origin of the inferred alpine tethys units intercalated within the forearc and foreland syntectonic sedimentation moreover the model testifies of the main tectonic steps that led to the sftb building first a low tapered accretionary wedge was accreted above the alpine tethys oceanic crust from the oligocene to the early miocene the following underthrusting of the stretched african continental margin and its frontal panormide platform shortened and thickened the accretionary wedge this phase provided favorable conditions for significant pulses of reworked alpine tethys units that intercalated within the forearc and foredeep successions during the middle miocene the decollement of the african meso cenozoic cover panormide platform and imerese sicanian deep water basin enhanced a deep seated deformation phase along with duplexing of the panormide platform beneath the alpine tethys wedge leading to its emersion since the late messinian activation of basement faults led to a generalized emersion of the orogenic units through large wavelength fold culminations accompanied by syn tectonic deposition at their southern limbs concurrently the prism front was partly indented to the southeast by the thick and locally already emerged hyblean platform

regional deformation and offshore crustal local faulting as combined processes to explain uplift through time constrained by investigating differentially uplifted late quaternary palaeoshorelines the foreland hyblean plateau se sicily

site classification for earthquake hazard and risk assessment in australia while site response phenomena are well recognized globally the influence of regolith properties on ground motion has not previously been investigated for much of australia in an effort to characterize the regolith in terms of its ability to modify earthquake ground shaking this validation study assesses the national site classification map of australia which has been developed for application in first order earthquake hazard and risk assessment in the absence of regolith thickness and fundamental period data site classes are assigned based on a method developed in california that uses the relationship between geological material and the shear wave velocity of the upper 30 m v s 30 the classification scheme is then adjusted to suit the australian geological environment including a correction for the presence of weathered in situ regolith commonly encountered in this stable tectonic setting the results are validated using geophysical and geotechnical data from a variety of quaternary sedimentary environments in the newcastle sydney and perth urban areas and from bedrock dominated environments at a range of sites across australia the results of these analyses demonstrate the utility but also highlight the limitations of applying a depth limited shear wave velocity method in site classification for seismic hazard assessment

new structural and seismological evidence and interpretation of a lithospheric scale shear zone at the southern edge of the ionian subduction system central eastern sicily italy we performed an integrative analysis of geological gravimetric and seismological data analyzed data depicted a not well known wrench zone in the central eastern sicily our findings enabled us to interpret this shear zone as a plio pleistocene step fault

high vp vs ratio saturated cracks or anisotropy effects 1 we measured vp vs ratios of thermally cracked westerly granite thermally cracked carrara marble and 4 porosity fontainebleau sandstone for an effective mean pressure ranging from 2 to 95 mpa samples were fluidsaturated alternatively with argon gas and water 5 mpa constant pore pressure the experimental results show that at ultrasonic frequencies vp vs ratio of water saturated specimen never exceeded 2 15 even at effective mean pressure as low as 2 mpa or for a lithology for which the poisson s ratio of minerals is as high as 0 3 calcite in order to check these results against theoretical models we examine first a randomly oriented cracked medium with dispersion but without anisotropy and second a medium with horizontally aligned cracks with anisotropy but without dispersion the numerical results show that experimental data agree well with the first model at high frequency vp vs ratios range from 1 6 to 1 8 in the dry case and from 1 6 to 2 2 in the saturated case the second model predicts both vp sv and vp sh to vary from 1 2 to 3 5 depending on the raypath angle relative to the crack fabric in addition perpendicular to the crack fabric a high vp vs ratio is predicted in the absence of shear wave splitting from these results we argue the possibility that high vp vs ratio 2 2 as recently imaged by seismic tomography in subduction zones may come from zones presenting important crack anisotropy the cumulative effects of crack anisotropy and high pore fluid pressure are required to get vp vs ratios above 2 2 citation wang x q a schubnel j fortin e c david y gueguen and h k ge 2012 high vp vs ratio saturated cracks or anisotropy effects geophys res lett 39 l11307 doi 10 1029 2012gl051742

crustal structure and seismotectonics of central sicily southern italy new constraints from instrumental seismicity summary in this paper we propose a new model of the crustal structure and seismotectonics for central sicily southern italy through the analysis of the depth distribution and kinematics of the instrumental seismicity occurring during the period from 1983 to 2010 and its comparison with individual geological structures that may be active in the area the analysed data set consists of 392 earthquakes with local magnitudes ranging from 1 0 to 4 7 we defined a new detailed 1 d velocity model to relocate the earthquakes that occurred in central sicily and we calculated a moho depth of 37 km and a mean vp vs ratio of 1 73 the relocated seismic events are clustered mainly in the area north of caltanissetta e g mainland sicily and in the northeastern sector madonie mountains of the study area only minor and greatly dispersed seismicity is located in the western sector near belice and along the southern coast between gela and sciacca the relocated hypocentral distribution depicts a bimodal pattern 50 per cent of the events occur within the upper crust at depths less than 16 km 40 per cent of the events occur within the middle and depth crust at depths between 16 and 32 km and the remaining 10 per cent occur at subcrustal depths the energy release pattern shows a similar depth distribution on the basis of the kinematic analysis of 38 newly computed focal plane solutions two major geographically distinct seismotectonic domains are distinguished the madonie mountain domain with prevalent extensional and extensional oblique kinematics associated with upper crust late pliocene quaternary faulting and the mainland sicily domain with prevalent compressional and compressional oblique kinematics associated with thrust faulting at mid to deep crust depth along the north dipping sicilian basal thrust sbt the stress inversion of the mainland sicily focal solutions integrated with neighbouring mechanisms available in the literature highlights a regional homogeneous compressional tensor with a subhorizontal nnw sse striking 1 axis in addition on the basis of geodetic data the mainland sicily domain may be attributed to the sse ward thrusting of the mainland sicily block along the sbt plane seismogenic shearing along the sbt at mid crustal depths was responsible for the unexpected belice 1968 earthquake mw 6 1 with evident implications in terms of hazard assessment

vertical gps ground motion rates in the euro mediterranean region new evidence of velocity gradients at different spatial scales along the nubia eurasia plate boundary we use 2 5 to 14 years long position time series from 800 continuous global positioning system gps stations to study vertical deformation rates in the euro mediterranean region we estimate and remove common mode errors in position time series using a principal component analysis obtaining a significant gain in the signal to noise ratio of the displacements data following the results of a maximum likelihood estimation analysis which gives a mean spectral index 0 7 we adopt a power law white noise stochastic model in estimating the final vertical rates and find 95 of the velocities within 2 mm yr with uncertainties from filtered time series 40 smaller than from the unfiltered ones we highlight the presence of statistically significant velocity gradients where the stations density is higher we find undulations of the vertical velocity field at different spatial scales both in tectonically active regions like eastern alps apennines and eastern mediterranean and in regions characterized by a low or negligible tectonic activity like central iberia and western alps a correlation between smooth vertical velocities and topographic features is apparent in many sectors of the study area glacial isostatic adjustment and weathering processes do not completely explain the measured rates and a combination of active tectonics and deep seated geodynamic processes must be invoked excluding areas where localized processes are likely or where subduction processes may be active mantle dynamics is the most likely process but regional mantle modeling is required for a better understanding

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

stress directions and shear wave anisotropy observations from local earthquakes in southeastern sicily italy the spatial distribution of 414 earthquakes 1 0 m l 4 6 recorded from 1994 to 2002 in southeastern sicily italy has been analyzed the seismicity generally coincides with mapped plio quaternary faults including the north north west south southeast striking offshore fault system which is the most important tectonic structure of the area for the best located events we computed 70 focal mechanisms by combining p wave polarities with s wave polarizations a predom inance of strike slip and normal faults was observed focal mechanisms were then inverted for stress tensor parameters by using the algorithm of gephart and forsyth the results highlighted a region governed mainly by a north northwest south south east to northwest southeast compressional stress regime moreover anisotropy anal ysis of shear waves showed a polarization of fast s waves coherently aligned with this stress direction a finer scale analysis of the stress tensor evidenced three regions characterized by slightly differing orientation of the greatest principal stress axis r1 the eastern sector displays a nearly horizontal r1 trending northwest southeast the central sector is affected by a low dip north northwest south southeast r1 whereas in the western sector a north northwest south southeast oriented r1 with a higher dip angle was detected finally the comparison of the spatial distribution of seismicity occurring during 1994 2002 with locations of previous instrumental earthquakes and larger m 5 0 historical events showed that the seismicity patterns are persistent

strain accumulation across the messina straits and kinematics of sicily and calabria from gps data and dislocation modeling article i nfo we use global positioning system gps velocities and dislocation modeling to investigate the rate and nature of interseismic strain accumulation in the area affected by the 1908 mw 7 1 messina earthquake southern italy within the framework of the complex central mediterranean microplate kinematics our data confirm a change in the velocity trends between sicily and calabria moving from nnw ward to ne ward with respect to eurasia and detail a fan like pattern across the messina straits where maximum extensional strain rates are 65 nanostrains yr extension normal to the coast of northern sicily is consistent with the presence of sw ne trending normal faults half space dislocation models of the gps velocities are used to infer the slip rates and geometric fault parameters of the fault zone that ruptured in the messina earthquake the inversion and the bootstrap analysis of model uncertainties finds optimal values of 3 5 2 0 1 3

gps velocity and strain fields in sicily and southern calabria italy updated geodetic constraints on tectonic block interaction in the central mediterranean 1 we present an improved rendition of the geodetic velocity and strain fields in sicily and southern calabria obtained through the analysis of 18 years of gps observations from continuous and survey station networks the dense spatial coverage of geodetic data provides precise quantitative estimates of previously established first order active kinematic features including i a narrow east west elongated belt of contraction 1 1 5 mm yr extending offshore northern sicily from ustica to stromboli across the aeolian islands ii a narrow east west trending contractional belt located along the northern rim of the hyblean plateau in southern sicily with shortening at up to 4 4 mm yr iii right motion 3 6 mm yr on the aeolian tindari letojanni fault atlf system a main shear zone extending from the aeolian islands to the ionian coast of sicily with significant transpression and transtension partitioned between discrete sectors of the fault iv transtension 1 mm yr across the sicily channel between sicily and north africa we use geodetic observations coupled to geological constraints to better elucidate the interplay of crustal blocks revealed in the investigated area in particular we focus on the atlf which forms the primary boundary between the sicilian and calabrian blocks the atlf juxtaposes north south contraction between sicily and the tyrrhenian block with northwest southeast extension in northeastern sicily and calabria contraction between sicily and tyrrhenian blocks probably arises from the main europe nubia convergence although sicily has a component of lateral motion away from nubia we found that convergence is not restricted to the northern offshore as commonly believed but is widely accommodated between the frontal belt and the northern rim of the hyblean foreland in southern sicily geodetic data also indicate that active right shear on the atlf occurs to the southeast of the mapped fault array in northern sicily suggesting the fault cuts through till the ionian coast of the island the small geodetic divergence between the hyblean and apulian blocks rimming on both sides the calabria block and subjacent ionian slab coupled with marine geophysical evidences in the ionian sea lends credit to the proposed deep root of the atlf and to a fragmentation of the ionian domain

segmentation of the farallon slab abstract recent tomography images reveal a complex 3d mantle structure beneath western united states with feature morphology varying rapidly with depth by assimilating plate motion history paleo age of sea floor and paleo geography of plate boundaries in a 3 d numerical model we simulate the farallon juan de fuca subduction during the past 40 ma we find that the highly segmented upper mantle structure of western u s is a direct result of the farallon subduction we show that the tilted horseshoe shaped fast seismic anomaly beneath nevada and utah at 300 600 km depth range is in fact a segment of curled slab subducted since 15 ma and the shallower linear slab beneath the cascades is younger than 5 ma the distinct morphology between these two parts of the subduction system indicates the strong influence of the fast trench rollback since 20 ma the northward migrating jf pa na triple junction and the toroidal flow around slab edges the observed mantle structures are used to constrain the rheology of the upper mantle through matching the shape depth and location of modeled subducted slab segments the inferred viscosity for the asthenosphere is 5 10 19 pa s and those for the transition zone and lower mantle are 1 5 10 21 pa s and 2 10 22 pa s respectively the slab is found to be about 2 orders of magnitude stronger than the ambient mantle above 410 km depth but of similar order of magnitude viscosity in the transition zone

the seismic sequence of january february 2014 at cephalonia island greece constraints from sar interferometry and gps this article has been accepted for publication in geophysical journal internationa 2015 published by oxford university press on behalf of the royal astronomical society all rights reserved

feasibility analysis for time lapse seafloor gravity monitoring of producing gas fields in the northern carnarvon basin offshore australia abstracthighly accurate seafloor gravity data can detect small density changes in subsurface hydrocarbon reservoirs by precisely repositioning the gravimeters on the seafloor in producing gas fields these small density changes are primarily caused by production related changes to the pressure and gas fluid saturations in the reservoir pore space knowledge of the pressure and saturation changes is vital to optimize the gas recovery especially in offshore environments in which wells are expensive and sparse we assessed the feasibility of time lapse seafloor gravity monitoring for the giant gas fields in australia s premier hydrocarbon province the northern carnarvon basin we determined that gravity monitoring is more feasible for reservoirs with a large areal extent and or shallow burial depths with high porosities and high net to gross sand ratios forward modeling of the gravity responses using simple equivalent geometry shapes and full 3d complex heterogeneous models predicted that density change

active fault kinematics and crustal stresses along the ionian margin of southeastern sicily since the late cretaceous onset of plate convergence between africa and europe the malta escarpment has been converted from a mesozoic passive margin into a mega hinge fault system with an additional sinistral strike slip component the modern tectonic stress regime with nw se directed maximum horizontal stresses has been established since late messinian times since the pleistocene sinistral strike slip deformation and contemporaneous normal faulting along the malta escarpment have induced the opening of oblique trending onshore grabens at the eastern margin of the hyblean plateau in this study we focus on the kinematics the controlling state of stress and the temporal variation of the neotectonic to active strike slip and normal fault structures the stress tensor calculations reveals that the widespread map scaled to meso scaled normal fault structures are governed by the long term extensional state of stress during the quaternary this long term stress tensor is predominantly controlled by gravitational induced stresses due to vertical load 1 sv and lateral extension due to the topographic gradient of the malta escarpment 3 sh ne sw in this case the average tectonic stresses 2 sh nw se transmitted by the regional to plate tectonic stress field are significantly smaller than the gravitational induced stresses in contrast the clear localization of conjugate sets of meso scaled strike slip fault structures and shear zones without accompanying normal fault structures give strong indications for episodic seismotectonic strike slip faulting under critical stress conditions in this state tectonically induced maximum horizontal stresses are successively increased by ongoing plate convergence from low level stress magnitudes 1 sv 2 sh nw se up to critical stress magnitudes 1 sh nw se 2 sv which are significantly larger than gravitational stresses at the critical state seismotectonic stress release occurs by active strike slip faulting as recently indicated in mid crustal levels by the moderate 1990 augusta earthquake and re establishes the long term extensional state of stress because the strike slip faults and shear zones in the study area were formed as surface ruptures they additionally give indications of episodic large earthquakes in this region with magnitudes greater than 6 0 as reported by several large earthquakes devastating e and se sicily in historical times

etnean and hyblean volcanism shifted away from the malta escarpment by crustal stresses abstract a fraction of the volcanic activity occurs intraplate challenging our models of melting and magma transfer to the earth s surface a prominent example is mt etna eastern sicily offset from the asthenospheric tear below the malta escarpment proposed as its melt source the nearby hyblean volcanism to the south and the overall northward migration of the eastern sicilian volcanism are also unexplained here we simulate crustal magma pathways beneath eastern sicily accounting for regional stresses and decompression due to the increase in the depth of the malta escarpment we find non vertical magma pathways with the competition of tectonic and loading stresses controlling the trajectories curvature and its change in time causing the observed migration of volcanism this suggests that the hyblean and etnean volcanism have been fed laterally from a melt pooling region below the malta escarpment the case of eastern sicily shows how the reconstruction of the evolution of magmatic provinces may require not only an assessment of the paleostresses but also of the contribution of surface loads and their variations at times the latter may even prevail accounting for these competing stresses may help shed light on the distribution and wandering of intraplate volcanism

gravimetric monitoring of gas production from the troll field four surveys of relative gravity and depth measurements have been conducted over the troll field since gas production began in 1996 precision in gravity intrasurvey repeatability measured as standard deviation has improved from 26 gal to 4 5 gal in two surveys in 2002 and 2005 the scatter of 74 station depth differences standard deviation has improved to 1 0 cm with modeled subsidence removed for the same two surveys subsidence of up to 3 cm is observed above the thickest reservoir of troll east between 2002 and 2005 time lapse gravity shows a general slight average increase in troll east 95 confidence for the interval centered at 5 2 4 4 gal which is likely caused by edgewater influx one gravity station close to troll a shows a 9 gal gravity increase indicating 2 2 m water rise repeated logging in a nearby well indicates 2 8 m rise these two observations agree within uncertainty bounds gravity decrease in troll west is explained by oil production and a downward moving gas oil con

crustal velocity field of western europe from permanent gps array solutions 1996 2001 we derive a new geodetic velocity field for western europe and the western mediterranean by rigorously combining 1 a selection of 36 itrf2000 sites 2 a solution from a subset of sites of the european permanent gps network euref epn 3 a solution of the french national geodetic permanent gps network rgp and 4 a solution of a permanent gps network in the western alps regal the resulting velocity field describes horizontal crustal motion at 64 sites in western europe with an accuracy of the order of i mm yr 1 or better its analysis shows that central europe defined as east of the rhine graben and north of the alps and the carpathians behaves rigidly at a 0 4 mm yr 1 level and defines a stable europe reference frame in that reference frame we find no significant motion at sites located west of the rhine graben and on the iberian peninsula which sets an upper bound of 0 6 mm yr 1 on horizontal motion across the rhine graben and the pyrenees we find that the current strain pattern in the western alps combines e w extension and right lateral shear we confirm a counterclockwise rotation of the adriatic microplate which appears to control the strain pattern along its boundaries in the friuli area the alps and the apennines our results also suggest that the africa eurasia plate motion in the western mediterranean may be 40 50 per cent slower that the nuvel1a plate motion model and rotated 20 30 counterclockwise

malta escarpment fault zone offshore eastern sicily pliocene quaternary tectonic evolution based on new multichannel seismic data 1 the malta escarpment represents the dominant morphological feature offshore eastern sicily linking the deep ionian basin to the east with the hyblean carbonate platform to the west interpretation of purposely acquired multichannel seismic data allows division of the malta escarpment into two portions characterized by different tectonic structures along the segment south of siracusa the malta escarpment is not affected by recent faulting and appears as a steep surface that flattens out toward the ionian basin a recent deformation characterized by a broad area of uplift occurs 20 30 km east from the slope along a nnw sse trend the segment of the malta escarpment extending north of siracusa on the other hand is characterized by the presence of nnw sse east dipping recent extensional faults and related sedimentary basins the observed structural features support the occurrence of a lithospheric tear between the ionian oceanic basin and the hyblean plateau

gravity changes and natural gas extraction in groningen gravity observations made over the groningen gasfield from 1978 onwards are available the existing gravity data were reanalysed and a new survey was carried out the observed gravity changes obtained during four surveys spanning an 18 year period were compared with the gravity effect due to natural gas extraction computed from the reservoir model and the production data the random error in the gravity values is small enough to detect the effect of gas extraction after a few years up to 2 gal year the trends obtained from observed and calculated gravity changes agree well within their expected error margins after statistical data snooping due to the inadequate measurement set up of the previous surveys systematic errors present in the gravity data hampered the use of this data for refinement of the reservoir and the production models however with improved gravity monitoring in particular a very systematic network set up and well calibrated instruments this should now be feasible by using the network analysis from the 1996 measurements for the planning of a network in space and time most of the current problems can be avoided

crustal velocity and strain rate fields in italy and surrounding regions new results from the analysis of permanent and non permanent gps networks summary we present a new geodetic velocity solution for italy and the surrounding areas obtained from an analysis of continuous and survey mode global positioning system observations collected between 1991 and 2002 we have combined local regional and global networks into a common reference frame velocity solution providing a new detailed picture of the regional scale deformation field in the central mediterranean our velocity estimates are computed with respect to a new stable eurasian reference frame constraining the kinematics of the greater african eurasian plate boundary system in the study area we provide strain rate values for the main seismotectonic districts which are in good agreement with the seismic deformation inferred from earthquake focal mechanisms the southern tyrrhenian area calabria the apennines the southeastern alps the southern dinarides and the albanides display deformation rates at the order of 20 30 nanostrain yr 1 the corsica sardinia block moves according to eurasian plate motions and there is no indication that the opening of the tyrrhenian is still active the pelagian and sicilian domains are separated by a northwest southeast discontinuity the sicily channel rifted area and marginally significant relative motion between the pelagian plateau and the african plate is also observed the southern tyrrhenian is affected by north south compression and accommodates up to 50 per cent of the africa eurasia relative plate motion whereas the calabrian arc exhibits 2 mm yr 1 northwest southeast extension the observed deformation pattern suggests the presence of a major approximately north south tectonic discontinuity separating the sicilian and calabrian domains an extensional boundary observed along peninsular italy coincides with the distribution of seismogenic faults along the axis of the apennines this boundary separates a tyrrhenian and an adriatic domain with diverging velocities orientated north nnw ward and northeastward respectively the apennines are extending perpendicularly to the chain axis at rates of less than 3 mm yr 1 and only in the outer northern apennines indications of active shortening are observed insignificant deformation is observed in the western po plain and the western alps while the central and eastern alps display north south shortening the eastern adriatic domain is shortening perpendicular to the dinaric front with strain rates increasing from north to south the locus of collision between the aegean balkan system and the adriatic and ionian domains is marked by the kephalonia fault system which accommodates up to 20 1 mm yr 1 of right lateral motion the deformation pattern observed in the peri adriatic domain is well described by a counter clockwise rotation of the adriatic microplate around a pole located in the western alps

geodynamic models of deep subduction abstract numerical and laboratory models that highlight the mechanisms leading to a complex morphology of subducted lithospheric slabs in the mantle transition zone are reviewed an increase of intrinsic density with depth an increase of viscosity or phase transitions with negative clapeyron slope have an inhibiting influence on deep subduction the impingement of slabs on a viscosity and density interface has been studied in laboratory tanks using corn syrup slab interaction with equilibrium and non equilibrium phase transitions has been modelled numerically in two dimensions both the laboratory and the numerical experiments can reproduce the variety of slab behaviour that is found in tomographic images of subduction zones including cases of straight penetration into the lower mantle flattening at the 660 km discontinuity folding and thickening of slabs and sinking of slabs into the lower mantle at the endpoint of a flat lying segment aside from the material and phase transition properties the tectonic conditions play an important role in particular the retrograde motion of the point of subduction trench rollback has an influence on slab penetration into the lower mantle a question that still needs to be clarified is the mutual interaction between plate kinematics and the subduction process through the transition zone

the database of individual seismogenic sources diss version 3 summarizing 20 years of research on italy s earthquake geology abstract this paper describes the main characteristics the evolution and the structure of the database of individual seismogenic sources diss and particularly of its release of early 2007 the database contains the results of the investigations of the active tectonics in italy during the past 20 years the first two sections of this paper document the recent evolution in mapping and archiving italian active fault data in relation to important achievements in the understanding of italian tectonics some of which were spurred by significant earthquakes the central sections describe the current structure of the database the reasons for its assumptions and data categories its current contents its evolution through several years of improvements the last section describes how the current contents of the database correspond with the existing strain and stress data available from focal mechanism borehole breakout and gps data for the whole of italy the database supplies a fresh and unified view of active and seismogenic processes in italy by building on basic physical constraints concerning rates of crustal deformation on the continuity of deformation belts and on the spatial relationships between adjacent faults both at the surface and at depth

spatial variation of present day stress field and tectonic regime in tunisia and surroundings from formal inversion of focal mechanisms geodynamic implications for central mediterranean we compiled 123 focal mechanisms from various sources for tunisia and adjacent regions up to sicily to image the current stress field in the maghrebides chain from tunisia to sicily and its foreland stress inversion of all the available data provides a first order stress field with a n150 e horizontal compression shmax and a transpressional tectonic regime but the obtained stress tensor poorly fit to the data set we separated them into regional subsets boxes in function of their geographical proximity kinematic regime homogeneity of kinematic orientations and tectonic setting their respective inversion evidences second and third order spatial variations in tectonic regime and horizontal stress directions the stress field gradually changes from compression in the maghrebides thrust belt to transpression and strike slip in the atlassic and pelagian foreland respectively where preexisting nw se to e w deep faults system are reactivated this spatial variation of the sismotectonic stress field and tectonic regime is consistent with the neotectonic stress field determined by others from fault slip data the major slab transfer edge propagator faults i e north south axis hammamet relay and malte escarpment which laterally delimit the subducting slabs play an active role in second and third order lateral variations of the tectonic regime and stress field orientations over the tunisian sicilian domain the past and current tectonic deformations and kinematics of the central mediterranean are subordinately guided by the plate convergence i e africa eurasia controlled or influenced by lateral slab migration segmentation and by deep dynamics such as lithosphere mantle interaction

incipient extension along the active convergent margin of nubia in sicily italy cefalu etna seismic zone 1 recent geodetic data are compatible with nne ssw tectonic extension at a rate of 5 mm yr in sicily southern italy within a broader region of net active compression along the nubian plate margin northern africa the structures that accommodate such extensional regime and its cause are still unknown from field structural surveys and seismological analyses the geometry kinematics structural architecture and seismic potential of an extensional seismic zone linking cefalu and mount etna in central eastern sicily are defined the zone includes high angle wnw striking normal and right lateral strike slip faults and subordinate north and nne striking strike slip faults either right or left lateral the occurrence of small discontinuous faults and the absence of related depressions and sedimentary basins suggest that the extensional regime is still in an incipient stage the ongoing seismic activity possibly reactivates preexisting faults instrumentally and historically recorded earthquakes are lower than about 6 in magnitude and destructive events are historically unknown since at least 1300 a d this apparent upper bound of earthquake magnitudes is consistent with the maximum magnitude values estimated from the length of the longest mapped faults and sources of seismic swarms which all together suggest a value between 6 and 6 5 as the maximum expected magnitude that can be proposed at the present stage of investigation for earthquakes in the study area lateral extension on preexisting faults and upwelling of melt mantle material beneath mount etna are considered viable processes to explain at least in part the active extensional tectonics along the cefalu etna seismic zone strike slip seismic faulting beneath mount etna may be part of a previously proposed diffuse transfer zone affecting northeastern sicily and including the tindari fault

deep origin of the dome shaped hyblean plateau southeastern sicily a new tectono magmatic model southeastern sicily is characterized by a prominent topography known as the hyblean plateau it is commonly considered as a flexural bulge formed by the northwest plunging of the hyblean malta platform beneath the sicilian fold and thrust belt however its noncylindrical shape and multiphase uplift history correlated to the late miocene and plio pleistocene volcanism outline a possible magmatic control on the hyblean plateau topographic expression we argue using 2 d flexural models that the flexural bending alone is unlikely to explain the high anomalous elevation of the hyblean plateau moreover topographic analysis show that the hyblean plateau has a dome shape composed of radially tilted preserved surfaces defining individual blocks the block edges seem to be related to deep seated inherited faults using an analogue modeling approach we show that magmatic intrusions beneath the thick meso cenozoic sedimentary cover can reproduce the first order morphology of the hyblean plateau when a structural inheritance is imposed accordingly we propose a tectono magmatic model that favors mafic sill intrusions as the major uplift source for the topographic anomaly however to explain the strong positive bouguer anomaly a deeper high density intracrustal body is needed moho uprising related to mesozoic rifting or mafic lower crust underplating intraplating since the late cretaceous can be evoked the small wavelength of the topography and the deep intracrustal mass anomaly makes the lithospheric elastic stresses sufficiently high to maintain a nonisostatic state over the geological time scales

spatial variations of seismogenic stress orientations in sicily south italy abstract seismogenic stress orientations are estimated in the lithosphere of sicily by inversion of 131 local earthquake focal mechanisms fms selected from the literature an average misfit f 14 5 between stress tensor and fms indicates that the entire set of earthquakes is generated by a highly heterogeneous stress field detailed analysis of stress tensors and related earthquake misfits obtained for tens of subsets based on spatial separation of data allowed us to identify two main stress domains in the study region i a compressional domain including etna western sicily and the southern tyrrhenian sea offshore sicily where the 1 orientation roughly changes from nw se in the etna area and western sicily to nne ssw at the northeastern edge of the domain eolian islands and ii an extensional domain in northeastern sicily between the eolian islands and etna where 3 is oriented analogously to previously estimated in the easterly confining extensional area of the messina straits general agreement is found between this stress pattern and the gps crustal displacement vectors reported in the most recent literature for the study region moreover stress inversion enables us to locate the extensional domain more accurately than the presently available gps data finally the stress orientations estimated in the southern and western sectors of the study area etna and western sicily on and offshore match well with the displacement fields predicted for sicily by large scale models of plate motion conversely a mismatch is observed in the northeastern sector eolian islands and northeastern sicily we suggest that the joint action of africa eurasia convergence and ionian subduction trench retreat rollback of the subducting slab may explain the stress pattern detected in sicily in the present study work for computation of a finite element regional geodynamic model based on geophysical and geological data collected over the last few years has recently started with the purpose of quantitatively checking this hypothesis

one hundred years of earthquake recording in australia abstract a comprehensive new catalog of australian earthquakes has been compiled and used to review the seismicity of australia the catalog contains 27 000 events of which 17 000 are considered to be mainshocks the catalog is complete for all australian events with a magnitude greater than m l 5 5 since 1910 m l 5 since 1960 m l 4 since 1970 and m l 3 5 since 1980 it is complete for events in southern australia above m l 3 5 since 1965 and m l 2 since 1980 before the development of local magnitude scales for australia around 1990 the richter magnitude scale was generally used at 600 km a typical hypocentral distance for much of australia the richter formula overestimates magnitude by around 0 5 units thus the results in the catalogs before and after the early 1990s are potentially discrepant most well located australian earthquakes are in the southern areas of the continent where the seismometer density is greatest in general the location uncertainty of australian earthquakes is high only 60 of events are located with an uncertainty of 10 km or less this percentage is smaller for earthquakes before 1980 and before 1960 very few events were located to within 10 km the hypocentral depths of australian earthquakes range mostly between 8 and 18 km except for the southwest corner of the continent where they are typically shallower than 5 km the seismicity in some areas of australia has been steady for at least 100 yr including the southeast corner the flinders ranges and the northwest corner in contrast seismicity in the southwest corner jumped by at least a factor of 6 in the 1940s and has been steady since then much of the rest of australia is characterized by episodic seismicity these episodes begin with a period of high activity lasting 1 10 yr and they are normally associated with a large m 6 earthquake following the large earthquake there is often a period of moderate activity lasting from a few years to several decades before and after each episode is a quiescent period of low activity lasting 0 1 10 ka during which the seismicity is more than an order of magnitude lower than during the period of high activity frequency magnitude relations were calculated using events since 1970 from the new catalog gutenberg richter a and b values were calculated on an 85 km grid and maps of the probability of an earthquake of m 4 9 occurring per year were derived these results are very similar to the global seismic hazard assessment program gshap map for australia the results were used to define four large 20 000 km 2 seismogenic zones fig 1 there are also several other small zones some of which appear to reflect recent episodes while others appear to be long lived the expected number of earthquakes m 5 and m 6 strain rate and deformation rate is given for the four large zones the remainder of australia and the whole australian continent the combined estimates of strain using seismic global positioning system gps and satellite laser ranging slr data suggest east west compressive deformation across southern australia of 0 65 2 0 mm per year likely to be in the 0 5 1 0 mm per year range

large scale ground deformation of etna observed by gps between 1994 and 2001 we have processed thirty global positioning system gps campaigns carried out at etna from 1994 to early 2001 between the last two main flank eruptions of the mt etna sicily italy this rest period allowed us to investigate the deep magma plumbing system of the mt etna the temporal dynamics of twenty three points observed three times or more were analyzed all the time series show a first order linear trend during the five years period it suggests that the volcano was continuously deformed by the action of a deep source while a discrete activity of the volcano was observed at the summit we have interpreted the residual deformation field as the result of an major eastward motion of the eastern flank of the volcano

determination of seismogenic structures in southeastern sicily italy by high precision relative relocation of microearthquakes abstract in december 1990 southeastern sicily was struck by a moderate earthquake m l 5 4 the event and the subsequent aftershocks represent renewed activity for the malta escarpment fault system mefs three centuries after the most recent of several large destructive historical earthquakes an 11 yr period of quiescence was interrupted with a minor swarm in 2002 m max 3 6 these sequences and regional seismicity were relocated through 3d tomography the resulting velocity model indicates a velocity contrast in the vicinity of mefs high precision relative relocations were derived by the cross spectral method for 18 events from the 1990 sequence and 10 earthquakes from the 2002 swarm these swarms were aligned along fault segments striking east northeast west southwest conjugate to the north northwest south southeast orientation of the mefs we conclude that the mefs is fragmented in segments with different seismic behaviors and that great stress accumulation along the main segment of the mefs is less likely

lithosphere tearing at step faults response to edges of subduction zones abstract slab edges are a relatively common feature in plate tectonics two prominent examples are the northern end of the tonga subduction zone and the southern end of the new hebrides subduction zone near such horizontal terminations of subduction trenches ongoing tearing of oceanic lithosphere is a geometric consequence we refer to such kinks in the plate boundary as a subduction transform edge propagator or step other steps are the north and south ends of the lesser antilles trench the north end of the south sandwich trench the south end of the vrancea trench and both ends of the calabria trench volcanism near steps is distinct from typical arc volcanism in some cases slab edges appear to coincide with mantle plumes using 3d mechanical models we establish that step faults are stable plate tectonic features in most circumstances in the probably rare cases that the resistance to fault propagation is high slab break off will occur relative motion along the transform segment of the plate boundary often is non uniform and the step is not a transform plate boundary in the rigid plate tectonics sense of the phrase step propagation may result in substantial deformation rotation topography and sedimentary basins with a very specific time space evolution surface velocities are substantially affected by nearby steps

evolution of the southern tyrrhenian slab tear and active tectonics along the western edge of the tyrrhenian subducted slab abstract the evolution of the southern tyrrhenian subduction has been possibly controlled by distinct episodes of slab break off as indicated by a critical review of the geological literature and by the analysis of purposely acquired multichannel seismic profiles within the proposed interpretation the first episode occurred from 8 5 to 4 0 ma and affected the segment of the slab located in the sardinia channel causing the abandonment of the adventure thrust front in western sicily the second episode occurred between 2 5 and 1 6 ma affecting the segment of slab located north of sicily and was preceeded by rifting in the strait of sicily the space and time location of these episodes appear controlled by discontinuities pre existing within the subducted african plate that trend at high angle to the advancing subduction front these discontinuities delimit segment of subducted slab that can be affected by slab break off and can act as wayouts for magma and mantle derived he the major of these discontinuities the malta escarpment has been reactivated in the quaternary as a trench perpendicular tear step faults ultimately the hierarchy in strength of these trench perpendicular features could have affected the timing and amount of trench retreat and backarc opening

seismogenic stress field estimation in the calabrian arc region south italy from a bayesian approach a new high quality waveform inversion focal mechanism database of the calabrian arc region has been compiled by integrating 292 mechanisms selected from literature and catalogs with 146 newly computed solutions the new database has then been used for computation of posterior density distributions of stress tensor components by a bayesian method never applied in south italy before the present study the application of this method to the enhanced database has allowed us to provide a detailed picture of seismotectonic stress regimes in this very complex area where lithospheric unit configuration and geodynamic engines are still strongly debated our results well constrain the extensional domain of calabrian arc and the compressional one of the southernmost tyrrhenian sea in addition previously undetected transcurrent regimes have been identified in the ionian offshore the new information released here will furnish useful tools and constraints for future geodynamic investigations

coupled hydrogeophysical inversion using time lapse magnetic resonance sounding and time lapse gravity data for hydraulic aquifer testing will it work in practice 1 temporal changes in water content can be directly related to the time lapse signals retrieved using magnetic resonance sounding tl mrs and relative gravimetry tl rg previous studies suggest that tl rg measurements can potentially provide accurate estimates of aquifer characteristics in an aquifer pumping test experiment when used in a coupled hydrogeophysical inversion approach however these studies considered highly idealized conditions the aim of this paper is twofold first we investigate three major issues which likely limit the practical utility of tl rg for pumping test monitoring partially penetrating pumping wells in anisotropic aquifers delayed drainage effects and typical data errors for tl rg second we introduce tl mrs in a similar coupled hydrogeophysical inversion framework and compare the performance of tl mrs and tl rg for pumping test monitoring for this purpose we consider a virtual pumping test for which we generate synthetic drawdown tl mrs and tl rg observations and subsequently determine the aquifer parameters in an inverse parameter estimation approach the inclusion of tl rg and tl mrs data did slightly improve parameter estimates for the specific yield and hydraulic conductivity when considering a fully penetrating well and minimal data error using more conservative tl rg and tl mrs data error estimates according our own field experience strongly limited the informative value of the tl rg data tl mrs data was less affected by this for a partially penetrating well under anisotropic conditions parameter uncertainty could be reduced more effectively compared to a fully penetrating well delayed drainage effects did not limit the ability of the tl mrs and tl rg data to reduce parameter uncertainty significantly the incorporation of representative measurement error correlation in the tl rg data did not affect its informative value a local sensitivity analysis showed that observations were most sensitive to the pumping rate and the thickness specific yield and hydraulic conductivity of the aquifer the inclusion of tl mrs data proved to be more effective to constrain the aquifer parameters compared with tl rg the inclusion of both tl rg and tl mrs had limited added value compared to tl mrs only we conclude that this particular application of coupled hydrogeophysical inversion has limited potential for tl rg while tl mrs appears to be a more promising method

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

convergence vs retreat in southern tyrrhenian sea insights from kinematics 1 the tyrrhenian sea is an extensional basin opened by trench retreat and back arc extension during subduction of the calabrian slab in the last 10 12 my subduction is still active beneath the semost part of the tyrrhenian sea as testified by seismicity down to 500 km depth by analyzing seismicity and geodetic data together with recent tomographic images we define the present day situation an evident n s compressional regime prevails in the tyrrhenian region west of the aeolian archipelago while east of them a nnw sse extension is documented by focal mechanisms and gps data with a much smaller strain rate with respect to the past the transition between these two domains is accommodated by a n s discontinuity zone which runs from aeolian islands to mt etna with an extensional to strike slip deformation

crustal motion along the eurasia nubia plate boundary in the calabrian arc and sicily and active extension in the messina straits from gps measurements 1 we investigate crustal deformation along the eurasia nubia plate boundary in calabria and sicily revealed by the gps velocity field obtained by the combination of continuous site velocities with previous results from episodic campaigns we recognize two distinct crustal domains characterized by different motions and styles of deformation convergence in sicily is taken up by crustal shortening along the former tyrrhenian back arc passive margin in agreement with seismological data and geological evidence of recent cessation of deformation along the plio pleistocene subduction front the analysis of the gps data and the consistency between earthquake slip vectors and convergence direction suggest that eu nu convergence in sicily does not require intermediate crustal blocks significant eurasia 3 mm yr to nne and nubia fixed 5 mm yr to ese residual velocities in calabria suggest instead the presence of an intermediate crustal block which can be interpreted as a forearc sliver or as an independent ionian block according to the first hypothesis subduction is still active in the ionian wedge although we find no evidence for active back arc spreading in the tyrrhenian sea the n115 e oriented sicily calabria gps relative motion is consistent with the extension observed during the 1908 mw 7 1 messina earthquake we suggest that up to 3 mm yr 80 of this estimated relative motion between sicily and the calabrian arc may be taken up in the messina straits

kinematics of subduction and subduction induced flow in the upper mantle 1 results of fluid dynamical experiments are presented to model the kinematics of lithospheric subduction in the upper mantle the experiments model a dense high viscosity plate subducting lithosphere overlying a less dense low viscosity layer upper mantle the overriding lithosphere is not incorporated several important features of slab behavior were investigated including the temporal variability of hinge line migration the kinematic behavior of the slab and the subduction induced upper mantle flow both fixed and free trailing edge boundary conditions of the subducting plate were investigated results show that hinge line retreat is a natural consequence of subduction of a negatively buoyant slab the migration rate increases until the slab approaches the upper lower mantle discontinuity resulting in a decrease in migration rate followed by a renewed increase and finally approaching a steady state slab retreat results in mantle flow with material initially located underneath the slab flowing around the lateral slab edges toward the mantle wedge experimental results indicate that all rollback induced flow occurs around the lateral slab edges forcing the hinge line to attain a convex shape toward the direction of retreat no signs for poloidal flow underneath the slab tip have been detected only a small component of toroidal type flow was observed underneath slanting slab tips for a fixed trailing edge the slab does not sink vertically downward but sinks at an angle in a regressive manner for a free trailing edge slab sinking is oriented more vertically while the surface part of the subducting plate is pulled into the subduction zone

pattern of deformation around the central aeolian islands evidence from multichannel seismics and gps data the tectonics of the central aeolian islands which are located within the tyrrhenian backarc basin has been investigated through a marine seismic reflection survey we find that compressional structures dominate around the islands whereas extensional faults occur only to the north of salina and filicudi towards the marsili basin this pattern of deformation although different from previously reported is in agreement with the strain field and stress regime obtained from gps measurements and seismological data age constraints suggest that contractional deformation was active since middle pleistocene being coeval with the building of the volcanic edifices of the aeolian islands and is superimposed on pre existing extensional deformation compressional and extensional regimes therefore can coexist within a backarc setting seismic profiles show that the tindari letojanni fault considered as a major tectonic element does not extend to the north towards the island of vulcano as a throughgoing fault rather deformation is accommodated in a broader belt displaying greater structural complexity

the migration of plate boundaries in se sicily influence on the large scale kinematic model of the african promontory in southern italy abstract a detailed field mapping coupled with structural analyses and morphological investigation has been carried out along the northern and western borders of the hyblean plateau se sicily in order to define the nature and the kinematics of a major quaternary fault belt this here designed as the scicli line fault belt is composed of two n50 oriented extensional basins that linked by a regional n10 trending transfer zone originated during the early pleistocene and experienced since the late quaternary a positive tectonic inversion in both the two stages of deformation the scicli line fault belt has been characterised by displacement rate comparable with the relative velocities measured between the distinct plates composing the central mediterranean region in the period going from 1 5 1 2 to 0 85 ma the fault belt accommodated the entire divergence between adria and nubia at present the scicli line fault belt absorbs most of the nubia eurasia convergence while the western divergent margin of the adria microplate has jumped to the eastern and the southern margins of the hyblean plateau along the late quaternary siculo calabrian rift zone the off shore prolongation of the two tectonic boundaries of the hyblean plateau has been recognised in the sicily channel where they are both interrupted by a wnw ese oriented dextral fault according to our reconstruction the hyblean plateau represents an isolated lithospheric block whose evolution can be related to the propagation of the western divergent margin of the adria microplate accompanied with the southward migration of the triple junction between eurasia nubia and adria in this new large scale kinematic picture the gps velocity measured in the hyblean region at the permanent site of noto is actually representative of the local kinematics rather than of the entire african promontory of southern italy this implies a correction of previous regional kinematic models based on combination of gps vectors in particular our data constrain a new interpretation both for the kinematics along the e w oriented nubia eurasia margin dominated by prevalent dextral deformation rather than reverse motions and for the intraplate deformation in the sicily channel within the africa promontory which would be dominated by a roughly n110 oriented extension this conclusion has implication also on the mechanism and the origin of the pantelleria linosa malta rift that is here interpreted as a transtensive feature developed along a major transform fault rather than the result of passive rifting induced by the nubia eurasia collision as it is currently interpreted

foreland segmentation along an active convergent margin new constraints in southeastern sicily italy from seismic and geodetic observations abstract we performed an in depth analysis of the ongoing tectonics of a large sector of southern sicily including the hyblean foreland and the front of the maghrebian chain as well as the ionian sea offshore through the integration of seismic and gps observations collected in the nearly two decades in particular a dataset consisting of more than 1100 small to moderate magnitude earthquakes 1 0 ml 4 6 has been used for local earthquake tomography in order to trace the characteristics of the faulting systems and for focal mechanisms computation to resolve the current local stress field and to characterise the faulting regime of the investigated area in addition gps measurements carried out on both episodic and continuous stations allowed us to infer the main features of the current crustal deformation pattern main results evidence that the hyblean plateau is subject to a general strike slip faulting regime with a maximum horizontal stress axis nw se to nnw sse oriented in agreement with the eurasia nubia direction of convergence the plateau is separated into two different tectonic crustal blocks by the left lateral strike slip scicli ragusa fault system the western block moves in agreement with central sicily while the eastern one accommodates part of the contraction arising from the main eurasia nubia convergence furthermore we provided evidences leading to consider the hyblean maltese escarpment fault system as an active boundary characterised by a left lateral strike slip motion separating the eastern block of the plateau from the ionian basin all these evidences lend credit to a crustal segmentation of the southeastern sicily

a note on fault reactivation reactivation of existing faults whose normal lies in the 1 3 plane of a stress field with effective principal compressive stresses 1 2 3 is considered for the simplest frictional failure criterion n n p where and n are respectively the shear and normal stresses to the existing fault p is the fluid pressure and is the static friction for a plane oriented at to 1 the stress ratio for reactivation is 1 3 1 cot 1 tan this ratio has a minimum positive value at the optimum angle for reactivation given by 12tan 1 1 but reaches infinity when 2 beyond which 3 0 is a necessary condition for reactivation an important consequence is that for typical rock friction coefficients it is unlikely that normal faults will be reactivated as high angle reverse faults or thrusts as low angle normal faults unless the effective least principal stress is tensile

a multi tiered earthquake hazard model for australia abstract earthquakes result from tectonic processes and their distribution is strongly influenced by large scale geology and the tectonic stress field however earthquake hazard estimates particularly ground motion recurrence have traditionally been computed using source models based primarily on instrumental and historical seismicity in areas of low to moderate seismicity such as australia large earthquakes commonly occur in areas which have experienced little or no recent activity making it difficult to develop source models based solely on seismicity the seismotectonic model developed for australia that is presented here aus5 is based on geology geophysics tectonics and seismicity the model was developed using a number of tiers of information so that new information can easily be incorporated the information used includes but is not limited to tectonic provinces basins and ranges gravity magnetic topography and seismicity all on a regional scale on a local scale for a site specific earthquake hazard study active faulting can be incorporated to provide fault source zones an earthquake hazard map showing peak ground acceleration with a 10 chance of exceedance in 50 years for southeastern australia using the geologically defined seismotectonic model aus5 is presented as an indication of how the model performs

australia s large earthquakes and recent fault scarps abstract nineteen large earthquakes up to magnitude ms 6 8 have occurred within continental australia this century and at least seven recent prehistoric fault scarps have been discovered the magnitude of the earthquake causing each of these prehistoric fault scarps has been estimated from the observed fault length and maximum scarp height and none exeeds magnitude 7 0 their occurrence demonstrates that the australian plate is undergoing significant internal deformation but as yet there is no model to explain their cause nor the likely site of the next large earthquake the absence of earthquake epicentres on the current tectonic map of australia is a regrettable omission

crustal structure of central sicily abstract we processed crustal seismic profile siripro acquired across central sicily to improve the seismic image we utilized the wave equation datuming technique a process of upward or downward continuation of the wave field between two arbitrarily shaped surfaces wave equation datuming was applied to move shots and receivers to a given datum plane removing time shifts related to topography and to near surface velocity variations the datuming procedure largely contributed to attenuate ground roll enhance higher frequencies increase resolution and improve the signal noise ratio processed data allow recognizing geometries of crust structures differentiating seismic facies and offering a direct image of ongoing tectonic setting within variable lithologies characterizing the crust of central sicily migrated sections underline distinctive features of hyblean plateau foreland and above all a crustal thinning towards the caltanissetta trough to the contact with a likely deep permo triassic rifted basin or rather a zone of a continent to oceanic transition inhomogeneity and fragmentation of sicily crust with a distinct separation of central sicily basin from western and eastern blocks appear to have guided the tectonic transport inside the caltanissetta crustal scale syncline and the accumulation of allochthonous terrains with south and north verging thrusts major tectonic stack operated on the construction of a wide anticline of the maghrebian chain in northern sicily sequential south verging imbrications of deep elements forming the anticline core denote a crust wedge indenting foreland structures deformation processes involved multiple detachment planes down to decoupling levels located near crust mantle transition supporting a presence of high density lenses beneath the chain interrelated to a southwards push of tyrrhenian mantle and asthenosphere

forearc extension and slow rollback of the calabrian arc from gps measurements 1 here we describe the horizontal velocities of continuous gps stations in the calabrian arc ca and surrounding regions the appropriate reference frame to evaluate the crustal motion of the ca is considered by assessing the internal deformation and the relative motion of the crustal blocks in the foreland of the apennines ionian maghrebides subduction system we propose that the motion of ca relative to the subducting ionian lower plate is most properly assessed by minimizing the gps velocities in apulia in this reference frame the significant 2 mm yr southeastward motion of the stations on the ionian flank of the ca shows that the arc is still moving towards the trench in agreement with the observations of active shortening in the ioanian wedge this southeastward migration is associated to 1 4 0 3 mm yr e w extension of the forearc in northern calabria comparable with the seismic strain averaged in the last 500 years the limited subaerial exposure decreases the resolution on locking of the subduction interface but the distribution and direction of crustal extension along the ca impose important constraints on geodynamic interpretations of the area

discrimination of tsunami sources earthquake versus landslide on the basis of historical data in eastern sicily and southern calabria abstract the source mechanisms responsible for large historical tsunamis that have struck eastern sicily and southern calabria are a topic of robust debate we have compiled a database of historical coeval descriptions of three large tsunamis 11 january 1693 6 february 1783 and 28 december 1908 by using accounts of run up and inundation and employing an approach proposed by okal and synolakis in 2004 we can provide discriminants to define the nature of the near field tsunami sources fault dislocation or landslide historical reports for the 1908 event describe affected localities maximum run ups and inundation areas however for the 1693 and 1783 tsunamis reports are limited to inundation and occasional run up estimates we calculate run up values for these events using available relations between inundation and run up we employed the model of okal and synolakis to the obtained profiles of tsunami run up along the inundated shorelines the 1908 run up data distribution confirms that the tsunami is compatible with a seismic dislocation source whereas the 1783 data supports contemporary observations and recent offshore investigations suggesting that the tsunami was produced by an earthquake triggered submarine landslide analysis of the 1693 event data suggests that the tsunami was generated during a tectonic event and thus a seismogenic source should be found offshore

depth variation of seismic source scaling relations implications for earthquake hazard in southeastern australia abstract advances in earthquake data acquisition and processing techniques have allowed for improved quantification of source parameters for local australian earthquakes until recently only hypocentral locations and local magnitudes ml had been determined routinely with little attention given to the inversion of additional source parameters the present study uses these new source data e g seismic moment stress drop source dimensions to further extend our understanding of seismicity and the continental stress regime of the australian landmass and its peripheral regions earthquake activity within australia is typically low and the proportion of small to large events i e the b value is also low it is observed that average stress drops for southeastern australian earthquakes appear to increase with seismic moment to relatively high levels up to approximately 10 mpa for ml 5 0 earthquakes this is thought to be indicative of high compressive crustal stress coupled with strong rocks and fault asperities furthermore the data indicates that shallow focus earthquakes shallower than 6 km appear to produce lower than average stress drops than deeper earthquakes between 6 and 20 km with similar moment recurrence estimates were obtained for a discrete seismogenic zone in southeastern australia decreasing b values with increasing focal depth for this zone indicate that larger earthquakes with high stress drops tend to occur deeper in the crust this may offer an explanation for the apparent increase of stress drop with hypocentral depth consequently earthquake hazard estimates that assume a uniform gutenburg richter distribution with depth i e constant b value may be too conservative and therefore slightly overestimate seismic hazard for surface sites in southeastern australia