reassessing the rupture process of the 2009 l aquila earthquake mw 6 3 on the paganica fault and investigating the possibility of coseismic motion on secondary faults the kinematic rupture of the l aquila earthquake on the paganica fault is reassessed with a highly comprehensive set of data this very complete dataset is also used to explore the possibility that secondary faults may be involved in the coseismic process the main characteristics of the slip distribution of the paganica normal fault found by previous studies are confirmed an initial propagation around and up dip of the hypocenter associated with a high velocity rupture 3 5 km s a main asperity centered about 6 7 km southeast of the hypocenter rupturing in the subsequent stage with a maximum slip of nearly 1 5 m a total rupture measuring about 15 km along strike and 12 km along dip and an overall low average velocity rupture 2 km s the statement that the main features of the slip distribution are confirmed by different studies based on distinct inversion schemes is by itself an achievement knowing that many past studies provided strongly discrepant slip maps for common events moreover we focus specifically on the existence of slip at shallow depth and its relations with the other known active faults in the vicinity of the paganica fault we find that 1 as found in previous studies shallow slip near the ground surface up dip of the hypocenter is incompatible with the available synthetic aperture radar interferograms and 2 the only secondary fault that is likely to have been activated during the mainshock is the san gregorio synthetic fault located 2 3 km southwest of the paganica fault online material figures of waveform fitting using different velocity models time versus distance distribution of slip from the single fault model variations in the geometry of the paganica fault geometry of complex faults models and geodetic data modeling uncertainty on the slip value and the rupture time effect of noise on resolution tests quantification of the improvement on the gps data fitting with the preferred two faults model with respect to the single fault model and a posteriori modeling of leveling data

two cryogenian glacial successions compared aspects of the sturt and elatina sediment records of south australia abstract two cryogenian glacial sequences the sturt and elatina occur within the adelaide rift complex s australia and are part of an 8 km thick succession recording rodinia fragmentation and subsequent passive margin development we compare and contrast these glacial successions presenting new data including detailed logged sections for both glacial sequences facies analysis reveals a total of six facies associations recording a range of glacial and glacially related processes these are a diamictite facies association ice proximal debris flows a sheet sandstone facies association fluvial deposits a flaser and rhythmically bedded facies association tidal flat a hummocky cross stratified sandstone facies association shoreface to offshore transition zone deposits and an underflow facies association recording offshore deposition a sixth facies association a ferruginous lonestone bearing siltstone is restricted to the top of the elatina formation and records rapid environmental amelioration and emergence from glaciation in the central flinders ranges the sturt succession commences with a glacial erosion surface ges which in agreement with previous workers was probably enhanced by rifting this ges is overlain in ascending order by the pualco tillite holowilena ironstone and wilyerpa formation with the warcowie dolomite member at the base of this latter formation a second ges is preserved within this latter unit and is overlain by a stratigraphic motif that records an alternation of offshore transition zone and offshore deposits significant base level falls within the wilyerpa formation are identified by fluvial deposits sitting disconformably upon offshore deposits in contrast within the elatina formation a single ges is proposed which defines the base of the formation the elatina formation is split into two informal members on the basis of analysis of sediment stacking patterns and the recognition of a sharp stratigraphic surface that divides the formation apart from a locally preserved basal diamictite the lower member consists of fluvial deposits whereas the upper member is dominated by a mixture of tidal flat sediments and debris flow deposits the boundary between these units is therefore interpreted as a hybrid surface recording tidal ravinement in some areas and a glacial advance in others deglaciation left contrasting deposits the sturt deglaciation culminated in deposition of black shale of the tindelpina shale member of the tapley hill formation seemingly as a sheet like deposit over the adelaide rift complex and beyond into the amadeus basin of central australia the elatina deglaciation meanwhile began first with deposition of the sixth facies association ferruginous dropstone bearing siltstone then proceeded with deposition of cap dolostone of the nuccaleena formation

finite faults and inverse theory with applications to the 1979 imperial valley earthquake abstract using a representation theorem from elastodynamics subsurface slip on a known fault is formulated as the solution to an inverse problem in which recorded surface ground motion is the data two methods of solution are presented the least squares method which minimizes the squared differences between theory and data and the constrained least squares method which simultaneously maintains a set of linear inequalities instabilities in the solution are effectively eliminated in both methods and the sensitivity of the solution to small changes in the data is quantitatively stated the inversion methodology is applied to 77 components of near field ground acceleration recorded during the 15 october 1979 imperial valley earthquake the faulting is constrained to propagate bilaterally away from the epicenter at an average velocity of 90 per cent of the shear wave speed on a vertical fault plane extending from the surface to 10 km depth inequality constraints are used to keep the faulting sequence physically reasonable by maintaining right lateral motion and positive slip velocity the preferred solution is stable and provides a good fit to the data it is also realistic and consistent with observed surface offsets and independent estimates of seismic moment

allochthonous salt initiation and advance in the northern flinders and eastern willouran ranges south australia using outcrops to test subsurface based models from the northern gulf of mexico the northern flinders ranges and eastern willouran ranges south australia expose neoproterozoic salt diapirs salt sheets and associated growth strata that provide a natural laboratory for testing and refining models of allochthonous salt initiation and emplacement the diapiric callanna group 850 800 ma comprises a lithologically diverse assemblage of brecciated rocks that were originally interbedded with evaporites that are now absent using stereonet analysis to derive three dimensional information from two dimensional outcrops of stratal geometries flanking salt diapirs and beneath salt sheets we evaluate 10 examples of the transition from steep diapirs to salt sheets 3 of ramp to flat geometries and 2 of flat to ramp transitions stratal geometries adjacent to feeder diapirs range from a minibasin scale megaflap to halokinetic drape folds to high angle truncations and appear to have no relationship to subsequent allochthonous salt development in all cases the transition from steep diapirs to salt sheets is abrupt and involved piston like breakthrough of thin roof strata which permitted salt to flow laterally we suggest two models to explain the transition from steep diapirs to subhorizontal salt 1 salt top breakout where salt rise occurs inboard of the salt flank thereby preserving part of the roof strata beneath the sheet and 2 salt edge breakout where rise occurs at the edge of the diapir with no roof preservation lateral emplacement of salt sheets is dependent on the interplay between the rate of salt supply to the front of the sheet and the sediment accumulation rate when the ratio of salt supply rate to sediment accumulation rate is high to moderate thrust advance produces base salt flats and truncation ramps respectively halokinetic folds are absent because the thrust emerges at the base of the sea floor scarp and mass transport complexes are rare as a result of relatively low scarp relief if the ratio is low pinned inflation leads to drape folding of the top salt and cover into a fold ramp with occasional slumping of the sheet and its roof and further breakout on thrust or reverse faults in the shallow water depositional environments of south australia lateral emplacement of salt sheets occurred through some combination of thrust advance extrusive advance and open toed advance with no evidence for subsalt thrust imbricates shear zones or continuous rubble zones in deep water environments such as the northern gulf of mexico thrust imbricates and rubble zones which represent slumped carapace are more common the presence of slumped carapace is caused primarily by higher topographic relief related to thicker hemipelagic roofs a lack of dissolution and gravity driven transport of overburden strata to the toes of large canopies

environmental interpretation and a sequence stratigraphic framework for the terminal proterozoic ediacara member within the rawnsley quartzite south australia abstract fossils of the ediacara biota are confined to preservational windows in the ediacara member of the rawnsley quartzite pound subgroup from the flinders ranges south australia the base of the ediacara member is a type 1 sequence boundary incised into the partly lithified chace quartzite member of the rawnsley quartzite the ediacara member and the upper half of the rawnsley quartzite comprise the rawnsley depositional sequence bounded above by the early cambrian uratanna depositional sequence the rawnsley sequence developed over an erosional surface cut into the chace quartzite member with some 250 m of relief southeasterly directed palaeovalleys are filled with a sequence of massive sandstone and laminated siltstone passing up into well bedded sandstone at lowstand local channels were filled by massive sand the highstand systems tract consists of several parasequence sets of laminated siltstone and channelized amalgamated massive sandstone overlain by interbedded siltstone and sandstone grading up into well bedded clean sandstone impressions of soft bodied ediacaran organisms are preserved above the valley fill facies on sandstone partings within upward shoaling delta front environments between storm and fairweather wavebase the ediacara member is in places conformably overlain by up to 500 m of sandstone of the same lithofacies as those underlying the member distinctive microbial mat bound sand laminae described as petee structures are characteristic of the rawnsley quartzite above and below the ediacara member during deposition of the ediacara member colonization of the deeper substrates by microbial mat communities enabled preservation of the ediacara biota the erosional surface at the base of the ediacara member is one of at least four incision events recorded in the terminal proterozoic and early cambrian succession of the adelaide geosyncline the similarity of incision filling lithofacies of the rawnsley and uratanna sequences has in condensed sections led to confusion between the depositional sequences characteristic trace and body fossil assemblages provide the only clear distinction between depositional cycles spanning the proterozoic cambrian boundary

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

the geological setting of tourmalinite at rum jungle n t australia genetic and economic implications tourmalinite is a common rock type associated with proterozoic strata bound mineral deposits although common it is often difficult to recognise in the field leading to misidentification it occurs as a conformable banded quartz tourmaline lithological unit comprising at least 15 and as much as 50 of the rock at rum jungle tourmalinite occurs within the oldest sediments arenites and magnesites as distinct lenses as facies equivalents of quartz magnetite units and mafic schists tuffs and distal equivalents of polymetallic sulfides distinct layering slump folding rip up clasts and the association with diagenetic pyrite suggest a sedimentary environment enechelon fracturing of the fine grained light green tourmaline crystals spectacularly supports pre deformation formation the crystals are optically and chemically zoned parallel to the c axis with irregular growth lamellae width which supports a pre regional metamorphic origin analyses show the tourmaline to be the mg rich variety dravite most tourmalinites are interpreted as subaqueous marine deposits it is more likely that they form in lacustrine shallow water evaporitic environments particularly continental rifts suitable b bearing fluids can be generated by hotspring activity and mobilized by co2 rich fluids association with chemical sediments suggests tourmalinites also have a chemical sediment precursor ample evidence at rum jungle supports the notion of a continental rift environment which was the site of deposition of fluvial arenites and alkaline evaporitic lake sediments localised hot spring activity contributed b bearing fluids which precipitated chemical sediments according to the pertaining ph temperature etc diagenetic alteration produced the tourmalinite now present these tourmalinites are comparable to those of similar age elsewhere e g sullivan broken hill they can be genetically modelled upon recent borate concentrations all of which occur in continental rift environments

coseismic deformation of the destructive april 6 2009 l aquila earthquake central italy from gps data 1 on april 6 2009 01 32 39 gmt the city of l aquila was struck by a mw 6 3 earthquake that killed 307 people causing severe destruction and ground cracks in a wide area around the epicenter four days before the main shock we augmented the existing permanent gps network with five gps stations of the central apennine geodetic network cageonet bordering the l aquila basin the maximum horizontal and vertical coseismic surface displacements detected at these stations was 10 39 0 45 cm and 15 64 1 55 cm respectively fixing the strike direction according to focal mechanism estimates we estimated the source geometry with a non linear inversion of the geodetic data our best fitting fault model is a 13 15 7 km2 rectangular fault sw dipping at 55 3 1 8 consistent with the position of observed surface ruptures the estimated slip 495 29 mm corresponds to a 6 3 moment magnitude in excellent agreement with seismological data

complexity of the rupture process during the 2009 l aquila italy earthquake summary in this study we investigate the rupture history of the 2009 april 6 mw 6 1 l aquila normal faulting earthquake by using a non linear inversion of strong motion gps and dinsar data both the separate and joint inversion solutions reveal a complex rupture process and a heterogeneous slip distribution slip is concentrated in two main asperities a smaller shallow patch of slip located updip from the hypocentre and a second deeper and larger asperity located southeastwards along strike direction the key feature of the source process emerging from our inverted models concerns the rupture history which is characterized by two distinct stages the first stage begins with rupture nucleation and with updip propagation at relatively high 4 0 km s 1 but still subshear rupture velocity the second stage starts nearly 2 0 2 5 s after nucleation and it is characterized by the along strike rupture propagation the largest and deeper asperity fails during this stage of the rupture process the rupture velocity is larger in the updip than in the along strike direction the updip and along strike rupture propagation are separated in time and associated with a mode ii and a mode iii crack respectively the comparison between the source models inferred in this study with the poisson ratio anomalies in the crustal volume containing the fault plane allows the interpretation of the delay in along strike rupture propagation in terms of a structural control of the rupture history our results show that the l aquila earthquake featured a very complex rupture with strong spatial and temporal heterogeneities suggesting a strong frictional and or structural control of the rupture process

control of the 2009 l aquila earthquake central italy by a high velocity structure a receiver function study 1 receiver functions rfs analyzed at two permanent broadband seismic stations operating in the epicentral area of the mw 6 3 2009 l aquila earthquake central italy yield insight on crustal structure along the fault rupture the harmonic decomposition of rfs highlights a subsurface structure in which both isotropic and anisotropic features are present we model the waveforms using recently developed monte carlo methods the retrieved models display a common depth structure between 10 and 40 km depth consistent with the under thrusting of the adria lithosphere underneath the apennines belt along the fault in the uppermost crust the s wave velocity structure is laterally heterogeneous right above the hypocenter we find a 4 6 km thick very high s wave velocity body vs as high as 4 2 km s that is absent in the se portion of the fault where the earthquake propagated the high vs body is coincident with the area of fewer aftershocks and is anticorrelated with the maximum slip patches of the earthquake as modeled by differential interferometric synthetic aperture radar dinsar and strong motion data we interpret this high vs body as a high strength barrier responsible for the high peak ground motion in the near field observed in the l aquila city and surroundings and for the complexity in the rupture evolution the retrieved seismic s wave velocity of this body far exceeds common vs values in the upper crust and it is more compatible with values observed in mafic basement rocks

insar data as a field guide for mapping minor earthquake surface ruptures ground displacements along the paganica fault during the 6 april 2009 l aquila earthquake 1 on 6 april 2009 a moderate earthquake mw 6 3 ml 5 8 struck the abruzzo region in central italy causing more than 300 fatalities and heavy damage to l aquila and surrounding villages coseismic surface effects have been thoroughly documented by timely field surveys as well as by remote sensing analyses of satellite images the outstanding quality of geological seismological geodetic and interferometric synthetic aperture radar insar information arguably represents the best ever data set made available immediately after a moderate seismic event based on this data set we aim at testing the capability of coupled geological and insar data to map surface faulting patterns associated with moderate earthquakes coseismic ground ruptures have been mapped at a scale of 1 500 in the whole epicentral area traces of surface ruptures have been inferred from linear phase discontinuities identified in the interferogram a very good agreement between the two methods resulted in the characterization of the main surface rupture along the paganica fault the same approach applied to ground ruptures hypothesized along other capable fault segments provided more questionable results thus the combined field and insar approach appeared useful for detecting continuous surface ruptures exceeding 1 km in length and showing displacements greater than a few centimeters these are the typical faulting parameters for moderate earthquakes 6 0 mw 6 5 in central apennines for continuous ground cracks shorter than a few hundred meters and or that show displacements smaller than 1 2 cm the described approach may be less helpful most probably due to the limited resolution of the data

surface deformation in the abruzzi region central italy from multitemporal dinsar analysis summary we investigate the 1992 2000 surface deformation affecting the abruzzi region central italy by exploiting two set of synthetic aperture radar sar data acquired by the ers 1 2 sar sensors from ascending and descending orbits respectively we apply the small baseline subset sbas differential synthetic aperture radar interferometry dinsar technique to the sar data set to estimate the displacement time series and the corresponding velocity maps our dinsar analysis allows us to detect a previously unreported major change in crustal deformation moving from the highest elevation of the central apennines to the adriatic sector that we infer as evidence of a complex tectonic boundary between two adriatic microplates involving a wide interaction zone an extension effect at a rate of about 0 10 10 6 yr 1 is also confirmed by our investigation our findings may have important implications in the seismic hazard assessment within the adriatic region in central italy

coseismic and post seismic slip of the 2009 l aquila central italy mw 6 3 earthquake and implications for seismic potential along the campotosto fault from joint inversion of high precision levelling insar and gps data abstract after the april 6th 2009 m w 6 3 m l 5 9 l aquila earthquake central italy we re measured more than 100 km of high precision levelling lines in the epicentral area the joint inversion of the levelling measurements with insar and gps measurements allowed us to derive new coseismic and post seismic slip distributions and to describe with high resolution details on surface displacements the activation and the slip distribution of a secondary fault during the aftershock sequence that struck the campotosto area major event m w 5 2 coseismic slip on the paganica fault occurred on one main asperity while the afterslip distribution shows a more complex pattern occurring on three main patches including both slips on the shallow portions and on the deeper parts of the rupture plane the comparison between coseismic and post seismic slip distributions strongly suggests that afterslip was triggered at the edges of the coseismic asperity the activation of a segment of the campotosto fault during the aftershock sequence with a good correlation between the estimated slipping area moment release and distribution of aftershocks raises the opportunity to discuss the local seismic hazard following the occurrence of the 2009 l aquila mainshock the campotosto fault appears capable of generating earthquakes as large as historical events in the region m 6 5 or as small as the ones associated with the 2009 sequence in the case that the campotosto fault is accumulating a significant portion of the current interseismic deformation the 2009 m w 5 events will have released only a small amount of the accumulated elastic strain and then a significant hazard still remains in the area continuing geodetic monitoring and a densification of the gps networks in the region are therefore needed to estimate the tectonic loading across the different recognized active fault systems in this part of the apennines

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

characterizing halokinesis and timing of salt movement in the abu musa salt diapir persian gulf offshore iran abstract geometric and stratigraphic characteristics of halokinetic sequences adjacent to the salt diapirs highlight the sedimentation response to variation in the rate of salt rise the style of salt movement sedimentation interaction and episodes of salt movement can be reconstructed by mapping these halokinetic sequences adjacent to the diapirs detailed interpretation of 2d seismic profiles adjacent to the abu musa salt diapir within the persian gulf basin offshore iran indicates that this diapir originated from the miocene fars salt which created a central and several ring like peripheral salt structures our results show that the evolution of the salt structures take place in three stages mound dome and post dome associated with sedimentation cycles periodically by passive and active rising to present the pattern of these halokinetic sequences reveals that the fars salt rose since mid miocene coeval sedimentation of the gachsaran formation the main mechanism of driving salt body has been the differential loading caused by down building processes

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

basin geometry and salt diapirs in the flinders ranges south australia insights gained from geologically constrained modelling of potential field data abstract the adelaide basin in australia is a complex of late neoproterozoic to early cambrian rift and sag basins which was inverted during the cambro ordovician delamerian orogeny the deposition of evaporitic sediments during the earliest stage of basin development in the late neoproterozoic willouran age played a major role in the subsequent tectonic evolution of the basin previous studies have shown that early mobilization vertical transport and withdrawal of the evaporites influenced the sedimentation during the late neoproterozoic and early cambrian the evaporites also influenced deformation during the inversion of the basin and the development of the delamerian fold and thrust belt however the control exerted by basement structures in the deposition of the evaporitic beds and the role of these tectonic structures in the later inversion of the basin have been poorly constrained in this work we use a combination of published and original geological observations along with the interpretation of potential field datasets total magnetic intensity and bouguer anomaly data to better constrain the geology of the basin at depth we construct two and a half dimensional forward models of the potential field data along selected profiles across the adelaide basin these models are constrained by the geology at the surface drill hole data and measured petrophysical properties specific gravity and magnetic susceptibility we achieved the best fit between observed and modelled potential fields with a model favouring thick skinned deformation where the diapirs are not randomly distributed but located directly above basement penetrating normal faults furthermore these normal faults were probably active during the sedimentation of the late neoproterozoic and early cambrian sediments and underwent partial or total inversion during the cambro ordovician delamerian orogeny mobilisation and withdrawal of the evaporites was therefore initiated and facilitated by the extension coeval with the opening of the basin and continued during the subsequent delamerian orogeny

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

mechanics of active salt diapirism abstract an active diapir forcefully intrudes its overburden driven by diapir pressure that overcomes the resistance of the overburden strength possible causes for the driving pressure are differential loading of the source layer and a density contrast with the overburden possible resisting forces derive from the mass of the roof block and resistance to the faulting and folding that accommodate the intrusion for a typical density contrast between salt and a sedimentary overburden a simple force balance demonstrates that the diapir height must be more than two thirds to three quarters the thickness of the surrounding overburden to initiate substantial active diapirism narrow diapirs must be even taller physical and numerical modeling show that typical structures of active diapirism are a central crestal graben flanked by relatively unstrained flaps that rotate upward and outward curved reverse faults can separate the flaps from the regional overburden normal faults in the crestal graben propagate downward with new faults created farther outward as the roof arches over the rising diapir thin wide roofs develop multiple grabens separating a relatively flat roof from the rotating flaps in cases leading to emergence the piercing diapir evolves from a pointed crest to a progressively rounded and widening crest as the flaps rotate outward the numerical models show that overburden flexure contributes to early formation of active diapir structures but piercement does not continue to emergence unless the diapir is very wide or tall relative to the overburden thickness active diapirism becomes progressively more difficult for diapir crests ranging from a rectangle a round cornered rectangle a semicircle to a triangle with a pointed crest

coseismic ground deformation of the 6 april 2009 l aquila earthquake central italy mw6 3 1 we provide field data of coseismic ground deformation related to the 6 april mw 6 3 l aquila normal faulting earthquake three narrow fracture zones were mapped paganica colle enzano p e mt castellano mt stabiata c s and san gregorio sg these zones define 13 km of surface ruptures that strike at 130 140 we mapped four main types of ground deformation free faces on bedrock fault scarps faulting along synthetic splays and fissures with or without slip that are probably due to the near surface lithology of the fault walls and the amount of slip that approached the surface coseismically the p e and c s zones are characterized by downthrow to the sw up to 10 cm and opening up to 12 cm while the sg zone is characterized only by opening afterslip throw rates of 0 5 0 6 mm day were measured along the paganica fault where paleoseismic evidence reveals recurring paleo earthquakes and post 24 8 kyr slip rate 0 24 mm yr

internal kinematics of salt diapirs the internal structure of intrusive and extrusive salt bodies elucidates their external shape and the mechanism and history of diapiric emplacement information relevant to petroleum exploration trace amounts of brine can act like heat to weaken salt and promote geologic creep by solution transfer mechanisms we compare natural strain markers in salt with the artificial markers used by fluid dynamicists stream lines are the smooth flow paths followed by fluid particles stream surfaces separate flow laminae and contain the stream lines grain shape fabrics in salt anneal readily and have strain memories so short that lineations map the stream lines and foliations map the stream surfaces of the last stages of deformation by contrast larger structures like folded beddi g have much longer strain memories as a result multiple generations of tonguelike recumbent flow folds formed by unsteady flow in the mother source layer rotate to upright sheath folds or spines in the stems of diapirs here they are constricted and refolded into steep curtain folds to form crescentic and other interference patterns visible in the roofs of salt mines mature diapirs can form crestal bulbs which may be balloon or mushroom shaped and which potentially form larger petroleum traps than previously supposed screens of country rock may be entrained between the stem and peripheral overhanging lobes caused by episodic sedimentation

determination of the fault plane using a single near field seismic station with a finite dimension source model summary we explore the possibility of determining the actual fault plane of an earthquake from the inversion of near source displacement seismograms of one station when a finitedimension source is used instead of a point source model and when the complete displacement is taken into account including near field waves tests on synthetic seismograms and real data recorded at local distances show that this is possible even with a single three component station a single accelerogram available for the erzincan turkey 1992 march 13 m s 6 8 earthquake is inverted and the solution found is compatible with other seismological studies and with the mechanism expected for the north anatolian fault

moho depth and vp vs ratio in peninsular italy from teleseismic receiver functions 1 we present a new data set of moho depth estimates for peninsular italy obtained from receiver functions analysis and a grid search approach teleseismic records from 174 broadband seismic stations were used to compute the receiver function data set in general our results agree well with previous knowledge adding original information in many regions where previous data were lacking or uncertain we find broad regions with consistent moho depth namely 1 the peri tyrrhenian areas bordering the homonymous sea have a 20 to 25 km deep moho 2 the foreland regions adriatic apulia iblean with 30 35 km deep moho 3 the apennines belt where we find westward deepening of the adriatic moho down to 50 km depth that well delineate the westward adria subduction overlayed by the shallow tyrrhenian moho 4 calabria shows a flat 40 km deep moho suddenly dipping at high angle from the tyrrhenian coast westward defining the ionian subduction and 5 a clear separation between northern and southern apennines is marked by a region of almost flat moho possible evidence of a detached slab in between we also find that in the northern apennines the shallow tyrrhenian moho is continuous for more than 200 km from the sea to under the northern apennines with a generally flat geometry and a few undulations suggesting either the boudinage or episodic pulses of extension of the tyrrhenian crust during its pliocene quaternary stretching the eastward extent of the tyrrhenian moho below the apenninic belt approximately corresponds to the eastward extent of the observed extension in the upper crust as mapped by the normal faulting earthquakes in this portion of the apennines we interpret an intracrustal discontinuity sw dipping below the belt parallel to the adria moho as the top of the lower crust being subducted beneath the apennines the subcrustal earthquakes of this region down to 80 km depth seem to be located within this subducted crustal layer the southern apennines show the same general geometry of subduction as the northern arc although the former have a less defined on land extended region and no earthquakes in the lower crust uppermost mantle in between the central apennines present a different moho geometry no clear doubling of the two plates but rather a constant bilateral deepening possibly associated to a crustal root with no evidence of a subduction setting this reinforces the hypothesis of a detached slab in this area we also present the first large scale mapping of average crustal vp vs ratios for peninsular italy the results although representing averages over the whole crust enhance some interesting features the most evident are belts of high vp vs in the thinned crust of the apennines where extension has long been active in the quaternary probably as an effect of highly fractured rocks with abundant fluid circulation strong correlation exists between areas of high vp vs and quaternary volcanoes suggesting the presence of fluids at depth

a neoproterozoic fringing stromatolite reef complex flinders ranges south australia abstract a series of 14 microbial buildups outcrop in stark topographic relief along the western edge of the enorama diapir in the central flinders zone of the adelaide geosyncline south australia the enclosing stratigraphic unit the enorama shale is in the locally named interglacial succession between the sturtian and marinoan varanger equivalent glacigenic units thereby placing the reefs within the upper cryogenian locally derived conglomerates showing progressive cannibalisation indicate that this diapir was active during reef and mound growth apparent gradual onlap of the enorama shale against the diapir controlled in part by the present structural disposition has allowed good resolution of the individual buildups movement of the diapir during and after reef growth has turned the succession to vertical so that the features are seen in section view provision of a clean stable substrate controlled the establishment of the buildups a core facies of cumulate stromatolite domes first formed mounds which interfingered with the surrounding sediments then reefs which stood well above the sea floor not all mounds progressed to reefs as the edge of the active diapir was unstable at times the maximum size of a mound plus reef is ca 50 m high and 200 m across the base at a microscopic scale the core facies shows distinctive clotted textures reminiscent of the calcimicrobes epiphyton and renalcis although a contribution to the stromatolitic domes from microbial activity is also possible the entire reef complex has been completely dolomitised probably by solutions emanating from the diapir early dolomite cement has allowed the preservation of the sedimentary textures and some porosity the reefs grew during a time of sea level rise and show a close relationship with the enorama diapir the diapir provided an area of shallow water around an island at a time when deeper water shale was being deposited in the rest of the basin the mound to reef transition shows catch up and keep up growth habit but the sudden demise of individual reefs appears related to pulses of movement on the diapir

the c 32 alkane 1 15 diol as a tracer for riverine input in coastal seas long chain alkyl diols are lipids that occur ubiquitously in marine sediments and are used as a proxy for sea surface temperature sst using the long chain diol index ldi and for upwelling intensity high nutrient conditions the distribution of 1 13 and 1 15 diols has been documented in open marine and lacustrine sediments and suspended particulate matter but rarely in coastal seas receiving a significant riverine and thus continental organic matter input here we studied the distribution of diols in four shelf seas with major river outflows the gulf of lion the kara sea the amazon shelf and the berau delta covering a wide range of climate conditions the relative abundance of the c32 1 15 diol is consistently higher close to the river mouth and particularly in the suspended particulate matter of the rivers suggesting a terrigenous source this is supported by statistical analysis which points out a significant positive correlation between the c32 1 15 diol and the branched and isoprenoid tetraether index a proxy reflecting soil and riverine input in marine environments however the c32 1 15 diol was not detected in soils and is unlikely to be derived from vegetation suggesting that the c32 1 15 diol is mainly produced in rivers this agrees with the observation that it is a dominant diol in most cultivated freshwater eustigmatophyte algae we therefore suggest that the relative abundance of the c32 1 15 diol can potentially be used as a proxy for riverine organic matter input in shelf seas our results also show that long chain alkyl diols delivered by rivers can substantially affect ldi reconstructed ssts in coastal regions close to river mouths

restoration of cross sections above intrusive salt domes the applicability of bed length restoration to the sequence above a vertical intrusion of salt was tested on an experimental model that included deposition of units during uplift restoration of the model resulted in an apparently unbalanced cross section due to excess bed length in the pre growth interval the excess bed length was due to significant internal strain for a correct restoration it is thus important to distinguish between the growth and pre growth sequences the thinning index which quantifies the thinning onto the uplift aids in making this distinction a thinning index vs depth curve has a sharp inflection at the top of the pre growth sequence the pre growth sequence is restored by area balancing the growth sequence deforms mainly by formation of a restal graben with little other strain sequential restoration of growth intervals shows the growth history of the dome when applied to the pool creek salt dome from the mississippi interior salt basin the methods developed for the model served to separate the pre growth from the growth sequence and to indicate a growth history of vertical intrusion changing through time to vertical intrusion plus regional extension

physical modeling of structures formed by salt withdrawal implications for deformation caused by salt dissolution by creating 15 physical models we investigated deformation above subsiding tabular salt salt walls and salt stocks dry quartz sand simulated a brittle sedimentary roof above viscous silicone representing salt the modeled diapiric walls had linear planforms and rectangular semicircular triangular or leaning cross sectional shapes the stock was cylindrical in models where the source layer or allochthonous salt sheet was initially tabular a gentle flat bottomed syncline bounded by monoclinal flexures formed above a linear zone where the silicone was locally removed above all subsiding diapirs the deformed roof was bounded by an inner zone of steep convex upward reverse faults and an outer zone of normal faults above subsiding diapiric walls extensional and contractional zones were balanced above the subsiding salt stock conical concentric fault zones comprised inner reverse faults and outer normal faults sediments were added both before prekinematic and during synkinematic salt withdrawal in entirely prekinematic roofs reverse fault zones and normal fault zones both widened with time reverse faults propagated upward from the corners of the withdrawing diapirs new reverse faults formed in the footwalls of reverse faults each nearer the center of the deepening roof trough conversely new normal faults formed successively outward from the sagging trough synkinematic deposition retarded faulting but the pattern of inner reverse and outer normal faults was repeated however reverse faults formed successively outward whereas normal faults formed inward new conceptual models suggest that salt dissolution forms similar structures to those physically modeled for salt withdrawal the appropriate physical models resemble natural dissolution structures above tabular salt extension alone above diapirs is not caused merely by salt withdrawal or dissolution but by regional extension or active diapirism

proterozoic canyons of the flinders ranges south australia submarine canyons or drowned river valleys abstract a number of kilometer sized erosional incisions canyons occur within a specific stratigraphic interval in the late proterozoic succession of the adelaide geosyncline flinders ranges south australia this paper describes in detail four adjacent east west orientated incisions in the northern flinders ranges which are interpreted to be part of an ancient sinuously meandering canyon system at least 600 m of siltstones and fine sandstones of the bunyeroo and the brachina formations were removed during the erosional event that produced the canyon infilling sediments which exhibit a similar succession in each incision were deposited during emplacement of the wonoka formation although an identical sedimentary succession occurs within each incision palaeocurrents determined from flute casts at the bases of sandstone beds alternate by close to 180 from one erosional feature to the next basal infilling sediments commonly contain lenticular breccias interpreted as slumps derived from the brachina formation which forms the incision walls it is significant that clasts in these breccias preserve evidence of lithification predating the erosional event that produced the incisions channel filling debris flow units which occur mainly above the basal slumps along with associated sandstones were most likely emplaced episodically asymmetric ripple cross laminae in the sandstone beds above and within debris flow units commonly are wave modified isolated occurrences of hummocky cross stratification are observed in most units of the incision fill a thin

structure and evolution of upheaval dome a pinched off salt diapir upheaval dome canyonlands national park utah is an enigmatic structure previously attributed to underlying salt doming cryptovolcanic explosion fluid escape or meteoritic impact we propose that an overhanging diapir of partly extrusive salt was pinched off from its stem and subsequently eroded many features support this inference especially synsedimentary structures that indicate jurassic growth of the dome over at least 20 m y conversely evidence favoring other hypotheses seems sparse and equivocal in the rim syncline strata were thinned by circumferentially striking low angle extensional faults verging both inward toward the center of the dome and outward near the dome s core radial shortening produced constrictional bulk strain forming an inward verging thrust duplex and tight to isoclinal circumferentially trending folds farther inward circumferential shortening predominated radially trending growth folds and imbricate thrusts pass inward into steep clastic dikes in the dome s core we infer that abortive salt glaciers spread from a passive salt stock during late triassic and early jurassic time during middle jurassic time the allochthonous salt spread into a pancake shaped glacier inferred to be 3 km in diameter diapiric pinch off may have involved inward gravitational collapse of the country rocks which intensely constricted the center of the dome sediments in the axial shear zone beneath the glacier steepened to near vertical the central uplift is inferred to be the toe of the convergent gravity spreading system

joint inversion of insar gps teleseismic and strong motion data for the spatial and temporal distribution of earthquake slip application to the 1999 izmit mainshock the space time distribution of slip of the 17 august 1999 izmit earthquake is investigated by inverting synthetic aperture radar sar interferometry and global positioning system gps data together with teleseismic broadband and near field strong motion records surface offsets are used as an added constraint special emphasis is given to analysis of the resolution of the different data sets we use a four segment finite fault model and a nonlinear inversion scheme allowing slip to vary in amplitude direction and duration as well as variable rupture velocity from the inversion of synthetic data we find that the best spatial resolution can be expected in the upper half of the fault model above 12 km where coverage of the interferometric sar data is good western half of the rupture and near the gps and strong motion stations teleseismic data are found to have a lower resolution that is more evenly distributed over the fault model the joint inversion of all the data sets has an increased resolving power compared with the separate inversions and gives a more robust description of the space and time distribution of slip our study shows the importance of resolution tests in evaluating the reliability of earthquake kinematic models and it confirms that an excellent fit of a single kind of data does not necessarily imply a good retrieval of the kinematic properties of an earthquake the izmit rupture which is almost pure right lateral strike slip faulting is dominated by the bilateral breaking of a central asperity located between 29 7 e about 10 km west of the city of golcuk and 30 4 e eastern margin of sapanka lake with slip reaching 6 8 m in the depth range 6 12 km the western termination of the rupture is found near the city of yalova but large slip ends around 29 7 e about 10 km east of hersek delta a second area of large slip is required by all the data sets further east toward the city of duzce between 30 7 e and 31 1 e karadere and duzce faults this eastern slip zone which is separated from the main central asperity by an area of greatly reduced slip is less well constrained by the data however a strong motion station near the city of duzce helps to locate a high slip patch near 31 1 e in the depth range 6 12 km the total seismic moment resulting from the joint inversion is 2 4 1027 dyne cm most of the energy release occurred in a short time less than 15 sec corresponding to the bilateral breaking of the central asperity rupture propagation is relatively uniform and fast toward the west with a rupture velocity close to 3 5 km sec propagation of large slip toward the east is initially slower but it accelerates during a short time interval about 10 sec after rupture nucleation eastward progression then slows down to less than 2 km sec after 15 sec and rupture almost vanishes in amplitude ca 20 sec after initiation rupture propagation then proceeds on the easternmost karadere and duzce fault segments east of 30 7 e from 22 to ca 50 sec supershear rupture propagation is not required for modeling the waveforms considered in this study the hypocenter of the duzce earthquake which occurred 3 months later 12 november 1999 m w 7 2 is located in the immediate vicinity of the easternmost slip patch of the izmit earthquake manuscript received 28 july 2000

drastic changes in the distribution of branched tetraether lipids in suspended matter and sediments from the yenisei river and kara sea siberia implications for the use of brgdgt based proxies in coastal marine sediments abstract the distribution of branched glycerol dialkyl glycerol tetraethers brgdgts in soils has been shown to correlate with ph and mean annual air temperature because of this dependence brgdgts have found an application as palaeoclimate proxies in coastal marine sediments based on the assumption that their distribution is not altered during the transport from soils to marine systems by rivers to study the processes acting on the brgdgt distributions we analysed the full suite of brgdgts including the recently described 6 me brgdgts in both the suspended particulate matter spm of the siberian yenisei river and the spm and sediments of its outflow in the kara sea the brgdgt distribution in the spm of the yenisei river was fairly constant and characterized by high abundances of the 6 me brgdgts reflecting their production at the neutral ph of the river water however the brgdgt distribution showed marked shifts in the marine system firstly in the yenisei river mouth the fractional abundance of the 6 me brgdgts decreases sharply the brgdgt signature in the yenisei river mouth possibly reflects brgdgts delivered during the spring floods that may carry a different distribution also coastal cliffs were shown to contain brgdgts and to influence especially those sites without major river inputs e g khalmyer bay further removed from the river mouth in situ production of brgdgts in the marine system influences the distribution however also the fractional abundance of the tetramethylated brgdgt ia increases resulting in a distribution that is distinct from in situ produced signals at similar latitudes svalbard we suggest that this shift may be caused by preferential degradation of labile riverine in situ produced brgdgts and the subsequent enrichment in less labile soil material the offshore distribution indeed agrees with the brgdgt distribution encountered in a lowland peat this implies that the offshore kara sea sediments possibly carry a soil dominated signal indicating potential for palaeoclimate reconstructions at this site both in the river system and coastal cliffs brgdgts were much more abundant than crenarchaeol an archaeal isoprenoid gdgt resulting in high 0 93 branched and isoprenoid tetraether bit index values moving downstream in the marine sediments a decrease in brgdgt concentrations coeval with an increase in crenarchaeol resulted in decreasing bit index values this decrease correlates with changes in bulk proxies for terrigenous input 13corg c n confirming the use of the bit index to trace the delivery of river transported and coastal cliff derived terrigenous organic matter

geochemistry of synsedimentary cements in early cambrian reefs abstract synsedimentary fibrous calcite cements in reefs representing different periods of early cambrian time from eastern siberia southern australia and eastern canada were analyzed to determine whether they retained information about the chemical and isotopic compositions of the seawater from which they precipitated although petrographically similar the sr o and c isotopic compositions as well as the sr and mg contents of the cements from the three areas are different such differences can be attributed to varying degrees of diagenesis of the cements that correlate with the tectonic history of each area cements from the siberian craton are the least altered cements from near the appalachian orogen are partially altered and cements from the flinders fold and thrust belt are extensively altered strontium contents of the fibrous cements generally increase with mg contents although the correlation among these two elements is more variable than that reported for devonian or holocene cements those cements with sr mg ratios near 0 04 which include clear fibrous calcite have the lowest 87 sr 86 sr ratios and have been least altered strontium isotopic ratios in the least altered cements are lower than whole rock ratios and probably approach the original values of early cambrian seawater 18o values in the cements are variable because of exchange with diagenetic fluids whereas 13c values exhibit local variations that do not match temporal curves constructed from whole rock data for the same regions thus most of the original chemical and isotopic compositions of these cements have been variably changed through diagenesis although limited information about the composition of early cambrian seawater such as sr and c isotopic compositions have been retained in some samples

coseismic stress and strain field changes investigation through 3 d finite element modeling of dinsar and gps measurements and geological seismological data the l aquila italy 2009 earthquake case study

rupture history of the 2009 l aquila italy earthquake from non linear joint inversion of strong motion and gps data 1 we image the rupture history of the 2009 l aquila central italy earthquake using a nonlinear joint inversion of strong motion and gps data this earthquake ruptured a normal fault striking along the apennines axis and dipping to the sw the inferred slip distribution is heterogeneous and characterized by a small shallow slip patch located up dip from the hypocenter 9 5 km depth and a large deeper patch located southeastward the rupture velocity is larger in the up dip than in the along strike direction this difference can be partially accounted by the crustal structure which is characterized by a high velocity layer above the hypocenter and a lower velocity below the latter velocity seems to have affected the along strike propagation since the largest slip patch is located at depths between 9 and 14 km the imaged slip distribution correlates well with the on fault aftershock pattern as well as with mapped surface breakages

joint inversion of coseismic and early postseismic slip to optimize the information content in geodetic data application to the 2009 m w 6 3 l aquila earthquake central italy when analyzing the rupture of a large earthquake geodetic data are often critical these data are generally characterized by either a good temporal or a good spatial resolution but rarely both as a consequence many studies analyze the coseismic rupture with data that also include one or more days of early postseismic deformation here we invert simultaneously for the coseismic and postseismic slip with the condition that the sum of the two models remains compatible with data covering the two slip episodes we validate the benefits of this approach with a toy model and an application to the 2009 m w 6 3 l aquila earthquake using a bayesian approach and accounting for epistemic uncertainties for the l aquila earthquake we find that if early postseismic deformation is not an explicitly acknowledged coseismic signal coseismic slip models may overestimate the peak amplitude while long term postseismic models may largely underestimate the total postseismic slip amplitude this example illustrates how the proposed approach could improve our comprehension of the seismic cycle fault frictional properties and the spatial and temporal relationship between seismic rupture afterslip and aftershocks

the cryogenian record of glaciation and deglaciation in south australia abstract this paper reviews the state of our current knowledge of the cryogenian glacial and deglacial sedimentary records of south australia two distinct glacial intervals are recognised within rocks of cryogenian 850 630 ma age separated by an interglacial succession that by definition lacks glacial facies the glacial successions were laid down during the sturt and elatina glaciations each of these glaciations is arguably of global extent under the snowball earth hypothesis hoffman and schrag 2002 evidence for glaciation has been known for over one hundred years from the sturt tillite howchin 1900 when compared like for like in a systematic facies analysis both glacial successions show some similarities notably the occurrence of diamictites representing glacial deposition and slope reflux and dropstone bearing intervals but also show some dramatic differences notably deposition of the sturt succession was strongly influenced by extensional tectonics for which evidence is provided by dramatic thickness variations either side of major faults and palaeocurrent data sub basins formed during regional extension contain diamictites 4 6000 m thick e g the yudnamutana and baratta troughs in the northern and central flinders ranges respectively deposition of the younger elatina glacial deposits was locally influenced by diapirism in the central flinders ranges but otherwise these younger deposits seem to maintain a relatively constant thickness of

coseismic and initial post seismic slip of the 2009 mw 6 3 l aquila earthquake italy from gps measurements summary here we report the preliminary results of gps data inversions for coseismic and initial afterslip distributions of the mw 6 3 2009 april 6 l aquila earthquake coseismic displacements of continuous and survey style gps sites show that the earthquake ruptured a planar sw dipping normal fault with 0 6 m average slip and an estimated moment of 3 9 1018 nm geodetic data agree with the seismological and geological information pointing out the paganica fault as the causative structure of the main shock the position of the hypocentre relative to the coseismic slip distribution supports the seismological evidence of southeastward rupture directivity these results also point out that the main coseismic asperity probably ended downdip of the paganica village at a depth of few kilometres in agreement with the small 1 10 cm observed surface breaks time dependent post seismic displacements have been modelled with an exponential function the average value of the estimated characteristic times for near field sites in the hanging wall of the fault is 23 9 5 4 d the comparison between coseismic slip and post seismic displacements for the first 60 d after the main shock shows that afterslip occurred at the edges of the main coseismic asperity with a maximum estimated slip of 25 cm and an equivalent seismic moment of 6 5 1017 nm the activation of the paganica fault spatially intermediate between the previously recognized main active fault systems suggests that strain accumulation in the central apennines may be simultaneously active on distinct parallel fault systems

basement cover interaction in the adelaide foldbelt south australia the development of an arcuate foldbelt abstract the upper proterozoic to cambrian aged sedimentary and volcanic rocks comprising the adelaide foldbelt were deformed and in places metamorphosed during the cambro ordovician delamerian orogeny tectonic fabrics developed in the central portion of the foldbelt mt lofty ranges demonstrate westward transport during the orogeny the sigmoidal shape outlined by the kangaroo is mt lofty ranges olary portion of the foldbelt is interpreted to have been the result of dextral wrench faulting in the lower to mid proterozoic basement thus cover rocks overlying such basement wrench fault zones would have suffered a transpressional stress regime giving rise to the observed fold axis oriented at an oblique angle to the thrust boundary in the northern portion of the foldbelt northern flinders ranges wrench faulting is interpreted to have accommodated considerable basement shortening which initiated a basement cover decollement and resulted in thrust bound pop up structures in the cover

physical modeling of sedimentation adjacent to diapirs and comparison with late precambrian oratunga breccia body in central flinders ranges south australia the interaction of sedimentation with the change in shape of a developing diapir is modeled in a series of simple sandbox experiments this model replicates the pillow diapir and postdiapir stages of salt movement modeling produced rim synclines crestal unconformities and turtle structure anticlines all features known to be associated with diapirs by changing experimental parameters such as diapir shape sedimentation was simulated around various diapiric situations one experiment closely matches the sediment distribution around the oratunga diapir one of the controversial breccia bodies in the late precambrian cambrian adelaide geosyncline exposed in the flinders ranges of south australia rim synclines unconformities and bedding attitude around oratunga resemble those described around salt domes in addition the distribution size orientation and lithology of breccia within the oratunga diapir resemble breccia associated with active salt diapirs in iran these data suggest the breccia was emplaced as a salt diapir

surface faulting of the 6 april 2009 mw 6 3 l aquila earthquake in central italy this paper documents evidence of surface faulting associated with the 6 april 2009 moderate sized earthquake ml 5 8 mw 6 3 in the central apennines of italy which caused major damage to the town of l aquila and its surroundings coseismic surface ruptures were mapped for a minimum distance of 2 6 km along the paganica fault a fault still poorly investigated relative to the other active faults nearby which bound much wider range fronts surface rupture length srl and maximum displacement parameters 2 6 km minimum and 10 15 cm respectively are in agreement with what is expected for an mw 6 3 event in the italian apennines tectonic environment different viewpoints exist on the amount of srl and the number of activated faults we propose a pattern of sympathetic and secondary slip on an array of faults around the master seismogenic structure past seismicity and evidence for larger holocene offsets on this and other capable faults nearby prove that the 2009 event is not a good reference event for assessing the seismic hazard of the region nevertheless the 2009 l aquila earthquake once more confirmed the importance of detailed geological studies for a proper seismic hazard assessment and it clearly illustrates the need to pay attention to moderate events and supposedly minor active faults indeed this type of earthquake is rather frequent in the whole mediterranean region and is potentially much more destructive than in the past due to the expanding urban centers and infrastructures inside their epicentral regions and even right above the traces of capable faults

the elatina glaciation late cryogenian marinoan epoch south australia sedimentary facies and palaeoenvironments abstract the late cryogenian elatina glaciation in south australia of marinoan age is named after the elatina formation of the glaciogenic yerelina subgroup which covers 200 000 km2 in the adelaide geosyncline and on the cratonic stuart shelf and is up to 1500 m thick the elatina glaciation is marked by numerous facies that are like those of phanerozoic glaciations basal diamictite displaying glacitectonites with penetrative deformation of preglacial beds indicating grounded ice or scouring by icebergs glaciomarine diamictites containing numerous faceted and striated clasts up to several metres across of intrabasinal and extrabasinal origin laminated siltstone and mudstone containing scattered ice rafted dropstones in outer marine shelf environments sandstones deposited in fluvial deltaic and inner marine shelf settings tidalites deposited in estuaries and on tidal deltas during interstadial rise of sea level with cyclic tidal rhythmites recording the annual oscillation of sea level and displaying wave generated ripple marks which together indicate long lived and extensive open seas siltstone containing acicular crystal pseudomorphs implying the formation of evaporite minerals in littoral deposits permafrost regolith of frost shattered quartzite breccia 20 m deep displaying large scale periglacial structures including primary sand wedges 3 m deep that indicate a frigid strongly seasonal climate near sea level periglacial aeolian sandstone covering 25 000 km2 and containing primary sand wedges near its base these deposits record a spectrum of settings ranging from permafrost regolith and periglacial sand sheet on the stuart shelf in the west through fluvial deltaic and inner marine shelf in the western and central parts of the adelaide geosyncline to outer marine shelf in the north and southeast the widespread and persistent rainout of fine grained sediment and ice rafted debris indicates that the sea was not frozen over during the elatina glaciation no direct age determination is available for the elatina glaciation and only maximum and minimum age limits of 640 and 580 ma respectively can at present be applied high quality palaeomagnetic data for red beds from the elatina formation supported by positive fold tests on soft sediment slump folds that demonstrate the early acquisition of magnetic remanence indicate deposition within 10 of the palaeoequator the yerelina subgroup in the adelaide geosyncline and on the stuart shelf is disconformably to unconformably overlain by the nuccaleena formation cap carbonate that marks the early ediacaran post glacial marine transgression the presence in near equatorial palaeolatitudes of glaciomarine deposition grounded ice and permafrost near sea level a strongly seasonal periglacial climate and widespread open seas implies a paradoxical palaeoclimate and palaeogeographic setting for the elatina glaciation the strong evidence for a non actualistic late cryogenian glacial climate in south australia has been a stimulus to worldwide multidisciplinary research on cryogenian glaciogenic successions

inversion of strong ground motion and teleseismic waveform data for the fault rupture history of the 1979 imperial valley california earthquake a least squares point by point inversion of strong ground motion and teleseismic body waves is used to infer the fault rupture history of the 1979 imperial valley california earthquake the imperial fault is represented by a plane embedded in a half space where the elastic properties vary with depth the inversion yields both the spatial and temporal variations in dislocation on the fault plane for both right lateral strike slip and normal dip slip components of motion inversions are run for different fault dips and for both constant and variable rupture velocity models effects of different data sets are also investigated inversions are compared which use the strong ground motions alone the teleseismic body waves alone and simultaneously the strong ground motion and teleseismic records the inversions are stabilized by adding both smoothing and positivity constraints the moment is estimated to be 5 0 10 25 dyne cm and the fault dip 90 5 dislocation in the hypocentral region south of the united states mexican border is relatively small and almost dies out near the border dislocation then increases sharply north of the border to a maximum of about 2 m under interstate 8 dipslip motion is minor compared to strike slip motion and is concentrated in the sediments the best fitting constant rupture velocity is 80 per cent of the local shear wave velocity however there is a suggestion that the rupture front accelerated from the hypocenter northward the 1979 imperial valley earthquake can be characterized as a magnitude 5 earthquake at the hypocenter which then grew into or triggered a magnitude 6 earthquake north of the border

the 2009 l aquila earthquake central italy a source mechanism and implications for seismic hazard an edited version of this paper was published by agu copyright 2009 american geophysical union

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

physical modelling of overburden deformation around salt diapirs abstract salt diapirs produce highly complex deformation patterns in the surrounding overburden which are difficult to image seismically or model numerically to further the understanding of deformation around salt structures we have used physical models with brittle granular overburdens and simulated sedimentation accompanying diapiric rise rigid linear indentors produce a crestal horst above the indentor with two flanking graben large amounts of indentation produce predominantly reverse faults along the margins of the diapir and extensional faults over the crest in contrast hemispherical indentors produced inward dipping concentric reverse faults forefully intruded polymer diapirs produce a narrow crestal graben above the diapir crest downbuilt polymer diapirs produce extensional faults on the flanks of the diapirs which offset the diapir walls no clear secondary rim synclines were developed as polymer is withdrawn evenly from the whole of the polymer layer across the model strong and anisotropic layered overburden were simulated using cohesive clay and mica respectively detachments were formed along mica layers which suppressed faults with large throws cohesive layer deformation began with tensile fractures permitting rotation of fractured rafts around the sides of the diapir these progressively slip off the crest and create large gaps in the stratigraphy

radiography of a normal fault system by 64 000 high precision earthquake locations the 2009 l aquila central italy case study 1 we studied the anatomy of the fault system where the 2009 l aquila earthquake mw 6 1 nucleated by means of 64 k high precision earthquake locations spanning 1 year data were analyzed by combining an automatic picking procedure for p and s waves together with cross correlation and double difference location methods reaching a completeness magnitude for the catalogue equal to 0 7 including 425 clusters of similar earthquakes the fault system is composed by two major faults the high angle l aquila fault and the listric campotosto fault both located in the first 10 km of the upper crust we detect an extraordinary degree of detail in the anatomy of the single fault segments resembling the degree of complexity observed by field geologists on fault outcrops we observe multiple antithetic and synthetic fault segments tens of meters long in both the hanging wall and footwall along with bends and cross fault intersections along the main fault and fault splays the width of the l aquila fault zone varies along strike from 0 3 km where the fault exhibits the simplest geometry and experienced peaks in the slip distribution up to 1 5 km at the fault tips with an increase in the geometrical complexity these characteristics similar to damage zone properties of natural faults underline the key role of aftershocks in fault growth and co seismic rupture propagation processes additionally we interpret the persistent nucleation of similar events at the seismicity cutoff depth as the presence of a rheological i e creeping discontinuity explaining how normal faults detach at depth