the detection of low magnitude seismic events using array based waveform correlation summary it has long been accepted that occurrences of a known signal are most effectively detected by cross correlating the incoming data stream with a waveform template such matched signal detectors have received very little attention in the field of detection seismology because there are relatively few instances in which the form of an anticipated seismic signal is known a priori repeating events in highly confined geographical regions have been observed to produce very similar waveforms and good signals from events at a given site can be exploited to detect subsequent co located events at lower magnitudes than would be possible using traditional power detectors even greater improvement in signal detectability can be achieved using seismic arrays running correlation coefficients from single sensors can be stacked over an array or network to result in a network correlation coefficient displaying a significant array gain if two events are co located the time separating the corresponding patterns in the wave train as indicated by the cross correlation function is identical for all seismic stations and this property means that the correlation coefficient traces are coherent even when the waveforms are not we illustrate the power of array based waveform correlation using the 1997 august 16 kara sea event the weak event that occurred 4 hr after the main event was barely detected using an sta lta detector on the spits array but is readily detected by signal matching on a single channel the main event was also recorded by the far more distant norsar array but no conventional detection can be made for the second event a clear detection is however made when the correlation coefficient traces are beamformed over all sensors of the array we estimate the reduction in detection threshold of a test signal on a regional seismic array using waveform correlation by scaling down a master signal and immersing it into seismic noise we show that for this case waveform correlation using a single channel detects signals of approximately 0 7 orders of magnitude lower than is possible using an sta lta detector on the array beam waveform matching on the full array provides an additional improvement of approximately 0 4 magnitude units we describe a case study in which small seismic events at the barentsburg coal mine on spitsbergen were detected using the signals from a major rockburst as master waveforms many spurious triggers occurred in this study whereby short sections of signal exhibited coincidental similarity with unrelated incoming wave fronts we demonstrate how such false alarms can almost always be identified and screened out automatically by performing frequency wavenumber analysis upon the set of individual correlation coefficient traces

a geodynamic model of the southern apennines accretionary prism the apennines comprise a neogen quaternary accretionary prism that shows several anomalies with respect to classic alpine type mountain belts namely i low elevation ii a shallow new moho below the core of the belt iii high heat flow in the internal parts iv mainly sedimentary cover involved in the prism v a deep foredeep and vi a fully developed back arc basin the suction exerted by a relatively eastward migrating mantle can determine the eastward retreat of the subduction zone and an asthenospheric wedging at the retreating subduction hinge heat flow geochemical and seismological data support the presence of a hot mantle wedge underlying the western side of the apenninic accretionary prism a thermal model of the belt with foreland dipping isotherms fits with deepening of the seismicity toward the east mantle volatiles signatures are also widespread in springs along the apennines

geologic structure and neotectonics of the north african continental margin south of sicily abstract marine geological and geophysical data together with drilling information indicate that the north african passive continental margin has been subjected to extension and wrenching after it collided with the northern part of sicily the area of the tripolitania basin jarrafa trough melita and medina bank and the ragusa malta plateau has formed part of a sinking passive margin since the dispersal of gondwanaland at about 180 my ago as observed from geohistory diagrams a record of rifting in a nw se direction accompanied by dextral shear along the southern troughs is observed in seismic reflection data the rifting started during the neocomian and lasted until the eocene when activity became minor a pre middle miocene period of northward subduction of oceanic crust is inferred from the geology in ne sicily uplift of the northern part of the african margin after collision in the middle miocene is seen in wells in southern sicily after the messinian a rift and dextral shear zone established itself across the african margin from the strait of sicily to the medina ridge in the lonian basin the zone is marked by up to 1 7 km deep grabens narrow active wrench faulted channels volcanic fissures and local uplifted keilhorsts such as malta this zone which varies in width from 100 to 35 km forms the southern boundary of a microplate which includes sicily we speculate that the present motion of this microplate is partly due to the eastward movement of the calabrian arc with the sicilian block over the last remaining oceanic lithosphere in the eastern mediterranean

hyperconcentrated flows on a forested alluvial fan of eastern canada geomorphic characteristics return period and triggering scenarios the assessment of the dominant flow type on alluvial fans usually refers to two categories debris flow fans i e sediment gravity flows and fluvial fans i e fluid gravity flows here we report the results of combined morphometric stratigraphic and sedimentological approaches which suggest that hyperconcentrated flows a transitional process rheologically distinct from debris flows and floods and sometimes referred to as debris floods mud floods or transitional debris flows are the dominant fan building process in eastern canada these flows produce transitional facies between those of debris flows which consist of a cohesive matrix supported diamicton and those of river flows which display more distinct stratification the size of the blocks in the channels and the abrasion scars at the base of several trees attest to the high transport capacity of these flows the fan channels are routed according to various obstacles comprised primarily of woody debris that impede sediment transit however these conditions of sediment storage are combined with readily available sediment due to the friable nature of the local lithology tree ring analysis allowed the reconstruction of eight hydrogeomorphic events which are characterized by a return period of 9 25 years for the period 1934 2008 although most of the analyzed events occurred after 1970 historical weather data analysis indicates that they were related to rare hydrometeorological events at regional and local scales this evidence led to the elaboration of weather scenarios likely responsible for triggering flows on the fan according to these scenarios two distinct hydrologic regimes emerge the torrential rainfall regime and the nival regime related to snowmelt processes hydrogeomorphic processes occurring in a cold temperate climate and particularly on small forested alluvial fans of north eastern north america should receive more attention from land managers given the hazard they represent as well as because of their sensitivity to various meteorological parameters copyright 2014 john wiley sons ltd

imaging fractures and sedimentary fabrics using shear wave splitting measurements made on passive seismic data summary the ability to detect aligned fractures using seismic anisotropy provides a valuable tool for exploiting hydrocarbon reservoirs better perhaps the most direct way of identifying anisotropy is by observing shear wave splitting however the interaction of shear waves with subsurface structure is often complicated although fractures in hydrocarbon reservoirs are usually subvertical shear waves recorded on downhole receivers from microseismic events in or near the reservoir are not likely to have travelled vertically as such interpreting splitting measurements made on such waves is a non trivial problem here we develop an approach to model the effects of subsurface structure on non vertically propagating shear waves rock physics theory is used to model the effects of sedimentary fabrics as well as fractures allowing us to use shear wave splitting measurements to invert for aligned fractures we use synthetic examples to demonstrate how it is possible to assess in advance how well splitting measurements will image structures and how this is highly dependent on the available range of ray coverage finally we demonstrate the inversion technique on a passive seismic data set collected during hydraulic fracture stimulation despite an unfavourable source receiver geometry the strike of an aligned fracture set is accurately identified

lateral interaction between metamorphic core complexes and less extended tilt block domains the alpujarras strike slip transfer fault zone betics se spain abstract the alpujarras area in southeastern spain exhibits one of the scant documented examples of extension related strike slip faults bordering core complexes in the world faults of the alpujarras fault zone define a regional scale complex ene striking transfer zone that marks the boundary among the sierra nevada elongated dome a highly extended constricted core complex and a less extended domain formed by large scale tilt blocks detailed mapping and structural analysis show that the alpujarras fault zone is an integral part of the wsw directed normal fault systems that thinned the betic hinterland during the middle miocene to recent time fault patterns and palaeostress analysis both indicate that dextral movement along the strike slip faults was induced by a local stress field with a sub horizontal e w to ese wnw trending maximum principal stress axis which is synchronous with the regional stress field driving the normal fault systems palaeostress analysis also indicates subsequent variations in the stress field with a sub horizontal nw se to n s trending maximum principal stress axis thus producing both the tectonic inversion of the northern fault of the alpujarras system and shortening of the unloaded extensional detachment footwall a simplified kinematic model for the tectonic evolution of the alpujarras area from the middle miocene to recent emphasizes the kinematic coupling of normal faults and strike slip transfer zones in the extensional process

neogene patterns of relative plate motion for africa europe some implications for recent central mediterranean tectonics a detailed relative motion picture for the neogene africa europe plate kinematics is presented the kinematic reconstruction was carried out using the finite difference solution between the rotation parameters determined for anomalies 7 to 2 in the africa north america europe plate motion circuit the analysis shows a motion of africa with respect to europe which is nne directed during late oligocene to burdigalian times becoming nnw trending from the langhian to the early tortonian from upper tortonian times onward the motion changes to a clear north west directed convergence major late neogene tectonic features of the central mediterranean region can to a large extent be explained within the context of the reconstructed major plate motions late tortonian to recent africa europe slip vectors are compatible with a variety of geological phenomenoa such as north west directed subduction beneath calabria south east translation of calabria and extension in the tyrrhenian sea north west trending slip vectors from thrust earthquakes between gibraltar and sicily and dextral strike slip across the north african margin

geodynamic evolution of the lithosphere and upper mantle beneath the alboran region of the western mediterranean constraints from travel time tomography an edited version of this paper was published by the american geophysical union copyright 2000 agu see also http www agu org pubs crossref 2000 2000jb900024 shtml http atlas geo cornell edu morocco publications calvert2000 htm

the argille varicolori unit in lucania italy a record of tectonic offscraping and gravity sliding in the mesozoic tertiary lagonegro basin southern apennines

geological relationships and u pb zircon and 40 ar 39ar tourmaline geochronology of gneisses and tourmalinites from the nevado filabride complex western sierra nevada spain tectonic implications abstract the nevado filabride complex the lowest complex in the betic hinterland forms a stack of alpine nappes the tectonic units consist of metasedimentary sequences whose ages are not well constrained gneiss bodies included in the sequences have been one of the few sources of geochronological data in this metamorphic complex new radiometric data from u pb zircon dating on gneisses from the western sierra nevada confirm the presence of late carboniferous intrusive rocks in the betic hinterland these results combined with available data from the literature and a detailed structural analysis suggest that the gneisses represent a single late variscan magmatic event evidence for a close genetic relation between gneisses and tourmalinites is provided by field and petrographic observations in conjunction with geochemical data u pb zircon 314 7 304 23 ma and 40 ar 39 ar tourmaline 319 85 5 81 317 85 3 67 ma geochronology a pre late carboniferous age for the basal formation of the nevado filabride sequence can be inferred the gneiss protolith and the graphite schist are considered to be the boron source and the precursor of the tourmalinites respectively superposed tectonic units rather than a continuous palaeozoic sequence is supported by the occurrence of palaeozoic rocks at the top of the nevado filabride complex the nappe tectonics as evidenced from the contractional character of the unit boundaries and the superposition of higher grade on lower grade metamorphic rocks is additionally supported by the superposition of older on younger rocks as revealed from radiometric data

sedimentation in the northern apennines corsica tectonic knot northern tyrrhenian sea central mediterranean offshore drilling data from the elba pianosa ridge the northern tyrrhenian sea is located on the collisional zone between the alpine corsica and the northern apennines and is a key area for gaining a better understanding of the complex relationships between these two systems the knowledge of the wide offshore part of this zone located between corsica france and mainland italy is based primarily on the analysis of several seismic profiles tied to the outcropping geology and unpublished preliminary reports of few offshore wells the here presented study of two offshore wells provides a revision of the sedimentology biostratigraphy and petrography of the thick mainly siliciclastic tertiary successions about 3 600 m composing the elba pianosa ridge epr a structural morphological high separating the tuscan shelf to the east from the corsica basin to the west a comparison with similar deposits cropping out in the surrounding onshore areas northern apennines corsica tuscan archipelago piedmont tertiary basin provides additional constraints for refinement of the complex geodynamic and regional setting in which the epr evolved

channel avulsion on alluvial fans in southern arizona historical aerial photographs and field observations on five fluvially dominated alluvial fans in southern arizona demonstrate that channel avulsion invariably occurs where bank heights are low and often at channel bends channel abandonment occurs through stream capture when overland flow from the main channel accelerates and directs headward erosion of smaller channels heading on the fan surface five distinct channel morphologies observed on the fans are related to different stages of the avulsion process and can be used to identify areas on a fan surface that are prone to avulsion a descriptive model of channel avulsion illustrates how the morphology of a single channel reach will evolve through time as it captures the main flow path and is itself eventually abandoned immediately following avulsions small preexisting channels that capture flow from the main channel will typically experience three fold or greater increases in channel width subsequent large floods can be stably conveyed through these high capacity reaches an uninterrupted sequence of sediment charged small flows however will eventually begin to back fill the wide channels as vegetation growth stabilizes the banks the stabilized and back filled channels are now prone to abandonment during large floods because the decrease in the channel s capacity leads to the generation of overland flow beyond the margins of the shallowed channels the action of the small aggrading floods is critical in the avulsion process since the greatest amount of overland flow is generated where bank heights are lowest as a result both small and large floods are effective agents of landscape change on the fans channel avulsions on the five fans are not completely random events in space and time because their occurrence is controlled by the relative positioning of low banks along the main channel and smaller channels draining the fan surface consequently the location and timing of future channel avulsions can potentially be anticipated in an effort to improve flood hazard assessment on fluvial fans in the rapidly urbanizing southwestern united states

structural and petrological analyses of the frido unit southern italy new insights into the early tectonic evolution of the southern apennines calabrian arc system abstract this study provides new data on the deformation and metamorphic evolution of the jurassic to upper oligocene frido unit an ocean continent transition oct unit belonging to the ligurian accretionary complex lac by means of the integration of structural analysis petrological investigations and a revision of the stratigraphical setting the frido unit representing the main metamorphic component of the lower middle miocene lac in southern italy is characterized by a multistage tectonic evolution including i two progressive deformation phases involving the development under relatively high pressure metamorphic conditions of an early cleavage associated with isoclinal folds within the framework of a dominant se ward tectonic transport ii a third deformation stage involving the growth of lower pressure na amphibole along extensional shear surfaces therefore probably marking the onset of tectonic exhumation and iii two very low temperature deformation phases characterized by the development of kink folds and associated thrusts probably related to the late tectonic emplacement of the accretionary wedge onto the outer sectors of the apennine domain with a prevailing tectonic transport first toward the ne and then toward the nw in order to clarify the metamorphic evolution of the frido unit petrologic analyses were focused on its metasedimentary pelitic succession here mineral parageneses including carpholite well documented for the first time in this study and potassic white mica yielded peak pressure of 1 2 1 4 gpa and temperature around 350 c thus indicating a high pressure very low temperature metamorphism and a p t t path characterized by a rapid exhumation without any greenschist facies overprint in comparison with similar units cropping out in northern calabria tuscany and corsica the frido unit experienced one of the coldest burial exhumation histories

inferring rock fracture evolution during reservoir stimulation from seismic anisotropy we have analyzed seismic anisotropy using shear wavesplitting measurements made on microseismic events recorded during a hydraulic fracture experiment in a tight gas reservoir in carthage east texas microseismic events were recorded on two downhole arrays of three component sensors the geometry of which provided good ray coverage for anisotropy analysis a total of 16 633 seismograms from 888 located events yielded 1545 well constrained shear wave splitting measurements manual analysis of splitting from a subset of this data set reveals temporal changes in splitting during fracturing inversion using the full data set allows the identification of fracture strike and density which is observed to vary during fracturing the recovered fracture strike in the rock mass is parallel to directions of regional borehole breakout but oblique to the hydraulic fracture corridor as mapped by the microseismic event we relate this to en echelon fracturing of preexisting cracks the magnitude of shear wave splitting shows a clear temporal increase during each pumping stage indicating the generation of cracks and fissures in a halo around the fracture corridor which thus increase the overall permeability of the rock mass our results show that shear wave splitting analysis can provide a useful tool for monitoring spatial and temporal variations in fracture networks generated by hydraulic stimulation

modes and timing of fracture network development in poly deformed carbonate reservoir analogues mt chianello southern italy abstract structural and paleostress analyses carried out on a kilometre sized outcrop of allochthonous shallow water carbonate units of the southern apennines allowed us to unravel a superposed deformation pattern associated with plate convergence the reconstructed tectonic evolution involves i early extensional faulting and fracturing associated with bending of the foreland lithosphere during forebulge and foredeep stages including the development of both tangential and radial normal fault and tensile fractures early middle miocene ii large scale thrusting and folding late miocene iii transcurrent faulting including two distinct sub stages characterized by different remote stress fields pliocene early pleistocene and iv extensional faulting late quaternary stage i normal faults generally occurring as conjugate sets and related fractures and veins are variably deformed and overprinted by later horizontal shortening despite having experienced such a long and complex structural history the studied carbonates are characterized by a background fracture network including two joint vein sets orthogonal to each other and to bedding that appears to be associated with the early fault sets that formed during the first foredeep forebulge related deformation stage therefore away from younger late miocene to quaternary fault zones the permeability structure of the studied carbonates appears to be essentially controlled by the early inherited fracture network as a similar fracture network is likely to characterize also the buried apulian platform carbonates representing the reservoir units for major oil fields in southern italy our results also bear possible implications for a better understanding of fluid flow in the subsurface and related hydrocarbon production

the okavango fan and the classification of subaerial fan systems abstract controversy exists over the classification of fluvially formed subaerial fans authors either restrict alluvial fans to debris flow dominated types or extend the spectrum to fans dominated by braided rivers the okavango fan provides an end member which extends this spectrum to fans dominated by meandering and low sinuosity rivers the fan is a large 150 km radial axis shallowly sloping 0 00036 highly vegetated subaerial fan which can be subdivided into four subenvironments these are 1 the entry corridor or panhandle characterized by single and anastomosing meander belts 2 the upper fan characterized by meander belts diverging from the fan apex comprising peat confined meandering channels with interchannel swamps forming thick peats 3 the middle fan with highly confined single and anastomosing low sinuosity rivers and less common prograding meander belts whose channels are confined by thick peats with however little chance of peat preservation and 4 the lower fan in which annual floods from relatively unconfined channels spread over the fan surface and interact with pre existing aeolian and lacustrine deposits with the recognition of this new fan type the spectrum of subaerial fan types can be expressed in terms of 1 debris flow dominated fans of which the death valley fans are a member 2 braided river dominated fans of which the kosi fan is a member and 3 low sinuosity meandering losimean river dominated fans of which the okavango fan is a member this spectrum can be expressed in terms of variation in slope maximum size and percentage of surface vegetation but crucial to the evolution of the various fan types is variation in the flashy to continuous nature of the discharge and the degree of channel confinement evident on the fan surface comparable ancient examples of the three fan types are recognizable many of which provide intermediates between the ideal end members debris flow dominated and braid dominated fan types are known from throughout earth history however the losimean fan type because of its reliance on confining vegetation may only have developed after the devonian period the spectrum of subaerial fan types can be expressed on a triangular field of variation with the vertices defined by the relative importance of the processes which shaped a particular fan system be they debris flows processes associated with braided rivers or processes associated with meandering and low sinuosity rivers

low angle normal faulting and focused exhumation associated with late pliocene change in tectonic style in the southern apennines italy in the southern apennines low temperature thermochronometry data indicate that exhumation of previous tectonically buried sedimentary units started at around 10 ma and took place mostly during the last 6 ma relatively high exhumation rates are obtained from apatite fission track aft and u th he ahe analysis pointing to a substantial contribution of tectonic processes to rock exhumation besides erosion exhumation rates derived from new apatite u th he data ahe for the last 3 ma are generally lower than rates determined by aft data and almost in line with erosion rates inferred from cosmogenic nuclides and sediment yield thus suggesting that tectonic exhumation was dominant during the older exhumation stages of this region however younger cooling ages in the monte alpi area from both aft and ahe analyses point out focused exhumation during the last 3 ma structural and morphotectonic analyses indicate that fast exhumation occurred specifically in this area where the apulian platform reservoir carbonates elsewhere buried beneath a several kilometer thick allochthonous cover are exposed at the surface as a result of a complex interplay between steep rooted reverse faulting and shallow low angle extension this deformation involved the development of foreland dipping low angle normal faults affecting the allochthonous cover units during the late stages of reverse fault related anticlinal growth in the underlying buried carbonates extension of the region triggered focused exhumation in the footwall of the extensional low angle faults which was followed by widespread crustal extension and associated development of high angle normal faults leading to surface uplift of monte alpi

a method to assess fluvial fan channel networks with a preliminary application to fans in coastal british columbia abstract the channel network on a fluvial fan distributes sediment across the fan surface and determines fan development we present a method to characterize fan channel networks fcns so that the effect of controls e g sediment supply on the fcn can be evaluated we then do a preliminary test of the method using three fans in coastal british columbia the method uses a set of three measures 1 the spatial extent of hydrogeomorphic activity measured as the percentage of the contemporary fan surface area occupied by active channels 2 the topologic structure using node counts to measure channel network complexity and 3 a sediment budget to indicate the proportion of sediment that is stored on the fan loosely characterized by comparing the second largest clast size of sediment at the fan apex or intersection point with the second largest clast at the toe of the fan these measures were applied to two fan deltas and one partial fan delta in northern vancouver island british columbia using channel surveys conducted in 2006 and 2007 all three fans are located within 30 km of each other have similar climatic physiographic and vegetation settings and have natural channel networks each fan has perennial channel flow at the fan apex watershed areas range from 19 5 to 35 6 km2 and contemporary fan areas range from 0 2 to 0 7 km2 the melton relative relief ratio ranges from 0 24 to 0 30 and none of the fans show evidence of debris floods or debris flows in addition to testing the efficacy of the fcn measures we use these fans to explore the question of whether fans in similar geomorphic settings and with similar controls develop similar fcns results show the fans have between 4 7 8 5 of the contemporary fan surface occupied by the active channel network topologic node counts indicate that the two fan deltas have a similar level of channel complexity with 42 54 nodes in total the partial fan delta channel network is approximately half as complex with 23 nodes in total all three fans have boulder sized sediment 30 50 cm at the fan apex on the two fan deltas the largest sediment at the toe of the fan is 10 12 cm indicating that much of the sediment delivered to the fan apex is stored on the fan in contrast the partial fan delta has 18 20 cm sized sediment transported into the axial valley river at the toe of the fan and a wider and steeper outlet channel indicating that a greater proportion of sediment is exported from the fan although the axial river does not visibly incise into the fan deposits the lower channel complexity and coarser sediment output indicates that the axial river truncates the toe of the partial fan delta the two fan deltas have similar fcns supporting the idea that fans in similar geomorphic settings develop similar fcns the partial fan delta is in a different geomorphic setting that was not identified prior to analysis of the fcns and has a different fcn this study also examines the effects of a large regional storm event that occurred between the 2006 and 2007 surveys one fan had increased active area two fans had increased total node counts and two fans increased output clast size after the flood event indicating the measures are sensitive and respond to disturbance further investigations of fcns may have utility in hazard assessments addressing how fans respond to changes in sediment supply or discharge regime how vegetation type affects fcns or the effect of other watershed processes or fan attributes

magnitudes of induced earthquakes and geometric scales of fluid stimulated rock volumes sometimes rock stimulations by fluid injections into geothermal boreholes are able to trigger perceptible or even potentially damaging earthquakes this does not seem to be the case for hydraulic fracturing of hydrocarbon reservoirs reasons for such a difference and factors defining magnitudes of induced earthquakes triggered tectonicly as well as induced artificially remain unclear we analyzed microseismic data obtained by fluid stimulations at different geothermal and hydrocarbon sites this analysis indicates that a rupture corresponding to a fluid induced earthquake seems to be only probable along a surface located mainly inside a stimulated rock volume we approximated the stimulated volume by an ellipsoid and compared the statistics of induced events with the statistics of randomly distributed thin flat disks modeling rupture surfaces we found that one of the main factors limiting the probability to induce a large magnitude event is the minimum principal axis of a fluid stimulated rock volume

the calabrian arc and the ionian sea in the dynamic evolution of the central mediterranean in the central mediterranean area it is possible to recognize three main realms the tyrrhenian sea the pelagian block and the ionian block these domains are limited by important fracture zones that are easily recognizable on land and offshore these fracture zones can be grouped into four main trends 1 the nw se trend which is characterized by dextral horizontal movements 2 the ne sw trend which is generally characterized by sinistral lateral horizontal movements 3 the e w trend which also shows dextral shear movements and 4 the n s trend which is characterized by normal faults only the tyrrhenian sea realm is characterized by a thinned crust of oceanic type and is connected to the apenninic chain by means of listric faults from a geophysical point of view the area shows a high heat flow which follows the main structural trends and positive gravimetric anomalies which are compatible with seismic refraction data and can be explained by the proposed model the pelagian block shows a continental crust about 20 km thick which progressively increases beneath the sicilian chain here an abrupt interruption with the tyrrhenian block takes place in the pelagian realm rifting processes developed according to the nw se and n s trend the n s trend characterizes the westernmost zone of the realm where volcanic processes and a relatively high heat flow can also be observed the ionian block is characterized by the following a thinned crust 17 20 km which increases 40 km towards the southern calabrian chain a thick sedimentary sequence high positive bouguer anomalies 300 mgal and very low heat flow 50 mw m 2 geophysical and structural analyses allowed us to evaluate the post tortonian evolution of the whole area under consideration this evolution resulted in continental crust formation according to a rigid plastic deformation model according to our model the ionian block can be considered as a domain characterized by a thinned continental crust and affected by intrusive material derived from the upper mantle furthermore this domain of probably jurassic age can be considered as a pelagic basin bordered by the pelagian block to the west and by the apulian block to the east northeast this basin according to its position with respect to the apenninic and sicilian chains has not been affected by tectogenesis and still represents a site of continuous sedimentation from a kinematic point of view the ionian realm can be linked with the pelagian block shifting towards the east northeast whereas it is limited towards the north by an e w fracture zone which regulates the opening of the tyrrhenian sea and the counterclockwise rotation of the apenninic chain according to the proposed model the opening of the tyrrhenian sea can be considered as a megaextension fracture which developed parallel to the maximum principal stress direction and evolved as a triangular shaped structural feature in preparing the model the authors have taken into account a large set of data collected both on land and offshore

tectonic burial and young 10 ma exhumation in the southern apennines fold and thrust belt italy in the southern apennines fold and thrust belt thermal indicators record exhumation of sedimentary units from depths locally in excess of 5 km the thrust belt is made of allochthonous sedimentary units that overlie a 6 8 km thick carbonate footwall succession the latter continuous with the foreland apulian platform is deformed by reverse faults involving the underlying basement therefore a switch from thin skinned to thick skinned thrusting occurred as the apulian platform carbonates and the underlying thick continental lithosphere were deformed during the latest shortening stages apatite fission track data showing cooling ages ranging between 9 2 1 0 and 1 5 0 8 ma indicate that exhumation marks these late tectonic stages probably initiating with the buttressing of the allochthonous wedge against the western margin of the apulian platform pliocene pleistocene foreland advancing of the allochthonous units exceeds the total amount of slip that based on cross section balancing and restoration could be transferred to the base of the allochthon from the underlying thick skinned structures this suggests that emplacement of the allochthon above the western portion of the apulian platform carbonates was followed by gravitational readjustments within the allochthonous wedge coeval and partly associated with thick skinned shortening at depth the related denudation processes are interpreted to have played a primary role in tectonic exhumation

variations in earthquake size distribution across different stress regimes the earthquake size distribution follows in most instances a power law1 2 with the slope of this power law the b value commonly used to describe the relative occurrence of large and small events a high b value indicates a larger proportion of small earthquakes and vice versa statistically significant variations of b values have been measured in laboratory experiments mines and various tectonic regimes such as subducting slabs near magma chambers along fault zones and in aftershock zones3 however it has remained uncertain whether these differences are due to differing stress regimes as it was questionable that samples in small volumes such as in laboratory specimens mines and the shallow earth s crust are representative of earthquakes in general given the lack of physical understanding of these differences the observation that b values approach the constant 1 if large volumes are sampled4 was interpreted to indicate that b 1 is a universal constant for earthquakes in general5 here we show that the b value varies systematically for different styles of faulting we find that normal faulting events have the highest b values thrust events the lowest and strike slip events intermediate values given that thrust faults tend to be under higher stress than normal faults we infer that the b value acts as a stress meter that depends inversely on differential stress

paleomagnetism and the adriatic promontory a reappraisal the geodynamic evolution of the western mediterranean area was influenced strongly by the adriatic promontory of the african plate which can be outlined at present by current seismicity and by facies and ophiolite distributions paleomagnetic results from different parts of the promontory contribute useful information about its past history the evaluation of these data is made difficult by the lack of a well defined apparent polar wander path for africa this has resulted in occasional overinterpretation of some paleomagnetic studies results from umbria and the southern alps cover a long enough period of time to define part of an apw path and support the idea that the promontory moved as an adjunct to the african plate during the late mesozoic and early cenozoic a conservative evaluation of cretaceous paleomagnetic data the most abundant for the promontory as a whole shows no strong evidence for previously proposed counterclockwise rotations of sicily or the southern alps relative to the african plate paleomagnetic data however suggest about 17 degrees counterclockwise rotation of autochthonous gargano and istria and about 25 degrees counterclockwise rotation of allochthonous umbria tectonic rotation of the middle part of the promontory appears to have occurred without significant rotation of its northern and southern extremities

oligo miocene rotation of sardinia kar ages and paleomagnetic data of tertiary volcanics abstract conventional k ar dating was carried out on mineral separates mostly plagioclases from middle tertiary volcanics of sardinia along with paleomagnetic studies the close agreement of dates from the two methods establishes the rotation age of sardinia relative to europe within a rather short time span of 1 5 ma between 20 5 and 19 ma from correlation of our results with the geomagnetic time scale it is suggested that the rotation took place shortly after the magnetic anomaly 6

active tectonics in the central apennines and possible implications for seismic hazard analysis in peninsular italy abstract the central apennines fault system cafs of peninsular italy overprints earlier structures of a neogene fold and thrust belt and includes segments characterized by diffuse seismicity distributed within a nnw sse trending zone 50 60 km wide the system has been analysed by means of morphotectonic and structural analysis of exposed active fault segments the resulting fault structure consists of an interconnecting network of roughly n s trending left lateral strike slip segments and mostly nw se oriented transtensional to normal faults evidence for recent activity of cafs structures is provided by faulted middle pleistocene holocene deposits including 30 40 ka old pyroclastites and 40 ka old palustrine sediments fresh scarps in both bedrock and late quaternary continental deposits and decametric lateral offsets locally affecting the post wurmian drainage pattern of the area the regional stress field responsible for the development and evolution of the cafs as inferred from fault slip data is characterized by a nw se compression and by a ne sw extension the cafs pattern and its present day kinematics have been related to left lateral strike slip motion on north south trending crustal faults the existence of deep seated strike slip faults in the central apennines has implications for seismic hazard analysis motion along these structures suggests in fact that coseismic surface faulting is distributed and that cumulative displacements include normal transtensional and strike slip components the seismogenic potential of cafs structures can therefore be best described by multiple rupture models and be better analysed in terms of partial contributions of lower rank features constituting congruent structural associations within the system

the carbonate tectonic units of northern calabria italy a record of apulian palaeomargin evolution and miocene convergence continental crust subduction and exhumation of hp lt rocks in northern calabria italy the metasedimentary succession of the lungro verbicaro tectonic unit preserves mineral assemblages suggesting underthrusting to depths in excess of 40 km internal deformation of these rocks occurred continuously during the following decompression index mineral composition associated with progressively younger tectonic fabrics indicates that a substantial part of the structural evolution took place within the blueschist facies p t field despite their tectonic and metamorphic history the rocks of the lungro verbicaro unit preserve significant sedimentary and palaeontological features allowing correlations with successions included in adjacent thrust sheets and the reconstruction of the mesozoic continental margin architecture the subduction exhumation cycle recorded by the lungro verbicaro unit is entirely of miocene age this portion of the apulia continental palaeomargin was involved in convergence related deformation not earlier than the aquitanian the integration of our results with available constraints on the tectonic evolution of the apennine calabrian arc system suggests that subduction and most of the subsequent exhumation of the lungro verbicaro unit occurred up to langhian time at maximum vertical rates in excess of 15 mm a 1 the exhumation process was then completed at much slower rates 1 in late miocene time as indicated by both apatite fission track data and stratigraphic information

global review of human induced earthquakes the human induced earthquake database hiquake is a comprehensive record of earthquake sequences postulated to be induced by anthropogenic activity it contains over 700 cases spanning the period 1868 2016 activities that have been proposed to induce earthquakes include the impoundment of water reservoirs erecting tall buildings coastal engineering quarrying extraction of groundwater coal minerals gas oil and geothermal fluids excavation of tunnels and adding material to the subsurface by allowing abandoned mines to flood and injecting fluid for waste disposal enhanced oil recovery hydrofracturing gas storage and carbon sequestration nuclear explosions induce earthquakes but evidence for chemical explosions doing so is weak because it is currently impossible to determine with 100 certainty which earthquakes are induced and which not hiquake includes all earthquake sequences proposed on scientific grounds to have been human induced regardless of credibility challenges to constructing hiquake include under reporting which is 30 of m 4 events 60 of m 3 events and 90 of m 2 events the amount of stress released in an induced earthquake is not necessarily the same as the anthropogenic stress added because pre existing tectonic stress may also be released thus earthquakes disproportionately large compared with the associated industrial activity may be induced knowledge of the magnitude of the largest earthquake that might be induced by a project mmax is important for hazard reduction observed mmax correlates positively with the scale of associated industrial projects fluid injection pressure and rate and the yield of nuclear devices it correlates negatively with calculated inducing stress change likely because the latter correlates inversely with project scale the largest earthquake reported to date to be induced by fluid injection is the 2016 m 5 8 pawnee oklahoma earthquake by water reservoir impoundment the 2008 m 8 wenchuan people s republic of china earthquake and by mass removal the 1976 m 7 3 gazli uzbekistan earthquake the minimum amount of anthropogenic stress needed to induce an earthquake is an unsound concept since earthquakes occur in the absence of industrial activity the minimum amount of stress observed to modulate earthquake activity is a few hundredths of a megapascal and possibly as little as a few thousandths equivalent to a few tens of centimeters of water table depth faults near to failure are pervasive in the continental crust and induced earthquakes may thus occur essentially anywhere in intraplate regions neither infrastructure nor populations may be prepared for earthquakes human induced earthquakes that cause nuisance are rare but in some cases may be a significant problem e g in the hydrocarbon producing areas of oklahoma usa as the size of projects and density of populations increase the potential nuisance of induced earthquakes is also increasing and effective management strategies are needed

control of rupture by fault geometry during the 1980 el asnam algeria earthquake summary the el asnam earthquake of 1980 october 10 ms 7 3 occurred on a segmented reverse fault in the atlas mountains of algeria this report re examines the teleseismic data for the main shock and major aftershocks in the light of detailed studies of the surface breaks geodetic changes and aftershock distribution the observed thrust fault is split into southern central and northern segments by distinct offsets and changes in trend the southern and central segments are each about 12 km long but the northern segment showed only 3 4 km of surface thrust breaks however widespread tensional faulting on ridges in the north east area together with focal mechanisms of locally recorded aftershocks indicates that a series of imbricate listric thrusts exists to the north of the northern fault segment using isc arrival time lists a relative relocation scheme is applied to the main shock and major aftershocks to improve their locations with respect to the mapped faults the main shock epicentre was at the south west end of the fault system in a zone where the thrust has a zig zag surface trace by contrast most of the major aftershocks were located further north east and were associated with the northern thrust segment and the imbricate thrusts to the north the largest aftershock mb 6 1 which occurred about 3 hr after the main shock was located to the east of the main thrust fault beneath the chelif alluvial basin first motion fault plane solutions are presented for the main shock and largest aftershock the main shock solution indicates a fault plane dipping 54 nw with strike 040 the aftershock solution however has a more e w trend 080 in agreement with the trends of the basin edges near its location the rupture history of the main shock is investigated by forward modelling of the long period p waves four subevents are clearly distinguishable the first three subevents occurred in rapid succession and contributed to the first cycle of the p wave radiation these three subevents represent the successive rupturing of the southern central and northern fault segments in order to match the observed waveforms these three ruptures must have different mechanisms and moments the fault segments have successively shallower dipts from south to north 54 45 and 40 respectively and the central segment had the largest moment release in agreement with the geodetic data of ruegg et al the delay times between the three sources suggest a rupture velocity of about 3 5 km s 1 and their nucleation depths were 7 km the junctions between the fault segments acted as geometric barriers to the rupture propagation but were broken by its passage the fourth subevent of the main shock produced the second cycle of the p wave radiation it began about 18 s after the first i e several seconds after the end of the third rupture nabelek demonstrates that the fourth subevent occurred on a shallow angle 20 thrust plane examination of the locally recorded aftershocks suggests that this plane is a decollement surface underlying the imbricate thrusts of the north east area the total seismic moment found from the body wave modelling is 7 7 1026 dyne cm in good agreement with geodetic and surface wave studies

tectono stratigraphic and kinematic evolution of the southern apennines calabria peloritani terrane system italy abstract temporal controls such as sedimentation ages in foredeep and wedge top basins combined with information about stratigraphic and metamorphic evolution ages and characterization of magmatic rocks deep structures burial and exhumation histories allowed us to obtain kinematic estimations of the southern apennines calabria peloritani terrane system evolution from the late oligocene to recent calculated thrust front velocities suggest to subdivide the orogenic evolution in main five kinematic stages characterized by different velocity trends nine kinematic complexes from a to i i e sets of tectonic units deformed in the same time range are determined according to foredeep ages these complexes bounded by main regional thrust faults encompass one or more tectonic sub units and successions of different paleoenvironment domains paleogeographic evolution model indicates according to available paleomagnetic data a counterclockwise rotation with a mean angle of 60 for the apennine platform carbonates whereas a mean angle of 20 for the eastern sector of the apennine platform and western side of apulian platform shortening estimations for the apennine successions show values ranging between 55 and 88 and a linear best fit indicating an increase from 60 nw sector to ca 90 se sector such high values are consistent with a deformation dominated by a thin skinned tectonics on the contrary the low value of 28 calculated for mt alpi suggests an exhumation ruled by high angle deep seated structures characterized by limited displacements tectonic vergences referred to middle late miocene late miocene and pliocene middle pleistocene when restored indicate an average eastward tectonic transport finally tectonic evolution is summarized in eleven schematic cross sections and corresponding paleogeographic maps

space time variations in source parameters of mining induced seismic events with m 0 space time variations in source parameters and fault plane solutions are related to structural mapping data and local regional stress field measurements in an attempt to characterize the behavior of a rock mass in the vicinity of an excavation in a mine source parameters i e total seismic energy p and s wave energy seismic moment static stress drop and apparent stress were analyzed for 85 events with moment magnitudes between 2 2 m 0 3 within a 90 m microseismic envelope ahead of an excavation these data allowed three types of failure mechanisms to be postulated a zone of flat lying extensional failures next to the excavation a zone of subvertical shear failures at the microseismic envelope boundary and a transition zone between these two where both shear and shear extensional failures occur two spatially distinct event clusters occurred at distance from the excavation for early and late stages of the excavation and next to the excavation during intermediate stages worth noting was an apparent change in p axis orientation with excavation where the average p axes before and following ore extraction were compatible with the local maximum principal stress and the p axes during intermediate excavation stages were compatible with the regional maximum principal stress or local intermediate principal stress distinct from these trends was the general increase in the values of each of the above source parameters over the duration of the excavation suggesting that stress levels were increasing as a result of the excavation geometry and procedure this was considered to be significant as rockbursts mn 1 8 to 2 7 occurred above the study area 6 months following the completion of the excavation

stratigraphy and tectonics of an internal unit of the southern apennines implications for the geodynamic evolution of the peri tyrrhenian mountain belt the parasicilide succession is a key element of the southern apennine orogen being originally located in the distal portion of the apulian palaeomargin at the neotethys ocean continent transition the succession presently included in the upper nappe complex of the thrust belt has been described elsewhere as a broken formation however detailed investigations carried out in the sele valley point out that there the parasicilide unit is characterized by a coherent stratigraphy therefore in the study area these rocks form a coherent sheet of distal continental margin oceanic sedimentary cover material included within the peri tyrrhenian mountain belt stratigraphic and structural constraints obtained from both pre and synorogenic deposits the latter including both foredeep and thrust top basin sediments suggest that the pre orogenic part of the parasicilide succession subsided into the apennine foredeep in the first part of the burdigalian the studied rocks were then involved in thrusting prior to late burdigalian early langhian times

fluvial fan deltas linking channel processes with large scale morphodynamics 1 alluvial fan deltas are built by aggrading and avulsing river channels a numerical model of flow and sediment transport in channels is combined with a condition for channel avulsion to describe evolution of the fan surface the model combines elements of two recent approaches 1 diffusional models of depositional basin filling which describe the evolution of overall morphology and 2 cellular models of channel evolution which provide simplified descriptions of channel dynamics here the cellular formulation is used simply as a template for discretizing a standard set of equations describing flow and sediment transport within channels the basic formulation is thus grid invariant and the results are in actual rather than arbitrary time and length scales the model captures the interaction between microscale channel morphodynamics including converging and diverging flow and avulsion and morphodynamics at the macroscale fan it provides a starting point for the study of a wide range of topics including the three dimensional stratigraphy of fan delta deposits and the response of fan deltas to engineering activities

upper messinian siliciclastic rocks in southeastern calabria southern italy palaeotectonic and eustatic implications for the evolution of the central mediterranean region abstract the messinian stratigraphy of eastern calabria southern italy is characterised by a threefold subdivision 1 a pelite section with local limestone and gypsum deposited in a restricted marine environment is unconformably or disconformably overlain by 2 coarse grained alluvial conglomerate which is in turn locally overlain by 3 a thin and discontinuous ribbon shaped sedimentary body of sandstone and pelite commonly displaying a shallow marine to continental progradational trend the basal unconformity disconformity coarse grain size and abrupt compositional sedimentological change of unit 2 with respect to unit 1 can be explained as a response to tectonic instability and out of sequence thrusting in the calabrian orogenic wedge possibly induced by isostatic back tilting of the wedge following the desiccation of the mediterranean sea this mechanism could explain widespread late messinian thrusting and syntectonic sedimentation along the apenninic maghrebian orogenic belt the uppermost messinian continental to shallow marine siliciclastic deposits of unit 3 crop out today at elevations of up to 300 m similar age equivalent sedimentary deposits can be traced along the apennines and the sicilian maghrebides thus indicating that the mediterranean area was flooded before deposition of the trubi formation the base of which is traditionally regarded as marking the reestablishment of marine conditions in the mediterranean region

average strain rate in the italian crust inferred from a permanent gps network ii strain rate versus seismicity and structural geology summary high quality weekly solutions for the coordinates of 45 permanent gps stations spanning 1 6 years and covering the alpine mediterranean area are used to estimate a horizontal velocity field aligned with the itrf2000 velocity datum after subtracting model velocities for the eurasian plate we show that the residual velocity field north of the apennines in the adriatic dinaric region describes a nne trending tectonic flow with a negative velocity gradient from 6 mm yr 1 ne of the apennines to virtually zero ne of the dinarids in the calabria region we observe a divergent pattern with nnw orientation which turns to west as one moves north towards tuscany very small residual velocities are observed for stations in the sardinia corsica block spain southern france and north of the alps this regional pattern of velocities defines areas of intraplate strain on the basis of good station coverage and of a strain rate value above a threshold we define five provinces calabria central apennines both in the extensional regime and north adriatic eastern alps and south adriatic under compression we show that the orientations of the principal strain rate axes agree with the stress pattern that is inferred from local seismicity a comparison of the geodetically determined strain rate with the strain rate associated with the seismic moment of earthquakes in the past 30 yr shows that each province may differ considerably from the others in the amount of seismic moment that is accommodated by surface strain for example the umbria seismic sequence of 1997 seems to have released a seismic moment that was not exceptionally large but concentrated over a short time interval so that the equivalent coseismic strain rate was larger than the value observed geodetically on average depending on the assumptions on the seismogenic volume and time span 70 100 per cent of the surface strain seems to be accommodated by the release of seismic moment in the upper italian crust

the liguride complex of southern italy a cretaceous to paleogene accretionary wedge abstract the ophiolite bearing allochthonous flysch liguride complex of the southern apennines italy has traditionally been divided into two tectonic units the metamorphic frido unit and the unmetamorphosed cilento unit the two units have hitherto been considered to derive from two distinct paleogeographic domains however the identification of cilento unit sediments within frido unit successions implies that the sediments of both units were coeval deposits within the same sedimentary basin cilento unit sediments also occur as the sedimentary cover of kilometre scale oceanic slices within the liguride complex indicating deposition on oceanic basement and not continental basement as was previously considered thrust transport directions and sediment provenance indicate that during late jurassic time this ocean basin lay to the east of the calabrian terrain and to the west of apulia calabria and apulia representing the european and african margins of neotethys respectively northwestwards subduction of oceanic crust beneath the calabrian terrain from late cretaceous time onwards produced an accretionary wedge which was later emplaced onto the apulian margin during the burdigalian collision of calabria and apulia the liguride complex represents the obducted remains of this accretionary wedge this interpretation contains three important implications for pre tertiary plate tectonic reconstructions of the western mediterranean region these are 1 1 the calabrian continental terrain formed part of the iberian plate on the north margin of neotethys this may have implications for the former location and continuation of the north pyrenean fault 2 2 the existence of a continuation of the eo alpine belt through calabria and the kabylies is placed in doubt thus requiring only one constant polarity nw dipping subduction direction to explain the structures now seen in these regions 3 3 the existence of a transform fault between the europe vergent structures of corsica and the africa vergent structures of calabria this transform must have been active from at least late cretaceous time in a position now occupied by the tyrrhenian sea

testing the validity of organic and inorganic thermal indicators in different tectonic settings from continental subduction to collision the case history of the calabria lucania border southern apennines italy abstract this paper investigates the applicability of organic and inorganic thermal parameters in a range of thermal conditions from diagenesis to epizone and in hp lt settings within the framework of continental subduction and exhumation in the southern apennines where independent thermobarometric constraints are available two juxtaposed tectonic units the hp lt lungro verbicaro unit in the hanging wall and the non metamorphic pollino ciagola unit in the footwall have been analysed for the lungro verbicaro unit clay mineral thermal parameters and vitrinite reflectance underestimate metamorphic conditions constrained by petrology suggesting that in relatively hp units these indicators are retarded9 and strongly depend on p t evolution through time on the other hand the k white mica b cell dimension provides a robust estimate of peak pressure fluid inclusion textures indicate a fast isothermal decompression during exhumation two phase inclusions from early stage syntectonic veins were trapped after isothermal exhumation at a pressure of 0 3 gpa for the pollino ciagola unit the correlation of analysed parameters effectively unravels the thermal evolution with maximum palaeotemperatures of c 150 c apatite fission tracks provide details of the final stages of exhumation indicating that both units were coherently exhumed in the late miocene following the tectonic emplacement of the lungro verbicaro unit on top of the pollino ciagola unit supplementary material x ray diffraction data whole rock composition quantitative analysis of the b cell dimension are available at http www geolsoc org uk sup18416

characterization of induced seismicity patterns derived from internal structure in event clusters seismicity induced by co2 injection at decatur illinois occurs in distinct clusters and shows no obvious correlation with the proceeding pressure front we analyse some of these clusters in more depth by using a waveform cross correlation approach with this approach we can associate about 1400 events from two clusters with moment magnitudes between 1 1 and 1 7 with specific formations of much smaller vertical dimensions 10th of meters than the depth resolution of traveltime based event locations the differentiation of reservoir and basement events and the definition of sub clusters by waveform correlation rather than by location helps to better analyse the spatio temporal evolution of the events within a cluster in the decatur case this is characterized by event migration from the reservoir into the adjacent basement the spatial variation of brune stress drop and gutenberg b value exhibit signs of a fluid driven triggering mechanism at the cluster level revealing a punctual hydraulic connection between reservoir and basement most likely associated with basement faults cutting into the reservoir the observed clustering of seismicity can thus be explained by the lateral heterogeneity of permeability and crustal strength and is overall consistent with a pressure induced triggering mechanism hence proper long term risk mitigation for large scale fluid injection close to the basement requires prior mapping of small sub seismic basement connected faults

closure of the africa eurasia north america plate motion circuit and tectonics of the gloria fault we examine the closure of the current plate motion circuit between the african north american and eurasian plates to test whether these plates are rigid and whether the gloria fault is an active transform fault we also investigate the possible existence of microplates that have been previously proposed to lie along these plate boundaries and compare the predicted direction of motion along the african eurasian plate boundary in the mediterranean with the direction of slip observed in earthquakes from marine geophysical data we obtain 13 transform fault azimuths and 40 3 m y average spreading rates 34 of which are determined from comparison of synthetic magnetic anomaly profiles to 140 observed profiles slip vectors from 32 earthquake focal mechanisms further describe plate motion detailed magnetic surveys north of iceland provide 11 rates in a region where prior plate motion models had few data magnetic profiles north of the azores triple junction record a rate of 24 mm yr 4 mm yr slower than used by prior models gloria and sea beam surveys accurately measure the azimuths of seven transform faults our plate motion model fits six of the seven within 2 two transform faults surveyed by gloria side scan sonar lie near famous area transform faults a and b and give azimuths 13 clockwise of them because recent studies show that short offset transforms such as transforms a and b are in many places oblique to the direction of plate motion we exclude azimuths from transforms with less than 35 km offset the best fitting and closure enforced vectors fit the data well except for a small systematic misfit to the slip vectors on right lateral slipping transforms slip vectors tend to be a few degrees clockwise of plate motion and mapped fault azimuths whereas on left lateral slipping transforms slip vectors tend to be a few degrees counterclockwise of plate motion and mapped fault azimuths we search the long eurasia north america boundary for evidence of an additional plate but find no systematic misfits to the data in particular if a spitsbergen plate exists and moves relative to eurasia its motion is less than 3 mm yr an africa eurasia euler vector determined by adding the eurasia north america and africa north america euler vectors is consistent with the gloria fault trend and with slip vectors from eastern azores gibraltar ridge focal mechanisms a small circle centered at the africa eurasia closure enforced pole fits the trace of the gloria fault the model in which closure was enforced predicts 4 mm yr slip across the azores gibraltar ridge and west northwest convergence near gibraltar 45 more oblique than suggested by a recent model based on compressive axes of focal mechanisms moreover our model predicts directions of plate motion that agree well with northwest trending slip vectors from thrust earthquakes between gibraltar and sicily because closure enforced vectors fit the data nearly as well as the best fitting vectors we conclude that the data are consistent with a rigid plate model and with the gloria fault being a transform fault

satellite based measurements of surface deformation reveal fluid flow associated with the geological storage of carbon dioxide interferometric synthetic aperture radar insar gathered over the in salah co sub 2 storage project in algeria provides an early indication that satellite based geodetic methods can be effective in monitoring the geological storage of carbon dioxide an injected volume of 3 million tons of carbon dioxide from one of the first large scale carbon sequestration efforts produces a measurable surface displacement of approximately 5 mm year using geophysical inverse techniques we are able to infer flow within the reservoir layer and within a seismically detected fracture fault zone intersecting the reservoir we find that if we use the best available elastic earth model the fluid flow need only occur in the vicinity of the reservoir layer however flow associated with the injection of the carbon dioxide does appear to extend several kilometers laterally within the reservoir following the fracture fault zone

on the tectonic evolution of the ligurian accretionary complex in southern italy unraveling the deformation pattern characterizing the transition from final oceanic subduction stages to early stages of deformation of a foreland continental margin is crucial for a better understanding of the geodynamic processes taking place at convergent plate boundaries in particular the combined role of internal wedge dynamics and continental margin architecture in controlling the tectonic evolution of an accretionary complex during its final emplacement onto the foreland continent is discussed in this study to this purpose we conducted integrated structural stratigraphic and low temperature thermochronometric analyses on the ligurian accretionary complex units exposed in the campania region italy and on continental margin successions located in their footwall as well as on related foredeep and wedge top basin deposits our results point out a series of late early miocene burdigalian shortening events also involving buttressing of the accretionary wedge against the crustal ramp of the foreland continental margin emplacement of the overthickened accretionary complex onto the distal part of the continental margin was followed by horizontal extension and wedge thinning aiding the development of wedge top depocenters extension may have been either related to reduced subduction rates during the middle miocene or to a period of subduction erosion known to have occurred in the northern apennines in the same time frame early miocene nw se shortening recorded by ligurian accretionary complex units was completely unrelated to later late miocene to pleistocene ne directed thrusting in the apennines which was coeval with backarc extension in the tyrrhenian sea therefore our results emphasize the occurrence of a major discontinuity in the neogene geodynamic evolution of the southern apennines the tectonic history of which may be clearly subdivided from a kinematic point of view into pre and syn tyrrhenian backarc extension stages

role of preexisting topography and overburden on strain partitioning of oblique doubly vergent convergent wedges 1 scaled sandbox modeling was used to analyze the three dimensional aspects of strain partitioning along obliquely convergent margins that underwent a subduction polarity reversal event in the experiments the first phase of shortening produced a preexisting topography that affected wedge kinematics during the second phase increasing degrees of obliquity during the first shortening phase produced different amounts of inherited topography and overburden giving way to different effects on wedge response during the second phase of shortening during the second phase the models with an inherited heavy overburden show an anomalous orientation for riedel shears predating the development of a margin parallel strike slip fault these shears are oriented at an angle that is higher than kinematically predicted with respect to the subduction slot suggesting a transient rotation of the stress applied by the obliquity of subduction in contrast experiments with a lighter overburden do not show this inconsistency in addition all the models displayed an unexpectedly high accretion rate during the second phase of shortening which we interpret to be dependent on topographical slope breaks inherited after the first phase of shortening and the critical asymmetrical architecture of doubly vergent wedges

kinematics and geological constraints of the slow moving pisciotta rock slide southern italy abstract the pisciotta landslide is a slow moving deep seated rock slide in the campania region of southern italy which has damaged a provincial road several times in the last decades and currently poses a hazard to the national railway that intersects the toe of the landslide the landslide involves an oligocene turbidite series which is composed of intercalated calcarenites marls and mudrocks the principal objectives of this study were to investigate the morphological evolution of the unstable slope quantitatively analyse ground deformations and construct an engineering geological model that is consistent with the spatial features of the landslide the long term evolution of the unstable slope was assessed through the examination of available aerial photos from 1943 to 2006 kinematic analyses of the ground deformations were conducted based on observed progressive displacement of the road as evident from the topographic maps and orthophotos 1955 2006 and the bi weekly displacement survey of 50 targets distributed across the landslide area september 2006 march 2009 the engineering geological model of the landslide was reconstructed from the stratigraphic data obtained from the study of borehole data and monitoring of inclinometers as well as from geological structural and geophysical surveys the analysis of the aerial photographs revealed an early stage of deformation in 1943 which has been gradually widening since then in addition to the main scarp and the landslide flanks other significant landslide structures such as the longitudinal and transverse cracks as well as the positive or negative morphologies were monitored and mapped in the subsequent years these studies indicated a progressive erosion of the upper part of the slope and a bulging of the foot long term kinematic analysis based on the progressive displacements of the road allowed the measurement of the ground deformations from 1955 to 2009 which revealed a cumulative horizontal displacement of up to 53 m and an average velocity of 0 98 m year 1 which has increased in the recent decades in addition the recent monitoring of the ground deformations demonstrated a continuous activity with an approximately constant rate of displacement and a composite kinematic history of the landslide body through differential displacements and associated velocities the engineering geological model of the landslide was found to be controlled by specific stratigraphic and structural constraints the landslide involves a stratigraphic interval of the saraceno formation nord calabrese tectonic unit with a largely marly argillaceous composition whose structural setting displays complex folding at the mesoscale and faulting with an approximately monocline attitude of bedding and a downslope dip direction at the macroscale the left flank of the landslide rests on a normal fault

reservoir characterization using surface microseismic monitoring microseismic monitoring of reservoir processes can be performed using surface or near surface arrays we review the published technical basis for the use of the arrays and the historical development of the method beginning with locating earthquakes through geothermal exploration to the growing field of hydraulic fracture monitoring practical considerations for the array deployment and data processing are presented the road ahead for the technology includes a move toward life of field buried arrays as well as opportunities for extended interpretation of the data particularly inversion for source mechanism estimation and measurement of anisotropy in the monitored subsurface

book review the techniques of modern structural geology volume 2 folds and fractures john g ramsay and martin i huber academic press london 1987 xi 309 398 pp price stg17 50 us 34 50 paperback

effects of vegetation on braided stream pattern and dynamics 1 investigations using a 16 m by 2 m recirculating experimental flume model of an ephemeral braided river indicate that the presence of large and erosion resistant plants within the channel e g trees or shrubs can have a significant impact on channel pattern and planform dynamics simulations show that these plants have two effects first they act as obstructions in some cases forcing the flow to divide this flow separation can allow the deposition of a small island immediately in the lee of the plant splitting the channel the net result is a substantial increase in the number of channels and correspondingly the braid index this is in direct contrast to previous studies where increased levels of vegetation in perennial streams have decreased the braid index second the plants stabilize braid bars and can form relatively stable islands in their lee significantly reducing the longitudinal migration of islands typically associated with braided rivers

deformations associated with the el asnam earthquake of 10 october 1980 geodetic determination of vertical and horizontal movements the resurvey of both a geodetic network and a leveling net was carried out in june 1981 8 months after the ms 7 3 el asnam earthquake of 10 october 1980 previous seismological and neotectonic studies ouyed et al 1981 yielding et al 1981 indicate that this event results from a northeast trending overthrust complex fault of about 40 km length which shows at least three principal segments with slightly different directions vertical movements evaluated by means of a trigonometric leveling method show an uplift of the northwestern side of the thrust fault of about 5 m and a depression of the southeastern edge of about 1 m these movements are progressively attenuated away from the fault trace horizontal movements have been evaluated by a classical first order triangulation method the resulting mean strain tensors calculated for different triangles of the geodetic network indicate a shortening of about 2 50 m which is consistent with the se nw direction of compression determined from neotectonic evaluations and focal mechanisms dislocation models are used to explain and discuss the observed deformations in light of the seismological data and observed ground breakages five segments are required to explain both horizontal and vertical deformations the magnitude of vertical displacements about 6 m at the junction between the southwest and the central segments of the fault argues for the breaking of this area during the main shock and for a slip vector of about 8 m at least in the central segment

odp leg 107 in the tyrrhenian sea insights into passive margin and back arc basin evolution leg 107 of the ocean drilling program drilled a west northwest east southeast transect of seven sites across the tyrrhenian sea the youngest of the sub basins of the mediterranean sea sites 654 653 652 and 656 document the rifting and subsidence of the sardinia passive continental margin on the upper margin site 654 we cored a classic transgressive sequence subaerial conglomerates overlain by oyster bearing sands overlain by marine marl comparison between the recovered lithologies and seismic reflection profiles suggests that the synrift sediments on the upper margin are tortonian late miocene to messinian latest miocene in age whereas synrift sediments on the lower margin are messinian to pliocene in age during the messinian desiccation of the mediterranean sites 654 and 653 now on the upper sardinian margin apparently occupied a basinal setting where they received nannoplankton bearing clays interbedded with laminated gypsum sites 656 and 652 now on the lower sardinia margin were apparently higher standing during the desiccation event their messinian facies are subaerial and lacustrine respectively we infer from these lines of evidence that tilting and subsidence occurred more than a million years earlier on the upper margin than on the lower margin such diachroneity can be interpreted in terms of migration of the zone of maximum extension above a rolling back subduction zone or in terms of extension of continental crust by shear along a deep detachment fault sites 655 651 and 650 were drilled into two small basalt floored basins of the central and eastern tyrrhenian emplacement of basaltic crust in the central tyrrhenian vavilov basin apparently began more than a million years before emplacement of basaltic crust in the eastern tyrrhenian marsili basin this observation is compatible with previous suggestions that the tyrrhenian has grown southeastward in response to rollback of the down going slab that currently dips northwestward under the toe of italy at the easternmost site high vesicularity of the basalt and benthic foram assemblages in the oldest sediments imply that the basalt erupted in water shallower than 2 500 m it has apparently subsequently subsided to its present depth of 4 100 m below sea level nearly three times as fast as normal subsidence of crust formed at a mid ocean ridge

simulation of seismic events induced by co2 injection at in salah algeria a b s t r a c t article history carbon capture and storage technology has the potential to reduce anthropogenic co2 emissions however the geomechanical response of the reservoir and sealing caprocks must be modelled and monitored to ensure that injected co2 is safely stored to ensure confidence in model results there is a clear need to develop ways of comparing model predictions with observations from the field in this paper we develop an approach to simulate microseismic activity induced by injection which allows us to compare geomechanical model predictions with observed microseismic activity we apply this method to the in salah ccs project algeria a geomechanical reconstruction is used to simulate the locations orientations and sizes of pre existing fractures in the in salah reservoir the initial stress conditions in combination with a history matched reservoir flow model are used to determine when and where these fractures exceed mohr coulomb limits triggering failure the sizes and orientations of fractures and the stress conditions thereon are used to determine the resulting micro earthquake focal mechanisms and magnitudes we compare our simulated event population with observations made at in salah finding good agreement between model and observations in terms of event locations rates of seismicity and event magnitudes 2015 the authors published by elsevier b v this is an open access article under the cc by license

tectonic evolution of pliocene pleistocene wedge top basins of the southern apennines new constraints from magnetic fabric analysis in the last decades multidiscipline investigation of the apennine mountain belt of peninsular italy has provided fundamental insights into the genesis and evolution of wedge top basins in this study we focus on shallow water to conti nental pliocene quaternary basins that formed on top of the southern apennine allochthonous wedge after its emplacement onto a large foreland carbonate platform domain apulian platform the wedge top basins analyzed in this study are mostly asymmetric being bounded to the north by a normal fault showing evidence of synsedimentary activity the basin succes sions are generally deformed by open folds and reverse faults resulting from shortening coeval with the sedimentation of the lower pliocene to lower middle pleistocene upper part of the basin fill anisotropy of magnetic susceptibility data from the basin successions are consistent with a basin evolution characterized by an initial stage of tectonic subsidence controlled by roughly north northwest south southeast oriented extension followed by southwest northeast shortening active during subse quent basin filling the latter shortening is marked by a dominant northwest southeast mean trend of the magnetic lineation obtained from most sites in the study area and is interpreted as a result of upward propagation of deep seated deformation tectonic inversion taking place within the buried apulian platform sitting in the footwall to the allochthonous wedge there fore our results emphasize a complex interplay of different tectonic processes controlling wedge top basin development resume au cours des dernieres decennies une etude multidisciplinaire de la chaine de montagnes des apennins dans la peninsule italienne a donne des apercus de la genese et de l evolution des bassins sur le prisme d accretion wedge top ba sins dans cette etude nous ciblons les bassins d eau peu profonde a continentaux datant du pliocene quaternaire qui se sont formes sur le dessus du prisme allochtone du sud des apennins apres sa mise en place sur un vaste domaine de plate forme de carbonate d avant pays la plate forme apulienne les bassins sur le prisme d accretion analyses dans la presente etude sont surtout asymetriques puisqu ils sont delimites au nord par une faille normale montrant des evidences d activite syn sedimentaire les successions de bassins sont generalement deformees par des plis ouverts et des failles inverses prove nant d un retrecissement contemporain de la sedimentation du pliocene inferieur au pleistocene inferieur moyen dans la par tie superieure du remplissage du bassin l anisotropie des donnees de susceptibilite magnetique provenant des successions de bassin concorde avec une evolution du bassin caracterisee par un stade initial de subsidence tectonique controlee par une extension a orientation generale nord nord ouest sud sud est suivie d un retrecissement sud ouest nord est actif durant le remplissage subsequent du bassin ce dernier retrecissement montre une tendance moyenne dominante nord ouest sud est de la lineation magnetique obtenue de la plupart des sites dans le secteur a l etude et il est interprete comme le resultat d une propagation vers le haut d une deformation situee en profondeur inversion tectonique qui s est produit dans la plate forme apulienne enfouie se trouvant dans l eponte inferieure du prisme allochtone nos resultats soulignent donc une interaction complexe entre les differents processus tectoniques qui controlent le developpement des bassins sur les prismes d accretion traduit par la redaction

deformation history of a synorogenic sedimentary wedge northern cilento area southern apennines thrust and fold belt italy in the northern cilento area of the southern italian apennines a deformed turbiditic succession of langhian to lower tortonian age the cilento unit unconformably overlies tectonic units liguride and sicilide derived from an oceanic accretionary complex and to the east overlies mesozoic cenozoic carbonates belonging to the apulian continental paleomargin the turbiditic succession representing the sedimentary infill of a miocene foreland basin developed over the flexured southwestern margin of the apulian plate shows a complete record of the deformation at the macroscopic and mesoscopic scales structures postdating synsedimentary slump features in the cilento unit include neptunian dikes and extensional veins perpendicular to bedding all related to high pore fluid pressures associated with burial early tectonic structures consist of minor thrust faults often conjugate and at a low angle to bedding produced by initial layer parallel shortening the main regional structure mapped in the area consists of a moderately inclined to recumbent hinterland vergent backfold this structure probably developed by shortening of the strata caught between shear surfaces that cut obliquely across bedding within the framework of a noncoaxial progressive deformation the main shear surface constituting the upper boundary to the shear zone is represented by a regional backthrust which brings mesozoic cenozoic carbonates onto the terrains of the cilento unit forming a triangle zone where backfolding of the latter occurred minor open domes and basins deform both limbs of the main regional structure probably as a result of progressive shear deformation and possibly of deformation above underlying thrust culminations it appears that high pore fluid pressures must have been important not only during the development of pretectonic i e burial related structures but also during the main tectonic deformation abnormally high fluid pressures reducing the effective stress and favoring intergranular movements suppressed cleavage formation and pervasive strain during the main folding event later in the deformation sequence a decrease in pore fluid pressure probably favored local cleavage development during refolding the deformation sequence outlined above provides a case history of the structural evolution of synorogenic clastic deposits progressively deformed and incorporated within a thrust belt this study documenting the deformation of a sedimentary wedge dominated by backfolding associated with hinterland vergent reimbrication should contribute to a better understanding of the wide range of deformation sequences and processes characterizing the tectonic evolution of thrust belt foredeep systems

estimation of multivalued arrivals in 3d models using wavefront construction part i1 a new 3d wavefield modelling approach based on dynamic ray tracing is presented this approach is called wavefront construction and it can be used in 3d models with constant or smoothly varying material properties s and p velocity and density separated by smooth interfaces wavefronts consisting of rays arranged in a triangular network are propagated stepwise through the model at each time step the differences in a number of parameters are checked between each pair of rays on the wavefront new rays are interpolated whenever this difference between pairs of rays exceeds some predefined maximum value a controlled sampling of the wavefront at all time steps is thus obtained receivers are given multiple event values by interpolation when the wavefronts pass them the strength of the wavefront construction method is that it is robust and efficient

experimental steep braided flow application to flooding risk on fans flooding processes occurring on alluvial fans are considerably different from those occurring along single thread rivers with well defined floodplains active erosion rapid sedimentation and the uncertainty in flow path make the prediction of flood evolution and extent difficult based on a large scale experiment this study investigates the long term evolution of the flow on a steep noncohesive sediment surface resembling a complex of merged alluvial fans the results are pertinent to the assessment of flooding hazard on alluvial fans at any given time the average flow occupancy was 21 of the surface however the flow was characterized by active channel switching and overflow processes the percentage of the surface remaining dry was found to decay harmonically with time a reworking time was defined as the time at which half of the surface that was initially dry remained dry whereas the other half was inundated at least once an empirical expression was developed in which reworking time is proportional to the average cross sectional area of flow and inversely proportional to the sediment supply

soil gas distribution in the main coseismic surface rupture zone of the 1980 ms 6 9 irpinia earthquake southern italy soil gas measurements of different gas species with different geochemical behaviors were performed in the area of the pecore plain a 200 m 300 m sized fault bounded extensional basin located in the northern mount marzano massif in the axial belt of the southern apennine chain the pecore plain area was affected by coseismic surface faulting during the ms 6 9 1980 irpinia earthquake the strongest and most destructive seismic event of the last 30 years in southern italy the collected data and their geostatistical analysis provide new insights into the control exerted by active fault segments on deep seated gas migration toward the surface the results define anomalies that are aligned with the nw se trending coseismic rupture of the 1980 earthquake along the western border of the plain as well as along the southern border of the plain where a hidden e w striking fault is inferred geospatial analysis highlights an anisotropic spatial behavior of 222rn along the main nw se trend and of co2 along the e w trend this feature suggests a correlation between the shape and orientation of the anomalies and the barrier conduit behavior of fault zones in the area furthermore our results show that gas migration through brittle deformation zones occurs by advective processes as suggested by the relatively high migration rate needed to obtain anomalies of short lived 222rn in the soil pores

crustal extension in the northern apennines the transition from compression to extension in the alpi apuane core complex an interpretation of northern apennine geology is presented which relates the temporal and spatial occurrence of both compressional and extensional deformation features in terms of the changing dynamic evolution within an accretionary wedge after a model proposed by platt 1986 followed by the initiation and development of continental rifting during cretaceous to eocene time an accretionary wedge formed as remnant tethyan oceanic crust subducted beneath the rotating corsica sardinia microplate microplate collision during the oligocene was characterized by the rapid imbrication of buoyant continental crust of the italian continental margin the record of which is preserved within the duplex structure geometry of the alpi apuane region the overthickened wedge geometry returned to a more stable configuration by developing extensional features during the miocene both listric normal faults at upper crustal levels and shear zones indicating evidence of distributed ductile extensional strain at mid crustal levels are recorded it is proposed that large scale regional extension with associated volcanism beginning in the messinian was represented by the intrusion of asthenospheric material from the subducted plate into the already attenuated accretionary complex further rifting perhaps aided by subduction and back arc processes in the southern apennines led to the formation of the tyrrhenian sea as an oceanic basin both the apennines and north american core complexes record evidence of crustal thickening followed by crustal thinning and finally of continental rifting this suggests that the similar histories of these regions with vastly different plate tectonic settings may both be explained by processes linked to the changing internal dynamics of accretionary wedges

kinematic evolution of the tethys belt from the atlantic ocean to the pamirs since the triassic abstract we present an updated series of kinematic reconstructions of the major plates around the tethys from the atlantic ocean to the pamirs between the early jurassic and the present this set is used elsewhere as a basis for paleogeographic maps of the entire region the problems related to the positions of the continents in the lower triassic are also discussed no direct analyses of magnetic anomalies and fracture zones in the atlantic have been made rather all available poles and rotations have been tested in order to eliminate or minimize possible kinematic errors the reconstructions are shown for nine key geological periods which correspond to well recognized magnetic anomalies except for the jurassic cretaceous boundary and the cretaceous tertiary boundary which correspond to interpolated positions paleolatitudes have been drawn using the study of westphal et al 1986 an attempt has been made to take into account the displacements caused by formation of the continental margins and basins by stretching the resulting relative vector of motions along the northern boundary of the tethys shows a significant change 80 m y ago left lateral motion with compression dominates before whereas right lateral motion with compression dominates after to the east rates of motion vary by a factor of three with time and four maxima can be clearly related to tectonic events in the late jurassic late cretaceous eocene and post middle miocene to the west north of apulia on the contrary the motion rate has not changed significantly since the early cretaceous and is close to 1 cm yr as an average these rather complex adjustments in rates and directions of relative motion are produced in great part through a complex migration of the africa eurasia pole of rotation and seem to be mostly governed by the tectonics of the tethys plate boundary

paleomagnetically determined rotations in the western sicilian fold and thrust belt new paleomagnetic data from the west sicilian fold and thrust belt indicate large scale clockwise rotations during tectonic transport for the platform and seamount paleogeographic units of the fold and thrust belt panormide and trapanese units there is a general consistency in the magnitude of rotation along strike suggesting the existence of large coherent structural units for the panormide platform clockwise rotations in the range of 90 to 140 relative to the underlying iblean parautochthon are recorded along 125 km of outcrop strike in the case of the trapanese unit clockwise rotations in the range of 47 to 70 relative to iblei are recorded along about 90 km of outcrop strike intervening basinal paleogeographic units imerese and sicanian units show clockwise rotations of similar magnitude although few reliable data are available from these units palinspastic reconstruction of the thrust belt incorporating the rotations and arguments for the present orientation of the margins of the paleogeographic units implies that the panormide platform and trapanese seamounts were originally elongated more or less north south relative to the present orientation of iblei the two units apparently coalesced to the south and were discontinuous to the north they and their intervening basins were part of a passive continental margin which occupied a large part of the area that was subsequently rifted to form the tyrrhenian sea

relationship between sediment supply and avulsion frequency in braided rivers the interplay between sediment supply s s sedimentation rate s r and the frequency of channel avulsion a f exerts a primary control on alluvial architecture in order to investigate the effect of sediment supply on avulsion frequency four froude scale model experiments of an aggrading braided river were undertaken in which the magnitude of s s was progressively increased over an eightfold range the value of a f increases at a rate slower than the increase in s s contrary to the trend previously reported by bryant falk and paola in their experimental study on alluvial fan dynamics these results suggest that the relationship between a f and s s is dependent upon bed slope and that the response of a f to an increase in s s in unconfined braided rivers may be different than that on steep alluvial fans

kinematics of the alpine arc and the motion history of adria the alps have been interpreted traditionally in terms of north or northwest directed convergence between africa and europe1 with adria the continental underpinnings of the adriatic sea and northern italy acting as a promontory of the african continent2 this has been supported by recent analyses of africa europe relative plate motions3 5 which indicate dominantly north south directed convergence during the tertiary phase of intracontinental shortening we show here however that kinematic indicators from alpine tectonites are difficult to reconcile with this motion history figs 1 and 2 and are explained best by roughly west northwest directed adria europe motion since about 70 million years ago combined with an arc normal pattern of motion driven by local body forces this implies that adria has moved independently of both africa and europe since at least the late cretaceous

tectono sedimentary evolution of the southern branch of the western tethys maghrebian flysch basin and lucanian ocean consequences for western mediterranean geodynamics the evolution of the oceanic maghrebian flysch basin and its continuation in the southern apennines was studied by reconstructing mainly representative stratigraphic successions in all sectors a common evolution has been identified rifting and drifting phases are indicated by remnants of oceanic crust jurassic limestones cretaceous palaeogene turbiditic and pelagic deposits the pre orogenic sedimentation was mainly controlled by extensional tectonics and sea level changes the occurrence of a generalized foredeep stage since the early miocene is testified by thick siliciclastic and volcaniclastic syn orogenic flysch successions the deformation of the oceanic areas began in the burdigalian and the resulting nappes were stacked in the growing chains during the middle miocene piggy back basins developed and the building of the chains was accomplished in the late tortonian areal distribution and ages of flysch deposits represent an important tool for the study of the diachronous growth of the accretionary wedges

spatio temporal evolution of frequency magnitude distribution and seismogenic index during initiation of induced seismicity at guy greenbrier arkansas abstract in this study we carry out detailed analyses of the spatio temporal variations of seismic b value during the onset of the potentially induced earthquake sequence between guy and greenbrier arkansas to investigate correlations with pore pressure change the range of b values suggests that the seismicity in the guy greenbrier area is mostly a result of the activation of pre existing faults the spatial distribution of b value correlates with modeled pore pressure changes in the northern segment of the fault b value increases with depth due to large pore pressure changes and opening of new fractures in the deeper part and stress relaxation in the shallower parts whereas in the southern segment the shallower part shows higher b values due to higher pore pressure fluctuations but the deeper part in the crystalline basement has low b value due to higher confining stress the correlation between the temporal variation of b value and hypocentral depth explains a previously observed temporal drop of b value this suggests that temporal variations should be interpreted along with the spatial variations estimation of the seismogenic indices for the guy greenbrier fault is provided our analysis suggests that monitoring changes in b value and seismogenic indices during an injection period might be used to avoid the occurrence of significant events if injection volume is reduced at critical times

a plate kinematic framework for models of caribbean evolution abstract we define the former relative positions and motions of the plates whose motions have controlled the geological evolution of the caribbean region newly determined poles of rotation defining the approximate spreading histories of the central north and the south atlantic oceans are given for the late jurassic early cretaceous anomaly sequence of the central north atlantic we have used previously published definitions of fracture zone traces and magnetic anomaly picks redetermining the pole positions and angular rotations for various isochrons on an evans and sutherland interactive graphics system for magnetic anomalies younger than the cretaceous quiet period in both oceans we 1 used seasat altimeter data to help define fracture zone traces and 2 identified and used marine magnetic anomalies to determine the positions of spreading isochrons along the flowlines indicated by the fracture zones by the finite difference method the relative paleopositions and the relative motion history between north and south america were computed this analysis defines the size and shape and the rate at which the size and shape changed of the interplate region between north and south america since the middle jurassic thus a plate kinematic framework is provided for the larger plates pertaining to the caribbean region in which can be derived more detailed scenarios for gulf of mexico and caribbean evolution north and south america diverged to approximately their present relative positions from late triassic to early campanian about 84 m y ago time this is the period during which the gulf of mexico and a proto caribbean seaway were formed since the campanian only minor relative motion has occurred from early campanian through to middle eocene times south america diverged only another 200 km and since the middle eocene minor n s convergence has occurred these very minor post early campanian motions have probably been accommodated by imperfect shear and compression along the atlantic fracture zones to the east of the lesser antilles and along the northern and southern borders of the caribbean plate accordingly it is suggested that from campanian time to the present the relative motions between the north and south american plates have had only minor effects on the structural development of the caribbean region primarily using the data of engebretson et al the convergence history of pacific plates with north america was calculated for two points near the western caribbean by completing finite difference solutions the convergence history of the pacific plates with the caribbean and south american plates can be approximated the direction and rate of convergence of the pacific plates with the americas may have controlled the style of subduction and possible microplate migration along the north american south american and western caribbean boundaries that define the eastern pacific plate margin

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