shear induced convective mixing in bottom boundary layers on slopes field data from a stratified lake demonstrate that buoyancy driven convective mixing can be an important mechanism for the formation of well mixed bottom boundary layers bbls on slopes convective turbulence is caused by differential transport of stratified water masses along the slope of a basin because the current velocity usually decreases toward the sediment water at some distance from the bottom is transported faster than is water below during upslope flow this process leads to transport of heavier water on top of lighter water and hence to unstable stratification within the bbls analogously strong bbl stratification occurs during downslope flow high frequency acoustic doppler current profiler adcp and temperature measurements in the bbls of a lake revealed the cyclic occurrence of convective turbulence driven by periodic across slope currents of internal seiching the estimated maximum buoyancy flux within the bbls was in good agreement with the highest observed dissipation rates of turbulent kinetic energy this suggests that in our specific case classical bottom shear production and the mentioned buoyancy driven convective production contributed by similar amounts to the turbulent kinetic energy

effective electrode array in mapping karst hazards in electrical resistivity tomography when conducting environmental and engineering investigations in karst terranes engineers and geologists often supplement exploratory borehole results with data gathered from surface geophysics to reduce the site characterization cost and establish the most useful locations for borings or samples when conducting resistivity investigations a frequently occurring problem is the need to determine which of the many existing electrode configurations will respond best to the material changes in karst features each array has its advantages and disadvantages in terms of depth of investigation sensitivity to horizontal or vertical variations and signal strength in the application presented in this paper numerical forward modeling was conducted of dipole dipole schlumberger and wenner arrays and they produced markedly different anomaly shapes for a conceptual model of the development of a cover collapse sinkhole the resolution of the three above mentioned arrays was further evaluated along a section of i 70 near frederick maryland where a sinkhole had occurred in the median of the highway the image from the dipole dipole array appeared to be better than those from the wenner and schlumerger arrays in displaying the sinkhole collapse area however they are all less effective than a mixed array in which apparent resistivities from all the three arrays are combined and processed together in the model because the mixed array requires a significant increase in data collection the dipole dipole array appears to be the most effective and less costly configuration in mapping karst hazards areas this conclusion was then confirmed by two case studies

historical earthquakes and variable kinematic behaviour of the 2009 l aquila seismic event central italy causative fault revealed by paleoseismological investigations abstract paleoseismological investigations has been carried out along the causative fault of the mw 6 1 2009 l aquila earthquake we dug three trenches in two different sites on the paganica fault to understand its holocene kinematic behavior paleoseismological results show a minimum of three faulting events preceding the 2009 earthquake the most recent recognized event occurred after 1420 1610 a d tentatively attributed to the 1703 february 2 seismic shock a previous event happened between 1st 2nd century a d and 7th 9th century a d probably in the interval 4th 6th century a d while another identified previous event occurred prior to 1st 2nd century a d the observed minimum displacement per event varies from 0 25 m to 0 50 m consistent with a fault length of about 22 27 km from which we infer a maximum expected mw 6 6 6 7 this implies that the paganica fault may occasionally rupture during 2009 like seismic events as well as during larger earthquakes activating contemporaneously to nearby active faults kinematically and structurally linked to the paganica fault more specifically on the basis of our data and of recent paleoseismologic studies we hypothesize a linkage of the investigated fault with the upper aterno valley fault system in this perspective the paganica fault can rupture as an independent fault segment with recurrence interval of about 3 hundreds of years and together with the upper aterno valley fault system with recurrence interval that varies between 1000 and 1500 years

transport by an intrusion generated by boundary mixing in a lake 1 a dye study was conducted to track an intrusion generated at the boundary of a small lake persistent turbid layers offshore presented evidence of possible intrusions from boundary mixing after high winds a streak of rhodamine wt was injected at the boundary of the lake where the slope was between 5 and 10 both vertical profiles and longitudinal transects of the dye concentration were measured the three dimensional dye mapping showed a distinct dye intrusion ranging between 0 5 and 1 m thick over 200 m in horizontal extent offshore 1 day after the injection profiles of temperature microstructure measured soon after the injection both at the injection site and offshore showed an elevated eddy diffusivity near the boundary where the dye was injected indicating that the intrusion resulted from boundary mixing because the dominant internal waves are subcritical the mixing is most likely due to seiching currents interacting with the boundary the propagation characteristics of the intrusion were predicted most closely by a formulation for a radially spreading intrusion governed by a balance between buoyancy and inertia these results show that intrusion generation and propagation may be a significant process for mass transport in stratified lakes and reservoirs

geodetic strain in peninsular italy between 1875 and 2001 1 we determine geodetic strain in peninsular italy by the gps reoccupation of the first order triangulation network of italy installed from 1860 the uncertainties in the original measurements about 3 ppm and the time span between the two observations imply that tectonic signals larger than about 0 03 ppm yr are resolvable along the apenninic belt where the largest earthquakes are concentrated the geodetic deformation has a clear and consistent strain pattern between adjacent regions well above the uncertainties and shows a pervasive ne sw extension along the tyrrhenian and adriatic coasts the geodetic signal is not homogeneous and is comparable with the uncertainty in the original measurements seismic deformation calculated over the same time interval agrees well with estimated extensional direction but the magnitudes of geodetic and seismic strain differ suggesting that in part of the apennines significant strain accumulation over the past 130 years may not have been released in earthquakes

deep electrical resistivity tomography for the prospection of low to medium enthalpy geothermal resources summary the growth of the geothermal industry sector requires innovative methods to reduce explo ration costs whilst minimizing uncertainty during subsurface exploration until now geoelec trical prospection had to trade between logistically complex cabled technologies reaching a few hundreds meters deep versus shallow reaching prospecting methods commonly used in hydro geophysical studies we present a recent technology for geoelectrical prospection and show how geoelectrical methods may allow the investigation of medium enthalpy geothermal resources until about 1 km depth the use of the new acquisition system which is made of a distributed set of independent electrical potential recorders enabled us to tackle logistics and noise data issues typical of urbanized areas we acquired a 4 5 km long 2 d geoelectrical survey in an industrial area to investigate the subsurface structure of a sedimentary sequence that was the target of a 700 m geothermal exploration well geo 01 satigny in the greater geneva basin western switzerland to show the reliability of this new method we compared the acquired resistivity data against reflection seismic and gravimetric data and well logs the processed resistivity model is consistent with the interpretation of the active seismic data and density variations computed from the inversion of the residual bouguer anomaly the combination of the resistivity and gravity models suggest the presence of a low resistivity and low density body crossing mesozoic geological units up to palaeogene neogene units that can be used for medium enthalpy geothermal exploitation our work points out how new geoelectrical methods may be used to identify thermal groundwater at depth this new cost efficient technology may become an effective and reliable exploration method for the imaging of shallow geothermal resources

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

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

residual transport of suspended material by tidal straining near sloping topography abstracttidal straining is known to have an important impact on the generation of residual currents and the transport of suspended material in estuaries and the coastal ocean essential for this process is an externally imposed horizontal density gradient typically resulting from either freshwater runoff or differential heating here it is shown that near sloping topography tidal straining may effectively transport suspended material across isobaths even if freshwater runoff and differential heating do not play a significant role a combined theoretical and idealized modeling approach is used to illustrate the basic mechanisms and implications of this new process the main finding of this study is that for a wide range of conditions suspended material is transported upslope by a pumping mechanism that is in many respects similar to classical tidal pumping downslope transport may also occur however only for the special cases of slowly sinking material in the vicinity of slopes with a slope angle la

unravelling the complexity of apenninic extensional fault systems a review of the 2009 l aquila earthquake central apennines italy the 2009 l aquila sequence activated a normal fault system 50 km long in the central apennines composed of two main nw trending faults 12 16 km long the main high angle l aquila segment and the campotosto listric fault the mw 6 1 l aquila mainshock nucleated on the paganica fault at a depth of 8 6 km and cut through the upper crust producing coseismic surface slip of up to 10 cm observed along a strike length of 13 km analysis of historical seismicity and data collected in paleo seismological trenches suggest that this event filled a 500 year gap in contrast the blind campotosto listric fault is composed of different fault segments displaying abrupt changes in dip at a depth where major events nucleate suggesting a rheological and geometrical control on stress concentration a foreshock sequence that started around 4 months before the l aquila mainshock activated the deepest portion of the paganica fault and marked the onset of large variations in elastic properties of the crustal volume the variations have been modelled in terms of dilatancy and diffusion processes corroborating the hypothesis that fluids play a key role in the nucleation process of extensional faults in the crust

investigating the architecture of the paganica fault 2009 mw 6 1 earthquake central italy by integrating high resolution multiscale refraction tomography and detailed geological mapping this article has been accepted for publication in geophysical journal internationa 2017 published by oxford university press on behalf of the royal astronomical society all rights reserved

convectively driven mixing in the bottom boundary layer closely spaced vertical profiles through the bottom boundary layer over a sloping continental shelf during relaxation from coastal upwelling reveal structure that is consistent with convectively driven mixing parcels of fluid were observed adjacent to the bottom that were warm by several millikelvin relative to fluid immediately above on average the vertical gradient of potential temperature in the superadiabatic statically unstable bottom layer was found to be 21 7 3 1024 km 21 or 6 0 3 1025 kg m24 in potential density turbulent dissipation rates increased toward the bottom but were relatively constant over the dimensionless depth range 0 4 1 0z d where d is the mixed layer height the rayleigh number ra associated with buoyancy anomalies in the bottom mixed layer is estimated to be approximately 1011 much larger than the value of approximately 10 3 required to initiate convection in simple laboratory or numerical experiments an evaluation of the data in which the bottom boundary layer was unstably stratified indicates that the greater the buoyancy anomaly is the greater the turbulent dissipation rate in the neutral layer away from the bottom will be the vertical structures of averaged profiles of potential density potential temperature and turbulent dissipation rate versus nondimensional depth are similar to their distinctive structure in the upper ocean during convection nearby moored observations indicate that periods of static instability near the bottom follow events of northward flow and local fluid warming by lateral advection the rate of local fluid warming is consistent with several estimates of offshore buoyancy transport near the bottom it is suggested that the concentration of offshore ekman transport near the bottom of the ekman layer when the flow atop the layer is northward can provide the differential transport of buoyant bottom fluid when the density in the bottom boundary layer decreases up the slope

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

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

imaging the structural style of an active normal fault through multidisciplinary geophysical investigation a case study from the mw 6 1 2009 l aquila earthquake region central italy firb abruzzo high resolution analyses for assessing the seismic hazard and risk of the areas affected by the 2009 april 6 earthquake no rbap10zc8k 005

the primary role of the paganica san demetrio fault system in the seismic landscape of the middle aterno valley basin central apennines abstract the paganica normal fault that caused the april 9 2009 l aquila earthquake central apennines is part of the paganica san demetrio fault system psdfs all available data useful to constrain the quaternary activity of the psdfs were reviewed with the aim to point out its role in the landscape evolution of the l aquila region and particularly of the middle aterno valley basin uplifted remnants of a low relief landscape summit paleosurface sp constrain to about 800 m the total offset of the psdfs since the late lower pleistocene also a sedimentary cycle ended at the beginning of middle pleistocene is now displaced about 550 m along the psdfs whereas alluvial deposits containing tephra layers 560 360 ka have been displaced more than 150 m by the paganica fault segment the long term slip rate values based on this evidence ranging between 0 4 and 0 9 mm y together with the short term slip rate values based on displacements along late pleistocene geomorphic features and deposits have shown that the psdfs i has played a primary role in the landscape evolution of the area despite its minor geomorphic appearance ii is linked at depth with other important listric faults located in the psdfs footwall assergi and campo imperatore faults that in this paper are interpreted as secondary faults this result has relevant seismotectonic implications for the middle aterno valley basin the psdfs is the main seismic source of the basin and controls also the seismic potential of other linked structures including the assergi and campo imperatore faults

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

evidence for surface faulting events along the paganica fault prior to the 6 april 2009 l aquila earthquake central italy 1 we performed paleoseismological investigations at four sites across the normal paganica fault pf source of the 2009 mw 6 3 l aquila earthquake with the goal of reconstructing the rupture history and of contributing to the evaluation of the maximum event expected along the pf we recognized five distinct surface faulting earthquakes including the 2009 in the trenches the age of the penultimate event is consistent with the 1461 earthquake the third event back occurred around 1000 ad the two oldest events have larger uncertainties and occurred in the interval 760 bc 670 ad and 2900 760 bc respectively the along strike vertical displacement for each paleoevent has a limited variability consistently with the fairly homogeneous slip observed in 2009 along the northern part of the rupture conversely the throws change between distinct events and range between 0 15 m in 2009 maximum estimate and close to 0 4 lower bound estimate in earlier events these paleorecords and the high fault escarpments imply that earthquakes larger than 2009 occurred on the pf with implications for the level of hazard recurrence intervals also reflect a change with time the average interval before 1000 ad is longer compared to that after this date two events occurred in the 2000 4000 years preceding 1000 ad while three events occurred since 1000 ad the age uncertainties affecting the interpreted events prevent the evaluation of a unique value for interevent interval the older events appear closely spaced in time or far apart depending on the upper or lower boundary of the age interval we tentatively assign an average interevent time of 500 years for the three youngest events whereas the time elapsed between the previous ones could be larger in the order of 1000 2000 years we calculate a late pleistocene dip slip rate for the pf of 0 2 0 4 mm yr consistent with 0 25 0 5 mm yr for the early pleistocene using age and throw of individual events we calculate a similar late holocene average dip slip rate of 0 3 0 4 mm yr this suggests that the portion of the pf where the 2009 continuous surface faulting occurred has fairly a constant average slip release since late pleistocene finally we discuss different rupture scenarios and alternative models of occurrence compatible with our data and their variability

deep electrical resistivity tomography along the tectonically active middle aterno valley 2009 l aquila earthquake area central italy three 2 d deep electrical resistivity tomography ert transects up to 6 36 km long were obtained across the paganica san demetrio basin bounded by the 2009 l aquila mw 6 1 normal faulting earthquake causative fault central italy the investigations allowed defining for the first time the shallow subsurface basin structure the resistivity images and their geological interpretation show a dissected mesozoic tertiary substratum buried under continental infill of mainly quaternary age due to the long term activity of the paganica san demetrio normal faults system psdfs ruling the most recent deformational phase our results indicate that the basin bottom deepens up to 600 m moving to the south with the continental infill largely exceeding the known thickness of the quaternary sequence the causes of this increasing thickness can be 1 the onset of the continental deposition in the southern sector took place before the quaternary 2 there was an early stage of the basin development driven by different fault systems that produced a depocentre in the southern sector not related to the present day basin shape or 3 the fault system slip rate in the southern sector was faster than in the northern sector we were able to gain sights into the long term psdfs behaviour and evolution by comparing throw rates at different timescales and discriminating the splays that lead deformation some fault splays exhibit large cumulative throws 300 m in coincidence with large displacement of the continental deposits sequence 100 m thus testifying a general persistence in time of their activity as leading splays of the fault system we evaluate the long term 3 2 5 myr cumulative and quaternary throw rates of most of the leading splays to be 0 08 0 17 mm yr 1 indicating a substantial stability of the faults activity among them an individual leading fault splay extends from paganica to san demetrio ne vestini as a result of a post early pleistocene linkage of two smaller splays this 15 km long fault splay can explain the holocene surface ruptures observed to be larger than those occurred during the 2009 l aquila earthquake such as revealed by palaeoseismological investigations finally the architecture of the basin at depth suggests that the psdfs can also rupture a longer structure at the surface allowing earthquakes larger than m 6 5 besides rupturing only small sections as it occurred in 2009

boundary mixing in lakes 1 modeling the effect of shear induced convection 1 recent studies in lakes have shown evidence for a strong influence of shear induced stratification on mixing in turbulent bottom boundary layers bbls on sloping topography these observations suggest that the periodic near bottom shear resulting from internal wave motions may lead to alternating periods of gravitationally stable and unstable stratification in the bbl with relevant implications for turbulence and mixing in the entire basin the impact of these processes for basin scale mixing is investigated here in a three dimensional processes oriented modeling study using a well investigated system lake alpnach switzerland as an example consistent with available observations our results indicate that the bbl becomes gravitationally unstable in areas with upslope flow covering a substantial fraction of the total bottom area of the lake while near bottom convection associated with the unstable stratification in these areas results in strong turbulence its contribution to net mixing is negligible since the bbl is already well mixed conversely in areas with downslope flow the near bottom shear generates stable stratification leading to a suppression of turbulence but also to larger mixing rates due to an enhanced mixing efficiency overall bbl mixing is found to dominate basin scale mixing these mechanisms are likely to be important for a large class of stratified natural waters in which boundary layer mixing is energized by periodic internal waves or basin scale motions

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

evidence for localized active extension in the central apennines italy from global positioning system observations to assess how contemporary crustal extension is accommodated in the central apennines we use a new continuous and survey style global positioning system velocity solution and model the velocity field using a bicubic spline interpolation method the partitioning of contemporary deformation over the 100 km wide central apennines belt reveals a pattern of strain accumulation that largely reflects the spatial distribution of historic and recent seismicity the highest gradients of horizontal velocities are observed across those faults associated with m 6 historical earthquakes dislocation modeling shows that interseismic elastic loading in which creep occurs below the seismogenic upper crust on the downdip extensions of historically active faults reproduces the observed velocity gradients the current resolution level of quaternary fault slip rates estimates hinders the comparison with past deformation patterns and in particular the discrimination between 1 migrating episodes of short term focused activity 2 a distributed pattern of simultaneous deformation on parallel fault systems or 3 long term localization of active extension taking into account geomorphological evidence we propose that the geodetically observed deformation spatially corresponds with a long term localization of strain along the long wavelength 100 km topographic bulge caused by its highest gravitation potential energy relative to surrounding lowlands

regional moment tensors of the 2009 l aquila earthquake sequence broadband waveform inversion of ground velocities in the 0 02 0 10 hz frequency band is successfully applied to 181 earthquakes with m l 3 of the april 2009 l aquila italy earthquake sequence this was made possible by the development of a new regional crustal velocity model constrained by deep crustal profiles surface wave dispersion and teleseismic p wave receiver functions and tested through waveform fit although all earthquakes exhibit normal faulting with the fault plane dipping southwest at about 55 for the majority of events a subset of events had much shallower dips the issue of confidence in the derived parameters was investigated by applying the same inversion procedure by two groups who subjectively selected different traces for inversion the unexpected difficulty in modeling the regional broadband waveforms of the mainshock as a point source was investigated through an extensive finite fault modeling of broadband velocity and accelerometer data which placed the location of major moment release up dip and about 4 7 s after the initial first arrival hypocentral parameters

a primitive equation ocean circulation model using a general vertical coordinate transformation 2 application to an overflow problem the version of the ocean general circulation model of the geophysical fluid dynamics laboratory with a generalized vertical coordinate transformation introduced in part 1 is used to study the overflow of a zonal ridge in a coarse resolution grid typical for climate applications the configuration roughly resembles the greenland scotland ridge with respect to scale latitude and height of the ridge reasonable qualitative agreement with observed conditions over the iceland faroe section has been achieved especially when a deeper passage was included at the eastern end of the idealized model ridge upwelling of deep water occurs at the eastern boundary where friction and more importantly diapycnal diffusion accomplish the necessary changes in potential vorticity the overflow consists of intermediate water when the renewal time for the deep water is made much larger than that for intermediate water the meridional mass transport is most sensitive to geometric factors like the height of the ridge frictional and diapycnal processes are crucial for the potential vorticity conversion at the ridge and have a strong effect on the water mass distribution bottom friction increases the near bottom flow across f h lines resulting in a large amount of northern basin deep water south of the ridge this effect can be represented only when the frictional bottom boundary layer is adequately resolved by the numerical grid

internal tides and ocean mixing recent satellite and in situ observations have shown that at ocean ridges and other seafloor topographic features a substantial amount of energy is transferred from the main ocean tides into internal tides in his perspective garrett explains how these internal waves with tidal periods propagate through the density stratified deep ocean and eventually break down into turbulence the resulting mixing affects ocean stratification and ocean circulation it thus influences climate as well as biological production the energy for the internal tides is derived from the rotational energy of the earth moon system changes of the length of the day and the distance to the moon

complexity of the 2009 l aquila earthquake causative fault system abruzzi apennines italy and effects on the middle aterno quaternary basin arrangement abstract an mw 6 1 devastating earthquake on april 6 2009 struck the middle aterno valley abruzzi apennines italy due to the activation of a poorly known normal fault system structural analysis of the fault population and investigation of the relationships with the quaternary continental deposits through integrated field and laboratory techniques were conducted in order to reconstruct the long term tectono sedimentary evolution of the basin and hypothesize the size of the fault segment a polyphasic evolution of the middle aterno valley is characterized by a conjugate e w and n s striking fault system during the early stage of basin development and by a dip slip nw striking fault system in a later phase the old conjugate fault system controlled the generation of the largest sedimentary traps in the area and is responsible for the horst and graben structures within the basin during the early pleistocene the e w and n s system reactivated with dip slip kinematics this gave rise to intra basin bedrock highs and a significant syn tectonic deposition causing variable thickness and hiatuses of the continental infill subsequently since the end of the early pleistocene with the inception of the nw striking fault system several nw strands linked into longer splays and their activity migrated toward a leading segment affecting the paganica san demetrio basin the paganica san demetrio fault alignment the findings from this work constrain and are consistent with the subsurface basin geometry inferred from previous geophysical investigations notably two major elements of the e w and n s striking faults likely act as transfer to the nearby stepping active fault systems or form the boundaries as geometric complexities that limit the paganica san demetrio fault segment overall length to 19 3 km the resulting size of the leading fault segment is coherent with the extent of the 6 april 2009 l aquila earthquake causative fault the positive match between the geologic long term and coseismic images of the 2009 seismogenic fault highlights that the comprehensive reconstruction of the deformation history offers a unique contribution to the understanding faults seismic potential

periodic convection within littoral lake sediments on the background of seiche driven oxygen fluctuations this study examines the effects of internal seiches on heat transport through the sediment water interface and the internal seiche related temperature and oxygen fluctuations above the sediment in the littoral zone of a stratified lake high resolution temperature profiles were taken within the upper sediment accompanied by temperature and oxygen measurements within the overlying water heat transport in the upper sediment alternated between diffusion and convection at the periodicity of the internal seiches with the strongest oscillations at a period of 2 4 h during long duration events 30 min of seiche driven cooling of the sediment surface the thermal instability extended as much as 9 cm down into the sediment followed by free convective transport in the upper sediment the vertical convective heat fluxes were close to those of rayleigh benard convection for pure fluid flow the convective heat fluxes were on average three times higher than the diffusive heat fluxes and the maximum convective heat fluxes of 50 100 w m 2 were 10 20 times higher than the maximum diffusive heat fluxes internal seiches caused advective oxygen fluctuations above the sediment that can potentially reinforce the effect of convection on biochemical processes within the lake sediments periodic temperature and oxygen variations due to internal seiching can cover 10 of the sediment area depending on seasonal stratification and lake morphometry in these areas convection intensifies the transport of heat nutrients and oxygen through the sediment surface and represents an important feature of the ecology of lakes

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

an idealized model of the world ocean part i the global scale water masses abstract a primitive equation three dimensional numerical model of the ocean employing idealized versions of the real topography and surface boundary conditions is used to study the water mass structure of the world ocean in particular the response of the model to three fundamental changes in boundary conditions is investigated in an attempt to identify the mechanisms in the model which are responsible for the establishment of the largest scale features of the global water mass structure with the drake passage closed thermohaline driving alone and a fresh north atlantic surface salinity specified only the coarsest aspects of the observed t and s structure are reproduced and the entire world ocean below the thermocline is dominated by water formed at the southern boundary the salinity configuration in particular lacks much of its observed structure in this case when the drake passage is opened the resulting circumpolar flow serves to isolate the extreme southern ocean this allows waters of no

fault displacement rates on a range of timescales abstract displacements on tectonic faults primarily accrue during earthquakes at rates that vary through time to examine the processes that underlie the temporal changes in fault displacement rates we analyse displacements and displacement rates for time periods from the present to 5 10 20 300 500 1000 and 5000 kyr for 261 active reverse or normal faults from a worldwide dataset displacement rates depart from million year average rates by up to three orders of magnitude with the size of these departures inversely related to the duration of the sample period and to fault length short term 20 kyr displacement rates generally span a greater range on small faults than large a feature which suggests more variable growth on smaller faults simple earthquake slip modeling shows that variations in displacement rates require changes in both recurrence interval and slip per event and do not support the characteristic slip earthquake model as long as fault system strain rates are uniform displacement rates generally become constant over time periods between 20 and 300 kyr with the length of time required to reach stability being inversely related to the regional basin wide strain rates stable long term displacement rates and fluctuations in earthquake recurrence intervals and slip arise in part due to fault interactions

two and three dimensional heterogeneity in carbonate sediments using resistivity imaging abstract volume heterogeneity was investigated in carbonate sediments using fine scale electrical resistivity data which are sensitive to porosity and to sediment macrostructure and microstructure variability in sediment density and porosity was assessed by x radiographic and two dimensional 2d electrical resistivity measurements in 3 cm thick slabs collected from the dry tortugas in the lower florida keys a comparison of the 2d correlation lengths calculated from each assessment indicates that using methods that differ in resolution these two methods measure quite different horizontal and vertical fluctuations in sediment density and porosity other electrical resistivity experiments were conducted using a 2d network of resistivity electrodes on the surface of freshly collected box cores the resulting three dimensional 3d resistivity data provide a unique insight into the spatial variability of sediment porosity and structure at the cm scale complementary x radiograph cores provide 2d datasets of resistivity and porosity at higher resolution these data are used to establish the porosity resistivity microstructure relationships for these carbonate sediments with microstructure being described in terms of tortuosity these relationships are used to extend our interpretation in terms of porosity and tortuosity to the corresponding 3d box core resistivity datasets sediment tortuosity is investigated by numerically modeling the flow of electrical currents through a range of pore morphologies in three dimensions the results show particular sensitivity to the intra particle porosity particle shape and the relative sizes of pores and throats the 3d methodology shows promise as a non invasive measurement of buried inhomogeneities that could lead to improving models for predicting acoustic backscattering from the sediment volume

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

geometry and evolution of a fault controlled quaternary basin by means of tdem and single station ambient vibration surveys the example of the 2009 l aquila earthquake area central italy we applied a joint survey approach integrating time domain electromagnetic soundings and single station ambient vibration surveys in the middle aterno valley mav an intermontane basin in central italy and the locus of the 2009 l aquila earthquake by imaging the buried interface between the infilling deposits and the top of the pre quaternary bedrock we reveal the 3 d basin geometry and gain insights into the long term basin evolution we reconstruct a complex subsurface architecture characterized by three main depocenters separated by thresholds basin infill thickness varies from 200 300 m in the north to more than 450 m to the southeast our subsurface model suggests a strong structural control on the architecture of the basin and highlights that the mav experienced considerable modifications in its architecture over time the buried shape of the mav suggests a recent and still ongoing predominant tectonic control by the nw se trending paganica san demetrio fault system psdfs which cross cuts older ca ene and nne trending extensional faults furthermore we postulate that the present day arrangement of the psdfs is the result of the linkage of two previously isolated fault segments we provide constraints on the location of the southeastern boundary of the psdfs defining an overall 19 km long fault system this allows for earthquakes larger than m6 5 this study emphasizes the benefit of combining two easily deployable geophysical methods for reconstructing the 3 d geometry of a tectonically controlled basin our joint approach provided us with a consistent match between these two independent estimations of the basin substratum depth within 15

dynamics of mixed bottom boundary layers and its implications for diapycnal transport in a stratified natural water basin here we report on two field experiments from lake alpnach surface area 4 8 km 2 maximum depth 34 m that were designed to study the process of boundary mixing and to estimate its efficiency the ratio between the turbulent kinetic energy converted into potential energy and dissipated into heat for diapycnal tracer transport lake alpnach is particularly suited for this purpose because it is known from earlier experiments that 1 its currents follow a regular oscillatory pattern associated with basin wide standing internal waves seiches period similar to 0 5 days and 1 day respectively and 2 diapycnal tracer transport is mainly caused by boundary mixing during one of the experiments reported here strong seiches were excited regularly and damped on a timescale of the order of 3 days during the other experiment seiching motion was comparably weak if seiching is excited regularly we find a persistent well mixed bottom layer of 4 5 m height at the deepest part of the lake in the absence of regular seiching the layer disappears within 10 20 days on the sloping bottom boundaries the well mixed layers 1 are of much more transient nature 2 exhibit different thermal structure and 3 decrease in thickness toward shallower depth inversely proportionally to the stability at the same depth in the lake interior their reduced thickness is possibly the result of repeatedly occurring intrusions of boundary mixed water masses that are observed to extend horizontally similar to 100 200 m into the lake interior as a consequence of repeated generation of intrusions mixing on the sloping boundaries is expected to be considerably more efficient compared to mixing over flat bottom boundaries the observed mixing efficiency the ratio of the rate of change of potential energy below depth z caused by turbulence to the energy loss by bottom friction below depth z increases indeed from 0 01 0 01 in the deepest well mixed layers to 0 15 0 04 in the upper pycnocline

turbulent production in an internal wave bottom boundary layer maintained by a vertically propagating seiche internal seiches which supply the energy responsible for mixing many lakes are often modeled as vertically standing waves however recent observations of vertical seiche propagation in a small lake are inconsistent with the standard vertically standing model to examine the processes responsible for such propagation drag and turbulent production in the bottom boundary layer of a small lake are related to the energy supplied by a propagating seiche period 10 24 h despite complex and fluctuating stratification which often inhibited mixing within 0 4 m of the bed bottom stress was well represented by a simple drag coefficient model drag coefficient 1 5 10 3 the net supply of seiche energy to the boundary layer was estimated by fitting a model for internal wave vertical propagation to velocity profiles measured above the boundary layer 1 4 5 m above lakebed fitted reflection coefficients ranged from 0 3 at 1 cycle d frequency to 0 7 at 2 4 cycles d cf near unity coefficients of classical seiche theories the net supply of seiche energy approximately balanced boundary layer turbulent production three of four peaks in production and energy flux occurred 0 8 2 2 days after strong oscillating winds a delay comparable to the time required for seiche energy to propagate to the lakebed a model based on the estimated drag coefficient predicted the observed frequency dependence of the seiche reflection coefficient for flat bed regions in narrow lakes the model predicts that reflection is controlled by the ratio of water velocity to vertical wave propagation speed with sufficiently large ratios leading to weak reflection and clear vertical seiche propagation

on stratified flow over a ridge intersecting coastlines abstract the adjustment between two interconnecting basins of stratified fluid resulting from the formation of a pool of dense water in one is investigated with an 18 level numerical general circulation model cycm it is found that basic features of the adjustment i e i the generation of low frequency coastally trapped kelvin waves which carry information about the alongshore pressure gradient created by the denser water toward the dividing ridge ii the subsequent generation of barotropic double kelvin waves by the jebar joint effect of baroclinicity and relief effect which propagate infinitely rapidly along the ridge setting up an anticyclonic gyre iii the generation of further coastally trapped kelvin waves at the opposite coast due to an alongshore pressure gradient created by upwelling at the ridge edge associated with the closure of the barotropic gym iv the generation of a coastally confined cyclonic gyre at the opposite ridge by the jebar effect and viscous and diffusive

boundary versus internal diapycnal mixing in stratified natural waters using the fluorescent dye uranin tracer release experiments to study the contribution of bottom boundary mixing to diapycnal transport in stratified natural waters were performed in lake alpnach central switzerland during 1992 1995 a first experiment involved injecting the tracer from a point source into the center of the hypolimnion that part of the lake below the surface mixed layer an in situ fluorometer was then employed to detect the horizontal and vertical spreading of the tracer cloud allowing rates of diapycnal diffusivity to be determined as long as the tracer was confined to the interior water region the diapycnal diffusivity was relatively small however after the tracer cloud had reached the lake boundary the diapycnal diffusivity increased by approximately one order of magnitude in a second experiment the tracer was released near the sediment water interface in this case the dynamics of vertical tracer spreading were opposite during the first few hours after tracer release diapycnal diffusivities were large subsequently decreasing as the tracer cloud drifted away from the lake boundary basin wide diapycnal diffusivities calculated from heat flux measurements based on temperature profiles obtained from thermistor chains or conductivity temperature depth casts agreed well with the values obtained from the vertical tracer diffusion after horizontal homogenization the results of the tracer experiments corroborate the hypothesis that diapycnal fluxes are determined predominantly by mixing in the bottom boundary region

the baltic sea tracer release experiment 2 mixing processes 1 deep water mixing processes in the largest basin of the baltic sea gotland basin are investigated here with the help of long term moored instrumentation and turbulence microstructure measurements budgets for heat and salinity reveal a strong temporal variability in the deep water mixing coefficients that is shown to be coupled to the wind forcing down to time scales of individual wind events consistent with the results from a simultaneously conducted tracer release experiment near boundary turbulence was identified as the key processes for basin scale mixing turbulent bottom boundary layers were found to be thick and stable in the flat deep part of the basin where highest dissipation rates were observed and comparatively thin less energetic and highly variable on the slopes due to a permanent tendency for boundary layer restratification in the absence of internal tides strongly damped basin scale topographic waves with periods of a few days a deep rim current and to a smaller extent near inertial waves were identified as the main energy sources for boundary mixing these results are likely to be relevant also for other medium sized stratified basins

electrical resistivity tomography ert of a coastal carbonate aquifer port miou se france as part of a larger regional research program karsteau the authors have applied electrical resistivity tomography ert techniques to characterize heterogeneities in the port miou coastal karst aquifer cassis se france field surveys were carried out on intensely fractured and karstified urgonian carbonates extensive research has characterized macro and micro scale geology of the port miou area and particularly underground water filled conduits and fault fracture and karst systems within a former quarry the authors applied 2d ert along two surface profiles of length 420 and 595 m to test capability for delineating subsurface conduits and possibly relationship between conduit and fault fracture karst orientation and 3d ert with a dense 120 electrode array at 1 m spacing 11 10 m was applied over an area of the quarry that had been profiled using 3d georadar and which has had intensive nearby structural geological interpretation the 2d profiling imaged several underground conduits at depths to 50 m below ground surface and below sea level including possibly the main port miou submarine spring and smaller springs the 2d profiling within the quarry provided a better understanding of the connectivity between major fractures and faults on the quarry walls and secondary springs along the coast supporting flow of the secondary springs along interpreted fracture orientations in addition 2d inversion derived conductivity models indicate that high resistivity zones above sea level are associated with non saturated zones and low resistivity anomalies in the non saturated zone are associated with residual clays in paleokarsts a partitioned lower resistivity zone below sea level can be associated with a higher porosity permeability zone with fractures and karstic features inversion models of the dense 3d ert data indicate a higher resistivity volume within the larger surveyed block the survey characterized the non saturated zone and the ert resistivities are correlated with karst features interpreted by 3d georadar and visible in the inferior wall of the quarry

deep water dynamics and boundary mixing in a nontidal stratified basin a modeling study of the baltic sea recent results from a tracer release experiment have shown that similar to many lakes and ocean basins deep water mixing in the baltic sea is largely determined by mixing processes occurring in the energetic near bottom region due to the complexity and small vertical extent of this region however previous modeling studies of the baltic sea have so far not been able to provide a numerically and physically sound representation of boundary mixing here we discuss first results from a nested high resolution simulation of the central baltic sea that aims at a realistic description of the turbulent bottom boundary layer with the help of new numerical techniques adaptive coordinates and state of the art turbulence modeling using a comprehensive data set from the baltic sea tracer release experiment we show that the model is able to reproduce the key dynamical processes near inertial waves topographic waves and a rim current with excellent accuracy boundary mixing triggered by these processes was found to result in simulated basin scale mixing rates in close agreement with observations including a seasonal variability that has been emphasized in previous studies these results may be relevant also for the description of mixing in large lakes and other stratified basins

the 2009 central italy earthquake seen through 0 5 myr long tectonic history of the l aquila faults system abstract on 6 april 2009 a mw 6 3 earthquake struck l aquila and dozens of neighbouring villages abruzzo central italy causing 308 deaths and with thousands injured within italian seismicity this was the strongest event since 1980 irpinia mw 6 9 and the first located so close to a large city since 1908 messina mw 7 3 consistent data from an integrated approach including stratigraphy geomorphology tephrochronology and paleoseismology have allowed us to identify a 19 km long hitherto poorly known structure as being responsible for this earthquake paganica san demetrio fault system psdfs the fingerprinting of four well dated tephra layers and a detailed outline of the geomorphological and stratigraphic setting have provided the basis for assessing the behaviour of the psdfs since its early activity here dated at least ca 500 ka to the present the slip rate of the structure calculated over different time windows has fluctuated slightly ca 0 5 mm yr paleoseismological analyses revealed the traces of the last surface faulting events thus we unambiguously recognise the offset associated with the mw 6 7 earthquake of 1703 which was previously related to other conterminous structures along with an older comparable strong event speculatively ascribed to an event purely known as the ad 801 central apennine earthquake this study shows that a long term to short term integrated approach is crucial in seismic hazard evaluation especially when dealing with fault systems that are difficult to trace geomorphically despite being capable of generating 2009 like earthquakes or even stronger events when conterminous structures are also involved

new geological insights and structural control on fluid circulation in la fossa cone vulcano aeolian islands italy accepted 1 june 2009 available online 21 june 2009 keywords electrical resistivity self potential soil co2 degassing temperature fluid circulation hydrothermal system structural boundary vulcano la fossa cone electric resistivity tomography ert self potential sp soil co2 ux and temperature are used to study the inner structure of la fossa cone vulcano aeolian islands nine profiles were performed across the cone with a measurement spacing of 20 m the crater rims of la fossa cone are underlined by sharp horizontal resistivity contrasts sp co2 flux and temperature anomalies underline these boundaries which we interpret as structural limits associated to preferential circulation of fluids the pietre cotte crater and gran cratere crater enclose the main hydrothermal system identified at the centre of the edifice on the base of low electrical resistivity values b20 m and strong co2 degassing sp and temperature anomalies in the periphery the hydrothermal activity is also visible along structural boundaries such as the punte nere forgia vecchia and palizzi crater rims and at the base of the cone on the southern side of the edifice along a fault attributed to the nwmain tectonic trend of the island inside the punte nere crater the ert sections show an electrical resistive body that we interpret as an intrusion or a dome this magmatic body is reconstructed in 3d using the available ert profiles its shape and position with respect to the pietre cotte crater fault allows replacing this structure in the chronology of the development of the volcano it corresponds to a late phase of activity of the punte nere edifice considering the position of the sp soil co2 flux and temperature maxima and the repartition of conductive zones related to hydrothermal circulation with respect to the main structural features la fossa cone could be considered as a relevant example of the strong influence of preexisting structures on hydrothermal fluid circulation at the scale of a volcanic edifice

physical properties of turbulent benthic boundary layers generated by internal waves physical properties of active turbulent benthic boundary layers tbbl generated by basin scale internal waves were studied within a northern hemisphere thermally stratified lake a microstructure profiler was used to measure the nature of the turbulence within the tbbls while a series of thermistor chains were used to monitor the thermal structure of the lake it was observed that a wind driven anticlockwise diurnal period vertical mode one kelvin wave generated large scale motions within the water column and that the interactions between this wave and the sloping lakebed induced tbbls a simple model based on potential energy change and boundary shearing was shown to describe the mean tbbl thickness

the internal wave field in sau reservoir observation and modeling of a third vertical mode water withdrawal from mediterranean reservoirs in summer is usually very high because of this stratification is often continuous and far from the typical two layered structure favoring the excitation of higher vertical modes the analysis of wind temperature and current data from sau reservoir spain shows that the third vertical mode of the internal seiche baroclinic mode dominated the internal wave field at the beginning of september 2003 we used a continuous stratification two dimensional model to calculate the period and velocity distribution of the various modes of the internal seiche and we calculated that the period of the third vertical mode is 24 h which coincides with the period of the dominating winds as a result of the resonance between the third mode and the wind the other oscillation modes were not excited during this period

a numerical model of the ventilated thermocline abstract a steady state numerical solution is found for an idealized rectangular ocean basin driven by wind and surface buoyancy flux a three dimensional primitive equation model is used in agreement with recent analytical modeling the thermocline in the numerical solution consists of three regions quite distinct in their ventilation characteristics forming the greater part of the subtropical thermocline is an unventilated pool zone located in the core of the subtropical gyre and a ventilated zone to the east the unventilated shadow zone lies farther east and toward the equator analysis of potential vorticity on constant density surfaces is used to study the structure of the thermocline a small but intense zone of convection located in the western boundary outflow caused by rapid heat loss to the atmosphere produces source water for the ventilated zone this water of extremely low potential vorticity mode water is distributed widely into the subtropical thermocline the pool forms equ

fault and basin depocentre migration over the last 2 ma in the l aquila 2009 earthquake region central italian apennines abstract morphological stratigraphical and structural investigations integrated with palaeomagnetic and tephrostratigraphic studies and 40 ar 39 ar measurements allowed us to define the quaternary tectonic sedimentary evolution of the epicentral area of the l aquila 2009 earthquake m w 6 3 this area roughly matches the paganica san demetrio castelnuovo psc intermountain basin filled by a fluvio lacustrine succession that is variously deformed by normal faults at its early stage early pleistocene ca 2 ma the basin hosted a lake that was characterised by whitish carbonate silt and mud deposition towards the end of the early pleistocene this was partly filled by a south eastward prograding deltaic system the south easternmost portion of the deltaic system was successively abandoned and eroded while sedimentation of a braided river system developed in a smaller area westwards before 780 ka this fluvio lacustrine system the lower psc syntheme ended and the area underwent erosional and pedogenic processes these processes continued up to 460 ka with the onset of fluvial gravel and volcanic rich silty sand deposition over a narrow area of the south western psc basin an earlier unit of the upper psc syntheme early middle pleistocene around 460 ka when most of this area was again subjected to denudational processes the sedimentation migrated into the previously exposed north western area of the psc basin where fluvial alluvial sediments were deposited between ca 460 ka and ca 350 ka a later unit of the upper psc syntheme between ca 350 ka and the present the sedimentation continued uninterrupted in a slight westwards restricted area of the psc basin upper late psc syntheme the significant contraction of the basin the shifting of its depocentre the variation in its geometry and in the spatial distributions and thicknesses of the units constituting the lower upper and late psc synthemes provide evidence for strong tectonic control this resulted in progressive reduction of the activity of the south easternmost tectonic structures and parallel migration of the fault activity on the westernmost structures in this perspective the fault system responsible for the l aquila 2009 earthquake can be seen as the most recent expression of a long lasting westwards polarised process of tectonic activity transfer

mixing of a tracer in the pycnocline a patch of sulfur hexafluoride was released in may 1992 in the eastern north atlantic on an isopycnal surface near 300 m depth and was surveyed over a period of 30 months as it dispersed across and along isopycnal surfaces the diapycnal eddy diffusivity k estimated for the first 6 months was 0 12 0 02 cm2 s while for the subsequent 24 months it was 0 17 0 02 cm2 s the vertical tracer distribution remained very close to gaussian for the full 30 months as the root mean square rms dispersion grew from 5 to 50 m lateral dispersion was measured on several scales the growth of the rms width of the tracer streaks from less than 100 m to approximately 300 m within 2 weeks implies an isopycnal diffusivity of 0 07 m2 s at scales of 0 1 to 1 km larger than expected from the interaction between vertical shear of the internal waves and diapycnal mixing teasing of the overall patch initially about 25 km across into streaks with an overall length of 1800 km within 6 months supports predictions of exponential growth by the mesoscale strain field at a rate of 3 0 5 10 7 s 1 the rms width of these streaks estimated as 3 km and maintained in the face of the streak growth indicates an isopycnal diffusivity of 2 m2 s at scales of 1 to 10 km much greater than expected from internal wave shear dispersion the patch was painted in albeit streakily by 12 months confirming expectations from analytical and numerical models homogenization of the patch continued during the subsequent 18 months while the patch continued to spread with an effective isopycnal eddy diffusivity on the order of 1000 m2 s acting at scales of 30 to 300 km

seismotectonic zoning in east central italy deduced from an analysis of the neogene to present deformations and related stress fields this paper concerns the space time evolution of the late miocene to present contractional and extensional deformations within east central italy with an analysis of the pattern and orientation of the related stress field an insight into the cover basement relations and a discussion of the seismotectonic implications the pattern and orientation of the deformation and stress fields have remained unchanged since late miocene time and have been always characterized by the coexistence and parallelism in contiguous areas in a given time of shortening to the east and elongation to the west with time during a multistage deformation history both the contraction and the extension fields have moved eastward basement involved tectonics with a west dipping multiple detachment system would have allowed the progressive eastward shift of crustal slices corresponding at the surface to well defined tectonic domains with consequent crustal thinning in the tuscan zone and crustal thickening beneath the apennine mountain chain by comparing macroseismic epicenters hypocenters and focal mechanisms with crustal structure and independently known active faults it appears evident that the pattern frequency and distribution of the crustal seismicity are tectonically controlled and that a contraction extension pair is active also at the present time in fact along the adriatic coastline contractional deformation prevails with involvement of pleistocene layers whereas beneath the apennine range extensional deformation prevails both t axes in the inner domain and p axes in the outer domain are oriented southwest northeast or west south west east northeast and this coaxiality reflects the situation depicted by the geologic stress field on this basis we have produced a seismotectonic zoning of east central italy with three distinct domains intramountain seismic zone isz foothills seismic zone fsz and coastal seismic zone csz a plausible explanation for the genesis of the active seismic deformations of east central italy is that the locally intense extensional upper crustal seismicity of the intramountain seismic zone is confined to the hanging wall of a major west dipping active extensional discontinuity whereas the less frequent contractional seismic activity of the coastal seismic zone is within the hanging wall of an outer major active west dipping contractional discontinuity an area of overlap between these two zones is represented by the foothills seismic zone where superposed epicentral patterns from different surfaces of weakness at different depths are the predictable result of the asymmetry of the deformation

palaeoseismology of the l aquila faults central italy 2009 mw 6 3 earthquake implications for active fault linkage summary urgent urban planning problems related to the 2009 april mw 6 3 l aquila earthquake prompted immediate excavation of palaeoseismological trenches across the active faults bordering the aterno river valley namely the mt marine mt pettino and paganica faults cross cutting correlations amongst existing and new trenches that were strengthened by radiocarbon ages and archaeological constraints show unambiguously that these three investigated structures have been active since the last glacial maximum period as seen by the metric offset that affected the whole slope alluvial sedimentary succession up to the historical deposits moreover in agreement with both 18th century accounts and previous palaeoseismological data we can affirm now that these faults were responsible for the catastrophic 1703 february 2 earthquake mw 6 7 the data indicate that the paganica san demetrio fault system has ruptured in the past both together with the conterminous mt pettino mt marine fault system along more than 30 km and causing an mw 6 7 earthquake and on its own along ca 19 km as in the recent 2009 event and in the similar 1461 ad event this behaviour of the l aquila faults has important implications in terms of seismic hazard assessment while it also casts new light on the ongoing fault linkage processes amongst these l aquila faults

stratification and mixing on sloping boundaries 1 in lakes as well as in the ocean vertical transport is to a large extent controlled by localized mixing along the boundaries of the respective basin direct measurements of turbulent mixing and density stratification in the bottom boundary layer of a large and deep lake reveal the importance of cross slope advection near sloping boundaries for local and basin scale vertical transport the periodic internal wave driven occurrence of up and downslope directed currents results in periodic heating and cooling of the boundary layer cooling of the boundary layer during periods of up slope flow is associated with unstable stratification and turbulent diffusivities exceed those observed during periods of down slope flow by almost one order of magnitude the periodic replacement of water in this layer with water from the interior of the basin maintains vertical density gradients and thus enhances the overall efficiency of the boundary mixing

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

effects of cross channel bathymetry and wind direction on destratification and hypoxia reduction in the chesapeake bay abstract a coupled estuarine hydrodynamic model and water quality model were used to analyze differences in destratification and anoxia hypoxia reduction by wind directions in the north south oriented chesapeake estuary usa the predominant cross channel bathymetry in the bay s anoxic center is asymmetric with a steeper and narrower shoal on the eastern shore than on the western shore which modifies wind induced circulation differently for two opposite wind directions model experiments of winds for 2 day at 8 m s indicated that for a stratified water over the aforementioned asymmetric bottom topography the easterly wind caused greater destratification and hypoxia reduction than the westerly wind this is a result of differential modulations on the two wind induced cross channel circulations by the asymmetric cross channel bathymetry the downwelling along the gentle slope in the easterly wind was characterized with stronger baroclinicity than the downwelling along the steep slope nearly perpendicular to surfaces of constant density in the westerly wind on the broad slope there undergo greater contrasting density readjustments to the vorticity changes around the bottom boundary layer bbl during upslope and downslope motions during the upslope condition the flow in bbl tends to decelerate under adverse pressure gradient which leads to a stable condition in the outer layer whereas during the downslope condition the bbl tends to accelerate under favourable pressure gradient which leads to unstable condition in the outer layer of the large scale flow overall the easterly wind caused greater anoxia reduction than the westerly wind during the entire wind period a similar case was found for northerly versus southerly winds in the early stages of the wind period modulated by the aforementioned bathymetry on the wind induced cross channel circulation the northerly wind caused greater anoxia reduction than the southerly wind however as wind continues the wind induced along channel circulation influences a larger area of greater hypoxia in the mid bay by which the southerly wind causes a greater destratification and anoxia reduction than the northerly wind this can supersede the greater destratification and anoxia reduction by the northerly wind under the bathymetry affected cross channel circulation

boundary mixing in lakes 2 combined effects of shear and convectively induced turbulence on basin scale mixing a detailed comparison of results from a numerical three dimensional hydrostatic lake model with high resolution observations of the vertical structure of the turbulent bottom boundary layer bbl in a medium size lake lake alpnach switzerland is provided the focus of this study is on the shear induced generation and destruction of stratification in the bbl that may ultimately lead to unstable layers convection the model was shown to provide a reliable description of the internal seiching dynamics as well as the local bbl properties including the generation of shear induced convection in two data sets from 2003 and 2007 basin scale mixing parameters inferred from the simulations are closely connected to the seiching motions with the hypolimnetic mixing reacting almost immediately to the variable wind forcing and seiching activity during upslope flow the bbl becomes convectively turbulent causing low mixing efficiency on a basin scale whereas during downslope flow the bbl is restratifying and shear induced turbulence is weak but leads to a higher mixing efficiency the overall deep water mixing efficiency varied in the range of 5 to 10 in this system dominated by turbulent boundary processes

spatio temporal evolution of temperature and fluid flow through a new thermo lithological boundary the case of a pit crater of karthala volcano comoros archipelago refilled on january 13th 2007 by a lava flow on january 13 th 2007 the effusive eruption of karthala volcano in the comoros islands emitted a lava flow which has been perfectly constrained inside the cylindrical shape of the choungou chagnoumeni pit crater 225m in diameter and with a thickness of about 7m the good knowledge of the geometry of this lava flow allowed modeling its cooling with the rheolef code with a good accuracy the results of the thermal modeling were compared with other measurements performed on the field 1 a high resolution electrical resistivity tomography profile crossing the boundary of the crater and 2 the thermal monitoring of temperature with eleven sensors spaced 1 meter apart at 30 cm depth perpendicularly to the boundary of the crater thanks to this multidisciplinary approach it has been possible to display that in the first order the resistivity distribution in the soil 2 years and 5 months after the eruption is directly influenced by the residual temperature and not by the structural boundary during the first three years of cooling an inversion in the shallow lateral temperature gradient was observed in temperature data set collected at 30 cm depth

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

seasonal evolution of the basin scale internal wave field in a large stratified lake the response of the water column to varying conditions of stratification and wind forcing was investigated in lake kinneret israel using data collected from thermistor chains and acoustic doppler current profilers during 1997 and 1998 the strong daily sea breeze was found to generate a vertical mode 1 internal kelvin wave and basin scale internal poincarewaves of vertical modes 1 2 and 3 the kelvin wave the dominant component of the internal wave field was responsible for alongshore velocities in the nearshore regions in the upwind nearshore regions velocities were dominated by the forced response to the wind and were cross shore in nature in the lake interior the kelvin wave effect on the horizontal velocity field was minor compared to the higher vertical mode poincarewaves the kelvin wave is shown to exist in resonant and nonforced states with the wind whereas the vertical mode 1 poincarewave energy remained relatively constant despite large variability in the forcing condi tions the energy in the higher mode poincarewaves varied greatly both on daily and seasonal timescales the results demonstrate that the wind energy forces multiple basin scale internal wave modes and that prior motion in the water column must be considered when determining the subsequent internal wave response in periodically forced systems lake kinneret israel has long been an important regional resource providing a substantial supply of drinking water as well as supporting a commercial fishery the monomictic lake is forced daily during the summer by a powerful sea breeze with stratification and wind patterns showing little variation from year to year these factors along with a fa vorable bathymetric pattern combine to make lake kinneret an ideal place for the field investigation of large scale inter nal waves and related phenomena such as the benthic bound ary layer horizontal transport and vertical mixing processes in addition to providing substantial insight into the local pro cesses and hence influencing local management study of the lake also provides fundamental knowledge of the dynam ics of enclosed basins on a geophysical scale during summer the internal rossby radius in lake kin neret is typically one half the basin width hence large scale motion in the lake will be affected by the earth s rotation and basin scale internal waves may be of topographic ross by kelvin or poincareform topographic rossby waves are sub inertial frequency oscillations that exist only in rotating fluids with variable bathymetry mysak et al 1985 stocker and hutter 1987 and these waves result from changes in depth affecting the relative vorticity of fluid elements in the absence of vertical boundaries wavelike solutions to the lin ear inviscid equations of motion for a flat bottomed region of homogeneous fluid with a constant rate of rotation are 1

morphotectonic analysis of the long term surface expression of the 2009 l aquila earthquake fault central italy using airborne lidar data abstract in this paper we present a morphotectonic study of the paganica san demetrio fault system psdfs responsible for the mw6 1 april 6 2009 earthquake l aquila central italy the discrepancy observed between the length of the seismologic geodetic modeled fault the limited size of the primary coseismic surface ruptures and the significant morphological expression of the psdfs stimulated a debate about the maximum rupture length of the psdfs and its capability to generate larger magnitude events to image the psdfs long term morphological expression and define its surface geometrical arrangement length number of fault splays and boundaries we took advantage of a high resolution airborne lidar dataset lidar topography substantially increased our confidence in detecting even subtle tectonic controlled morphologies we define the psdfs as a 19 km long fault system that displays a complex structural setting characterized by two different sectors 1 the paganica sector to the nw with a narrow deformation zone and 2 the san demetrio sector to se where the strain is accommodated by several fault splays dissecting a wider quaternary basin we also defined a first order hierarchy among the numerous fault splays across the psdfs the long term geomorphic expression of the psdfs suggests that it ruptured also involving the whole 19 km long structure besides rupturing only small sections as it occurred in 2009 this suggests a variable slip behavior empirical relations applied to this hypothesis allow up to m 6 6 earthquakes along the psdfs these results have a critical impact on the seismic hazard assessment of the area when compared with a m 6 1 event as the 2009

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

shallow subsurface structure of the 2009 april 6 mw 6 3 l aquila earthquake surface rupture at paganica investigated with ground penetrating radar p the shallow subsurface structure of the 2009 april 6 m w 6 3 l aquila earthquake surface rupture at paganica has been investigated with ground penetrating radar to study how the surface rupture relates spatially to previous surface displacements during the holocene and pleistocene the discontinuous surface rupture stepped between en echelon parallel faults within the overall fault zone that show clear holocene pleistocene offsets in the top 10 m of the subsurface some portions of the fault zone that show clear holocene offsets were not ruptured in 2009 having been bypassed as the rupture stepped across a relay zone onto a fault across strike the slip vectors defined by opening directions across surface cracks indicate dip slip normal movement whose azimuth remained constant between 210 degrees and 228 degrees across the zone where the rupture stepped between faults we interpret maximum vertical offsets of the base of the holocene summed across strike to be 4 5 m which if averaged over 15 kyr gives a maximum throw rate of 0 23 0 30 mm yr 1 consistent with throw rates implied by vertical offsets of a layer whose age we assume to be similar to 33 ka this compares with published values of 0 4 mm yr 1 for a minimum slip rate implied by offsets of middle pleistocene tephras and 0 24 mm yr 1 since 24 8 kyr from palaeoseismology the paganica fault although clearly an important active structure is not slipping fast enough to accommodate all of the 3 5 mm yr 1 of extension across this sector of the apennines other neighbouring range bounding active normal faults also have a role to play in the seismic hazard

resistivity of partially saturated carbonate rocks with microporosity simple archie s relations relate average conductivity to average porosity and average saturation and seem to work when the fluctuations of local porosity and local saturation are small in general carbonates are extremely inhomogeneous and archie s relations fail the saturation exponent n can depend on saturation itself and n can be anomalously large or small the resistivity of rocks with a mixture of micropores macropores and vugs is computed using effective medium theories quantitative mathematical modeling is used to study the influence of textural details geometries that lead to an anomalously high value of saturation exponent are contrasted with those with an anomalously low value of saturation exponent the resistivity becomes anomalously large when the conducting water phase is trapped in isolated regions the resistivity becomes insensitive to the volume fraction of water if the configuration of the major current carrying paths changes little with saturation simple examples with differenc

vertical propagation of lakewide internal waves 1 internal waves with diurnal period dominated velocities measured by an acoustic doppler profiler adp in a small lake main basin 3000 m by 400 m by 18 m adp profiles and an along lake temperature section indicate that the observed waves like seiches had horizontal wavelengths exceeding the metalimnion length however unlike non dissipative seiches the observed waves propagated vertically carrying energy to the lakebed where waves were absorbed rather than being strongly reflected this absorption is predicted by a standard parameterization of boundary layer dissipation the absence of upward propagating energy precludes seiche resonance limits focusing of waves toward attractors and suggests that hypolimnion dissipation was limited by the supply of downward propagating energy vertical wavelengths were less than the lake depth simplified calculations suggest that vertically propagating waves as opposed to vertically standing seiches are most likely where vertical wavelengths are short near bed stratification is strong and lakes are short and deep

geometry and structure of a fault bounded extensional basin by integrating geophysical surveys and seismic anisotropy across the 30 october 2016 mw 6 5 earthquake fault central italy the pian grande di castelluccio basin

finite element inversion of dinsar data from the mw 6 3 l aquila earthquake 2009 italy 1 fault slip distribution is usually retrieved from geodetic data assuming that the local crust is an elastic homogeneous and isotropic half space in the last decades spatially dense geodetic data e g dinsar maps have highlighted complex patterns of coseismic deformation that require new modeling tools such as numerical methods able to represent rheological and geometrical complexities of the earth s crust in this work we develop a procedure to perform inversion of geodetic data based on the finite element method accounting for a more realistic description of the local crust the method is applied to the 2009 l aquila earthquake mw 6 3 using dinsar images of the coseismic displacement results highlight the non negligible influence of the medium structure homogeneous and heterogeneous models show discrepancies up to 20 in the fault slip distribution values furthermore in the heterogeneous models a new area of slip appears above the hypocenter we also perform a resolution study showing that the information about fault slip distributions retrieved from geodetic data should be considered as averaged on surrounding patches

complex 3 d finite element modelling of the 2009 april 6 l aquila earthquake by inverse analysis of static deformation summary on 2009 april 6 a mw 6 3 earthquake struck the abruzzi region central italy and caused severe destruction in l aquila and the surrounding area in this work we present a finite element analysis of the event based on a realistic complex 3 d model accounting for topographic relief and rheological heterogeneities deduced from local tomography finite element computed green s functions were implemented in a linear inversion of gps coseismic displacements to retrieve the slip distribution on the rupture plane the inverted slip models basically agree with previous studies carried out on homogeneous domains but reveal the presence of a single high slip patch whereas half space or 1 d approaches obtain a more complex slip pattern our results point out that the introduction of 3 d features significantly influences the obtained source model suggesting a trade off between domain complexities and source details

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