the preparatory phase of the mw 6 1 2009 l aquila italy normal faulting earthquake traced by foreshock time lapse tomography

space time evolution of crustal deformation related to the mw 6 3 2009 l aquila earthquake central italy from principal component analysis inversion of gps position time series

source complexity of the 6 april 2009 l aquila central italy earthquake and its strongest aftershock revealed by elementary seismological analysis 1 seismic recordings are immediately available when an earthquake occurs their analysis allows the reconstruction of the rupture dynamics by means of sophisticated techniques which usually need some tests to provide robust results however immediate information on the source kinematics is required in order to imagine the fault location and extent and quickly reconstruct the areas of stress release and subsequent accumulation very simple analysis may provide useful information giving insight in source complexity right after the 6 april 2009 l aquila earthquake mw 6 3 we analyzed the seismograms recorded at broadband and strong motion stations and provided firm constraints on rupture kinematics slip distribution and static surface deformation also discriminating the actual fault plane the fracture occurred in two stages with initial updip propagation successively proceeding toward se possibly on a different plane we also analyzed the strongest aftershock mw 5 6 showing that useful indications could be retrieved for lower magnitude events

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

first assessment of the local seismic amplification susceptibility of the isernia province molise region southern italy by the integration of geological and geomorphological studies related to the first level seismic microzonation project this paper presents the results of the geological and geomorphological investigation carried out during the first level seismic microzonation project in the isernia province territory the study area falls in one of the most seismically active areas of the apennine chain and it has been struck in historical times by destructive earthquakes that caused several causalities and diffuse damages to the buildings the analysis points out the occurrence of geological features that can determine possible site amplification phenomena related to areas with extensive outcrops of thick continental deposits or to unstable areas both covering about 48 of the investigated areas the latter are sometimes combined with geomorphological features such as scarps isolated peaks and ridges that are also responsible for possible site amplification in addition a susceptibility to local seismic amplification index has been introduced which highlights that more than 64 of the investigated area along with a significant percentage of buildings fall within the highest categories of susceptibility to local seismic amplification

post seismic relaxation following the 2009 april 6 l aquila italy earthquake revealed by the mass position of a broad band seismometer summary post seismic relaxation is known to occur after large or moderate earthquakes on time scales ranging from days to years or even decades in general long term deformation following seismic events has been detected by means of standard geodetic measurements although seismic instruments are only used to estimate short timescale transient processes albeit inertial seismic sensors are also sensitive to rotation around their sensitive axes the recording of very slow inclination of the ground surface at their standard output channels is practically impossible because of their design characteristics however modern force balance broad band seismometers provide the possibility to detect and measure slow surface inclination through the analysis of the mass position signal this output channel represents the integral of the broad band velocity and is generally considered only for state of health diagnostics in fact the analysis of mass position data recorded at the time of the 2009 april 6 l aquila mw 6 3 earthquake by a closely located sts 2 seismometer evidenced the occurrence of a very low frequency signal starting right at the time of the seismic event this waveform is only visible on the horizontal components and is not related to the usual drift coupled with the temperature changes this analysis suggests that the observed signal is to be ascribed to slowly developing ground inclination at the station site caused by post seismic relaxation following the main shock the observed tilt reached 1 7 10 5 rad in about 2 months this estimate is in very good agreement with the geodetic observations giving comparable tilt magnitude and direction at the same site this study represents the first seismic analysis ever for the mass position signal suggesting useful applications for usually neglected data

coseismic ruptures of the 24 august 2016 mw 6 0 amatrice earthquake central italy on 24 august 2016 a mw 6 0 normal faulting earthquake struck central italy causing about 300 fatalities and heavy damage a geological survey collected the coseismic effects observed at the surface in order to evaluate two competing hypotheses about their nature surface faulting versus gravitational deformation we find that the most significant geological effect is a 5 2 km long alignment of ground ruptures along the mt vettore fault system these ruptures are independent from lithology topography morphology and change in slope and exhibit an average dip slip displacement of 13 cm geometry kinematics and dimensional properties of this zone of deformation strongly lead us to favor the primary surface faulting hypothesis that fits well the predicted estimates from experimental scaling law relationships our study provides relevant hints for surface faulting in extensional domains contributing to implement the worldwide database of the moderate earthquakes

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

do earthquake storms repeat in the apennines of italy terra nova 23 300 306 2011 abstract series of multiple main shocks that develop on adjacent faults is a typical way in which active extension is accommodated in the apennines of italy this behaviour is explained by fault interaction that occurs at a scale ranging from seconds to days yielding a space time clustering of earthquakes termed as earthquake storms we show that the seismic energy released by historical earthquakes in central apennines is clustered into two main small time periods around 600 and 300 years ago during which a great portion of the normal faulting belt failed we favour the hypothesis that clustering results from sudden input of deep fluids into the brittle upper crust the roughly 300 years periodicity and the 3 4 mm year 1 of tectonic extension suggest that earthquake storms need to be taken into account in seismic hazard scenarios

imaging the rupture of the mw 6 3 april 6 2009 l aquila italy earthquake using back projection of teleseismic p waves 1 we present rupture details of the mw 6 3 april 6 2009 l aquila earthquake derived by back projecting teleseismic p waves this technique has previously been applied to large magnitude earthquakes but this is the first application to a moderate size event we processed vertical component seismograms for 60 broadband stations obtained from the incorporated research institutions for seismology iris data center the traces were aligned and normalized using a multi channel cross correlation algorithm and 4th root stacking was used to image the rupture we found that the l aquila earthquake ruptured towards the south and that a second discrete pulse of energy occurred 20 25 km east of the epicenter about 17 18 s after the nominal origin time the spatial extent of the rupture image correlates well with a post seismic survey of damage in the region because the technique is potentially very fast images can be produced within 20 30 minutes of the origin time it may be useful to governmental agencies tasked with emergency response and rescue

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

complexity of the mw 6 3 2009 l aquila central italy earthquake 2 broadband strong motion modeling 1 near fault strong ground motions 0 1 10 hz recorded during the mw 6 3 2009 l aquila earthquake exhibit great spatial variability modeling the observed seismograms allows linking distinct features of the observed wavefield to particular source and propagation effects and provides insights on strong motion complexity from this moderate magnitude event we utilize a hybrid integral composite approach based on a k square kinematic rupture model combining low frequency coherent and high frequency incoherent source radiation and providing omega squared source spectral decay several source model features proven to be stable by means of an uncertainty analysis in the preceding low frequency 2 hz

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

surface displacements and source parameters of the 2003 bam iran earthquake from envisat advanced synthetic aperture radar imagery 1 the mw 6 6 26 december 2003 bam iran earthquake was one of the first earthquakes for which envisat advanced synthetic aperture radar asar data were available using interferograms and azimuth offsets from ascending and descending tracks we construct a three dimensional displacement field of the deformation due to the earthquake elastic dislocation modeling shows that the observed deformation pattern cannot be explained by slip on a single planar fault which significantly underestimates eastward and upward motions se of bam we find that the deformation pattern observed can be best explained by slip on two subparallel faults eighty five percent of moment release occurred on a previously unknown strike slip fault running into the center of bam with peak slip of over 2 m occurring at a depth of 5 km the remainder occurred as a combination of strike slip and thrusting motion on a southward extension of the previously mapped bam fault 5 km to the east

the displacement field of the landers earthquake mapped by radar interferometry geodetic data obtained by ground or space based techniques can be used to infer the distribution of slip on a fault that has ruptured in an earthquake although most geodetic techniques require a surveyed network to be in place before the earthquake1 3 satellite images when collected at regular intervals can capture co seismic displacements without advance knowledge of the earthquake s location synthetic aperture radar sar interferometry first introduced4 in 1974 for topographic mapping5 8 can also be used to detect changes in the ground surface by removing the signal from the topography9 10 here we use sar interferometry to capture the movements produced by the 1992 earthquake in landers california11 we construct an interferogram by combining topographic information with sar images obtained by the ers 1 satellite before and after the earthquake the observed changes in range from the ground surface to the satellite agree well with the slip measured in the field with the displacements measured by surveying and with the results of an elastic dislocation model as a geodetic tool the sar interferogram provides a denser spatial sampling 100 m per pixel than surveying methods1 3 and a better precision 3 cm than previous space imaging techniques12 13

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

insights from the mw 6 3 2009 l aquila earthquake central apennines unveiling new seismogenic sources through their surface signatures the adjacent san pio fault terra nova 23 108 115 2011 abstract we analysed a broad region around l aquila in search of seismogenic faults similar to that responsible for the 6 april 2009 earthquake mw 6 3 having in mind the lessons learned from this earthquake we focused on adjacent areas displaying similar morphotectonic geological and structural features the basin running from barisciano to civitaretenga navelli notably located near the southeastern edge of the 2009 aftershock pattern appears to be one such area we collected morphotectonic and structural data indicating that this basin is underlain by a major active normal fault the san pio fault all the observations are very much reminiscent of the morphotectonic geological and structural setting of the area struck by the l aquila earthquake suggesting that the newly identified fault has the potential for a mw 6 2 shock

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

source model for the mw 6 7 23 october 2002 nenana mountain earthquake alaska from insar 1 the 23 october 2002 nenana mountain earthquake mw 6 7 occurred on the denali fault alaska to the west of the mw 7 9 denali earthquake that ruptured the same fault 11 days later we used 6 interferograms constructed using radar images from the canadian radarsat 1 and european ers 2 satellites to determine the coseismic surface deformation and a source model data were acquired on ascending and descending satellite passes with incidence angles between 23 and 45 degrees and time intervals of 72 days or less modeling the event as dislocations in an elastic half space suggests that there was nearly 0 9 m of right lateral strike slip motion at depth on a near vertical fault and that the maximum slip in the top 4 km of crust was less than 0 2 m the nenana mountain earthquake increased the coulomb stress at the future hypocenter of the 3 november 2002 denali earthquake by 30 60 kpa

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

the 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

slip distributions on active normal faults measured from lidar and field mapping of geomorphic offsets an example from l aquila italy and implications for modelling seismic moment release surface slip distributions for an active normal fault in central italy have been measured using terrestrial laser scanning tls in order to assess the impact of changes in fault orientation and kinematics when modelling subsurface slip distributions that control seismic moment release the southeastern segment of the surface trace of the campo felice active normal fault near the city of l aquila was mapped and surveyed using techniques from structural geology and using tls to define the vertical and horizontal offsets of geomorphic slopes since the last glacial maximum 15 3 ka the fault geometry and kinematics measured from 43 sites and throw heave measurements from geomorphic offsets seen on 250 scarp profiles were analysed using a modification of the kostrov equations to calculate the magnitudes and directions of horizontal principal strain rates the map trace of the studied fault is linear except where a prominent bend has formed to link across a former left stepping relay zone the dip of the fault and slip direction are constant across the bend throw rates since 15 3 ka decrease linearly from the fault centre to the tip except in the location of the prominent bend where higher throw rates are recorded vertical coseismic offsets for two palaeo earthquake ruptures seen as fresh strips of rock at the base of the bedrock scarp also increase within the prominent bend the principal strain rate calculated by combining strike dip slip direction and post 15 3 ka throw rate decreases linearly from the fault centre towards the tip the strain rate does not increase across the prominent fault bend the above shows that changes in fault strike whilst having no effect on the principal horizontal strain rate can produce local maxima in throw rates during single earthquakes that persist over the timescale of multiple earthquakes 15 3 ka detailed geomorphological and structural characterisation of active faults is therefore a critical requirement in order to properly define fault activity for the purpose of accurate seismic hazard assessment we discuss the implications of modelling subsurface slip distributions for earthquake ruptures through inversion of gps insar and strong motion data using planar fault approximations referring to recent examples on the nearby paganica fault that ruptured in the mw 6 3 2009 l aquila earthquake

the 1994 sefidabeh eastern iran earthquakes revisited new evidence from satellite radar interferometry and carbonate dating about the growth of an active fold above a blind thrust fault in 1994 three shallow earthquakes of mw 6 occurred close together on blind thrusts near sefidabeh in eastern iran in an earlier study of the teleseismic waveforms the geomorphology and the faulting in the epicentral region it was suggested that these earthquakes were associated with the growth of a ridge above a blind thrust fault system whose activity could be detected by its effect on the surface drainage in this study we present a sar interferogram that precisely determines the location and amount of coseismic surface displacements showing that the earthquakes in the sefidabeh sequence probably occurred on en echelon fault segments associated with three stepping ridges we also present u th dates of 100 ka for lake deposits uplifted by the growing ridge from the cumulative dated uplift and knowledge of the surface displacements due to an earthquake sequence we estimate that 120 such events have occurred in the past 100 ka with an average recurrence interval of 830 yr and an average convergence rate of 1 5 mm yr 1 on the sefidabeh thrust each estimate has an uncertainty of a factor of two either way we argue that the sefidabeh fault originally formed by coalescence of many small fault segments and has grown in length at about 2 cm yr 1 in the past 100 ka though the coseismic surface deformation observed in the sar interferogram closely resembles folding the overall topography does not because of inherited topography associated with earlier geological deformation in spite of this the activity of the buried thrust fault can easily be detected by its effect on the surface drainage a significant lesson when interpreting landscapes that are not entirely due to the present day deformation

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

distribution and magnitude of post seismic deformation of the 2009 l aquila earthquake m6 3 surface rupture measured using repeat terrestrial laser scanning we captured post seismic deformation close to the surface rupture of the 2009 l aquila earthquake m6 3 central italy using repeat terrestrial laser scan tls methods from 8 to 126 d after the earthquake we repeatedly laser scanned four road surfaces that intersected the earthquake surface rupture we modelled vertical near field deformation at millimetre level precision by comparing subsequent laser scan data sets to the first acquired at each site the horizontal post seismic deformation at each site was measured between reflectors paired across the rupture the tls data were supplemented by total station data from a fifth site which measured the vertical and horizontal components of post seismic deformation between two points spanning the rupture we find post seismic deformation increased between 44 and 126 d at the southeastern end of the rupture beneath which a significant gradient in coseismic slip exists within the fault zone the location rate of decay and spatially localized nature of the post seismic deformation within tens of metres of the surface rupture suggests it is due to afterslip in the fault zone driven by increased shear stresses at the edges of regions which slipped coseismically we note that the magnitude of post seismic deformation in the far field obtained from insar and gps is not significantly greater than the deformations we have measured close to the rupture we suggest that shallow localized afterslip within the fault zone is responsible for the majority of the regional post seismic deformation field

analysis of a 150 m sediment core from the co seismic subsidence depocenter of the 2009 mw 6 1 l aquila earthquake italy implications for holocene pleistocene tectonic subsidence rates and for the age of the seismogenic paganica fault system abstract laqui core was drilled in the co seismic subsidence depocenter shown by dinsar images in the bazzano sub basin after the 2009 mw 6 1 l aquila earthquake laqui core aimed at gathering high resolution integrated stratigraphy and defining its relationships with the paganica and other active faults that yielded co seismic subsidence lithostratigraphy and micropaleontological analyses indicate a late pleistocene holocene fluvial alluvial sequence and below 41 m palustrine sediments sandwiching at 84 115 m a thick gravel package four 14c ages gathered from 5 to 15 m yield calibrated ages between 6 and 41 ka bp paleomagnetism reveals a normal polarity above 84 m while below the gravel package 115 m it shows frequent polarity changes the occurrence of intervals of clear reverse polarity testifies below 115 m the deposition during the matuyama chron we conclude that the normal polarity package down to 84 m along with the underlying gravels were deposited at high sedimentation rate 0 46 mm yr for the upper 15 m during the brunhes chron

reverse drag revisited why footwall deformation may be the key to inferring listric fault geometry abstract although reverse drag the down warping of hanging wall strata toward a normal fault is widely accepted as an indicator of listric fault geometry previous studies have shown that similar folding may form in response to slip on faults of finite vertical extent with listric or planar geometry in this study we therefore seek more general criteria for inferring subsurface fault geometry from observations of near surface deformation by directly comparing patterns of displacement stress and strain around planar and listric faults as predicted by elastic boundary element models in agreement with previous work we find that models with finite planar planar detached and listric detached faults all develop hanging wall reverse drag folds all of these model geometries also predict a region of tension and elevated maximum coulomb stress in the hanging wall suggesting that the distribution and orientation of near surface joints and secondary faults may also be of limited utility in predicting subsurface fault geometry the most notable difference between the three models however is the magnitude of footwall uplift footwall uplift decreases slightly with introduction of a detachment and more significantly with the addition of a listric fault shape a parametric investigation of faults with constant slip ranging from nearly planar to strongly listric over depths from 1 to 15 km reveals that footwall fold width is sensitive to fault geometry while hanging wall fold width largely reflects fault depth application of a graphical approach based on these results as well as more complete inverse modeling illustrates how patterns of combined hanging wall and footwall deformation may be used to constrain subsurface fault geometry

recent terrestrial and satellite observations to model deformations at colli albani volcano central italy the colli albani volcanic complex rome italy has been dominated by episodic eruptions commencing around 561 ka and ending with the most recent activity of the albano maar phase 70 ka earthquakes of moderate intensity gas emissions and significant ground deformations are the recent evidences of a residual activity former geodetic data from leveling surveys gps stations and insar observations tracked ongoing significant uplift of the order of few mm year near the colli albani western flank different uplift rates were detected by each technique in different time spans suggesting also the possibility of sporadic recharge of the hydrothermal system the renewed high precision leveling data from igmi survey carried out in 1997 1999 and the last leveling survey carried out in 2006 show that the uplift along the route is currently significant at an average rate of 3 mm year radar interferograms from alos satellite show uplift rate of 6 mm year southwest of the central sector of the leveling route we have undertaken a joint inversion of the various geodetic data vertical rates from leveling surveys gps site velocities and insar observations acquired by alos satellite using a nonlinear inversion technique to estimate the parameters of a point pressure source possibly capable of explaining the ongoing deformation at colli albani volcano

space time distribution of afterslip following the 2009 l aquila earthquake 1 the inversion of multitemporal dinsar and gps measurements unravels the coseismic and postseismic afterslip slip distributions associated with the 2009 mw 6 3 l aquila earthquake and provides insights into the rheological properties and long term behavior of the responsible structure the paganica fault well resolved patches of high postseismic slip 10 20 cm appear to surround the main coseismic patch maximum slip 1 m through the entire seismogenic layer above the hypocenter without any obvious depth dependent control time series of postseismic displacement are well reproduced by an exponential function with best fit decay constants in the range of 20 40 days a sudden discontinuity in the evolution of released postseismic moment at 130 days after the main shock does not correlate with independent seismological and geodetic data and is attributed to residual noise in the insar time series the data are unable to resolve migration of afterslip along the fault probably because of the time interval six days between the main shock and the first radar acquisition surface fractures observed along the paganica fault follow the steepest gradients of postseismic line of sight satellite displacements and are consistent with a sudden and delayed failure of the shallow layer in response to upward tapering of slip the occurrence of afterslip at various levels through the entire seismogenic layer argues against exclusive depth dependent variations of frictional properties on the fault supporting the hypothesis of significant horizontal frictional heterogeneities and or geometrical complexities we support the hypothesis that such heterogeneities and complexities may be at the origin of the long term variable behavior suggested by the paleoseismological studies rupture of fault patches with dimensions similar to that activated in 2009 appears to have a 500 year recurrence time interval documented by paleoseismic and historical studies in addition to that paleoseismological evidence of large 0 5 m coseismic offsets seems to require seismic events recurring every 1000 2000 years characterized by 1 multisegment linkage 2 surface ruptures larger than in 2009 and 3 complete failure of the 2009 coseismic and postseismic patches

spectral element simulations of seismic waves generated by the 2009 l aquila earthquake abstract we adopt a spectral element method sem to perform numerical simulations of the complex wavefield generated by the 6 april 2009 m w 6 3 l aquila earthquake in central italy the mainshock is represented by a finite fault solution obtained by inverting strong motion and global positioning system data testing both 1d and 3d wavespeed models for central italy surface topography attenuation and the moho discontinuity are also accommodated including these complexities is essential to accurately simulate seismic wave propagation three component synthetic waveforms are compared to corresponding velocimeter and strong motion recordings the results show a favorable match between data and synthetics up to 0 5 hz in a 200 km 200 km 60 km model volume capturing features mainly related to topography or low wavespeed basins we construct synthetic peak ground velocity maps that for the 3d model are in good agreement with observations thus providing valuable information for seismic hazard assessment exploiting the sem in combination with an adjoint method we calculate finite frequency kernels for specific seismic arrivals these kernels capture the volumetric sensitivity associated with the selected waveform and highlight prominent effects of topography on seismic wave propagation in central italy online material movie of wave propagation waveform fits and stable of station parameters

surface displacements associated with the l aquila 2009 mw 6 3 earthquake central italy new evidence from sbas dinsar time series analysis 1 we investigate the surface displacements in the area affected by the april 2009 l aquila earthquake central italy through an advanced dinsar analysis in particular we apply the sbas approach to retrieve deformation maps and displacement time series from envisat data acquired between february 2003 and october 2009 and from cosmo skymed data relevant to the six month interval following the earthquake our analysis shows no evidence of pre seismic surface deformation at the 35 day temporal sampling of the envisat sensor on the other hand by benefiting of the high spatial resolution and temporal sampling of the cosmo skymed satellites we measure post seismic displacements at an unprecedented level of detail for a dinsar analysis this allows us to identify three main areas continuing to deform after the earthquake in addition our modeling shows that post seismic displacements are very likely related to the fault afterslip since their decay times are on the order of 101 102 days

strong ground motion simulation of the 6 april 2009 l aquila italy earthquake on 6 april 2009 an earthquake of mw 6 13 herrmann et al 2011 occurred in central italy close to the town of l aquila although the earthquake is considered to be a moderate size event it caused extensive damage to the surround ing area the earthquake is identified with significant directivity effects high amplitude short duration motions are observed at the stations that are oriented along the rupture direction whereas low amplitude long duration motions are observed at the stations oriented in the direction opposite to the rupture the complex nature of the earthquake combined with its damage potential brings the need for studies that assess the seismological characteristics of the 2009 l aquila mainshock in this study we present the strong ground motion simulation of this particular earthquake using a stochastic finite fault model with a dynamic corner frequency ap proach for modeling the resulting ground motions we choose two finite fault source models that take into account the source complexity of the l aquila mainshock in order to test the sensitivity of ground motion parameters to the seismic wave attenua tion parameters we use two different attenuation models obtained in the study region using weak motion and strong motion databases comparisons are made between the attenuation of synthetics and ground motion prediction equations gmpes synthetic ground motions are further compared with the observed ones in terms of fourier amplitude and response spectra at 21 strong ground motion stations that recorded the mainshock within an epicentral distance of 100 km the spatial distribution of shaking intensity obtained from the did you feel it project and site survey results are compared with the spatial distributions of simulated peak ground motion intensity parameters our results show that despite the limitations of the method in simulating the directivity effects the stochastic finite fault model seems an effective and fast tool to simulate the high frequency portion of ground motions

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

postseismic displacement of the 1999 athens earthquake retrieved by the differential interferometry by synthetic aperture radar time series 1 in september 1999 a moderate mw 5 9 earthquake struck the attica plain causing unexpected and extensive damage to athens and its population in this work we exploit the potential of multitemporal differential interferometry by synthetic aperture radar dinsar analysis using about a hundred european remote sensing ers 1 2 images to calculate the displacement time series from 1992 to 2002 this analysis allows us to clearly separate a strictly coseismic signal from a postseismic gradual subsidence reaching a maximum value of about 3 cm in the following 2 5 years we model this signal in terms of afterslip on the seismogenic fault the afterslip distribution retrieved by linear inversion reflects the coseismic slip distribution and occurs mainly downdip of the area that ruptured during the main shock the analysis of the static stress transfer suggests that the afterslip was triggered by the main shock then it propagated aseismically through the fault plane a partial overlap between the coseismic and aseismic slip area at the hypocentral region indicates that the 1999 rupture surface was not healed at least until the date of the last postseismic image april 2002 the results obtained with a time series approach for this moderate magnitude earthquake suggest that multitemporal dinsar analysis should become an important methodology for the study of large earthquake ruptures

fault extent estimation for near real time ground shaking map computation purposes rapid evaluation of strong ground shaking maps after moderate to large earthquakes is crucial to recognizing those areas where the largest damage and losses are expected these maps play a fundamental role for emergency management this is particularly important for areas having high seismic risk potential and covered by dense seismic networks in near real time applications ground shaking maps are produced by integrating recorded data and estimates obtained by using ground motion predictive equations which assume point source models however particularly for large earthquakes improvements in the predictions of the peak ground motion can be obtained when fault extension and orientation are available in fact detailed source information allows one to use a more robust source to site distance metric compared with hypocentral distance in this paper a technique for estimating both fault extent in terms of its surface projection and dominant rupture direction is presented this technique can be used in near real time ground motion map calculation codes with the aim of improving ground motion estimates with respect to a point source model the model parameters are estimated by maximizing a probability density function based on the residuals between observed and predicted peak ground motion quantities the latter obtained by using predictive equations the model space to be investigated is defined through a bayesian approach and it is explored by a grid searching technique the effectiveness of the proposed technique is demonstrated by offline numerical tests using data from three earthquakes occurring in different seismotectonic environments the selected earthquakes are the 17 august 1999 m w 7 5 kocaeli turkey earthquake the 6 april 2009 m w 6 3 l aquila italy earthquake and the 17 january 1994 m w 6 7 northridge california earthquake the obtained results show that the proposed technique allows for fast and first order estimates of the fault extent and dominant rupture direction which could be used to improve ground shaking map calculations

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

the 2009 april 6 mw 6 3 l aquila central italy earthquake finite fault effects on intensity data summary we analyse the spatial distribution of the intensity data points surveyed after the mw 6 3 2009 l aquila central italy earthquake with the aim to recognize and quantify finite fault and directivity effects the study is based on the analysis of the residuals evaluated with respect to attenuation with distance models calibrated for l aquila earthquake we apply a non parametric approach considering both the epicentral and the rupture distance which accounts for the finite extension of the source then starting from a simplified kinematic rupture model of the l aquila fault we compute four directivity predictors proposed in literature and assess their correlation with intensity residuals we derive a so called intensity directivity factor by the correlation between theoretical predictors and observed residuals that allows us to identify and quantify the intensity data points affected by forward and backward directivity during l aquila earthquake we find that the effects are more pronounced in the forward directivity direction and increments up to 1 mcs intensity unit are expected moreover the directivity predictor that accounts for radiation pattern poorly correlates with residuals these results show that the spatial distribution of the l aquila macroseismic field is affected by source effects and in particular that directivity induced amplification effects can be recognized we show that the quasi unilateral rupture propagation along the fault can explain the high intensity patterns observed along specific direction at relatively large distance from the instrumental epicentre in accordance with the seismological source models derived from the analysis of instrumental observations

clues for a relation between rotational effects induced by the 2009 mw 6 3 l aquila central italy earthquake and site and source effects abstract the 2009 m w 6 3 l aquila earthquake produced an impressive number of rotational effects on vertically organized objects such as chimneys pillars capitals and gravestones we present a dataset of such effects that consists of 105 observations at 37 different sites and represents a compendium of earthquake induced instances of rotational effects that is unprecedented in recent times we find that the absolute majority of the reported effects were observed in the epicentral zone and that most of the observations are located where the mercalli cancani sieberg intensity is between 7 and 8 9 the evident asymmetry in the distribution of the rotational effects resembles the southeastward directivity of the macroseismic effects and highlights a significant convergence between rotations and damage finally we perform some qualitative analyses to recognize and evaluate which geological and seismological parameters can be significant contributors to local rotations we find that surface geology and amplification of the seismic motion at each reported location strongly influence the occurrence and the nature of the earthquake induced rotational effects conversely the contribution of the pattern of slip distribution on the fault plane plays only a secondary role in enhancing the rotational motion at each site

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

aeromagnetic investigation of southern calabria and the messina straits italy tracking seismogenic sources of 1783 and 1908 earthquakes southern calabria and the ne corner of sicily italy were struck in 1783 and 1908 a d by two of the most catastrophic earthquakes ever in european history although it is generally acknowledged that the seisms were yielded by normal faults rupturing the upper crust of the calabria peloritani terrane no consensus exists on seismogenic source location and orientation here we report on a high resolution low altitude aeromagnetic survey of southern calabria and messina straits in southern calabria we document a broad weakly positive 5 10 nt anomaly zone interrupted by three en echelon sw ne null to negative magnetic anomaly corridors euler deconvolution and magnetic modeling show that the anomaly pattern is produced by a 1 1 5 km thick crustal layer located within 3 km depth this layer is offset by a 25 km long ne trending fault that corresponds to the armo normal fault recently inferred to be the source for the 1908 earthquake few kilometers to the south we also document a subparallel and previously unrecognized fault entering the messina straits and likely joining the armo fault at depth further east we model a 40 km long normal fault probably extending northeastward for additional 40 km running along the south calabria axis from aspromonte to the serre mountains and partly following the 18 km long surface rupture witnessed by deodat de dolomieu after the 1783 earthquake thus aeromagnetic data suggest that the sources of the 1783 and 1908 earthquakes are en echelon faults belonging to the same nw dipping normal fault system straddling the whole southern calabria

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

aftershock patterns and main shock faulting we have compared aftershock patterns following several moderate to large earthquakes with the corresponding distributions of coseismic slip obtained from previous analyses of the recorded strong ground motion and teleseismic waveforms well located aftershock hypocenters are projected onto the main shock fault plane and their positions are examined relative to the zones of coseismic displacement indicated by the estimated distributions of main shock slip we also examine the aftershock focal mechanisms when these data are available in an attempt to identify possible patterns of secondary faulting within the aftershock zone our results are consistent with a hypothesis of aftershock occurrence that requires a secondary redistribution of stress following primary failure on the earthquake fault aftershocks following the earthquakes examined in this study occur mostly outside of or near the edges of the source areas indicated by the patterns of main shock slip the spatial distribution of aftershocks reflects either a continuation of slip in the outer regions of the areas of maximum coseismic displacement or the activation of subsidiary faults within the volume surrounding the boundaries of main shock rupture

the 2009 l aquila mw 6 3 earthquake a new technique to locate the hypocentre in the joint inversion of earthquake rupture process summary a new technique is presented to jointly invert the teleseismic and interferometric synthetic aperture radar insar data by simultaneously searching for the hypocentre and the relative weight of insar data in this technique the parameters of causative fault is determined by using insar data first and then the hypocentre is searched for by jointly inverting teleseismic and insar data with the assumption that each subfault on the fault is a potential hypocentre with this technique we investigated the source rupture process of the 2009 april 6 l aquila mw 6 3 earthquake without the use of the existing hypocentre locations our estimated hypocentre is 42 366 n 13 385 e depth 6 9 km with an uncertainty of 1 2 km similar to the hypocentre 42 348 n 13 380 e depth 9 5 km determined by national institute of geophysics and volcanology ingv using arrival time data within the epicentral distance of 50 km our joint inversion suggests a scalar moment of 3 5 1018 nm equivalent to a moment magnitude of mw 6 3 the source process consists of two subevents with a total duration of 7 7 s the first event 0 3 s corresponds to the slip patch near the hypocentre and the second in the next 4 7 s ruptured the other slip patch at 4 16 km along the strike direction these unilateral rupture characteristics of the l aquila earthquake are confirmed by the apparent source time functions astfs analysis in addition two resolution tests are performed to check the reliability of this work clarifying the differences between the inversion results with teleseismic data only insar data only and joint inversion indicating that a higher resolution can be achieved through the joint inversion

time lapse imaging of coseismic ruptures for the 2019 ridgecrest earthquakes using multiazimuth backprojection with regional seismic data and a 3 d crustal velocity model

occurrence of partial and total coseismic ruptures of segmented normal fault systems insights from the central apennines italy abstract normal faulting earthquakes rarely rupture the entire extent of active normal faults and can also jump between neighbouring faults this confounds attempts to use segmentation models to define the likelihood of future rupture scenarios we attempt to study this problem comparing the offsets produced in single earthquakes with those produced by multiple earthquakes over longer timescales together with detailed studies of the structural geology we study the active normal fault system that caused the mw 6 3 2009 l aquila earthquake in central italy comparing the spatial distribution of coseismic offsets cumulative offsets that have developed since 15 3 ka and the total offsets that have accumulated since the faults initiated at 2 3 ma our findings suggest that 1 faults within a segmented fault system behave as a single interacting fault segment over time periods including multiple earthquake cycles e g 2 3 ma or 15 3ka with single earthquakes causing either partial or total ruptures of the entire system 2 an along strike bend causes throw and throw rates enhancements within the bend throughout the seismic history of the fault system we discuss the synchronised and geometrically controlled activity rates on these faults in terms of the propensity for floating earthquakes multi fault earthquakes and seismic hazard

radar interferogram filtering for geophysical applications the use of sar interferometry is often impeded by decorrelation from thermal noise temporal change and baseline geometry power spectra of interferograms are typically the sum of a narrow band component combined with broad band noise we describe a new adaptive filtering algorithm that dramatically lowers phase noise improving both measurement accuracy and phase unwrapping while demonstrating graceful degradation in regions of pure noise the performance of the filter is demonstrated with sar data from the ers satellites over the jakobshavns glacier of greenland

graviquakes in italy abstract we discuss the mechanics of crustal normal fault related earthquakes and show that they represent dissipation of gravitational potential energy graviquakes and their magnitude increases with the involved volume delimited by the seismogenic fault and an antithetic dilated wedge in its hangingwall and the fault dip the magnitude increases with the deepening of the brittle ductile transition bdt which in turn enlarges the involved volume the fault dip seems rather controlled by the static friction of the involved crustal layers we apply the model to the extensional area of the italian peninsula whose geodynamics is controlled by the alpine and apennines subduction zones the latter has a well developed backarc basin and a large part of the accretionary prism is affected by on going extensional tectonics which is responsible for most of peninsular italy seismicity analyzing the seismic record of the apennines the length of seismogenic normal faults tends to be at most about 3 times the hypocenter depth we compile a map of the brittle ductile transition depth and assuming a fixed 45 or 60 fault dip and a dilated wedge developed during the interseismic period almost perpendicular to the fault plane we compute the maximum volume of the hangingwall collapsing at the coseismic stage and estimate the maximum expected magnitude lower magnitude values are obtained in areas with thinner brittle layer and higher heat flow moreover lower magnitude relative to those theoretically expected may occur in areas of higher strain rate where faults may creep faster due to lower frictional values

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

normal faults and thrusts reactivated by deep fluids the 6 april 2009 mw 6 3 l aquila earthquake central italy 1 on 6 april 2009 a mw 6 3 earthquake occurred in the central apennines italy damaging the city of l aquila and the surrounding country we relocate the october 2008 to 6 april 2009 foreshocks and about 2000 aftershocks occurred between 6 and 30 april 2009 by applying a double difference technique and determine the stress field from focal mechanisms the events concentrate in the upper 15 km of the crust three main nw se to nnw sse striking 30 45 and 80 90 dipping faults were activated during the seismic sequence among these a normal fault and a thrust were reactivated with dip slip movements in response to ne sw extension the structural maturity of the seismogenic fault system is lower than that displayed by other systems in southern apennines because of the lower strain rate of the central sector of the chain with respect to the southern one vp vs increases progressively from october 2008 to the 6 april 2009 main shock occurrence along a nw se strike because of an increment in pore fluid pressure along the fault planes pore pressure diffusion controls the space time evolution of aftershocks a hydraulic diffusivity of 80 m2 s 1 and a seismogenic permeability of about 10 12 m2 suggest the involvement of gas rich co2 fluids within a highly fractured medium suprahydrostatic high fluid pressure about 200 mpa at 10 km of depth within overpressurized traps bounded by preexisting structural and or lithological discontinuities at the lower upper crust boundary are required to activate the april 2009 sequence traps are the storage zone of co2 rich fluids uprising from the underlying about 20 km deep metasomatized mantle wedge these traps easily occur in extensional regimes like in the axial sector of apennines but are difficult to form in strike slip regimes where subvertical faults may cross the entire crust in the apennines fluids may activate faults responsible for earthquakes up to mw 5 6 deep fluids more than tectonic stress may control the seismotectogenesis of accretionary wedges

coseismic and postseismic deformation of the 2016 mw 6 2 lampa earthquake southern peru constrained by interferometric synthetic aperture radar

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

new insights into fault activation and stress transfer between en echelon thrusts the 2012 emilia northern italy earthquake sequence here we present the results of the inversion of a new geodetic data set covering the 2012 emilia seismic sequence and the following 1 year of postseismic deformation modeling of the geodetic data together with the use of a catalog of 3 d relocated aftershocks allows us to constrain the rupture geometries and the coseismic and postseismic slip distributions for the two main events mw 6 1 and 6 0 of the sequence and to explore how these thrust events have interacted with each other dislocation modeling reveals that the first event ruptured a slip patch located in the center of the middle ferrara thrust with up to 1 m of reverse slip the modeling of the second event located about 15 km to the southwest indicates a main patch with up to 60 cm of slip initiated in the deeper and flatter portion of the mirandola thrust and progressively propagated postseismically toward the top section of the rupture plane where most of the aftershocks and afterslip occurred our results also indicate that between the two main events a third thrust segment was activated releasing a pulse of aseismic slip equivalent to a mw 5 8 event coulomb stress changes suggest that the aseismic event was likely triggered by the preceding main shock and that the aseismic slip event probably brought the second fault closer to failure our findings show significant correlations between static stress changes and seismicity and suggest that stress interaction between earthquakes plays a significant role among continental en echelon thrusts

abruzzo italy earthquakes of april 2009 heterogeneous fault slip models and stress transfer from accurate inversion of envisat insar data abstract the seismic sequence that occurred in the abruzzo apennines near l aquila italy in april 2009 caused extensive damage and a large number of casualties more than 300 the earthquake struck an area in the italian apennines chain where several faults belonging to adjacent seismotectonic domains create a complex tectonic regime resulting from the interaction among regional stress buildup local stress changes caused by individual earthquakes and viscous elastic stress relaxation understanding such complex interaction in the apennines can lead to a large step forward in the seismic risk mitigation in italy the abruzzo earthquake has been very well recorded by interferometric synthetic aperture radar insar data much better than the first italian earthquake ever recorded by satellites namely the 1997 umbria marche earthquake envisat environmental satellite data for the abruzzo earthquake are in fact very clear and allow an accurate reconstruction of the faulting mechanism we present here an accurate inversion of vertical deformation data obtained by envisat images aimed to give a detailed reconstruction of the fault geometry and slip distribution the resulting fault models are then used to compute by a suitable theoretical model based on the elastic dislocation theory the stress changes induced on the neighboring faults the correlation of the subsequent mainshocks and aftershocks of the abruzzo sequence with the volumes undergoing increasing coulomb stress clearly evidence the triggering effect of coseismic stress changes on further seismicity moreover this analysis put in evidence which seismotectonic domains have been more heavily charged by stress released by the abruzzo mainshocks the most important faults significantly charged by the abruzzo sequence belong to the sulmona and avezzano tectonic domains taking into account the average regional stress buildup in the area the positive coulomb stress changes caused by this earthquake can be seen as anticipating the next earthquakes in the neighboring domains of 15 20 yr