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

seismicity normal faulting and the geomorphological development of the gulf of corinth greece the corinth earthquakes of february and march 1981 three major destructive earthquakes of m s 6 7 6 4 6 4 occurred in the eastern part of the gulf of corinth in february and march 1981 associated normal faulting was observed on both the north and the south sides of the gulf examination of teleseismic local seismic surface faulting and geomorpbological data suggests that the first and second of these shocks activated major north dipping normal faults these faults control the topography and bathymetry and are related to the recent uplift and subsidence of the coastline it is probable that the first earthquake occurred on a faultwhich outcrops underwater and the second on a fault which is visible on land it appears that the third shock activated an antithetic normal fault dipping southwards on the north side of the gulf and that the overall structure of the gulf of corinth graben is asymmetric the northern antithetic fault clearly demonstrates the geomorphological changes associated with developing young normal faulting in addition we suggest that observations of recent coastline movement provide a powerful tool for identifying major active fault systems and predicting their historical role in the paleogeography of an area

fault generated mountain fronts in the central apennines central italy geomorphological features and seismotectonic implications the morphotectonic framework of the central apennines is given by faulted blocks bounded by normal faults mostly trending nw se nnw sse and ne sw which cut previous compressive structures such a structural setting is consistent with the lbcal mechanisms of the earthquakes which often occur in this area in this paper three lithologically different normal fault generated mountain fronts are analysed in order to assess the relations between their geomorphic features and active tectonics they border the norcia depression sibillini mts umbria the amatrice ampotosto plateau laga mts lazio and the fucino basin marsica mts abruzzi the norcia depression is bounded by a n20 w trending normal fault to the east and by a parallel antithetic fault to the west the main fault has a 1000 m throw and gives rise to a wide fault escarpment characterized by l sharp slope breaks due to low angle gravity faults 2 important paleolandslides and 3 several fault scarplets on the piedmont belt affecting quaternary deposits the amatrice ampotosto plateau is delimited by the western slope of mt gorzano which runs along a n20 w trending normal fault having a 1500m throw minor parallel faults dislocate quaternary landforms large scale massmovements also occur here e the fucino basin was struck by th e 1915 avezzano earthquake 0 xi mcs which produced extensive surface faulting along two parallel nw trending normal fault escarpments on the eastern border of the basin there is paleoseismrc evidence including buried gravity graben in late glacial gravels and tectonic dip slip striations on holocene calcitic crusts covering bedrock normal fault planes these data suggest that active extensional tectonics plays a major role in the slope morphogenesis of the central apennines and they indicate the importance of geomorphic analysis in seismic zonation of this area

fault scarps and deformation rates in lazio abruzzo central italy comparison between geological fault slip rate and gps data abstract we compare new and literature data concerning the integrated deformation rate since 18 ka for the central apennines with deformation rate data derived from a 6 year gps campaign we constructed topographic profiles across the majority of the active faults in the area we derived deformation rate data from displaced post glacial sediments and slopes associated with the last major glacial retreat that occurred in the region about 18 kyr ago paleoseismic investigations in this region clearly show that offset of these features is the cumulative effect of repeated surface faulting earthquakes with magnitudes in the range 5 5 ms 7 0 a cumulative throw rate diagram incorporating both our values and the values extracted from the literature i e previously published trenching studies scarp profiles and offset terraces is presented providing a regional picture of the spatial deformation rate distribution in the central apennines during the latest pleistocene and holocene by converting cumulative throw rates into heave rates we calculate maximum extension rates of ca 2 mm year at the location of the same transect where 6 2 mm year has been measured with gps over 6 years this discrepancy between geodetic and geological fault slip rate data implies that we have to be cautious whenever we use gps data for seismic hazard assessment purposes or when attempting to reconstruct the tectonic processes in an area because geodetic data may be unrepresentative of the longer term deformation rates on the other hand this discrepancy may provide insights into the mechanics of the seismic cycle we discuss various scenarios that may explain the mis match between long term and short term measurements

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

erosion of tephra from the 1980 eruption of mount st helens erosion of tephra on hillslopes north of mount st helens was measured at intervals of several months between 1980 and 1983 using large arrays of stakes rill erosion was initially greater than sheetwash but its importance decreased comparatively quickly both rill erosion and sheetwash decreased by one to two orders of magnitude over the three year period because a stable rill network developed and more permeable and less erodible substrates were created or exposed the decrease occurred prior to recovery of plants the causes for the rapid decline in erosion at mount st helens explain patterns of erosion following several other recent tephra eruptions basin wide annual rates of erosion were computed by mapping the surface cover the hillslope gradient and the texture and thickness of tephra and by using statistical relations developed between them and erosion rates annual erosion decreased from 26 mm between may 1980 and may 1981 to 1 8 mm between may 1982 and may 1983 projecting this rate of decline into the future indicated that only about one sixth of the tephra on hillslopes will be removed by water erosion before soil creep and other forms of mass wasting again dominate hillslope evolution

active normal faulting during the 1997 seismic sequence in colfiorito umbria did slip propagate to the surface in order to determine whether slip during an earthquake on the 26th september 1997 propagated to the surface structural data have been collected along a bedrock fault scarp in umbria italy these collected data are used to investigate the relationship between the throw associated with a debated surface rupture observed as a pale unweathered stripe at the base of the bedrock fault scarp and the strike dip and slip vector previous studies have suggested that the surface rupture was produced either by primary surface slip or secondary compaction of hangingwall sediments some authors favour the latter because sparse surface fault dip measurements do not match nodal plane dips at depth it is demonstrated herein that the strike dip and height of the surface rupture represented by a pale unweathered stripe at the base of the bedrock scarp shows a systematic relationship with respect to the geometry and kinematics of faulting in the bedrock the strike and dip co vary and the throw is greatest where the strike is oblique to the slip vector azimuth where the highest dip values are recorded this implies that the throw values vary to accommodate spatial variation in the strike and dip of the fault across fault plane corrugations a feature that is predicted by theory describing conservation of strain along faults but not by compaction furthermore published earthquake locations and reported fault dips are consistent with the analysed surface scarps when natural variation for surface dips and uncertainty for nodal plane dips at depth are taken into account this implies that the fresh stripe is indeed a primary coseismic surface rupture whose slip is connected to the seismogenic fault at depth we discuss how this knowledge of the locations and geometry of the active faults can be used as an input for seismic hazard assessment

fault slip rate variations during crustal scale strain localisation central italy rates of plate motion are generally uniform over 10 102 myrs timescales faults between tectonic plates might therefore be expected to show temporally uniform slip rates if the same number of faults remain active for an extending region of the eurasia africa plate boundary italy finite throw values vertical component of the slip for seismogenic normal faults are less than that predicted when recent throw rates are extrapolated over the fault lifetimes the effect correlates with distance from the fault system tips and demonstrates that the slip rates on centrally located faults have increased with time neighbouring normal faults were active in the quaternary but show no signs of surface faulting during the latest pleistocene to holocene death of these faults has provided the extra strain per unit time to drive the increased slip rates measured on other faults thus fault interaction and death modify slip rates and seismic hazards associated with plate tectonics

single event throws along the delta fault baikal rift reconstructed from ground penetrating radar geological and geomorphological data abstract surface displacement is critical to assess the seismic potential of an active fault its distribution along strike is strongly variable and its detection is sometimes ambiguous in soft and poorly consolidated sediments here we show that ground penetrating radar gpr supported by geological and geomorphological data is effective in revealing the total throw on an active fault including brittle and ductile deformational components we studied throws that occurred along the delta fault during the 1862 tsagan earthquake on lake baikal the motion on that fault was measured along a stepped system of normal ruptures in which the main plane dips to the nw at 56 76 the total throws of holocene sediments from gpr data vary from 1 81 to 9 59 m the contribution of the ductile component to the offset was between 13 and 42 its maximum values correspond to minimum dip values of the main fault plane and the largest widths of the fault damage zone the width also correlates well with the total vertical displacement consequently the structural features of the rupture zone and the variable distribution of offsets in soft sediments of mixed behaviour should be properly considered when estimating the magnitudes of normal fault earthquakes

computer simulation models of scoria cone degradation abstract long term erosional modifications of the relatively simple morphology of scoria cinder cones are ideally suited for study by field and computer simulation methods a series of temporally distinct cones in the san francisco and springerville volcanic fields of arizona provides the foundation for documenting the degradational evolution of scoria cones in a semi arid climate progressive changes due to erosion are illustrated by the systematic decrease with increasing age of various morphometric parameters including scoria cone height cone height width ratio hco wco crater depth width ratio and slope angle for example holocene latest pleistocene cones in the san francisco field have a mean hco wco value of 0 178 0 041 a mean maximum slope angle of 29 7 4 2 and a mean average slope angle of 26 4 7 3 whereas the group of pliocene cones have values of 0 077 0 024 20 5 5 8 and 8 7 2 7 respectively comparative morphology of scoria cones is a potentially useful dating tool for mapping volcanic fields in order to better understand the degradational modifications of these volcanic landforms we have developed a numerical approach to simulate the surficial processes responsible for the erosion of a typical scoria cone the simulation algorithm can apply either a linear diffusion equation model or a model with a nonlinear transport law using a finite difference formulation the simulation operates upon a three dimensional scoria cone input as a matrix of elevation values utilizing both field and model results the correlation between changing hco wco value cone age and computer time step was expressed graphically to derive comprehensive values of the transport or diffusion coefficient df for both volcanic fields for the san francisco volcanic field df had a calculated value of 21 4 m2 kyr for the linear model and 5 3 m kyr for the nonlinear model while for the springerville volcanic field df had a calculated value of 24 4 m2 kyr for the linear model and 6 3 m kyr for the nonlinear model

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

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

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

fault orientation variations along the strike of active normal fault systems in italy and greece implications for predicting the orientations of subseismic resolution faults in hydrocarbon reservoirs the orientations of subseismic scale faults vary systematically along the strike of basin bounding active normal faults in italy and greece a total of 16 272 outcrop measurements of the strike and dip of fault planes and their associated slip vectors indicate oblique slip near the lateral fault tips of the normal faults subseismic faults vary in orientation to accommodate this slip if viewed in map view from the footwall looking toward the hanging wall right lateral slip occurs at the left end of the faults with left lateral slip at the right end overall slip vectors converge toward the hanging wall with intersection lines for faults accommodating this slip parallel to the slip vector if the same faulting style applies elsewhere the empirical relationships presented herein can be used to calibrate results from mechanical fault models and provide a pragmatic guide to the orientations of normal fault bound compartments of rock in subsurface hydrocarbon reservoirs given that the offsets across such faults may be below seismic resolution and not amenable to direct measurement

neotectonics and late holocene paleoseismic evidence in the plio quaternary daroca half graben iberian chain ne spain implications for fault source characterization this work has been supported by project cgl2017 85045 p ministerio de economia industria y competitividad gobierno de espana

sedimentary and tectonic evolution of plio pleistocene alluvial and lacustrine deposits of fucino basin central italy abstract the fucino basin was the greatest lake of the central italy which was completely drained at the end of 19th century the basin is an intramontane half graben filled by plio quaternary alluvial and lacustrine deposits located in the central part of the apennines chain which was formed in upper pliocene and in quaternary time by the extensional tectonic activity the analysis of the geological surface data allows the definition of several stratigraphic units grouped in lower units and upper units the lower units upper pliocene are exposed along the northern and north eastern basin margins they consist of open to marginal lacustrine deposits breccia deposits and fluvial deposits the upper units lower pliocene holocene consist of interbedded marginal lacustrine deposits and fluvial deposits thick coarse grained fan delta deposits are interfingered at the foot of the main relief with fluvial lacustrine deposits most of the thickness of the lacustrine sequences more than 1000 m thick is buried below the central part of the fucino plain the basin is bounded by e w wsw ene and nw se fault systems velino magnola fault e w and tremonti celano aielli fault wsw ene and s potito celano fault nw se in the north the trasacco fault the pescina celano fault and the serrone fault nw se in the south east the geometry and kinematic indicators of these faults indicate normal or oblique movements the study of industrial seismic profiles across the fucino basin gives a clear picture of the subsurface basin geometry the basin shows triangular shaped basin fill geometry with the maximum deposits thickness toward the main east boundary fault zones that dip south westward serrone fault trasacco fault pescina celano fault on the basis of geological surface data borehole stratigraphy and seismic data analysis it is possible to recognize and to correlate sedimentary and seismic facies the bottom of the basin is well recognized in the seismic lines available from the good and continuous signals of the top of meso cenozoic carbonate rocks the shape of sedimentary bodies indicates that the filling of the basin was mainly controlled by normal slip along the nw se boundary faults in fact the continental deposits are frequently in on lap contact over the carbonate substratum several disconformable contacts occurred during the sedimentary evolution of the basin the main faults with antithetic and synthetic fault planes displace the whole sedimentary sequence up to the surface indicating a recent faults activity 1915 avezzano earthquake ms 7 0 the stratigraphic and tectonic setting of the fucino basin and neighboring areas indicates that the extensional tectonic events have had an important role in driving the structural sedimentary evolution of the plio quaternary deposits the geometry of the depositional bodies of the fault planes and their relationships indicate that the fucino basin was formed as a half graben type structure during plio quaternary extensional events some internal complexities are probably related to the fold and thrust structures of the apenninic orogeny formed in messinian time in this area and to a different activity timing of the e w and wsw ene fault systems and the nw se fault systems we believe based on the similarity of the surface characteristics that the structural setting of the fucino basin can be extrapolated to the other great intramontane basins in central italy e g rieti l aquila sulmona sora isernia basins

fault slip directions in central and southern greece measured from striated and corrugated fault planes comparison with focal mechanism and geodetic data fault slip directions recorded by outcropping striated and corrugated fault planes in central and southern greece have been measured for comparison with extension directions derived from focal mechanism and global positioning system gps data for the last 100 years to test how far back in time velocity fields and deformation dynamics derived from the latter data sets can be extrapolated the fault slip data have been collected from the basin bounding faults to plio pleistocene to recent extensional basins and include data from arrays of footwall faults formed during the early stages of fault growth we show that the orientation of the inferred stress field varies along faults and earthquake ruptures so we use only slip directions from the centers of faults where dip slip motion occurs to constrain regionally significant extension directions the fault slip directions for the peloponnese and gulfs of evia and corinth are statistically different at the 99 confidence level but statistically the same as those implied by earthquake focal mechanisms for each region at the 99 confidence level they are also qualitatively similar to the principal strain axes derived from gps studies extension directions derived from fault slip data are 043 047 for the southern peloponnese 353 for the gulf of corinth and 015 014 for the gulf of evia extension on active normal faults in the two latter areas appears to grade into strike slip along the north anatolian fault through a gradual change in fault slip directions and fault strikes to reconcile the above with 5 myr 1 clockwise rotations suggested for the area we suggest that the faults considered formed during a single phase of extension the deformation and formation of the normal fault systems examined must have been sufficiently rapid and recent for rotations about vertical axes to have been unable to disperse the fault slip directions from the extension directions implied by focal mechanisms and gps data thus in central and southern greece the velocity fields derived from focal mechanism and gps data may help explain the dynamics of the deformation over longer time periods than the 100 years over which they were measured this may include the entire deformation history of the fault systems considered a time period that may exceed 1 2 myr

surface faulting accompanying the borah peak earthquake and segmentation of the lost river fault central idaho on the morning of 28 october 1983 the ms 7 3 borah peak earthquake struck central idaho and formed a y shaped zone of surface faults that is divided into a southern a western and a northern section the total length of the surface faults is 36 4 3 1 km and the maximum net throw is 2 5 to 2 7 m the near surface net slip direction determined from the rakes of striations in colluvium averaged 0 17 m of sinistral slip for 1 00 m of dip slip the 20 8 km long southern section is the main zone of surface faulting and coincides with the thousand springs segment of the lost river fault it has the largest amount of net throw most complex rupture patterns and best evidence of sinistral slip the surface faults include zones of ground breakage as much as 140 m wide en echelon scarps with synthetic and antithetic displacements and individual scarps that are nearly 5 m high the 14 2 km long western section diverges away from the lost river fault near the northern end of the southern section the net throw on this section is generally less than 0 5 m but locally is as much as 1 6 m the new ruptures are poorly developed across the crest and north flank of the willow creek hills they are mostly downhill facing arcuate scars perhaps incipient landslides that may overlie a deeper zone of tectonic movement the northern section at least 7 9 km long is on the warm spring segment of the lost river fault and has a maximum net throw of about 1 m the pattern of surface faulting on this section is simple compared to the other sections a 4 7 km long gap in 1983 surface faults separates the northern and southern sections but contains an older scarp of late pleistocene age geologic seismologic and geodetic data from the earthquake suggest that barriers confined the primary coseismic rupture to the thousand springs segment of the fault the rupture propagated unilaterally to the northwest from a hypocenter near the southeastern end of the segment the southeastern boundary of the segment is marked by an abrupt bend in the range front a 4 km long gap in late quaternary scarps and transverse faults of eocene age that intersect the lost river fault the northwestern boundary of the thousand springs segment is at the junction of the willow creek hills and the lost river fault here the southern and western sections of surface faults diverge and there is a gap in the 1983 scarps during the first few weeks after the main shock the large magnitude and large stress drop aftershocks clustered near this barrier later aftershocks were mainly northwest of the barrier on the warm spring and challis segments and showed that strain adjustments eventually affected the entire northern part of the lost river fault fault scarp morphology and the bedrock geology suggest that the boundary between the thousand springs and warm spring segments has probably ruptured less frequently and had less net slip during much of the late cenozoic than the interior of the adjacent segments the 1983 faulting shows that although segment boundaries can stop or deflect primary ruptures secondary surface faulting can occur on adjacent segments of the main fault a late pleistocene scarp in the 1983 gap suggests that infrequent earthquakes perhaps larger than the 1983 event might break through a segment boundary and thus release strain on two adjacent segments

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

computational tools for relaxing the fault segmentation in probabilistic seismic hazard modelling in complex fault systems use of faults in seismic hazard models allows us to capture the recurrence of large magnitude events and therefore improve the reliability of probabilistic seismic hazard assessment psha in the past decades fault segmentation provided an important framework for quantifying fault based psha recent complex coseismic ruptures e g 2010 mw 7 1 canterbury 2012 mw 8 6 sumatra 2016 mw 7 8 kaik ura 2016 mw 6 5 central italy have shown the need to consider different possible combinations of rupture scenarios in psha here we present two new methodologies that model rates of ruptures along complex fault systems one based on a floating rupture approach fresh and another one based on assumed rupture scenarios sunfish they represent alternatives to a recently proposed approach sherifs and further step to overcome the segmented and un segmented approaches commonly used in psha in europe differences among sherifs sunfish and fresh are related to the way slip rate rupture geometries and magnitude frequency distributions are modelled to quantify the differences between these three methodologies we compared psha results based on geometries and slip rates of a fault system located in northeastern italy assuming a given maximum magnitude and the same seismic moment rate target differences up to 20 30 in the peak ground acceleration at 2 and 10 in 50 years are observed finally we show that the three methodologies are able to solve for the long term rate of ruptures with resulting psha that reflect the fault system geometry and slip rates without any assumption on segment boundaries using fault based approaches in psha requires collecting as much local geological information as possible now that multi fault rupture approaches are available simplifying assumptions often made to model complex fault systems uniform slip rate segmentation hypothesis are no longer necessary on the other hand local data collection should be strongly encouraged to better characterize the actual fault slip rate variability and the complex 3d geometries

surface faulting of the 1954 fairview peak ms 7 2 and dixie valley ms 6 8 earthquakes central nevada abstract the 1954 fairview peak earthquake was followed 4 min and 20 sec later by the dixie valley earthquake surface ruptures were distributed among six different faults that define a complex north trending zone 100 km long and over 15 km wide the rupture sequence progressed from south to north the initial event produced a 32 km rupture of right oblique slip along the east dipping fairview fault where the components of right lateral offset and vertical separation reached 2 9 and 3 8 m respectively the northernmost ruptures occurred during the subsequent event along a 46 km portion of the east dipping dixie valley fault where the sense of slip was normal and reached a maximum vertical separation of 2 8 m average surface offset for both events is about 1 2 m the west dipping west gate louderback mountains and gold king faults also ruptured during the earthquake sequence these faults form a complex structural linkage within a 15 km left step that separates the surface traces of the fairview and dixie valley faults the west dipping faults likely played an important role in the redistribution of static stress from the fairview peak earthquake and subsequent triggering of the dixie valley earthquake right lateral offsets of more than a meter occurred along both the west gate and louder back mountains faults slip was limited to normal motion of 1 m or less along the gold king fault the change from right oblique motion along the fairview fault to pure normal motion on the dixie valley fault may reflect the transition from principally northwest extension in the south to more westerly extension in the north alternatively slip at the latitude of the dixie valley fault may be partitioned between pure normal slip along the dixie valley fault and strike slip motion on faults immediately to the west observations of fault dip provide insight to the complex three dimensional geometry of the rupture sequence of particular note a significant section of the dixie valley fault appears to be characterized by dip angles as low as 25 at the surface slip variation or earthquake endpoints do not generally appear to have been influenced by changes in bedrock type we do not observe systematic relations between slip variation and aspects of fault trace geometry such as salients and reentrants yet the relative competence of footwall bedrock appears to have influenced the long term development of large salients and reentrants along both the dixie valley and the fairview faults as well as the style of rupture along the southern portion of the dixie valley fault

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

throw rate variations within linkage zones during the growth of normal faults case studies from the western volcanic zone iceland abstract this work investigates how throw rates vary within fault bends and sites of fault linkage during the process of normal fault growth in the western volcanic zone iceland through detailed field mapping and field measurements of fault throws normal faults are mapped and along strike throw profiles are constructed in order to understand how the throw rates relate with the local fault geometry along faults at different stages of linkage the results show that throw rates increase within linkage zones and propagating fault bends independently from the stage of maturity of the fault bend this implies that 1 the relationship between the local fault geometry and the along strike distribution of throw rate is driven by the deeper part of the fault where established fault bends start propagating to the surface 2 faults grow first by linkage and coalescence of separate faults and then by accumulation of slip on the resultant fault in agreement with models of fault growth by linkage and coalescence 3 incipient fault bends can produce uncertainty associated with palaeoseismological results if fault bends remain unrecognised moreover this work demonstrates that existing models showing increased co seismic and throw rates within fault bends and sites of fault linkage found in continental extensional settings are valid in a geodynamic context of a mid oceanic rifts

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

structure of the michoacan guanajuato volcanic field mexico abstract the distribution and the alignment of volcanoes and fault scarps provide new insights into the structural framework of the michoacan guanajuato volcanic field a total of 1894 volcanoes occur over an area of 34 500 km 2 contour maps of the density of volcanoes and average volcano height indicate a shift from polygenetic to monogenetic volcanism from north to south in the field volcano edifice height has a bimodal density distribution which can be described by two populations with mean heights of 95 m and 510 m plotting the distribution of these two populations on separate contour maps reveals a n35e trend in monogenetic volcanoes and a n60w trend in polygenetic volcanoes fault scarps cut tertiary volcanic rocks and older quaternary volcanoes but are overprinted by volcanoes and lava flows in the central part of the field fault scarps define two fault zones oriented n60e in the northeastern part of the area and n60w in the northwest part of the area e w trending faults are common and alignments of volcanoes often parallel these faults regional trends in volcano distribution appear to be related to plate convergence the n60w trend of the polygenetic volcanoes is colinear to the western trans mexican volcanic arc parallel to the middle america trench and parallel to a major fault zone and represents an extinct volcanic arc the n35e band of monogenetic volcanoes may reflect the segmentation of the subducted plate

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

partitioned postseismic deformation associated with the 2009 mw 6 3 l aquila earthquake surface rupture measured using a terrestrial laser scanner using 3d terrestrial laser scan tls technology we have recorded postseismic deformation on and adjacent to the surface rupture formed during the 6th april 2009 l aquila normal faulting earthquake mw 6 3 using surface modeling techniques and repeated surveys 8 124 days after the earthquake we have produced a 4d dataset of postseismic deformation across a 3 65 m area at high horizontal spatial resolution we detected millimetre scale movements partitioned between discrete surface rupture slip and development of a hangingwall syncline over 10 s of meters we interpret the results as the signal of shallow afterslip in the fault zone we find 52 of the total postseismic hangingwall vertical motion occurs as deformation within 30 m of the surface rupture the total postseismic vertical motions are approximately 50 that of the coseismic we highlight the importance of quantifying partitioned postseismic contributions when applying empirical slip magnitude datasets to infer palaeoearthquake magnitudes

contrasting strike slip motions on thrust and normal faults implications for space geodetic monitoring of surface deformation recent global positioning system gps records of surface deformation caused by earthquakes on intracontinental dip slip faults revealed in unprecedented detail a significant strike slip component near the fault tips that is markedly different for thrust and normal faults in the hanging wall of the thrust fault ruptured during the a d 2003 chengkung taiwan earthquake a divergent displacement pattern was recorded in contrast a convergent slip pattern was observed in the hanging wall of the normal fault that produced the 2009 l aquila italy earthquake such convergent slip patterns are also evident in field records of cumulative fault slip from central italy which underlines the coseismic origin of cumulative displacement patterns here we use three dimensional numerical modeling to demonstrate that the observed fault parallel motions are a characteristic feature of the coseismic slip pattern on normal and thrust faults modeled slip vectors converge toward the center of normal faults whereas they diverge for thrust faults this causes contrasting fault parallel displacements at the model surface our model also predicts divergent movements in normal fault footwalls which were recorded for the first time during the l aquila earthquake during the postseismic phase viscous flow in the lower crust induces fault parallel surface displacements which have the same direction as the coseismic displacements but are distributed over a larger area that extends far beyond the fault tips therefore detecting this signal requires gps stations in the prolongation of the fault strike postseismic velocities vary over several orders of magnitude depending on the lower crustal viscosity and may reach tens of millimeters per year for low viscosities our study establishes the link between coseismic and cumulative slip patterns on normal and thrust faults and emphasizes that understanding fault parallel slip components and associated surface displacements is essential for inferring regional deformation patterns from space geodetic and fault slip data

pre existing cross structures and active fault segmentation in the northern central apennines italy abstract the multideformed axial zone of the apennines provides a great opportunity to explore the influence of pre existing cross structures inherited from pre quaternary tectonic phases on the segmentation of quaternary active seismogenic extensional faults detailed geological and structural data and their comparison with seismological data show that although the attitudes strike and dip of oblique pre existing faults are certainly an important factor in determining a segment boundary the size of the inherited oblique structures seems to be more crucial pre existing cross structures with lengths ranging from several kilometers to a few tens of kilometers show a twofold behavior they can act as segment barriers during the rupture of a single fault segment or they can be reactivated as transfer zones inducing the activation of two adjacent segments that belong to the same fault system regional basement crustal oblique pre existing cross structures with lengths ranging from several tens of kilometers to hundreds of kilometers commonly nne striking may act as persistent structural barriers that halt both fault segment and fault system propagation thus determining their terminations and maximum sizes in the northern central apennines the nne striking ancona anzio valnerina and ortona roccamonfina tectonic lineaments although having been repeatedly reactivated since the mesozoic represent the most important examples of these structures moreover probably due to their misorientation with respect to the present extensional stress field regional nne striking pre existing structures appear to be less likely to produce strong magnitude events no surface evidence for quaternary faulting has been found thus far and historical and instrumental seismicity shows only m m 7 event on the other hand is more likely to occur along the n nw s se trending normal fault systems lastly we propose a model that can explain the different sizes of fault segments and fault systems on the basis of their location with respect to the persistent structural barriers and their spacing in this view our results may contribute to a more reasonable assessment of the nature and size of future surface ruptures in the northern central apennines which are of critical importance to estimating seismic hazard

earthquake scaling fault segmentation and structural maturity abstract slip and length measurements on earthquakes suggest large stress drop variability we analyze an extended set of slip length measurements for large earthquakes m 6 to seek for the possible origin s of this apparent variability we propose that such variability arises from earthquakes breaking a variable number of major fault segments that number depends on the strength of the inter segment zones which itself depends on the structural maturity of the faults we propose new d max l parameterizations based on that idea of multiple segment ruptures in such parameterizations each broken segment roughly scales as a crack while the total multi segment rupture does not stress drop on individual segments is roughly constant only varying between 3 5 to 9 mpa the slight variation that is still observed depends on fault structural maturity more mature faults have lower stress drops than immature ones the new d max l functions that we propose reduce uncertainties with respect to available relationships they thus provide a more solid basis to estimate seismic hazard by integrating fault properties revealed by geological studies

high resolution field mapping and analysis of the august october 2016 coseismic surface faulting central italy earthquakes slip distribution parameterization and comparison with global earthquakes

layered seismogenic source model and probabilistic seismic hazard analyses in central italy we defined a seismogenic model for central italy based on three layers of sources and computed the relative seismic hazard maps one layer is constituted by individual structures liable to generate major earthquakes m 5 5 we defined them as seismogenic boxes by using geological information in terms of plan projec tion of active faults the seismicity rates associated with an individual source are based on the geometry and kinematics of the fault the recurrence model is controlled by the earthquake source association and when possible we defined the occurrence time of the last major event using it in a time dependent approach another layer is given by the instrumental seismicity analysis of the past two decades which allows us to evaluate the background seismicity m 5 5 using a sliding window selec tion of events we defined a model of regular adjacent cells of variable a and b values of the gutenberg richter relation the last layer utilizes all the instrumental earth quakes and the historical events not correlated to known structures 4 5 m 6 by separating them into seismotectonic provinces shaped on a geological structural basis the seismic hazard computations first use this layered model in a traditional probabilistic scheme the results indicate a narrow belt of peak ground acceleration pga higher than 0 30g with standard deviation in attenuation functions in the axial part of the apennine chain with a maximum spot of pga 0 40g southeast of the area damaged by the 1997 1998 umbria marche sequence pga expected not to be exceeded in 50 years at 90 probability level the background seismicity gives a nonnegligible contribution to the hazard at least for first damage levels then a simplified time dependent hypothesis has been introduced for the individual sources alone computing the conditional probability of occurrence of characteristic earth quakes for each source by brownian passage time distributions adopting equivalent fictitious seismicity rates we obtained maps referring to the next 50 years by using traditional codes these results show that the contribution of the recently active sources vanishes and the most hazardous sites are now located south of l aquila and in the sulmona area we consider that the methodology and results obtained are useful for seismic risk reduction strategies

coseismic throw variation across along strike bends on active normal faults implications for displacement versus length scaling of earthquake ruptures fault bends and associated changes in fault dip play a key role in explaining the scatter in maximum offset versus surface rupture length fault scaling relationships detailed field measurements of the fault geometry and magnitude of slip in the 2016 2017 central italy earthquake sequence alongside three examples from large historical normal faulting earthquakes in different tectonic settings provide multiple examples in which coseismic throw increases across bends in fault strike where dip also increases beyond what is necessary to accommodate a uniform slip vector coseismic surface ruptures produced by two mainshocks of the 2016 2017 central italy earthquake sequence 24 august 2016 mw 6 0 and 30 october 2016 mw 6 5 cross a 0 83 km amplitude along strike bend and the coseismic throws for both earthquakes increase by a factor of 2 3 where the strike of the fault changes by 28o and the dip increases by 20 25o we present similar examples from historical normal faulting earthquakes 1887 sonora earthquake mw 7 5 1981 corinth earthquakes mw 6 7 6 4 and 1983 borah peak earthquake mw 7 3 we demonstrate that it is possible to estimate the expected change in throw across a bend by applying equations that relate strike dip and slip vector to horizontal strain conservation along a nonplanar fault for a single earthquake rupture the calculated slip enhancement in bends can explain much of the scatter in maximum displacement dmax versus surface rupture length scaling relationships if fault bends are unrecognized they can introduce variation in dmax that may lead to erroneous inferences of stress drop variability for earthquakes and exaggerate maximum earthquake magnitudes derived from vertical offsets in paleoseismic data sets

viscous roots of active seismogenic faults revealed by geologic slip rate variations viscous flow in the deep crust and uppermost mantle can contribute to the accumulation of strain along seismogenic faults in the shallower crust1 it is difficult to evaluate this contribution to fault loading because it is unclear whether the viscous deformation occurs in localized shear zones or is more broadly distributed2 furthermore the rate of strain accumulation by viscous flow has a power law dependence on the stress applied yet there are few direct estimates of what the power law exponent is over the long term for active faults here we measure topography and the offset along fault surfaces created during successive episodes of slip on seismically active extensional faults in the italian apennines during the holocene epoch we show that these data can be used to derive a relationship between the stress driving deformation and the fault strain rate averaged over about 15 thousand years kyr we find that this relationship follows a well defined power law with an exponent in the range of 3 0 3 3 1 this exponent is consistent with nonlinear viscous deformation in the deep crust and crucially strain localization promoted by seismogenic faulting at shallower depths although we cannot rule out some distributed deformation we suggest that fault strain and thus earthquake recurrence in the apennines is largely controlled by viscous flow in deep localized shear zones over many earthquake cycles

relationship between topography rates of extension and mantle dynamics in the actively extending italian apennines to investigate the mechanism driving active extension in the central and southern italian apennines and the geography of seismic hazard we compare spatial variations in upper crustal strain rate measured across exposed fault scarps since 15 3 ka with data on cumulative upper crustal strain and topographic elevation and free air gravity p wave tomography and sks splitting delay times that are a proxy for strain in the mantle high extensional strain rates across the apennines since 15 3 ka 0 4 3 1 mm yr along 90 km transects occur in two areas lazio abruzzo se campania and basilicata where values for finite extensional strains that have developed since 2 3 ma are highest 2 7 km cumulative throw and where mean elevation in 5 90 km ne sw boxes is 600 m the intervening area nw campania and molise with 600 m mean elevation in 5 90 km boxes has extension rates 0 4 mm yr and lower values for finite extensional strains 2 km cumulative throw these two areas with high upper crustal strain rates overlie mantle that has relatively long spatially interpolated sks delay times 1 2 1 8 s indicating relatively high mantle strains and free air gravity values 140 160 mgals the intervening area of lower extension rate has shorter spatially interpolated sks delay times 0 8 1 2 s and lower free air gravity values 120 mgals the two areas with high upper crustal strain rates and strain mean elevation and mantle strain coincide with the northern and southern edges of a slab window in the tyrrhenian apennines subducting plate that has been inferred from published p wave tomography together these correlations suggest that dynamic support of the topography by mantle flow through the slab window may control the present day upper crustal strain rate field in the apennines and the geography of seismic hazard in the region

fault segmentation new concepts from the wasatch fault zone utah usa the question of whether structural segment boundaries along multisegment normal faults such as the wasatch fault zone wfz act as persistent barriers to rupture is critical to seismic hazard analyses we synthesized late holocene paleoseismic data from 20 trench sites along the central wfz to evaluate earthquake rupture length and fault segmentation for the youngest 3 ka and best constrained earthquakes differences in earthquake timing across prominent primary segment boundaries especially for the most recent earthquakes on the north central wfz are consistent with segment controlled ruptures however broadly constrained earthquake times dissimilar event times along the segments the presence of smaller scale subsegment boundaries and areas of complex faulting permit partial segment and multisegment e g spillover ruptures that are shorter 20 40 km or longer 60 100 km than the primary segment lengths 35 59 km we report a segmented wfz model that includes 24 earthquakes since 7 ka and yields mean estimates of recurrence 1 1 1 3 kyr and vertical slip rate 1 3 2 0 mm yr for the segments however additional rupture scenarios that include segment boundary spatial uncertainties floating earthquakes and multisegment ruptures are necessary to fully address epistemic uncertainties in rupture length we compare the central wfz to paleoseismic and historical surface ruptures in the basin and range province and central italian apennines and conclude that displacement profiles have limited value for assessing the persistence of segment boundaries but can aid in interpreting prehistoric spillover ruptures our comparison also suggests that the probabilities of shorter and longer ruptures on the wfz need to be investigated

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

stripping of keanakakoi tephra on kilauea volcano hawaii morphological characteristics erosional processes and effects of burial and exhumation by debris mantles on basaltic volcanic landforms have been evaluated through field study of the keanakakoi formation a basaltic tephra formed in 1790 by phreato magmatic eruptions from kilauea caldera hawaii the upper coarse lithic intermediate fine vitric and lower mixed members of this formation play different roles in the creation of micro terrain elements during stripping of tephra from the underlying bedrock of the seven micro terrain elements defined bedrock scabby upland surfaces and lag gravels are the most distinctive and widely distributed different proportions and combinations of micro terrain elements define five zones of progressive deterioration of the keanakakoi tephra blanket southwestward from kilauea caldera into the kau desert fluvial and eolian processes operate on different time scales and at different locations governed by blanket thickness debris caliber and the formation of case hardened crusts stripping of an entire mantle is probably not possible however materials trapped within depressions form the only clearly discernible morphological expression of previously more extensive debris blankets

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

coseismic and postseismic subsurface displacements and strains for a dip slip normal fault in a three layer elastic gravitational medium a three layer elastic gravitational fault displacement model has been developed using elastic dislocation and employed to examine the effects of rigidity layering gravity and stress relaxation on surface and subsurface displacements fields for a dip slip normal fault within our three layer model layer 1 represents the upper crust layer 2 the lower crust and layer 3 the upper mantle the fault is embedded in the upper crust horizontal as well as vertical displacement components have been determined displacement field changes due to postseismic stress relaxation have been calculated using both the correspondence principle and relaxed rigidity moduli and results are in close agreement the relaxed rigidity method provides an accurate and computationally efficient method of examining postseismic relaxation postseismic relaxation within the lower two layers only gives surface uplift increasing footwall uplift and decreasing hangingwall subsidence and also increases the wavelength of surface vertical displacement postseismic stress relaxation within all three layers i e uniform half space produces a shorter wavelength of surface vertical deformation with respect to the coseismic response moho topography created during coseismic deformation is initially amplified during postseismic relaxation the relaxed moho topography is dependent on the strength of the upper crust as well as the strength of the lower crust and mantle gravity has a significant influence on displacements only at the postseismic stage when the effective rigidity of the lower layers is small coseismic and postseismic normal strains associated with dip slip normal faulting have been examined for a large normal basement fault intersecting the free surface the coseismic horizontal surface strain perpendicular to fault strike is compressive adjacent to the fault and in the footwall and tensile in the hangingwall away from the fault coseismic stress redistribution may generate significant tensile brittle failure of the upper crust adjacent to large basement faults

displacement and geometrical characteristics of earthquake surface ruptures issues and implications for seismic hazard analysis and the process of earthquake rupture there now exist about three dozen historical earthquakes for which in vestigators have constructed maps of earthquake rupture traces accompanied by de scriptions of the coseismic slip observed along the fault strike the maps and slip distributions are compiled here to place observational bounds on aspects of seismic hazard analysis and fault mechanics analysis leads to an initial statistical basis to predict the end points of rupture and the amount of surface slip expected at sites along the strike during earthquakes on mapped faults the observations also give support to the ideas that there exists a process zone or volume of about 3 4 km in dimension at the fronts of large laterally propagating earthquake ruptures within which stress changes may be sufficient to trigger slip on adjacent faults and that the ultimate length of earthquake ruptures is controlled primarily by the geometrical complexity of fault traces and variations in accumulated stress levels along faults that arise due to the location of past earthquakes to this may be added the observation that the form of earthquake surface slip distributions is better described by asymmetric rather than symmetric curve forms and that earthquake epicenters do not appear to correlate in any systematic manner to regions of maximum surface slip observed along strike online material maps of surface ruptures digitized values and curve fits to surface slip distributions and notes and references for tables 1 and 2

uncertainty in strain rate from field measurements of the geometry rates and kinematics of active normal faults implications for seismic hazard assessment abstract multiple measurements of the geometry kinematics and rates of slip across the auletta fault campania italy are presented and we use these to determine 1 the spatial resolution of field measurements needed to accurately calculate a representative strain rate 2 what aspects of the geometry and kinematics would introduce uncertainty with regard to the strain rate if not measured in the field we find that the magnitude of the post last glacial maximum throw across the fault varies along strike if such variations are unnoticed different values for a representative strain rate hence different results in seismic hazard calculations would be produced to demonstrate this we progressively degrade our dataset calculating the implied strain rate at each step excluding measurements can alter strain rate results beyond 1 uncertainty thus we urge caution when using only one measurement of slip rate for calculating hazard we investigate the effect of approximating the throw profile along the fault with boxcar and triangular distributions and show that this can underestimate or overestimate the strain rate with results in the range of 72 237 of our most detailed strain rate calculation we discuss how improved understanding of the potential implied errors in strain rate calculations from field structural data should be implemented in seismic hazard calculations

monogenetic volcanism personal views and discussion monogenetic volcanism produces small volume volcanoes with a wide range of eruptive styles lithological features and geomorphic architectures they are classified as spatter cones scoria or cinder cones tuff rings maars maar diatremes and tuff cones based on the magma water ratio dominant eruption styles and their typical surface morphotypes the common interplay between internal such as the physical chemical characteristics of magma and external parameters such as groundwater flow substrate characteristics or topography plays an important role in creating small volume volcanoes with diverse architectures which can give the impression of complexity and of similarities to large volume polygenetic volcanoes in spite of this volcanic facies complexity we defend the term monogenetic volcano and highlight the term s value especially to express volcano morphotypes this study defines a monogenetic volcano a volcanic edifice with a small cumulative volume typically 1 km3 that has been built up by one continuous or many discontinuous small eruptions fed from one or multiple magma batches this definition provides a reasonable explanation of the recently recognized chemical diversities of this type of volcanism

geomorphic significance of postglacial bedrock scarps on normal fault footwalls the existence of well preserved holocene bedrock fault scarps along active normal faults in the mediterranean region and elsewhere suggests a dramatic reduction in rates of rock weathering and erosion that correlates with the transition from glacial to interglacial climate we test and quantify this interpretation using a case study in the italian central apennines holocene rates are derived from measurements of weathering pit depth along the magnola scarp where previous cosmogenic cl 36 analyses constrain exposure history to estimate the average hillslope erosion rate over similar to 10 5 years we introduce a simple geometric model of normal fault footwall slope evolution the model predicts that the gradient of a weathering limited footwall hillslope is set by fault dip angle and the ratio of slip rate to erosion rate if either slip or erosion rate is known the other can be derived applying this model to the magnola fault yields an estimated average weathering rate on the order of 0 2 0 4 mm yr more than 10 times higher than either the holocene scarp weathering rate or modern regional limestone weathering rates a numerical model of footwall growth and erosion in which erosion rate tracks the oxygen isotope curve reproduces the main features of hillslope and scarp morphology and suggests that the hillslope erosion rate has varied by about a factor of 30 over the past one to two glacial cycles we conclude that preservation of carbonate fault scarps reflects strong climatic control on rock breakdown by frost cracking

comparison of earthquake strains over 102 and 104 year timescales insights into variability in the seismic cycle in the central apennines italy in order to study the existence of possible deficits or surpluses of geodetic and earthquake strain in the lazio abruzzo region of the central apennines compared to 15 3 kyrs multi seismic cycle strain rates horizontal strain rates are calculated in 5 km x 5 km and 20 km x 20 km grid squares using slip vectors from striated faults and offsets of late pleistocene holocene landforms and sediments strain rates calculated over 15 3 kyrs within 5 km x 5 km grid squares vary from zero up to 2 34 0 54 x 10 7 yr 1 and resolve variations in strain orientations and magnitudes along the strike of individual faults surface strain rates over a time period of 15 3 kyrs from 5 km x 5 km grid squares integrated over an area of 80 km x 160 km shows the horizontal strain rate of the central apennines is 1 18 0 04 0 12 x10 8 yr 1 and 1 83 4 43 3 80 x 10 10 yr 1 parallel and perpendicular to the regional principal strain direction 043 degrees 223 degrees 1 degrees associated with extension rates of ms 6 0 magnitude historical earthquakes have been reported to be as low as zero this demonstrates the importance of comparing the exact same areas and that strain rates vary spatially on the length scale of individual faults and on a timescale between 10 2 yr and 10 4 yr in the central apennines we use these results to produce a fault specific earthquake recurrence interval map and discuss the regional deformation related to plate boundary and sub crustal forces temporal earthquake clustering and the natural variability of the seismic cycle

morphometric and morphological development of holocene cinder cones a field and remote sensing study in the tolbachik volcanic field kamchatka article i nfo the evolution of landscape over time is a central aspect of geological paleogeographical and geomorphological studies volcanic features like cinder cones offer the opportunity to monitor the processes and development of the landscape cinder cones are perhaps the simplest and most common volcanic landforms in the world morphological and morphometric study of cinder cones has proven an efficient tool for determining their relative dates and the erosional processes affecting them the extensive kamchatka volcanic province russian far east with its large tolbachik cinder cone field is an excellent case study for spatial and temporal classification and calibration of changes in morphometric values with time we show how the morphological and morphometric values of the monogenetic cinder cones measured in the field and by digital elevation models can be used to validate their age and erosional processes field data were gps measurements of cinder cones formed at the tolbachik 1975 1976 eruption and of holocene cinder cones erosion processes on the cinder cones and lava flows were identified and evaluated for every studied cinder cone morphometric parameters were assessed on the basis of remotely sensed data and digital elevation model morphometric measurements were taken of cone height and slope and average axis diameter and the height width ratio was obtained the comparison of morphometric parameters calculated from aster dem and topographic map clearly supports the concept of relative morphometric dating as the most recent cinder cones are always associated with the highest slopes and h w ratio the measured morphometric values of the recent tolbachik cinder cones are valuable benchmark data for determining erosion rates such as the measured values for the paricutin cone in mexico after the 1943 eruption the variability of the morphometric values of the recent cinder cones is due to their lithological coarse composition a comparison with the older cinder cones in the area shows that the climatic conditions of the kamchatka peninsula and the slow development of vegetation cover determine a high rate of erosion and rapid change in the morphometric values as compared to published values for other volcanic fields

twenty years of paleoseismology in italy abstract italy has one of the most complete and historically extensive seismic catalogues in the world due to a unique and uninterrupted flow of written sources that have narrated its seismic history since about the end of the iron age seismic hazard studies have therefore always been mainly based upon this huge mass of data nevertheless the italian catalogue probably lacks many m 6 5 events the seismogenetic structures responsible for which are characterized by recurrence times that are longer than the time span covered by our historical sources for these reasons and as in other countries earthquake data that in italy have been derived from paleoseismological studies should finally become a necessary ingredient in seismic risk assessment indeed over the past 20 years some hundred trenches have been excavated supplying reliable and conclusive data on the recent activities of many faults through to many robust datings of surface fault events these studies have provided the ages of several unknown or poorly known m 6 5 earthquakes here we summarize the state of the art of paleoseismology in italy and present a first catalogue of 56 paleoearthquakes pci that occurred mainly in the past 6 kyr the pci integrates the historical instrumental seismic catalogue and extends it beyond the recurrence time of the seismogenetic faults 2000 1000 yr we feel confident that the use of the pci will enhance future probabilistic seismic hazard assessment and thus contribute to more reliable seismic risk mitigation programs

comparison of surface slip and focal mechanism slip data along normal faults an example from the eastern gulf of corinth greece abstract focal mechanism and surface slip data are used to investigate whether kinematics are similar at depth and at the surface along an active normal fault in the gulf of corinth greece we present a new database of slip data from the lateral termination of the south alkyonides fault segment safs and the en echelon stepover between it and an adjacent fault and use published data on surface slip and focal mechanism data pertaining to slip at depth during the 1981 alkyonides earthquake sequence the focal mechanisms exhibit similar fault plane orientations and kinematics to those measured at the surface within the stepover both data sets show that contemporaneous c n s and c e w extension is being accommodated by c e w and c n s oriented normal faults and the overall deformation is distributed oblate vertical flattening the deviation of the surface slip direction from 350 increases with distance from the centre of the safs the deviation of the focal mechanism t axes from 350 fit well with the surface data implying that the coseismic slip on the safs at depths of 7 10 km exhibits a similar kinematic pattern as that observed at the surface our results imply that it is critical to know the along strike position of data on a fault if either focal mechanisms or surface slip are to be used to infer regional strain and stress trajectories

distributed normal faulting in the tip zone of the south alkyonides fault system gulf of corinth constrained using 36cl exposure dating of late quaternary wave cut platforms abstract the geometry rates and kinematics of active faulting in the region close to the tip of a major crustal scale normal fault in the gulf of corinth greece are investigated using detailed fault mapping and new absolute dating fault offsets have been dated using a combination of 234u 230th coral dates and in situ 36cl cosmogenic exposure ages for sediments and wave cut platforms deformed by the faults our results show that deformation in the tip zone is distributed across as many as eight faults arranged within 700 m across strike each of which deforms deposits and landforms associated with the 125 ka marine terrace of marine isotope stage 5e summed throw rates across strike achieve values as high as 0 3 1 6 mm yr values that are comparable to those at the centre of the crustal scale fault 2 3 mm yr from holocene palaeoseismology and 3 4 mm yr from gps geodesy the relatively high deformation rate and distributed deformation in the tip zone are discussed in terms of stress enhancement from rupture of neighbouring crustal scale faults and in terms of how this should be considered during fault based seismic hazard assessment

the geomorphological evolution of the paricutin cone and lava flows mexico 1943 1990 abstract erosion and sedimentation processes in the paricutin cone and adjacent lava fields have been evaluated 47 years after the eruption through field study of the morphological characteristics of the area previous studies indicate an initial stage of accelerated erosion decreasing quickly after the stripping of the ash layers and cessation of the volcanic activities in the cone and crater area revegetation is the main process after the first stage of stripping of fine ash the lava fields are the least affected areas by erosional processes with vegetation development in minor depressions crevices and along the edges of the lava flows the llanos or lava dammed plains are the most active physiographic units with continuous deposition of sediments they are completely covered by vegetation or under agricultural use incision of channels along the lava field edge promotes the integration of the drainage system but still most of the affected area drains into the lave field present erosion rates are higher than normal rates and a complete rehabilitation of the pyroclastic area may extend over decades filling of sediments and revegetation of the lava fields will develop in a longer period of several millennia

a spatiotemporal clustering model for the third uniform california earthquake rupture forecast ucerf3 etas toward an operational earthquake forecast we the ongoing working group on california earthquake probabilities present a spatiotemporal clustering model for the third uniform california earthquake rupture forecast ucerf3 with the goal being to represent aftershocks induced seismicity and otherwise triggered events as a potential basis for operational earthquake forecasting oef specifically we add an epidemic type aftershock sequence etas component to the previously published time independent and long term time dependent forecasts this combined model referred to as ucerf3 etas collectively represents a relaxation of segmentation assumptions the inclusion of multifault ruptures an elastic rebound model for fault based ruptures and a state of the art spatiotemporal clustering component it also represents an attempt to merge fault based forecasts with statistical seismology models such that information on fault proximity activity rate and time since last event are considered in oef we describe several unanticipated challenges that were encountered including a need for elastic rebound and characteristic magnitude frequency distributions mfds on faults both of which are required to get realistic triggering behavior ucerf3 etas produces synthetic catalogs of m 2 5 events conditioned on any prior m 2 5 events that are input to the model we evaluate results with respect to both long term 1000 year simulations as well as for 10 year time periods following a variety of hypothetical scenario mainshocks although the results are very plausible they are not always consistent with the simple notion that triggering probabilities should be greater if a mainshock is located near a fault important factors include whether the mfd near faults includes a significant characteristic earthquake component as well as whether large triggered events can nucleate from within the rupture zone of the mainshock because ucerf3 etas has many sources of uncertainty as will any subsequent version or competing model potential usefulness needs to be considered in the context of actual applications electronic supplement 1 figures showing discretization verification of the distancedecaycubesampler average simulated participation rate and average cumulative magnitude frequency distributions mfds 1 http www bssaonline org lookup suppl doi 10 1785 0120160173 dc1

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

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

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

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

chemical and structural characterization of thermally simulated kerogen and its relationship with microporosity abstract kerogen was isolated from the maoming shale at different temperatures to understand changes in chemical structural and porosity characteristics during artificial maturation advanced solid state 13 c nuclear magnetic resonance nmr techniques were employed along with fourier transform infrared ft ir raman spectroscopy rs stable carbon isotopes and rock eval pyrolysis to characterize the organic matter om whereas the microporosity and surface properties were elucidated using n 2 and co 2 adsorption techniques as the temperature increased the aliphatic and carbonyl carbons of the kerogen samples showed remarkable decreases in abundance together with an increase of non protonated and protonated aromatic carbons moreover the kerogen became more enriched in 13 c and had a higher degree of crystallization with increasing ro and t max the aromaticity ranged from 46 9 to 94 7 and the minimum aromatic cluster size varied from 10 carbons at 350 c to 38 carbons at 500 c which was significantly related to the microporosity v o d co2 of the kerogen samples and their nonlinear sorption of phenanthrene and benzene the microporosity was extensively affected by the loss of aliphatic carbon and the increase of aromatic fused carbon when the temperature reached 500 c the collapse of aromatic interlayer remarkably reduced the micropore volume in the kerogen and then resulted in the decreasing adsorption of hydrophobic organic chemicals hocs the above observation confirms the molecular sieve effect in the kerogen samples in addition the micro filling adsorption for hocs is dominant on the thermally simulated kerogen samples

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

surface volume and gravity changes due to significant earthquakes occurred in central italy from 2009 to 2016 we have modelled the surface volume and gravity changes caused by four seismic events three mainshocks moment magnitude mw 6 0 5 9 6 5 occurred during the last seismic period started on 2016 august 24 in central italy and the 2009 april 6 l aquila earthquake mw 6 3 our calculations start from the source parameters estimated by the inversion of the largest dataset of interferometric synthetic aperture radar insar and global positioning system observations ever managed in italy after earthquake occurrences based on the half space elastic dislocation theory the vertical displacements modelled after the 2016 events allow to infer a substantial unbalance between the subsided and uplifted volumes in particular we detected 106 106 m3 of hangingwall subsidence against 37 106 m3 of footwall uplift that accounts for 74 of the total volume mobilization from the ratio between the footwall and total deformed volumes we have computed an average fault dip of 47 in line with the values retrieved by seismological methods the total gravity variations which affected the study area are of the order of 1 gal 1 gal 10 8 ms 2 in the far field and 170 gal in the near field the area affected within a gravity change of 1 gal is 140 km long and 57 km wide parallel to the apennines mountain chain the larger contribution is given by positive variations which account for the tensional style of deformation and larger subsided area the significant gravity variations modelled from the coseismic deformations point out the need to update our knowledge about the absolute gravity field in italy carrying out extensive measurements and to align italy to the recent international standards about national gravity and height networks international association of geodesy iag report commission 2 gravity field http www iag commission2 ch 2015

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

some remarks on the origin of foredeeps abstract geological observations show that there are two main types of foredeep basins on the base of their subsidence rate and their relationship with the associated orogen or accretionary wedge high rates of subsidence up to 1600 m myr and a ratio lower than 1 between the area of the elevated belt and the area of the basin characterize the foredeeps associated with w dipping subduction low rates of subsidence up to 300 m myr and a ratio higher than 1 between the area of the orogen and the area of the basin characterize the foredeeps associated with e or ne dipping subductions this observation enables us to interpret the slow filling of foredeeps of the first type and the much faster filling of foredeeps of the second type moreover w dipping subductions have a steeper and faster monocline bounding the base of the deep foredeep in contrast to e or ne dipping subductions which have a shallower monocline this differentiation supports the notion of the eastward mantle flow with respect to the lithosphere detected in the hot spot reference frame in this view the foredeep depth in w dipping subductions is mainly controlled by the roll back of the subduction hinge pushed by the relative eastward mantle flow while foredeep depth in e or ne dipping subductions is instead mainly generated by the load of the thrust sheets and by the roll back of the subduction hinge due to the advancing upper plate contrasting the upward push of the mantle the shape of the foredeeps is regularly arcuate in case of w dipping subduction while is linear or following the shape of the inherited continental margin in case of e or ne dipping subduction fold development in the two opposite foredeeps is significantly different in w dipping subduction the folds are transported down in subduction while they are forming and consequently they are poorly eroded syntectonic sediments drape a preserved fold in the e ne dipping subduction folds and thrust sheets are instead uplifted and deeply eroded this is also predicted by the envelope of the crests in the two distinct accretionary wedges in the w dipping case the envelope may dip toward the subduction while it is rising toward the hinterland in the other cases this approach may explain the differences in terms of geometries amount and rates of subsidence between the foredeeps around the adriatic plate for instance the foredeep of the southern alps back thrust belt foredeep is deformed in the western part by the later apenninic foredeep development associated with the sinistral oblique ramp of the w dipping adriatic plate subduction the relationship in the frontal parts of a thrust belt between accretion and eustacy has to be analyzed in terms of when where and how fast thrusts propagation took place with respect to the randomly distributed sea level third order fluctuations and by the type of subduction which is connected to the foredeep and thrust belt or accretionary wedge therefore the stratigraphic patterns in foredeep basins are peculiar and casual successions that record the combination of regional tectonic evolution with independent wider scale sea level changes

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

rupture of the pitaycachi fault in the 1887 mw 7 5 sonora mexico earthquake southern basin and range province rupture kinematics and epicenter inferred from rupture branching patterns during the 3 may 1887 mw 7 5 sonora earthquake surface rupture end to end length 101 8 km an array of three north south striking basin and range province faults from north to south pitaycachi teras and otates slipped sequentially along the western margin of the sierra madre occidental plateau this detailed field survey of the 1887 earthquake rupture zone along the pitaycachi fault includes mapping the rupture scarp and measurements of surface deformation the surface rupture has an endpoint to endpoint length of 41 0 km dips 70 w and is characterized by normal left lateral extension the maximum surface offset is 487 cm and the mean offset 260 cm the rupture trace shows a complex pattern of second order segmentation however this segmentation is not expressed in the 1887 along rupture surface offset profile which indicates that the secondary segments are linked at depth into a single coherent fault surface the pitaycachi surface rupture shows a well developed bipolar branching pattern suggesting that the rupture originated in its central part where the polarity of the rupture bifurcations changes most likely the rupture first propagated bilaterally along the pitaycachi fault the southern rupture front likely jumped across a step over to the teras fault and from there across a major relay zone to the otates fault branching probably resulted from the lateral propagation of the rupture after breaching the seismogenic part of the crust given that the much shorter ruptures of the otates and teras segments did not develop branches

spatial and temporal variations in growth rates along active normal fault systems an example from the lazio abruzzo apennines central italy abstract the geometry kinematics and rates of active extension in lazio abruzzo italian apennines have been measured in order to gain a better understanding of the spatial and temporal variations in fault growth rates and seismic hazards associated with active normal fault systems we present fault map traces throws throw rates and slip directions for 17 parallel en echelon or end on active normal faults whose 20 40 km lengths combine to form a soft linked fault array ca 155 km in length and ca 55 km across strike throw rates derived from observations of faulted late glacial features and holocene soils show that both maximum throw rates and throw rate gradients are greater on centrally located faults along the strike of the array total throws and throw gradients show similar spatial variations but with weaker relationships with distance along strike when summed across strike throw rates are increasingly high towards the centre of the array relative to summed throws we interpret the above to suggest that throw rates have changed in the recent past ca 0 7 ma from spatially random fault growth rates initiating at 2 5 3 3 ma to growth rates that are greater on centrally located faults we interpret this as evidence for fault interaction producing throw rate variations that drive throw profile readjustment on these crustal scale soft linked faults the results are used to discuss seismic hazards in the region which are quantified in a second paper in this issue