paleoseismology along the 1980 surface rupture of the irpinia fault implications for earthquake recurrence in the southern apennines italy the irpinia fault was the source of the ms 6 9 1980 irpinia earthquake and produced the first unequivocal historical surface faulting in italy trenching of the 1980 fault scarp at piano di pecore a flat intermontane basin about 5 km south of the 1980 instrumental epicenter provides the first data on earthquake recurrence intervals slip per event and slip rate on a major normal fault in the southern apennines fault zone the trenches exposed evidence of four pre 1980 paleoearthquakes that occurred during the past 8600 years a best estimate average recurrence interval is 2150 years although the time interval between individual events varies by as much as a factor of 2 each paleo earthquake is similar to the 1980 surface rupture in amount of slip and style of deformation which suggests that the 1980 event is characteristic for the irpinia fault slip per event values average 61 cm the net vertical displacement of 2 12 2 36 m since 8600 cal year b p observed in the trenches gives a vertical slip rate of 0 25 0 35 mm yr a dip slip rate of 0 29 0 40 mm yr and an extension rate of 0 14 0 20 mm yr although fault behavior data are only available for the irpinia fault they provide a starting point for evaluating earthquake recurrence and rates of deformation in southern apennines they suggest that 1 fault specific earthquake recurrence intervals based on the historical seismic record overestimates the occurrence of large magnitude m7 earthquakes and 2 the holocene rate of extension across the apennines is 1 mm yr the 1980 earthquake and the paleoseismologic observations show that repeated and localized surface faulting occurs in southern apennines and leaves subtle but distinct geomorphic evidence that can be detected with detailed and careful investigation

defining seismogenic sources from historical earthquake felt reports abstract we present a method that uses macroseismic intensity data to assess the location physical dimensions and orientation of the source of large historical earthquakes intensity data contain a great deal of information that can be used to constrain the essential characteristics of the seismic source in particular both the seismological theory and its practice suggest that the orientation of the source of significant earthquakes is reflected in the elongation of the associated damage pattern a plausible and easily manageable way of describing a seismic source is by representing it as an oriented rectangle the length and width of which are obtained from moment magnitude through empirical relationships this rectangle is meant to represent either the actual surface projection of the seismogenic fault or at least the projection of the portion of the earth crust where a given seismic source is likely to be located the systematic application of this method to all the m 5 5 earthquakes that occurred in the central and southern apennines italy in the past four centuries returned encouraging results that compare well with existing instrumental direct geological and geodynamic evidence the method is quite stable for different choices of the algorithm parameters and provides elongation directions that in most cases can be shown to be statistically significant in particular the resulting pattern of source orientations is rather homogeneous showing a consistent appennines parallel trend that agrees well with the ne sw extension style of deformation active in the central and southern portions of the italian peninsula

empirical ground motion attenuation relations for the eastern alps in the magnitude range 2 5 6 3 in this paper we use a large data set of seismometric and accelerometric recordings 3168 vertical and 1402 for each of the horizontal components collected by various networks in the eastern alps to estimate empirical ground motion attenuation relations valid in the magnitude range 2 5 6 3 for distances of up to 130 km relations are developed for horizontal and vertical peak ground acceleration and velocity arias intensity response spectral acceleration and fourier amplitude for 46 periods between 0 1 and 2 sec we adopt a simple magnitude dependent attenuation model predicting closer attenuation curves and decreasing distance attenuation for increasing magnitude we use truncated regression analysis to deal with the problem of non triggering stations with respect to other approaches our solution does not require any discarding of data or the knowledge of which stations did not trigger our relations agree with others suitable for the study region for magnitudes greater than 5 8 while they have a faster attenuation for lower magnitudes in an attempt to reduce the standard deviation we have introduced soil classification into the relation as well as a characterization of sites by means of h v ratios these ratios were estimated either by earthquakes receiver function or by the background seismic noise nakamura s ratios similar to findings in other studies the improvement obtained with soil classification is negligible while h v ratios reduce the standard deviation by up to 22 finally we have investigated the implications of these new relations for seismic hazard assessment considering two sites of interest located in northeastern italy udine and gemona in both cases the difference in the hazard estimates for return periods shorter than 100 years is notable with respect to all other available relations

a seismic hazard uncertainty analysis for the new madrid seismic zone abstract a review of the scientific issues relevant to characterizing earthquake sources in the new madrid seismic zone has led to the development of a logic tree of possible alternative parameters a variability analysis using monte carlo sampling of this consensus logic tree is presented and discussed the analysis shows that for 2 exceedence in 50 year hazard the best estimate seismic hazard map is similar to previously published seismic hazard maps for the area for peak ground acceleration pga and spectral acceleration at 0 2 and 1 0 s 0 2 and 1 0 s sa the coefficient of variation cov representing the knowledge based uncertainty in seismic hazard can exceed 0 6 over the new madrid seismic zone and diminishes to about 0 1 away from areas of seismic activity sensitivity analyses show that the largest contributor to pga 0 2 and 1 0 s sa seismic hazard variability is the uncertainty in the location of future 1811 1812 new madrid sized earthquakes this is followed by the variability due to the choice of ground motion attenuation relation the magnitude for the 1811 1812 new madrid earthquakes and the recurrence interval for m 6 5 events seismic hazard is not very sensitive to the variability in seismogenic width and length

seismic moment tensors of the april 2009 l aquila central italy earthquake sequence summary on 2009 april 6 the central apennines were hit by an mw 6 3 earthquake the region had been shaken since 2008 october by seismic activity that culminated in two foreshocks with mw 4 1 week and a few hours before the main shock we computed seismic moment tensors for 26 events with mw between 3 9 and 6 3 using the regional centroid moment tensor rcmt scheme most of these source parameters have been computed within 1 hr after the earthquake and rapidly revised successively the focal mechanisms are all extensional with a variable and sometimes significant strike slip component this geometry agrees with the ne sw extensional deformation of the apennines known from previous seismic and geodetic observations events group into three clusters those located in the southern area have larger centroid depths and a wider distribution of t axis directions these differences suggest that towards south a different fault system was activated with respect to the sw dipping normal faults beneath l aquila and more to the north

anatomy of an intruded coal ii effect of contact metamorphism on organic δ13c and implications for the release of thermogenic methane springfield no 5 coal illinois basin abstract concerns about the present day accelerated rate of carbon input to the atmosphere have prompted the search for comparable events throughout earth s history recent research has attempted to determine the cause of such events represented as negative 13 c excursions within the sedimentary record and their subsequent effect on the earth it has been suggested that such excursions could be the result of the large scale release of 13 c depleted thermogenic methane produced by the intrusion of large igneous provinces lips into organic rich rocks and or coal e g mcelwain et al 2005 svensen et al 2004 2007 our study asserts that if intrusions result in significant release of 13 c depleted thermogenic methane from intruded coals 13 c enriched coal should be observed adjacent to the intrusions in this study values of bulk organic 13 c 13 c org are reported for fifteen samples along a coal transect in the illinois basin where a pennsylvanian age coal the springfield or no 5 coal is intruded by a permian ultramafic dike the samples reveal significant bulk geochemical and petrographic changes within the alteration halo for example volatile matter vm decreases towards the intrusion whereas fixed carbon fc and vitrinite reflectance r r both increase accompanied by the development of natural coke both isotropic and anisotropic mosaic structure devolatilization vacuoles and carbonate mineralization reflectance levels and coke development are consistent with exposure to temperatures 450 500 c despite the high level of alteration of the organic matter no significant change is observed in 13 c org values across the transect vary by less than 0 5 along this transect 13 c org does not correlate with r r and does not appear to be influenced by maceral composition the intruded coals show no evidence of pyrolytic carbon that could influence 13 c org the relatively high vm contents of the intruded coals compared to coals that have undergone normal burial maturation and the lack of any trend in 13 c org approaching the intrusion raises questions about previously published models of the effects of large scale igneous intrusions on atmospheric composition and 13 c org excursions associated with oceanic anoxic events this study underscores the importance of the use of organic petrography in combination with isotope geochemistry to determine if contact metamorphosed coals and organic rich shales could have released a significant amount of 13 c org depleted volatiles leading to negative 13 c org excursions in the sedimentary record

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

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

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

rupture features of the 2016 mw 6 2 norcia earthquake and its possible relationship with strong seismic hazards for analyzing possible reasons for the heavy damage and seismogenic features of the 24 august 2016 norcia earthquake we constructed and analyzed its rupture process by incorporating data sets of near field strong motion teleseismic and static gps displacements the optimized model revealed a relatively compact slip pattern with mainly normal fault components the maximum slip was around 0 9 m while the rupture areas extended 11 km and 20 km along dip and strike respectively the total seismic moment was 2 3 1018 nm equivalent to mw 6 2 most seismic moments were released within 10 s radiating 3 5 1013 j of seismic energy the rupture history showed asymmetric propagation and is characterized by a relatively high rupture velocity within the first 6 s with a maximum of 3 2 km s the main shock slip pattern correlated well with the aftershocks distribution and most of the accumulated strain was released in the east of seismic gap between the nearby 1997 and 2009 earthquake sequences

model uncertainties of the 2002 update of california seismic hazard maps in this article we present and explore the source and ground motion model uncertainty and parametric sensitivity for the 2002 update of the california probabilistic seismic hazard maps our approach is to implement a monte carlo simulation that allows for independent sampling from fault to fault in each simulation the source distance dependent characteristics of the uncertainty maps of seismic hazard are explained by the fundamental uncertainty patterns from four basic test cases in which the uncertainties from one fault and two fault systems are studied in detail the california coefficient of variation cov ratio of the standard deviation to the mean map for peak ground acceleration 10 of exceedance in 50 years shows lower values 0 1 0 15 along the san andreas fault system and other class a faults than along class b faults 0 2 0 3 high cov values 0 4 0 6 are found around the garlock anacapa dume and palos verdes faults in southern california and around the maacama fault and cascadia subduction zone in northern california

geodetic and seismologic evidence for slip variability along a blind normal fault in the umbria marche 1997 1998 earthquakes central italy summary we analysed elevation changes induced by the 1997 1998 umbria marche central apennines italy earthquakes we employed data from a first order geodetic levelling line measured in 1951 1992 and 1998 the line bears a record of pre seismic and coseismic strains associated with the causative fault of the 1997 september 26 09 40 mainshock mw 6 0 a first level analysis performed under the assumption of slip homogeneity of coseismic slip shows misfits that cannot be reduced simply by altering the fault size and geometry a more detailed analysis based on a distribution of coseismic slip obtained from broad band seismograms provides a better fit and is in agreement with 1951 1992 elevation changes interpreted as precursory slip by previous investigators the levelling data sets new constraints on the location extent dip and depth of the fault in full agreement with seismological evidence and images from sar interferometry the data show no evidence for slip in the uppermost 3 km of the crust suggesting that a major and widely recognized normal fault that exists in the area is no longer active and showing a tendency of present tectonic strains to revert the current topographic setting

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

seismic sequences and swarms in the latium abruzzo molise apennines central italy new observations and analysis from a dense monitoring of the recent activity abstract we present a detailed analysis of the seismic activity in the central apennines based on a high quality seismogram data set collected from two temporary and three permanent networks this integrated network recorded between january 2009 and december 2013 a total of 7011 local earthquakes 6270 selected for this study with local magnitudes m l ranging from 0 4 to 4 7 hypocentres were located by using a reference 1d crustal velocity model determined with a genetic algorithm the majority of the hypocenters are located beneath the axis of the apenninic belt while the rest are found along the peri tyrrhenian margin hypocentral depth distribution extends to a depth of 31 km with a pronounced peak between 8 and 12 km both low to moderate magnitude seismic sequences and diffuse swarm like seismicity was observed there were two major seismic swarms and a seismic sequence which included the marsica sora m l 4 7 main shock a total of 468 fault plane solutions were derived from p wave polarities this new data set more than quadruples the number of focal mechanisms that was previously available for regional stress field analysis in the study region the majority of the fault plane solutions in the central apennines show predominantly normal fault movements with t axis trends oriented ne sw focal mechanisms calculated in this study confirm that this area is in extension for the seismic swarms sequence in the marsica sora area we also derived the azimuth and plunge of the principal stress axes by inverting fault plane solutions we find a few right lateral strike slip focal mechanisms that possibly identify the prolongation of the strike slip kinematics in the gargano apulia foreland to the west and mark the passage to the nw se striking normal faults of the inner apenninic belt the seismicity and stress distribution we observe might be consistent with a fragmented tectonic scenario in which faults with small dimensions release seismic energy in a diffused way

thermal models of the middle america trench at the nicoya peninsula costa rica 1 we present thermal models of the 24 ma cocos plate subducting under the caribbean plate at the nicoya peninsula costa rica our modeling incorporates the effect of hydrothermal cooling of the seafloor and the absence of an accretionary prism initial geotherms of the incoming plate representing different effective cooling depths of hydrothermal circulation affect the thermal structure and temperatures along the main subduction thrust excluding the deforming prism results in a higher heat flow immediately landward of the trench than previous models and therefore significant frictional heating is not required conductive plate cooling over predicts heat flow across the frontal forearc with no or very low frictional heating models with hydrothermal cooling to depths of 2 km under predicts the heat flow comparisons with recently determined hypocenter locations indicate that the updip limit of seismicity is consistent with temperatures between 100 150 c but there are large along strike variations in both the seismicity and thermal regime

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

the holocene paleoearthquakes on the 1915 avezzano earthquake faults central italy implications for active tectonics in the central apennines abstract extensive paleoseismological research was conducted in the fucino plain central italy in order to better understand the seismogenic characteristics of the fault responsible for the 1915 avezzano earthquake ms 7 0 and improve the general knowledge regarding active tectonics in the central apennines evidence for late pleistocene holocene surface faulting events was obtained through the study of thirteen sites across four different fault branches the paleoseismological analysis outlined the occurrence of ten surface faulting events in the past 33 000 years seven of which occurred during the holocene radiocarbon thermoluminescence and archaeological dating permitted the definition of an event chronology and the estimation of a recurrence interval for surface faulting events ranging between 1400 and 2600 years on the basis of the observed offsets it was possible to calculate vertical slip rates for the individual fault branches ranging between 0 24 mm yr 1 and 0 5 mm yr 1 and an extension rate across the fucino plain ranging between 0 6 and 1 mm yr 1 the chronology of surface faulting events appears linearly distributed in time and the observed recurrence times are similar to those inferred by other paleoseismological studies along different active apennine faults the general consequence of the large time span between strong earthquakes is that even a 2000 year long historical record such as the italian earthquake catalogue does not cover the entire seismic cycle of all the active apennine faults a comparison of the extension rate across the fucino plain with that across the entire central apennines as inferred from the sum of seismic moments of earthquakes which occurred in the interval 1000 1992 shows a seismicity deficit in the period indicated this confirms that a number of seismogenic faults were not active during the past 1000 years

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

fault based earthquake rupture forecast in central italy remarks after the l aquila mw 6 3 event abstract in 2006 we published an earthquake hazard model called lassci layered seismogenic source model in central italy in october 2008 we began to update the model for use in 5 and 10 year forecasts the lassci 2006 model is supported by good fault based definitions of seismogenic sources and simple physically motivated models of earthquake occurrence the lassci 2009 model has been improved by revision of the error propagation assumptions and increased accuracy of the earthquake probabilities the 6 april 2009 earthquake that struck l aquila occurred on the model fault having the highest probability of occurrence in the 2009 revised lassci forecast it is therefore consistent with our model assumptions furthermore peak ground accelerations were in reasonable agreement with the values having 90 probability of not being exceeded in 50 yr in the revised 2009 model the aggregate probability of having a maximum sized event in the next 5 yr on at least one of the neighboring sources less than 25 km distance away decreases in l aquila from 10 to 7 after the earthquake occurrence but still remains a maximum there along the central apennines the lassci models 2006 and 2009 featuring characteristic fault sources and time dependence seem to be suitable for guidance in reconstruction and seismic retrofit in the central appenines

random stress and earthquake statistics spatial dependence summary we calculate the 3 d stochastic rotations of focal mechanisms disorientations caused by stresses arising from the presence of many small random point defects that may surround the tip of an earthquake fault these random stresses can be shown to be distributed according to a cauchy distribution as a consequence the next episode of fracture of a fault cannot be planar the disorientation of focal mechanisms of these new rupture episodes is closely approximated by a rotational cauchy distribution as observed previously the geometry of fault systems for natural earthquakes is consistent with these observations since it too can be modelled by the cauchy distribution these observations indicate how the 3 d rupture process in rocks and other materials can be modelled we also calculate distributions of disorientations caused by a uniformly random 3 d rotation of sources these distributions are governed by symmetry properties of earthquake focal mechanisms to take into account the source symmetry we compare the cauchy distribution which is due to influence of random stresses to the distributions caused by random rotations

3d ground motion estimation in rome italy paleoseismic evidence and seismic hazard analysis suggest that the city of rome italy has experienced considerable earthquake ground motion since its establishment more than 2000 years ago seismic hazards in rome are mainly associated with two active seismogenic areas the alban hills and the central apennines regions located about 20 km southeast and 80 100 km east of central rome within the twentieth century m 6 8 and m 5 3 earthquakes in the apennines and the alban hills respectively have generated intensities up to mercalli cancani sieberg scale mcs vii in the city with a lack of strong motion records we have generated a 3d velocity model for rome embedded in a 1d regional model and estimated long period 1 hz ground motions for such scenarios from finite difference simulations of viscoelastic wave propagation we find 1 hz peak ground velocities pgvs and peak ground accelerations pgas of up to 14 cm sec and 44 cm sec2 respectively for a m 5 3 alban hills scenario largest near the northwestern edge of the tiber river our six simulations of a m 7 0 central apennine scenario generate 0 5 hz pgvs in rome of up to 9 cm sec as well as extended duration up to 60 sec the peak motions are similar to but the durations much longer than those from previous studies that omitted important wave guide effects between the source and the city the results from the two scenarios show that the strongest ground motion amplification in rome occurs in the holocene alluvial areas with strong basin edge effects in the tiber river valley our results are in agreement with earlier 2d sh wave results showing amplification of peak velocities by up to a factor of 2 in the alluvial sediments largest near the contact to the surrounding plio pleistocene formations our results suggest that both earthquakes from the alban hills and the central apennines regions contribute to the seismic hazards in rome although earthquakes from the former area may generate the larger peak motions seismic waves from the latter region may generate ground motions with extended durations capable of causing significant damage on the built environment

surface faulting in norcia central italy a paleoseismological perspective we carried out paleoseismological analyses in norcia one of the oldest town of central italy four trenches were dug in late pleistocene holocene deposits across an unmapped antithetic splay of the norcia fault system the investigated fault runs through the recent settlement of the town brushing against the middle age city walls we found evidence of repeated surface ruptures in the past 20 ky the last one dated to a period fitting with the 1703 ad catastrophic earthquake m 6 8 our data i show definitively the late pleistocene holocene activity of the norcia fault system ii strengthen the historical accounts describing surface ruptures during the 1703 event in norcia iii cast light on the seismogenic behavior of the 70 km long fault system between l aquila and norcia central italy and iv predict the occurrence of normal surface faulting inside the municipality of norcia during future mz6 earthquakes d 2005 elsevier b v all rights reserved

estimation of response spectra and simulation of nonstationary earthquake ground motions abstract italian strong motion data were used to study the attenuation of response spectra and to simulate artificial accelerograms as a function of magnitude distance and site geology the database has already been utilized for the study of the atten uation of peak ground acceleration pga and velocity and consists of 95 accelero grams from 17 earthquakes of magnitudes ranging from 4 6 to 6 8 using multiple regressions we developed empirical predictive equations for the vertical and hori zontal components of response spectra corresponding to 14 frequencies ranging from 0 25 to 25 hz predictive equations aimed at the ground motion simulation were also estimated for time dependent frequency parameters strong ground motion du ration and arias intensity the shape of the predicted spectra is strongly dependent on magnitude and nearly independent of distance alluvium sites show an amplification effect with respect to stiff sites in different frequency ranges according to the thickness of the soil deposit the vertical horizontal spectral ratio in far field varies with magnitude and frequency from 0 35 to 0 85 the resulting response spectra are compared with the predictions of some recent attenuation relationships and with those proposed by the eurocode ec8 the simulation of nonstationary strong ground motions is achieved through an empirical method where time and frequency features of the motion are represented through the physical spectrum extending the spectral moments theory to the nonsta tionary case the simulated time histories fit the recorded accelerograms in terms of several ground motion amplitude measures such as peak acceleration peak velocity fourier spectra and response spectra the principal advantage of the proposed method consists in correlating the simulation parameters with earthquake magnitude source distance and soil conditions introduction in the field of seismic risk assessment the prediction of shaking intensity in future earthquakes plays a key role re liable estimates of the ground motions that structures must be designed to withstand are obtained mainly through em pirical predictive relationships developed after statistical analysis of data recorded during strong earthquakes many predictive equations are by now available in dif ferent regions of the world campbell 1985 1993 for the prediction of peak ground acceleration pga many fewer are the relationships developed for the prediction of response spectral values idriss 1991 boore

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

slip rate depth distribution for active faults in central italy using numerical models abstract slip rate is a critical parameter for describing geologic and earthquake rates of known active faults although faults are inherently three dimensional surfaces the paucity of data allows for estimating only the slip rate at the ground surface and often only few values for an entire fault these values are frequently assumed as proxies or as some average of slip rate at depth evidence of geological offset and single earthquake displacement as well as mechanical requirements show that fault slip varies significantly with depth slip rate should thus vary in a presumably similar way yet these variations are rarely considered in this work we tackle the determination of slip rate depth distributions by applying the finite element method on a 2d vertical section with stratification and faults across the central apennines italy in a first step we perform a plane stress analysis assuming visco elasto plastic rheology and then search throughout a large range of values to minimize the rms deviation between the model and the interseismic gps velocities using a parametric analysis we assess the accuracy of the best model and the sensitivity of its parameters in a second step we unlock the faults and let the model simulate 10 kyr of deformation to estimate the fault long term slip rates the overall average slip rate at depth is approximately 1 1 mm yr for normal faults and 0 2 mm yr for thrust faults a maximum value of about 2 mm yr characterizes the avezzano fault that caused the 1915 mw 7 0 earthquake the slip rate depth distribution varies significantly from fault to fault and even between neighbouring faults with maxima and minima located at different depths we found uniform distributions only occasionally we suggest that these findings can strongly influence the forecasting of cumulative earthquake depth distributions based on long term fault slip rates

m 7 earthquake rupture forecast and time dependent probability for the sea of marmara region turkey we forecast time independent and time dependent earthquake ruptures in the marmara region of turkey for the next 30 years using a new fault segmentation model we also augment time dependent brownian passage time bpt probability with static coulomb stress changes cff from interacting faults we calculate mw 6 5 probability from 26 individual fault sources in the marmara region we also consider a multisegment rupture model that allows higher magnitude ruptures over some segments of the northern branch of the north anatolian fault zone beneath the marmara sea a total of 10 different mw 7 0 to mw 8 0 multisegment ruptures are combined with the other regional faults at rates that balance the overall moment accumulation we use gaussian random distributions to treat parameter uncertainties e g aperiodicity maximum expected magnitude slip rate and consequently mean recurrence time of the statistical distributions associated with each fault source we then estimate uncertainties of the 30 year probability values for the next characteristic event obtained from three different models poisson bpt and bpt cff using a monte carlo procedure the gerede fault segment located at the eastern end of the marmara region shows the highest 30 year probability with a poisson value of 29 and a time dependent interaction probability of 48 we find an aggregated 30 year poisson probability of m 7 3 earthquakes at istanbul of 35 which increases to 47 if time dependence and stress transfer are considered we calculate a twofold probability gain ratio time dependent to time independent on the southern strands of the north anatolian fault zone

palaeoseismicity in the gran sasso massif abruzzo central italy abstract the upper maone and venacquaro valleys on the northern side of the gran sasso massif apennines central italy have been studied in detail from the geological and geomorphological standpoints to date the activity of the faults that produced spectacular fault scarps in the late glacial and holocene sediments and morphological features the faults that produced the studied scarps have been active at least four times during the last 18 000 years and each time on the basis of the indications emerging from the study of the scarp heights displacements of similar size were probably produced the first faulting seems datable to a period slightly more recent than 18 000 years ago the second faulting occurred after the moraines of the second apennine stage these preceding a lacustrine deposit dated 11 760 160 bp could be put in the older portion of the period between 16 000 and 13 000 years ago the third faulting must be more recent than 6000 7000 years ago and slightly older than 5450 170 and 6110 180 bp a fourth phase is appreciably later than 3490 160 bp and older than the year 1000 a d for the venacquaro valley the size of the displacements more recent than 18 000 years ago indicated by the height of the fault scarps and by geophysical data is about 16 18 m for the val maone the size of the displacements more recent than the moraines of the second apennine stage is 10 11 m the respective slip rates are 0 88 1 mm year for the venacquaro valley and approximately 0 67 0 78 mm year for the maone valley it is very probable that the fault activity occurred during a seismic event or events that took place during a short time the intervals between the seismic events or seismic periods although these cannot be defined with precision appear longer than 2500 3000 years and shorter than 6000 7000 years it is possible that also in the gran sasso as in other parts of the abruzzo apennines seismic activity is characterized by events of great magnitude with long return periods

the nisi fault as a key structure for understanding the active deformation of the nw peloponnese greece abstract the previously unknown nisi fault in nw peloponnese was ruptured during the 2008 movri mountain earthquake attaining a maximum offset of 25 cm the fault is interpreted as a branch of a flower structure above a blind strike slip fault we investigate the nisi fault seismotectonic evolution using morphotectonic analysis in order to determine whether the landscape is affected by tectonic forcing and paleoseismology to determine earthquake recurrence interval and fault slip rates we applied several geomorphic indices such as the asymmetry factor af the stream length gradient index sl the valley floor width to valley height ratio vf the mountain front sinuosity smf the drainage basin shape bs and the hypsometric curve hc in four large drainage basins of the study area the results show that fault related vertical motions and the associated tilting influenced the drainage geometry and the landscape development values of stream gradient indices sl are relatively high close to the fault trace mountain front sinuosity smf mean values along the fault zones range from 1 12 to 1 23 valley floor width to valley height ratios vf mean values along the studied fault range between 0 21 and 2 50 drainage basin shape bs mean values along the fault range from 1 04 to 3 72 lateral fault growth was likely achieved by propagation primarily towards north northwestward the paleoseismic history of the fault investigated by a trench and 14c dating of seven samples indicates two morphogenic earthquakes in the last 1 kyr therefore we suggest that the nisi fault displays a slip rate on the order of 1 mm yr and a recurrence interval ranging between 300 and 600 years from a seismotectonic point of view the fault is classified as high activity rate with abundant but discontinuous geomorphic evidence of its activity other similar faults affecting the western peloponnese can be envisaged with a similar procedure additionally the seismic history and surface expression of the nisi fault resembles other faults of similar length in greece and italy particularly a crucial issue in terms of seismic risk management is that neotectonic analysis has to be envisaged carefully on short in length faults since these faults can be possibly related to strong earthquakes

probabilities of occurrence of large plate rupturing earthquakes for the san andreas san jacinto and imperial faults california 1983 2003 the san andreas san jacinto and imperial faults in california are divided into 19 segments conditional probabilities are calculated that a particular segment will be the site of a large plate rupturing earthquake i e an event that breaks the entire down dip extent of the seismogenic zone during the next 20 years the sizes of such events which account for most of the slip that occurs seismically appear to vary greatly for different segments of these faults repeat time of large shocks coseismic displacement moment release rupture length and seismic magnitude appear to correlate with one another and to be a function of the tectonic style of different parts of those fault zones tectonic inhomogeneities on a scale of about 1 to 100 km are much larger than displacement in any single seismic event and may be regarded as being invariant in their effects upon earthquake generation over many cycles of large shocks it is this invariance that appears to lead to a given segment of a fault rupturing repeatedly in events of nearly the same size since repeat time varies however for a given segment of a fault a simple probabilistic approach is used to forecast the likelihood of large future earthquakes for each segment using as input the time of the last large shock the average recurrence time and the standard deviation of time intervals between events dates of the last large shocks are available for most of the segments investigated repeat times are estimated from times of historic and prehistoric events tectonic similarity and times calculated from coseismic displacement in the last large shock divided by a rate of fault motion or strain buildup the standard deviation of time intervals divided by the average repeat time is close to 1 3 for three fault segments in california for which data are available on historic and prehistoric earthquakes that normalized value is adopted for all calculations of conditional probability magnitudes and seismic moments of future plate rupturing events are estimated for each fault segment several of the segments have well constrained probabilities for rupture during the next 20 years whereas others have large uncertainties eight of the segments constituting about 40 of the total lengths of the three faults have moderate to high probability and thus should be instrumented and studied extensively so as to provide shorter time warnings in some cases two adjacent segments may be nearly in phase in their loading history and may break in a single event the segment of the san andreas fault from opposite san jose to san juan bautista which ruptured less than 1 5 m in 1906 and which probably also broke in 1838 is calculated to have a moderate to high probability of an earthquake of magnitude 6 to during the next 20 years a 325 km section of the southern san andreas between tejon pass and the salton sea has about a 25 chance of rupturing in a shock of magnitude near 8 during the next 20 years all the other segments have only a small chance i e less than 5 to 10 of rupturing in an event of magnitude near 8 during that interval

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

the database of individual seismogenic sources diss version 3 summarizing 20 years of research on italy s earthquake geology abstract this paper describes the main characteristics the evolution and the structure of the database of individual seismogenic sources diss and particularly of its release of early 2007 the database contains the results of the investigations of the active tectonics in italy during the past 20 years the first two sections of this paper document the recent evolution in mapping and archiving italian active fault data in relation to important achievements in the understanding of italian tectonics some of which were spurred by significant earthquakes the central sections describe the current structure of the database the reasons for its assumptions and data categories its current contents its evolution through several years of improvements the last section describes how the current contents of the database correspond with the existing strain and stress data available from focal mechanism borehole breakout and gps data for the whole of italy the database supplies a fresh and unified view of active and seismogenic processes in italy by building on basic physical constraints concerning rates of crustal deformation on the continuity of deformation belts and on the spatial relationships between adjacent faults both at the surface and at depth

new paleoseismological data from the gran sasso d italia area central apennines 1 paleoseismological analyses along the campo imperatore normal fault cif in the gran sasso massif which is an area characterized by the absence of significant historical earthquakes highlight the occurrence of surface faulting after the 5th 3rd cent bc and around the 6th 5th millenium bc these ages agree with those reported by giraudi and frezzotti 1995 on the western tip of the cif thus suggesting the possible entire rupture of the 30 km long cif during m7 events these data contribute to the re evaluation of the seismic hazard of a large surrounding area including the city of l aquila 100 000 inhabitants which is located 20 km from the cif in the hangingwall side index terms 7221 seismology paleoseismology 7223 seismology seismic hazard assessment and prediction 7230 seismology seismicity and seismotectonics 8107 tectonophysics continental neotectonics

seismogenic sources in the adriatic domain abstract we present an overview of the seismogenic source model of the adriatic domain included in the latest version of the diss database http diss rm ingv it diss and in the european share database http diss rm ingv it share the model consists of composite and individual seismogenic sources located inside and along the margins of the adria plate in order to locate and parameterize the sources we integrated a wide set of geological geophysical seismological and geodynamic data either available from published literature or resulting from our own field work seismic profile interpretations and numerical modelling studies we grouped the sources into five regions based on geometrical and kinematic homogeneity criteria seismogenic sources of the central western adriatic north eastern adriatic eastern adriatic and central adriatic regions belong to the northern apennines external dinarides and offshore domains respectively they are characterized by nw se strike reverse to oblique kinematics and shallow crustal seismogenic depth seismogenic sources of the southern western adriatic region instead are e w striking dextral strike slip faults cutting both the upper and lower crust the fastest moving seismogenic sources are the most southern thrusts of the eastern adriatic and the strike slip sources of the southern western adriatic while the seismogenic sources of the central adriatic exhibit the lowest slip rates estimates of maximum magnitude are generally in good agreement with the historical and instrumental earthquake records except for the north eastern adriatic region where seismogenic sources exhibit a potential for large earthquakes even though no strong events have been reported or registered all sources included in the database are fully geometrically and kinematically parameterized and can be incorportaed in seismic hazard calculations and earthquake or tsunami scenario simulations

a bayesian seismic hazard analysis for the city of naples in this paper we explore the feasibility of formulating the hazard assessment procedure to include the information of past earthquakes into the probabilistic seismic hazard analysis together with the use of an ensemble modeling technique this strategy allows on one hand to enlarge the information used in the evaluation of the hazard from alternative models for the earthquake generation process to past shaking and on the other hand to explicitly account for the uncertainties the bayesian scheme we propose is applied to evaluate the seismic hazard of naples the framework in which we have embedded the tools is flexible to include all types of uncertainties here we focus on a sensitive study of the earthquake occurrence by implementing models that span from random to cluster type temporal behavior and models that include quasi periodic occurrence of earthquakes on faults we implement 5 different spatio temporal models to parameterize the occurrence of earthquakes potentially dangerous for naples subsequently we combine these hazard curves with shakemaps of past earthquakes that have been felt in naples since 1200 a d the results are posterior ensemble hazard curves for three exposure times e g 5 10 and 50 years in a dense grid that cover the municipality of naples considering rocky soil and including the site amplification our results show the importance to include the data from past shaking since the difference between the prior and the posterior is about 8 15 for the different exposure times

quaternary basin evolution and present tectonic regime in the area of the 1997 1998 umbria marche seismic sequence central italy abstract geological and geomorphological surveys have been performed in the area affected by the 1997 1998 umbria marche seismic sequence m max 6 0 aimed at defining the quaternary tectonic history and the characteristics of the present tectonic regime data have been collected from 1 the analysis of the remnant landsurfaces by means of aerial photos and field surveys 2 geological surveys in the cesi san martino basin and in the easternmost sector of the colfiorito basin in order to identify deformative features affecting the quaternary deposits 3 the analysis of boreholes and geo electrical data derived from previous surveys performed in the 1960s in order to reconstruct the top of the pre quaternary substratum in the colfiorito basin two different successions of remnant landsurfaces have been identified along the faults bounding the basins to the east in the hangingwall and the footwall respectively the difference accounts for a fault controlled evolution of the landscape at least during the upper pliocene early pleistocene the deformation affecting the quaternary deposits and landforms in the investigated basins indicates a decreasing tectonic activity along the master faults since the middle pleistocene surface deformation due to tectonics is faint and displayed by gentle warping of the landforms during the late quaternary as for the basin geometry subsurface data show that two minor depressions formed in the colfiorito basin during the quaternary the oldest one close to the fault bounding the basin while the youngest and deepest formed in the inner portion of the basin therefore the present geometry is different from that of other fault bounded quaternary depressions of the central apennines typically half graben basins showing the maximum depth of the substratum in the area close to the master fault tectonic history may be summarised as follows 1 origin of the quaternary fault bounded colfiorito and cesi san martino basins 2 evolution of the basins with a half graben style 3 significant reduction of tectonic activity since the middle pleistocene during the third phase the evolution of the basins is no longer related to a half graben style in the case of the colfiorito basin a new depression is superimposed to on the previous half graben whose evolution is related to the lowering of the inner portion of the basin through warping moreover present activity does not result in fault related surficial displacements but only in continuous deformation spread over the basins these conclusions have fundamental implications for the seismotectonic framework of the 1997 1998 earthquake sequence this deformation style is indeed in agreement with the coseismic deformation modelled by means of the sar interferometry analyses carried out by other institutions during the seismic sequence and with the lack of evident surface faulting related to the mentioned events in the investigated area this evidence indicates that the evolution of the investigated area since the middle pleistocene resulted from the summation of deformative episodes similar to that which occurred during the recent seismic sequence as a consequence no earthquakes with magnitude larger than 6 are expected in the area

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

connecting seismically active normal faults with quaternary geological structures in a complex extensional environment the colfiorito 1997 case history northern apennines italy 1 the northern apennines of italy are characterized by a complex tertiary tectonic history where superposed compressional and extensional deformation occurred in such regions characterized by low active extensional strain rate the coseismic surface ruptures are rare and often a matter of much debate resulting in a difficult connection between geological faults i e faults which can be mapped at the surface and seismological faults i e faults which actually generate earthquakes the availability of detailed geological mapping and high resolution seismological data for the colfiorito area struck in 1997 by a sequence of six 5 mw 6 normal faulting earthquakes allow us to compare and verify the existence of geometric and kinematic correspondence between the mapped geological quaternary faults and the activated structures in map view the earthquakes distribution reflects the fault pattern mapped at the surface the length of activated and mapped faults is quite similar 7 10 km the coseismic subsided region imaged by interferometric synthetic aperture radar data is located in the hanging wall of the mapped normal faults that bound the quaternary basins in section view there is a geometric connection between mapped normal faults and the aftershock alignments used to image fault geometry at depth comparison of striated fault planes and aftershock focal mechanism solutions show a strong kinematic consistency this study points out that the quaternary tectonosedimentary evolution and the present day geological and geomorphologic setting of the colfiorito area can be interpreted as the result of repeated extensional earthquakes similar to the 1997 events occurring on nw se trending normal faults our data also show that the main shocks of the colfiorito sequence nucleated close to the intersections between the normal faults and the preexisting compressional transpressional structures which in 1997 acted as lateral barriers to rupture propagation and consequently constrained the fault size

form and flow of the academy of sciences ice cap severnaya zemlya russian high arctic 1 the 5 575 km2 academy of sciences ice cap is the largest in the russian arctic a 100 mhz airborne radar digital landsat imagery and satellite synthetic aperture radar sar interferometry are used to investigate its form and flow including the proportion of mass lost through iceberg calving the ice cap was covered by a 10 km spaced grid of radar flight paths and the central portion was covered by a grid at 5 km intervals a total of 1 657 km of radar data digital elevation models dems of ice surface elevation ice thickness and bed elevation data sets were produced cell size 500 m the dems were used in the selection of a deep ice core drill site total ice cap volume is 2 184 km3 5 5 mm sea level equivalent the ice cap has a single dome reaching 749 m maximum ice thickness is 819 m about 200 km or 42 of the ice margin is marine about 50 of the ice cap bed is below sea level the central divide of the ice cap and several major drainage basins in the south and east of the ice cap and of up to 975 km2 are delimited from satellite imagery there is no evidence of past surge activity on the ice cap sar interferometric fringes and phase unwrapped velocities for the whole ice cap indicate slow flow in the interior and much of the margin punctuated by four fast flowing features with lateral shear zones and maximum velocity of 140 m yr 1 these ice streams extend back into the slower moving ice to within 5 10 km of the ice cap crest they have lengths of 17 37 km and widths of 4 8 km mass flux from these ice streams is 0 54 km3 yr 1 tabular icebergs up to 1 7 km long are produced total iceberg flux from the ice cap is 0 65 km3 yr 1 and probably represents 40 of the overall mass loss with the remainder coming from surface melting driving stresses are generally lowest 40 kpa close to the ice cap divides and in several of the ice streams ice stream motion is likely to include a significant basal component and may involve deformable marine sediments

characterization of earthquake induced ground motion from the l aquila seismic sequence of 2009 italy summary based only on weak motion data we carried out a combined study on region specific source scaling and crustal attenuation in the central apennines italy our goal was to obtain a reappraisal of the existing predictive relationships for the ground motion and to test them against the strong motion data peak ground acceleration pga peak ground velocity pgv and spectral acceleration sa gathered during the mw 6 15 l aquila earthquake 2009 april 6 01 32 utc the l aquila main shock was not part of the predictive study and the validation test was an extrapolation to one magnitude unit above the largest earthquake of the calibration data set the regional attenuation was determined through a set of regressions on a data set of 12 777 high quality high gain waveforms with excellent s n ratios 4259 vertical and 8518 horizontal time histories seismograms were selected from the recordings of 170 foreshocks and aftershocks of the sequence the complete set of all earthquakes with ml 3 0 from 2008 october 1 to 2010 may 10 all waveforms were downloaded from the iside web page http iside rm ingv it iside standard index jsp a web site maintained by the istituto nazionale di geofisica e vulcanologia ingv weak motion data were used to obtain a moment tensor solution as well as a coda based moment rate source spectrum for each one of the 170 events of the l aquila sequence 2 8 mw 6 15 source spectra were used to verify the good agreement with the source scaling of the colfiorito seismic sequence of 1997 1998 recently described by malagnini et al 2008 finally results on source excitation and crustal attenuation were used to produce the absolute site terms for the 23 stations located within 80 km of the epicentral area the complete set of spectral corrections crustal attenuation and absolute site effects was used to implement a fast and accurate tool for the automatic computation of moment magnitudes in the central apennines

a ten year earthquake occurrence model for italy the recent m w 6 3 destructive l aquila earthquake has further stimulated the improvement of the italian operational earthquake forecasting capability at different time intervals here we describe a medium term 10 year forecast model for m w 5 5 earthquakes in italy that aims at opening new possibilities for risk mitigation purposes while a longer forecast yielded by the national seismic hazard map is the primary component in establishing the building code a medium term earthquake forecast model may be useful to prioritize additional risk mitigation strategies such as the retrofitting of vulnerable structures in particular we have developed an earthquake occurrence model for a 10 year forecast that consists of a weighted average of time independent and different types of available time dependent models based on seismotectonic zonations and regular grids the inclusion of time dependent models marks a difference with the earthquake occurrence model of the national seismic hazard map and it is motivated by the fact that at the 10 year scale the contribution of time dependency in the earthquake occurrence process may play a major role the models are assembled through a simple averaging scheme whereby each model is weighted through the results of a retrospective testing phase similar to the ones carried out in the framework of the collaboratory for the study of earthquake predictability in this way the most hazardous italian areas in the next ten years will arise from a combination of distinct models that place more emphasis on different aspects of the earthquake occurrence process such as earthquake clustering historical seismic rate and the presence of delayed faults capable of large events finally we report new challenges and possible developments for future updating of the model

a monte carlo method for probabilistic hazard assessment of induced seismicity due to conventional natural gas production abstract a monte carlo approach to probabilistic seismic hazard analysis is developed for a case of induced seismicity associated with a compacting gas reservoir the geomechanical foundation for the method is the work of kostrov 1974 and mcgarr 1976 linking total strain to summed seismic moment in an earthquake catalog our monte carlo method simulates future seismic hazard consistent with historical seismic and compaction datasets by sampling probability distributions for total seismic moment event locations and magnitudes and resulting ground motions ground motions are aggregated over an ensemble of simulated catalogs to give a probabilistic representation of the ground motion hazard this approach is particularly well suited to the specific nature of the time dependent induced seismicity considered we demonstrate the method by applying it to seismicity induced by reservoir compaction following gas production from the groningen gas field a new ground motion prediction equation gmpe tailored to the groningen field has been derived by calibrating an existing gmpe with local strong motion data for 2013 2023 we find a 2 chance of exceeding a peak ground acceleration of 0 57 g and a 2 chance of exceeding a peak ground velocity of 22 cm s above the area of maximum compaction disaggregation shows that earthquakes of m w 4 5 at the shortest hypocentral distances of 3 km and ground motions two standard deviations above the median make the largest contributions to this hazard uncertainty in the hazard is primarily due to uncertainty about the future fraction of induced strains that will be seismogenic and how ground motion and its variability will scale to larger magnitudes

discrepancy between earthquake rates implied by historic earthquakes and a consensus geologic source model for california we examine the difference between expected earthquake rates inferred from the historical earthquake catalog and the geologic data that was used to develop the consensus seismic source characterization for the state of california california department of conservation division of mines and geology cdmg and u s geological survey usgs petersen et al 1996 frankel et al 1996 on average the historic earthquake catalog and the seismic source model both indicate about one m 6 or greater earthquake per year in the state of california however the overall earthquake rates of earthquakes with magnitudes m between 6 and 7 in this seismic source model are higher by at least a factor of 2 than the mean historic earthquake rates for both southern and northern california the earthquake rate discrepancy results from a seismic source model that includes earthquakes with characteristic maximum magnitudes that are primarily between m 6 4 and 7 1 many of these faults are interpreted to accommodate high strain rates from geologic and geodetic data but have not ruptured in large earthquakes during historic time our sensitivity study indicates that the rate differences between magnitudes 6 and 7 can be reduced by adjusting the magnitude frequency distribution of the source model to reflect more characteristic behavior by decreasing the moment rate available for seismogenic slip along faults by increasing the maximum magnitude of the earthquake on a fault or by decreasing the maximum magnitude of the background seismicity however no single parameter can be adjusted consistent with scientific consensus to eliminate the earthquake rate discrepancy applying a combination of these parametric adjustments yields an alternative earthquake source model that is more compatible with the historic data the 475 year return period hazard for peak ground and 1 sec spectral acceleration resulting from this alternative source model differs from the hazard resulting from the standard cdmg usgs model by less than 10 across most of california but is higher generally about 10 to 30 within 20 km from some faults

effect of time dependence on probabilistic seismic hazard maps and deaggregation for the central apennines italy abstract we produce probabilistic seismic hazard assessments for the central apennines italy using time dependent models that are characterized using a brownian passage time recurrence model using aperiodicity parameters of 0 3 0 5 and 0 7 we examine the sensitivity of the probabilistic ground motion and its deaggregation to these parameters for the seismic source model we incorporate both smoothed historical seismicity over the area and geological information on faults we use the maximum magnitude model for the fault sources together with a uniform probability of rupture along the fault floating fault model to model fictitious faults to account for earthquakes that cannot be correlated with known geologic structural segmentation we show maps for peak ground acceleration pga and 1 0 hz spectral acceleration sa 1 on rock having 10 probability of exceedence in 50 yr we produce maps to compare the separate contributions of smoothed seismicity and fault components in addition we construct maps that show sensitivity of the hazard for different parameters and the poisson model for the poisson model the addition of fault sources to the smoothed seismicity raises the hazard by 50 at locations where the smoothed seismicity contributes the highest hazard and up to 100 at locations where the hazard from smoothed seismicity is low for the strongest aperiodicity parameter smallest the hazard may further increase 60 80 or more or may decrease by as much as 20 depending on the recency of the last event on the fault that dominates the hazard at a given site in order to present the most likely earthquake magnitude and or the most likely source site distance for scenario studies we deaggregate the seismic hazard for sa 1 and pga for two important cities rome and l aquila for pga both locations show the predominance of local sources having magnitudes of about 5 3 and 6 5 respectively for sa 1 at a site in rome there is significant contribution from local smoothed seismicity and an additional contribution from the more distant apennine faults having magnitude around 6 8 for l aquila the predominant sources remain local in order to show the variety of impact of different values we also obtained deaggregations for another three sites in general as decreases periodicity increases the deaggregation indicates that the hazard is highest near faults with the highest earthquakes rates this effect is strongest for the long period 1 sec ground motions

geographic deaggregation of seismic hazard in the united states the seismic hazard calculations for the 1996 national seismic hazard maps have been geographically deaggregated to assist in the understanding of the relative contributions of sources these deaggregations are exhibited as maps with vertical bars whose heights are proportional to the contribution that each geographical cell makes to the ground motion exceedance hazard bar colors correspond to average source magnitudes we also extend the deaggregation analysis reported in harmsen et al 1999 to the western conterminous united states in contrast to the central and eastern united states ceus the influence of specific faults or characteristic events can be clearly identified geographic deaggregation for 0 2 sec and 1 0 sec pseudo spectral acceleration sa is performed for 10 probability of exceedance pe in 50 yr 475 yr mean return period and 2 pe in 50 yr 2475 yr mean return period for four western u s cities los angeles salt lake city san francisco and seattle and for three central and eastern u s cities atlanta boston and saint louis in general as the pe is lowered the sources of hazard closer to the site dominate larger more distant earthquakes contribute more significantly to hazard for 1 0 sec sa than for 0 2 sec sa additional maps of geographically deaggregated seismic hazard are available on the internet for 120 cities in the conterminous united states for 1 sec sa and for 0 2 sec sa with a 2 pe in 50 yr examination of these maps of hazard contributions enables the investigator to determine the distance and azimuth to predominant sources and their magnitudes this information can be used to generate scenario earthquakes and corresponding time histories for seismic design and retrofit where fault density is lower than deaggregation cell dimensions we can identify specific faults that contribute significantly to the seismic hazard at a given site detailed fault information enables investigators to include rupture information such as source directivity radiation pattern and basin edge effects into their scenario earthquakes used in engineering analyses

investigation of the active celano l aquila fault system abruzzi central apennines italy with combined ground penetrating radar and palaeoseismic trenching summary we studied fault scarps along the northern sector of the celano l aquila fault system in the abruzzi region central apennines up to 9 5 km long 3 m high fault scarp traces mark the slope foot of ridgetop valleys at mt ocre range in order to provide direct evidence of the deformation history of these scarps we initiated geomorphic ground penetrating radar gpr and trenching investigations gpr investigations yielded subsurface stratigraphic features of the scarp zones and determined the locations for trenching sites a total of five trenches were excavated at two different sites structural and stratigraphic analysis of the trench exposures combined with historical considerations showed three faulting events between 5620 bc and 1300 ad the most recent of them occurred after 1690 bc each of these events produced an estimated minimum vertical displacement ranging between 0 3 and 0 5 m our interpretation is that the mt ocre fault branch represents the northernmost surface expression of a single 35 km long seismogenic structure associated with m 7 earthquakes any attempt to estimate the seismic hazard in the area must consider the presence of this important source

strain rate relaxation of normal and thrust faults in italy summary we find that geodetic strain rate sr integrated with the knowledge of active faults points out that hazardous seismic areas are those with lower sr where active faults are possibly approaching the end of seismic cycle sr values estimated from gps velocities at epicentral areas of large historical earthquakes in italy decrease with increasing elapsed time thus highlighting faults more prone to reactivation we have modelled an exponential decrease relationship between sr and the time elapsed since the last largest earthquake differencing historical earthquakes according to their fault rupture style then we have estimated the characteristic times of relaxation by a non linear inversion showing that events with thrust mechanism exhibit a characteristic time 990yr about three times larger than those with normal mechanism assuming standard rigidity and viscosity values we can infer an average recurrence time of about 600yr for normal faults and about 2000yr for thrust faults

time independent and time dependent seismic hazard in greece based on seismogenic sources abstract an improved procedure is followed to assess time independent andtime dependent hazard for 144 broad sites cities towns villages of greece in termsof expected macroseismic intensities at each one of these sites in this procedureseveral new results are taken into account source parameters based on new researchwork on seismicity and on other relative information new regionalization and im proved seismicity data parameters and anisotropic radiation at the seismic source anew relation for the attenuation of macroseismic intensities and the effect of localconditions site effects on the strong ground motion analytic relations and tables determined by this procedure permit the reliableassessment of time independent hazard in terms of macroseismic intensity in mmscale peak horizontal ground acceleration and velocity at each one of these 144sites and at any probability level time dependent hazard has been also assessed for these 144 broad sites in greece in terms of the probability for the occurrence of strong ground motion with macro seismic intensity i vii in mm scale at each one of these sites during the period1996 2010 comparison of the assessed time dependent hazard with observed ma croseismic intensities of the period 1950 1995 indicates that the time dependentmodel gives very reasonable results introduction

paleoseismicity of the ovindoli pezza fault central apennines italy a history including a large previously unrecorded earthquake in the middle ages 860 1300 a d geomorphic and trenching investigations along the ovindoli pezza fault show that this normal fault is one of the major seismogenic faults in the central apennines we found clear geological evidence for three holocene surface faulting earthquakes on this fault the most recent earthquake occurred in the middle ages between 860 and 1300 a d the penultimate occurred about 1900 b c or shortly after and the oldest probably occurred between 3300 and 5000 b c although the most recent surface faulting earthquake occurred during historical time no evidence for it have been found in the historical record slip per event ranges between 2 and 3 m and the length of the rupture is at least 12 20 km suggesting m 6 5 7 0 for the paleoearthquakes the dip slip rate determined from trenching is 0 7 1 2 mm yr and is consistent with the long term slip rate of 0 9 2 5 mm yr lower values preferred obtained from displaced geomorphic features trench data combined with long term slip rate estimates suggest the recurrence interval is longer than a millennium and possibly as long as 3300 years the time elapsed since the most recent earthquake is 700 1130 years the seismic behavior of the ovindoli pezza fault is consistent with other well known seismogenic faults of the central and southern apennines the lack of mention or mislocation of the most recent event on the ovindoli pezza fault in the historical record of the past two millennia should be attributed mainly to the unsettled cultural and social conditions and poor economic state that characterized the middle ages especially in thinly populated regions such as the central apennines this example highlights an intrinsic limit of the historical data and raises the possibility that other regions considered seismically quiet on the basis of a long historical record may in reality have had large earthquakes that were not recorded

slip distribution of the 1997 umbria marche earthquake sequence joint inversion of gps and synthetic aperture radar interferometry data 1 in september october 1997 a seismic sequence struck the southern part of the umbria marche region in central italy the three largest earthquakes took place on 26 september 0033 ut mw 5 7 09 40 gu mw 6 0 near colfiorito and on 14 october mw 5 6 near sellano we present a slip model for the main sequence over two separate fault planes we use previously published global positioning system gps and differential interferometric synthetic aperture radar dinsar data as well as new dinsar data covering the sellano event as input to a simulated annealing solution for the distribution of fault slip the combination of both types of geodetic data as well as the combination of sar interferograms from both ascending and descending satellite tracks allows us to make a more complete geodetically based assessment of the fault slip for these earthquakes for the solutions presented here we required the slip distribution to match the observed surface displacements while maintaining a total scalar seismic moment approximately equal to the seismologically inferred moments for this sequence we find the slip was concentrated in a zone at 4 5 5 km depth with a shallower tail extending to near the surface at the northern end of the colfiorito sequence for both the second colfiorito event and the sellano event individual patches were calculated with maximum slip of 2 m implying stress drops as high as 20 mpa coulomb stress calculations show that the coseismic slip distribution for the colfiorito events facilitated slip of the adjacent sellano earthquake

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