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

using in situ chlorine 36 cosmonuclide to recover past earthquake histories on limestone normal fault scarps a reappraisal of methodology and interpretations cosmic ray exposure dating of preserved seismically exhumed limestone normal fault scarps has been used to identify the last few major earthquakes on seismogenic faults and recover their ages and displacements through the modelling of the content of in situ 36cl cosmonuclide of the scarp rocks however previous studies neglected some parameters that contribute to 36cl accumulation and the uncertainties on the inferred earthquake parameters were not discussed to better constrain earthquake parameters and to explore the limits of this palaeoseismological method we developed a matlab modelling code provided in supplementary information that includes all the factors that may affect 36cl observed in seismically exhumed limestone fault scarp rocks through a series of synthetic profiles we examine the effects of each factor on the resulting 36cl and quantify the uncertainties related to the variability of those factors those most affecting the concentrations are rock composition site location shielding resulting from the geometry of the fault scarp and associated colluvium and scarp denudation in addition 36cl production mechanisms and rates are still being refined but the importance of these epistemic uncertainties is difficult to assess we then examine how pre exposure and exposure histories of fault zone materials are expressed in 36cl profiles we show that the 36cl approach allows unambiguous discrimination of sporadic slip versus continuous creep on these faults it allows identification of the large slip events that have contributed to the scarp exhumation and provides their displacement with an uncertainty of 25 cm and their age with an uncertainty of 0 5 1 0 kyr by contrast the modelling cannot discriminate whether a slip event is a single event or is composed of multiple events made of temporally clustered smaller size events as a result the number of earthquakes identified is always a minimum while the estimated displacements are maximum bounds and the ages the approximate times when a large earthquake or a cluster of smaller earthquakes have occurred we applied our approach to a data set available on the magnola normal fault central italy including new samples from the buried part of the scarp reprocessing of the data helps to refine the seismic history of the fault and quantify the uncertainties in the number of earthquakes their ages and displacements we find that the magnola fault has ruptured during at least five large earthquakes or earthquake clusters in the last 7 ka and may presently be in a phase of intense activity

self similarity of the largest scale segmentation of the faults implications for earthquake behavior article i nfo article history earthquakes are sensitive to the along strike segmentation of the faults they break especially in their initiation propagation and arrest we examine that segmentation and search whether it shows any specific properties we focus on the largest scale fault segmentation which controls the largest earthquakes it is well established that major segments within faults markedly shape their surface cumulative slip length profiles segments appear as large slip bumps separated by narrow pronounced slip troughs inter segments we use that property to examine the distribution location number length of the major segments in 927 active normal faults in afar east africa of various lengths 0 3 65 km cumulative slips 1 1300 m slip rates 0 5 5 mm yr and ages 10 4 10 6 yr this is the largest fault population ever analyzed to identify the major bumps in the slip profiles and determine their number location and length we analyze the profiles using both the classical fourier transform and a space frequency representation of the profiles the s transform which is well adapted for characterizing local spectral properties our work reveals the fol lowing results irrespective of their length 70 of the slip profiles have a triangular envelope shape in conflict with the elastic crack concept irrespective of their length the majority of the faults at least 50 70 have a limited number of major segments between 2 and 5 and more commonly equal to 3 5 the largest scale segmentation of the faults is thus self similar and likely to be controlled by the fault mechanics the slip deficits at the major inter segment slip troughs tend to smooth as the faults accumulate more slip resulting in increased connection of the major segments the faults having accumulated more slip therefore generally appear as un segmented 10 30 our observations therefore show that whatever the fault on which they initiate large earthquakes face the same number of major segments to potentially break the number of segments that they eventually break seems to depend on the slip history structural maturity of the fault

hydro geomorphic controls on the development and distribution of acid sulfate soils in central java indonesia abstract coastal planning policies and regulations in indonesia have not adequately considered acid sulfate soils ass as a constraint on development aquaculture is often undertaken in unsuitable areas and fish and shrimp culture systems in particular fail after a short period of production because of the impacts of ass on pond water quality and subsequently on fish and shrimp health this study describes a mapping approach based on an understanding of the hydro geomorphic controls on the formation and the distribution of ass in central java indonesia the underlying approach was to identify associations between ass development and distribution within estuarine hydro geomorphological units hgus this study utilized a multi level methodology involving multi resolution remotely sensed data and gis analysis coupled with field and laboratory based data to obtain hydro geomorphic and soil information at different mapping scales an estuary classification scheme for central java identified river tide and wave dominated estuaries as the dominant estuary types hgus were identified in each estuary type to define the relationships between landform development processes and pyrite concentration in soil layers thirty nine hgus were classified based on landforms marine and fluvial hydrology geomorphic processes land use and vegetation types field and laboratory assessment of soil properties were undertaken to identify the horizontal distribution of ass in the hgus and its vertical character in soil profiles in contrast to previous studies the results showed that estuaries located in low energy environments on the north coast have low

dependency of near field ground motions on the structural maturity of the ruptured faults little work has been undertaken to examine the role of specific long term fault properties on earthquake ground motions here we empirically examine the influence of the structural maturity of faults on the strong ground motions generated by the rupture of these faults and we compare the influence of fault maturity to that of other source properties slip mode and blind versus surface rupturing we analyze the near field ground motions recorded at rock sites for 28 large mw 5 6 7 8 crustal earthquakes of various slip modes the structural maturity of the faults broken by those earthquakes is classified into three classes mature intermediate and immature based on the combined knowledge of the age slip rate cumulative slip and length of the faults we compare the recorded ground motions to the empirical prediction equation of boore et al 1997 at all frequencies earthquakes on immature faults produce ground motions 1 5 times larger than those generated by earthquakes on mature faults the fault maturity appears to be associated with larger differences in ground motion amplitude than the style of faulting factor of 1 35 between reverse and strike slip earthquakes and the surface rupture occurrence factor of 1 2 between blind and surface rupturing earthquakes however the slip mode and the fault maturity are dependent parameters and we suggest that the effect of slip mode may only be apparent actually resulting from the maturity control we conclude that the structural maturity of faults is an important parameter that should be considered in seismic hazard assessment

changing views of the san andreas fault the magnitude 7 0 earthquake that struck haiti on 12 january 2010 is a reminder of the devastation caused by large earthquakes because recurrence of large m 7 8 earthquakes is rare on the order of centuries studying the past behavior of a fault guides future expectations paleoseismologists examine the stratigraphic and geomorphic history of deposits and landforms along a fault for evidence of past ruptures such observations provide information on when earthquakes happened what parts of the fault failed and the size of the earthquakes the collected geologic data form the backbone of probabilistic seismic hazard analyses 1 used by the insurance and engineering industries and are increasingly used to explore models of lithosphere rheology and fault interaction 2 3 because of sparse data however inferences about patterns of strain accumulation and release are a common occurrence on pages 1119 and 1117 of this issue zielke et al 4 and grant ludwig et al 5 present data and interpretations providing an exciting new view that questions fault behavior models that have been applied to the south central san andreas fault for decades highlighting the value of revisiting old problems with new techniques

past and future earthquakes on the san andreas fault the san andreas fault in calfornia is one of the best studied earthquake generating faults in the world in their perspective weldon et al discuss recent efforts to construct rupture scenarios that is possible histories of the date location and length of fault rupture of past earthquakes on the fault existing knowledge of the locations and dates of past earthquakes can be explained by different scenarios but the authors argue that the evidence favors the hypothesis that the fault breaks in relatively infrequent large earthquakes they caution that the current 148 year hiatus since the last big earthquake is likely to end within the next 50 years with a large rupture or sequence of ruptures spanning a substantial part of the fault

determining the present day kinematics of the idrija fault slovenia from airborne lidar topography abstract located in central europe at the junction of the southern alps and the dinarides the 100 km long idrija fault striking n310 and dipping 80 ne is often considered as the potential source of the historical 1511 earthquake estimated macroseismic magnitude mm 6 8 using 1 25 000 to 1 5000 topographical maps satellite images spot5 12 5 m illuminated dem and airborne lidar data derived 1 m dem we examined in detail the idrija fault trace along a 20 km long swath in the central portion of the fault combining topographic and remote sensing data allows characterizing the recent activity along the idrija fault and estimating its cumulative displacement along strike between tolmin and godovic the fault trace is mostly linear but appears divided into three disconnected segments of 11 20 km long morphological evidences such as offset streams and ridges and major drainage abandonments suggest ongoing movement at three sites field observations and lidar dem analysis allow measuring cumulative dextral offsets comprised between 35 and 65 m we found two larger offsets of 140 m and 360 m at the southeasternmost site the vertical component is significant and revealed by a rake ranging from 0 to 33 the derived n303 n310 striking slip vector is in agreement with the motion along this fault as suggested by the geodesy assuming that the smallest measured offsets have been recorded after the last glacial maximum lgm about 20 ka ago the minimum slip rate for the idrija fault is about 1 5 mm yr over this period of time

earthquake supercycles inferred from sea level changes recorded in the corals of west sumatra records of relative sea level change extracted from corals of the mentawai islands sumatra imply that this 700 kilometer long section of the sunda megathrust has generated broadly similar sequences of great earthquakes about every two centuries for at least the past 700 years the moment magnitude 8 4 earthquake of september 2007 represents the first in a series of large partial failures of the mentawai section that will probably be completed within the next several decades

the application of radiocarbon age estimates to the dating of glacial sequences an example from the miami sublobe ohio u s a abstract despite the importance of dating glacial sequences little evidence has been available to highlight the stratigraphic issues associated with the interpretation of age analysis a compilation of radiocarbon data from the miami sublobe of the laurentide ice sheet provides a large enough data set more than 133 dates to identify at least two sources of error sample and unit variability and transportation problems analysis of different samples from the same stratigraphic level commonly differ by more than the reported one sigma error and 2 000 year differences do occur glacial entrainment and transportation emplace older organic material over younger in situ materials and this effect may also give age errors in the data set of up to 2 000 years at a minimum multiple radiocarbon ages from a sequence of units are necessary to assign a reliable age to events within a glacial sequence however representing multiple ages poses its own problems a graphical representation that combines the probability of each sample appears to be one solution

post glacial slip history of the sparta fault greece determined by 36cl cosmogenic dating evidence for non periodic earthquakes 1 using 36cl cosmic ray exposure dating we obtained continuous exposure histories for 7 12 m high limestone surfaces at two sites 10 km apart on the sparta normal fault scarp as each major earthquake adds new surface to the cumulative scarp exposing new material to cosmic ray bombardment these exposure histories allow the slip history to be constrained the results show that an earthquake occurred on this fault 2800 300 yr ago we infer that this is the seismic event that destroyed ancient sparta in 464 b c four earlier earthquakes ruptured the sparta fault in the last 13 ka with similar slip amplitudes of about 2 m and with time intervals ranging from 500 yr to 4500 yr the observations also confirm that the sparta scarp is post glacial supporting the hypothesis that similar scarps elsewhere in the mediterranean region have a comparable age the absence of any event since 464 b c could suggest a future event is imminent however the irregularity of earthquake time intervals could also be due to changes of loading with important consequences for the mechanics of continental deformation

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

morphology displacement and slip rates along the north anatolian fault turkey 1 geological and geomorphological offsets at different scales are used to constrain the localization of deformation total displacement and slip rates over various timescales along the central and eastern north anatolian fault naf in turkey the naf total displacement is reevaluated using large rivers valleys 80 15 km and structural markers pontide suture 85 25 km tosya vezirkopru basins 80 10 km these suggest a neogene slip rate of 6 5 mm yr over 13 myr the river network morphology shows offsets at a range of scales 20 m to 14 km across the main fault trace and is also used to estimate the degree to which deformation is localized at a smaller scale the morphology associated with small rivers is offset by 200 m along the naf the age of these features can be correlated with the holocene deglaciation and a slip rate of 18 3 5 mm yr is determined this is consistent with a rate of 18 5 mm yr deduced independently from the 14c dating of stream terrace offsets over the short term gps data gives a similar rate of 22 3 mm yr all our results tend to show that most of the deformation between the anatolian and eurasian lithospheric plates has been accommodated along or very close to the active trace of the naf the difference between the neogene and the holocene slip rate may be due to the recent establishment of the current plate geometry after the creation of the naf

calibration of cosmogenic 36cl production rates from ca and k spallation in lava flows from mt etna 38 n italy and payun matru 36 s argentina abstract published cosmogenic 36cl production rates from ca and k spallation differ by almost a factor of 2 in this paper we determine production rates of 36cl from ca and k in samples of known age containing little cl ca rich plagioclases and k feldspars were separated from a total of 13 samples collected on the surfaces of four basaltic lava flows at mt etna 38 n italy and from a trachyte lava flow at payun matru volcano 36 s argentina eruption ages determined by independent methods range between 0 4 and 32 ka sample site elevations range between 500 and 2500 m corresponding scaling factors were calculated using five different published scaling models four of which consider paleo geomagnetic field variations integrated over the exposure durations the resulting five data sets were then analyzed using a bayesian statistical model that incorporates the major inherent uncertainties in a consistent way spallation production rates from ca and k considering all major uncertainties are 42 2 4 8 atoms 36cl g ca 1 a 1 and 124 9 8 1 atoms 36cl g k 1 a 1 normalized to sea level and high latitude using the scaling method of stone 2000 scaling models that account for paleo geomagnetic intensity changes yield very similar mean values at most 4 if the uncertainties in the independent ages are neglected in the bayesian model the calculated element specific production rates would be about 12 higher our results are in agreement with previous production rate estimations both for ca and k if only low cl i e 20 ppm samples are considered

considerations on the significance of some post glacial fault scarps in the abruzzo apennines central italy abstract in this paper the tectonic and palaeoseismological significance of the fault scarps present in the massifs of the velino and of mount greco and in the plains adjacent to these massifs forming part of the abruzzo apennines is discussed the basic features of post glacial fault scarps already mentioned in the literature are illustrated found in the fucino plain in the ovindoli piani di pezza area on the mount magnola in the valle majelama alluvial fan and in the piano di aremogna others not previously mentioned surveyed by the author in the mount ocre cefalone area in the piana di corvaro and on the mount greco toppe del tesoro are also discussed on the basis of the characteristics of these scarps and of the chronological framework of the last phases of activity of the faults which gave rise to the scarps described the reliability of the assumptions made for palaeoseismological studies in other places is discussed for the abruzzo area the studies performed in the area of the velino and greco massifs suggest that to establish the possible co seismical activity of the faults the use of morphological indices and also of the results obtained with the excavation of trenches has to be very cautiously applied it is considered that the following can be stated it is probable that the majority of the mentioned fault scarps are co seismic in view of the height of some fault scarps it cannot be excluded that they were formed during the course of earthquake sequences lasting not more that 2 3000 years it is possible that some of the above mentioned scarps were produced during seismic events of great magnitude it does not seem possible at present to calculate a precise slip rate the amount of the offset often changes along the same fault even over short distances moreover there are many horst and graben type structures produced by local effects which contribute towards making an assessment of the fault offsets complicated it is also clear that erosion can change the aspect of the scarps an evaluation of the displacements caused by the faults producing them must therefore be made extremely cautiously caution is needed in assessing the magnitude of past earthquakes and in assuming recurrence intervals the dating of the phases of fault activity is approximate and there is great difficulty in recognizing with any certainty the duration the sort of activity and the length of the fault segment concerned in the activity moreover the existence in the past of aseismic creep and of movements linked to post glacial isostatic rebound cannot be excluded with any certainty these considerations must be regarded for the two massifs examined since there have been the epicentres of rare earthquakes of low intensity the only large earthquake known in history which caused surface ruptures occurred in the fucino area in 1915 the fault scarps reported in this paper seem however interpretable in general as indications of post glacial tectonic activity the intensity of which was unsuspected until a few years ago

spatiotemporal complexity of continental intraplate seismicity insights from geodynamic modeling and implications for seismic hazard estimation continental intraplate seismicity seems often episodic clustered and mi grating the observed seismicity shows both spatial clustering in seismic zones and scattering across large plate interiors temporal clustering followed by long periods of quiescence and migration of seismicity from one seismic zone to another here we explore the complex spatiotemporal patterns of intraplate seismicity using a 3d visco elasto plastic finite element model the model simulates tectonic loading crustal failure in earthquakes and coseismic and postseismic stress evolution for a later ally homogeneous lithosphere with randomly prespecified perturbations of crustal strength the model predicts various spatiotemporal patterns of seismicity at different timescales spatial clustering in narrow belts and scattering across large regions over hundreds of years connected seismic belts over thousands of years and widely scat tered seismicity over tens of thousands of years the orientation of seismic belts coincides with the optimal failure directions associated with the assumed tectonic loading stress triggering and migration cause spatiotemporal clustering of earth quakes when weak zones are included in the model the predicted seismicity initiates within the weak zones but then extends far beyond them if a fault zone is weakened following a large earthquake repeated large earthquakes can occur on the same fault zone even in the absence of strong tectonic loading these complex spatiotemporal patterns of intraplate seismicity predicted in this simple model suggest that assessment of earthquake hazard based on the limited historic record may be biased toward over estimating the hazard in regions of recent large earthquakes and underestimating the hazard where seismicity has been low during the historic record

complex deformation at shallow depth during the 30 october 2016 m w 6 5 norcia earthquake interference between tectonic and gravity processes the relation between slip at the near surface and at depth during earthquakes is still not fully resolved at the moment this deficiency leads to large uncertainties in the evaluation of the magnitude of past earthquakes based on surface observations which is the only accessible evidence for such events a better knowledge of the way slip distributes over distinct rupture strands within the first few kilometers from the surface would contribute greatly to reduce these uncertainties the 30 october 2016 mw6 5 norcia earthquake has been captured by a variety of geodetic techniques which provide access to the slip distribution both at depth and at the ground surface with an unprecedented level of detail for a normal faulting earthquake we first present coseismic surface offset measurements from correlation of optical satellite images of submetric resolution which are compared to field observations made shortly after the earthquake based on a joint inversion of optical data together with insar and gps data we then propose a rupture model that explains the observations both at far field and near field scales finally we explore different rupture geometries at shallow depth in an attempt to better explain the near field deformation i e within the first hundreds of meters around the fault observed at the surface despite the fact that the solution is not unique several lines of evidence suggest that gravity processes could be locally involved which interfere with the dominant tectonic processes

comparison of geodetic and geologic data from the wasatch region utah and implications for the spectral character of earth deformation at periods of 10 to 10 million years the wasatch fault and adjacent fault zones provide an opportunity to compare present day deformation rate estimates obtained from space geodesy with geologic displacement rates over at least four temporal windows ranging from the last millennium up to 10 myr the three easternmost gps sites of the basin and range geodetic network bargen at this latitude define a 130 km wide region spanning three major normal faults extending east west at a total rate of 2 7 0 4 mm yr with an average regional strain rate estimated to be 21 4 nstrain yr about twice the basin and range average on the wasatch fault the vertical component of the geologic displacement rate is 1 7 0 5 mm yr since 6 ka 0 6 mm yr since 130 ka and 0 5 0 7 mm yr since 10 ma however it appears likely that at the longest timescale rates slowed over time from 1 0 to 1 4 mm yr between 10 and 6 ma to 0 2 to 0 3 mm yr since 6 ma the cumulative vertical displacement record across all three faults also shows time variable strain release ranging from 2 to 4 mm yr since 10 ka to 1 mm yr averaged over the past 130 kyr conventional earthquake recurrence models reid type behavior would require an accordingly large variation in strain accumulation or loading rate on a 10 kyr timescale for which there appears to be no obvious geophysical explanation alternatively seismic strain release given a wide range of plausible constitutive behaviors for frictional sliding may be clustered on the 10 kyr timescale resulting in the high holocene rates with comparatively low uniform strain accumulation rates on the 100 kyr timescale wallace type behavior the latter alternative combined with observations at the million year timescale and the likelihood of a significant contribution of postseismic transients implies maxima of spectral amplitude in the velocity field at periods of 10 myr variations in tectonic loading 10 kyr clustered strain release and of 100 years postseismic transients if so measurements of strain accumulation and strain release may be strongly timescale dependent for any given fault system

relationships between fault geometry slip rate variability and earthquake recurrence in extensional settings field observations and modelling indicate that elastic interaction between active faults can lead to variations in earthquake recurrence intervals measured on timescales of 102 104 yr fault geometry strongly influences the nature of the interaction between adjacent structures as it controls the spatial redistribution of stress when rupture occurs in this paper we use a previously published numerical model for elastic interaction between spontaneously growing faults to investigate the relationships between fault geometry fault slip rate variations and the statistics of earthquake recurrence these relationships develop and become systematic as a long term consequence of stress redistribution in individual rupture events even though on short timescales earthquake activity appears to be stochastic we characterize fault behaviour using the coefficient of variation cv of earthquake recurrence intervals and introduce a new measure slip rate variability srv that takes into account the size and time ordering of slip events cv generally increases when the strain is partitioned on more than one fault but the relationship between long term fault slip rate srmean and cv is poorly defined in contrast srv increases systematically where faulting is more distributed and srmean is lower to first order srv is inversely proportional to srmean we also extract earthquake recurrence statistics and compare these to previously published probability density functions used in earthquake forecasting the histograms of earthquake recurrence vary systematically as a function of fault geometry and are best characterized by a weibull distribution with fitting parameters that vary from site to site along the fault array we explain these phenomena in terms of a time varying geometrical control on stress loading of individual faults arising from the history of elastic interactions and compare our results with published data on srv and earthquake recurrence along normal faults in new zealand and in the italian apennines our results suggest that palaeoseismic data should be collected and analysed with structural geometry in mind and that information on srv cv and srmean should be integrated with data from earthquake catalogues when evaluating seismic hazard

evidence for self similar triangular slip distributions on earthquakes implications for earthquake and fault mechanics we characterize average slip distributions on earthquakes beyond their individual heterogeneity for that we analyze a large number of seismic slip distributions both measured at the surface after earthquakes 44 profiles and derived from slip inversion models 76 models investigating the overall shape of these slip profiles we find that they are roughly triangular both along strike and dip and most of them 70 80 are asymmetric long linear slopes and high slip gradients therefore are the key ingredients to describe earthquake slip profiles the scaling relations between maximum displacement and length or width suggest furthermore that the triangular slip profiles are self similar such slip patterns make earthquakes dominated by one major zone of maximum slip hence one major asperity analyzing the position of hypocenters with respect to these asperities we find that earthquakes nucleate at a distance from them that averages 20 30 of their total length compiling observations on 56 earthquakes we show that this distance i e the asperity size is structurally defined we then compare the earthquake slip profiles to cumulative slip profiles measured on long term faults of various ages and sizes and find that all profiles have a similar shape triangular and asymmetric hence combining data for a large number of earthquakes leads to point out average generic characteristics of the coseismic slip that are similar to those that emerge from the accumulation of events with time on a single fault this suggests that these characteristics result from robust physical properties

slip accumulation and lateral propagation of active normal faults in afar we investigate fault growth in afar where normal fault systems are known to be currently growing fast and most are propagating to the northwest using digital elevation models we have examined the cumulative slip distribution along 255 faults with lengths ranging from 0 3 to 60 km faults exhibiting the elliptical or bell shaped slip profiles predicted by simple linear elastic fracture mechanics or elastic plastic theories are rare most slip profiles are roughly linear for more than half of their length with overall slopes always 0 035 for the dominant population of nw striking faults and fault systems longer than 2 km the slip profiles are asymmetric with slip being maximum near the eastern ends of the profiles where it drops abruptly to zero whereas slip decreases roughly linearly and tapers in the direction of overall aden rift propagation at a more detailed level most faults appear to be composed of distinct shorter subfaults or segments whose slip profiles while different from one to the next combine to produce the roughly linear overall slip decrease along the entire fault on a larger scale faults cluster into kinematically coupled systems along which the slip on any scale individual fault or fault system complements that of its neighbors so that the total slip of the whole system is roughly linearly related to its length with an average slope again 0 035 we discuss the origin of these quasilinear asymmetric profiles in terms of initiation points where slip starts and barriers where fault propagation is arrested in the absence of a barrier slip apparently extends with a roughly linear profile tapered in the direction of fault propagation

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

east west extension and holocene normal fault scarps in the hellenic arc examination of surface fault traces with spot images and in the field corroborates the inference that the active tectonics of southern peloponnesus and crete are dominated by approximately north south normal faulting and approximately east west extension the heights of holocene normal fault scarps yield first order regional estimates of fault slip rates between 0 1 and 2 3 mm yr most of the surface scarps probably ruptured during past earthquakes such as that which destroyed sparta in 464 b c on the sparta fault the holocene average slip rate and the recurrence time of large earthquakes may be 1 mm yr and 3000 yr respectively the regional pattern of quaternary faulting suggests that the east west extension near the hellenic subduction zone is fast about 5 10 m y the change from north south to east west extension in the late pliocene 2 4 ma implies that the aegean is starting to collide with the northern margin of africa

coseismic slip and afterslip of the great mw 9 15 sumatra andaman earthquake of 2004 we determine coseismic and the first month postseismic deformation associated with the sumatra andaman earthquake of 26 december 2004 from near field global positioning system gps surveys in northwestern sumatra and along the nicobar andaman islands continuous and campaign gps measurements from thailand and malaysia and in situ and remotely sensed observations of the vertical motion of coral reefs the coseismic model shows that the sunda subduction mega thrust ruptured over a distance of about 1500 km and a width of less than 150 km releasing a total moment of 6 7 7 0 10 22 n m equivalent to a magnitude m w 9 15 the latitudinal distribution of released moment in our model has three distinct peaks at about 4 n 7 n and 9 n which compares well to the latitudinal variations seen in the seismic inversion and of the analysis of radiated t waves our coseismic model is also consistent with interpretation of normal modes and with the amplitude of very long period surface waves the tsunami predicted from this model fits rela tively well the altimetric measurements made by the jason and topex satellites neither slow nor delayed slip is needed to explain the normal modes and the tsunami wave the near field geodetic data that encompass both coseismic deformation and up to 40 days of postseismic deformation require that slip must have continued on the plate interface after the 500 sec long seismic rupture the postseismic geodetic moment of about 2 4 10 22 nm mw 8 8 is equal to about 30 5 of the coseismic moment release evolution of postseismic deformation is consistent with rate strengthening frictional afterslip online material summary of geodetic data used in this study

episodic behavior of the jordan valley section of the dead sea fault inferred from a 14 ka long integrated catalog of large earthquakes the continuous record of large surface rupturing earthquakes along the dead sea fault brings unprecedented insights for paleoseismic and archaeoseismic research in most recent studies paleoseismic trenching documents the late holocene faulting activity while tectonic geomorphology addresses the long term behavior 10 ka with a tendency to smooth the effect of individual earthquake rupture events m w 7 here we combine historical archaeological and paleoseismic investigations to build a consolidated catalog of destructive surface rupturing earthquakes for the last 14 ka along the left lateral jordan valley fault segment the 120 km long fault segment limited to the north and the south by major pull apart basins the hula and the dead sea respectively is mapped in detail and shows five subsegments with narrow stepovers width 3 km we conducted quantitative geomorphology along the fault measured more than 20 offset drainages excavated four trenches at two sites and investigated archaeological sites with seismic damage in the jordan valley our results in paleoseismic trenching with 28 radiocarbon datings and the archaeoseismology at tell saydiyeh supplemented with a rich historical seismic record document 12 surface rupturing events along the fault segment with a mean interval of 1160 yr and an average 5 mm yr slip rate for the last 25 ka the most complete part of the catalog indicates recurrence intervals that vary from 280 yr to 1500 yr with a median value of 790 yr and suggests an episodic behavior for the jordan valley fault our study allows a better constraint of the seismic cycle and related short term variations late holocene versus long term behavior holocene and late pleistocene of a major continental transform fault

incorporating and reporting uncertainties in fault slip rates 1 quantitative slip rate estimates are essential to understanding crustal deformation processes and assessing seismic hazard computing slip rates requires two fundamental ingredients estimates of the age of an offset landforrn or deposit and displacement along the fault of interest because both of these measures contain uncertainty slip rates are inherently uncertain methods to compute and report slip rates have not been standardized and therefore slip rate data are presented inconsistently and are frequently ambiguous in particular slip rate uncertainty is often insufficiently characterized we present a rigorous probabilistic approach to computing and reporting intermediate to long term fault slip rates additionally we have developed freely available software that provides standard age and displacement uncertainty models we demonstrate the method using recent observations from the neodani and death valley fish lake valley fault zones and we compare slip rates determined using this approach with previously published results

coseismic and initial postseismic deformation from the 2004 parkfield california earthquake observed by global positioning system electronic distance meter creepmeters and borehole strainmeters global positioning system gps electronic distance meter creepmeter and strainmeter measurements spanning the m 6 0 parkfield california earthquake are examined using these data from 100 sec through 9 months following the mainshock the omori s law with rate inversely related to time 1 t p and p ranging between 0 7 and 1 3 characterizes the time dependent deformation during the postseismic period these results are consistent with creep models for elastic solids with an accurate function of postseismic response the coseismic displacements can be estimated from the high rate 1 min sampling gps and the coseismic displacements are approximately 75 of those estimated from the daily solutions consequently fault slip models using daily solutions overestimate coseismic slip in addition at 2 months and at 8 months following the mainshock postseismic displacements are modeled as slip on the san andreas fault with a lower bound on the moment exceeding that of the coseismic moment online material data description and supplementary figures tables and data used in models and time series analysis

aftershocks of the campania lucania italy earthquake of 23 november 1980 abstract the result of a study of 1130 aftershocks of the 1980 campania lucania earthquake are presented the data were collected primarily with a dense array of portable smoked drum seismographs deployed in the epicentral region a few days after the main shock tests performed on subsets of the data to establish the location accuracy are described in detail and epicentral maps and cross sections are presented and discussed one hundred and sixty well constrained fault plane solutions using upward traveling rays are presented the distribution of aftershocks forms an elongate cloud which does not define a plane this is not because the events are poorly located a subset of events located with epicentral errors of less than 1 km and depth errors less than 2 km forms a similar cloud to the complete aftershock set the aftershock mechanisms are very varied some are similar to the main event but many differ profoundly these include events on shallow or vertical planes and thrust events the latter include some events which require contraction in the direction in which the main event indicates extension the aftershocks of all mechanisms are intermixed in space in such a way that no simple system of faults can explain them a model to explain the aftershocks and the lack of surface ruptures in the main event is offered it is proposed that the main shock cuts between two aseismic detachment surfaces and that the aftershocks are a consequence of the complicated deformation that such a geometry demands whatever interpretation is adopted the results are a challenge to the commonly accepted view that aftershocks even approximately define simple fault planes or that aftershock mechanisms replicate the mechanism of the main shock defects in interpretations of the main shock and aftershocks process arise largely from a lack of information about the geometry of structures at depth in the epicentral region suitable deep reflection profiles could help to resolve this problem

deep seated gravitational slope deformation large scale rock failure and active normal faulting along mt morrone sulmona basin central italy geomorphological and paleoseismological analyses abstract active faulting is one of the main factors that induce deep seated gravitational slope deformations dgsds in this study we investigate the relationships between the tectonic activity of the nw se normal fault system along mt morrone central apennines italy and the evolution of the associated sackung type dgsd the fault system is considered to be the source of m 6 5 7 earthquakes our investigations have revealed that the dgsd began to affect the mt morrone sw slope after the early pleistocene this was due to the progressive slope instability arising from the onset of the younger western fault with the older eastern fault acting as the preferred sliding zone paleoseismological investigations based on the excavation of slope deposits across gravitational troughs revealed that the dgsd was also responsible for the displacement of late pleistocene holocene sediments accumulated in the sackung troughs moreover we observed that the investigated dgsd can evolve into large scale rock slides therefore as well as active normal faulting the dgsd should be considered as the source of a further geological hazard overall our approach can be successfully applied to other contexts where active normal faults control the inception and evolution of a dgsd

complex normal faulting in the apennines thrust and fold belt the 1997 seismic sequence in central italy a long sequence of moderate magnitude earthquakes 5 m 6 struck central italy in september and october 1997 at the end of the sequence a year later the seismogenic area extends for about 60 km along the apennines the analysis of historical seismicity suggests that this seismic sequence filled a 700 year gap in this portion of the chain other historical sequences in the same area are characterized by prolonged seismic release on adjacent fault segments probably due to the in volvement of shallow and complex structures inherited by the compressive tectonics the distribution of seismicity and the fault plane solutions show that the extension in this region is accomplished by normal faults dipping at relatively low angles 40 to the southwest the focal mechanisms of the largest shocks reveal normal faulting with extension perpendicular to the apenninic chain northeast southwest consistently with the quaternary tectonics of the internal sector of the northern apen nine belt and with previous earthquakes in adjacent regions three mainshocks oc curred on distinct 5 to 10 km long fault segments adjacent and slightly offset be tween each other high quality aftershock locations show that seismicity is confined within the sedimentary mesozoic cover in the upper 8 km of the crust and that most of the aftershocks are shallower than the largest shocks which nucleated at 6 km depth faults evidenced by aftershock locations have a planar geometry and show increased complexity toward the surface most of the aftershock focal mechanisms are dominated by normal faulting several strike slip events occurred at shallow depths reactivating portions of pre existing thrust planes that segment the normal fault system the spatiotemporal evolution of seismicity shows a peculiar migration of hypocenters along the strike of the main faults with multiple ruptures and the activation of fault segments before the occurrence of the main rupture episodes

estimating surface rupture length and magnitude of paleoearthquakes from point measurements of rupture displacement we present a method to estimate paleomagnitude and rupture extent from measurements of displacement at a single point on a fault the variability of historic ruptures is summarized in a histogram of normalized slip then scaled to give the probability of finding a given displacement within a rupture for any magnitude considered the histogram can be inverted assuming any magnitude earthquake is as likely as another yielding probability density functions of magnitude and rupture length for any given displacement measurement to improve these distributions we include a term to account for the probability that the earthquake would cause ground rupture and two alternative distributions of earthquake magnitude the gutenberg richter magnitude distribution predicts shorter rupture lengths and smaller magnitudes than does a uniform distribution where any magnitude earthquake is considered equally likely longer ruptures and larger magnitudes than the uniform model are predicted by an alternative magnitude distribution designed to return site average displacement this model is a generalization of the characteristic earthquake model and reasonably describes paleoseismic findings on the southern san andreas fault where slip is accommodated by average displacements of a few meters and earthquake recurrence times of 100 250 years our results should increase the value of paleoseismic displacement measurements for hazard assessment in particular they quantify probability estimates of earthquake magnitude and rupture length where point observations of rupture displacement are available and so can contribute to probabilistic seismic hazard analyses online material rupture profiles used to sample rupture variability

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

slip in the 1857 and earlier large earthquakes along the carrizo plain san andreas fault the moment magnitude mw 7 9 fort tejon earthquake of 1857 with a 350 kilometer long surface rupture was the most recent major earthquake along the south central san andreas fault california based on previous measurements of its surface slip distribution rupture along the 60 kilometer long carrizo segment was thought to control the recurrence of 1857 like earthquakes new high resolution topographic data show that the average slip along the carrizo segment during the 1857 event was 5 3 1 4 meters eliminating the core assumption for a linkage between carrizo segment rupture and recurrence of major earthquakes along the south central san andreas fault earthquake slip along the carrizo segment may recur in earthquake clusters with cumulative slip of 5 meters

source analysis of the 2002 molise southern italy twin earthquakes 10 31 and 11 01 1 on october 31 2002 a moderate size earthquake mw 5 8 occurred in molise region southern italy causing loss of young human lives in a school collapse and destructions in several villages the day after a slightly smaller earthquake happened a few kilometers westward from the first one without making strong damage we use a complete set of seismological data global regional and local including both body and surface waves to better understand the source process of these two events we show that the two earthquakes are similar in terms of hypocentral depth focal mechanism and source kinematics moreover the imaged slip zones are almost contiguous which makes the time delay between the two shocks 29 hours an open question the identified updip rupture propagation has amplified the radiation usually created by such mw 5 8 earthquakes at 15 20 km depth we model a maximum acceleration zone in agreement with location of damaged villages

time variable deformation in the new madrid seismic zone new geodetic measurements show that the new madrid is currently deforming too slowly if at all to account for large earthquakes in the region over the past 5000 years this result together with increasing evidence for temporal clustering and spatial migration of earthquake sequences in continental interiors indicates that either tectonic loading rates or fault properties vary over a few thousand years

grouping and migration of surface faulting and variations in slip rates on faults in the great basin province abstract nonuniformity of the occurrence of large slip events producing surface ruptures on seismogenic faults and variations in slip rate probably characterize seismogenic faulting in the great basin province western united states examples include the grouping of faulting events along the lost river fault idaho changes in tilt rates of the east range and cortez mountains nevada extension of slip along a fault on the northwest flank of the humboldt range nevada and migration or shifting of slip back and forth from one fault to another along subparallel range front faults in dixie valley nevada

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

partial rupture of a locked patch of the sumatra megathrust during the 2007 earthquake sequence the great sumatra andaman earthquake and tsunami of 2004 was a dramatic reminder of the importance of understanding the seismic and tsunami hazards of subduction zones 1 2 3 4 in march 2005 the sunda megathrust ruptured again producing an event 5 of moment magnitude mw 8 6 south of the 2004 rupture area which was the site of a similar event in 1861 ref 6 concern was then focused on the mentawai area where large earthquakes had occurred in 1797 mw 8 8 and 1833 mw 9 0 6 7 two earthquakes one of mw 8 4 and twelve hours later one of mw 7 9 indeed occurred there on 12 september 2007 here we show that these earthquakes ruptured only a fraction of the area ruptured in 1833 and consist of distinct asperities within a patch of the megathrust that had remained locked in the interseismic period this indicates that the same portion of a megathrust can rupture in different patterns depending on whether asperities break as isolated seismic events or cooperate to produce a larger rupture this variability probably arises from the influence of non permanent barriers zones with locally lower pre stress due to the past earthquakes the stress state of the portion of the sunda megathrust that had ruptured in 1833 and 1797 was probably not adequate for the development of a single large rupture in 2007 the moment released in 2007 amounts to only a fraction both of that released in 1833 and of the deficit of moment that had accumulated as a result of interseismic strain since 1833 the potential for a large megathrust event in the mentawai area thus remains large

paleoseismology of the johnson valley kickapoo and homestead valley faults clustering of earthquakes in the eastern california shear zone paleoseismic data from 11 trenches at seven sites excavated across the southern johnson valley kickapoo and homestead valley faults that ruptured in the 1992 landers earthquake as well as the northern johnson valley fault which did not fail in 1992 indicate that the return period for large surface rupturing events in this part of the eastern california shear zone is in the range of 5 15 ka the inferred slip rates based on their respective recurrence intervals are in the range of 0 2 0 6 mm yr for each of the faults studied a previous large earthquake ruptured the southern johnson valley and kickapoo faults about 5 ka b p the northern johnson valley fault also failed at about this time at 5 8 ka b p and may have been part of the same rupture in contrast the penultimate large earthquake that we identify on the homestead valley fault occurred about 15 ka b p much earlier than other faults involved in the 1992 rupture from these observations combined with paleoseismic work by others after the 1992 earth quake it appears that previous events along the southern johnson valley and kick apoo faults were different than those of 1992 and may have involved other fault segments it has been over 5 ka since the most recent rupture on the northern johnson valley fault therefore it is surprising that it did not fail in the 1992 rupture from our observations dextral shear appears to be distributed across the entire eastern california shear zone with individual faults taking only a small proportion of the overall slip release of this regional strain appears to occur in temporal clusters of large earthquakes with the 1992 event apparently the most recent of a sequence of late holocene 0 1 ka earthquakes that have ruptured the nine faults we have trenched in the southwestern mojave desert previous clusters of earthquake activity occurred in the early 8 9 ka and middle 5 6 ka holocene and possibly the latest pleistocene 15 ka

recovering paleoearthquake slip record in a highly dynamic alluvial and tectonic region hope fault new zealand from airborne lidar knowing the slip amplitudes that large earthquakes produced in prehistorical times is one key to anticipate the magnitude of large forthcoming events it is long known that the morphology is preserving remnants of paleoearthquake slips in the form of fault offset landforms however the measured offsets that can be attributed to the most recent paleoearthquakes are generally few along a fault so that they rarely allow recovering the slip distributions and largest slips of these earthquakes we acquired 1 m resolution airborne lidar data on a 30 km stretch of a fast slipping strike slip fault eastern hope fault new zealand located in a region of high alluvial dynamics where landforms are rapidly evolving data analysis reveals 200 offset landforms only 30 allow a good to moderate quality offset measurement from these good to moderate quality measures we recover the slip length distributions and largest slips of the four most recent large paleoearthquakes and find evidence of 4 6 prior events the record suggests that large earthquake slip recurred in multiples of about 4 m along the 30 km stretch although they have larger uncertainties the more numerous lower quality offsets that we also measured reveal a similar earthquake slip record this shows that although offset landforms are partly degraded in dynamically active landscapes they store valuable information on paleoearthquake slips this information might be recovered provided that the morphology is analyzed at high resolution and continuously over a significant fault length remote lidar data are powerful to perform such analyses

displacement history of a limestone normal fault scarp northern israel from cosmogenic 36cl the abundance of cosmogenic 36 cl measured in 41 limestone samples from a 9 m high bedrock fault scarp allows us to construct the 14 kyr fault displacement history of the nahef east normal fault northern israel 300 m above sea level n33 latitude the nahef east fault is one of a series of fault scarps located along the 700 m high zurim escarpment a major geomorphic feature samples at the top of the scarp have the highest nuclide concentrations 79 x 10 4 atoms g rock 1 samples at the base have the lowest 11 x 10 4 atoms g rock 1 using chemical data from the samples nahef east fault scarp geometry and surface and subsurface production rates for the 36 cl producing reactions we have constructed a numerical model that calculates 36 cl accumulation on a scarp through time given a series of unique displacement scenarios the resulting model 36 cl concentrations are compared to those measured in the scarp samples faulting histories that result in a good match between measured and modeled 36 cl abundances show three distinct periods of fault activity during the past 14 kyr with over 6 vertical meters of motion occurring during a 3 kyr time period in the middle holocene smaller amounts of displacement occurred before and after the period of most rapid motion the episodic behavior of the nahef east fault indicates that the average displacement rate of this fault system has varied through time

earthquake clustering inferred from pliocene gilbert type fan deltas in the loreto basin baja california sur mexico a stacked sequence of pliocene gilbert type fan deltas in the loreto basin was shed from the footwall of the dextral normal loreto fault and deposited at the margin of a marine basin during rapid fault controlled subsidence fan delta parasequences coarsen upward from marine siltstone and sandstone at the base through sandy bottomsets and gravelly foresets to gravelly nonmarine topsets each topset unit is capped by a thin shell bed that records marine flooding of the delta plain several mechanisms may have produced repetitive vertical stacking of gilbert deltas 1 autocyclic delta lobe switching 2 eustatic sea level fluctuations 3 climatically controlled fluctuations in sediment input and 4 episodic subsidence produced by temporal clustering of earthquakes we favor hypothesis 4 for several reasons but hypotheses 2 and 3 cannot be rejected at this time earthquake clustering can readily produce episodic subsidence at spatial and temporal scales consistent with stratigraphic trends observed in the loreto basin this model is supported by comparison with paleoseismological studies that document clustering on active faults over a wide range of time scales earthquake clustering is a new concept in basin analysis that may be helpful for understanding repetitive stratigraphy in tectonically active basins

temporal clustering of major earthquakes along individual faults due to post seismic reloading palaeoseismic evidence suggests that earthquake recurrence intervals in some regions can be highly variable with clusters of multiple large events separated by much longer periods of quiescence because post seismic processes have a significant effect on the reloading rate of the coseismic fault we hypothesize that temporal variations in the amount of stress concentrated in the non seismogenic lithosphere can modulate large earthquake recurrence times we explore this hypothesis using simple analogue spring dashpot slider models we find that in the presence of small amounts of environmental noise post seismic stress transfer over timescales much longer than an earthquake cycle may be an important factor in generating clustering behaviour the propensity for the system to be clustered is a function of a non dimensional number that we call the wallace number w w is defined as the average earthquake stress drop divided by the product of the long term geologic strain rate across the fault and the effective viscosity of the system our results indicate that environments with relatively low strain rates and a relatively weak non seismogenic lithosphere are most susceptible to clustering driven by post seismic stress recycling mechanisms

stratigraphic evidence for millennial scale temporal clustering of earthquakes on a continental interior fault holocene mississippi river floodplain deposits new madrid seismic zone usa abstract the earthquake cycles that characterize continental interior areas that are far from active plate boundaries have proven highly cryptic and difficult to resolve we used a novel paleoseismic proxy to address this issue namely we reconstructed holocene mississippi river channels from maps of floodplain strata in order to identify channel perturbations reflective of major displacement events on the high hazard and mid plate reelfoot thrust fault new madrid seismic zone u s a only three discrete slip events are currently documented for the reelfoot fault ad 900 ad 1450 and ad 1812 this study extends this record and thus illustrates the utility of stratigraphic proxies as paleoseismic tools we concurrently offer here some of the first quantified response times for tectonically induced channel pattern changes in large alluvial rivers we identified at least two cycles of pervasive meandering that were interrupted by channel straightening responses occurring upstream of the reelfoot fault scarp these straightening responses initiated at 2244 bc 269 to 1620 bc 220 and ad 900 respectively and each records initiation of a period of reelfoot fault slip after millennia of relative tectonic quiescence the second or new madrid straightening response was triggered by the previously known ad 900 fault slip event and this initial low sinuosity has been protracted until the modern day by the latter ad 1450 and ad 1812 events the first or bondurant straightening response began a period of several hundred to 1400 years of low river sinuosity which evidences a similar period of multiple recurrent displacement events on the reelfoot fault these bondurant events predate the existing paleoseismic record for the reelfoot fault these data offer initial evidence that slip events on the reelfoot fault were temporally clustered on millennial scales and thus offers the first direct evidence for millennial scale clustering of earthquakes on a continental interior fault this carries additional ramifications namely faults that have been quiescent and non hazardous for millennia could re enter an enduring period of recurrent hazardous earthquakes with little warning likewise the reelfoot fault also reveals evidence of temporal clustering of earthquakes on short term cycles months as well as evidence for longer term reactivation cycles 10 4 10 6 years this introduces the possibility that temporal clustering could be hierarchical on some continental interior faults

the role of viscoelastic stress transfer in long term earthquake cascades insights after the central italy 2016 2017 seismic sequence central italy is characterized by a network of active faults that interact in a complex manner coseismic coulomb stress changes have been invoked by several authors to explain the concentration of moderate to strong earthquakes in this region but none has considered the time dependent viscoelastic relaxation of the lower crust and upper mantle as a possible additional source of stress changes at a regional scale here starting from the 1915 m w 6 9 0 2 fucino earthquake we calculated the coseismic plus postseismic coulomb failure stress changes cfs due to eight moderate to strong earthquakes that have struck central italy in the last century and culminated with the 2016 2017 sequence results from this modeling coupled with some synthetic tests simulating normal fault earthquakes with different magnitudes allowed us to highlight the importance of postseismic processes in particular the viscoelastic stress transfer due to events of m w 6 5 can modify the spatial distribution of cfs on a centennial timescale and therefore trigger events at larger distances in addition using these results we identified other earthquake clusters in the historical catalogue last 618 years which like the 1915 2017 series were potentially modulated by both coseismic and postseismic processes finally considering our calculations combined with historical and paleoseismological data we suggest that several faults in central italy may be at present close to failure

long term earthquake clustering a 50 000 year paleoseismic record in the dead sea graben the temporal distribution of earthquakes in the dead sea graben is studied through a 50 000 year paleoseismic record recovered in laminated sediments of the late pleistocene lake lisan paleo dead sea the lisan represents more than 10 times the 4000 years of historical earthquake records it is the longest and most complete paleoseismic record along the dead sea transform and possibly the longest continuous record on earth it includes unique exposures of seismite beds earthquake induced structures associated with slip events on syndepositional faults the seismites are layers consisting of mixtures of fragmented and pulverized laminae the places where the seismites abut syndepositional faults are interpreted as evidence for their formation at the sediment water interface during slip events on these faults thicker sediment accumulation above the seismites in the downthrown blocks indicates that a seismite formed at the water sediment interface on both sides of the fault scarps modern analogs and the association with surface ruptures suggest that each seismite formed during a m l 5 5 earthquake the 230 th 234 u ages of a columnar section obtained by thermal ionization mass spectrometry give a mean recurrence time of 1600 years of m l 5 5 earthquakes in the dead sea graben the earthquakes cluster in 10 000 year periods separated by quiet periods of similar length this distribution implies that a long term behavior of the dead sea transform should be represented by a mean recurrence of at least 20 000 year record this observation has ramifications for seismic hazard assessment based on shorter records

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

slip history of the magnola fault apennines central italy from 36cl surface exposure dating evidence for strong earthquakes over the holocene to better understand the mechanics of deformation in the mediterranean and the role that the convergence between africa and europe plays it is necessary to know the deformation field at different time scales here we use in situ 36 cl surface exposure dating of exposed bedrock fault scarps to determine earthquake time slip histories and to quantify slip rates over the last several thousand years this information allows us to delineate the seismic history of normal faulting within the mediterranean area over that time period we have studied the limestone scarp produced by the magnola fault in the central apennines italy the magnola fault in the fucino area is an active 15 km long normal fault striking wnw and dipping ssw the range front morphology characterised by steep triangular facets separated by v shaped valleys and wine glass canyons suggests that the magnola fault has been active for at least the last several hundred thousand years at the base of the facets the fault cuts limestone bedrock to produce a well preserved normal fault scarp 10 to 12 m high the distribution of 36 cl concentration versus the height along that scarp is best explained by a minimum of five and a maximum of seven successive earthquake exhumations with slips varying between 1 5 and 3 m an age of 5 ka at the base of the scarp and of 12 ka at the top yields a slip rate of 0 8 mm year the absence of any event on this fault during the last 5000 years suggests either that a future event is imminent on the magnola fault or that the fault has entered a quiescent period with

motion on the kaparelli fault greece prior to the 1981 earthquake sequence determined from 36cl cosmogenic dating in february and march 1981 three successive destructive earthquakes occurred at the eastern end of the gulf of corinth the third shock march 4 ms 6 4 ruptured the kaparelli fault about 40 cm of a limestone fault scarp was exhumed by the earthquake each major prehistoric earthquake has added new surface to this cumulative scarp exposing fresh material to cosmic ray bombardment using 36cl cosmic ray exposure dating we have obtained the continuous exposure history for this 4 5 m high limestone surface at two sites about 50 m apart the results suggest that the kaparelli fault has ruptured three times prior to 1981 at 20 3 ka 14 5 0 5 ka and 10 5 0 5 ka with slip amplitudes between 0 6 m and 2 1 m the kaparelli fault appears to have been inactive for 10 thousand years prior to the 1981 event

the origin of compositional variation in basalts recovered by submersible drill from mount glooscap mid atlantic ridge at 36 25 n a large peak in the crestal mountains of the mid atlantic ridge about 16 km west of the amar rift valley at 36 25 n was sampled for basalt with a submersible electric rock core drill on a comparable surficial scale as the famous area twenty eight basalt samples from seven drilling stations have been analyzed for major and trace elements many of the samples come from flows lying under a cover of carbonate rocks and therefore could not have been sampled by a submersible or a dredge through comparisons with published compositional data it appears that unlike famous generated basalts amar generated basalts are on average more evolved and are always lree enriched most of the in and between hole compositional variation can be accounted for by low temperature alteration accumulation of phenocrysts and low pressure relatively low temperature fractional crystallization a source heterogeneous in trace elements or undergoing variable degrees of partial melting is necessary to explain the remaining

repeat times of large earthquakes implications for earthquake mechanics and long term prediction information on the time intervals between large earthquakes is now available for several fault segments along plate boundaries in japan alaska california cascadia and turkey when dates in a sequence are known historically as along much of the nankai trough they provide information on the natural intrinsic variability of the rupture process most sets of repeat times however are dominated by paleoseismic determinations of dates of older large earthquakes which contain measurement uncertainties in addition to intrinsic variability a bayesian technique along with prior information on measurement uncertainties is used to make maximum likelihood estimates of intrinsic repeat time and its normalized standard deviation the coefficient of variation cv it is these intrinsic parameters and their uncertainties that are most useful for understanding the mechanics of earthquakes and for prediction for timescales of a few decades our estimates of intrinsic cv are small 0 to 0 25 for several very active fault segments where deformation is relatively simple large events do not appear to be missing in historic and paleoseismic records and data are available at or near major asperities and away from the ends of rupture zones cv is larger for regions of multibranched faulting overlapping slip near the ends of rupture zones and for data from uplifted terraces at subduction zones a poisson process is an inferior characterization of all of the 11 segments we examined scenarios used by recent working groups that assume either poissonian behavior or renewal processes with cv of 0 5 0 2 for the most active fault segments in the san francisco bay area likely lead to incorrect 30 year probability estimates the hayward fault and perhaps the peninsular segment of the san andreas fault in the san francisco bay area appear to be advanced in their buildup of stress that will be released in future large earthquakes multibranched faulting may account for why the predicted tokai earthquake in japan has not occurred as of 2006 parkfield earthquakes from 1857 to 2004 were characterized by the largest uncertainty of the sequences we studied cv 0 37 which may account for the failure of past predictions the large cv for parkfield fits our hypothesis that relatively weak fault segments are characterized by more irregular earthquake recurrence paleoseismic data from coastal sites along the cascadia subduction zone are characterized by cvs of about 0 3

seismic slip history of the pizzalto fault central apennines italy using in situ produced 36cl cosmic ray exposure dating and rare earth element concentrations morphological and geological observations reveal that most apenninic faults are highly segmented and that the majority of the fault segments are less than 10 km long although these faults have undergone numerous paleoseismological investigations quantitative data remain crucially lacking for a large number of fault segments because such data are essential to understanding how these faults have ruptured and interacted in the past and how they might behave in the future we investigated the holocene seismic history of the pizzalto normal fault a 13 km long fault segment belonging to the pizzalto rotella aremogna fault system in the apennines we collected 44 samples from the pizzalto fault plane exhumed during the holocene and analyzed the 36cl and rare earth element ree contents together the 36cl and ree concentrations show that at least six events have exhumed 4 4 m of the fault scarp between 3 and 1 ka with slip per event values ranging from 0 3 to 1 2 m no major events have been detected over the last 1 kyr the rotella aremogna pizzalto fault system has a clustered earthquake behavior with a mean recurrence time of 1 2 kyr and a low to moderate probability ranging from 4 to 26 of earthquake occurrence over the next 50 years

a new multilayered visco elasto plastic experimental model to study strike slip fault seismic cycle nowadays technological advances in satellite imagery measurements as well as the development of dense geodetic and seismologic networks allow for a detailed analysis of surface deformation associated with active fault seismic cycle however the study of earthquake dynamics faces several limiting factors related to the difficulty to access the deep source of earthquake and to integrate the characteristic time scales of deformation processes that extend from seconds to thousands of years to overcome part of these limitations and better constrain the role and couplings between kinematic and mechanical parameters we have developed a new experimental approach allowing for the simulation of strike slip fault earthquakes and analyze in detail hundreds of successive seismic cycle model rheology is made of multilayered visco elasto plastic analog materials to account for the mechanical behavior of the upper and lower crust and to allow simulating brittle ductile coupling postseismic deformation phase and far field stress transfers the kinematic evolution of the model surface is monitored using an optical system based on subpixel spectral correlation of high resolution digital images first results show that the model succeed in reproducing the deformation mechanisms and surface kinematics associated to the main phases of the seismic cycle indicating that model scaling is satisfactory these results are comforted by using numerical algorithms to study the strain and stress distribution at the surface and at depth along the fault plane our analog modeling approach appears then as an efficient complementary approach to investigate earthquake dynamics

earthquake supercycles in central italy inferred from 36cl exposure dating we use 36cl surface exposure dating to determine the slip release pattern over the last 15 kyr for the velino magnola fault a major active normal fault in central italy we sampled the fault at five well separated sites along its length and modeled the 36cl concentrations measured in the 376 samples we find that the fault broke in at least 9 large earthquakes that occurred in two 5 6 ka long supercycles each cycle included a 4 5 ka long phase of relative quiescence followed by a cluster of at least 3 large earthquakes or earthquake sequences that released most of the accumulated strain in 1 ka all 9 identified events broke the entire fault and produced maximum surface slips of 2 3 m though the velino magnola fault seems presently in a stage of relative quiescence it may re enter a phase of paroxysmal seismic activity in a few hundred of years

paleoseismicity of two historically quiescent faults in australia implications for fault behavior in stable continental regions paleoseismic studies of two historically aseismic quaternary faults in australia confirm that cratonic faults in stable continental regions scr typically have a long term behavior characterized by episodes of activity separated by quiescent intervals of at least 10 000 and commonly 100 000 years or more studies of the approximately 30 km long roopena fault in south australia and the approximately 30 km long hyden fault in western australia document multiple quaternary surface faulting events that are unevenly spaced in time the episodic clustering of events on cratonic scr faults may be related to temporal fluctuations of fault zone fluid pore pressures in a volume of strained crust the long term slip rate on cratonic scr faults is extremely low so the geomorphic expression of many cratonic scr faults is subtle and scarps may be difficult to detect because they are poorly preserved both the roopena and hyden faults are in areas of limited or no significant seismicity these and other faults that we have studied indicate that many potentially hazardous scr faults cannot be recognized solely on the basis of instrumental data or historical earthquakes although cratonic scr faults may appear to be nonhazardous because they have been historically aseismic those that are favorably oriented for movement in the current stress field can and have produced unexpected damaging earthquakes paleoseismic studies of modern and prehistoric scr faulting events provide the basis for understanding of the long term behavior of these faults and ultimately contribute to better seismic hazard assessments

glacier retreat in new zealand during the younger dryas stadial the younger dryas a period of sudden cooling in the northern hemisphere about 12 900 years ago is perhaps the best known example of abrupt climate change but the global extent of the younger dryas is a topic of intense debate particularly in the record of glacial behaviour in new zealand a new reconstruction of the growth and retreat patterns of glaciers in the southern alps in new zealand at the time of the younger dryas supports the suggestion that temperature reductions in the north caused warming and glacial retreat in the southern hemisphere through a series of climate feedbacks the younger dryas during which northern hemisphere temperatures cooled drastically in just a few years is perhaps the best known example of abrupt climate change but its global extent is under debate particularly in the record of glacial behaviour in new zealand these authors present evidence for glacial retreat in new zealand during the younger dryas supporting the hypothesis that northern hemisphere climate changes caused southern hemisphere warming through a series of climate feedbacks millennial scale cold reversals in the high latitudes of both hemispheres interrupted the last transition from full glacial to interglacial climate conditions the presence of the younger dryas stadial 12 9 to 11 7 kyr ago is established throughout much of the northern hemisphere but the global timing nature and extent of the event are not well established evidence in mid to low latitudes of the southern hemisphere in particular has remained perplexing1 2 3 4 5 6 the debate has in part focused on the behaviour of mountain glaciers in new zealand where previous research has found equivocal evidence for the precise timing of increased or reduced ice extent1 2 3 the interhemispheric behaviour of the climate system during the younger dryas thus remains an open question fundamentally limiting our ability to formulate realistic models of global climate dynamics for this time period here we show that new zealand s glaciers retreated after 13 kyr bp at the onset of the younger dryas and in general over the subsequent 1 5 kyr period our evidence is based on detailed landform mapping a high precision 10be chronology7 and reconstruction of former ice extents and snow lines from well preserved cirque moraines our late glacial glacier chronology matches climatic trends in antarctica southern ocean behaviour and variations in atmospheric co2 the evidence points to a distinct warming of the southern mid latitude atmosphere during the younger dryas and a close coupling between new zealand s cryosphere and southern high latitude climate these findings support the hypothesis that extensive winter sea ice and curtailed meridional ocean overturning in the north atlantic led to a strong interhemispheric thermal gradient8 during late glacial times in turn leading to increased upwelling and co2 release from the southern ocean9 thereby triggering southern hemisphere warming during the northern younger dryas

long range and long term fault interactions in southern california paleoseismological data suggest the occurrence of four bursts of seismic moment release in the los angeles region during the past 12 000 yr the historic period appears to be part of an ongoing lull that has persisted for about the past 1000 yr these periods of rapid seismic displacement in the los angeles region have occurred during the lulls between similar bursts of activity observed on the eastern california shear zone in the mojave desert which is now seismically active a kinematic model in which the faults of the greater san andreas system suppress activity on faults in the eastern california shear zone and vice versa can explain the apparent switching of activity between the two fault networks combined with the observation that short term geodetic and longer term geologic rates co vary on major southern california fault systems this suggests that either 1 a temporal cluster of seismic displacements on upper crustal faults increases ductile deformation on their downward extensions or 2 rapid ductile slip in the lower crust beneath faults loads the upper crust driving a seismic cluster we suggest that alternating periods of rapid seismic displacement may be the expected mode of seismicity when two fault systems accommodate the same plate boundary motion and slip on one system suppresses slip on the other

paleoseismic evidence of clustered earthquakes on the san andreas fault in the carrizo plain california exposures we have excavated across the san andreas fault contradict the hypothesis that part of the fault in the carrizo plain is unusually strong and experiences relatively infrequent rupture the exposures record evidence of at least seven surface rupturing earthquakes which have been approximately dated by accelerated mass spectrometry radiocarbon analysis of detrital charcoal and buried in situ plants five large earthquakes have occurred since 1218 a d the most recent earthquake event a was the 1857 fort tejon earthquake which we have associated with 6 6 10 m of dextral slip along the main fault trace the penultimate earthquake event b most likely occurred within the period a d 1405 1510 slip from either events b and c combined or from event b alone totals 7 11 m three earthquakes events c d and e occurred in a temporal cluster prior to event b and after approximately a d 1218 the average recurrence interval within this cluster is 73 116 years depending on assumptions events f and g occurred after 200 years b c a depositional hiatus between events e and f may hide evidence of additional earthquakes events b and d within the carrizo cluster of a d 1218 1510 may correlate with events t a d 1329 1363 and v a d 1465 1495 at pallett creek on the mojave segment of the fault this suggests two fault ruptures similar in length to that of 1857 events c and e apparently did not rupture the mojave section which suggests that the carrizo segment has ruptured independently or in combination with segments to the north irregular repeat times of large earthquakes suggest a pattern of clustered events at the end of seismic supercycles

active oblique extension in the central apennines italy evidence from the fucino region the fucino basin is a flat quaternary depression within the central apennines it is surrounded by active normal faults with small oblique slip components surface faulting was observed along the east side of the basin during the ms 7 0 avezzano earthquake of 1915 in order to understand the kinematics of recent strain better and to assess the seismic hazard of this region we carried out a detailed geomorphic and structural study of the faults around the basin fault scarp heights were accurately measured with total station profiles and vertical slip rates were estimated assuming slope offsets to post date the end of periglacial abrasion 14 4 kyr bp to the north the most prominent fault the magnola fault appears to have an average postglacial throw rate of 0 7 0 3 mm yr 1 and together with the velino fault to be capable of generating earthquakes of maximum magnitudes of 6 9 7 3 with recurrence intervals of 1000 3000 yr east of the basin the serrone parasano and ventrino faults form a right stepping horsetail of the giovenco fault current vertical slip rates on the three former faults appear to be between 0 5 and 1 4 0 5 and 1 0 and 0 3 and 1 1 mm yr 1 respectively infrequent maximum magnitude earthquakes on them may also exceed 7 particularly in the case of coupled rupture with loosely constrained recurrence intervals up to several thousand years the right lateral slip components implied by the most recent slickensides and by geomorphic offsets on the nw se trending normal faults of the area suggest that the blocks they bound rotate counterclockwise consistent with oblique left slip on the nnw sse trending giovenco and ovindoli faults to the east sinistral shear parallel to the latter faults the maximum relief across the magnola fault and the postglacial slope offsets measured suggest that the extension rate across the central apennines might be of the order of 6 3 mm yr 1 in a n20 10 e direction more northerly than hitherto inferred

12 000 year long record of 10 to 13 paleoearthquakes on the yammouneh fault levant fault system lebanon we present results of the first paleoseismic study of the yammouneh fault the main on land segment of the levant fault system within the lebanese restraining bend a trench was excavated in the yammouneh paleolake where the fault cuts through finely laminated sequences of marls and clays first order variations throughout this outstanding stratigraphic record appear to reflect climate change at centennial and millennial scales the lake beds are offset and deformed in a 2 m wide zone coinciding with the mapped fault trace ten to thirteen events are identified extending back more than 12 kyr reliable age bounds on seven of these events constrain the mean seismic return time to 1127 135 yr between 12 ka and 6 4 ka implying that this fault slips in infrequent but large m 7 5 earthquakes our results also provide conclusive evidence that the latest event at this site was the great a d 1202 historical earthquake and suggest that the yammouneh fault might have been the source of a less well known event circa a d 350 these findings combined with previous paleoseismic data from the zebadani valley imply that the parallel faults bounding the beqaa release strain in events with comparable recurrence intervals but significantly different magnitudes our results contribute to document the clustering of large events on the levant fault into centennial episodes such as that during the eleventh through twelfth centuries separated by millennial periods of quiescence and raise the possibility of a m 7 event occurring on the yammouneh fault in the coming century such a scenario should be taken into account in regional seismic hazard assessments and planned for accordingly

rare earth elements record past earthquakes on exhumed limestone fault planes evaluating the timing and size of past earthquakes is a constant challenge in palaeoseismology here we show that rare earth element ree concentrations can be used to constrain the number and slips of major past earthquakes we focus on one of the rare faults worldwide the magnola normal fault italy whose holocene earthquake history is precisely known we analysed 42 samples from along the 10 m that form the surface of the well preserved seismically exhumed fault scarp and seven samples extracted from the fault plane section buried in the ground we show that the first metre of soil contaminates the scarp rocks producing a marked concentration peak in ree similar peaks are recognized on the exhumed scarp at positions that coincide with the transitions between the known past ruptures we conclude that the ree peaks locate palaeoground levels and are excellent markers for the large earthquakes that exhumed the scarp

the repetition of large earthquake ruptures abstract this survey of well documented repeated fault rupture confirms that some faults have exhibited a characteristic behavior during repeated large earthquakes that is the magnitude distribution and style of slip on the fault has repeated during two or more consecutive events in two cases faults exhibit slip functions that vary little from earthquake to earthquake in one other well documented case however fault lengths contrast markedly for two consecutive ruptures but the amount of offset at individual sites was similar adjacent individual patches 10 km or more in length failed singly during one event and in tandem during the other more complex cases of repetition may also represent the failure of several distinct patches the faults of the 1992 landers earthquake provide an instructive example of such complexity together these examples suggest that large earthquakes commonly result from the failure of one or more patches each characterized by a slip function that is roughly invariant through consecutive earthquake cycles the persistence of these slip patches through two or more large earthquakes indicates that some quasi invariant physical property controls the pattern and magnitude of slip these data seem incompatible with theoretical models that produce slip distributions that are highly variable in consecutive large events

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

faulting and earthquake triggering during the 1783 calabria seismic sequence summary between the 1783 february 5 and 1783 march 28 five earthquakes struck the southern part of calabria the main shock february 5 and the first aftershock february 6 devastated the region ene of the messina strait the greatest damage occurred along the foot of the aspromonte mountains south of san giorgio morgeto and along the tyrrhenian coast south of palmi a surface break about 18 km long with several feet of downthrow to the west formed along the cittanova santa cristina fault as a result of the main shock on february 7 a third large shock ruined villages at the foot of the serre mountains north of san giorgio morgeto morphological and structural evidence combined with a reassessment of observations made at the time of the earthquakes suggest that these three shocks were shallow 20 km and related to slip on the west dipping ne striking cittanova sant eufemia palmi scilla and serre normal faults respectively which juxtapose the basement of the aspromonte and serre mountains with the pleistocene deposits of the gioia tauro and mesima basins and border the palmi coastal high the three faults belong to an active rift that stretches from northern calabria to offshore the ionian coast of sicily the spatial coupling between the 1783 events is investigated by resolving changes of coulomb failure stress the main shock 1783 february 5 m 7 on the cittanova and sant eufemia faults increased that stress by several bars on the scilla fault triggering the 1783 february 6 earthquake m 6 5 the cumulative effect of these two shocks was to raise the coulomb stress by more than 1 bar on the sw part of the serre fault which was subsequently the site of the 1783 february 7 shock m 6 5 in turn the first three events increased the stress by about 1 bar on the ne part of this latter fault leading to the 1783 march 1 shock m 5 7 the gap between the 1783 february 7 and 1783 march 1 events may be related to the previous occurrence of an earthquake 124 yr before 1659 november 5 m 6 which had already released stress locally the occurrence of the last 1783 event 28 march is not as simply accounted for by coulomb modelling in part because it remains unclear which fault slipped and how deep this event was overall the 1783 sequence increased the coulomb failure stress by several bars south of the messina strait and north of the epicentral region of the 1693 se sicily catania noto earthquakes 125 yr later this same region was the site of the 1908 messina earthquake also a normal faulting event our study thus provides one convincing example in which coulomb stress modelling brings insight into the spatial dynamics of seismic sequences