uplift deformation and fluid involvement within an active normal fault zone in the gulf of corinth greece the active pisia fault zone is exposed close to the crest of a rotated carbonate fault block that forms part of the southern margin to the gulf of corinth half graben in central greece the crest of the fault block lies above sea level whilst in the hanging wall a marine basin exists as a result the diagenetic and structural characteristics of the fault zone record complex fluid involvement both early phreatic carbonate syn kinematic cements characterized by drusy fabrics baroque dolomites and crack seal textures and late vadose carbonate syn kinematic cements characterized by flowstones containing cave collapse debris exist in the uplifted footwall to the fault downward percolation of vadose meteoric waters and the upwelling of pore waters with elevated temperatures produced the diagenetic features observed within the fault zone the co existence of early phreatic and late vadose cements within the fault zone is related to footwall uplift across the water table and subsequent erosional unroofing the present day elevation of phreatic cements to c 650m above current sea level provides a minimum estimate of footwall uplift along the fault the wider implication is that temporal changes in deformation and fluid flow may typify fault block evolution

active deformation of the continents whereas relatively narrow bands of deformation define oceanic plate boundaries in continental situations deformation is shown to be distributed over much broader zones the complex and heterogeneous nature of boundary regions between major plates is outlined with reference to the mediterranean and the himalayas relatively aseismic regions have traditionally been defined as microplates but although they are presently acting as rigid blocks undergoing slow deformation it is argued that this need not always have been the case and that deformation may simply have moved elsewhere broad zones of deformation surrounding rigid blocks are highlighted as fundamental to the analysis and interpretation of continental tectonics detailed theoretical consideration is given to the kinematics of distributed formation and the dynamics of continental deformation a j barker

long term versus short term deformation of the meizoseismal area of the 2008 achaia elia mw 6 4 earthquake in nw peloponnese greece evidence from historical triangulation and morphotectonic data abstract the deformation of the meizoseismal area of the 2008 achaia elia mw 6 4 earthquake in nw peloponnese of the first significant strike slip earthquake in continental greece was examined in two time scales of 102 years based on the analysis of high accuracy historical triangulation data describing shear and of 105 106 years based on the analysis of the hydrographic network of the area for signs of streams offset by faulting our study revealed pre seismic accumulation of shear strain of the order of 0 2 rad year in the study area consistent with recent gps evidence but no signs of significant strike slip induced offsets in the hydrographic network these results confirm the hypothesis that the 2008 fault which did not reached the surface and was not associated with significant seismic ground deformation probably because of a surface flysch layer filtering high strain events was associated with an immature or a dormant recently activated fault this fault about 150 km long and discordant to the morphotectonic trends of the area seems first to contain segments which have progressively reactivated in a specific direction in the last 20 years reminiscent of the north anatolian fault and second to limit an 150 km wide recent shear zone in the internal part of the arc in a region mostly dominated by thrust faulting and strong destructive earthquakes

foreshock occurrence before large earthquakes rates of foreshock occurrence involving shallow m 6 and m 7 mainshocks and m 5 foreshocks were measured in two worldwide catalogs over 20 year intervals the overall rates observed are similar to ones measured in previous worldwide and regional studies when they are normalized for the ranges of magnitude difference they each span the observed worldwide rates were compared to a generic model of earthquake clustering based on patterns of small and moderate aftershocks in california the aftershock model was extended to the case of moderate foreshocks preceding large mainshocks overall the observed worldwide foreshock rates exceed the extended california generic model by a factor of 2 significant differences in foreshock rate were found among subsets of earthquakes defined by their focal mechanism and tectonic region with the rate before thrust events higher and the rate before strike slip events lower than the worldwide average among the thrust events a large majority composed of events located in shallow subduction zones had a high foreshock rate while a minority located in continental thrust belts had a low rate these differences may explain why previous surveys have found low foreshock rates among thrust events in california especially southern california while the worldwide observations suggests the opposite california lacking an active subduction zone in most of its territory and including a region of mountain building thrusts in the south reflects the low rate apparently typical for continental thrusts while the worldwide observations dominated by shallow subduction zone events are foreshock rich if this is so then the california generic model may significantly underestimate the conditional probability for a very large m 8 earthquake following a potential m 7 foreshock in cascadia the magnitude differences among the identified foreshock mainshock pairs in the harvard catalog are consistent with a uniform distribution over the range of observation

geodetic constraints to the kinematics of the kapareli fault reactivated during the 1981 gulf of corinth earthquakes abstract comparison of historical and of post seismic triangulation data is used to model vertical crustal movements in the vicinity of the kapareli fault or the alkynonides earthquakes north fault one of the two antithetic normal faults which reactivated during the 1981 gulf of corinth ms 6 7 earthquakes this fault is characterized by a much smaller geomorphological signature than the south or perachora fault of the same seismic sequence analysis of geodetic data on the basis of polynomial filtering and elastic dislocation modelling as well as analysis of structural and coastal change data permits us to conclude that the upper bound in the uncertainty level of most of the available elevation changes is 20 30 cm usually lower than the corresponding dislocation signal in addition the available geodetic data have a systematic pattern and are consistent with structural data for this reason they permit more precise constraints on the geometry and the role of the kapareli fault or the alkyonides earthquakes north fault its total length is estimated about 17 km about 50 longer than its surface trace about 30 40 cm subsidence of its hanging wall as well as at least 15 cm maximum uplift of its footwall is also inferred this new evidence suggests that although in the long term the kapareli fault may represent a rather secondary antithetic fault to the alkyonides earthquakes south perachora fault during the 1981 earthquakes it probably had a more important structural role

rift migration and lateral propagation evolution of normal faults and sediment routing systems of the western corinth rift greece the active corinth rift records hanging wall migration of faulting and slip rate accel eration the rift initiated at approximately 5 4 ma and older parts are well exposed in the northern peloponnese a new correlation of chrono and lithostratigraphy and structure across the onland central to westernmost rift with offshore data reveals westward rift propagation as well as north ward fault migration northward fault migration ended first in the east with the stabilization of major north dipping faults that now bound the gulf the basin then propagated to the wnw in two stages each involving the initiation of a new fault that propagated east to se to link to the sta ble fault system extension rates accelerated in distinct steps as the rift opened to the west the youngest faults in the westernmost rift are associated with high seismicity and highest geodetic extension due to rapid fault growth and linkage at depth the early synrift succession infilled substantial inherited palaeo relief antecedent rivers estab lished vigorous sediment routing systems that controlled facies distribution throughout rifting albeit with drainage reorganization during fault migration events multiple deepening events recorded in the stratigraphy can be due to lateral rift propagation the transition from rift initiation to rift climax is therefore diachronous along the rift axis

40ar 39ar age of detrital muscovite within lower ordovician sandstone in the coastal plain basement of florida implications for west african terrane linkages detrital muscovite was concentrated from a core of lower ordovician sandstone recovered from 1282 m in the sun oil company h t parker no 1 well marion county florida the concentrate records a 40ar 39ar plateau age of 504 1 2 1 ma the paleozoic sedimentary section penetrated in this well is part of an extensive subsurface lower ordovician middle devonian sedimentary succession characterized by gondwanan paleontological affinities the succession has been correlated with sequences of similar age in the bove basin of west africa which unconformably overlie metamorphic units of the bassaride and rokelide orogens in senegal and guinea muscovite within these metamorphic rocks records ca 500 510 ma postmetamorphic 40ar 39ar cooling ages and was likely a proximal source for the lower paleozoic clastic detritus represented in the pre mesozoic sedimentary sequences beneath the southeastern united states coastal plain

contrasting accreted terranes in the southern appalachian orogen basement beneath the atlantic and gulf coastal plains and west african orogens abstract a variety of lithostratigraphic units may be outlined within the pre mesozoic crystalline basement of the atlantic and gulf coastal plains these include 1 a group of metamorphic rocks of variable grade together with deformed and retrogressed granite in southwestern alabama and southeastern mississippi wiggins uplift hornblende and biotite within higher grade units record 40ar 39ar post metamorphic cooling ages of 310 300 ma 2 a suite of contrasting igneous rocks granite basalt and agglomerate and serpentinite which occurs along the brunswick altamaha magnetic anomaly in southwestern alabama and 3 an extensive apparently coherent tectonic element the suwannee terrane comprised of undeformed granite in which biotite records 40ar 39ar post magmatic cooling ages of 530 525 ma low grade felsic metavolcanic rocks a suite of high grade metamorphic lithologies st lucie metamorphic complex in which hornblende yields 40ar 39ar post metamorphic cooling ages of 515 510 ma and a succession of lower ordovician middle devonian sedimentary rocks characterized by gondwanan fauna the west african orogens mauritanides bassarides and rokelides record a locally complex polyphase tectonothermal evolution the earliest event corresponded to westward rifting of a continental fragment from the west african craton at 700 ma this led to development of a rift facies lithotectonic succession which included sedimentary units and intracontinental igneous sequences rifting was limited and a western ensialic arc began to develop by 680 ma the associated convergence culminated in an episode of folding and metamorphism at 650 ma pan african i orogenesis following widespread deposition of late paleozoic glacial and flyschoid sediments a second tectonothermal event occurred between 550 and 500 ma pan african ii orogenesis the west african orogens were marked by general tectonic quiescence throughout most of the early and middle paleozoic late paleozoic 300 ma collision of gondwana and laurentia resulted in eastward translation of previously tectonized mauritanide units over their foreland and emplacement at highest structural levels of previously imbricated nappes which include sequences with uncertain palinspastic origins the late paleozoic hercynian transport was largely intracontinental and only westernmost portions of the exposed mauritanides record an associated penetrative tectonothermal overprint characteristics of pre mesozoic basement units which comprise the suwannee terrane in the florida subsurface suggest they represent extensions of the bassaride rokelide orogen there is no apparent record of paleozoic tectonothermal activity in the suwannee terrane this contrasts markedly with penetrative late paleozoic reworking of basement units in the wiggins uplift this suggests that a major dextral transcurrent fault was active during the late paleozoic and that proximal basement units were directly involved in collisional aspects of pangea assembly the various basement units of the coastal plain are not correlative with any of the non laurentian terranes exposed in the southern appalachian orogen e g carolina terrane of the eastern piedmont which accreted in the ordovician devonian to exterior positions along the eastern margin of the north american craton these exotic appalachian terranes were transported into their present structural positions during late paleozoic collision of gondwana and laurentia they are separated from gondwanan elements of the suwannee terrane by a suture approximately marked by the brunswick altamaha magnetic anomaly

the tertiary geodynamical evolution of the aegean arc a paleomagnetic reconstruction abstract the paleomagnetic results obtained in the last 5 6 years from tertiary formations in the aegean domain indicate that the lower miocene arc was almost rectilinear with an e w trend and that its curvature has been acquired tectonically in two major phases during the middle miocene a first phase of deformation is characterized by rotations occurring at the two terminations of the arc clockwise in the west epirus anticlockwise in the east southeastern anatolia a second phase of rotation occurring in the last 5 ma about a pole situated in the southern adriatic sea has affected only the northwestern part the data also indicate that the antalya basin has not been involved in the geodynamical evolution of the arc so that the bey daglari represent its easternmost unit a more complex rotational pattern is observed in the internal zones the large rotations measured in evia 48 and skyros 26 probably occurred in the last 5 ma and result from rotation of fault bounded blocks in a shear zone connecting the north aegean trough to the external arc in the izmir region in the karaburun peninsula of western anatolia and in the island of lesbos significant counterclockwise clockwise or null rotations of coherent blocks have taken place during the neotectonic extensional regime furthermore the values of the inclination obtained from both sedimentary and volcanic oligo miocene formations are systematically shallower than expected on the basis of a geocentered dipole field this suggests that the entire studied area has undergone a northward drift of over 1000 km since the middle miocene

changes in static stress on southern california faults after the 1992 landers earthquake the magnitude 7 5 landers earthquake of 28 june 1992 was the largest earthquake to strike california in 40 years the slip that occurs in such an earthquake would be expected to induce large changes in the static stress on neighbouring faults these changes in stress should in turn affect the likelihood of future earthquakes stress changes that load faults towards failure have been cited as the cause of small1 5 moderate6 and large7 earthquakes conversely those that relax neighbouring faults have been related to a decrease in seismicity5 here we use an elastic half space model8 to estimate the stress changes produced by the landers earthquake on selected southern california faults including the san andreas we find that the estimated stress changes are consistent with the triggering of four out of the five aftershocks with magnitude greater than 4 5 and that the largest changes 1 10 bar occurring on part of the san bernardino segment of the san andreas fault may have decreased the time to the next magnitude 8 earthquake by about 14 years

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

aegean tectonics strain localisation slab tearing and trench retreat abstract we review the geodynamic evolution of the aegean anatolia region and discuss strain localisation there over geological times from late eocene to present crustal deformation in the aegean backarc has localised progressively during slab retreat extension started with the formation of the rhodope metamorphic core complex eocene and migrated to the cyclades and the northern menderes massif oligocene and miocene accommodated by crustal scale detachments and a first series of core complexes mccs extension then localised in western turkey the corinth rift and the external hellenic arc after messinian times while the north anatolian fault penetrated the aegean sea through time the direction and style of extension have not changed significantly except in terms of localisation the contributions of progressive slab retreat and tearing basal drag extrusion tectonics and tectonic inheritance are discussed and we favour a model 1 where slab retreat is the main driving engine 2 successive slab tearing episodes are the main causes of this stepwise strain localisation and 3 the inherited heterogeneity of the crust is a major factor for localising detachments the continental crust has an inherited strong heterogeneity and crustal scale contacts such as major thrust planes act as weak zones or as zones of contrast of resistance and viscosity that can localise later deformation the dynamics of slabs at depth and the asthenospheric flow due to slab retreat also have influence strain localisation in the upper plate successive slab ruptures from the middle miocene to the late miocene have isolated a narrow strip of lithosphere still attached to the african lithosphere below crete the formation of the north anatolian fault is partly a consequence of this evolution the extrusion of anatolia and the aegean extension are partly driven from below asthenospheric flow and from above extrusion of a lid of rigid crust

lithospheric sources of north florida usa tholeiites and implications for the origin of the suwannee terrane abstract sr nd and pb isotopic data for mesozoic tholeiites from six drillholes in northern florida suwannee terrane indicate derivation of the magmas from a source that was slightly incompatible element enriched with respect to bulk earth probably continental lithospheric mantle variably contaminated by more enriched crust initial isotopic compositions of the florida tholeiites show a considerable range 87 sr 86 sr 0 7059 to 0 7097 end 4 6 to 0 1 206 pb 204 pb 18 30 to 18 65 207 pb 204 pb 15 57 to 15 66 and 208 pb 204 pb 38 22 to 38 35 these compositions are distinctly different from those of mesozoic alkali basalts from the subsurface of southwestern florida heatherington a l mueller p a 1991 geochemical evidence for triassic rifting in southwestern florida tectonophysics 188 291 302 it is suggested that the north florida tholeiites were derived from within the continental lithosphere in contrast with mesozoic volcanic rocks from southwestern florida which have been previously suggested to be related to a mantle plume sm nd isotope systematics suggest derivation of the tholeiites from a 1 ga source a similar age to that proposed by pegram pegram w j 1990 development of continental lithospheric mantle as reflected in the chemistry of the mesozoic appalachian tholeiites usa earth and planetary science letters 97 316 331 for the source of tholeiitic basalts within the carolina terrane this supports proterozoic tectonic models which suggest that both the suwannee and carolina terranes had affinities with south american portions of gondwana containing 1 ga crust specifically the sunsas rondonian province nance murphy 1996 mueller p a kozuch m heatherington a l wooden j l offield t w koeppen r p klein t l nutman a p 1996 evidence for mesoproterozoic basement in the carolina terrane and speculations on its origin in nance r d thompson m d eds avalonian and related peri gondwanan terranes of the circum north atlantic gsa special paper 304 pp 207 218

influence of static stress changes on earthquake locations in southern california earthquakes induce changes in static stress on neighbouring faults that may delay hasten or even trigger subsequent earthquakes1 10 the length of time over which such effects persist has a bearing on the potential contribution of stress analyses to earthquake hazard assessment but is presently unknown here we use an elastic half space model11 to estimate the static stress changes generated by damaging magnitude m 5 earthquakes in southern california over the past 26 years and to investigate the influence of these changes on subsequent earthquake activity we find that in the 1 5 year period following a m 5 earthquake any subsequent nearby m 5 earthquake almost always ruptures a fault that is loaded towards failure by the first earthquake after this period damaging earthquakes are equally likely to rupture loaded and relaxed faults our results suggest that there is a short period of time following a damaging earthquake in southern california in which simple coulomb failure stress models could be used to identify regions of increased seismic hazard

stratigraphic and palaeoenvironmental summary of the south east georgia embayment a correlation of exploratory wells a continental offshore stratigraphic test cost well and six exploratory wells have been drilled in the south east georgia embayment the oldest rocks penetrated are weakly metamorphosed lower ordovician quartz arenites and silurian shales and argillites in the transco 1005 1 well and upper devonian argillites in the cost ge 1 well these marine strata which are equivalent to the tippecanoe sequence in florida underlie the post rift unconformity and represent part of a disjunct fragment of gondwana that was sutured to the north american craton during the late palaeozoic alleghanian orogeny the palaeozoic strata are unconformably overlain by interbedded non marine jurassic bajocian and younger sandstones and shales and marginal marine lower cretaceous sandstones calcareous shales and carbonates which contain scattered beds of coal and evaporite together these rocks are stratigraphically equivalent to the onshore fort pierce and cotton valley formations and rocks of the lower cretaceous comanchean provincial series the abundance of carbonates and evaporites in this interval which reflects marine influences within the embayment increases upwards eastwards and southwards the upper cretaceous part of the section is composed mainly of neritic calcareous shales and shaley limestones stratigraphically equivalent to the primarily marginal marine facies of the onshore atkinson cape fear and middendorf formations and black creek group and to limestones and shales of the lawson limestone and peedee formations cenozoic strata are primarily semiconsolidated marine carbonates palaeocene to middle eocene strata are commonly cherty middle miocene to pliocene strata are massive and locally phosphatic and glauconitic quaternary sediments are dominated by unconsolidated carbonate sands the effects of eustatic changes and shifts in the palaeocirculation are recorded in the upper cretaceous and tertiary strata

first paleomagnetic results from neocene formations in evia skyros and the volos region and the deformation of central aegea paleomagnetic results from neogene volcanic and sedimentary formations in central aegea indicate that evia and skyros have undergone a 48 and 26 clockwise rotation respectively the volos region does not show any significant rotation in the last 3 ma the rotation of evia is about twice as large as the one measured from coeval formations in the external hellenic arc the results are interpreted in terms of a published model of distributed deformation by faulting which also provides an explanation for the significant differential rotation of evia and skyros

geodetic measurement of tectonic deformation in the southern alps and provence france 1947 1994 abstract active deformation at the boundary between the eurasia and africa plates varies in style the belt between the alpine mountain range and the mediterranean sea for example differs markedly in its western and eastern parts in the western part around southeast france the mountains are higher but the seismicity lower than in the eastern part around northern italy and greece yet the inter plate convergence rate of 6 mm yr varies by less than 15 between these two areas to better understand the behaviour of this complex plate boundary we use geodesy to map the spatial distribution of the deformation in this paper we focus on southeast france a tectonic crossroads between three different domains alps ligurian sea and massif central which exhibits a moderate level of seismicity here the geodetic measurements imply low rates of horizontal deformation by combining historical triangulation measurements mostly from 1947 to 1983 with global positioning system gps surveys in 1993 and 1994 we estimate the rate of angular shear in triangular subnetworks covering the study area the estimated strain rates in thirteen of nineteen triangles are smaller than their 1 standard deviation uncertainties of about 0 1 microradian yr this value bounds the rate of deformation for a 100 km wide zone in provence between marseilles to the south and the ventoux massif to the north the geodetic estimates place an upper bound of 1 to 2 mm yr on the slip rates of two seismically active structures the durance fault and the nimes fault assuming a fault zone 20 km wide in each case we also find strain rates as high as 0 20 0 07 microradian yr in three subnetworks near the epicentre of the magnitude 5 3 haute ubaye earthquake in 1959 in a region which includes the higher summits this may be interpreted either as pure shear with compression oriented ne sw across this region or right lateral simple shear along nnw sse trending faults given that this earthquake is the only one of its magnitude recorded in the study area during the time interval spanned by the geodetic measurements we infer that most of the geodetically observed deformation occurs aseismically on the whole the geodetic results suggest that the rate of north south shortening across the 100 km wide study area is not more than 1 or 2 mm yr in agreement with kinematic models based on other types of geophysical data since this deformation represents only a small part of the convergence rate of 6 mm yr predicted by the nuvel 1 model for the entire boundary between the african and eurasian plates the remaining deformation must be accommodated elsewhere this study illustrates how a careful analysis of historical geodetic data can measure the rate of tectonic deformation even where it is low and thus meaningfully bound geophysical models

the methana volcano geothermal resource greece and its relationship to regional tectonics abstract geophysical methods of analysis were applied in order to investigate the deep structure and the geothermal potential of the methana volcano ne peloponnesus greece the study is based on a re evaluation and reinterpretation of legacy magnetotelluric mt data with modern analysis methods as well as 3 d inversion of aeromagnetic data constrained by in situ measurements of magnetic susceptibility magmatic systems are located in regions of active tectonic processes that often play a controlling role the mt method is effective in delineating low resistivity functional elements of volcanic systems such as magma chambers vents thermal fluid reservoirs and thermal fluid circulation conduits the latter two of which are typically associated with active faults the aeromagnetic data can assist in mapping the configuration hence emplacement modes of volcanic rocks at depth accordingly the joint interpretation of these lines of evidence together with structural and geochemical information is expected to allow insight into the influence of contemporary tectonics on the inception and evolution of the volcano the contemporary stress field is mainly extensional nne ssw oriented and overall homogeneous in the area of methana it allows for the formation of wnw ese north easterly dipping normal faults w e faults consistent with the synthetic dextral r shear direction of riedel s shear theory and nw se faults consistent with the antithetic sinistral r shear direction all such features have been mapped on methana peninsula the magnetotelluric data imaged a significant geothermal reservoir developing around an intersection of the three active fault zones normal r and r at depths of 1 1 5 km below the centre of the peninsula as well as elongate epiphenomenal conductivity anomalies associated with the circulation of thermal fluids along all three fault zones the 3 d magnetic susceptibility model strongly suggests that the intrusion and emplacement of magmas were guided by the same active fault zones with particular reference to the r and r shears whose influence is imprinted on the configuration of volcanic rocks at depth the joint interpretation of all lines of evidence indicates that magmatism and volcanism at methana are almost completely controlled by tectonic activity in a manner analogous to the situation of the large santorini volcanic complex it also indicates that the reservoir is replenished through the weak permeable zone created by the intersection of the r and r shears which is very probably collocated with the main vent of intrusive magmatic activity and may connect with a shallow magma chamber at depths greater than 4 5 km the apparently common origin and similarities differences in the circulation paths of thermal fluids may amply explain both the individual characteristics and similarities differences in the chemical composition of thermal spring discharges which have been reported by hitherto geochemical investigations

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

increasing critical sensitivity of the load unload response ratio before large earthquakes with identified stress accumulation pattern the load unload response ratio lurr method is proposed for short to intermediate term earthquake prediction yin x c chen x z song z p yin c 1995 a new approach to earthquake prediction the load unload response ratio lurr theory pure appl geophys 145 701 715 this method is based on measuring the ratio between benioff strains released during the time periods of loading and unloading corresponding to the coulomb failure stress change induced by earth tides on optimally oriented faults according to the method the lurr time series usually climb to an anomalously high peak prior to occurrence of a large earthquake previous studies have indicated that the size of critical seismogenic region selected for lurr measurements has great influence on the evaluation of lurr in this study we replace the circular region usually adopted in lurr practice with an area within which the tectonic stress change would mostly affect the coulomb stress on a potential seismogenic fault of a future event the coulomb stress change before a hypothetical earthquake is calculated based on a simple back slip dislocation model of the event this new algorithm by combining the lurr method with our choice of identified area with increased coulomb stress is devised to improve the sensitivity of lurr to measure criticality of stress accumulation before a large earthquake retrospective tests of this algorithm on four large earthquakes occurred in california over the last two decades show remarkable enhancement of the lurr precursory anomalies for some strong events of lesser magnitudes occurred in the same neighborhoods and during the same time periods significant anomalies are found if circular areas are used and are not found if increased coulomb stress areas are used for lurr data selection the unique feature of this algorithm may provide stronger constraints on forecasts of the size and location of future large events

seismic hazard in the marmara sea region following the 17 august 1999 izmit earthquake on 17 august 1999 a destructive magnitude 7 4 earthquake occurred 100 km east of istanbul near the city of izmit on the north anatolian fault this 1 600 km long plate boundary 1 2 slips at an average rate of 2 3 cm yr 1 refs 3 5 and historically has been the site of many devastating earthquakes 6 7 this century alone it has ruptured over 900 km of its length 6 models of earthquake induced stress change 8 combined with active fault maps 9 had been used to forecast that the epicentral area of the 1999 izmit event was indeed a likely location for the occurrence of a large earthquake 9 10 here we show that the 1999 event itself significantly modifies the stress distribution resulting from previous fault interactions 9 10 our new stress models take into account all events in the region with magnitudes greater than 6 having occurred since 1700 ref 7 as well as secular interseismic stress change constrained by gps data 11 these models provide a consistent picture of the long term spatio temporal behaviour of the north anatolian fault and indicate that two events of magnitude equal to or greater than the izmit earthquake are likely to occur within the next decades beneath the marmara sea south of istanbul

40ar 39ar and u pb evidence for late proterozoic grenville age continental crust in north central cuba and regional tectonic implications renne p r mattinson j m hatten c w somin m onstott t c millfin g and linares e 1989 4 ar 39ar and u pb evidence for late proterozoic grenville age continental crust in north central cuba and regional tectonic implications precambrian res 42 325 341 central cuba is composed of fault bounded tectonostratigraphic terranes juxtaposed and deformed during plate collision and subsequent transform motion between the caribbean and north american plates in the late mesozoiccenozoic one of these the las villas terrane contains crystalline basement rocks thought to be pre upper jurassic on stratigraphic grounds the socorro complex occurs in the northwestern las villas terrane and consists of marbles and siliciclastic metasedimentary rocks and the rio carla granite an 4 ar 39ar plateau date of 903 5 7 1 ma for phlogopite from a marble corroborates previous k ar dates from this unit and establishes unambiguously a late proterozoic age for high grade metamorphism discordance of the 4 ar agar age spectrum can be reliably attributed to diffusive ar loss which if modeled as an episodic thermal event implies a reheating age that closely coincides with the late cretaceous paleogene collision between the caribbean and north american plates u pb zircon data indicate an intrusive age of 172 4 ma for the rio carla granite and reveal an inherited zircon component with an age of 900 ma radio isotopic data from the socorro complex display no evidence of pan african age thermal overprinting these observations combined with constraints provided by published results from nearly pangean landmasses suggest that the complex lay substantially to the southwest present day co ordinates during the early paleozoic following its genesis in the mid mesozoic the caribbean plate evidently transported fragments of an extensive grenville age belt that spanned the americas during the late proterozoic

the importance of classical geodetic observations for analyzing the geodynamic behaviour of the acores archipelago abstract despite their relative poor precision classical geodetic observations can provide valuable information about tectonic displacements because their lack of precision is balanced by the time span they cover in the case of the acores archipelago the contribution of six decades of classical observations provide a historically reliable and important source of information in the establishment of a tectonic model for that area complementary to gps data where only few years of observations are available based upon angular and invar wire measurements carried out in the thirties compared with more recent classical and gps observations the authors were able to deduce some significant displacements for the central group we conclude that the area is expanding in an approximately wsw ene direction showing a component parallel to the plate boundary between eurasia and africa which is about 1 5 greater than the component in the perpendicular direction as regards the faial and s jorge islands our results show a good agreement with the proposed geodynamic models for faial but not for s jorge for faial the results indicate an extension perpendicular to the faults in the direction wnw ese and a dextral strike slip along the same faults in the case of s jorge the lack of agreement with the proposed geodynamic models is probably due to the particular poor geometry and scale control of the inner network

evidence of bias in estimations of earthquake size magnitudes of earthquakes determined using traditional methods show systematic deviations dependent on tectonic setting from accurate estimates of earthquake size magnitudes are overestimated for most of the continental earthquakes underestimated for mid oceanic ridges and differences of varying sign are obtained for subduction zones this is important in evaluating the seismic risk or consideration of effects such as the seismic versus aseismic strain release as seismic moments determined from magnitudes can be wrong by as much as a factor of four

local and regional components of western aegean deformation extracted from 100 years of geodetic displacement measurements summary our objectives are as follows first we wish to develop a methodology to recover the long term component of deformation from any set of distributed time averaged geodetic strain measurements that were subject to seismic disturbance given a catalogue of local seismicity that occurred during the measurement period second using seismic and geodetic data sets that span approximately 100 years we apply this technique in the western aegean to assess the role of local seismicity in regional deformation the methodology is developed using a model for crustal deformation constructed from a long term smooth regional strain field combined with instantaneous local perturbations from upper crustal earthquakes approximated by static elastic dislocations by inverting geodetic displacements for the smooth field while simultaneously floating influential but uncertain earthquake source parameters an estimate of the regional component of deformation that is approximately independent of the seismicity can be made in the western aegean we find that the horizontal component of regional deformation can be described with minor inaccuracy by a quadratic relative displacement field the principal horizontal extensional axes calculated from the regionally smooth displacement field agree in orientation with the t axes of earthquakes in the region these observations indicate that the instantaneous elastic strain of the 10 km thick seismogenic layer is driven by a stress field that is smooth on the scale of the geodetic network as a whole 200 300 km

a simple explanation for the occurrence of the 1911 morgan hill earthquake in the stress shadow of the 1906 san francisco earthquake we propose a new model to overcome an apparent stress shadow paradox the stress shadow of the 1906 san francisco earthquake was so effective in inhibiting earthquake activity that no m 6 earthquakes occurred in the san francisco bay area for more than 70 years after the 1906 earthquake with one exception the 1911 morgan hill earthquake how could this earthquake occur only 5 years after the 1906 earthquake in an area where earthquake activity should have been inhibited our model is characterized by localized locked patches on the morgan hill segment of the calaveras fault surrounded by steadily creeping patches according to this model the tectonic stressing rate on the morgan hill segment is so high that the stress shadow caused by the 1906 earthquake can be dissipated within several years this simple model is consistent with both the surface deformation data and the apparent earthquake recurrence at morgan hill in contrast to two previous models which are either poorly constrained or have difficulty explaining such observations

an apparent mechanism dependence of radiated seismic energy we develop an extension to the method of boatwright and choy 1986 for determining the radiated seismic energy es that accounts for factors that bias the estimate we apply our technique to 204 events worldwide during the period 1992 1999 and find that the apparent stress is on average largest for strike slip events 0 70 mpa while for reverse and normal events it is significantly smaller 0 15 and 0 25 mpa respectively these results support the mechanism dependence of es reported by choy and boatwright 1995 although we find that once likely sources of bias are accounted for the mechanism dependence is not as strong as found previously the source of the mechanism dependence is unclear but one possibility is that it reflects a mechanism dependent difference in the stress drop this hypothesis is suggested by the scaling of slip with width in large strike slip earthquakes and makes two predictions which could be used to test it the first is that the discrepancy should disappear for the very largest dip slip earthquakes as the length of the fault greatly exceeds the downdip extent the second is that the discrepancy ought to disappear for smaller earthquakes the first can not yet be tested due to a lack of recent very large dip slip earthquakes the second is supported by the lack of mechanism dependence to es for smaller earthquakes an alternative hypothesis is that the apparent mechanism dependence could result if faults are opaque during rupture blocking seismic radiation across them brune 1996 this could cause radiated seismic energy to be trapped preferentially in the crust near the source volume for dipping faults there remains however a large discrepancy between estimates of es obtained from teleseismic versus regional data this discrepancy indicates a problem with teleseismic and or regional estimates of the seismic energy and must be resolved before a definite conclusion can be drawn

two stage erosion and deposition in a continental margin setting an 40ar 39ar laserprobe study of offshore detrital white micas in the norwegian sea detrital white micas from a restricted region of the norwegian sea have been analysed by the 40ar 39ar laserprobe examining the ages of individual white mica grains from offshore triassic jurassic and cretaceous sandstones reveals a narrow range of detrital white mica ages 369 424 ma moreover there is an inverse relationship between sediment age and detrital white mica age with the triassic sands containing a larger proportion of younger white micas and the cretaceous sands containing the oldest white micas in addition residence times of the detritus which is the age of the sediment subtracted from the age of the detrital white mica range from c 150 to c 300 ma for the triassic and cretaceous sands respectively the inverse age relationships combined with the large residence times for these stratigraphic levels can best be explained by an erosion deposition model involving at least two stages taking into account previous provenance studies in the lofoten region of the norwegian sea these new data suggest that detritus shed initially from the exhuming caledonian nappes of nw norway in late silurian early devonian times was deposited in intramontane basins that were themselves subsequently unroofed and re eroded from permo triassic times this caused the recycling of the caledonian detritus from the devono carboniferous basins and led to the inverted detrital age distribution ovserved in the triassic cretaceous sediments examined in this study while sedimentary recycling is not a surprising feature for mesozoic basins in the north and norwegian seas this study documents a previously untapped method 40ar 39ar laserprobe provenance studies by which to identify its effect and extent

the relationship between strain rates crustal thickening palaeomagnetism finite strain and fault movements within a deforming zone the deformation of continental lithosphere generally does not occur on a single fault but is distributed over a zone up to a few hundred kilometers wide if the deformation rate is constant throughout the zone and if the velocity is continuous everywhere and does not change with time the deformation gradient tensor can be obtained analytically this tensor directly determines the amount of crustal thickening and is related in a complicated manner to the finite strain tensor the declination of remnant magnetization measured within the zone can also be rotated by the deformation because palaeomagnetic measurements are generally made on rigid blocks which have not been deformed there is no simple relationship between such rotations and the finite strain expressions for all these quantities are obtained in terms of the velocity gradients which are taken to be constant the history of western north america is used to illustrate the relationship between the present deformation by strike slip and thrust motions the rotations of the remnant magnetization vectors and the shape of accreted terranes at the surface distributed deformation is taken up by motion on faults which separate the zone into blocks the displacement rate on the faults their strike and the finite rotations of the blocks are all controlled by the velocity gradients analytic expressions relating these quantities are obtained a deforming zone containing normal faults which crosses central greece takes up both strike slip and extension and illustrates the relationship between the structures within and the motion across the zone a similar but more complicated zone in northeastern iran involves both strike slip and shortening

active tectonics of the alpine himalayan belt between western turkey and pakistan summary over 80 new fault plane solutions combined with satellite imagery as well as both modern and historical observations of earthquake faulting are used to investigate the active tectonics of the middle east between western turkey and pakistan the deformation of the western part of this region is dominated by the movement of continental material laterally away from the lake van region in eastern turkey this movement helps to avoid crustal thickening in the van region and allows some of the shortening between arabia and eurasia to be taken up by the thrusting of continental material over oceanic type basement in the southern caspian mediterranean makran and black sea thus central turkey bounded by the north and east anatolian strike slip faults is moving west from the van region and overrides the eastern mediterranean at two intermediate depth seismic zones one extending between antalya bay and southern cyprus and the other further west in the hellenic trench the motion of northern iran eastwards from the van region is achieved mainly by a conjugate system of strike slip faults and leads to the low angle thrusting of iran over the southern caspian sea the seismicity of the caucasus shows predominantly shortening perpendicular to the regional strike but there is also some minor elongation along the strike of the belt as the causcasus overrides the caspian and black seas the deformation of the eastern part of this region is dominated by the shortening of iran against the stable borders of turkmenistan and afghanistan the north east direction of compression seen in zagros is also seen in north east iran and the kopet dag where the shortening is taken up by a combination of strike slip and thrust faulting large structural as well as palaeomagnetic rotations are likely to have occurred in ne iran as a result of this style of deformation north south strike slip faults in southern iran allow some movement of material away from the collision zone in ne iran towards the makran subduction zone where genuinely intermediate depth seismicity is seen within this broad deforming belt large areas such as central turkey nw iran azerbaijan central iran and the southern caspian appear to be almost aseismic and therefore to behave as relatively rigid blocks surrounded by active belts 200 300 km wide the motion of these blocks can usefully be described by poles of rotation the poles presented in this paper predict motions consistent with those observed and also predict the opening of the gulf of iskenderun ne of cyprus the change within the zagros mountains from strike slip faulting in the nw to intense thrusting in the se and the relatively feeble seismicity in se iran baluchistan this description also explains why the north south structures along the iran afghanistan border do not cut the east west ranges of the makran within the active belts surrounding the relatively aseismic blocks a continuum approach is needed for a description of the deformation even though motions at the surface may be concentrated on faults the evolution of fault systems within the active zones is controlled by geometric constraints such as the requirement that simultaneously active faults do not in general intersect many of the active processes discussed in this paper particularly large scale rotations and lateral movement along the regional strike are likely to have caused substantial complexities in older mountain belts and should be accounted for in any reconstructions of them

repeated gps surveys across the ionian sea evidence of crustal deformations summary geodetic evidence of crustal deformation in the ionian area detected by gps surveys is given in this paper a network consisting of nine geodetic sites crossing the ionian sea from calabria southern italy to northwestern greece was repeatedly surveyed starting in 1991 within the framework of the tyrgeonet project the results obtained from processing data from three gps campaigns performed on the same network in 1991 1994 and recently in 1995 show significant changes in the positions of five sites the deformations in terms of displacements coordinate differences are obtained by applying a rigorous statistical approach that analyses their significance by an original iterative procedure based on the classical f fisher test although more substantial geophysical conclusions require more observations the estimated relative displacement pattern is generally coherent with the features of the main tectonic structures identified for this area the detected deformations for the greek sites confirm the activity of the kephalonia right lateral transform fault and a rightlateral motion of the mattinata fault northern apulia seems to have been detected by the italian sites moreover within the time span analysed the site of matera shows a different behaviour from the three adriatic sites tremiti m s angelo and specchia cristi since relative displacements among matera and these sites were detected this fact may indicate the weakness of the assumption reported in some papers that matera could be a representative site of the motion of the whole adriatic plate furthermore the site of specchia cristi shows the maximum relative displacement in the network with a vector magnitude of about 5 cm with a 3 cm confidence interval at the 95 per cent level therefore even if some additional gps observations are needed to achieve a clearer picture of the tectonic behaviour of the ionian sea area the detected relative displacement pattern of the italian sites agrees with a possible rotational behaviour of the apulian platform with respect to the adriatic plate as already hypothesized by finetti 1982

paleoseismicity of the 1981 corinth earthquake fault seismic contribution to extensional strain in central greece and implications for seismic hazard we present paleoseismological trenching results for the active skinos fault which ruptured the surface on the alkyonides gulf basin margin in the 1981 gulf of corinth earthquake sequence three trenches expose evidence of up to six previous events which are comparable to the 1981 deformation in terms of size and geometry vertical displacement produced by the 1981 earthquake ranged from 0 45 to 1 3 m at the bambakies fan trench sites decreasing towards the eastern fault tip east of the trenches trench 1 reveals two previous events with vertical displacements between 0 5 and 1 2 m since 390 a d trench 2 reveals five or six previous events but these are not dated trench 3 reveals four previous events since 670 a d vertical displacements associated with interpreted paleoearthquakes at the trench sites are 1 2 m the recurrence interval on the skinos fault is estimated to average 330 years however significant variation in recurrence interval is allowed by the available radiometric dates average vertical displacement rates derived from the trenches are in the range 0 7 2 5 mm yr a similar long term average vertical displacement rate of 1 2 2 3 mm yr is estimated for the lifespan of the basin bounding fault this equates to a horizontal seismic strain contribution of 2 5 mm yr from the skinos fault this local seismic strain rate overlaps within error with geodetically determined velocities across the alkyonides gulf assumed to represent uniform deep crustal strain thus seismic deformation on the basin bounding fault system may take up the major part of extension across the basin and aseismic strain is not necessitated by the data if correct this would imply that geodetically determined strain rates may be used as a proxy for potential seismic moment release in seismic hazard analyses for this region

quaternary evolution of the corinth rift and its implications for the late cenozoic evolution of the aegean summary we present geological and morphological observations at different scales to constrain rates of faulting and the distribution of deformation in the seismically active aegean region we focus first on the 130 km long corinth rift an asymmetric graben where a flight of terraces of marine origin are uplifted we show that the edges of the terraces lie in the footwall of the normal fault bounding the corinth rift and correspond to sea level highstands of laic pleistocene age using a detailed analysis of aerial and spot imagery supported by field observations we have mapped 10 terrace platforms and strandlines ranging in elevation from 10 to 400 m over distances of 2 to 20 km from the fault the elevation of the terraces inner edges was estimated at 172 sites with an error of 5m this data set contains a precise description of the uplift and flexure of 10 different palaeohorizontal lines with respect to the present sea level to date the deformation we correlate the corinth terraces with late pleistocene oxygen isotope stages of high sea level stands and with global sea level fluctuations using a thick elastic plate model consistent with our current understanding of the earthquake cycle and a boundary element technique we reproduce the geometry of the shorelines to constrain both mechanical parameters and the slip on the fault we show that the seismogenic layer behaves over the long term as if its elastic modulus were reduced by a factor of about 1000 all the terraces are fitted for fault slip increasing in proportion to terrace age and the component of regional uplift is found to be less than 0 3 mm yr 1 the best fits give a slip rate of 11 3 mm yr 1 on the main rift bounding fault over the last 350 kyr other geological and morphologic information allows us to estimate the total age of the main fault 1 ma and to examine the mechanical evolution of the corinth rift the minimum observed sediment thickness in the gulf places an extreme check on the results of the modelling and a lower bound on slip rate of 6 7 mm yr 1 40 per cent less than estimated with modelling even this slip rate is nearly 10 times higher than for comparable features in most of the aegean and elsewhere in the world at a larger scale the spacing and asymmetry of the rift systems in the aegean suggest strain localization in the upper mantle with slow extension starting 15 myr ago or earlier the more recent 1 myr rapid phase of rifting in corinth partly reactivated this earlier phase of extension the younger faulting in corinth appears to result from its present location in the inhomogeneous stress field process zone of the south westward propagating tip of the southern branch of the north anatolian fault we extend these relations to propose a mechanical model for the late cenozoic evolution of the aegean as the arabia europe collision progressed in eastern turkey it caused anatolia to move to the west and the north anatolian fault to propagate into the aegean where the early slow extension started to be modified about 5 ma ago the process of propagation dramatically increased the activity of some but not all of the earlier rifts the model we present is compatible with tectonic observations as well as with the seismicity the palaeomagnetic rotations and the displacement field now observed with gps and slr

late holocene evolution of the east eliki fault gulf of corinth central greece abstract trench stratigraphy and morphotectonic analysis was used to examine the recent evolution of the helike eliki plain and eliki fault the entire alluvial plain of the kerynites and vouraikos rivers which cross the eliki fault has subsided at rate of 1 4 mm yr resulting in the burial of the late hellenistic roman occupation horizons under 3 m of fluvial and colluvial sediments along the eastern segment of the eliki fault five trenches have been excavated and their 5000 yr old fluvial and colluvial deposits have been studied in association with the fault strand imprinted on them the kerynites river crosses at high angle the eliki fault and appears to be sensitive in tectonic movements related with the eliki fault sedimentation in the alluvial plain and the fluvial geomorphology of the kerynites river is important for understanding the fault evolution and the burial of the ancient 4th century bc helike city the kerynites river course highlights breaching deformation is the more likely to connect east and west eliki fault segments and that postseismic deformation is a significant mechanism for stress accommodation for part of the west end of the gulf of corinth

revision of the timing magnitude and distribution of neogene rotations in the western aegean region to evaluate the dimension and the timing of the clockwise rotating domain and the nature of the structures that accommodate the rotating domain in the western aegean region paleomagnetic analyses were carried out in northern western and southwestern greece the results show that the rotating domain covers an area including the external albanides western mainland greece including evia and probably at least partly the peloponnesos smaller clockwise rotations on the order of 30 408 were reported previously from the chalkidiki peninsula and the islands of skyros and limnos previously two phases of approximately 258 of rotation were suggested the last one during the plio pleistocene our analysis shows that the western aegean domain rotated approximately 408 clockwise between 15 13 and 8 ma followed by an additional 108 after 4 ma the rotating domain is accommodated in the north by deformation associated with the scutari pec fault zone and in the west by the ionian thrust and the hellenic subduction zone to the south no rocks older than 10 ma are available so no conclusive data are obtained to the east of the rotating domain extensional detachment systems of the cyclades and rhodope areas were active during the rotation phase and may explain at least part of the differences in finite amounts of rotation between nonrotation or counterclockwise rotations observed in northern and eastern greece and the large clockwise rotations in western greece d 2004 elsevier b v all rights reserved

global patterns of radiated seismic energy and apparent stress radiated energies from shallow earthquakes with magnitudes 5 8 that occurred between 1986 and 1991 are used to examine global patterns of energy release and apparent stress in contrast to traditional methods which have relied upon empirical formulas these energies are computed through direct spectral analysis of broadband seismic waveforms velocity squared spectra of body waves are integrated after they have been corrected for effects arising from depth phases frequency dependent attenuation and focal mechanism the least squares regression fit of energy es to surface wave magnitude ms for a global set of 397 earthquakes yields log es 4 4 1 5ms which implies that the gutenberg richter relationship overestimates the energies of earthquakes the least squares fit between es and seismic moment m0 is given by the relationship es 1 6 10 5 m0 which yields 0 47 mpa as the average global value of apparent stress however the regression lines of both es ms and es m0 yield poor empirical predictors for the actual energy radiated by any given earthquake the scatter of data is more than an order of magnitude about each of the regression lines on the other hand global variations between es and mo while large are not random when subsets of es m0 are plotted as a function of seismic region and faulting type the scatter in data is substantially reduced the es m0 fits for many seismic regions and tectonic environments are very distinctive and a characteristic apparent stress c can be derived the lowest apparent stresses 3 0 mpa are associated with strike slip earthquakes that occur at oceanic ridge ridge transforms and in intraplate environments seaward of island arcs intermediate values of apparent stress 1 5 a 3 0 mpa are associated with strike slip earthquakes at incipient or transitional plate boundaries in general the dominant mode of failure for a tectonic environment is associated with the faulting type that has the lowest apparent stress an energy magnitude me can complement moment magnitude mw in describing the size of an earthquake me being derived from velocity power spectra is a measure of seismic potential for damage mw being derived from the low frequency asymptote of displacement spectra is more physically related to the final static displacement of an earthquake when earthquake size is ranked by moment a list of the largest events is dominated by earthquakes with thrust mechanisms when earthquake size is ranked by energy the list of the largest events is dominated by strike slip earthquakes

late paleozoic orogenies in western africa and eastern north america the diachronous closure of theic ocean the carboniferous evolution in western morocco southeastern canada and new england was dominated by intracontinental processes the subsidence of pull apart sedimentary basins and their subsequent deformation during middle carboniferous to early permian times with the development of autochthonous structures and mainly low to medium grade metamorphism on the other hand the structural style of the late carboniferous deformation in the southern appalachians and to a substantial degree also in new england that is related to a continental collision is characterized by deep seated northwest vergent thrusts and medium to high grade metamorphism the mauritanides structures are symmetrically east vergent thrusts this pattern is explained by the diachronous closure of the theic ocean that separated the avalon and carolina microcontinental blocks from paleo gondwana the closure of the theic ocean occurred during devonian times between the northern appalachians and the northwestern edge of paleo gondwana morocco whereas it was achieved only at the end of carboniferous times between the southern appalachians and western africa mauritania senegal the late devonian to early carboniferous counterclockwise rotation of gondwana induced the opening of the pull apart basins of canada new england and morocco as well as later the oblique collision in the southern appalachians and the generalized late paleozoic dextral transcurrent faulting along the northern edge of paleo gondwana

mechanism diversity of the loma prieta aftershocks and the mechanics of mainshock aftershock interaction the diverse aftershock sequence of the 1989 loma prieta earthquake is inconsistent with conventional models of mainshock aftershock interaction because the aftershocks do not accommodate mainshock induced stress changes instead the sense of slip of the aftershocks is consistent with failure in response to a nearly uniaxial stress field in which the maximum principal stress acts almost normal to the mainshock fault plane this orientation implies that i stress drop in the mainshock was nearly complete ii mainshock induced decreases of fault strength helped were important in controlling the occurrence of after shocks and iii mainshock rupture was limited to those sections of the fault with preexisting shear stress available to drive fault slip

an inverse method for determining lithospheric strain rate variation on geological timescales abstract inverse theory is used to calculate the strain rate variation as a function of time needed to fit observed subsidence patterns within extensional sedimentary basins no a priori information concerning either the duration of rifting or the total strain is required the method is one dimensional but can be generalised for use with two and three dimensional data conventional kinematic modelling of such basins normally assumes that lithospheric stretching is instantaneous or that the strain rate during a rifting period of known duration is constant the scheme is tested on a variety of synthetic data and applied to subsidence data from the dolomites northern italy linear error analysis combined with random and systematic noise tests show that variations in strain rate are significant and well resolved in the dolomites inverse calculations produce good fits to the data yielding total strains and durations of lithospheric stretching that are consistent with geological constraints calculated strain rates are not constant but vary between 10 18 10 15 s 1 information concerning spatial and temporal strain rate variation will provide important constraints for dynamic models of lithospheric deformation

geochemical evidence for triassic rifting in southwestern florida abstract mesozoic rhyolites and basalts from three drillholes penetrating the pre cretaceous basement of southwestern florida were analyzed for their trace element and sr and nd isotopic compositions major and trace element abundances suggest the suite was erupted in an extensional environment and isotopic data indicate derivation primarily from aged enriched precambrian continental lithosphere combined to varying degrees with an asthenospheric component nd model ages show no significant difference in the age of the lithosphere from which these rocks and volcanic rocks of paleozoic age from north florida were derived arguing against major displacement across the peninsula including along proposed extensions of the jay fault and or bahamas fracture zone we suggest that the geophysically inferred boundary across the peninsula if a fault may have had a strong normal component consistent with the greater depth to basement south of the boundary in this view the southwestern florida mesozoic volcanic province sfmv may represent a part of a major triassic rift basin associated with the breakup of pangaea

geodetic determination of tectonic deformation in central greece from 1900 to 1988 the global positioning system has been used to measure the relative displacements of fifteen monuments in a hundred year old triangulation network spanning part of the aegean extensional basin these displacements reflect the tectonic deformation of the region over the past century showing more than one metre of north south extension across the network the crust in this region appears to contain a few slowly deforming blocks separated by more rapidly deforming zones

earthquake doublet in kagoshima japan rupture of asperities in a stress shadow two shallow moderate m 6 earthquakes occurred in the northwestern part of kagoshima prefecture kyushu southern japan i discuss the effect of the stress change due to the first earthquake 26 march 1997 on the occurrence of the second earthquake 13 may 1997 the rupture characteristics of the two earthquakes are inferred in two steps to form the basis of the discussion i first invert strong ground motion data to construct kinematic source models and then estimate the distribution of static stress drop from the derived dislocation distributions the rupture process of the march event is simple and well described with rupture of a single asperity patch of high stress drop on the other hand multiple asperities on conjugate faults ruptured during the may event the maximum value of static stress drop for both earthquakes is about 4 mpa and seems lower than those of other japanese intraplate earthquakes the hypocenter and the largest asperity of the may earthquake are located in a stress shadow caused by the march earthquake thus the rupture history of the may earthquake is difficult to explain with a static stress change model other mechanisms such as fluid migration and dynamic stresses were also investigated but failed to explain the triggering i propose the coupled effect of static change in shear stress and normal stress under the rate and state dependent friction law as a possible mechanism

focal mechanism dependence of static stress triggering of earthquakes abstract we perform a global statistical investigation into the problem of coulomb stress triggering of earthquakes by using the harvard cmt catalogue of shallow earthquakes from 1976 to 2001 we consider earthquake pairs i e pairs of successive earthquakes occurring near each other with similar focal mechanisms and address the problem of whether or not the change of the coulomb failure stress cfs produced by the first earthquake of the pair encourages the occurrence of the second one an interesting feature is that such a coulomb stress triggering phenomenon has an apparent focal mechanism dependence for thrust earthquakes a more evident triggering effect can be observed

worldwide doublets of large shallow earthquakes abstract we investigated all the pairs of mw 7 5 shallow earthquakes in the harvard catalog that occurred at a centroid distance of less than 100 km we showed that most of these pairs have similar focal mechanisms because these earthquakes generally should have focal regions in excess of 100 km diameter their rupture zones apparently intersect for all these pairs the time interval is significantly less than the time span needed for plate motion to accumulate the strain released by the first event these observations conflict strongly with quasi periodic recurrence models on which the seismic gap hypothesis is based power law recurrence fits these earthquake ob servations much better introduction many models used to forecast long term seismic hazard are based on the quasi periodic or seismic cycle hypothesis of large earthquake occurrence this hypothesis assumes that the probability of a large earthquake is low after signifi cant release of seismic energy and that danger increases only when tectonic plate motion accumulates strain sufficient for a new strong event several models have been formulated to apply this idea to long term earthquake prediction mccann

on relating apparent stress to the stress causing earthquake fault slip apparent stress a is defined as where is the average shear stress loading the fault plane to cause slip and is the seismic efficiency defined as ea w where ea is the energy radiated seismically and w is the total energy released by the earthquake the results of a recent study in which apparent stresses of mining induced earthquakes were compared to those measured for laboratory stick slip friction events led to the hypothesis that this hypothesis is tested here against a substantially augmented data set of earthquakes for which can be estimated mostly from in situ stress measurements for comparison with a the expanded data set which includes earthquakes artificially triggered at a depth of 9 km in the german kontinentales tiefbohrprogramm der bundesrepublik deutschland ktb borehole and natural tectonic earthquakes covers a broad range of hypocentral depths rock types pore pressures and tectonic settings nonetheless over 14 orders of magnitude in seismic moment apparent stresses exhibit distinct upper bounds defined by a maximum seismic efficiency of 0 06 consistent with the hypothesis proposed before this behavior of a and can be expressed in terms of two parameters measured for stick slip friction events in the laboratory the ratio of the static to the dynamic coefficient of friction and the fault slip overshoot typical values for these two parameters yield seismic efficiencies of 0 06 in contrast to efficiencies for laboratory events for which is always near 0 06 those for earthquakes tend to be less than this bounding value because ea for earthquakes is usually underestimated due to factors such as band limited recording thus upper bounds on appear to be controlled by just a few fundamental aspects of frictional stick slip behavior that are common to shallow earthquakes everywhere estimates of from measurements of a for suites of earthquakes using are found to be comparable in magnitude to estimates of shear stress on the basis of extrapolating in situ stress data to seismogenic depths

faulting associated with large earthquakes and the average rate of deformation in central and eastern asia we determine approximate average rates of deformation in portions of eastern and central asia for the last 80 years these rates are based on estimates of source dimensions average displacements seismic moments and orientations of faults of all large earthquakes m 7 5 and as many other major earthquakes m 7 0 as possible in asia since 1900 a major part of this study is the compilation of these data for separate parts of asia we combine seismic moment tensors to estimate the average rotational strain or deformation tensors for these regions for the last 80 years we estimate that shortening across the tien shan has occurred at 11 mm yr between 5 and 19 mm yr left lateral shear on easterly trending planes in mongolia in northwestern tibet gansu and ningxia and on the xianshuihe fault in western sichuan has been very rapid more than 10 mm yr in each region and apparently as rapid as 40 mm yr in northwestern tibet gansu and ningxia slower rates of a few to 10 mm yr appear to characterize east west extension and conjugate north south shortening of tibet the earthquake history of the himalaya is consistent with rates of underthrusting of more than 10 mm yr but is probably less than the convergence rate of india with eurasia of about 50 mm yr the overall strain field is consistent with a large part of india s penetration into eurasia being absorbed by the extrusion of material out of india s way as a result southeast china moved at about 21 mm yr east southeast with respect to eurasia in the last 80 years with an uncertainty of about a factor of 2 in this estimated rate

seismicity and associated strain of central greece between 1890 and 1988 summary we examined the seismicity of central greece between 1890 and 1988 using macroseismic and instrumental data to ask two questions 1 does the seismicity of this period reveal all the major tectonic structures that are known to be active and 2 what are the likely strains associated with the seismicity over this period many known active structures have been effectively aseismic for the last hundred years and even the inclusion of all known large events earlier than 1890 reveals no activity associated with the ne coast of evia gulf of argos or graben ne of mt parnassos it is clear that even 100 years data are inadequate for either a reasonable assessment of seismic risk or for a confident estimation of maximum magnitude however we are aware of no earthquakes in central greece during the last 200 yr that were larger than ms 7 0 it is probable that the maximum magnitude is restricted by the maximum length of fault segments which appears to be around 15 20 km the earthquakes of ms 5 8 during 1890 1988 can account for a n s displacement of around 45 70 cm with maximum and minimum estimates a factor of two greater and smaller than this across part of a 1890 1900 triangulation network in central greece that was resurveyed in 1988 the contribution of smaller events may increase this displacement by about 50 per cent this cumulative seismic displacement is similar to that estimated from the geodetic work about 100 cm but a detailed comparison of the two sets of observations will be reported elsewhere a re evaluation of all the important earthquakes of 1890 1988 in central greece is presented in the appendix which summarizes information of use to both earth scientists and engineers

foreshock occurrence rates before large earthquakes worldwide global rates of foreshock occurrence involving shallow m 6 and m 7 mainshocks and m 5 foreshocks were measured using earthquakes listed in the harvard cmt catalog for the period 1978 1996 these rates are similar to rates ones measured in previous worldwide and regional studies when they are normalized for the ranges of magnitude difference they each span the observed worldwide rates were compared to a generic model of earthquake clustering which is based on patterns of small and moderate aftershocks in california and were found to exceed the california model by a factor of approximately 2 significant differences in foreshock rate were found among subsets of earthquakes defined by their focal mechanism and tectonic region with the rate before thrust events higher and the rate before strike slip events lower than the worldwide average among the thrust events a large majority composed of events located in shallow subduction zones registered a high foreshock rate while a minority located in continental thrust belts measured a low rate these differences may explain why previous surveys have revealed low foreshock rates among thrust events in california especially southern california while the worldwide observations suggest the opposite california lacking an active subduction zone in most of its territory and including a region of mountain building thrusts in the south reflects the low rate apparently typical for continental thrusts while the worldwide observations dominated by shallow subduction zone events are foreshock rich

estimation of small surface displacements in the upper rhine graben area from a combined analysis of ps insar levelling and gnss data the intra plate deformation of the upper rhine graben urg located in central europe is investigated using geodetic measurement techniques we present a new approach to calculate a combined velocity field from insar levelling and gnss measurements as the expected tectonic movements in the urg area are small less than 1mma 1 the best possible solutions for linear velocity rates from single technique analyses are estimated in a first step second we combine the velocity rates obtained from insar line of sight velocity rates in ascending and descending image geometries levelling vertical velocity rates and gnss horizontal velocity rates using least squares adjustment lsa focusing on the northern urg area we analyse sar data on four different image stacks ers ascending ers descending envisat ascending envisat descending using the persistent scatterer ps approach the linear velocity rates in ascending and descending image geometries respectively are estimated in an lsa from joint time series analysis of ers and envisat data vertical velocity rates from levelling are obtained from a consistent adjustment of more than 40 000 measured height differences using a kinematic displacement model horizontal velocity rates in east and north direction are calculated from a time series analysis of daily coordinate estimates at 76 permanently operating gnss sites in the urg region as the locations at which the measurement data of ps insar levelling and gnss reside do not coincide spatial interpolation is needed during several steps of the rigorous processing we use ordinary kriging to interpolate from a given set of data points to the locations of interest with a special focus on the modeling and propagation of errors the final 3 d velocity field is calculated at a 200 m grid which carries values only close to the location of ps points resulting in a mean horizontal and vertical precision of 0 30 and 0 13 mm a 1 respectively the vertical component of the combined velocity field shows a significant subsidence of about 0 5 mm a 1 in the northern part of the graben coinciding with a well known quaternary basin structure horizontal displacement rates of up to 0 8 mm a 1 in southeast direction are observed outside the graben in reasonable alignment with the average direction of maximum horizontal stress within the graben the velocity directions rotate toward east in the non subsiding part while an opposite trend is observed in the subsiding part of the graben the complexities of the observed velocity field are compatible to the geomechanical situation in our investigation area which is characterized by a transition from a restraining to a releasing bend setting glacial isostatic adjustment is another potential source influencing the observed velocity field as well as anthropogenic signals due to mining oil exploration and groundwater usage that have been identified in some places

jaibaras trough an important element in the early tectonic evolution of the parnaiba interior sag basin northern brazil abstract the jaibaras trough jt is a late precambrian to early paleozoic basin that is related to the subsequent formation of the paleozoic mesozoic parnaiba intracratonic basin in northern brazil based on available geological and geophysical data we propose that the jt is a prototypical rift basin formed by brittle reactivation processes along ancient shear zones associated with the ne sw transbrasiliano lineament of the brazilian panafrican orogeny the jt evolution is partially constrained by the stratigraphic sequences outcropping at the border of the basin or drilled by exploratory boreholes the preserved sedimentary column records in a broad sense the sedimentary and tectonic controls on the early subsidence in the parnaiba basin these sequences are constituted by basal fault scarp related paraconglomerates followed laterally and vertically by fluvial lacustrine sandstones interbedded with reddish shale the jt geological evolution is also constrained by petrology of four magmatic events coreau dike swarm mucambo and meruoca plutons and mafic parapui suite related to continental rifting the late precambrian early paleozoic age of jt is perfectly compatible with continental fragmentation during the processes of lithospheric stretching that affected western gondwana at that time the contemporaneous development of a magmatic sedimentary system dated as cambrian to ordovician and confined to the rift trend raised the thermal gradient and produced a mantle softening discontinuity giving rise to a broad uplifted region this might explain the close temporal and spatial association between the transbrasiliano lineament and the early paleozoic depositional axis of the parnaiba basin an integrated interpretation of the jt and the early tectonostratigraphic behaviour of the parnaiba basin indicates that the jt might constitute a precursory stage that was slightly inverted before the initiation of sag deposition in the intracratonic basin

geodetic strain of greece in the interval 1892 1992 a first order triangulation of greece was carried out in the 1890s reoccupation using global positioning system receivers of 46 of the 93 original markers yielded estimates of the deformation of the region over the intervening interval broad regions have similar geodetic strain over the 100 year time span strain north of the gulf of korinthos is predominantly north south extension though with a significant east west component the central peloponnisos is relatively stable whereas the gulfs of the southern peloponnisos are all characterized by uniaxial east west extension the seismic expression of strain for the entire region calculated from the seismic moment tensors of earthquakes of m s 5 8 during the past 100 years accounts for only 20 50 of the geodetically determined strain at a scale of 50 100 km the fraction of the strain that is expressed seismically varies much more than this range in particular whereas seismic strain in the eastern gulf of korinthos over the past 100 years is commensurate with the geodetic strain there is rapid extension across the western gulf of korinthos 0 3 strain yr 1 with negligible seismic strain for the 100 year period prior to 1992 the egion earthquake of june 1995 in the western gulf of korinthos released only a small proportion 20 of the elastic strain that had accumulated in that region the observed distribution of displacements can be explained by the relative rotation of two plates with a broad accommodation zone between them but it is equally consistent with the deformation that would be expected of a sheet of fluid moving toward a low pressure boundary at the hellenic trench a simple calculation implies that if the region does behave as a fluid then its effective viscosity is 10 22 10 23 pa s such viscosities are consistent with the deformation of a lithosphere obeying a rheological law similar to that obtained for olivine in the laboratory

continental tectonics in the aftermath of plate tectonics the success of plate tectonics required an acceptance of continental drift and thus a reinterpretation of the large scale geological history of most of the earth but the basic tenet of plate tectonics rigid body movements of large plates of lithosphere fails to apply to continental interiors where buoyant continental crust can detach from the underlying mantle to form mountain ranges and broad zones of diffuse tectonic activity

active faulting at delphi greece seismotectonic remarks and a hypothesis for the geologic environment of a myth historical data are fundamental to the understanding of the seismic history of an area at the same time knowledge of the active tectonic processes allows us to understand how earthquakes have been perceived by past cultures delphi is one of the principal archaeological sites of greece the main oracle of apollo it was by far the most venerated oracle of the greek ancient world according to tradition the mantic proprieties of the oracle were obtained from an open chasm in the earth delphi is directly above one of the main antithetic active faults of the gulf of corinth rift which bounds mount parnassus to the south the geometry of the fault and slip parallel lineations on the main fault plane indicate normal movement with minor right lateral slip component combining tectonic data archaeological evidence historical sources and a reexamination of myths it appears that the helice earthquake of 373 b c ruptured not only the master fault of the gulf of corinth rift at helice but also the antithetic fault at delphi similarly to the corinth earthquake of 1981 moreover the presence of an active fault directly below the temples of the oldest sanctuary suggests that the mythological oracular chasm might well have been an ancient tectonic surface rupture

changes in state of stress on the southern san andreas fault resulting from the california earthquake sequence of april to june 1992 the april to june 1992 landers earthquake sequence in southern california modified the state of stress along nearby segments of the san andreas fault causing a 50 kilometer segment of the fault to move significantly closer to failure where it passes through a compressional bend near san gorgonio pass the decrease in compressive normal stress may also have reduced fluid pressures along that fault segment as pressures are reequilibrated by diffusion that fault segment should move closer to failure with time that fault segment and another to the southeast probably have not ruptured in a great earthquake in about 300 years

seismic strain rates in regions of distributed continental deformation we compare the rates and configurations of seismic deformation determined from moment tensor mechanisms of earthquakes in five continental regions with the rates and configurations expected if the seismicity reflected the relative plate motions in the regions the five regions the aegean iran california western new guinea and central asia are characterized by high levels of seismicity distributed over hundreds to thousands of kilometers from the accepted plate boundaries the earthquake mechanisms are compiled primarily from the catalog of centroid moment tensor solutions which is nearly complete over the interval 1977 1987 for earthquakes greater than ms 5 the thickness of the seismogenic layer in each region is constrained by the results of modeling broadband body wave phases and of previous earthquake studies in the aegean california and western new guinea the observed configurations of deformation agree with a simple model of distributed accommodation of relative plate motion in iran and central asia the moment tensors indicate that there is appreciable strain parallel to the strikes of the belts we augment our 10 year estimates of seismic deformation with the available historical moment and magnitude estimates for the five regions and find that moderate and large earthquakes account for between 25 and 70 of the deformation of the seismogenic layer

stress evolution and seismic hazard of the dead sea fault system abstract we calculated the stress evolution for the central part of the dead sea fault system 30 5 n 34 5 n from 551 to 2005 through modelling the static stress changes due to 14 historical earthquakes with m s 6 0 superimposed by tectonic loading from relative plate motion from the results of our numerical models we identified two segments with high positive changes in coulomb failure stress cfs exceeding 4 mpa a 90 km long segment of the jordan fault south of the sea of galilee and a 30 km long segment east of the dead sea these segments could result in m s 7 4 and m s 6 8 earthquakes respectively in contrast to similar stress evolution models of other continental transform faults our results support only partly the hypothesis that coseismically induced static stress changes control the spatial succession of earthquakes we calculated on each rupture plane the mean of cfs and the maximum cfs due to the stress changes of all preceding earthquakes the results of the calculated mean cfs values reveal that only 6 out of 13 earthquakes could have been triggered the subsequent earthquake from the analysis of the maximum cfs values we find that 8 out of 13 earthquakes could have triggered the subsequent earthquake since our model results are sensitive to location and magnitude of historical earthquakes and the tectonic loading rates of the fault segments we emphasize the need for further paleoseismological studies and current slip rate estimation from continuously observing gps arrays and geological investigations taking into account that six large cities beirut damascus haifa tel aviv amman and jerusalem are in close proximity with distances between 30 and 150 km to the jordan segment the seismic risk is probably higher than accounted before