tectonic denudation of the shuswap metamorphic terrane of southeastern british columbia large scale over thrusting and regional extension are both known to have been operative within the shuswap metamorphic terrane of the southern omineca belt the monashee core complex of the northern shuswap terrane is interpreted to be a crustal scale duplex that was developed during late mesozoic shortening and thickening of the crust uplift of the monashee complex caused by basement duplexing is estimated to have been in excess of 25 km late cretaceous overthrusting of high grade metamorphic and related plutonic rocks during later stages of uplift and basement duplexing led to weakening of the crust and to gravitationally driven extension of a regional crustal welt shuswap culmination denudation and spreading of this uplifted metamorphic terrane are attributed to displacements across listric normal shear zones and faults localized along the outward dipping flanks of the shuswap culmination total extension across the shuswap culmination at the northern end of the monashee complex is estimated to be no greater than 30 this model of denudation and gravity induced spreading is extrapolated southward into the valhalla and okanagan regions where extension may be far more significant

rapid extension in an eocene volcanic arc structure and paleogeography of an intra arc half graben in central idaho a study of extension volcanism and sedimentation in the middle eocene panther creek half graben in central idaho shows that it formed rapidly during an episode of voluminous volcanism the east southeast tilted panther creek half graben developed across the northeast edge of the largest cauldron complex of the challis volcanic field and along the northeast trending trans challis fault zone two normal fault systems bound the east side of the half graben one fault system strikes northeast parallel to the trans challis fault zone and the other strikes north to northwest the geometry of the basin fill deposits shows that movement on these two normal fault systems was synchronous and that both faults controlled the development of the panther creek half graben strikes of the synextension volcanic and sedimentary rocks are similar throughout the half graben whereas dips decrease incrementally upsection from as much as 60 to less than 10 previous k ar dates and a new 40 ar 39 ar plateau date from the youngest widespread tuff in the basin suggest that most of basin formation spanned 3 m y between about 47 7 ma and 44 5 ma as much as 6 5 km of volcanic and sedimentary rocks were deposited during that time although rates of extension and subsidence were very high intense volcanic activity continually filled the basin with ash flow tuffs outpacing subsidence and sedimentation until the end of basin development after the abrupt end of challis volcanism locally derived pebble to boulder conglomerate and massive reworked ash accumulated in the half graben these sedimentary rocks make up a small part of the basin fill in the panther creek half graben and were derived mainly from proterozoic metasedimentary rocks uplifted in the footwall of the basin the east southeast tilt of the sedimentary rocks their provenance and coarse grain size and the presence of a gravity slide block derived from tilted volcanic rocks in the hanging wall attest to continued tectonism during conglomerate deposition provenance data from the sedimentary rocks imply that the highland in the footwall of the panther creek half graben was never thickly blanketed by synextension volcanic rocks despite intense volcanic activity analysis of the panther creek half graben and other intra arc rift basins supports previous interpretations that relative rates of volcanism and subsidence control the proportion of volcanic rocks deposited in intra arc rifts

seismicity of the aegean and surrounding area abstract seismicity parameters based on instrumental and historical data are given for 36 seismic sources of shallow earthquakes and for 6 seismic sources of intermediate depth earthquakes in the aegean and surrounding area 34 n 43 n 18 e 30 e these parameters are of two categories parameters of the first category are useful for seismic hazard evaluation a and b values of the frequency magnitude relation maximum earthquake magnitude number of shocks larger than certain magnitude per year while parameters of the second category are proper for describing the spatial distribution of seismicity mean return period most probable magnitude in a certain time period moment rate shallow seismicity is highest along the convex side of the hellenic arc but close to the coast ionian islands south peloponnesus south of crete south of karpathos and rhodos in central greece patraikos corinthiakos evoikos gulfs thessalia and along a seismic belt which includes the northwestern anatolia fault zone the northernmost part of the aegean sea and the serbomacedonia zone the intermediate depth seismic activity is distributed in two parts of the benioff zone which dips from the convex side eastern mediterranean to the concave side aegean sea of the hellenic arc the one part shows a low dip angle and includes earthquakes with focal depths between 70 km and 100 km this part has a high seismicity earthquake magnitudes up to 8 0 and is situated below the inner slope of the sedimentary part of the hellenic arc eastern peloponnesus north of crete rhodos based on the fact that this part of the benioff zone is a continuation of the seismic zone of shallow earthquakes along the hellenic arc and that both zones have the same seismicity it is concluded that they constitute a continuous seismic belt on which coupling occurs between the subducted eastern mediterranean lithosphere and the overthrusted aegean lithosphere the other inner part of the benioff zone shows low seismicity maximum earthquake magnitude up to 7 1 with earthquakes of focal depths between 100 km and 180 km it dips at a mean angle of 38 below the volcanic arc of the southern aegean sea and is the result of the subduction of the front part of the eastern mediterranean lithosphere without coupling with the aegean lithosphere

potential earthquake risk estimations by application of a simulation process abstract potential earthquake risks are defined here in terms of the annual probability of exceeding a peak ground acceleration level at the free surface of a site potential earthquake risks in israel were estimated by shapira 1981 1982 by considering the apparent seismicity of the region during the last 145 years in this paper a simulation process has been applied in order to examine the reliability of previous estimations and to provide another general tool for earthquake risk evaluation a relatively simple monte carlo procedure was developed and has been used for estimating as an example the potential earthquake risk in jerusalem israel the estimated probabilities obtained by the simulation procedure are for all practical purposes similar to the apparent probabilities previously determined by the author however a re evaluation of the potential earthquake risks in israel will be required when an attenuation equation based on local and regional acceleration measurements has been developed

the role of seismicity models in probabilistic seismic hazard estimation comparison of a zoning and a smoothing approach summary seismic hazard estimations are compared using two approaches based on two different seismicity models one which models earthquake recurrence by applying the truncated gutenbergrichter law and a second one which smoothes the epicentre location of past events according to the fractal distribution of earthquakes in space woo 1996 the first method requires the definition of homogeneous source zones and the determination of maximum possible magnitudes whereas the second method requires the definition of a smoothing function our results show that the two approaches lead to similar hazard estimates in low seismicity regions in regions of increased seismic activity on the other hand the smoothing approach yields systematically lower estimates than the zoning method this epicentre smoothing approach can thus be considered as a lower bound estimator for seismic hazard and can help in decision making in moderate seismicity regions where source zone definition and estimation of maximum possible magnitudes can lead to a wide variety of estimates due to lack of knowledge the two approaches lead however to very different earthquake scenarios disaggregation studies at a representative number of sites show that if the distributions of contributions according to source site distance are comparable between the two approaches the distributions of contributions according to magnitude differ reflecting the very different seismicity models used the epicentre smoothing method leads to scenarios with predominantly intermediate magnitudes events 5 m 5 5 while the zoning method leads to scenarios with magnitudes that increase with the return period from the minimum to the maximum magnitudes considered these trends demonstrate that the seismicity model used plays a fundamental role in the determination of the controlling scenarios and ways to discriminate between the most appropriate models remains an important issue

kinematics and timing of three superposed extensional systems east central idaho evidence for an eocene tectonic transition cenozoic crustal extension in east central idaho began about 50 ma and continues at present three distinct episodes characterize one of the longest intervals of cenozoic extension yet documented in the north america cordillera crosscutting relationships between ne striking normal faults and volcanic rocks regional dike trends and slickenline data indicate nw se extension during peak eocene volcanism about 49 48 ma episode 1 ne striking normal faults with at most a few kilometers of offset formed in an intraarc setting during rapid ne subduction of oceanic plates under the pacific northwest north to nnw striking and west dipping normal faults with offsets up to 10 15 km formed during a younger middle eocene to oligocene basin forming event episode 2 this newly documented episode was the most important extensional event in east central idaho and began during the waning phases of challis volcanism wsw ene to sw ne extension during episode 2 was nearly perpendicular to the extension direction during episode 1 and perpendicular to the grain of the idaho montana fold and thrust belt the flip in extension direction between episode 1 and episode 2 is tightly constrained by 40ar 39ar age determinations to have taken place at the end of eocene challis magmatism about 46 48 ma i infer that plate boundary forces controlled the geometry of normal faults and dikes during episode 1 whereas internal stresses within previously thickened crust drove major sw to wsw directed extension during episode 2 a drop in convergence rates between the north american and farallon plates between 59 ma and 42 ma stock and molnar 1988 may coincide with the onset of gravitational spreading during episode 2 and may also explain the abrupt end of eocene magmatism in the pacific northwest miocene and younger sw dipping basin and range faults episode 3 extended the region in a ne sw direction although faults formed during episode 2 and episode 3 are not parallel slickenlines indicate only small changes in slip vector trends suggesting little rotation of the extension direction in east central idaho since 46 ma

geometric test for late cretaceous paleogene intracontinental transform faulting in the canadian cordillera the tintina trench northern rocky mountain trench tt nrmt fault zone and the fraser river straight creek fr sc fault zone are separate en echelon concentric small circle fault segments of a composite intracontinental transform fault zone more than 2500 km long that cuts diagonally across the canadian cordillera from the outboard part of a tectonic collage of accreted foreign terranes in the south into the north american preaccretionary continental margin in the north most of the 450 km of right hand slip on the tt nrmt fault zone was transformed southward during the late cretaceous and paleocene into oblique convergence in the southern canadian rockies the remainder probably comprising less than 100 km was transformed southwestward during early and middle eocene time via a zone of distributed shear and east west crustal stretching into right hand slip on the en echelon fr sc fault zone these interpretations based on regional systematic mapping of geologic structures are in conflict with interpretations of paleomagnetic measurements that call for more than 1000 km of post mid cretaceous right hand displacement along the general locus of the tt nrmt fault zone involving foreign terranes and the parts of north america to which they had been accreted this paradox must be resolved

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

the surface rupture and slip distribution of the 17 august 1999 izmit earthquake m 7 4 north anatolian fault the 17 august 1999 izmit earthquake occurred on the northern strand of the north anatolian fault zone the earthquake is associated with a 145 km long surface rupture that extends from southwest of duzce in the east to west of hersek delta in the west detailed mapping of the surface rupture shows that it consists of five segments separated by releasing step overs herein named the hersek karamursel golcuk izmit sapanca lake sapanca akyazi and karadere segments from west to east respectively the hersek segment which cuts the tip of a large delta plain in the western end of the rupture zone has an orientation of n80 the n70 80 e trending karamursel golcuk segment extends along the linear southern coasts of the izmit gulf between karamursel and golcuk and produced the 470 cm maximum displacement in golcuk the northwest southeast striking golcuk normal fault between the karamursel golcuk and izmit sapanca segments has 2 3 m maximum vertical displacement the maximum dextral offset along the izmit sapanca lake segment was measured to be about 3 5 m and its trend varies between n80 e and east west the sapanca akyazi segment trends n75 85 w and expresses a maximum displacement of 5 2 m the karadere segment trends n65 e and produced up to 1 5 m maximum displacement the karadere and sapanca akyazi segments form fan shape or splaying ruptures near their eastern ends where the displacement also diminished

extensional deformation with northwest vergence pioneer core complex central idaho the pioneer mountains of idaho contain a detachment fault that separates a lower plate core of precambrian and ordovician metasedimentary rocks and cretaceous and eocene plutonic bodies from a surrounding upper plate of paleozoic sedimentary and tertiary sedimentary and volcanic units the detachment system developed during tertiary extension and it overprinted paleozoic and mesozoic east directed compressional features beneath the detachment both brittle and ductile mylonitic deformation can be observed trends of stretching lineations in the mylonite and striations along the detachment surface both cluster around n65 w composite planar fabrics s and c surfaces in the mylonite and development of the mylonite zone on the northwest side of the core both suggest a top to the west sense of shear both brittle and ductile deformation affect the eocene pluton of the core therefore the deformation must be eocene or younger displacement is estimated at about 17 km the extension direction in the pioneer complex correlates with that of other core complexes in the region north and south of the snake river plain this suggests that the direction of extension in core complexes was controlled by an inherited structural framework which was crustal in scale

the seismic parameter b of the frequency magnitude relation and its association with the geological zones in the area of greece abstract the parameter b of the frequency magnitude relation has been accurately calculated for each of the 21 seismic zones into which the aegean and surrounding area 34 n 43 n 18 e 30 e has been divided on the basis of several seismotectonic criteria these 21 seismic zones have been geographically separated into three a b c groups regions according to the values of the parameter b the outer region a is characterized by a relatively high value 1 03 the middle region b by an intermediate value 0 84 and the innermost region c by a low value 0 60 the boundaries of these three groups of zones almost coincide with the boundaries of well known geological zones this observation is interpreted in terms of mechanical heterogeneity of the material and of structural and stress conditions in the area

rupture zones in the aegean region rupture zones of strong shallow earthquakes can be investigated by field observations of surface fault traces sf accurate location of spatial clusters of aftershocks or other small earthquakes cl reliable fault plane solutions fp and information on the spatial distribution of sites with high i viii macroseismic intensities ma the validity of these four techniques was successfully tested by comparing the results of their application to several cases of strong shallow earthquakes these techniques were then applied to spatially define the rupture zones of 150 strong m 6 0 shallow earthquakes in the aegean and surrounding area the type of faulting was determined for all these zones by the use of reliable fault plane solutions which are available for this area the orientation of most of these rupture fault zones is in good agreement with the presently acting stress field with some exceptions which are attributed to the rupture of pre existing faults the tectonic implications of these zones are discussed 1999 elsevier science b v all rights reserved

small scale spatial variation of the stress field in the back arc aegean area results from the seismotectonic study of the broader area of mygdonia basin n greece abstract in the present work a detailed seismotectonic study of the broader area of the mygdonia basin n greece is performed digital data for earthquakes which occurred in the broader mygdonia basin and were recorded by the permanent telemetric network of the geophysical laboratory of the aristotle university of thessaloniki during the period 1989 1999 were collected and fault plane solutions for 50 earthquakes which occurred in the study area were calculated with a modified first motions approach which incorporates amplitude and radiation pattern information fault plane solutions for the 3 main shocks of volvi 23 05 78 m w 5 8 and 20 06 78 m w 6 5 and arnaia 04 05 95 m w 5 8 events and the 1978 aftershock sequence were additionally used moreover data from two local networks established in the mygdonia basin were also incorporated in the final dataset determination of the stress field was realized by the use of the method of gephart and forsyth gephart j w forsyth d w 1984 an improved method for determining the regional stress tensor using earthquake focal mechanism data application to the san fernando earthquake sequence jour geophys res v 89 no b11 p 9305 9320 for the stress tensor inversion and the results were compared with independent estimates based on the calculation of the average moment tensor papazachos c b kiratzi a a 1992 a formulation for reliable estimation of active crustal deformation and its application to central greece geophys j int 111 424 432 the obtained stress results show a relatively good agreement between the two approaches with differences in the azimuth of the dominant extension axis of the order of 10 furthermore comparison with independent information for the mean stress axes provided by the study of kinematics on neotectonic faults mountrakis d kilias a tranos m thomaidou e papazachos c karakaisis g scordilis e chatzidimitriou p papadimitriou e vargemezis g aidona e karagianni e vamvakaris d skarlatoudis a 2003 determination of the settings and the seismotectonic behavior of the main seismic active faults of northern greece area using neotectonic and seismological data earthquake planning and protection organisation oasp in greek shows a similar agreement with typical misfit of the order 10 the stress inversion method was modified in order to select one or both nodal planes of the focal mechanism which corresponds to the true fault plane of the occurred earthquakes and was able to select a single fault plane in the majority of examined cases using this approach the obtained fault plane rose diagrams are in agreement with results from various neotectonic studies moreover several secondary active fault branches were identified which are still not clearly observed in the field

the skyros earthquake mw 6 5 of 26 july 2001 and precursory seismicity patterns in the north aegean sea the rupture zone of the m w 6 5 earthquake of 26 july 2001 in the north aegean sea nas is oriented northwest southeast and occupies the southwestern part of the seismic zone of nas the motion indicates reverse faulting with a significant sinistral strike slip component a review of the past nas seismicity reveals that in the last 150 yr the seismicity is strongly clustered in time with 14 out of 15 pre 2001 events being members of a cluster only the 1912 earthquake is an isolated event this implies that the probability of the 2001 earthquake being the first member of a new time cluster is 0 93 which is the probability for the next nas strong earthquake to occur within a time interval equal to the mean interarrival time of cluster events 2 9 2 06 yr the distribution of the earthquake rupture zones and the position of the 2001 event suggest that the next event may rupture one of the unruptured parts of nas to the northeast of the 2001 earthquake

tectonic evolution of the priest river complex northern idaho and washington a reappraisal of the newport fault with new insights on metamorphic core complex formation new geologic mapping 40ar 39ar thermochronometry and geobarometry in the middle eocene priest river metamorphic core complex provide the basis for unraveling the role of en echelon fault systems in core complex formation and for determining the scale of crustal fragments that form during continental extension four faults occur in the priest river complex the east verging purcell trench fault zone on the eastern side consists of two distinct en echelon fault segments separated by an unfaulted homocline the u shaped newport fault system on the northwestern side is a conjugate normal fault set the west verging eastern newport fault terminates within the silver point wrencoe pluton which was intruded syntectonically into the fault zone the east verging western newport fault merges with the east verging spokane dome mylonite zone in the underlying infrastructure new geobarometric data show that this midcrustal shear zone which evidently forms part of the regional basal decollement of the cordilleran fold and thrust belt also records significant eocene extensional shearing rocks that formed beneath the mylonite zone at a depth of 30 35 km are juxtaposed against rocks that formed at a depth of 10 km above the zone eocene 40ar 39ar chrontours in the southern part of the infrastructure record progressive exhumation and quenching that becomes younger eastward in the northern fragment of the infrastructure alternating domains of progressive westward exhumation quenching and progressive eastward exhumation quenching occur beneath the eastern newport fault and the northern purcell trench fault respectively these relationships form the basis for a new model of the evolution of the priest river complex the southern part of the infrastructure was exhumed by a major east verging detachment system comprising the western newport fault and the reactivated eastern part of the spokane dome mylonite zone into which the western newport fault merges this master detachment fault which roots in the southern purcell trench on the east side of the core complex plunges beneath the northern part of the infrastructure the selkirk crest block below the detachment the infrastructure appears to be intact above the detachment the crust extended along a set of relaying conjugate detachment faults these faults are the eastern newport fault and the north and south purcell trench faults kinematic analysis shows that the selkirk crest block is a crustal scale extensional horse that was stranded as continued extension moved the underlying metamorphic infrastructure out from beneath it and toward the west along the master detachment this study shows that large tracts of midcrustal rocks can be translated and stranded as allochthonous fragments during continental crustal extension

a catalogue of seismicity in greece and the adjacent areas for the twentieth century a magnitude homogeneous earthquake catalogue spanning the twentieth century has been assembled for greece and adjacent areas data assemblage had to consider all of the common magnitude scales mw ms mb and ml including ml ath of the national observatory of athens noa fourteen different correlation equations between magnitude scales were considered in order to approach magnitude homogeneity in the final catalogue this catalogue contains an estimate of both mw and ms for each earthquake and the actual reported values of mb ms mw and ml the final catalogue includes 5198 earthquakes after having been truncated at 4 mw to eliminate large numbers of patchily reported microearthquakes these 5198 earthquakes during 1900 1999 are within the area 33 438n 18 30 998e focal depths 1 0 215 km and magnitude range 4 0vmwv7 7 the surface wave magnitude ms is always estimated for each earthquake to facilitate application of the catalogue to seismic hazard assessment since seismic attenuation laws are more often expressed in terms of ms rather than mw alongside this new catalogue the data of papazachos and papazachou for the period 550 bc 1899 then provide a full picture of the known seismicity of greece d 2004 elsevier b v all rights reserved

triggered slip observations of the 17 august 1999 izmit turkey earthquake using radar interferometry we use synthetic aperture radar interferometry insar to map the displacement field of the 17 august 1999 izmit earthquake which largely conforms to that predicted for an elastic upper crust we determine the earthquake source parameters and show that slip continues farther west than the mapped fault ruptures we also show that additional sub surface displacements occurred on parallel strands of the north anatolian fault zone we argue that this was caused by changes in static stress accompanying the mainshock or by the dynamic release of regional stresses

thessaloniki gerakarou fault zone tgfz the western extension of the 1978 thessaloniki earthquake fault northern greece and seismic hazard assessment abstract active faulting and seismic properties are re investigated in the eastern precinct of the city of thessaloniki northern greece which was seriously affected by two large earthquakes during the 20th century and severe damage was done by the 1759 event it is suggested that the earthquake fault associated with the occurrence of the latest destructive 1978 thessaloniki earthquake continues westwards to the 20 km long thessaloniki gerakarou fault zone tgfz which extends from the gerakarou village to the city of thessaloniki this fault zone exhibits a constant dip to the n and is characterised by a complicated geometry comprised of inherited 100 trending faults that form multi level branching tree like fault geometry along with nne to ne trending faults the tgfz is compatible with the contemporary regional n s extensional stress field that tends to modify the pre existing nw se tectonic fabric prevailing in the mountainous region of thessaloniki both the 1978 earthquake fault and tgfz belong to a ca 65 km long e w trending rupture fault system that runs through the southern part of the mygdonia graben from the strymonikos gulf to thessaloniki this fault system here called thessaloniki rentina fault system trfs consists of two 17 20 km long left stepping 100 trending main fault strands that form underlapping steps bridged by 8 10 km long ene wsw faults the occurrence of large m 6 0 historical earthquakes in 620 677 and 700 a d demonstrates repeated activation and therefore the possible reactivation of the westernmost segment the tgfz could be a major threat to the city of thessaloniki changes in the coulomb failure function cff due to the occurrence of the 1978 earthquake calculated out in this paper indicate that the tgfz has been brought closer to failure a convincing argument for future seismic hazard along the tgfz

kernel estimation methods for seismic hazard area source modeling in probabilistic seismic hazard analysis the representation of seismic sources by area zones is a standard means of data reduction however where the association between seismicity and geology is complex as it is in many tectonic regimes the construction of zone geometry may become contentiously subjective and ambiguities may end up being resolved through appeal to the nonscientific rule of conservatism or pragmatism although consideration of alternative zonations within a logic tree framework provides a channel for some of the uncertainty it does not address the fundamental validity of the zonation procedure itself in particular neither the minimal assumption of uniform seismicity within a zone nor the euclidean geometry of a zone accord with the fractal spatial distribution of seismicity and the magnitude insensitivity of zonation ignores the spatial extent and correlations of different sized earthquakes an alternative procedure for area source modeling avoids euclidean zones and is based statistically on kernel estimation of the activity rate density inferred from the regional earthquake catalog the form of kernel is governed by the concepts of fractal geometry and self organized criticality with the bandwidth scaling according to magnitude in contrast with zonal models for intraplate regions the kernel estimation methodology makes provision for moderate earthquakes to cluster spatially while larger events may migrate over sizeable distances

driving mechanisms for 40 km of exhumation during contraction and extension in a continental arc cascades core washington 1 in the nw north american cordillera the cascades core region of the coast plutonic complex underwent late cretaceous 96 ma to locally 73 ma sw ne contraction and crustal thickening followed by dextral transpression 73 to 55 ma then transtension 3 mm yr by local thrusting in regions undergoing crustal thickening in the central part of the core chelan block 40 km of exhumation occurred between 91 and 45 ma about half of which occurred during early contraction driven by thrusting and half during top to north arc oblique shear during reactivation of a midcrustal cretaceous thrust the dinkelman decollement the footwall of this thrust consists of the swakane biotite gneiss a cretaceous metaclastic assemblage with recorded pressures of 10 12 kbar no arc related magmatism and structures dominated by pervasive top to north shearing the hanging wall consists of the napeequa complex an oceanic assemblage with recorded pressures of 6 12 kbar voluminous arc related magmatism and complex structures indicating early top to wsw shearing younger top to north shearing and widespread folding in the napeequa top to north shearing started by 73 ma during melt present conditions at pressures 6 kbar top to north shearing in both hanging wall and footwall continued during exhumation 1 6 mm yr and cooling to greenschist facies conditions during which slip became increasingly localized eventually resulting in formation of pseudotachylite on discrete slip surfaces we suggest that arc oblique extension was driven by along arc heterogeneity in displacements erosion initially during transpression and underplating of continental sediments and later during transtension

petrological and geochronological constraints on regional metamorphism along the northern border of the bitterroot batholith quantitative thermobarometry in pelites and garnet amphibolites from the bitterroot metamorphic core complex combined with u pb dating of metamorphic monazite and zircon from footwall rocks provide new constraints on the p t t evolution of footwall rocks the thermobarometric and geochronological results when correlated with observations from other regions bordering the bitterroot batholith define a regional metamorphic history for the northern margin of the bitterroot batholith consisting of three distinct events beginning with early prograde metamorphism m1 coincident with arc related magmatism and crustal shortening at c 100 80 ma magmatism and crustal thickening led to regional upper amphibolite facies metamorphism m2 and anatectic melting between 64 and 56 ma mineral textures related to high temperature isothermal decompression m3 coincident with late stages of magmatism in the bitterroot complex footwall 56 48 ma are only preserved in areas adjacent to extensional structures the close temporal relationship between peak metamorphism and the onset of footwall decompression indicates that thermal weakening was an important factor in the initiation of early eocene regional extension and tectonic denudation of the bitterroot complex and possibly the boehls butte metamorphic terrane the morphology of the decompressional p t t path derived for bitterroot footwall rocks is similar to other trajectories reported for cordilleran core complexes and may represent a transition in the deformational style of core bunding detachments responsible for exhumation

strain partitioning in an obliquely convergent orogen plutonism and synorogenic collapse coast mountains batholith british columbia canada 1 we describe the crustal structure of the coast mountains batholith between 54 and 55 n within the canadian cordillera with emphasis on emplacement of the 7 km thick kasiks sill complex ksc kinematic patterns that developed during emplacement of the ksc are the result of interactions between magma transport magma accumulation and regional deformation the sills were emplaced during nw directed normal shearing and flattening of country rocks that host the ksc a 2 km thick shallowly ne dipping mylonite zone cuts the eastern side of the ksc kinematic indicators within the mylonite zone record top to the east normal displacements structural analysis shows that mylonite formation occurred during subvertical shortening and east northeast subhorizontal extension u pb zircon age dates show that ene directed normal shearing along the eastern side of the ksc and wnw directed normal shearing within the ksc occurred contemporaneously between 54 and 51 ma indicating strong strain partitioning between the mylonite and the ksc this pattern of strain partitioning is interpreted to have been driven by return flow of melt laden crust in response to tectonic denudation of the upper crust seismic profiling shows that many of these structures extend to mid and lower crustal depths comparison of our results with other regions within the canadian cordillera indicates that orogen scale right lateral strike slip faults deformed synchronously with wide spread magmatism and formation of extensional gneiss domes thus the crustal structure of the coast mountains batholith was the result of early tertiary batholith construction during dextral oblique convergence and synorogenic collapse

timing of extension in the pioneer metamorphic core complex with implications for the spatial temporal pattern of cenozoic extension and exhumation in the northern u s cordillera 1 the pioneer core complex pcc in central idaho lies along a transition between early eocene and ca 40 ma core complexes to the north and south respectively thus the age of extensional development of the pcc is important in understanding the spatial temporal patterns of core complex development in the north american cordillera new results including structural observations and u pb zircon shrimp and icpms geochronology constrain the early extensional history of the footwall for the first time high temperature strain with a top wnw shear sense is pervasive throughout metamorphic rocks of the northwestern footwall an isoclinally folded dike yields a crystallization age of 48 47 ma whereas a crosscutting dike yielded an age of 46 ma metamorphic rocks are also intruded by the 50 48 ma pioneer intrusive suite pis a w dipping granodiorite sheet displaying a magmatic fabric northwest trending lineations are locally visible and also defined by anisotropy of magnetic susceptibility indicating that during emplacement the pis was undergoing similarly oriented extensional strain as the enclosing metamorphic rocks therefore wnw directed extension spanning this structural section occurred between 50 and 46 ma following emplacement of crosscutting 46 ma dikes deformation was partitioned into the wnw directed wildhorse detachment motion on the detachment occurred between 38 and 33 ma as documented by previous 40ar 39ar thermochronology it is not clear however whether extension was continuous through the interval between these two time periods although early eocene extension in the pcc was synchronous with extension in core complexes to the north rates of footwall exhumation in central idaho were much lower this southward slowing is compatible with n s differences in inferred subduction zone geometry kinematics and in the internal character of the orogenic wedge

an alternative approach to probabilistic seismic hazard analysis in the aegean region using monte carlo simulation abstract the aegean is the most seismically active and tectonically complex region in europe damaging earthquakes have occurred here throughout recorded history often resulting in considerable loss of life the monte carlo method of probabilistic seismic hazard analysis psha is used to determine the level of ground motion likely to be exceeded in a given time period multiple random simulations of seismicity are generated to calculate directly the ground motion for a given site within the seismic hazard analysis we explore the impact of different seismic source models incorporating both uniform zones and distributed seismicity a new simplified seismic source model derived from seismotectonic interpretation is presented for the aegean region this is combined into the epistemic uncertainty analysis alongside existing source models for the region and models derived by a k means cluster analysis approach seismic source models derived using the k means approach offer a degree of objectivity and reproducibility into the otherwise subjective approach of delineating seismic sources using expert judgment similar review and analysis is undertaken for the selection of peak ground acceleration pga attenuation models incorporating into the epistemic analysis greek specific models european models and a next generation attenuation model hazard maps for pga on a rock site with a 10 probability of being exceeded in 50 years are produced and different source and attenuation models are compared these indicate that greek specific attenuation models with their smaller aleatory variability terms produce lower pga hazard whilst recent european models and next generation attenuation nga model produce similar results the monte carlo method is extended further to assimilate epistemic uncertainty into the hazard calculation thus integrating across several appropriate source and pga attenuation models site condition and fault type are also integrated into the hazard mapping calculations these hazard maps are in general agreement with previous maps for the aegean recognising the highest hazard in the ionian islands gulf of corinth and hellenic arc peak ground accelerations for some sites in these regions reach as high as 500 600 cm s 2 using european nga attenuation models and 400 500 cm s 2 using greek attenuation models

timescales of migmatization melt crystallization and cooling in a cordilleran gneiss dome valhalla complex southeastern british columbia 1 integration of in situ and conventional ion microprobe u th pb zircon and monazite geochronology with 40ar 39ar hornblende biotite and muscovite thermochronology provides a temporal record of metamorphism partial melting fluids and cooling of exhumed midcrustal to lower crustal rocks the valhalla complex southeastern british columbia is one of a series of elongate gneiss domes within the omineca belt of the canadian cordillera we have performed u th pb and 40ar 39ar age measurements on migmatitic gneisses from a range of structural levels and settings within the valhalla complex in an effort to better document the timing of migmatization and exhumation stromatic migmatites and leucosomes crystallized in boudin necks yield concordant u pb zircon ages that cluster near 60 ma and th pb monazite ages of circa 60 50 ma in situ analyses of monazite in samples that contain 60 50 ma however the combined data also suggest that melt crystallization circa 60 ma in the valhalla complex occurred rapidly and before the other domes within the omineca belt cooling at 49 ma throughout the omineca is associated with regional extension and exhumation of migmatites in the domes the presence of abundant migmatites and the similarity in timing of melt crystallization and cooling in domes along the 400 km long omineca belt is consistent with localization of exhumation at the boundary between the flowing crust of the hinterland and the rigid colder crust of the rocky mountain foreland

delineation of seismic sources in probabilistic seismic hazard analysis using fuzzy cluster analysis and monte carlo simulation abstract determination of seismic sources is the first step in probabilistic seismic hazard analysis psha however this step especially in low seismic regions is often controversial in conventional psha procedure determination of seismic sources is merely based on the subjective judgments of experts and in many cases there are great differences among proposed seismic models in a specific region as a result one important source of uncertainty in psha is due to determination of seismic sources in this article by combination of fuzzy clustering analysis and monte carlo simulation an objective method for determination and probabilistic modeling of seismic sources is presented by clustering spatial locations of earthquakes it is possible to specify the extent of each seismic source in an objective way a cluster quality index is used to identify the optimum number of clusters the density and spread of events in each cluster determines the geometrical shape of seismic sources moreover in this article a method is proposed to construct spatial probability density functions pdfs of earthquake locations based on the results of fuzzy clustering analysis the spatial pdf of earthquakes can be used for the generation of synthetic events in monte carlo simulation the azarbaijan region with its varied seismotectonics and generally high seismicity is used as an important area of seismicity in which to develop and demonstrate the application and capability of fuzzy clustering analysis in specifying seismic sources the psha is performed for the city of tabriz and a comprehensive comparison is made between the results of conventional psha ordinary monte carlo hazard analysis and the proposed method the results indicate there is an objective relationship between observed seismicity and seismotectonic evidences in the region moreover the distribution of synthetic events is highly correlated with the observed seismicity seismotectonic and geological information of the region

delineation of shallow seismic source zones using k means cluster analysis with application to the aegean region the selection of specific uniform seismic source zones for use in probabilistic seismic hazard analysis is often controversial recognizing that a consistent approach to source model development is not always possible as the information available relating to geology and seismotectonics can vary from region to region the k means algorithm for hierarchical cluster analysis can be used to partition regions based on observed seismicity the aegean incorporating greece albania former yugoslav republic of macedonia f y r o m southern bulgaria and western turkey with its varied seismotectonics and generally high seismicity is used as an important area of seismicity in which to develop and demonstrate the application of k means two types of algorithm are considered the first is a point source k means that can be used to partition a catalogue of earthquake hypocentres the second is a novel line source development of the algorithm appropriate in seismology as these are analogues for the traces of active faults which is then applied to a catalogue of known fault ruptures in the aegean the common problems of the k means methodology are also addressed ensemble analyses are used to identify better choices of initial estimates for the cluster centres a cluster quality index is used to identify the optimum number of clusters and its robustness assessed when considering different subsets of the observed earthquake catalogue an alternative approach is also implemented monte carlo seismic hazard analysis is used to compare models with different numbers of clusters with the observed seismicity of the 20th century considerable variation is found in the optimum number of clusters identified either by the quality index or by stochastic seismic hazard analysis ultimately the k means partitions of seismicity are developed into source models and their representation of aegean seismotectonics assessed the result is that models containing between 20 and 30 clusters emerge as the most appropriate in capturing the spatial variation in hypocentral distribution and fault type in the aegean

coseismic and postseismic fault slip for the 17 august 1999 m 7 5 izmit turkey earthquake we use global positioning system gps observations and elastic half space models to estimate the distribution of coseismic and postseismic slip along the izmit earthquake rupture our results indicate that large coseismic slip reaching 5 7 meters is confined to the upper 10 kilometers of the crust correlates with structurally distinct fault segments and is relatively low near the hypocenter continued surface deformation during the first 75 days after the earthquake indicates an aseismic fault slip of as much as 0 43 meters on and below the coseismic rupture these observations are consistent with a transition from unstable episodic large earthquakes to stable fault creep sliding at the base of the seismogenic zone

earthquake clustering and energy release of the african arabian rift system the earthquakes associated with continental deformation are spatially and temporally variable and are fundamental in understanding fault activity and seismogenic hazards we conduct kk means cluster analysis on seismicity in the african arabian rift systems to create the first computationally objective analysis of the pattern of earthquakes we use seismic moment to compute spatial variations in maximum credible earthquake mcred and likely time to the next major release of seismic energy our best fit model has 32 clusters of 100 400 km 100 400 km in length with cluster size decreasing northward along the rift and cluster boundaries correlating with major structural segmentation of the rift mcred varies between mwmw 5 2 and 7 4 across the whole dataset with the highest values estimated in portions of the rift where the majority of extension is accommodated by seismogenic failure

geodetic estimate of seismic hazard in the gulf of korinthos the recent 15 june 1995 m0 6 0 1018 n m aigion earthquake in the western gulf of korinthos has focussed attention on the seismic hazard of the region although there have been few large earthquakes in the region during this century the historical record suggests that there may have been many large earthquakes there in the interval 1750 1900 we present geodetic data that give estimates of the rate of extension of the gulf of korinthos during this century and which suggest that less than half of the elastic strain in the central and western gulf of korinthos has been released by earthquakes during this century in contrast the seismic and geodetic strains in the eastern gulf of korinthos are in agreement with each other if the discrepancy between seismic and geodetic strains in the western gulf of korinthos that has accumulated during this century is removed in earthquakes the moment release will be equivalent to several ms 6 5 earthquakes

a new seismic hazard model for new zealand we present a new probabilistic seismic hazard analysis psha for new zealand an important feature of the analysis is the application of a new method for the treatment of historical distributed seismicity data in psha the psha uses the seismicity recorded across and beneath the country to define a three dimensional grid of a values i e parameter a of a gutenberg richter distribution log n yr a bm in which n yr is the number of earthquakes per year recorded inside each grid cell equal to or greater than magnitude m parameter b and the limiting maximum cutoff magnitude of the gutenberg richter distribution are defined from the surrounding region 14 crustal and 23 subcrustal seismotectonic zones are defined for the country and then smoothed across the boundaries of the zones the methodology therefore combines the modern method of defining continuous distributions of seismicity parameters frankel 1995 frankel et al 1996 with the traditional method of defining large area sources and the associated seismicity parameters e g algermissen et al 1990 the methodology provides a means of including deep subduction zone seismicity in a psha preserves the finer scale spatial variations of seismicity rates across a region avoids the undesirable edge effects produced in the traditional method when adjacent area sources enclose areas of significantly different seismicity rates and also enables parameters most reliably defined at a regional scale parameter b and maximum cutoff magnitude of a gutenberg richter distribution and slip type to be incorporated into the psha the psha combines the modeled seismicity data with geological data describing the location and earthquake recurrence behavior of 305 active faults and new attenuation relationships for peak ground acceleration and spectral acceleration developed specifically for new zealand different attenuation expressions are used for crustal and subduction zone earthquakes the resulting psh maps for a 150 year return period show the highest hazard to occur in the center and southwest of the country in the areas of highest historical crustal and deep subduction zone seismicity in contrast the longer return period maps 475 and 1000 year return period show the highest hazard to occur from the southwest to northeast ends of the country along the faults that accommodate the majority of the motion between the pacific and australian plates the maps are currently being used to revise new zealand s building code which has previously been based on pshas that did not explicitly include individual faults as earthquake sources manuscript received 10 april 2001

segmentation of the sumatran fault segmentation of the sumatran fault is discerned using an analytical approach in which a k means algorithm partitions earthquakes into clusters of seismicity along the fault clusters are tessellated into segment zones from which segment lengths and maximum credible magnitude are estimated decreasing the depth of seismicity sampled from 70 to 60 to 50 km reduces interaction with deeper seismicity and results from the k means algorithm initially suggest that the fault has k 14 16 and 16 clusters respectively after inspection it becomes clear that the optimum number of clusters is 16 the 16 cluster model developed into zones generates segment lengths ranging from 22 to 196 km and maximum earthquake potentials in the range of mw 6 5 7 8 the sumatran fault is dominated by eight great central segments distributed approximately symmetrically about lake maninjau these central fault segments dominate the hazard which is less in the far north because segments are shorter

second order moment of central california seismicity 1969 1982 the second order moment cross correlation function of earthquakes in the u s geological survey central california catalog between 1969 and 1982 was calculated with respect to a magnitude threshold m 4 0 over interevent distances up to 80 km and interevent times up to 320 days the statistical procedure results in a representation of the spatial temporal structure of the catalog associated with m 4 0 earthquakes and is capable of revealing patterns too weak to be detected in the space time distribution of seismicity for individual earthquake sequences a method is introduced for identifying aftershocks based on a physical two parameter model of the earthquake interaction process the results show that the aftershock process dominates the second order moment and may even obscure the statistical expression of a precursory process a concentration of foreshocks within 15 km and 3 days of m 4 0 main shocks exhibits an apparent migration toward the main shock loci with velocity 2 6 5 3 km d this concentration may be related to an observed tendency for m 4 0 events to cluster auto correlate over this interevent range with the identified aftershocks removed the residual catalog is poissonion in space and time when two m 4 0 earthquakes occur within 80 km and 40 days of each other aftershock productivity appears to be relatively enhanced in the earlier sequence this suggests that aftershock populations are not solely dependent on their main shocks and that unusually productive aftershock sequences may be predictors of future moderate earthquakes

compressional wave velocity and attenuation at ultrasonic and sonic frequencies in near surface sedimentary rocks laboratory ultrasonic measurements of compressional wave velocity and attenuation were made as a function of effective pressure on samples of limestone sandstone and siltstone taken from a shallow borehole test site the results indicate that the sandstones are pervaded by grain contact microcracks which dramatically affect their compressional wave attenuations clean sandstone shows a compressional wave quality factor q sub p of 24 2 at 5 mpa effective pressure close to the estimated in situ burial pressure and a q sub p of 83 29 at 60 mpa the q sub p of limestones and siltstones at the site show negligible and small increases with pressure in the laboratory respectively the strong pressure dependence of q sub p in clean sandstone was used to infer the presence of in situ microcracks sediment velocities measured in the laboratory at about 1 mhz were compared with those from the full waveform sonic log at about 10 khz implies that they must also be highly attenuating over a significant part of the frequency range 10 khz to 1 mhz to account for the magnitude of the observed velocity dispersion assuming the laboratory q sub p values measured at 5 mpa remain constant down to 10 khzmore predicts the observed dispersion quite well furthermore the sonic log velocities of sandstones limestones and siltstones after normalizing each lithology for porosity and clay content were found to reflect the same pressure depth trends observed in the laboratory the results provide evidence for the existence of in situ microcracks in near surface sediments less

a monte carlo approach to seismic hazard analysis abstract we have developed a monte carlo methodology for the estimation of seismic hazard at a site or across an area this method uses a multitudinous resampling of an earthquake catalog perhaps supplemented by parametric models to construct synthetic earthquake catalogs and then to find earthquake ground motions from which the hazard values are found large earthquakes extrapolated from a gutenberg richter recurrence relation and characteristic earthquakes can be included in the analysis for the ground motion attenuation with distance the method can use either a set of observed ground motion observations from which estimates are randomly selected a table of ground motion values as a function of epicentral distance and magnitude or a parametric ground motion attenuation relation the method has been tested for sites in new england using an earthquake catalog for the northeastern united states and southeastern canada and it yields reasonable ground motions at standard seismic hazard values this is true both when published ground motion attenuation relations and when a dataset of observed peak acceleration observations are used to compute the ground motion attenuation with distance the hazard values depend to some extent on the duration of the synthetic catalog and the specific ground motion attenuation used and the uncertainty in the ground motions increases with decreasing hazard probability the program gives peak accelerations that are comparable to those of the 1996 u s national seismic hazard maps the method can be adapted to compute seismic hazard for cases where there are temporal or spatial variations in earthquake occurrence rates or source parameters

sensitivity analysis of seismic hazard for western liguria north western italy a first attempt towards the understanding and quantification of hazard uncertainty abstract the use of logic trees in probabilistic seismic hazard analyses often involves a large number of branches that reflect the uncertainty in the selection of different models and in the selection of the parameter values of each model the sensitivity analysis as proposed by rabinowitz and steinberg rabinowitz n steinberg d m 1991 seismic hazard sensitivity analysis a multi parameter approach bull seismol soc am 81 796 817 is an efficient tool that allows the construction of logic trees focusing attention on the parameters that have greater impact on the hazard in this paper the sensitivity analysis is performed in order to identify the parameters that have the largest influence on the western liguria north western italy seismic hazard the analysis is conducted for six strategic sites following the multi parameter approach developed by rabinowitz and steinberg rabinowitz n steinberg d m 1991 seismic hazard sensitivity analysis a multi parameter approach bull seismol soc am 81 796 817 and accounts for both mean hazard values and hazard values corresponding to different percentiles e g 16 ile and 84 ile the results are assessed in terms of the expected pga with a 10 probability of exceedance in 50 years for rock conditions and account for both the contribution from specific source zones using the cornell approach cornell c a 1968 engineering seismic risk analysis bull seismol soc am 58 1583 1606 and the spatially smoothed seismicity frankel a 1995 mapping seismic hazard in the central and eastern united states seismol res lett 66 8 21 the influence of different procedures for calculating seismic hazard seismic catalogues epicentral parameters source zone models frequency magnitude parameters maximum earthquake magnitude values and attenuation relationships is considered as a result the sensitivity analysis allows us to identify the parameters with higher influence on the hazard only these parameters should be subjected to careful discussion or further research in order to reduce the uncertainty in the hazard while those with little or no effect can be excluded from subsequent logic tree based seismic hazard analyses

the 17 august 1999 izmit earthquake on 17 august 1999 an earthquake of magnitude 7 4 shook northwestern turkey details on the earthquake9s characteristics and effects across northwestern turkey are provided and are put in the historical context of previous earthquakes in the region the earthquake was the seventh in a series of earthquakes migrating westwards along the north anatolian fault since 1939 information on historical earthquakes modeling and estimates of the slip rate along the fault indicate that the location and severity of the earthquake should not have come as a surprise

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

gps constraints on continental deformation in the africa arabia eurasia continental collision zone and implications for the dynamics of plate interactions 1 the gps derived velocity field 1988 2005 for the zone of interaction of the arabian african nubian somalian and eurasian plates indicates counterclockwise rotation of a broad area of the earth s surface including the arabian plate adjacent parts of the zagros and central iran turkey and the aegean peloponnesus relative to eurasia at rates in the range of 20 30 mm yr this relatively rapid motion occurs within the framework of the slow moving 5 mm yr relative motions eurasian nubian and somalian plates the circulatory pattern of motion increases in rate toward the hellenic trench system we develop an elastic block model to constrain present day plate motions relative euler vectors regional deformation within the interplate zone and slip rates for major faults substantial areas of continental lithosphere within the region of plate interaction show coherent motion with internal deformations below 1 2 mm yr including central and eastern anatolia turkey the southwestern aegean peloponnesus the lesser caucasus and central iran geodetic slip rates for major block bounding structures are mostly comparable to geologic rates estimated for the most recent geological period 3 5 myr we find that the convergence of arabia with eurasia is accommodated in large part by lateral transport within the interior part of the collision zone and lithospheric shortening along the caucasus and zagros mountain belts around the periphery of the collision zone in addition we find that the principal boundary between the westerly moving anatolian plate and arabia east anatolian fault is presently characterized by pure left lateral strike slip with no fault normal convergence this implies that extrusion is not presently inducing westward motion of anatolia on the basis of the observed kinematics we hypothesize that deformation in the africa arabia eurasia collision zone is driven in large part by rollback of the subducting african lithosphere beneath the hellenic and cyprus trenches aided by slab pull on the southeastern side of the subducting arabian plate along the makran subduction zone we further suggest that the separation of arabia from africa is a response to plate motions induced by active subduction

seismic risk of circum pacific earthquakes i strain energy release commonly used earthquake whole process frequency magnitude and strain energy magnitude laws are merged to obtain an analytic expression for an upper bound magnitude to regional earthquake occurrencem3 which is expressed primarily in terms of the annual maximum magnitudem1 and the magnitude equivalent of the annual average total strain energy releasem2 values ofm3 are also estimated graphically from cumulative strain energy release diagrams both methods are illustrated by application to the high seismicity of the circum pacific belt using duda s 1965 data and regionalisation values ofm3 obtained analytically with their uncertainties are in agreement with those obtained graphically empirical relations are then obtained betweenm1 m2 andm3 which could be of general assistance in regional seismic risk considerations if they are found to be of a universal nature for instance m3 andm2 differ by one magnitude unit in subregions of the circum pacific

multivariate statistical analysis for the assessment of groundwater quality under different hydrogeological regimes multivariate statistical analysis has been widely used for hydrogeochemical characterization of groundwater quality in this study hydrochemical data from three hydrological basins were used and two methods factor and cluster analyses were applied the first area is the coastal area of eastern thermaikos gulf where groundwater is influenced by seawater intrusion and geothermal fluids the other two areas are the inland basins of gallikos and perdikas in which agricultural and industrial activities constitute the main anthropogenic pollution sources of groundwater initially the aforementioned methods were applied for each area separately and resulted in a different number of significant factors and clusters while the natural and anthropogenic influences were spatially determined in each area additionally factor and cluster analyses were applied coupling data from all areas therefore five clusters and three major factors were determined distinguishing the hydrochemical processes and impacts from anthropogenic activities in more detail it is worth mentioning that the application of cluster analysis in the coupled groundwater samples of all studied areas resulted beneficially in the most hydrochemically complex area salinization dominates in the coastal area while in gallikos and perdikas basins high concentrations of no3 occur mainly due to agricultural activities and small livestock units the numerous hydrochemical samples are identified as the main issue for the higher discretization and reliability of the second approach nevertheless this study is associated with a number of limitations of multivariable statistical analysis regarding extreme concentrations of cl and na this issue stimulates further research in overcoming and understanding these drawbacks