modelling deformation rates in the western gulf of corinth rheological constraints summary the gulf of corinth is one of the most active extensional regions in the mediterranean area characterized by a high rate of seismicity however there are still open questions concerning the role and the geometry of the numerous active faults bordering the basin as well as the mechanisms governing the seismicity in this paper we use a 2 d plane strain finite element analysis to constrain the upper crust rheology by modelling the available deformation data gps and geomorphology we consider a ssw nne cross section of the rift cutting the main active normal faults aigion west eliki and off shore faults the models run for 650 kyr assuming an elasto viscoplastic rheology and 1 3 cm yr 1 horizontal extension as boundary condition resulting from gps data we model the horizontal and vertical deformation rates and the accumulation of plastic strain at depth and we compare them with gps data with long term uplift rates inferred from geomorphology and with the distribution of seismicity respectively our modelling results demonstrate that dislocation on high angle normal faults in a plastic crustal layer plays a key role in explaining the extremely localized strain within the gulf of corinth conversely the contribution of structures such as the antithetic trizonia fault or the buried hypothetical subhorizontal discontinuity are not necessary to model observed data

hydrothermal alteration of tertiary igneous rocks from the isle of skye northwest scotland hydrothermal alteration of tertiary granites from skye involed the reaction of igneous amphibole biotite ferroaugite fayalite alkali feldspar plagioclase feldspar magnetite and ilmenite with aqueous fluid primarily to combinations of secondary alkali feldspar chlorite and montmorillonite lesser amounts of muscovite calcite epidote prehnite zeolite and pyrite also developed during mineralogical alteration of the granites there was a net addition to rock of h and a net loss of ca fe and probably na there is no positive evidence for a significant change in their al si mg or k contents hydrothermal alteration of skye granite involved not only large scale migration of 18o 16o d and h but also of ca fe and probably na mineral thermometry combined with textural observations suggests that chemical isotopic and most mineralogical alteration were synchronous and occurred at 350 450 c textural observations further suggest that the mechanism of isotopic exchange between granite and hydrothermal fluid primarily was solution reprecipitation

extensional tectonics and mafic plutons in the ketilidian rapakivi granite suite of south greenland abstract the early proterozoic rapakivi suite in the ketilidian mobile belt of south greenland is bimodal with an abundance of mafic plutons which mingled and hybridised with the rapakivi granites basic rocks lacking signs of hybridisation and with mineralogy and bulk compositions apparently unaffected by proximity to the granites are enriched in large ion lithophile element lile relative to high field strength element hfse and have moderate nb depletion these are characteristics common to basic rocks found in back arc basins this tectono magmatic environment supports a model for the late ketilidian of crustal extension probably caused by slab roll back and is in keeping with the low pressure high temperature metamorphic conditions which prevailed when the rapakivi suite was emplaced nd and sr isotopes confirm the juvenile character of the ketilidian crust and rapakivi granites hybrid mafic rocks have low end compared to depleted mantle while apparently unhybridised examples have also undergone some isotopic modification

microstructures and their implications for faulting processes insights from dglab core samples from the gulf of corinth abstract we have examined microstructures mineralogical composition geochemical alteration and texture of four selected fault rock samples from the deep geodynamical laboratory dglab gulf of corinth project using optical microscopy cathodoluminescence microscopy cl scanning electron microscopy sem transmission electron microscopy tem and synchrotron x ray diffraction measurements the fault core is composed of red and gray clayey gouge material and surrounded by a damage zone of brecciated limestones pressure solution features calcite veins and calcite clasts in the breccia and gouge material attest the presence of paleo fluids and fluid driven mass transfer during deformation differences in cl colors between the matrix and calcite vein cement and inside the vein cement suggest repeated infiltration of fluids with different composition from various sources formation water and meteoric water twin lamellae densities estimated in calcite veins are used as paleo piezometer the deduced differential stress is 140 70 mpa for the older vein generation and appears to be higher than stress for the youngest veins 45 23 mpa in spite of the relatively small clay content in both samples newly formed clay minerals have been observed in gray as well as red clayey gouge material differences between gray and red clay gouge material are found in fault rock composition porosity and clay fabric the proportion of chlorite in the red gouge is significantly less than that in the gray gouge whereas the initial porosity is significantly higher than in the gray gouge material the detection of a well oriented clay fabric in red clay gouge samples is unique in comparison to other major fault zones

active faulting at the western tip of the gulf of corinth greece from high resolution seismic data abstract the gulf of corinth is one of the fastest spreading intra continental rifts on earth gps data indicate that the rift is currently opening in a nne ssw direction with a rate of extension reaching up to 16 mm yr 1 in its westernmost part although the rest of the offshore rift has been well studied the western tip of the rift is still poorly explored we present an accurate map of submarine faults in this area based on two high resolution seismic reflection surveys single channel sparker in the eastern part of the studied area the sedimentary infill is affected by the known north eratini south eratini and west channel faults further to the west the seafloor is mostly flat and is bounded to the north by the normal south dipping trizonia fault to the north the shallower part of the gulf shows to the east a diffuse pattern of normal and strike slip deformation which is replaced to the west by a 7 5 km long se striking strike slip fault zone called the managouli fault zone to the westernmost tip of the gulf in the nafpaktos basin two fault sets with different strikes are encountered the one with a ne sw strike exhibits a clear strike slip component the western tip of the gulf of corinth is the only part of the corinth rift where convincing evidence for strike slip movement has been found this fault pattern is likely related to the complex deformation occurring at the diffuse junction at the western tip of the rift between three crustal blocks continental greece peloponnese and the ionian island akarnania block

a microseismic study in the western part of the gulf of corinth greece implications for large scale normal faulting mechanisms summary we present the results of a dense seismological experiment in the western part of the gulf of corinth psathopyrgos aigion area one of the most active rifts in the aegean region for which we have precise tectonic information the network included 51 digital stations that operated during july and august 1991 covering a surface of 40 x 40 km2 among the 5000 recorded events with ml ranging between 1 0 and 3 0 we precisely located 774 events we obtained 148 well constrained focal mechanisms using p wave first motions of these 60 also have mechanisms obtained by combining the p wave first motions with the s wave polarization directions the observed seismicity is mainly located between 6 and 11 km depth most of the fault plane solutions correspond to e w striking normal faulting in agreement with the geological evidence most of the well determined mechanisms indicate a nodal plane dipping 10 25 due north and a steep south dipping plane a similar asymmetry is also seen in the seismicity distribution and in the overall geological structure of the corinth rift we discuss this evidence and the inference of a deep detachment zone a structure where the major faults seen at the surface appear to root a large part of the microseismic activity appears to cluster in regions near the junctions of the main faults with the proposed detachment zone this feature of the microseismicity is interpreted in terms of stress transfer and stress concentration in regions of probable nucleation of future large earthquakes

the 1786 earthquake triggered landslide dam and subsequent dam break flood on the dadu river southwestern china abstract chinese historic documents recorded that on june 1 1786 a strong m 7 75 earthquake occurred in the kangding luding area sichuan southwestern china resulting in a large landslide that fell into the dadu river as a result a landslide dam blocked the river ten days later the sudden breaching of the dam resulted in catastrophic downstream flooding historic records document over 100 000 deaths by the flood this may be the most disastrous event ever caused by landslide dam failures in the world although a lot of work has been carried out to determine the location magnitude and intensity of the 1786 earthquake relatively little is known about the occurrence and nature of the landslide dam in this paper the dam was reconstructed using historic documents and geomorphic evidence it was found that the landslide dam was about 70 m high and it created a lake with a water volume of about 50 106 m3 and an area of about 1 7 km2 the landslide dam breached suddenly due to a major aftershock on june 10 1786 the peak discharge at the dam breach was estimated using regression equations and a physically based predictive equation the possibility of a future failure of the landslide seems high particularly due to inherent seismic risk and detailed geotechnical investigations are strongly recommended for evaluating the current stability of the landslide

active faulting within the offshore western gulf of corinth greece implications for models of continental rift deformation discrimination between different lithospheric extension models focusing on the roles of low angle vs high angle faulting and how strain is distributed requires high fidelity imaging of brittle deformation high resolution seismic reflection and multibeam bathymetric data in the western gulf of corinth continental rift were collected to establish the contribution of offshore faults to extension onshore fault slip here is significantly less than expected from geodetic strain rates the rift at this location is a half graben tilted to the north by s dipping faults within the uppermost crust a basement horst on the northern margin is uplifted by the north and south eratini faults and the axial channel is fault controlled subsided lowstand shorelines in the hanging wall of the north eratini and the well studied aigion fault suggest that the faults have similar displacements summed extension from the four major faults across this part of the rift eliki subchannel south eratini north eratini is 8 16 mm yr thereby reconciling geologic and geodetic data sets distributed deformation across isolated multiple faults can model this part of the rift without recourse to and potentially incompatible with an underlying low angle detachment

metallogeny of south greenland a review of geological evolution mineral occurrences and geochemical exploration data abstract south greenland has been the site of historic mining of cryolite copper graphite and gold hosts mineral deposits with gold uranium zinc niobium tantalum zirconium hafnium ree iron titanium vanadium fluorite and graphite and has additional potential for lithium beryllium phosphorus gallium and thorium data from stream sediment geochemical surveys document that south greenland is enriched in a range of these elements relative to the rest of greenland and to estimates of the upper crust composition distribution patterns for individual elements within south greenland exhibit enriched regions that are spatially related to lithological units crustal structure and known mineralisation the northern domain of south greenland includes the southernmost part of the orthogneiss dominated north atlantic craton orogenic gold mineralisation is hosted by quartz veins and hydrothermally altered rocks associated with shear zones intersecting the mesoarchaean tartoq group of mafic metavolcanic rocks geochemical exploration indicates that additional potential for gold mineralisation exists within palaeoproterozoic supracrustal rocks overlying the archaean basement rocks formed during the palaeoproterozoic ketilidian orogeny occupy a major part of south greenland and has been divided into two domains the central domain is underlain by the julianehab igneous complex forming a 100 km wide ene wsw zone centrally across south greenland intrusive and extrusive mostly felsic magmatic rocks were emplaced in two main stages 1850 1830 and 1800 1780 ma in a continental arc setting positive anomalies in aeromagnetic data indicate that mafic plutons are common in the late igneous complex intra arc mafic metavolcanic rocks contain syngenetic stratabound copper sulphide and epigenetic shear zone hosted copper silver gold mineralisation at kobberminebugt and kangerluluk whereas metasedimentary and metapyroclastic rocks contain stratabound uraninite mineralisation orthomagmatic iron titanium vanadium mineralisation is hosted by a gabbro a potential for porphyry type mineralisation related to the late intrusive stages of the julianehab igneous complex is suggested by showings with copper molybdenum and gold together with stream sediment anomalies for these elements vein type uranium mineralisation occurs in fault zones in the julianehab igneous complex related to mesoproterozoic rifting the southern domain contains an assemblage of palaeoproterozoic metasedimentary and metavolcanic rocks that underwent moderate to strong deformation peak ht lp metamorphism and partial melting with subsequent retrograde exhumation at 1790 1765 ma the supracrustal rocks contain syngenetic au as sb u and zn mineralisation in volcanic or graphite and sulphide rich sedimentary environments graphite was mined historically at two sites many stream sediment gold anomalies are located in a ne trending belt along the boundary between the early julianehab complex and the supracrustal rocks to the south they reflect a number of auriferous quartz vein occurrences including the nalunaq gold deposit hosted in a system of shear zones and probably generated as orogenic gold during ketilidian accretion the 1755 1730 ma a type ilua plutonic suite is the latest magmatic event in the ketilidian orogen the 1300 1140 ma gardar period involved continental rifting sedimentation and alkaline magmatism numerous dykes and 10 ring shaped intrusion complexes were formed across south greenland an orthomagmatic iron titanium vanadium deposit is hosted by troctolitic gabbro residual magmas and fluids resulting from extreme magmatic differentiation possibly combined with assimilation of older crust created mineral deposits including cryolite that was mined at ivigtut large low grade deposits of uranium rare earth elements zinc at kvanefjeld and tantalum niobium rare earth element zirconium at kringlerne in the ilimaussaq complex as well as tantalum niobium rare earth elements at motzfeldt so in the igaliko complex the south greenland crustal evolution records effects of mantle processes such as lithospheric extension subduction and underplating which resulted in recurrent magma emplacement in tectonically active environments as such the geology of south greenland reflects events and circumstances that are favourable to the generation and preservation of hydrothermal ore forming fluid systems during the ketilidian orogeny as well as to the development of extreme rock compositions within the gardar alkaline igneous province

dating san andreas fault earthquakes with lichenometry regionalrockfalleventsinthesierranevadaofcaliforniaare caused by distant earthquakes on the northern and southern san andreasfaultaswellasbylocalearthquakes lichenometricdating of synchronous pulses of rockfalls that are presumed to be caused by five historical earthquakes suggests an accuracy of 2 2 3 5 yr 95 confidence level for dating young events comparison of lichenometric ages for prehistorical rockfalls with precise radiocarbon ages of surface rupture times at the pallett creek and wrightwood paleoseismology sites indicates that earthquakes on the southern san andreas fault caused rockfalls 200 to 400 km to the north a major rockfall event at about a d 1690 supports the fumal et al 1993 model for a san andreas fault earthquake that was not detected at pallett creek the a d 1690 event in the chronology indicates that the earthquake recurrence interval was shorter and that the degree of clustering of times of earthquakes was less on the mojave segment of the san andreas fault than previously thought

scaling properties within the gulf of corinth greece comparison between offshore and onshore active faults abstract the gulf of corinth greece is a 110 km long by 30 km wide active graben displaying strong seismicity hosted both on north and south dipping normal faults this complex fault pattern consists of two fault populations offshore and onshore the offshore fault population is investigated by densely arranged seismic reflection profiles during the last 20 years whereas the onshore fault population displays spectacular and well exposed faults delineated by high accuracy mapping we analyzed fault length and throw in order to study the scaling properties of 136 well determined offshore and onshore faults and the comparison between the two datasets we examined the statistical properties on both fault populations in order to describe the role of segmentation in the growth of faults and the different stages of the evolution of the fault networks our results on power law relationships associated with the scaling properties of the fault zones in the gulf of corinth suggest that both fault populations are bi fractal providing the initiation of a sature state in deformation in addition the vertical throw of faults shows that both fault populations have similar properties but different distributions below and above 5 km respectively displacement length ratios show that faults larger than 9 km appear to accumulate throw without any dramatic change to their length these observations combined with other geophysical studies within the gulf suggest that the characteristic fault lengths of 5 km and 9 km can be correlated to the crustal mechanical structure and the seismicity of the gulf

development of microporosity diffusion channels and deuteric coarsening in perthitic alkali feldspars turbidity is an almost universal feature of alkali feldspars in plutonic rocks and has been investigated by us in alkali feldspars from the klokken syenite using sem and tem it is caused by the presence of myriads of tubular micro inclusions either fluid filled micropores or sites of previous fluid inclusions and is associated with coarsening of microperthite and development of sub grains micropores are abundant in coarsened areas in which porosities may reach 4 5 but are almost absent from uncoarsened pristine braind microperthite areas the coarsening is patchy and involves a scale increase of up to 103 without change in the composition of the phases low albite and low microcline or in the bulk composition of the crystal it occurs abruptly along an irregular front within individual crystals which retain their original shapes the coherent braid microperthite gives way across the front to an irregular semi coherent film perthite over a few m and then to a highly coarsened irregular patch perthite containing numerous small sub grains on scales of a few hundred nm in both phases the coarsening and micropore formation occured at a t 400 450 c and it is inferred to have been driven by the release of coherent strain energy low angle grain boundary migration being favoured by a fluid the patchy nature of the coarsening and the absence of a relationship with initial grain boundaries suggest that the fluid was of local origin possibly arising in part through exsolution of water from the feldspar the sub grain texture and microporosity modify profoundly the permeability of the rock and greatly enhance the subsequent reactivity of the feldspars

normal fault growth and linkage in the whakatane graben new zealand during the last 1 3 myr determination of fault growth rates and fault network evolution at time scales from 104 106 years has been hampered by a lack of a well constrained stratigraphic succession that provides a high fidelity record of fault development over these time periods here we show how seismic reflection data of different spatial resolutions can be used to constrain the linkage history and displacement rate variations of a single major fault we present data collected in the offshore whakatane graben bay of plenty new zealand where intense normal faulting occurs as a result of active back extension the focus of our study is the rangitaiki fault a linked segmented normal fault which is the dominant active structure in the graben the total linked fault length is c 20 km long and has a displacement of up to 830 130 m in the top 1 5 km of sediments the fault has been actively growing for the last 1 34 0 51 ma and has developed from isolated fault segments to a fully linked fault system initially the dominant process of fault growth was tip propagation with an average and maximum displacement rates of 0 52 0 18 mm yr 1 and 0 72 0 23 mm yr 1 respectively interaction and linkage became more significant as the fault segments grew towards each other resulting in the fault network becoming fully linked between 300 and 18 ka following fault segment linkages the average displacement rate of the fault network increased by almost three fold to 1 41 0 31 mm yr 1 while the maximum displacement rate increased to 2 72 0 61 mm yr 1 this is the first time that the growth rate of unlinked fault segments has been resolved and has been shown to be slower than in the subsequent linked fault system

high sediment yields and cool wet winters test of last glacial paleoclimates in the northern mediterranean opposing models have been proposed for last glacial paleoclimates in the mediterranean area to discriminate between the alternative models we calculate variations in sediment yield within a high resolution stratigraphic framework developed for the alkyonides basin central greece latest quaternary highstand deposits are distinguised from lowstand lake corinth deposits on the basis of seismic reflection data and micropaleontological and palynological analyses of drop cores after depth conversion and calculation of solid sediment masses in successive time slices sediment discharge rates during the last glacial lowstand interval ca 70 12 ka are shown to have exceeded discharge rates during the preceeding interglacial highstand interval ca 128 70 ka by 60 implying enhanced seasonality during the glacial period with cool dry summer and wet winter conditions in the region sediment yield calculations can thus provide an empirical test of paleoclimate models and offer input to sequence stratigraphic models

high angle not low angle normal faults dominate early rift extension in the corinth rift central greece low angle normal faults lanfs accommodate extension during late stage rifting and breakup but what is more difficult to explain is the existence of lanfs in less stretched continental rifts a critical example is the 5 ma corinth rift central greece where microseismicity the geometry of exposed fault planes and deep seismically imaged faults have been used to argue for the presence of 30 dipping normal faults however new and reinterpreted data call into question whether lanfs have been influential in controlling the observed rift geometry which involves 1 exposed steep fault planes 2 significant uplift of the southern rift margin 3 time averaged tens of thousands to hundreds of thousands of years uplift to subsidence ratios across south coast faults of 1 1 1 2 and 4 north margin subsidence we test whether slip on a mature lanf can reproduce the long term tens of thousands of years geometry and morphology of the corinth rift using a finite element method to model the uplift and subsidence fields associated with proposed fault geometries models involving lanfs at depth produce very minor coseismic uplift of the south margin and post seismic relaxation results in net subsidence in contrast models involving steep planar faults to the brittle ductile transition produce displacement fields involving an uplifted south margin with uplift to subsidence ratios of 1 2 3 compatible with geological observations we therefore propose that lanfs cannot have controlled the geometry of the corinth rift over time scales of tens of thousands of years we suggest that although lanfs may become important in the transition to breakup in areas that have undergone mild stretching do not have significant magmatic activity and do not have optimally oriented preexisting low angle structures high angle faulting would be the dominant strain accommodation mechanism in the upper crust during early rifting

fault displacement rates on a range of timescales abstract displacements on tectonic faults primarily accrue during earthquakes at rates that vary through time to examine the processes that underlie the temporal changes in fault displacement rates we analyse displacements and displacement rates for time periods from the present to 5 10 20 300 500 1000 and 5000 kyr for 261 active reverse or normal faults from a worldwide dataset displacement rates depart from million year average rates by up to three orders of magnitude with the size of these departures inversely related to the duration of the sample period and to fault length short term 20 kyr displacement rates generally span a greater range on small faults than large a feature which suggests more variable growth on smaller faults simple earthquake slip modeling shows that variations in displacement rates require changes in both recurrence interval and slip per event and do not support the characteristic slip earthquake model as long as fault system strain rates are uniform displacement rates generally become constant over time periods between 20 and 300 kyr with the length of time required to reach stability being inversely related to the regional basin wide strain rates stable long term displacement rates and fluctuations in earthquake recurrence intervals and slip arise in part due to fault interactions

the importance of microearthquakes in crustal extension of an active rift a case study from new zealand received 24 august 2012 revised 29 november 2012 accepted 19 december 2012 1 the amount of extension accommodated in active rifts by earthquakes that do not rupture the ground surface e g mw 5 5 is often poorly constrained the matata earthquake sequence mes a high quality dataset of 2563 relocated microearthquakes 1 mw 4 7 that ruptured the taupo rift in new zealand over a period of 49 months has been used to quantify the proportion of extension produced by small to moderate sized earthquakes analysis shows that the extension rate across the rift due to the mes is 2 4 0 7 mm yr at 1s standard deviation an average extension rate for small to moderate magnitude earthquakes which also prevailed during the preceding 28 years 1977 2004 and represents up to 30 of the total contemporary deformation recorded across the north taupo rift by gps 15 5 mm yr the bulk of the mes 94 occurred at depths of 1 5 to 6 5 km and may not be observed in geological datasets e g as displacements of the ground or near surface horizons small scale faulting associated with microseismicity may thus record strains not measured by geological datasets and constitute an important component of the 3 10 mm yr disparity between geological and gps rates of extension across the taupo rift

evolution of the offshore western gulf of corinth the young gulf of corinth rift in central greece is an ideal place to study processes occurring during the initiation and early stages of continental extension at the east end of the 100 km long e w rift holocene extension on n dipping faults equates to geodetic extension rates at the western end however estimated extension rates on n dipping onshore faults account for only 20 40 of the geodetically measured rates 10 15 mm yr we use high quality multichannel seismic reflection and swath bathymetry data to investigate the tectonics of the western gulf and quantify the contribution of offshore fault activity toward total rift extension five major offshore faults generate the variable basement topography and a ca 0 4 ma unconformity separates stratigraphy into two main packages basin fill geometry indicates that during the early stages of subsidence of the offshore western gulf s dipping faults were the dominant border fault structure this is still the case at the western end of the western gulf however elsewhere n dipping faults on the south margin are now relatively more dominant and cause stratigraphy to tilt south the temporally and spatially varying rift structure contrasts with the simple consistently n dipping border fault half graben geometry of the east gulf of corinth combined west gulf offshore and onshore holocene fault extension rates total 5 14 5 mm yr within the range calculated geodetically and render enhanced slip on a low angle detachment surface beneath the western gulf unnecessary

alternating marine and lacustrine sedimentation during late quaternary in the gulf of corinth rift basin central greece abstract the gulf of corinth in central greece has a maximum depth of about 900 m and is separated from the open sea by the rion strait with a sill depth of 62 m marked by an extensive submarine terrace during eustatic sea level lowstands the gulf of corinth was a lake under lacustrine conditions stratified sediments accumulated in the deep water basins and turbid underflows from rivers eroded the basin slopes as the sea level rose marine waters flooded the gulf and deltas prograded across the shelves in shallow water areas two key reflectors termed z and x are terrace surfaces commonly erosional which mark the base of the overlying deltaic sequences in deep water basins z and x mark the top of the acoustically stratified sediments interpreted as lacustrine turbidites reflectors y and w mark the base of these stratified intervals and overlie acoustically transparent sections similar to the holocene section the last lacustrine conditions in the gulf z to y were during isotopic stage 2 and terminated about 12 000 yr ago age estimates based on sedimentation rates suggest that the x to w interval corresponds to the stage 4 lowstand of sea level in the western gulf of corinth shoreline transgressive surfaces corresponding to minor transgressions in stage 5 and to major transgression at the end of stage 6 are recognised this seismic stratigraphy permits a detailed interpretation of the history of the gulf of corinth in the past hundred thousand years it also provides a general model for sedimentation in rift basins in which marine and lacustrine sediments alternate

cryptoperthites and cooling rate in a layered syenite pluton a chemical and tem study alkali feldspars in the klokken layered syenite south greenland are optically either coarse turbid deuteric patch perthites or clear unaltered fine braid microor cryptoperthites irregular clear volumes can be found in most turbid grains electron microscopy shows that all clear crystals or volumes are cryptoperthites in which the periodicity of the exsolution lamellae increases systematically with distance from the roof of the intrusion from 40 nm to 300nm they are composed of low albite and diagonally associated maximum microcline a secondary coarsening is responsible for optically visible braid microperthites the layered series consists of interleaved granular syenites and coarser grained laminated syenites with mineral layering microprobe analyses show a downward decrease in ca and ba in the granular syenite feldspars consistent with chilling from the roof inwards most laminated syenite feldspars contain 1 an increasing to 5 in mafic layers the periodicity of the exsolution lamellae in the laminated syenite feldspars is consistently up to twice that in adjacent granular syenites periodicity is not influenced by ab or or an content but high an feldspars have continuous zig zag intergrowths while others are more lozengeshaped lamellar periodicities largely reflect cooling rate in the pluton cooling times in the exsolution interval were probably about 103 104 years at the top of the series whereas existing experimental data suggest that the periodicities would be reached in a few days or years the periodicities at the top of the granular series are only slightly greater than experimentally determined initial wavelengths for spinodal decomposition suggesting that little or no coarsening occurred despite the long cooling times coarsening did occur lower in the pile framework ordering and twinning must slow or stop coarsening the difference in periodicity between the granular and laminated syenite series may be caused by differences in amount of water incorporated in the feldspar structure from the magma the exsolution of this water at low temperatures could be the cause of the deuteric unmixed patch perthites small volumes of cryptoperthite which have escaped deuteric unmixing may be common in igneous rocks in general and may be useful relative indicators of cooling rate

sedimentary impacts of recent moderate earthquakes from the shelves to the basin floor in the western gulf of corinth abstract in seismically active areas long term records of large earthquakes are indispensable to constrain reccurence patterns of large earthquakes in the western corinth rift one of the most active areas in europe in terms of seismicity data about ancient earthquakes are still insufficient despite historical records covering the last two millenia and several studies in onshore paleoseimology in this paper we test the use of offshore sediments from the gulf of corinth to identify sediment failures and tsunamis that have been triggered by historical earthquakes two shelves 40 100 m deep one sub basin 180 m and the basin floor 330 m have been sampled by short gravity cores the cores were analyzed in order to identify and characterize event deposits the age control has been provided by 137cs and 210pb activity measurements showing that the cores represent 2 to 4 centuries of sedimentation in each site sandy event deposits are interbeded in the muddy hemipelagic sedimentation the age of event deposits has been compared to the record of historical earthquakes using new and published macroseismic data this comparison shows temporal coincidence of some event deposits and documented earthquakes with a macroseismic intensity vii in the area e g in 1861 ce 1888 ce and 1909 ce in nearshore shallow water settings the record of event deposits does not exactly fit with the historical record of large earthquakes because too few event deposits are present this may be due to the absence of sediment failures or to a lower preservation of the deposits in such settings in the deepest site in the basin floor the correspondence is better a sandy turbidite probably corresponds to each large earthquake since 1850 ce except one aseismic sediment density flow that occurred at the end of the 20th century surprisingly the ms 6 2 june 15 1995 aigion earthquake is only possibly recorded in one nearshore site on the aigion shelf in the form of a tsunami back wash flow deposit this study showed that moderate earthquakes m 5 8 6 5 can significantly impact marine sediments regarding the evaluation of seismic hazard in the area the basin floor is proposed as a promising site for long term paleoseismology in the gulf of corinth while shallower settings need to be considered more carefully

implications of structural segmentation during earthquakes the 1995 egion earthquake gulf of corinth greece the egion earthquake which occurred in the gulf of corinth central greece ms 6 2 on 15 june 1995 was caused by normal slip on the north dipping and wnw trending egion fault the egion fault ruptured at depth during the egion mainshock and probably re ruptured at shallow level during the largest aftershock the surface trace of the egion fault has a segmented geometry linkage between three segments which show long term deformation differences as well as coseismic segmentation enabled all segments to be incorporated in an earthquake segment the surface ruptures continued to grow after the coseismic motion the afterslip throw of the fault 10 weeks after the main event was equal to the 3 cm value for maximum coseismic slip this afterslip was accompanied by uplift of the footwall block and a warp like hangingwall subsidence folding this pattern of deformation was associated with more complex deformation at the western end of the earthquake segment here afterslip was accompanied by general subsidence of the whole area between 25th june and 30th july followed by uplift of the whole area without afterslip between 30th july and 2nd september the afterslip rate averaged over the 73 day period after the main event varied from 0 48 mm day 1 along the central part of the earthquake segment to 0 16 mm day 1 at the eastern end of the earthquake segment

fluid involvement in the active helike normal fault gulf of corinth greece abstract rock fabric and mineralogical composition from the fault core and the unaffected protolith have been used to define the role of the segmented helike fault to fluid flow sixty samples were investigated by xrd sem observation and sem eds microanalyses detrital smectite calcite and quartz represent the mineral assemblage at the crest of the footwall block in foniskaria sampling site in this site smectite is enriched at the rims of the fault core all other sampling sites located at the base of the fault scarp are characterized by detrital and newly formed minerals detrital minerals include plagioclase quartz calcite and illite in nikolaiika sampling site and smectite illite kaolinite quartz calcite in selinous sampling site in the latter sampling site erionite and cerussite are newly formed minerals with erionite considered as the hydrothermal alteration product of fluids at 80 100 c at the eastern fault segment illite quartz and calcite t13 site corresponds to detrital minerals mineralogy in the fault core reflects its high permeability to down flowing meteoric water and weak hydrothermal alteration the rock fabric suggests mineral alignment parallel to the fault plane mineralogy indicates that the aigion helike and pyrgaki faults in the gulf of corinth host hydrothermal activity at shallow levels

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

prehistorical earthquakes on the alpine fault new zealand studies of synchronous prehistorical landslides in rugged plate boundary mountain ranges can be used to estimate times of earthquakes to locate the earthquake generating fault zones and to describe patterns of seismic shaking lichenometry can date regional rockfall events caused by large earthquakes in the southern alps of new zealand with a 95 confidence level precision of 10 years spatial variation of rockfall abundance an index of seismic shaking is a function of the intensity and duration of seismic shaking and hillslope sensitivity to earthquakes four of the earthquakes of the past 1000 years appear to have caused exceptionally widespread regional rockfall events that were largest opposite the 350 km long cook segment of the alpine fault lichenometric age estimates 10 years of these cook segment earthquakes at 1748 1489 1226 and 967 a d are supported by radiocarbon and weathering rind age estimates of times of coseismic geomorphic processes and by times of prehistorical forest disturbance events a mean earthquake recurrence interval of 260 years 15 years and similar patterns of seismic shaking imply constant rupture length and slip per event in accord with the characteristic earthquake model

ancient landslide dam events in the jishi gorge upper yellow river valley china some scholars have argued that the formation and outburst of an ancient dammed lake in the jishi gorge at ca 3700 cal yr bp resulted in the destruction of lajia the site of a famous prehistoric disaster in the guanting basin upper yellow river valley china however the cause of the dammed lake and the exact age of the dam breaching are still debated we investigated ancient landslides and evidence for the dammed lake in the jishi gorge including dating of soil from the shear zone of an ancient landslide sediments of the ancient dammed lake and loess above lacustrine sediments using radiocarbon and optically stimulated luminescence osl dating methods six radiocarbon dates and two osl dates suggested that the ancient landslides and dammed lake events in the jishi gorge probably occurred around 8100 cal yr bp and the ancient dammed lake was breached between 6780 cal yr bp and 5750 cal yr bp hence the outburst of the ancient dammed lake in the jishi gorge was unrelated to the ruin of the lajia site but likely resulted in flood disasters in the guanting basin around 6500 cal yr bp

kinematic analysis of secondary faults within a distributed shear zone reveals fault linkage and increased seismic hazard abstract complex multifault earthquake ruptures involving secondary faults emphasize the necessity to characterize their seismogenic potential better and study their relationship with major faults to improve the seismic hazard assessment of a region high resolution geophysical data were interpreted to make a detailed characterization of the averroes fault and the north averroes faults which are poorly known secondary right lateral strike slip faults located in the central part of the alboran sea western mediterranean these faults appear to have evolved since the pliocene as part of a distributed dextral strike slip shear zone in response to local strain engendered by the diverging movement of the carboneras fault to the north and the yusuf and alboran ridge faults to the south in addition the architecture of these faults suggests that the averroes fault may eventually link with the yusuf fault thus leading to a higher seismogenic potential therefore these secondary faults represent a hitherto unrecognized seismogenic hazard since they could produce earthquakes up to moment magnitude mw 7 6 our results highlight the importance of the role played by secondary faults in a specific kinematic framework their reciprocal linkage and their mechanical relationship with the main faults could lead to future complex fault ruptures this information could improve fault source and earthquake models used in seismic and tsunami hazard assessment in this and similar regions

18o 16o homogenization of the middle crust during anatexis the thor odin metamorphic core complex british columbia the occurrence of isotopically uniform quartz 18 o 12 5 0 5 and feldspar 10 9 0 7 throughout different rock types indicates that much of a 6 km thick section of the mid crustal selkirk allochthon underwent internally buffered 18 o 16 o homogenization during paleocene melting and decompression as it moved up the monashee thrust ramp areas of uniform 18 o are those with the most leucogranite or those subjected to severe anatexis only locally in the most impermeable or refractory zones did 18 o exchange among the rocks leucogranite melts and aqueous fluids fail to go to completion i e in the deepest parts of the section in a marble rich zone around some thick amphibolites and in most garnets evidence for 18 o 16 o heterogeneity in the protoliths of these rocks is observed in stratigraphically correlative lower grade units elsewhere in british columbia as well as in garnets that coexist with isotopically homogeneous quartz in our model 18 o 16 o homogenization accompanied muscovite dehydration and partial melting of pelites with only minor influx of external h 2o followed by release of magmatic h 2o from these melts triggering further melting of adjacent feldspathic assemblages as they were uplifted 20 km during thrusting just prior to onset of detachment faulting locally low 18 o in feldspar down to 3 8 and profound quartz feldspar 18 o 16 o disequilibrium were imprinted at shallow levels during meteoric hydrothermal alteration associated with eocene detachment faulting

normal faulting and crustal deformation alkyonides gulf and perachora peninsula eastern gulf of corinth rift greece geophysical structural geochronological and geomorphological data indicate that the psatha east alkyonides skinos and pisia faults are holocene active structures whereas the status of the west alkyonides strava perachora and loutraki faults is less certain we see no evidence for significant lateral surface fault growth new data for late pleistocene footwall uplift of the psatha fault are comparable with previously estimated holocene rates pre holocene stratigraphic sequences in the alkyonides gulf allow calculation of vertical displacement on the skinos fault of 1 42 1 60 km over a period of 0 6 ma previous palaeoseismological studies indicate comparable displacement rates extrapolated to 0 61 2 20 ma whereas extrapolation of previous geodetic data indicate a range of 0 17 0 46 ma the latter is too short given the evidence of the stratigraphic record signifying either that these data may not be representative of longer term rates or that significant deformation has taken place elsewhere for example on offshore antithetic faults a case is established for uniform late quaternary post mis 7 uplift of the perachora peninsula at rates of c 0 2 0 3 mm a 1 the lack of regional tilting over perachora corinth isthmia is in marked contrast to the situation in the alkyonides megara basins to the east

geometry and slip rate of the aigion fault a young normal fault system in the western gulf of corinth the aigion fault is one of the youngest major normal faults in the gulf of corinth greece with an immature displacement profile based on geometry slip rate and comparison with regional faults we estimate the fault system length at 10 km we find the slip rate of the fault system is 3 5 1 mm yr decreasing to 2 5 0 7 mm yr close to its eastern tip complex fault geometry and displacement profiles on the shelf east of aigion are consistent with the latter as the eastern tip location analysis of slip on this fault system and the established fault to the south western eliki fault suggests that slip was transferred rapidly but not homogeneously between the two faults during the period of contemporaneous activity together with a lack of evidence of lateral propagation at the eastern fault tip in the last 10 13 k y we suggest that the fault developed and established its current length rapidly within its 200 300 k y history these results contribute to our understanding of the process of northward fault migration into the rift and the development of new normal faults

osl dating of landslide dammed lake deposits in the north of tehran iran 958 ray taleghan ruyan earthquake abstract one large landslide soleghan in the north of the megacity tehran has been surveyed for dating with osl methods landslide dammed lake deposits of the soleghan landslide was used to obtain the age of the landslide event using the sar protocol for both quartz and feldspar grains the age of the event was 1 09 0 09 ka for quartz and 1 03 0 08 ka and 1 10 0 13 ka for feldspars stimulation at 50 c and 225 c respectively these results suggest that the soleghan mass movement was an earthquake induced landslide triggered by the 23rd february 958 7 7 m ray taleghan ruyan earthquake based on this work thorough review studies of landslides using osl dating methods can be used to determine the age of other mass movements in iran multiple landslides with identical ages which may be attributed to a seismic event could be created by a known earthquake or an unknown earthquake subsequently finding an unknown earthquake will complete the earthquake catalogue resulting in a better hazard assessment

contribution of archaeological data to studies of earthquake history in the iranian plateau we use archaeological evidence to identify ancient earthquakes in the vicinity of large 20th century events in the iranian plateau two large earthquakes on the zagros main recent fault were preceded by historical earthquakes in ad 1008 and ad 1107 and by earthquakes in the intervals ad 224 459 and 1650 1600 bc giving return times of 1800 2100 500 800 and 850 950 years the ad 1962 ms 7 2 bo in zahra earthquake on the ipak fault in north central iran was preceded by an earthquake in 2000 1500 bc recorded at the sagzabad mound a return time of 3500 4000 years if there are no missing events the ad 1990 ms 7 3 rudbar tarom earthquake in the western alborz mountains was preceded by an earthquake in 1000 800 bc recorded at the marlik mound a return time of 2800 3000 years the ad 1948 ms 7 2 kopeh dagh earthquake that destroyed ashkabad capital of turkmenistan was preceded by an earthquake in 10 bc ad 10 recorded at mithradatkert nesa mound and by an earthquake in 2000 bc recorded at ak tapeh mound assuming no missing earthquakes this region has an earthquake return time of about 2000 years in khorasan province which was struck by a sequence of large earthquakes from ad 1936 to 1997 a mosque at qa en was destroyed in the mid 11th century ad probably the historical earthquake of ad1066 in the absence of palaeoseismic investigations archaeology offers the promise of recording earthquakes through more than one seismic cycle in different regions of iran q 2001 elsevier science ltd all rights reserved

vapor phase exsolution as a controlling factor in hydrogen isotope variation in granitic rocks the notch peak granitic stock utah abstract the notch peak granitic stock western utah is comprised of three concentric sequentially intruded rock types from granite at the rim to quartz monzonite i to quartz monzonite ii at the core the 18 o values of whole rocks vary about an average of 9 4 smow irrespective of the rock type and position relative to contact suggesting that the three magmas had the same parent the whole rock d values in the stock range from 100 to 55 d values increase toward the cores of both quartz monzonite i and quartz monzonite ii resulting in concentric contours the d contours of quartz monzonite ii cross cut those of quartz monzonite i suggesting little isotopic interaction between these bodies and the absence of a late pervasive fluid phase there is a positive correlation between d values and water content of the samples where samples from each body define a distinct field the positive correlation is explained by isotopic fractionation attendant on vapor exsolution from the crystallizing magma an observed increase in d with the degree of chloritization a trend opposite to that observed in systems where participation of meteoric water has been demonstrated is the result of subsolidus interaction with the exsolved fluids these results show that large variations in the hydrogen isotope ratios of a granitoid can arise by exsolution of a vapor phase from the melt on crystallization in general magmas with larger modal amount of primary hydrous phases will tend to have higher d values than those with small amounts of hydrous phases furthermore the relatively high d values of chlorites at notch peak confirm the applicability of classical concepts of closed system deuteric alteration to some granitoid bodies thus meteoric water interaction need not be always invoked to explain hydrogen isotope variation and deuteric alteration in granitoids

exploratory models of long term crustal flow and resulting seismicity across the alpine aegean orogen 1 long term crustal flow is computed with a kinematic finite element model based on iterated weighted least squares fits to data and prior constraints data include 773 fault traces 106 fault offset rates 510 geodetic velocities 2566 principal stress azimuths and velocity boundary conditions representing the rigid parts of the eurasia africa and anatolia plates model predictions include long term velocities fault slip rates and distributed permanent strain rates between faults one model assumes that geodetic velocities measured adjacent to the aegean trench reflect a temporarily locked subduction zone in this case long term subduction velocity averages 45 mm yr and rapid crustal extension is predicted in the southern aegean sea another model assumes steady creeping subduction in this case subduction velocity averages only 29 mm yr and the eastern aegean seafloor is predicted to be more nearly rigid long term seismicity maps are computed for each model on the basis of the shift hypotheses and previous global calibrations of plate boundary earthquake production retrospective comparisons to seismic catalogs are encouraging map patterns spatial distribution functions and total earthquake counts are all comparable while neither model accurately predicts earthquake rates at all magnitudes the creeping subduction model is more accurate for strong m6 events which dominate the seismic hazard

assessment of grid based whole rock δd surveys in exploration boulder county epithermal tungsten deposit colorado important epithermal tungsten mineralization in the boulder county district is mainly hosted by quartz ferberite fewo4 veins isotopic studies based on an extensive grid deltad and individual samples of wall rock alteration and mineralization deltad deltao have demonstrated the dominance of meteoric fluids during alteration processes however the involvement of magmatic fluids during the deposition of the ferberite veins cannot be ruled out the fluids responsible for alteration exchanged with the country rocks to produce a large deltad anomaly but no concomitant delta o 18 anomaly indicating that water rock ratios were small the deltad anomaly coincides closely with those produced by h2o and rb sz used as a proxy for hydrothermal alteration but does not correlate closely with either lithochemical w anomalies or areas of greatest w production it is concluded that the fluids responsible for district wide hydrothermal alteration are distinct from those that produced the w mineralization and that ed anomalies while a sensitive technique for highlighting areas of significant fluid rock interact ion must be used with caution for identifying drilling targets the study has provided an estimate of the stable isotope composition of early tertiary meteoric water in the front range ca deltad 140 deltao 18 7

rapakivi granites south greenland hydrothermal alteration of igneous layering igneous layering is developed in the proterozoic rapakivi granite suite of south greenland in an area on the south easternmost coast of the island of angnikitsoq the layering at this locality is unusual in that it is defined by interstitial phases we suggest that large scale hydrothermal alteration has converted a fine grained pyroxene cumulate in which original cumulate pyroxenes occurred in the interstices between larger feldspars to interstitial biotite and green amphibole

the rapakivi granites of south greenland stable isotope characteristics of their black and white facies and the nature of their protolith abstract the rapakivi granites of south greenland were emplaced into the ketilidian orogenic belt at about 1 74 ga during an episode of extensional tectonics petrographically they can be subdivided into a roughly subequal black facies and white facies distinguished by the colour turbidity of the alkali feldspars and by the associated mineralogy which is more hydrous i e amphibole and biotite compared to olivine and pyroxene in the white facies the oxygen isotope composition of these rocks is notably homogeneous from thirteen outcrops sampled over an area extending some 200 km 100 km all alkali feldspars have an average 18 o of 10 2 0 4 this lack of variation is consistent with the consensus petrogenetic model which invokes a very well mixed two component protolith the high abundance of 18 o mean whole rock 18 o 9 4 argues that the major contribution perhaps 90 although originally mantle derived had undergone 18 o enrichment in a low temperature sedimentary cycle there is no oxygen isotopic distinction between alkali feldspars in the black and white facies which is argued to be a consequence of the relatively anhydrous nature of the melt hydrogen isotope compositions vary widely by 30 but are coherent on a hand specimen scale as demonstrated by approximately equal d of biotite and alkali feldspar it is not clear at which stage the d h heterogeneity was introduced

oxygen isotope fractionation in quartz albite anorthite and calcite laboratory measurements of equilibrium oxygen isotope fractionation in quartz albite anorthite and calcite have been carried out by anhydrous exchange between silicates and calcite at temperatures of 600 c and above exchange in these systems is as rapid as exchange between silicates and water fractionation factors can be summarized in the following equations qc 0 38 106t 2 abc 0 57 106t 2 anc 1 59 106t 2 from which the silicate pair fractionations are readily obtained these results are compared with published theoretical estimates as well as data derived from hydrothermal experiments some significant differences are found in particular it is difficult to reconcile all of the hydrothermal data either with theoretical calculations or with the present experimental data the new experiments provide an internally consistent set of fractionation factors suitable for isotopic thermometry and for test of disequilibrium in natural systems

dating past earthquakes and related sediments by thermoluminescence methods a review abstract applications of luminescence dating of geological materials have undergone extensive development and refinement since 1986 when mccalpin first attempted to date faults using thermoluminescence tl today luminescence methods offer high potential for dating paleoearthquakes and coseismic and post seismic deformation features over timescales ranging from 102 to 106 a while luminescence approaches generally do not possess the precision obtained by for example 40ar 39ar and 14c methods they offer a useful alternative approach with advantages in terms of age range and scope of material although the application of luminescence dating has in some cases been successfully described a comprehensive study outlining and defining protocols for routine luminescence methods to paleoseismology and neotectonic studies has not been forthcoming this review surveys previous attempts to apply tl techniques to paleoseismology and determination of the age of sediments associated with seismic events however while the use of tl has been a great success the wide application of tl has been hampered by the problem of daylight signal resetting

textural evolution of the rapakivi granites south greenland sr o and h isotopic investigations the development of rapakivi texture in feldspars from the ketilidian granitoids of south greenland has been investigated using sr o and h isotopes a low temperature signature is found in the sr and o data which seemingly contradicts some textural features that point to a magmatic origin of the plagioclase mantles around the k feldspar ovoids an origin for these mantles involving exsolution from an original alkali feldspar solid solution is proposed which involves growth of mantles over a range of conditions determined by the mobility of the exsolving sodic feldspar this mobility may be enhanced at high temperatures in the presence of melts or increased fluid pressures and at lower temperatures by the processes responsible for the transformation of k feldspar to microcline rapakivi granites with both white and dark green feldspar occur in south greenland but show no major isotopic differences although the dark alkali feldspars contain significantly more fluid equivalent fluids in the white alkali feldspars may have escaped during plagioclase exsolution

an alternative model for the growth of faults conventional growth models suggest that faults become larger due to systematic increases in both maximum displacement and length we propose an alternative growth model where fault lengths are near constant from an early stage and growth is achieved mainly by increase in cumulative displacement the model reconciles the scaling properties of faults and earthquakes and predicts a progressive increase in fault displacement to length ratios as a fault system matures this growth scheme is directly applicable to reactivated fault systems in which fault lengths were inherited from underlying structure and established rapidly the model may also apply to some non reactivated fault systems near constant fault lengths during subsequent growth are attributed to retardation of lateral propagation by interaction between fault tips the model is validated using kinematic constraints from growth strata which are displaced by a system of reactivated normal faults in the timor sea nw australia

the aigion neos erineos coastal normal fault system western corinth gulf rift greece geomorphological signature recent earthquake history and evolution 1 at the westernmost part of the corinth rift greece an area of rapid extension and active normal faulting geomorphological observations reveal the existence and geometry of an active nw se trending coastal fault system which includes the aigion fault we recognize a similar fault pattern on both the coastal range front to the nw of aigion town and the holocene fan deltas in front of it we interpret this as a result of recent migration of faulting to the hanging wall of the fault system differences in the geomorphic expression of the constituent faults provide hints on the possible evolution of the fault pattern during this recent migration a trench excavated across one of the identified coastal fault scarps on a holocene fan delta provides information on the seismic history of the fault system which includes at least four possibly six earthquakes in the past 4000 years a minimum estimate for the slip rate of the trenched fault is 1 9 2 7 mm yr the trench exposed sediments of an uplifted paleolagoon approximate age 2000 years b p inside which the last two earthquakes formed an underwater monoclinal scarp oscillating coastal vertical movements are suggested by the fact that the lagoonal deposits are also uplifted on the trenched fault hanging wall uplift by offshore faults and by the abrupt transition from fluvial to lagoonal deposits subsidence by more landward faults assuming that extensive coastal sediment failure has not taken place in the specific part of the fan delta within the time interval of interest these movements suggest that the proposed migration of activity from the range front faults to those on the fan deltas is probably still ongoing with activity on both sets of faults

a new mechanism of granite emplacement intrusion in active extensional shear zones one of the principal ways in which continental crust grows is by the incorporation from deeper within the earth of large volumes of granitic magma a space problem exists1 as to how these magmas are accommodated in the crust traditionally two main emplacement mechanisms have been emphasized forceful intrusion whereby buoyancy driven magmas physically push the crust aside creating granitic diapirs and balloons and passive emplacement characterized by replacive mechanisms such as cauldron subsidence and stoping although more recent work2 3 has demonstrated that space for granites may be created within bends and offsets of large transcurrent faults the simple view of either forceful or passive still fails to account for the intrusive mechanisms of many granites here we report the discovery of a new igneous intrusion mechanism in the superbly exposed proterozoic continental crust of south greenland we have observed that rapakivi granite was intruded as large scale sheets along ductile extensional shear zones that were active during emplacement in such a process the space problem seems to be simply resolved

the specific case of the mid proterozoic rapakivi granites and associated suite within the context of the columbia supercontinent abstract rapakivi granites and the associated suite anorthosite mangerite and charnockite that developed during the mid proterozoic escape the global rules that control usual granitic magma formation about 40 points that characterise the proterozoic magmatism confirm the originality of the magmatism rapakivi granites developed without a global orogenic context within the supercontinent columbia the intrusions extend from the east european shield to the western us through fennoscandia greenland and labrador other occurrences in the amazonian shield australia or south china are less well documented they show no definite trend in age or chemistry that would explain large scale mantle plume effects a mantle upwelling of material is contradictory with the re assembly of a supercontinent because it occurred before this magmatic episode 1 9 1 8 ga at 1 7 ga the supercontinent columbia amalgamated with the collision of the yapavai and mazatzal provinces a model is suggested that takes into account the supercontinent re assembly defining a downwelling flow in the mantle that anchors the continent above it in contrast to a material flow heat is still delivered to the base of the continental lithosphere and is focused toward the juvenile suture zone the base of the crust must reach 1200 1300 c before producing anorthosite magmas under such a high temperature gradient lasting over a long time magmas are transferred toward the upper crust giving the thin 5 km and square shape 100 km that the intrusions presently have heat delivery is essentially conductive leading to long time spans for intrusions the presence of the supercontinent immobile over a descending cell poloidal mode of convection developed a tangential force toroidal mode of convection that partly split the continent through strike slip deformation due to plate rotation it developed progressively between 1 57 and 1 3 ga starting from fennoscandia and then passing to amazonia western us and labrador in a clockwise sense the associated rotation induced sinistral shear manifested by small scale shear zones and the orientation of late magmatic facies topaz bearing granites in each province the proterozoic magmatism appears to be unique because it requires a supercontinent with a zone of juvenile crust surrounded by older cratons the present moho still shows remnants of this process having bumpy undulations that may reach 22 km in amplitude over a distance of 200 km

optical dating of landslide dammed lake deposits in the upper yellow river qinghai tibetan plateau china abstract two large landslides dehenglong and suozi blocked the upper yellow river from longyang gorge to liujia gorge on the qinghai tibetan plateau this research is significant because no relevant chronologies for this landslide dammed lake had been reported twelve osl samples were collected from the lacustrine sediments of the landslide dammed lake deposited on both banks of the upper yellow river samples yielded similar ages of ca 80 ka the dehenglong landslide and suozi landslide are thus inferred to be triggered by ca 80 ka tectonic movements

emplacement of rapakivi granite and syenite by floor depression and roof uplift in the palaeoproterozoic ketilidian orogen south greenland in the palaeoproterozoic ketilidian orogen of south greenland tabular intrusions of the rapakivi granite suite exposed at graah fjelde lindenow fjord and qernertoq and a mesoproterozoic syenite of the gardar province exposed at paatusoq were emplaced by a combination of roof uplift and floor depression the strain associated with the emplacement of the intrusions mainly involved redistribution of mass vertically within the lithosphere space for the emplacement of the rapakivi plutons was not created during regional extension on low angle ductile shear zones as claimed by some previous workers and there is no evidence that emplacement of the intrusions coincided with extensional collapse of the orogen following crustal thickening the rapakivi granites post date peak metamorphism in the orogen by 35 46 ma and their contacts cross cut and clearly post date intense flat lying d1 d2 fabrics that formed by partitioning of deformation into arc normal and arc parallel components during oblique convergence