ground motion modeling of the 1906 san francisco earthquake part ii ground motion estimates for the 1906 earthquake and scenario events abstract we estimate the ground motions produced by the 1906 san francisco earthquake making use of the recently developed song et al 2008 source model that combines the available geodetic and seismic observations and recently constructed 3d geologic and seismic velocity models our estimates of the ground motions for the 1906 earthquake are consistent across five ground motion modeling groups employing different wave propagation codes and simulation domains the simulations successfully reproduce the main features of the boatwright and bundock 2005 shakemap but tend to over predict the intensity of shaking by 0 1 0 5 modified mercalli intensity mmi units velocity waveforms at sites throughout the san francisco bay area exhibit characteristics consistent with rupture directivity local geologic conditions e g sedimentary basins and the large size of the event e g durations of strong shaking lasting tens of seconds we also compute ground motions for seven hypothetical scenarios rupturing the same extent of the northern san andreas fault considering three additional hypocenters and an additional random distribution of slip rupture directivity exerts the strongest influence on the variations in shaking although sedimentary basins do consistently contribute to the response in some locations such as santa rosa livermore and san jose these scenarios suggest that future large earthquakes on the northern san andreas fault may subject the current san francisco bay urban area to stronger shaking than a repeat of the 1906 earthquake ruptures propagating southward towards san francisco appear to expose more of the urban area to a given intensity level than do ruptures propagating northward

plio quaternary kinematic development and paleostress pattern of the edremit basin western turkey abstract the edremit basin and kazdag high are the most prominent morphological features of the biga peninsula in northwest anatolia there is still no consensus on the formation of edremit basin and debates are on whether the basin evolved through a normal a right lateral or a left lateral strike slip faulting in this study the geometric structural and kinematic characteristics of the edremit basin are investigated to make an analytical approach to this problem the structural and kinematic features of the faults in the region are described according to field observations these fault slip data derived from the fault planes were analyzed to determine the paleostress pattern of faulting in the region according to the performed analysis the southern end of the biga peninsula is under the influence of the ene wsw trending faults of the region such as the yenice gonen the edremit the pazarkoy and the havran balikesir fault zones the right step over geometry and related extension caused to the development of the edremit basin as a transtensional pull apart basin between the havran balikesir fault zone and the edremit fault zone field observations showed that the plio quaternary faults at the edremit gulf and adjacent areas are prominently right lateral strike slip faults our paleostress analyses suggest a dominant ne sw extension in the study area as well as nw se direction this pattern indicates the major effects of the north anatolian fault system and the component of aegean extensional system in the region however our kinematic analysis represents the dominant signature of the north anatolian fault system in basin bounding faults the field observations and kinematic findings of this study are also consistent with the regional gps paleomagnetic and seismological data this study concludes that the north anatolian fault system is the prominent structure in the current morphotectonic framework of the edremit gulf and adjacent areas

basin structure influences on the propagation of teleseismic waves in the santa clara valley california we have investigated ground motion amplification in the santa clara valley scv using teleseismic p waves observed during the 1998 deployment of 41 short period seismometers the santa clara valley seismic experiment scvse lindh et al 1999 fletcher et al 2003 recorded many local and regional earthquakes and seven large m w 6 4 teleseisms measured teleseismic p wave arrival time delays relative p wave amplification and p wave energy were used in the analysis the relative p wave amplification is found to correlate strongly with the arrival time delays in addition the p wave energy is found to correlate with the observed teleseismic delays we also compared observed p wave arrival time delays and p wave amplification with synthetics computed by using 3d finite difference simulations of the teleseismic wave field to model these parameters using both the university of california berkeley ucb stidham et al 1999 stidham 1999 and the u s geological survey usgs brocher et al 1997 jachens et al 1997 3d velocity models the results indicate that arrival time delays on the order of 0 25 sec correlate strongly with the reported basin depths in the two models we find that the correlation between the arrival time delays and basin depth is strongest for the usgs model however the ucb velocity model yields wave amplification that better matches the data the finite difference simulations indicate that in general the observations may be reproduced by either of the 3d velocity models although refinements to the proposed 3d structure for the scv are needed

the effect of sparse vegetation on the transport of dune sand by wind the precise effect of a sparse plant cover on the transport of dune sand by wind is a critical factor in understanding the morphology evolution and global distribution of aeolian dunes1 3 it is also of considerable practical importance in sand stabilization rehabilitation and restoration ecology here i report the first detailed experimental quantification of this effect using living plants in patterns approximating natural vegetation for wind velocities v at 0 5 m elevation up to 15 m s 1 and plant covercup to 17 the rate of aeolian sand transport q g cm 1 s 1 is closely approximated by q b v 1 kc vt 3 where b is bagnold s constant4 vt is a threshold velocity and k is a constant dependent on plant geometry for typical small erect or spreading herbaceous dune plants k 0 018 for small rounded stemless plants k 0 046

effect of shifting sand burial on soil evaporation and moisture salt distribution in a hyper arid desert it is a serious threat for the sustainable protection of the taklimakan desert highway shelterbelt tdhs from shifting sand burial to explore the effects of shifting sand burial on soil evaporation salt accumulation and their distribution micro lysimeters were used under sand burial of different thickness 1 3 and 5 cm and particle size 0 063 0 063 0 20 and 0 20 2 00 mm the results demonstrated that 1 soil daily evaporation and accumulative evaporation decreased with the sand burial thickness and thus evaporative inhibiting efficiency increased consequently the soil water content increased with sand burial thickness 1 48 12 70 than the control 2 finer textured 0 063 mm sand burial 0 2 cm depth promoted soil evaporation and salt accumulation at topsoil accumulative evaporation increased 5 1 mm and electrical conductivity ec of topsoil increased 13 30 ds m 1 compared with the control and 3 while topsoil ec decreased 1 65 6 46 ds m 1 with the increase in sand burial thickness soil ec beneath the sand burial interface showed a reverse trend we concluded that shifting sand burial has obvious effects on soil water evaporation salt accumulation and water salt redistribution and it could be considered to save water and reduce salt accumulation in arid desert areas like the tdhs with saline irrigation

contribution of radar interferometry to a two step inversion of the kinematic process of the 1992 landers earthquake we study the rupture process of the 1992 landers earthquake to limit the trade off between slip amplitude and rupture time that affects solutions using only seismological data we adopt a two step approach we first constrain the slip distribution and its uncertainty by independent geodetic data to recover in the second step the temporal details of the rupture propagation the first step consists of an inversion of interferometric data and global positioning system measurements both independently and together to constrain slip distribution on a three segment fault model along both strike and dip direction we use a genetic algorithm to test the uniqueness of the solution and a least squares formulation to find the model which best fits the data we conclude from the results of these geodetic inversions that interferometric data are rich enough to access the slip distribution in the case of the landers earthquake since the surface deformations are more sensitive to shallow slip in our configuration the slip amplitude is better resolved near the surface than at depth the resulting slip distribution is in agreement with geological observations at the surface and confirms the heterogeneous nature of the landers earthquake most of the slip occurs at shallow depths on the homestead valley fault second segment with a maximum value of around 7 m another high slip zone is observed on the johnson valley fault first segment at 8 km depth in the second step we invert strong motion data with the a priori final slip amplitude and its uncertainty deduced from geodetic data to constrain the time history of the rupture process this second step emphasizes a strong variation of the temporal development of the earthquake fast rupture front velocities appear within high slip zones and the rupture slows when it encounters a resistance along the fault on average the rupture front propagates with velocities close to the s wave velocity and terminates about 20 s after initiation the large variations in both slip amplitude and rupture velocity suggest that the rupture process is better described by successively breaking asperities than by a pulse propagating with constant velocity

comparison of young volcanic associations of western and eastern anatolia formed under a compressional regime a review abstract turkey is characterised by widespread post oligocene volcanism in western anatolia volcanic activity began during the late oligocene early miocene in a compressional regime a widespread suite of andesitic and dacitic calc alkaline rocks was erupted in this period they were accompanied by locally developed high level granitic intrusions the abrupt change from n s compression to n s stretching in the middle miocene was accompanied by a gradual transition to alkali basaltic volcanism in eastern anatolia the collision related compressional tectonics and associated volcanic activity began in the late miocene to pliocene and continued almost without interruption into historical times one minor and two major volcanic phases may be distinguished an initial minor eruptive phase of basic and intermediate alkaline rocks was followed by widespread eruptions of andesitic and dacitic calc alkaline rocks during the pliocene partly penecontemporaneous with this a second more important major phase of volcanism involving alkaline and transitional lavas began and continued during the quaternary the calc alkaline lavas of both regions were erupted at a time when the compressional regime led to crustal thickening these lavas display many geochemical and isotopic signatures that may be interpreted in terms of contamination of magma involving continental crustal materials the alkaline lavas in both regions began during the final stage of the compressional regime and form two groups one group is geochemically and isotopically similar to the calc alkaline rocks and the other is more typically alkaline the volcanic evolution of these two regions of turkey followed a somewhat similar pattern producing highly contaminated calc alkaline lavas at the beginning and evolving towards uncontaminated alkaline lavas at the end

simulated ground motion in santa clara valley california and vicinity from m 6 7 scenario earthquakes abstract models of the santa clara valley scv 3d velocity structure and 3d finite difference software are used to predict ground motions from scenario earthquakes on the san andreas saf monte vista shannon south hayward and calaveras faults twenty different scenario ruptures are considered that explore different source models with alternative hypocenters fault dimensions and rupture velocities and three different velocity models ground motion from the full wave field up to 1 hz is exhibited as maps of peak horizontal velocity and pseudospectral acceleration at periods of 1 3 and 5 sec basin edge effects and amplification in sedimentary basins of the scv are observed that exhibit effects from shallow sediments with relatively low shear wave velocity 330 m sec scenario earthquakes have been simulated for events with the following magnitudes 1 m 6 8 7 4 calaveras sources 2 m 6 7 6 9 south hayward sources 3 m 6 7 monte vista shannon sources and 4 m 7 1 7 2 peninsula segment of the saf sources ground motions are strongly influenced by source parameters such as rupture velocity rise time maximum depth of rupture hypocenter and source directivity cenozoic basins also exert a strong influence on ground motion for example the evergreen basin on the northeastern side of the scv is especially responsive to 3 5 sec energy from most scenario earthquakes the cupertino basin on the southwestern edge of the scv tends to be highly excited by many peninsula and monte vista fault scenarios sites over the interior of the evergreen basin can have long duration coda that reflect the trapping of seismic energy within this basin plausible scenarios produce predominantly 5 sec wave trains with greater than 30 cm sec sustained ground motion amplitude with greater than 30 sec duration within the evergreen basin

distribution of aseismic slip rate on the hayward fault inferred from seismic and geodetic data 1 we solve for the slip rate distribution on the hayward fault by performing a least squares inversion of geodetic and seismic data sets our analysis focuses on the northern 60 km of the fault interferometric synthetic aperture radar insar data from 13 independent ers interferograms are stacked to obtain range change rates from 1992 to 2000 horizontal surface displacement rates at 141 bench marks are measured using gps from 1994 to 2003 surface creep observations and estimates of deep slip rates determined from characteristic repeating earthquake sequences are also incorporated in the inversion the fault is discretized into 283 triangular dislocation elements that approximate the nonplanar attributes of the fault surface south of the city of hayward a steeply east dipping fault geometry accommodates the divergence of the surface trace and the microseismicity at depth the inferred slip rate distribution is consistent with a fault that creeps aseismically at a rate of 5 mm yr to a depth of 4 6 km the interferometric synthetic aperture radar insar data require an aseismic slip rate that approaches the geologic slip rate on the northernmost fault segment beneath point pinole although the insar data might be complicated by a small dip slip component at this location a low slip rate patch of 1 mm yr is inferred beneath san leandro consistent with the source location of the 1868 earthquake we calculate that the entire fault is accumulating a slip rate deficit equivalent to a mw 6 77 0 05 per century however this estimate of potential coseismic moment represents an upper bound because we do not know how much of the accumulated strain will be released through aseismic processes such as afterslip

evolution of the triassic continental margin northwest anatolia abstract the northwest anatolian basement consists of two distinctly different metamorphic assemblages which were juxtaposed prior to the deposition of liassic cover sediments these include the lower and the upper associations the lower association is mainly represented by triassic metavolcanic and associated metasedimentary units together with a slice of ophiolite the upper association rests on the lower association with a low angle thrust fault and is composed of paleozoic or older schists gneisses and phyllites a transgressive succession begins above the basement with permo carboniferous neritic limestones these platform type carbonates were disrupted by rifting during the early triassic at the initial phase of rifting coarse clastics and associated rift type lavas were formed the rift then evolved into an ocean basin which closed at the end of the triassic the continental margin of the triassic basin underwent regional metamorphism initially high t low p it was followed later by a high p low t metamorphic phase during the metamorphism the continental margin units were multiply deformed by north directed compressive stress later on unmetamorphosed triassic successions of the continental margin were thrust northward onto the metamorphosed part of the same continental margin thus the triassic assemblages of northwest anatolia collectively display the dynamics and various structural affects of the deformation recorded in the continental margin and adjacent oceanic unit

a new model of wind erosion in the presence of vegetation 1 vegetation is known to impact strongly the erosion of soil by the wind lateral cover is the primary parameter used to represent the amount of vegetation in aeolian research and in particular shear stress partitioning research although lateral cover provides a simple means for representing how much vegetation is in an area it is not capable of characterizing how vegetation is distributed a new nonequilibrium model for the representation of nonerodible roughness elements is presented that uses the size distribution of erodible gaps between plants to characterize the ratio of the maximum shear stress to the average shear stress at the surface the model shows very good agreement with measured shear stress ratios from the laboratory and field experiments the model also satisfactorily explains relatively high horizontal aeolian sediment flux at high lateral cover the relationship between this model and another shear stress partitioning model is explored and the new model is found to be superior to the existing model because it 1 utilizes parameters with physical meaning that are measurable in the field or laboratory 2 explains observations of horizontal flux at high cover 3 overcomes difficulties inherent in the use of lateral cover to characterize vegetation on the surface 4 is scale explicit and 5 can be used at multiple scales from an individual unvegetated gap to an entire landscape

fault zone amplified waves as a possible seismic hazard along the calaveras fault in central california the calaveras fault lies within a low velocity zone lvz 1 2 km wide near gilroy california accelerographs g06 located in the lvz 1 2 km from the calaveras fault and g07 4 km from g06 recorded both the m 6 2 1984 morgan hill and the m 6 9 1989 loma prieta earthquakes comparison of the ground motions shows that a large 0 6 1 0 hz velocity pulse observed at g06 during the morgan hill event may be amplified by focussing caused by the lvz such amplified waves might be a mappable seismic hazard and the zone of increased hazard can extend as much as 1 2 km from the surface trace of the fault finite difference simulations of ground motions in a simplified lvz model show a zone of amplified motion similar to the observations

geological evolution of the late mesozoic continental margin of northwestern anatolia abstract the armutlu peninsula is a composite tectonic entity made up of sections of the sakarya continent the rhodope pontide fragment and an ophiolite these were assembled following a continental collision between gondwanaland and laurasia during the late cretaceous the northern margin of the sakarya continent underwent progressively increasing deformation prior to and during the advancing collision due to continued convergence between the two continents initially the leading edge of the continent subsided under the load of an approaching ophiolitic slab following this a north directed thrusting and folding occurred during the turonian progressive elimination and eventual closure of the ocean preceded the thrusting of northerly situated collisiondashinduced nappe packages over the leading edge of the sakarya continent the nappe laden edge of the continental margin then collapsed and steadily subsided under the heavy load of the ophiolitic slab and the northern continental fragment consequently the nappe packages and the ophiolite were collectively metamorphosed during the coniaciandashsantonian interval during the subsidence the main body of the sakarya continent partially detached from its collapsed edge along a fault zone and thus suffered an independent but less severe deformation which lasted until the uplift of the collapsed edge in the campanian from the late campanian onward throughout later orogenic stages the metamorphic and nondashmetamorphic units amalgamated into a single tectonic entity forming a basement for younger cover rocks

u pb zircon geochronology of the paleogene neogene volcanism in the nw anatolia its implications for the late mesozoic cenozoic geodynamic evolution of the aegean abstract the northern aegean region was shaped by subduction obduction collision and post collisional extension processes two areas in this region the rhodope thrace biga peninsula to the west and armutlu almacik nallihan the central sakarya to the east are characterized by extensive eocene to miocene post collisional magmatic associations we suggest that comparison of the cenozoic magmatic events of these two regions may provide insights into the late mesozoic to cenozoic tectonic evolution of the aegean with this aim we present an improved cenozoic stratigraphy of the biga peninsula derived from a new comprehensive set of u pb zircon age data obtained from the eocene to miocene volcanic units in the region the compiled radiometric age data show that calc alkaline volcanic activity occurred at 43 15 ma in the biga peninsula 43 17 ma in the rhodope and thrace regions and 53 38 ma in the armutlu almacik nallihan region which are slightly overlapping we discuss the possible cause for the distinct cenozoic geodynamic evolution of the eastern and western parts of the region and propose that the rhodope thrace and biga regions in the north aegean share the same late mesozoic to cenozoic geodynamic evolution which is consistent with continuous subduction crustal accretion southwestward trench migration and accompanying extension all preceded by the late cretaceous paleocene collision along the vardar suture zone in contrast the armutlu almacik nallihan region was shaped by slab break off and related processes following the late cretaceous paleocene collision along the izmir ankara suture zone the eastern and western parts of the region are presently separated by a northeast southwest trending transfer zone that was likely originally present as a transform fault in the subducted tethys oceanic crust and demonstrates that the regional geodynamic evolution can be strongly influenced by the geographical distribution of geologic features on the subducting plate

site response shallow shear wave velocity and wave propagation at the san jose california dense seismic array ground motion records from a 52 element dense seismic array near san jose california are analyzed to obtain site response shallow shear wave velocity and plane wave propagation characteristics the array located on the eastern side of the santa clara valley south of the san francisco bay is sited over the evergreen basin a 7 km deep depression with miocene and younger deposits site response values below 4 hz are up to a factor of 2 greater when larger regional records are included in the analysis due to strong surface wave development within the santa clara valley the pattern of site amplification is the same however with local or regional events site amplification increases away from the eastern edge of the santa clara valley reaching a maximum over the western edge of the evergreen basin where the pre cenozoic basement shallows rapidly amplification then decreases further to the west this pattern may be caused by lower shallow shear wave velocities and thicker quaternary deposits further from the edge of the santa clara valley and generation trapping of surface waves above the shallowing basement of the western evergreen basin shear wave velocities from the inversion of site response spectra based on smaller local earthquakes compare well with those obtained independently from our seismic reflection refraction measurements velocities from the inversion of site spectra that include larger regional records do not compare well with these measurements a mix of local and regional events however is appropriate for determination of site response to be used in seismic hazard evaluation since large damaging events would excite both body and surface waves with a wide range in ray parameters frequency wavenumber plane wave analysis is used to determine the backazimuth and apparent velocity of coherent phases at the array conventional high resolution and multiple signal characterization f k power spectra and stacked slowness power spectra are compared these spectra show surface waves generated scattered at the edges of the santa clara valley and possibly within the valley at the western edge of the evergreen basin

rupture process of the 1987 superstition hills earthquake from the inversion of strong motion data a pair of significant earthquakes occurred on conjugate faults in the western imperial valley involving the through going superstition hills fault and the elmore ranch cross fault the first event was located on the elmore ranch fault m s 6 2 and the larger event on the superstition hills fault m s 6 6 the latter event is seen as a doublet teleseismically with the amplitudes in the ratio of 1 2 and delayed by about 8 sec this 8 sec delay is also seen in about a dozen strong motion records these strong motion records are used in a constrained least squares inversion scheme to determine the distribution of slip on a 2 d fault upon closer examination the first of the doublets was found to be itself complex requiring two episodes of slip thus the rupture model was allowed to have three separate subevents treated as separate ruptures with independent locations and start times the best fits were obtained when all three events initiated at the northwestern end of the fault near the intersection of the cross fault their respective delays are 2 1 and 8 6 sec relative to the first subevent and their moments are 0 4 0 9 and 3 5 10 25 dyne cm which is about half of that seen teleseismically this slip distribution suggests multi rupturing of a single asperity with stress drops of 60 200 and 15 bars respectively the first two subevents were confined to a small area around the epicenter while the third propagated 18 km southwestward compatible with the teleseismic and afterslip observations

nebkha flow dynamics and shadow dune formation in this study wind flow is simulated via cfd over five nebkha dune forms that range in shape from a cone to a hemisphere approximately and to a dome in order to examine the structure of the wake zone formed downwind and the effect on the leeward flow separation zone and shadow dune formation dune height was fixed at 0 5 m while the nebkha diameter increased in 0 25 m increments from 0 5 m to 1 5 m and aspect ratio h d from 1 0 to 0 3 the mean flow comprises an upwind region of reduced velocity which expands as nebkha width increases high velocity marginal wings and paired counter rotating reversing vortices leeward of the nebkha the point at which flow separation occurs moves further downwind as the nebkha diameter increases the core regions of the reversing vortices are situated further downwind behind the smaller nebkha than in the case of the larger nebkha these factors in combination allow for higher velocity perturbations tke and narrower wake behind the smaller nebkha and the suppression of downwind wake development in the case of the increasingly larger nebkha shadow dune length increases as nebkha width increases for lower incident velocity flow and is barely affected by nebkha width at higher flows the extent of the leeward separation or wake zone and hence shadow dune length more strongly varies as a function of wind velocity

estimation of q for long period 2 sec waves in the los angeles basin we simulate 0 to 0 5 hz 3d wave propagation through the southern california earthquake center seismic velocity reference model version 2 for the 1994 northridge earthquake in order to examine the effects of anelastic attenuation and amplification within the near surface sediments we use a fourth order finite difference staggered grid method with the coarse grained frequency independent anelastic scheme of day and bradley 2001 and a variable slip distribution from kinematic inversion for the northridge earthquake we find that the near surface material with s wave velocity v s as low as 500 m sec significantly affects the long period peak ground velocities compared with simulations in which the s wave velocity is constrained to 1 km sec and greater anelastic attenuation also has a strong effect on ground motion amplitudes reducing the predicted peak velocity by a factor of up to 2 5 relative to lossless simulations our preferred q model is q s v s 0 02 v s in meters per second for v s less than 1 2 km sec and much larger q s v s 0 1 v s in meters per second for layers with higher velocities the simple model reduces the standard deviation of the residuals between synthetic and observed natural log of peak velocity from 1 13 to 0 26 relative to simulations for the lossless case the anelastic losses have their largest effect on short period surface waves propagating in the los angeles basin which are principally sensitive to q s in the low velocity near surface sediments of the basin the low frequency ground motion simulated here is relatively insensitive to q p as well as to the values of q s at depths greater than roughly that of the 2 km sec s wave velocity isosurface

geology geochemistry and geochronology of fe oxide cu au mineralization associated with şamli pluton western turkey abstract the amli balikesir fe oxide cu au deposit one of several iron cu au deposits in western turkey is hosted by porphyritic rocks of the multi phase amli pluton and metapelitic metadiabasic rocks of karakaya complex two successive mineralization events are recognized in the area as i early magnetite and sulfide and ii late hematite goethite native copper au alteration associated with the mineralization in amli is characterized by four distinct mineralogical assemblages they are in chronological order of formation 1 plagioclase early pyroxene scapolite 2 garnet late pyroxene 3 chlorite epidote and 4 chalcedony calcite alteration geochemical isotopic sr nd o s and geochronological ar ar data from alteration and magmatic rocks suggest a temporal and genetic link between the multiphase amli pluton and the hydrothermal system that controls the fe oxide cu au mineralization 40 ar 39 ar geochronology on hornblende and biotite separates of the amli pluton yielded an age range between 23 20 0 50 and 22 42 0 11 ma overlapping with 40 ar 39 ar age of 22 34 0 59 ma from alteration the close spatial and temporal associations of amli mineralization with porphyritic intrusions pervasive ca rich alteration calcic plagioclase andraditic garnet diopsidic pyroxene scapolite and epidote are considered as common features akin to calcic assemblages in typical iocg deposits besides abundant low ti 0 5 magnetite hematite high cu moderate au up to 8 82 ppm association structural control and lithologic controls of mineralization low s sulfide content chalcopyrite pyrite in the deposit and the derivation of causative magma from subduction modified subcontinental lithospheric mantle under a transpressional to transtensional regime are collectively considered as the features in favor of iocg type mineralization for the amli deposit

petrogenesis of collision related plutonics in central anatolia turkey central anatolia exhibits good examples of calc alkaline and alkaline magmatism of similar age in a collision related tectonic setting continent island arc collision in the central anatolia region late cretaceous post collisional plutonic rocks intrude palaeozoic mesozoic metamorphic rocks overthrust by upper cretaceous ophiolitic units to make up the central anatolian crystalline complex in the complex three different intrusive rock types may be recognised based on their geochemical characteristics i calc alkaline behrekdag cefalikdag and celebi ii subalkaline transitional baranadag and ii alkaline hamit the calc alkaline and subalkaline plutonic rocks are metaluminous i type plutons ranging from monzodiorite to granite the alkaline plutonic rocks are metaluminous to peralkaline plutons predominantly a type ranging from nepheline monzosyenite to quartz syenite all intrusive rocks show enrichment in lile and lree relative to hfse and have high 87sr 86sr and low 143nd 144nd ratios these characteristics indicate an enriched mantle source region s carrying a subduction component inherited from pre collision subduction events the tectonic discrimination diagram of rb vs y nb suggests that the calc alkaline subalkaline and alkaline plutonic rocks have been affected by crustal assimilation combined with fractional crystallisation processes the coexistence of calc alkaline and alkaline magmatism in the central anatolian crystalline complex may be attributed to mantle source heterogeneity before collision the former carries a smaller intraplate component and pre subduction enrichment compared to the latter either thermal perturbation of the metasomatised lithosphere by delamination of the thermal boundary layer tbl or removal of a subducted plate slab breakoff is the likely mechanism for the initiation of the post collisional magmatism in the complex

an exact solution for effects of topography on free rayleigh waves an exact solution for the effects of topography on rayleigh wave amplification is presented the solution is obtained by incorporating conformal mapping into complex variable stress functions developed for free rayleigh wave propagation in an elastic half space with a flat upper surface results are presented for free rayleigh wave propagation across isolated symmetric ridges and valleys it is found for wavelengths that are comparable to ridge widths that horizontal rayleigh wave amplitudes are amplified at ridge crests and that vertical amplitudes are strongly reduced near ridge crests relative to horizontal and vertical amplitudes of free rayleigh waves in the flat case horizontal amplitudes are strongly deamplified at valley bottoms relative to those for the flat case for rayleigh wavelengths comparable to valley widths wave amplitudes in the symmetric ridges and valleys asymptotically approach those for the flat case with increased wavelengths increased ridge and valley widths and with horizontal distance from and depth below the isolated ridges and valleys also prograde particle motion is predicted near crests of narrow ridges and near the bottoms of narrow valleys finally application of the theory at two sites known for topographic wave amplification gives a predicted surface wave amplification ratio of 3 80 at the ridge center for a frequency of 1 0 hz at robinwood ridge in northern california and a predicted surface wave amplification ratio of 1 67 at the ridge center for the same frequency at the cedar hill nursery site at tarzana in southern california

seismic activity of the san francisco bay region moment magnitude m with objective confidence level uncertainties are estimated for felt san francisco bay region earthquakes using bakun and went worth s 1997 analysis strategy for seismic intensity observations the frequency magnitude distribution is well described for m 5 5 events since 1850 by a gutenberg richter relation with a b value of 0 90 the seismic moment rate m yr since 1836 is 2 68 1018 n m yr 95 confidence range 1 29 1018 n m yr to 4 07 1018 n m yr the seismic moment rate since 1850 is nearly the same m yr in the 56 years before 1906 is about 10 times that in the 70 years after 1906 in contrast m yr since 1977 is about equal that in the 56 years before 1906 80 1 14 of the plate motion moment accumulation rate is available for release in earthquakes the historical m yr and the portion of the plate motion moment accumulation rate available for release in earthquakes are used in a seismic cycle model to estimate the rate of seismic activity in the twenty first century high and low rates of future seismic activity are both permissible given the range of possible seismic cycle recurrence times t and the uncertainties in the historical m and in the percentage of plate motion available for release in earthquakes if the historical seismic moment rate is not greater than the estimated 2 68 1018 n m yr and the percentage of the plate motion moment accumulation available for release in earthquakes is not less than the estimated 80 then for all t the rate of seismic moment release from now until the next 1906 sized shock will be comparable to the rate from 1836 to 1905 when m 6 1 2 shocks occurred every 15 to 20 years

the blown sand flux over a sandy surface a wind tunnel investigation on the fetch effect abstract detailed wind tunnel tests were conducted to examine the fetch effect of a sandy surface on a sand cloud blowing over it the results suggest that the fetch length of a sandy surface has a significant effect on both the vertical flux profile and total horizontal flux the sand flux over a sandy surface increases with height in the very near surface layer but then decays exponentially in agreement with the widely accepted conclusion the decay function can be expressed by q aexp h b where q is the sand flux at height h coefficient a that tends to increase with wind speed implies the influence of wind while coefficient b that defines the relative decay rate shows the influence of both the fetch and wind the relative decay rate increases with fetch when the fetch length is short then becomes constant when the fetch reaches a certain length the threshold fetch length over which the relative decay rate keeps constant increases with wind speed the average saltation height generally increases with fetch both the relative decay rate and average saltation height show that the fetch effect on the flux profile becomes more significant when the wind speed increases the total sand transport equation for the total fetch can be expressed by q c 1 ut u 2u3 g where q is the total sand transport rate u and ut are the wind velocity and threshold wind velocity at the centerline height of the wind tunnel respectively g is gravitational acceleration is the density of air and c is a proportionality coefficient that increases with the fetch length implying that the total sand flux increases with the fetch length

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

petrochemistry of the south marmara granitoids northwest anatolia turkey post collision magmatic rocks are common in the southern portion of the marmara region kapidag karabiga gonen yenice can areas and also on the small islands marmara avsa pasalimani in the sea of marmara they are represented mainly by granitic plutons stocks and sills within triassic basement rocks the granitoids have ages between late cretaceous and miocene but mainly belong to two groups eocene in the north and miocene in the south the miocene granitoids have associated volcanic rocks the eocene granitoids do not display such associations they are both granodioritic and granitic in composition and are metaluminous calc alkaline medium to high k rocks their trace elements patterns are similar to both volcanic arc and calc alkaline post collision intrusions and the granitoids plot into the volcanic arc granite vag and collision related granite areas colg of discrimination diagrams the have high 87sr 86sr 0 704 0 707 and low 143nd 144nd 0 5124 0 5128 during their evolution the magma was affected by crustal assimilation and fractional crystallization afc nd and sr isotopic compositions support an origin of derivation by combined continental crustal afc from a basaltic parent magma a slab breakoff model is consistent with the evolution of south marmara sea granitoids

magma generation by slab steepening and breakoff beneath a subduction accretion complex an alternative model for collision related volcanism in eastern anatolia turkey 1 eastern anatolia is regarded as one of the best examples of continental collision represented by a 2 km high plateau it displays shallow and diffuse seismicity indicating that the crust is still being actively deformed perhaps the most striking aspect of eastern anatolia is the volume and compositional variability of collision related volcanic products erupted during the neogene and quaternary time a number of models have been proposed for the genesis of this volcanism in the region however recent geophysical studies have revealed that a mantle lithosphere is almost completely absent beneath a greater portion of the region which makes us question the validity of the previous models in this paper we propose a new model for magma genesis slab steepening and breakoff beneath a large subduction accretion complex this model holds that a northward subducting oceanic lithosphere beneath the eastern anatolia accretionary prism gets steepened and eventually detached from the continental lithosphere of the bitlis poturge massif following the continent accretionary complex collision this brings the asthenospheric mantle in contact with the accretionary complex at shallow depths e g around 50 km resulting in rapid regional uplift and extensive melting which leads to collisional volcanism

a spatial random field model to characterize complexity in earthquake slip 1 finite fault source inversions reveal the spatial complexity of earthquake slip over the fault plane we develop a stochastic characterization of earthquake slip complexity based on published finite source rupture models in which we model the distribution of slip as a spatial random field the model most consistent with the data follows a von karman autocorrelation function acf for which the correlation lengths a increase with source dimension for earthquakes with large fault aspect ratios we observe substantial differences of the correlation length in the along strike a x and downdip a z directions increasing correlation length with increasing magnitude can be understood using concepts of dynamic rupture propagation the power spectrum of the slip distribution can also be well described with a power law decay i e a fractal distribution in which the fractal dimension d remains scale invariant with a median value d 2 29 0 23 while the comer wave number k c which is inversely proportional to source size decreases with earthquake magnitude accounting for larger slip patches for large magnitude events our stochastic slip model can be used to generate realizations of scenario earthquakes for near source ground motion simulations

a record of large earthquakes on the southern hayward fault for the past 500 years the hayward fault a major branch of the right lateral san andreas fault system traverses the densely populated eastern san francisco bay region california we conducted a paleoseismic investigation to better understand the hayward fault9s past earthquake behavior the site is near the south end of tyson9s lagoon a sag pond formed in a right step of the fault in fremont because the hayward fault creeps at the surface we identified paleoseismic events using features that we judge to be unique to ground ruptures or the result of strong ground motion such as the presence of fault scarp colluvial deposits and liquefaction we correlate the most recent event evidence e1 to the historical 1868 m 6 9 earthquake that caused liquefaction in the pond and recognize three additional paleoruptures since a d 1470 110 yr event ages were estimated by chronological modeling which incorporated historical and stratigraphic information and radiocarbon and pollen data modeled mean age and 95 percentile ranges of the three earlier events are a d 1730 1650 1790 yr e2 a d 1630 1530 1740 yr e3 and a d 1470 1360 1580 e4 the ages of these paleoearthquakes yield a mean recurrence of 130 40 yr although the mean recurrence is well determined for the period a d 1470 1868 individual intervals are less well determined e1 e2 140 80 70 yr e2 e3 100 90 100 yr and e3 e4 150 130 110 yr

three dimensional structure influences on the strong motion wavefield of the 1989 loma prieta earthquake abstract the accurate calculation of ground motions for future large earthquakes depends on detailed knowledge of three dimensional 3d geologic structure and the earthquake source process as well as sufficient computational resources in this article we describe the results of finite difference simulations for the 1989 loma prieta ca earthquake with a 3d seismic velocity model for the san francisco bay region and a heterogeneous slip model of the source additionally we explore the sensitivity of the synthetics to the major geologic structures in the velocity model the san francisco bay region particularly the loma prieta region is a unique area for the study of 3d wave propagation because of the pronounced lateral velocity contrasts across the strike slip faults of the region understanding the effects of such long wavelength structure is doubly important when considering a source located close to such a contrast our simulations show that the lateral velocity contrast across the san andreas fault saf would be expected to substantially affect the propagation of elastic waves radiated from a source in the loma prieta region indeed we find that the refraction of energy by the saf serves to reduce ground motions at stations located along the san francisco peninsula and the quaternary and tertiary alluvial basins of the san francisco bay region are found to amplify and extend the duration of ground motions in santa clara valley livermore valley and san pablo bay we find that the 3d model as currently defined accurately describes the spatial variation of peak ground velocity for frequencies less than 0 5 hz which suggests that this model may be used to estimate ground motions for future earthquake scenarios

wind tunnel simulation of the three dimensional airflow patterns behind cuboid obstacles at different angles of wind incidence and their significance for the formation of sand shadows sand shadows commonly form downwind of obstacles in arid and semi arid regions understanding their dynamics requires insights into the airflow patterns behind the obstacles under different wind regimes here we studied models of cuboid obstacles to characterize the three dimensional responses of airflow behind obstacles with different shape ratios to variations in the incident flow in a wind tunnel simulation wind velocity was measured using particle image velocimetry piv the flow patterns behind cuboid obstacles were complicated by changes in the incidence angle of the approaching flow and in the obstacle s shape ratio the flows separated both horizontally and vertically creating reverse flow cells downwind of the obstacles the horizontal cells were characterized by two asymmetrical opposing reverse vortices at flow incidence angles greater than 60 to 65 whereas the vertical cells formed a single vortex at all angles the cells shifted position in response to changes in the incidence angle and shape ratio reflecting the interaction between outer and reverse flows the parameters of the horizontal and vertical reverse cells depended on the shape ratios and incidence angles but not on the wind velocity the sizes of the horizontal and vertical reverse cells were correlated reflecting their interactions the low velocity shadow behind the obstacle caused sand deposition and determined the sand shadow s evolution field experiments will be required to relate these airflow patterns to sand shadow development

dune sand transport as influenced by wind directions speed and frequencies in the ordos plateau china the ordos plateau in china is a region with extensive wind erosion severe desertification and various aeolian sand hazards in order to determine aeolian sand transport in this region the relationship between the sand transport rate and wind speed at 10 min frequencies was established by field observation in both the qubqi sand desert and the mu us sandy land threshold wind speeds 2 m above the ground for mobile semi fixed and fixed dune surfaces were estimated by field observations the sand transport rate increased with the increase of the bare land ratio and near bed wind speed high resolution meteorological 10 min average wind velocity data at 10 m above the ground were converted into velocity values at a height of 2 m to calculate sand transport potential based on three specific parameters decisive for sand transport wind speed duration and direction the quantity of aeolian sand transported was calculated for various wind speed levels and directions and the overall characteristics of sand transport on different dune surface types were determined by vector operation techniques sand transporting winds took place mainly in springtime the prevailing wind directions were w wnw and nw with a frequency of more than 60 in total and sand transport in these directions made up more than 70 of the total transport corresponding to a general southeastward encroachment of aeolian sand in the study area the relationship between wind frequency and speed can be expressed by a power function high magnitude strong winds had a low frequency but they played a dominant role in aeolian sand transport

post collisional adakite like magmatism in the agvanis massif and implications for the evolution of the eocene magmatism in the eastern pontides ne turkey abstract in the anatolia the caucasus and northwest iran the eocene epoch is characterized by widespread basic to acidic magmatism whose temporal and spatial evolutions and origin are poorly understood in this paper we provide geochronological and geochemical data on a suite of early eocene intrusions from northeast turkey and discuss their origin within a regional tectonic framework post to late collisional moderate to small bodies of quartz diorite and leucogranodiorite as well as later dacite porphyries intrude permo triassic low grade metamorphic rocks in the southern part of the eastern pontides very close to the neo tethyan izmir ankara erzincan suture in places the intrusives display well developed subsolidus foliations indicating on going penetrative deformation during and shortly after emplacement different emplacement depths were inferred based on the contact metamorphic mineral assemblages al in hornblende barometry and igneous textures quartz diorite 14 16 km vs dacitic porphyries 7 km biotite and hornblende ar ar and zircon u pb data indicate that the compositionally and texturally different intrusives were emplaced at 51 ma ypresian three lines of evidence indicate that the early eocene represents a tectonically active time with high exhumation rates 0 6 cm a 1 i the quartz diorite and dacitic porphyries were emplaced at different crustal depths ii the emplacement ages of these texturally distinct intrusive rocks are geochronologically undistinguishable and iii intrusive rocks locally show a well developed foliation the intrusive rocks display high abundances of al 2 o 3 sr ba lrees and low abundances of y sc and hrees and are similar to high silica adakites from supra subduction zone settings the geochemical features imply a residual and or fractionating assemblage rich in hornblende garnet pyroxene and poor in plagioclase all rock types display similar sr nd isotopic characteristics with initial e nd and 87 sr 86 sr values ranging from 1 0 to 1 1 and from 0 70421 to 0 70494 respectively these three coeval rock groups quartz diorite leucogranodiorite and dacite porphyries were generated from a similar source by variable degrees of partial melting and fractionation these data together with those from the literature clearly reveal that the adakitic signature is common in paleocene to early eocene igneous rocks in northern turkey on both sides of the izmir ankara erzincan suture but disappears towards the middle eocene regional geological constraints indicate that the continental collision between the pontides and the anatolide tauride block occurred in the paleocene and that the middle eocene represents a period of major extension characterized by a marine transgression we therefore suggest that the early eocene adakitic magmatism in northern turkey resulted from the presence of a thickened continental crust following the continental collision along the neo tethyan izmir ankara erzincan suture whereas the voluminous middle eocene magmatism was related to extensional collapse of a thickened orogen

dextral strike slip along the kapidag shear zone nw turkey evidence for eocene westward translation of the anatolian plate the northern part of the kapidag peninsula marmara sea nw turkey is affected by the e w trending kapidag shear zone which cuts through calc alkaline granitoids of the ocaklar pluton resulting in mylonitic orthogneiss macroscopic and microscopic shear sense indicators such as sc fabrics shear bands clasts and mica fish unequivocally suggest dextral strike slip for the kapidag shear zone based on petrographic data deformation microfabrics of quartz and feldspar and the slip systems in quartz the dextral shearing should have been active at t 500 300 c and p 5 kbar published k ar and 39ar 40ar cooling ages of hornblende and biotite suggest that cooling below 500 300 c occurred during the eocene ca 45 ca 35 ma meaning that the kapidag shear zone should have been active during middle to late eocene times the differential stress related to the shearing was 50 mpa as is indicated by the size of recrystallized quartz grains based on the new and published data it is concluded that the westward movement of the anatolian plate might have been active almost continuously from the middle eocene until recent times

coeval plutonism and metamorphism in a latest oligocene metamorphic core complex in northwest turkey a metamorphic core complex of latest oligocene age crops out in the kazdag mountain range in northwest turkey the footwall of the core complex consists of gneiss amphibolite and marble metamorphosed at 5 1 kbar and 640 50 c the average muscovite and biotite rb sr ages from the gneisses are 19 ma and 22 ma respectively and imply high temperature metamorphism during latest oligocene times the hangingwall is made up of an unmetamorphosed lower tertiary oceanic accretionary melange with upper cretaceous eclogite lenses the hangingwall and footwall are separated by an extensional ductile shear zone two kilometres thick mylonites and underlying high grade metamorphic rocks show a n trending mineral lineation with the structural fabrics indicat ing down dip top to the north shear sense the shear zone the accretionary melange and the high grade metamorphic rocks are cut by an undeformed granitoid with a 21 ma rb sr biotite age analytically indistinguishable from the rb sr biotite ages in the surrounding footwall gneisses the estimated pressure of the metamorphism and that of the granitoid emplacement indicate that the high grade metamorphic rocks were rapidly exhumed at 24 ma from a depth of 14 km to 7 km by activity along the shear zone the subsequent exhumation of the metamorphic rocks to the surface occurred during pliocene quaternary times in a transpressive ridge between two overstepping fault segments of the north anatolian fault zone the high grade metamorphic rocks of the kazdag range are surrounded by voluminous calc alkaline volcanic and plutonic rocks of late oligocene early miocene age which formed above the northward dipping hellenic subduction zone the magmatic arc setting of the core complex and stratigraphic evidence for subdued topography in northwest turkey prior to the onset of extension suggest that the latest oligocene regional extension was primarily related to the roll back of the subduction zone rather than to the gravitational collapse

the mission link between the hayward and calaveras faults the left stepover between the calaveras and hayward faults gives rise to compressive strain that is accommodated by vertical deformation producing the highest hills bordering the east side of san francisco bay monument peak to mission peak the projection of the active trace of the hayward fault is separated 3 5 km from the junction of the northern and southern segments of the calaveras fault at calaveras reservoir for pure strike slip on the hayward and calaveras faults the stepover region is compressed in area at a rate given by the separation times the long term slip rate of 9 mm yr on the hayward fault assuming a seismogenic depth of 10 km the horizontal compression accumulated over 150 years is equivalent to a dip slip seismic moment of 2 8 1018 n m this moment if released in a single event would generate an earthquake of magnitude 6 3 due to dip slip alone dip slip may occur on buried faults throughout the stepover region the base of the southwest face of monument peak suggests a buried thrust or reverse fault dipping northeast the prominent scarp on mission peak has the same strike and sense of slip current microearthquakes between the calaveras and hayward faults align parallel to the mission fault but show only horizontal slip on a vertical fault plane a dipping fault is needed to satisfy the geometric constraint of the convergence therefore the mission fault zone must consist of two or more fault surfaces inclined at different dip angles as is observed in the san andreas fault zone in the loma prieta area horizontal slip is building up stress on the inclined fault which is currently locked growing compressive stress will increasingly impede horizontal slip until a thrust or reverse slip event occurs allowing then more horizontal slip to be transferred from the calaveras to the hayward fault the dip slip fault might be the unstable element governing slip in the larger system

high resolution image of calaveras fault seismicity 1 by measuring relative earthquake arrival times using waveform cross correlation and locating earthquakes using the double difference technique we are able to reduce hypocentral errors by 1 to 2 orders of magnitude over routine locations for nearly 8000 events along a 35 km section of the calaveras fault this represents 92 of all seismicity since 1984 and includes the rupture zone of the m 6 2 1984 morgan hill california earthquake the relocated seismicity forms highly organized structures that were previously obscured by location errors there are abundant repeating earthquake sequences as well as linear clusters of earthquakes large voids in seismicity appear with dimensions of kilometers that have been aseismic over the 30 year time interval suggesting that these portions of the fault are either locked or creeping the area of greatest slip in the morgan hill main shock coincides with the most prominent of these voids suggesting that this part of the fault may be locked between large earthquakes we find that the calaveras fault at depth is extremely thin with an average upper bound on fault zone width of 75 m given the location error however this width is not resolvably different from zero the relocations reveal active secondary faults which we use to solve for the stress field in the immediate vicinity of the calaveras fault we find that the maximum compressive stress is at a high angle only 13 from the fault normal supporting previous interpretations that this fault is weak

the mount kozak magmatic complex western anatolia abstract the mount kozak igneous complex is located close to the towns of ayvalik bergama and burhaniye in the western anatolia turkey magmatic activity occurred during the late oligocene early miocene beginning with the emplacement of the kozak pluton sheet intrusive rocks formed around it coevally they are surrounded by the volcanic rocks partly contemporaneously with the emplacement of the granitic rocks during the early miocene the upper oligocene lower miocene magmatic rocks of the kozak region are represented by a high k calc alkaline suite of predominantly intermediate and acidic composition their geochemical characteristics suggest that the magmas are hybrid and were formed from a similar source representing mantle derived magmas contaminated by crustal materials the cogenetic plutonic rocks the hypabyssal rocks and the overlying volcanic associations are related to one another in space and time and appear to have been connected to a shallow level granitic intrusion in a caldera collapse setting the calc alkaline magmatic activity waned during the middle miocene when the volcanism was rejuvenated during the late miocene pliocene alkaline basalt lavas were formed as fissure eruptions

the emplacement history of granitic intrusions into the upper crust forceful to passive emplacement of the early miocene solarya pluton nw turkey as a case study abstract post collisional magmatism in western anatolia produced several granitic bodies represented by shallow level intrusions in this study we present field geochronology and geothermo barometry results of the solarya pluton sp nw turkey in order to better understand its emplacement into the different levels of the crust the sp consists of three main plutonic members showing different textural properties the northern part of the plutonic body is represented by k feldspar megacrystalline granodiorite kfmg with distinct porphyritic texture and southern part is made up of microgranite granodiorite mgg displaying microgranular texture whereas haplogranite which displays graphic granophyric textures is represented by a thin aureole between the sp and basement rocks field relations petrography and geothermo barometry studies combined with 40ar 39ar and u pb zircon dating results suggest that different members of the sp were emplaced into different levels of crust with different mechanisms the kfmg 40ar 39ar 23 2 ma u pb 21 8 ma began its emplacement forcefully in the relatively deeper levels in the crust av 1 65 kbar av 797 c 6 1 km depth after this stage mgg 40ar 39ar 22 6 ma u pb 21 2 ma was passively emplaced into the shallow levels av 0 69 kbar av 745 c 2 4 km depth via cauldron subsidence and in the latter stages the sheet intrusive rocks haplogranite 40ar 39ar 21 6 ma and hypabyssal association were emplaced into the ring faults at 1 5 km depth forceful to passive emplacement of the sp into the upper crust occurred under aegean extensional tectonics our study contributes to examination of the granite ascent and emplacement within other extensional provinces worldwide

isotopic evidence from the ivrea zone for a hybrid lower crust formed by magmatic underplating the large mafic complex overlying mantle peridotites in the ivrea zone of northern italy originated by underplating of mantle derived magma onto the base of continental crust and may be a unique outcrop of typical mafic lower crust sampled elsewhere only by mafic xenoliths neodymium and strontium isotope data show that the magmas assimilated large and roughly uniform proportions of crustal material the resulting hybrid magmas have the same isotopic signature as and may represent the lower crustal roots of upper crustal hercynian granitoid intrusions

a case study of compression to escape tectonic transition tectonic evolution of the nallihan wedge and comparison with the tercan wedge eastern mediterranean turkey abstract the nallihan and cayirhan regions in western anatolia host the stratigraphically and tectonically important features of nallihan wedge the stratigraphic relationships and structural architecture of the wedge are not well understood which are essential for better understanding of the timing and tectonic evolution of western anatolia today the nallihan wedge is bounded by the north anatolian fault and the thrace eskisehir fault in the northwest and southwest respectively the existence of dagkuplu melange within the wedge represents the closure of the izmir ankara ocean the occurrence of the lower jurassic shelf slope reef and deep sea successions transitioning upward into the cretaceous shelf and slope successions represent the opening and closing cycles of the intra pontide ocean the tight and asymmetric folds steep in the west gentle in the east within this stratigraphic sequence and the development of the eocene units reflect the closure of the intra pontide and izmir ankara oceans the geometric structure and evolution of the nallihan wedge is directly related to the final continental collision w e and sw ne striking large scale oblique thrusts also exhibit notable strike slip components within the study area the principal direction of the fold axes are w e and wnw ese oriented for the eocene and neogene units during the eocene the depositional environment of the study area was a ramp basin mainly dominated by a braided river when a portion of the intra pontide ocean was situated on the northern side of the study area the compressional tectonic regime continued to the end of the oligocene which is followed by a new tectonic regime during the miocene when the triangular shape region between the thrace eskisehir fault and the north anatolian fault developed as an intermontane basin the evolution of this basin can be compared with the tercan wedge bordered by the north eastern anatolian fault and the north anatolian fault in the nallihan and cayirhan regions the n s trending compressional regime started during the upper cretaceous and continued until the final continental collisional during the upper eocene the compressional structures in the area became reactivated during the post collisional escape tectonic phase in western anatolia leading to the development of the prominent isparta angle during the miocene during this period the thrace eskisehir fault and burdur fethiye shear zone also formed as intracontinental transform fault zones in western anatolia the nallihan wedge started to form in a wedge shaped area between the thrace eskisehir fault and the zone of strike slip faults with thrust component that later developed into the north anatolian fault thus eocene and pre eocene structures obtain strike slip component by an inversion during the miocene during and post pliocene the thrace eskisehir fault lost its tectonic activity as the north anatolian fault propagated westward into the region previously controlled by the thrace eskisehir fault during this interval the nallihan wedge entered a new stage of deformation which is also observed today

slab breakoff a model for caledonian late granite syn collisional magmatism in the orthotectonic metamorphic zone of scotland and donegal ireland abstract none of the existing models for calc alkaline late granite siluro devonian genesis in the metamorphic caledonian orogenic belt of ireland and scotland fully explains their spatial age or chemical character a consistent model must involve the closure of iapetus ocean where slab breakoff is a natural consequence of attempted subduction of continental crust expected outcome is a long linear belt of high k calc alkaline magmas some with characteristic trace element signatures specifically high ba sr and zr other features include the critical magmatic association of coeval appinite and granite rapid uplift erosion and the low grade regional metamorphism in the southern uplands the linear heat pulse on breakoff is spatially intensity and time limited producing small volume melts emplaced as separated plutons over a short time span magmatism in the caledonian metamorphic belt is accurately accounted for by slab breakoff on collision of baltica with the scoto greenland margin during the scandian orogeny following iapetus ocean closure the two chemically isotopically and areally distinctive suites in the metamorphic belt in scotland viz the argyll and cairngorm suites can be modelled by reference to the donegal granites where sequential partial melting of new lamprophyric underplated crust then shallower old crust as heat conduction moved up through the crust on slab breakoff produced magmas characteristic of the two suites

slab breakoff a model of lithosphere detachment and its test in the magmatism and deformation of collisional orogens we present a model proposing that oceanic lithosphere detaches from continental lithosphere during continental collision slab breakoff allowing an explanation of syn to post collisional magmatism and metamorphism continental collisions are preceded by subduction of dense oceanic lithosphere and followed by attempted subduction of buoyant continental lithosphere this situation of opposing buoyancy forces leads to extensional deformation in the subducted slab a narrow rifting mode of deformation will result if there is strain localization slab breakoff results we have assessed the plausiblity of this process by quantitatively evaluating an upper bound for the strength of the lithosphere and have compared it with the change in buoyancy force during continental sbduction whether breakoff will occur and the depth at which it will occur is a strong function of temperature and hence the subduction velocity for a subduction velocity of 1 cm yr breakoff could occur at depths of between 50 and 120 km while at higher velocities it is still likely to occur but at deeper depths as a result of the rifting during breakoff the asthenosphere upwells into the narrow rift and following breakoff it impinges on the mechanical lithosphere of the overriding plate the resulting conducted thermal perturbation leads to melting of the metasomatised overriding mantle lithosphere producing basaltic magmatism that leads to granitic magmatism in the crust dry asthenospheric mantle will melt only if breakoff occurs at a depth shallower than ca 50 km breakoff removes the force at the downdip side of the continental crust while the enhanced heating leads to a reduction of the strength of the underlying crust both effects facilitate the freeing of buoyant crustal sheets which can then rise towards the surface leading to the rapid exhumation of eclogite facies continental crust the cessation of subduction and replacement of the cold oceanic lithosphere by asthenosphere leads to rapid uplift of the orogen we have tested the variety of predicted expressions of slab breakoff in the geological record of the alps the aegean islands and the dabie shan a comparison of the various belts highlights 1 that the magmatism and metamorphism are found near the suture and the centre of the orogen demonstrating the general steepening of suture during collision 2 that a vague inverse correlation exists between maximum depth of metamorphism and volume of syn orogenic magmatism and 3 that the melts can be emplaced in both compressive and extensional environments we suggest that slab breakoff is an important step in the evolution of many orogenic belts and it allows an explanation for the combined presence in collisional orogens of magmatism with a mantle parentage and ultra high pressure metamorphics

distribution of interseismic slip rates and the potential for significant earthquakes on the calaveras fault central california 1 the calaveras fault is a major component of the san andreas fault system in the san francisco bay area that generated 13 earthquakes of ml 5 since 1850 in most recent ml 5 events premain shock and postmain shock microseismicity is sparse in the region of coseismic slip these aseismic areas are believed to represent locked patches of the fault that are accumulating strain to be released in ml 5 events we analyze geodetic data to better characterize the spatial distribution of interseismic slip rates on the calaveras fault modeling the slip distribution in the seismogenic zone by inversion of over 25 years of surface deformation data we use a regional fault model with the seismogenic zone of the calaveras fault discretized into 6 km 3 km elements employing a weighted least squares approach with smoothing and positivity constraints our discretized fault slip model consistently identifies regions of slip deficit in the seismogenic zone of the calaveras fault that generally correspond to regions of decreased microseismicity and ruptures of previous moderate earthquakes in particular we find correspondence with the 1979 coyote lake and 1984 morgan hill events as well as regions where historical earthquakes on the coyote and the sunol san ramon segments have occurred moment magnitude calculations based on the estimated slip deficit fault area and recurrence intervals agree with measured magnitudes of modern events and interpreted historical magnitudes the results suggest that a combination of geodetically derived fault slip models and microseismicity distribution can be used to characterize seismic hazard

post collision magmatism and tectonics in northwest anatolia a suite of biotite hornblende granodiorite intrusions has been emplaced into blueschist facies metasediments in northwest anatolia following collision between two continental margins now represented by the tavsanli and sakarya zones the 40ar 39ar ages of phengites and glaucophanes from the blueschists metamorphosed under unusually high p low t conditions p 20 2 kbar t 430 30 c suggest that metamorphism apparently occurred over a period spanning at least 20 ma from 108 to 88 ma post tectonic granodiorites were emplaced during the eocene 53 to 48 ma resulting in a cordierite and andalusite bearing thermal aureole indicative of pressures of 3 kbar trace element systematics of the granodiorites are consistent with a derivation either from mantle derived magmas by fractional crystallisation in shallow magma chambers or from anatexis of crustal lithologies of internediate composition at pressures 10 kbar the preservation of high p low t assemblages in the blueschists together with the range of ages determined for blueschist facies metamorphism are indicative of rapid exhumation of delaminated fragments from a subducted continental margin however decompression melting of the crust is unlikely to have been a significant cause of magmatism both because exhumation of the blueschists from deep crustal levels predated magmatism by at least 25 ma and because of the small melt fraction 0 1 that may be generated in crustal lithologies by this process melting in the mantle wedge is required either to generate a primary melt for the derivation of magmas of intermediate composition or to provide an advective heat source for crustal melting the cause of melt formation in the upper mantle may be related to the termination of subduction following collision during the mid eocene

morphology spatial pattern and sediment of nitraria tangutorum nebkhas in barchans interdune areas at the southeast margin of the badain jaran desert china abstract to understand the characteristics of the nebkhas in barchan interdune areas isolated barchan dunes at the southeast margin of the badain jaran desert in china and nitraria tangutorun nebkhas in the interdune areas were selected and the morphometric parameters spatial patterns and granulometric characteristics of the nebkhas in various interdune zones were compared according to the locations relative to barchan dunes the interdune areas were divided into three zones the windward interdune zone zw the leeward interdune zone zl and the horn interdune zone zh the zone that is proximal to barchan dunes and has never been disturbed by barchan dunes was also selected zi the morphometric parameters were measured through a satellite image and field investigation the population density and spatial patterns were analyzed using the satellite image and surface sediment samples of the nebkhas and barchan dunes were collected for grain size analysis the morphometric parameters of nitraria tangutorun nebkhas in the interdune zones differ significantly the nebkhas in zh are larger than those observed in the other zones and the nebkhas are the smallest in zl in all of the zones the long axis orientation of the nebkhas is perpendicular to the prevailing wind direction the population density of the nebkhas in zw is relatively higher whereas the density in zh and zl becomes obviously lower the spatial distribution of nebkhas in all of the zones can be categorized as a dispersed pattern the sediments of the nebkhas are coarsest in zh and finest in zl in addition the sediments of the nebkhas in all of the zones are finer than those of barchan dunes the amount of sand captured by the nebkhas in the interdune areas is approximately 20 of the volume of barchan dunes the variations of the nebkhas sizes spatial pattern and sediment are subjected to migration flow field and sand transport of barchan dunes and sand accumulation with plant growth in the interdune areas which suggest complex mutual interactions between barchan dunes and the nebkhas in the interdune areas

coseismic deformation during the 1989 loma prieta earthquake and range front thrusting along the southwestern margin of the santa clara valley california damage patterns caused by the 1989 loma prieta earthquake along the southwestern margin of the santa clara valley california form three zones that coincide with mapped and inferred traces of range front thrust faults northeast of the san andreas fault damage in these zones was largely contractional consistent with past displacement associated with these faults the damage zones coincide with gravity and aeromagnetic anomalies modeling of the anomalies defines a southwest dipping thrust fault that places the franciscan complex over cenozoic sedimentary rocks to minimum depths of 2 km diffuse loma prieta earthquake aftershocks encompass the downward projection of this modeled thrust to depths of 9 km our results indicate that in this region the potential for concentrated damage arising from either primary deformation along the thrust faults themselves or by sympathetic motion triggered by earthquakes on the san andreas fault may be higher than previously recognized

fission track thermochronology vertical kinematics and tectonic development along the western extension of the north anatolian fault zone 1 we have investigated the low temperature history of pre neogene basement areas adjacent to the western extension of the north anatolian fault zone nafz by apatite fission track thermochronology of 33 samples taken from marmara island kapidag peninsula both in the sea of marmara samothrake island and chalkidike peninsula both in the north aegean region together with already published apatite fission track data from 30 other sampling localities of the region these data 63 in total have been evaluated mainly with regard to the transitional period from the mesohellenic orogeny eocene oligocene to the plate tectonical individualization of the aegean antolian microplate to gain a better understanding of the tectonical chronology that has led to modern east mediterranean plate tectonics apatite fission track investigations of the area under discussion reveal two major events of cooling and exhumation of pre neogene rocks a first frequency maximum of cooling ages between 35 and 25 ma late eocene to early oligocene is due to postorogenic regional erosion after the climax of the mesohellenic orogeny which was caused by continental collision of the pelagonian platform and the rila rhodope zone after the final closure of the axios vardar ocean a second frequency maximum of cooling ages between 17 and 11 5 ma early to middle miocene depicts more localized uplift and exhumation in consequence of transpressive and or transtensive movements along early structural discontinuities that gave rise to the later fault systems in the western extension of the nafz the earliest fault structures of this system have developed shortly after the orogenic collapse and crustal extension of the rila rhodope area but quasi simultaneously with the onset of subduction along the modern hellenic trench the regional distribution of fission track ages of the miocene age group 17 to 11 5 ma and corresponding thermochronological calculations based on frequency distributions of confined track lengths suggest that an early fault propagation has occurred from east to west during the miocene the onset of subduction along the hellenic trench and subsequent gravitational retreat of the subducting oceanic slab are considered as a major cause for transtension of the aegean crust especially with regard to the development of north aegean pull apart basins such early fault structures have facilitated the westward propagation of a continuous nafz that took place during the pliocene from the easternmost marmara region to the gallipoli peninsula and to the north aegean trough

fault geometry at the rupture termination of the 1995 hyogo ken nanbu earthquake the source geometry and slip distribution at rupture termination of the 1995 hyogo ken nanbu earthquake were investigated using waveform inversion on the assumption of fault branching in the northeastern part of the rupture model possible branching of the okamoto fault is suggested both by the static displacement distribution and damage extension east of kobe nishinomiya area to exclude data contaminated by the basin edge diffracted wave in the waveform inversion process we examined the spatio temporal variation of its influence and from a comparison with a flat model we determined windows appropriate for the data three subevents were identified as was reported in previous works the largest was in the shallow part on the awaji side whereas the smaller two occurred at great depths 7km on the kobe side we found a smaller subevent in the deep part of the branch total variance reduction was larger and the abic value was smaller when we assumed the branch than when we did not which shows the superiority of the branching fault model resolution checks showed that the slips on proposed branched portions are physical and not caused by random data noise or systematic errors in green s func tions that arise from misestimation of velocity structures calculation of the relative static displacement between two leveling observation stations near the branching fault also showed the greater utility of the branching fault model the effect of slip on the branched fault has been shown in near source ground motion simulation using the 3d finite difference method iwata et al 1999 the characteristic distribution of ground motion in the near source region indicated by the damage distribution is well reproduced by the modeling of both the source process and wave propagation in the realistic 3d velocity structure slip on the branched fault affected the ground motion in eastern kobe nada and higashi nada wards ashiya and nishinomiya cities but its contribution is not dominant even in those regions about 30 to 50 maximum velocity in the frequency range of 0 1 to 1 0 hz we conclude that branching rupture of the okamoto fault during the hyogo ken nanbu earthquake is the preferable interpretation on the source process of this earth quake this supports the idea of a geometrical barrier suggested by geological ob servations

the combined inversion of seismic and geodetic data for the source process of the 16 october 1999 mw 7 1 hector mine california earthquake we investigate the source process of the m w 7 1 hector mine earthquake by inverting broadband regional and local seismic displacement waveforms com bined with global positioning system gps and synthetic aperture radar interfer ometry insar geodetic measurements we find that the three data sets individually produce remarkably similar slip distributions over a multisegment fault a simulta neous inversion of the three data sets is presented and the sensitivity of the combined inversion to the weighting of the three independent data sets is examined the results indicate that the overall length of the fault that slipped is 42 km with a peak slip of 5 50 m and total scalar seismic moment of 6 8 10 19 n m the majority of slip is located on the western branch of the lavic lake fault to the northwest of the hypo center although the overall rupture is bilateral with appreciable slip on the bullion fault to the southeast some slip is located on an eastern branch of the lavic lake fault an apparent bifurcation which is also evident from aftershock locations the average slip and stress drops are 2 70 1 62 1 60 m and 78 36 and 55 bars for the western lavic lake the eastern lavic lake and bullion faults respectively the results also indicate that the overall rupture process is relatively slow which is char acterized by a several second delay before the onset of significant slip a 1 8 km sec rupture velocity of the primary asperity and long spatially variable dislocation rise times

origin of the early middle devonian magmatism in the sakarya zone nw turkey geochronology geochemistry and isotope systematics abstract a unique example of isotopically dated devonian metagranitoid the camlik metagranite okay et al 1996 crops out in the biga peninsula nw turkey although its contact relationships with the country rocks and geodynamic setting have remained to be enigmatic so far our field work however has shown that a number of metagranitoid bodies similar to the camlik metagranite intruded the country rocks and developed contact metamorphic zones consisting of andalusite and calcsilicate hornfelses garnet epidote and diopsite wollastonite skarns the country rocks of these metagranitoids are made up of regionally metamorphosed metaclastic successions with subordinate metacarbonate metachert metabasites the kalabak formation intercalated with tectonic slices of meta serpentinites the metagranitoids and the kalabak formation are collectively termed here the havran unit which forms a ne sw trending 20 km wide and 80 km long belt in the biga peninsula the havran unit is unconformably overlain by the late triassic shallow marine sediments and is in tectonic contact with the permo triassic karakaya complex interpreted as the palaeotethyan subduction accretion complex u pb shrimp ii and la icp ms dating of the zircons from four individual plutons yielded crystallization ages ranging from 389 1 2 6 to 401 5 4 8 ma i e early to middle devonian based on their geochemical characteristics the metagranitoids are divided into two groups named the camlik and yolindi metagranitoids both granitoids display distinct subduction signature and plot in the volcanic arc granite and post collisional granite fields on tectonic discrimination diagrams 87 sr 86 sr t values of these intrusions vary between 0 707367 and 0 715588 while their 143 nd 144 nd t values range from 0 51166 to 0 51187 very low values of end t from 5 3 to 9 1 imply that the lower to mid devonian metagranitoids in the havran unit might have been generated by partial melting of lower continental crust probably driven by a major magma underplating event delamination and or slab breakoff models are considered to be the most plausible mechanisms for the genesis of these metagranitoids the data obtained in this study has shown for the first time the widespread existence of devonian and older basement in nw turkey regional geological correlations imply that this basement may be an exotic terrane in the sakarya zone emplaced during the late triassic prior to its amalgamation with the palaeotethyan karakaya complex

rupture process of the 1999 kocaeli turkey earthquake estimated from strong motion waveforms the multiple time window linear waveform inversion is applied to study the source process of the 1999 kocaeli turkey earthquake using strong motion data two peculiar observations characterize this event the first one is a conflicting observation of the long surface ruptures and short source duration resulting from the observed strong motion waveforms the second is an anomalously short s p time observed at a station skr considering its hypocentral distance a supershear rupture propagation ellsworth and celebi 1999 and the p wave triggering of an asperity anderson et al 2000 were both proposed to explain the record at skr our waveform inversion study is aimed to examine these possibilities in order to clarify the relation between the spatial distribution of the surface ruptures and coseismic slips we divide the assumed fault plane into three parts and look for the first time window front propagation velocity propagation velocity of triggering front of the first time window at each subfault in each part by performing numerous inversions changing the first time window front propagation velocity separately in each part and selecting the best first time window propagation velocities that give largest variance reduction at the same time appropriate smoothness of spatiotemporal slip distribution is searched for by performing inversions with different strength of smoothing constraints against the observational equations and judging the relative appropriateness of inversion results in terms of the akaike s bayesian information criterion the best source model is characterized by an asperity that is about 35 km east of the epicenter and near a segment boundary at sapanca lake triggered by the first time window front with 5 8 km sec close to p wave velocity the time progression of the rupture suggests a scenario where a p wave arriving from the hypocenter or somewhere around the hypocenter triggered the second largest asperity near the junction of the segments at sapanca lake which is a preferable interpretation the first time window propagation velocities west of the hypocenter and east of skr are expected to be 3 0 km sec manuscript received 20 august 2000

obduction subduction and collision as reflected in the upper cretaceous lower eocene sedimentary record of western turkey late cretaceous early eocene tethyan evolution of western turkey is characterized by ophiolite obduction high pressure low temperature metamorphism subduction arc magmatism and continent continent collision the imprints of these events in the upper cretaceous lower eocene sedimentary record of western anatolia are studied in thirty eight well described stratigraphic sections during the late cretaceous period western turkey consisted of two continents the pontides in the north and the anatolide taurides in the south these continental masses were separated by the izmir ankara neo tethyan ocean during the convergence the pontides formed the upper plate the anatolide taurides the lower plate the arc magmatism in the pontides along the black sea coast is biostratigraphically tightly constrained in time between the late turonian and latest campanian ophiolite obduction over the passive margin of the anatolide tauride block started in the santonian soon after the inception of subduction in the turonian as a result large areas of the anatolide tauride block subsided and became a region of pelagic carbonate sedimentation during the campanian the leading margin of the anatolide tauride block was buried deeply and was deformed and metamorphosed to blueschist facies during campanian times the campanian arc volcanic rocks in the pontides are conformably overlain by shaley limestone of maastrichtian palaeocene age however maastrichtian sedimentary sequences north of the tethyan suture are of fore arc type suggesting that although arc magmatism ceased by the end of the campanian age continent continent collision was delayed until palaeocene time when there was a change from marine to continental sedimentation in the fore arc basins the interval between the end of the arc magmatism and continent continent collision may have been related to a northward jump of the subduction zone at the end of campanian time or to continued obduction during the maastrichtian

a prospective sector in the tethyan metallogenic belt geology and geochronology of mineral deposits in the biga peninsula nw turkey abstract the tethyan metallogenic belt tmb extending from europe through anatolia to iran is one of the world s major metal producing belts and consists of many sectors mineral deposits of the biga peninsula in northwestern turkey exhibit in many ways the characteristics of mineral deposits found throughout the belt biga peninsula tectonically forms the westernmost part of the sakarya zone and easternmost part of the rhodope zone at the intersection of gondwana and laurasia the biga peninsula metallogeny research and exploration project created a gis inventory of mineral deposits and prospects and classified them genetically to evaluate the mineral deposit potential using genetic models based on descriptive data the gis database consisting of 128 deposits or prospects helped to generate new prospects and potential prospects this field based study indicated that the biga peninsula forms a prime target for gold copper exploration not only in turkey but in the world the current economically significant mineral deposits of the biga peninsula were shaped by cenozoic calc alkaline magmatism ranging between 52 and 18 ma and related to mainly collisional and post collisional tectonic regime epithermal au ag deposits including high hs low ls and intermediate sulfidation is styles porphyry au cu mo and base metal skarn systems are economically the most important though there are no currently economic examples of some of them in the biga peninsula other deposit types include carlin like distal disseminated au ag orogenic au especially listwanite hosted volcanogenic mn and u lateritic ferricrete fe deposits carbonate replacement cr and placers several active metal mines such as balya arapucandere and koru are operating in the biga peninsula kucukdere au ag deposit in balikesir is the only gold mine in the biga peninsula except for by product gold produced from base metal deposits results of the study show current total gold endowment of the biga peninsula including reserves and or resources is 9 18 moz gold 284 2 t contained in twelve different deposits of these only 6 contain significant gold 0 3 moz or 10 t halilaga porphyry and agi dagi and kirazli hs epithermal systems have an ongoing resource estimate and halilaga is a candidate to be one of the largest cu au deposits not only in the biga peninsula but in turkey currently newly discovered tepeoba is the largest porphyry cu mo au deposit with known resources in the biga peninsula here the first 40 ar 39 ar step heating age data conducted on some of the major hs epithermal gold deposits and causative intrusives in the biga peninsula are reported geochronological results from this project evaluated with previous studies indicate at least 3 phases of porphyry and 2 phases of high sulfidation epithermal gold mineralization in the biga peninsula the most important mineralizing phases and related host rocks for gold mineralization range from 38 to 22 ma the oligocene is especially important for economic epithermal and porphyry systems in the biga peninsula which is comparable to deposits in the oligo miocene serbomacedonian rhodope metallogenic belt of the balkan peninsula in se europe

a regional view of urban sedimentary basins in northern california based on oil industry compressional wave velocity and density logs compressional wave sonic and density logs from 119 oil test wells provide knowledge of the physical properties and impedance contrasts within urban sedimentary basins in northern california which is needed to better understand basin amplification these wire line logs provide estimates of sonic velocities and densities for primarily upper cretaceous to pliocene clastic rocks between 0 1 and 5 6 km depth to an average depth of 1 8 km regional differences in the sonic velocities and densities in these basins largely 1reflect variations in the lithology depth of burial porosity and grain size of the strata but not necessarily formation age for example miocene basin filling strata west of the calaveras fault exhibit higher sonic velocities and densities than older but finer grained and or higher porosity rocks of the upper cretaceous great valley sequence as another example hard eocene sandstones west of the san andreas fault have much higher impedances than eocene strata mainly higher porosity sandstones and shales located to the east of this fault and approach those expected for franciscan complex basement rocks basement penetrations define large impedence contrasts at the sediment basement contact along the margins of several basins where quaternary pliocene and even miocene deposits directly overlie franciscan or salinian basement rocks at depths as much as 1 7 km in contrast in the deepest geographic centers of the basins such logs exhibit only a modest impedance contrast at the sediment basement contact at depths exceeding 2 km prominent up to 1 km sec and thick up to several hundred meters velocity and density reversals in the logs refute the common assumption that velocities and densities increase monotonically with depth online material borehole log regression parameters and metadata

mineral chemistry crystallization conditions and geodynamic implications of the oligo miocene granitoids in the biga peninsula northwest turkey abstract widespread plutonic rocks in nw turkey occur within the southward younging and overlapping magmatic belts across the aegean region post collisional magmatism is represented by a series of granitoidic intrusions and volcanic successions k ar and u pb la icp ms zircon dating of the kazdag and yenice plutons yielded ages between 20 5 0 5 ma and 27 89 0 17 ma late oligocene early miocene the granitoid samples are high k calc alkaline and metaluminous to slightly peraluminous the 87sr 86sr values for the granitoids enclaves and leucocratic rocks range between 0 705168 and 0 708357 the initial 143nd 144nd ratios calculated for the crystallization ages of ca 23 27 ma are between 0 512425 and 0 512614 and the end values vary from 3 5 to 0 2 the nd tdm model ages range between 0 73 and 1 13 ga these samples are enriched in liles and lree and depleted in hfses with negative eu anomalies indicating that the melts were derived from an enriched lithospheric mantle modified by subducted slab derived melts energy constrained assimilation and fractional crystallization ec afc modelling indicates that fractional crystallization and crustal assimilation modified the parent magma s composition during its residence in the upper crust the mineral chemistry of amphiboles pyroxenes biotites and feldspars is used to constrain the pressure p temperature t oxygen fugacity log o2 and water contents h2omelt during the crystallization of the magmas in the studied granitoids the clinopyroxene temperatures are in the range of 823 910 45 c the amphibole temperatures for the studied plutonic rocks are in the range of 707 926 c mean 798 45 c and the crystallization depths are estimated to be in the interval of 1 02 10 2 km the nw anatolian plutonic rocks can be considered to have been equilibrated at the oxygen fugacities of calcic amphiboles log o2 between 8 99 and 13 96 bars mean 12 11 bar and h2omelt contents between 1 63 and 6 79 mean 4 15 meanwhile the biotites which display consistent oxygen fugacity values 10 65 to 13 22 suggest their reliability with the typical values of calc alkaline magma crystallization these values suggest a relatively higher oxidation state during crystallization and are related to arc magmatism all of the calculated values indicate that all of the plutons were emplaced at shallow crustal levels it can be inferred that the oligo miocene magmatism in nw turkey may be linked to crustal thinning that resulted from slab roll back and a back arc extensional regime after the collision between the sakarya zone and anatolide tauride platform

wind tunnel simulation of the three dimensional airflow patterns around shrubs 1 dunes formed around vegetation such as shrubs are common in arid and semiarid regions and some coastal regions understanding their dynamics requires insights into the airflow patterns around shrubs thus we analyzed the horizontal and vertical flow patterns around model shrubs using wind measurements obtained by particle image velocimetry in a scaled wind tunnel simulation flow patterns around shrubs were complicated by the presence of bleed flows and displaced flows below a critical shrub density between 0 05 and 0 08 bleed flow is dominant the flows separate in both horizontal and vertical planes when the shrub density equals or exceeds this critical density resulting in reverse cells in the lee of shrubs the horizontal reverse cells are characterized by two symmetrical opposing reverse eddies whereas the vertical reverse cells form a single eddy the positions of the reverse cells shift in response to changes in shrub density reflecting the interaction between bleed flow and reverse flow the parameters of horizontal reverse cells are functions of shrub density and wind velocity parameters of vertical reverse cells change mainly with respect to shrub density and vary only slightly with wind velocity the lengths of the horizontal and vertical reverse cells are correlated reflecting interactions between them field experiments on dune morphology will be required to relate these airflow patterns to dune development

neotethyan closure history of western anatolia a geodynamic discussion this paper addresses the lithosphere scale subduction collision history of the eastern termination of the aegean retreating subduction system i e western anatolia although there is some general consensus on the protracted subduction evolution of the aegean since the early cenozoic at least correlation with western anatolia has been widely debated for more than several decades in western anatolia three main tectonic configurations have been envisaged in the past years to reconstruct slab dynamics during the closure of the neotethyan oceanic realm since the late cretaceous some authors have suggested an aegean type scenario with the continuous subduction of a single lithospheric slab punctuated by episodic slab roll back and trench retreat whereas others assumed a discontinuous subduction history marked by intermittent slab break off during either the campanian ca 75 ma or the early eocene ca 55 50 ma the third view implies three partly contemporaneous subduction zones our review of these models points to key debated aspects that can be re evaluated in the light of multidisciplinary constraints from the literature our discussion leads us to address the timing of subduction initiation the existence of hypothetical ocean basins the number of intervening subduction zones between the taurides and the pontides the palaeogeographic origin of tectonic units and the possibility for slab break off during either the campanian or the early eocene thence we put forward a favoured tectonic scenario featuring two successive phases of subduction of a single lithospheric slab and episodic accretion of two continental domains separated by a continental trough representing the eastern end of the cycladic ocean of the aegean the lack of univocal evidence for slab break off in western anatolia and southward younging hp lt metamorphism in continental tectonic units from 85 70 to 50 ma in the late cretaceous palaeogene period suggests continuous subduction since 110 ma marked by roll back episodes in the palaeocene and the oligo miocene and slab tearing below western anatolia during the miocene

variable vegetation cover and episodic sand movement on longitudinal desert sand dunes abstract longitudinal linear sand dunes of the simpson and strzelecki dunefields in eastern central australia present a paradox low levels of activity today stand in contrast to luminescence dating which has repeatedly shown deep deposits of sand on dune crests dating to within the late holocene in order to investigate the nature of dune activity in the simpson strzelecki dunefield vegetation and sand mobility were investigated by detailed vegetation survey and measurement of rippled area and loose sand depth of dunes at three sites along a climatic gradient the response of both vegetation and sand movement to inter annual climate variability was examined by repeat surveys of two sites in drought and non drought conditions projected plant cover and plant crust cover were found to have inverse linear relationships with rippled area and the area of deep loose sand no relationship was found between these measures of sand movement and the plant frontal area index a negative exponential relationship between equivalent mobile sand depth on dune surfaces and both vascular plant cover and vascular crust cover was also found there is no simple threshold of vegetation cover below which sand transport begins dunes with low perennial plant cover may form small dunes with slip faces leading to a positive feedback inhibiting ephemeral plant growth in wet years and accelerating sand transport rates the linear dunefields are largely within the zone in which plant cover is sufficient to enforce low sand transport rates and in which there is a strong response of vegetation and sand transport to inter annual variation in rainfall both ephemeral plants mostly forbs and crust were found to respond rapidly to large 20 mm month rainfall events on millennial time scales the level of dune activity is controlled by vegetation cover and probably not by fluctuations of wind strength land use or extreme decadal time scale drought may destabilise dunes by removing perennial plant cover accelerating wind erosion

evolution of the bayramic magmatic complex northwestern anatolia abstract during the oligocene middle miocene period widespread magmatic activity developed in western anatolia following the continental collision between the sakarya continent and the tauride anatolide platform this produced both intrusive and extrusive rocks which appear to be associated in space and time as exemplified from the bayramic area in the bayramic area the magmatic activity started with the intrusion of the evciler granite and the coeval lower volcanic association this was followed by the development of the upper volcanic association these rock groups form collectively the bayramic magmatic complex which was generated under an on going north south compressional regime the bayramic magmatic complex has a subalkaline composition displaying a calcalkaline trend trace elements and ree contents resemble to island arc and collision related magmas according to the isotope values the bayramic magmatic complex was derived from the magmas of lithospheric mantle origin which were later contaminated while passing through the thick continental crust in a post collisional tectonic setting during the oligocene early miocene period the latest product of the magmatism is the late miocene pliocene basalt lavas their geochemical properties are clearly different from the oligocene early miocene magmatic rocks the basalts were generated when the north south compression gave way to the north south extensional regime

petrologic case for eocene slab breakoff during the indo asian collision the greater himalayan sequence is the metamorphic core of the himalaya and has been a focus of considerable study yet its petrologic evolution remains controversial pre oligocene metamorphism was nearly obliterated by miocene metamorphism and melting which many workers ascribe to shear heating unusually high concentrations of radioactive elements accompanying burial and or several kilometers of miocene exhumation due to extensional faulting sparse oligocene to eocene ages are often assigned to a tectonically unspecified event an alternative slab breakoff model subduction of greater himalayan rocks to 100 km depth in the eocene followed by buoyant extrusion due to decoupling of the oceanic lithosphere has also been proposed based on rare eocene eclogites but without explanation of miocene melting or metamorphic petrogenesis we argue that slab breakoff readily explains the eocene eclogites miocene partial melts and late eocene k rich magmas in southeastern tibet and that metamorphic and plutonic ages help define the timing and rates of breakoff and extrusion this model implies that 1 much of the greater himalayan sequence was subducted to depths greater than commonly considered 2 fluid absent decompression melting at 30 35 km depth was the consequence of as much as 100 km of extrusion rather than radioactive heating or a smaller crustal level extensional or erosional event and 3 eruption of eocene k rich tibetan plateau lavas has no implication for topography of the tibetan plateau

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

genesis of collision volcanism in eastern anatolia turkey late cenozoic volcanism in eastern anatolia extends in a broad sw ne trending belt across the arabia eurasia collision zone from the arabian foreland basin in the southwest and to the kars plateau and lesser caucasus in the northeast foreland volcanism is dominated by basaltic shield and fissure eruptions of transitional tholeiitic alkaline composition volcanism on the thickened crust north of the bitlis thrust zone varies from the mildly alkaline volcano nemrut and older mus volcanics in the south through the transitional calc alkaline alkaline volcanoes bingol and suphan and the alkaline volcano tendurek to the calc alkaline volcano ararat and older kars plateau volcanics in the north isotope sr nd and trace element systematics indicate that the lavas from the foreland were derived from the mantle lithosphere of the arabian continent which had been enriched by small volumes of asthenospheric melts over a period of time and that lavas from the alkaline volcanic area around mus and the volcanoes nemrut and tendurek north of the bitlis thrust zone were derived from a lithospheric source of similar composition either from the same underthrust arabian continent or from the bitlis massif microcontinent by contrast the transitional lavas from bingol and suphan and the calc alkaline lavas from ararat and kars were derived from lithosphere carrying a distinct subduction signature inherited from pre collision subduction events positive correlations between 87sr 86sr and sio2 and rb nb and sio2 in the alkaline and transitional lavas suggest that combined assimilation and fractional crystallization was an important process within at least part of the thickened crust of the collision zone trace element covariation diagrams such as y rb indicate the importance of hornblende crystallization at depth and orthopyroxene at shallow levels within the calc alkaline provinces in contrast to the consistently anhydrous crystallization sequences of the alkaline lavas trace element diagrams based on the covariation of compatible and incompatible elements point to moderate low degrees of partial melting with residual clinopyroxene throughout and residual garnet in the foreland province consideration of mineral stabilities mantle solidi and geothermal gradients before and after collision suggest that lithospheric thickening should both increase the thickness of metasomatized lithosphere and depress the metasomatized zone to greater depths probably beneath the amphibole and dolomite breakdown curves perturbation of the thickened lithosphere by delamination of the thermal boundary layer perhaps coupled with local stretching associated with pull apart basins on strike slip fault systems is then sufficient to generate melt the composition of that melt being largely dependent on the enrichment history of the lithosphere in question in eastern anatolia volcanism appears to have started between about 8 and 6 ma ago some 5 ma after the start of rapid uplift of the east anatolian plateau

a comparative analysis of nebkhas in central tunisia and northern burkina faso this paper reports a comparative analysis of nebkha morphology in central tunisia and northern burkina faso based on a total of 473 measured nebkhas nebkhas are mounds composed of wind borne sediment that accumulated around shrubs the size of the mounds was measured by height h and a horizontal component l the latter being the mean of the length and width of the mound in the tunisian data set three trends of development of the mounds were distinguished for ziziphus lotus nebkhas initially the height increases linearly with the increase in the horizontal component until it reaches about 17 m when the horizontal component exceeds 17 m the height stabilizes before a decreasing trend of the height occurs these results provided the basis for mathematical modelling of nebkha development a non linear and a linear fit were compared and a second order polynomial function was found to best fit the data on nebkha size from tunisia the results indicate that nebkhas have three stages of development a growing a stabilizing and a degrading stage the model was applied to data on acacia sp nebkhas and balanites aegyptiaca nebkhas from burkina faso with good results the non linear fit was slightly better than the linear fit nebkhas exist at all three stages of development in tunisia whereas burkina faso has nebkhas that are mainly at the growing stage these differences are a function of time lag in land degradation between the two study areas because the wind transport of sediment and the sediment supply are highly related to the density of the vegetation cover in semiarid areas this conclusion in further supported by dating of nebkhas and of historical and recent vegetation changes in the study areas reported in the literature the results show that differences in plant ecologies however are also very important for the rate of development of nebkhas which is demonstrated by the much faster growth of balanites nebkhas as compared to acacia nebkhas even though they occur in the same type of environment

gravity and magnetic expression of the san leandro gabbro with implications for the geometry and evolution of the hayward fault zone northern california the hayward fault one of the most hazardous faults in northern california trends north northwest and extends for about 90 km along the eastern san francisco bay region at numerous locations along its length distinct and elongate gravity and magnetic anomalies correlate with mapped mafic and ultramafic rocks the most prominent of these anomalies reflects the 16 km long san leandro gabbroic block inversion of magnetic and gravity data constrained with physical property measurements is used to define the subsurface extent of the san leandro gabbro body and to speculate on its origin and relationship to the hayward fault zone modeling indicates that the san leandro gabbro body is about 3 km wide dips about 75 80 northeast and extends to a depth of at least 6 km one of the most striking results of the modeling which was performed independently of seismicity data is that accurately relocated seismicity is concentrated along the western edge or stratigraphically lower bounding surface of the san leandro gabbro the western boundary of the san leandro gabbro block is the base of an incomplete ophiolite sequence and represented at one time a low angle roof thrust related to the tectonic wedging of the franciscan complex after repeated episodes of extension and attenuation the roof thrust of this tectonic wedge was rotated to near vertical and in places the strike slip hayward fault probably reactivated or preferentially followed this preexisting feature because earthquakes concentrate near the edge of the san leandro gabbro but tend to avoid its interior we qualitatively explore mechanical models to explain how this massive igneous block may influence the distribution of stress the microseismicity cluster along the western flank of the san leandro gabbro leads us to suggest that this stressed volume may be the site of future moderate to large earthquakes improved understanding of the three dimensional geometry and physical properties along the hayward fault will provide additional constraints on seismic hazard probability earthquake modeling and fault interactions that are applicable to other major strike slip faults around the world manuscript received 11 january 2002

crystallization conditions and compositional variations of silicate and sulfide minerals in the pb zn skarn deposits biga peninsula nw turkey abstract the biga peninsula nw turkey is an important sector of the tethyan metallogenic belt in addition to au and ag this region hosts several pb zn cu fe and mo deposits pb zn skarn mineralizations in the biga peninsula biga pb zn skarn are bounded by carbonate lenses in the metamorphic rocks and localized along the regional faults and at the contact between carbonate units and igneous metamorphic rocks the primary ore minerals are galena sphalerite chalcopyrite pyrite arsenopyrite magnetite and hematite ore bearing altered rocks are composed primarily of calc silicate alteration minerals including both prograde grossular andradite garnets and johannsenite hedenbergite pyroxenes and retrograde epidote chlorite quartz and calcite assemblages the garnet composition is a solid solution with

relationships between very high pressure subduction complex assemblages and intrusive granitoids in the tavsanli zone sivrihisar massif central anatolia abstract the sivrihisar massif of central anatolia exposes blueschist and eclogite facies metasedimentary and metabasaltic rocks in close association with granitoid plutons the massif is located within the tavsanli zone the subducted and exhumed northern continental margin of the anatolide tauride block the relationship of the very high pressure assemblages to co existing granitoid plutonic bodies kaymaz and sivrihisar is unclear as the region can be considered the type locality for the entrainment of excess argon in k bearing minerals samples from its granitoids and a subduction complex assemblage were collected imaged with cathodoluminescence cl and dated using zircon u pb in situ in thin section ion microprobe methods the granitoids are heterogeneous as evidenced by cl images and geochemical variations finer grained sivrihisar samples are syenite and show plagioclase replacing k feldspar whereas coarser grained rocks are monzonite and show the opposite reaction our samples of the kaymaz granitoids are extremely si rich 82 97 wt sio 2 and have experienced sericitization cl images of both granitoids show evidence for fluid interactions at both the subsolidus and lower temperature stages in their tectonic history subduction along the tavsanli zone was ongoing during the early to late cretaceous and entrained zircons with igneous zonation in cl that crystallized as early as the paleoproterozoic sivrihisar massif granitoids record zircon crystallization from the late cretaceous to early oligocene here we present a model in which the sivrihisar and kaymaz melts source from a subducting slab along the afyon zone further to the south and mix with an igneous component generated during decompression due to break off of the tavsanli slab the model speculates that the tavsanli zone is the northernmost segment of an amalgamation of stacked subduction zones that transition in activity from north to south over time

evidence for a supershear transient during the 2002 denali fault earthquake elastodynamic considerations suggest that the acceleration of ruptures to supershear velocities is accompanied by the release of rayleigh waves along the fault from the stress breakdown zone these waves generate a secondary slip pulse trailing the rupture front but manifest almost entirely in ground motion perpendicular to the fault in the near source region we construct a spontaneously propagating rupture model exhibiting these features and use it to explain ground motions recorded during the 2002 denali fault earthquake at pump station 10 located 3 km from the fault we show that the initial pulses on both the fault normal and fault parallel components are due to the supershear stress release on the fault whereas the later arriving fault normal pulses result from the trailing subshear slip pulse on the fault online material mpeg movies of rupture history and ground motion

dune mobility and vegetation cover in the southwest kalahari desert as part of a wider project investigating the palaeoenvironmental significance of partially vegetated linear dunes in the southwest kalahari data collected in the latter part of 1992 concerning dune movement and vegetation cover suggest that sediment transport is occurring on some dune surfaces and that the majority of surface activity occurs on the crests and upper slopes of the dunes the data suggest that the limiting variables on surface sediment movement vary on different parts of a dune on interdunes and lower dune slopes the primary limiting variable is available wind energy while on dune crests and upper slopes it is vegetation cover ground cover by litter has much greater importance in protecting the surface sediment from erosion than rooted vegetation from individual data points no evidence is found to support a threshold vegetation cover below which sediment movement occurs rather a gradient of activity is suggested whereby a reduction in vegetation cover increases the potential for sediment movement and surface change however dunes with differing amounts of mean vegetation cover display differing degrees of surface activity and at this scale a vegetation cover threshold in the region of 14 per cent may be recognized

observed and simulated ground motions in the san bernardino basin region for the hector mine california earthquake during the m w 7 1 hector mine earthquake peak ground velocities recorded at sites in the central san bernardino basin region were up to 2 times larger and had significantly longer durations of strong shaking than sites just outside the basin to better understand the effects of 3d structure on the long period ground motion response in this region we have performed finite difference simulations for this earthquake the simulations are numerically accurate for periods of 2 sec and longer and incorporate the detailed spatial and temporal heterogeneity of source rupture as well as complex 3d basin structure here we analyze three models of the san bernardino basin model a with structural constraints from gravity and seismic reflection data model f water well and seismic refraction data and the southern california earthquake center version 3 model hydrologic and seismic refraction data models a and f are characterized by a gradual increase in sediment thickness toward the south with an abrupt step up in the basement surface across the san jacinto fault the basin structure in the scec version 3 model has a nearly uniform sediment thickness of 1 km with little basement topography along the san jacinto fault in models a and f we impose a layered velocity structure within the sediments based on the seismic refraction data and an assumed depth dependent v p v s ratio sediment velocities within the scec version 3 model are given by a smoothly varying rule based function that is calibrated to the seismic refraction measurements due to computational limitations the minimum shear wave velocity is fixed at 600 m sec in all of the models ground motion simulations for both models a and f provide a reasonably good match to the amplitude and waveform characteristics of the recorded motions in these models surface waves are generated as energy enters the basin through the gradually sloping northern margin due to the basement step along the san jacinto fault the surface wave energy is confined to the region north of this structure consistent with the observations the scec version 3 model lacking the basin geometry complexity present in the other two models fails to provide a satisfactory match to the characteristics of the observed motions our study demonstrates the importance of using detailed and accurate basin geometry for predicting ground motions and also highlights the utility of integrating geological geophysical and seismological observations in the development and validation of 3d velocity models

a reanalysis of the hypocentral location and related observations for the great 1906 california earthquake we determine probabilistic hypocentral locations for the foreshock and mainshock of the great 1906 california earthquake through reanalysis of arrival time observations in conjunction with modern velocity models and advanced event location techniques we obtain two additional observations for the mainshock and one for the foreshock that were not used in previous location studies using a robust likelihood function for event location we generate a usable subset of the predominantly unreliable teleseismic readings and determine new wave type identifications for some of the local and teleseismic readings our locations are much better constrained than those of earlier studies even though we do not assume that the epicenter lies on the san andreas fault as did previous authors we confirm the conclusions of earlier studies that the local and teleseismic arrival time observations can be explained by a single foreshock focus and a single mainshock focus on the san andreas fault and that there is no single unique hypocenter that satisfies all available local observations the maximum likelihood point latitude 37 78 n longitude 122 51 w for our preferred mainshock location indicates a hypocenter to the west of san francisco close to the san andreas fault zone this hypocenter has a 68 confidence error of about 8 km parallel to the san andreas fault and about 24 km perpendicular to the fault and a depth in the midcrust of about 12 7 km the closest point on the san andreas fault to this hypocenter lies about 10 km to the northwest of the widely accepted mainshock epicenter of bolt 1968 our mainshock location is consistent with the association of initial rupture of the 1906 mainshock with a dilatational right bend or step over in the submerged san andreas fault system offshore of the golden gate our foreshock location is less well constrained than our mainshock location but is consistent with the foreshock hypocenter being at the same location as the mainshock hypocenter online material visualization of 3d probabilistic hypocentral locations associated with the 1906 earthquake

geology of the ignimbrites and the associated volcano plutonic complex of the ezine area northwestern anatolia abstract the ezine region is located in the northwestern part of anatolia where young granitic and volcanic rocks are widespread and show close spatial and temporal association in this region magmatism began with the kestanbol granite which intruded into metamorphic basement rocks and formed contact metamorphic aureole to the east and southeast the pluton is surrounded by hypabyssal rocks which in turn are surrounded by volcanic associations the volcanic rocks may be divided into two main groups on the basis of their lithological properties lavas and lahar deposits dominate the northern sector while ignimbrites dominate the southern sector the ignimbrite eruptions were formed partly coevally with the plutonic and the associated volcanic rocks during the early miocene they appear to have been associated in a caldera collapse environment geochemical properties of the plutonic and the associated volcanic assemblages indicate that the magmas are hybrid and co genetic and were formed from a similar mantle source under a compressional regime prior to the opening of the present e w trending graben of the aegean western anatolian region

ground motion modeling of the 1906 san francisco earthquake part i validation using the 1989 loma prieta earthquake we compute ground motions for the beroza 1991 and wald et al 1991 source models of the 1989 magnitude 6 9 loma prieta earthquake using four different wave propagation codes and recently developed 3d geologic and seismic velocity models in preparation for modeling the 1906 san francisco earthquake we use this well recorded earthquake to characterize how well our ground motion simulations reproduce the observed shaking intensities and amplitude and durations of recorded motions throughout the san francisco bay area all of the simulations generate ground motions consistent with the large scale spatial variations in shaking associated with rupture directivity and the geologic structure we attribute the small variations among the synthetics to the minimum shear wave speed permitted in the simulations and how they accommodate topography our long period simulations on average under predict shaking intensities by about one half modified mercalli inten sity mmi units 25 35 in peak velocity while our broadband simulations on average under predict the shaking intensities by one fourth mmi units 16 in peak velocity discrepancies with observations arise due to errors in the source models and geologic structure the consistency in the synthetic waveforms across the wave propagation codes for a given source model suggests the uncertainty in the source parameters tends to exceed the uncertainty in the seismic velocity structure in agree ment with earlier studies we find that a source model with slip more evenly distributed northwest and southeast of the hypocenter would be preferable to both the beroza and wald source models although the new 3d seismic velocity model improves upon previous velocity models we identify two areas needing improvement nevertheless we find that the seismic velocity model and the wave propagation codes are suitable for modeling the 1906 earthquake and scenario events in the san francisco bay area online material modified mercalli intensities and velocity waveforms and a movie of simulated wave propagation