magnetostratigraphical dating of loess deposits in china the age of chinese loess deposits has long been disputed biostratigraphical and earlier magnetostratigraphical investigations placed the entire loess formation within the pleistocene the new palaeomagnetic measurements reported here on a bore hole section near lochuan shaanxi province suggest a clearly defined magnetic polarity zonation which extends below the olduvai subchron a late pliocene age of 2 4 myr is assigned to the oldest loess sediments measured the intensity variations of natural remanent magnetization nrm and low field magnetic susceptibility are indicative of climatic changes during loess deposition

changes in the magnitude frequency b value prior to large m 6 0 earthquakes in japan on the basis of akaike s bayesian information criterion abic a new method of estimating temporal and spatial variations in the magnitude frequency relation b value is developed the space time volume studied is divided into a number of segments having equal volumes for which b values are estimated the smoothness of the estimated b value is guaranteed by the introduction of a prior distribution the parameters of the prior distribution are chosen in such a way as to minimize the abic this method is employed to study the temporal and spatial variations of b values for microearthquake activity in the kanto tokai and tottori areas where seven earthquakes of m 6 0 have recently occurred the temporal variation of b values for the source region of the western nagano earthquake sep 1984 m 6 8 in the tokai area shows a decrease in b values about 2 years before the occurrence of the main shock similar findings before the southwestern ibaraki feb 1983 m 6 0 the southern ibaraki oct 1985 m 6 0 and the chiba dec 1987 m 6 7 earthquakes in the kanto area and the tottori earthquake oct 1984 m 6 2 in the tottori area were obtained these findings are confirmed by a precursor analysis pa in which effects of aftershocks are eliminated using a quantitative definition temporal variations of b values are classified into three groups increase decrease and no change the space time volume of decrease accounts for approximately 10 of the total volume for a period before the occurrence of earthquakes the decrease appears more frequently than might be expected from random chance the results suggest that the decrease in b values is a promising candidate to act as a precursory phenomena

rates of crustal deformation in western turkey as deduced from major earthquakes abstract western turkey has undergone dominantly n s extension probably since the late miocene this extensional regime caused the formation of e w trending grabens and similarly orientated normal faults the rates of deformation of the seismogenic layer caused by the major earthquakes ms 5 5 during the period between 1943 and 1983 are calculated for western anatolia this region is first analysed as a single system and then divided into two provinces namely the marmara and southwestern anatolian provinces which are investigated as two separate seismotectonic units the dominant mode of deformation in the marmara province is amounting to right lateral displacement 24 0 mm yr other modes of upper crustal deformation in this province can be explained by an average 7 1 mm yr n s extension 10 0 mm yr e w contraction and 0 13 mm yr thinning of a 10 km seismogenic layer the dominant mode of deformation in southwestern anatolia is about 13 5 mm yr extension in the n s direction this region is also undergoing e w extension of about 3 6 mm yr justifying the separation of marmara and southwestern anatolian provinces as two different seismotectonic provinces the average rate of thinning of the seismogenic layer in this area is 0 5 mm yr which is consistent with large scale normal faulting observed here it is found that n s extension in western anatolia increases from north to south while e w compression in the marmara province changes to e w extension in southwestern anatolia it is suggested that these kinematics may explain the present bending of the north anatolian transform forming a transtensional basin between the marmara and southwestern anatolian provinces

the age of the buyuk menderes graben west turkey and its tectonic implications the age of formation of the buyuk menderes graben middle burdigalian middle serravallian is earlier than previously considered tortonian this supports the contention of seyitog lu scott that north south extensional tectonics in west turkey commenced at the latest during early miocene time following a palaeogene compression

fractal dimension and b value on creeping and locked patches of the san andreas fault near parkfield california we tested the hypotheses 1 that the fractal dimension d of hypocenters are different in a locked and a creeping segment of the san andreas fault and 2 that the relationship d 2b holds approximately where b is the slope of the frequency magnitude relationship the test area was the 30 to 50 km fault segment north of park eld for which two earthquake catalogs exist the borehole high resolution seismic network data and the u s geological survey data which have a minimum magnitude of completeness of mc 0 4 and mc 1 0 1 2 respectively the relative location errors in the two catalogs are estimated as 0 25 km and less than 1 km respectively the periods of high quality data available extend from 1987 to 1998 5 and 1981 to 2000 2 respectively furnishing 2609 and 3775 events for analysis in the two catalogs in the locked part 0 5 b 0 7 and 0 96 d 1 14 whereas in the creeping segment 1 1 b 1 6 and 1 45 d 1 72 however the spatial distribution of the hypocenters in the creeping segment is not well approximated by a fractal distribution we conclude 1 that the frequency magnitude distribution as described by b as well as the fractal dimension d are different in the locked and creeping segments near park eld 2 that the spatial distribution in the creeping segment is not well approximated by a fractal distribution and 3 that the relationship d 2b holds in the locked segment where both parameters can be measured accurately thus we propose that the heterogeneity of seismogenic volumes lead to differences in d and b and that these differences where established by high quality data may furnish clues concerning properties of fault zones

gradual unlocking of plate boundary controlled initiation of the 2014 iquique earthquake a long foreshock series unlocked the south american plate boundary until eventually initiating the m 8 1 iquique chile earthquake two groups publishing in this issue of nature analyse the seismic context of the iquique earthquake that occurred off the coast of northern chile on 1 april 2014 in a seismic zone that had been quiescent since a significant event in 1877 gavin hayes et al identify areas of remaining or elevated earthquake hazard along the megathrust fault in the region and conclude that the 2014 iquique event was not the earthquake that had been anticipated given that significant sections of the northern chile subduction zone have not ruptured in almost 150 years they suggest that it is likely that future megathrust earthquakes will occur south and potentially north of the 2014 iquique sequence bernd schurr et al show that the april 2014 earthquake broke a central fraction of the northern chile seismic gap the last major segment of the south american plate boundary that had yet to rupture in the past century from july 2013 up to the april earthquake they identify three seismic clusters along this part of the plate boundary each lasting a few weeks with earthquakes of increasing peak magnitudes they conclude that these seismic clusters and their slip transients reflect a gradual weakening of the central part of the seismic gap that was instrumental in initiating the final failure on 1 april 2014 northern chile was struck by a magnitude 8 1 earthquake following a protracted series of foreshocks the integrated plate boundary observatory chile monitored the entire sequence of events providing unprecedented resolution of the build up to the main event and its rupture evolution here we show that the iquique earthquake broke a central fraction of the so called northern chile seismic gap the last major segment of the south american plate boundary that had not ruptured in the past century1 2 since july 2013 three seismic clusters each lasting a few weeks hit this part of the plate boundary with earthquakes of increasing peak magnitudes starting with the second cluster geodetic observations show surface displacements that can be associated with slip on the plate interface these seismic clusters and their slip transients occupied a part of the plate interface that was transitional between a fully locked and a creeping portion leading up to this earthquake the b value of the foreshocks gradually decreased during the years before the earthquake reversing its trend a few days before the iquique earthquake the mainshock finally nucleated at the northern end of the foreshock area which skirted a locked patch and ruptured mainly downdip towards higher locking peak slip was attained immediately downdip of the foreshock region and at the margin of the locked patch we conclude that gradual weakening of the central part of the seismic gap accentuated by the foreshock activity in a zone of intermediate seismic coupling was instrumental in causing final failure distinguishing the iquique earthquake from most great earthquakes finally only one third of the gap was broken and the remaining locked segments now pose a significant increased seismic hazard with the potential to host an earthquake with a magnitude of 8 5

temporal and spatial variations of gutenberg richter parameter and fractal dimension in western anatolia turkey abstract the temporal and spatial variations of gutenberg richter parameter b value and fractal dimension dc during the period 1900 2010 in western anatolia was investigated the study area is divided into 15 different source zones based on their tectonic and seismotectonic regimes we calculated the temporal variation of b and dc values in each region using zmap the temporal variation of these parameters for the prediction of major earthquakes was calculated the spatial distribution of these parameters is related to the stress levels of the faults we observed that b and dc values change before the major earthquakes in the 15 seismic regions to evaluate the spatial distribution of b and dc values 0 50 0 50 grid interval were used the b values smaller than 0 70 are related to the aegean arc and eskisehir fault the highest values are related to sultandagi and sandikli faults fractal correlation dimension varies from 1 65 to 2 60 which shows that the study area has a higher dc value the lowest dc values are related to the joining area between aegean and cyprus arcs burdur fethiye fault zone some have concluded that b values drop instantly before large shocks others suggested that temporally stable low b value zones identify future large earthquake locations the results reveal that large earthquakes occur when b decreases and dc increases suggesting that variation of b and dc can be used as an earthquake precursor mapping of b and dc values provide information about the state of stress in the region i e lower b and higher dc values associated with epicentral areas of large earthquakes

some premonitory phenomena of the 1995 hyogo ken nanbu kobe earthquake seismicity b value and fractal dimension abstract this paper presents a detailed and complex analyses of the spatio temporal evolution of seismic activity between 1976 and 1998 in a broad area surrounding the epicentre of the 1995 hyogo ken nanbu kobe earthquake as well as in the source area various precursory changes in seismicity such as quiescence followed by increased seismic activity b value and fractal dimension correlation dimension d2 anomalies appear approximately two years before the occurrence of the major event an increased level of background seismicity is clearly observed after the occurrence of the kobe earthquake particularly in the northeast extension of the source area all these anomalous changes in seismic activity before and after the occurrence of the 1995 hyogo ken nanbu earthquake appear in a relatively large region surrounding the epicentre of the main shock as well as in the source area

high resolution record of northern hemisphere climate extending into the last interglacial period high resolution record of northern hemisphere climate extending into the last interglacial period

modeling of seismic hazard for turkey using the recent neotectonic data abstract recent developments in the neotectonic framework of turkey introduced new tectonic elements necessitating the reconstruction of turkey s seismic hazard map in this regard 14 seismic source zones were delineated maximum earthquake magnitudes for each seismic zones were determined using the fault rupture length approximation regression coefficients of the earthquake magnitude frequency relationships for the seismic zones were compiled mostly from earlier works along with these data a strong ground motion attenuation relationship developed by joyner and boore joyner w b boore d m 1988 measurement characterization and prediction of strong ground motion earthquake engineering and soil dynamics 2 recent advances ground motion evaluation pp 43 102 was utilized to model the seismic hazard for turkey using the probabilistic approach for the modeling the earthquake location uncertainty concept was employed a grid of 5106 points with 0 2 intervals was constituted for the area encompassed by the 25 46 e longitudes and 35 43 n latitudes for the return periods of 100 and 475 years the peak horizontal ground acceleration pga in bedrock was computed for each grid point isoacceleration maps for the return periods of 100 and 475 years were constructed by contouring the pga values at each node

3 d spatial variation of b values of magnitude frequency distribution beneath the kanto district japan summary a method is developed for estimation and interpolation of 6 values in space a 3 d spline function is considered for the logarithm of the 6 value at each location in the space since many parameters for the spline coefficients are required to obtain a sensible estimate of the spatial variation of 6 values we consider the penalized log likelihood with the standard roughness penalties for the spline function further the error bands of the b value estimation at each location can be calculated using the current method the spatial distribution of 6 values beneath the kanto district down to the depth of 100km is determined based on hypocentral data of microearthquakes from the kanto tokai observational network of the national research center for disaster prevention the stability of the estimated pattern is checked by comparing with the results using alternative cut off magnitudes this is further ensured by comparison with the result obtained by an alternative model using equally divided blocks on the whole the vertical change in 6 value is greater than the horizontal one it is high in the crust of the eurasian plate especially above the upper boundary of the subducting pacific plate and in the northwest part or the volcanic area in the kanto district a steep decrease of the 6 values is seen to take place in perpendicular direction to the subducting pacific plate boundary also a similar change is seen in the boundary between the eurasian and phillippine sea plates especially beneath the southern part of the kanto plain the 6 value is low in the upper boundary of the subducting plates but high in the lower plane of the double seismic zone in the pacific plate it appears that even within a narrow area of aftershocks the 6 value can change significantly it is also found that the variation of the 6 value estimate is in good agreement with the structure of seismic wave fractional velocity perturbations the regions of high and low 6 values correspond respectively to the lower and higher parts of the p wave velocity the similar relationship is seen with the spatial structure of the seismic wave attenuation

the b value before the 6th august 1988 india myanmar border region earthquake a case study abstract smith 1981 1986 and wyss et al 1990 have observed that intermediate term quiescence is often associated with an increasing b value this study pertains to the temporal behaviour of the b value before the earthquake of 6th august 1988 which occurred in the india myanmar border region the b value in the preparation zone of the earthquake 21 25 5 n 93 96 e as identified by gupta and singh 1986 1989 is found to have increased gradually from 1976 to a maximum value of 1 33 during july 1987 followed by a short term drop before the occurrence of the earthquake the quiescence period observed by gupta and singh 1986 1989 for this earthquake is better reflected by the intermediate term increase in the b value a drop in the mean magnitude since 1978 is supported by a cusum plot

evidence from the gediz graben for episodic two stage extension in western turkey western turkey falls within a wide belt of nne ssw directed active continental extension generally similar to the basin and range province of the usa it comprises a zone of wnw ese trending major grabens detailed study of the gediz graben reveals two contrasting infills that represent two distinct extensional stages separated by a short phase of compression the older infill consists of an 800 m thick folded and exhumed continental sedimentary sequence with intercalated calc alkaline volcanics it accumulated in a basin formed in the northern hanging wall of a detachment fault during miocene early pliocene times the younger infill rests on the older infill with angular unconformity and consists of about 170 m of undeformed terraced continental sediments and basaltic lavas it accumulated during plio quaternary times in an asymmetric graben bounded by step like normal faults this later extension was probably triggered by the commencement of sea floor spreading along the red sea in early pliocene times and has persisted to the present almost all the grabens in western turkey are best explained by this episodic two stage graben model with an intervening phase of short term compression which differs from the progressive evolution inferred for the basin and range province of the usa

regional variations and correlations of gutenberg richter parameters and fractal dimension for the different seismogenic zones in western anatolia we investigated the regional variations of gutenberg richter g r parameters a and b and fractal correlation dimension dc and relations among these parameters for the different regions in western anatolia wa the whole examined area 26 33 e 33 40 5 n is divided into 15 different seismogenic regions based on their tectonic and seismotectonic regimes we used database including 69 182 earthquakes for the instrumental period from 1900 to 2011 we calculated b value which is the slope of the frequency magnitude gutenberg richter relationship from maximum likelihood method ml and dc value which is the slope of log10c r versus log10r from correlation integral using the least squares ls method computed values for 15 different seismogenic regions are mapped using different color scale for different range of values of b and dc regional distributions of these parameters reveal information about regional variation of stress level and geological complexity we concluded aegean arc and aegean islands aliaga fault and buyuk menderes graben the most vulnerable regions for occurrence of the large earthquakes in wa considering the computed lowest b values and the highest dc values in these regions since dc b values are the highest in these regions this ratio may be used as an indicator of earthquake hazard levels of different seismogenic zones in a studied region an effort is made to find relationships between the g r parameters and fractal dimension we observed negative correlation between dc and b values and positive correlation between dc and a b values for different regions of wa we observed that the relationship between a b and dc can be used for seismicity earthquake risk and hazard studies because of the computed high correlation coefficient and fewer scattering of these parameters

gps constraints on africa nubia and arabia plate motions summary we use continuously recording gps cgps and survey mode gps sgps observations to determine euler vectors for relative motion of the african nubian arabian and eurasian plates we present a well constrained eurasia nubia euler vector derived from 23 igs sites in europe and four cgps and three sgps sites on the nubian plate 0 95 4 8 n 21 8 4 3 e 0 06 0 005 myr 1 we see no significant 1m m yr 1 internal deformation of the nubian plate the gps nubian eurasian euler vector differs significantly from nuvel 1a 21 0 4 2 n 20 6 0 6 e 0 12 0 015 myr 1 implying more westward motion of africa relative to eurasia and slower convergence in the eastern mediterranean the arabia eurasia and arabia nubia gps euler vectors are less well determined based on only one cgps and three sgps sites on the arabian plate the preliminary arabia eurasia and arabia nubia euler vectors are 27 4 1 0 n 18 4 2 5 e 0 40 0 04 myr 1 and 30 5 1 0 n 25 7 2 3 e 0 37 0 04 myr 1 respectively the gps arabia nubia euler vector differs significantly from nuvel 1a 24 1 1 7 n 24 0 3 5 e 0 40 0 05 myr 1 but is statistically consistent at the 95 per cent confidence level with the revised euler vector reported by chu gordon based on a re evaluation of magnetic anomalies in the red sea 31 5 1 2 n 23 0 2 7 e 0 40 0 05 myr 1 the motion implied in the gulf of aqaba and on the dead sea fault dsf by the new gps nubia arabia euler vector i e ignoring possible sinai block motion and possible internal plate deformation grades from pure left lateral strike slip in the gulf and on the southern dsf with increasing compression on the central and northern dsf with relative motion increasing from 5 6 to 7 5 mm yr 1 1m m yr 1 from south to north along the northern dsf i e north of the lebanon restraining bend motion is partitioned between 6 1m m yr 1 left lateral motion parallel to the fault trace and 4 1m m yr 1 faultnormal compression relative motions on other plate boundaries including the anatolian and aegean microplates derived from the gps euler vectors agree qualitatively with the sense of motion indicated by focal mechanisms for large crustal earthquakes m 6 where data are available on fault slip rates on plate bounding faults north anatolian fault east anatolian fault dead sea fault red sea rift they are generally lower than but not significantly different from the full plate motion estimates suggesting that the majority of relative plate motion is accommodated on these structures

holocene east asian summer monsoon records in northern china and their inconsistency with chinese stalagmite δ18o records abstract monsoon precipitation over china exhibits large spatial differences it has been found that a significantly enhanced east asian summer monsoon easm is characterized by increased rainfall in northern china and by reduced rainfall in southern china and this relationship occurs on different time scales during the holocene this study presents results from a diverse range of proxy paleoclimatic records from northern china where precipitation variability is traditionally considered as an easm proxy our aim is to evaluate the evolution of the easm during the holocene and to compare it with all of the published stalagmite 18 o records from the asian monsoon region in order to explore the potential mechanism s controlling the chinese stalagmite 18 o we found that the intensity of the easm during the holocene recorded by the traditional easm proxy of moisture or precipitation records from northern china is significantly different from the chinese stalagmite 18 o records the easm maximum occurred during the mid holocene challenging the prevailing view of an early holocene easm maximum mainly inferred from stalagmite 18 o records in eastern china in addition all of the well dated holocene stalagmite 18 o records covering a broad geographical region exhibit a remarkably similar trend of variation and are statistically well correlated on different time scales thus indicating a common signal however in contrast with the clear consistency in the 18 o values in all of the cave records both instrumental and paleoclimatic records exhibit significant spatial variations in rainfall on decadal to centennial time scales over eastern china in addition both paleoclimatic records and modeling results suggest that holocene east asian summer monsoon precipitation reached a maximum at different periods in different regions of china thus the stalagmite 18 o records from the easm region should not be regarded as a reliable indicator of the strength of the east asian summer monsoon furthermore modern observations indicate that the moisture for precipitation in the east asian monsoon region is mainly derived from the indian ocean the moisture transport route from the indian ocean to the east asian monsoon region during the holocene is almost identical to that of modern precipitation therefore the strong correlation of 18 o records in the easm and indian summer monsoon ism regions and the similarity of the pattern of latitudinal changes in 18 o values in stalagmites and in modern meteoric precipitation along the water vapor transport route further suggests that the stalagmite 18 o records from the easm region are essentially a signal of the isotopic composition of precipitation which is determined mainly by changes in the 18 o of atmospheric vapor in the upstream source region over the indian ocean and indian monsoon region via the upstream depletion mechanism finally the main trends of the stalagmite 18 o records are strongly correlated with the known evolution of the ism and therefore these records reflect the history of the ism rather than that of the easm our findings support the conclusion that easm variability is mainly controlled by northern hemisphere summer insolation and was strongly modulated by ice volume during the last deglaciation and early holocene which delayed the response of the easm maximum to peak insolation forcing

variation in carbon isotopic composition over the past ca 46 000 yr in the loess paleosol sequence in central kazakhstan and paleoclimatic significance abstract we present a high resolution record of 13 c org variation from two loess sequences in central kazakhstan the variation shows that the vegetation was persistently dominated by c 3 plants over the past ca 46 000 yr the 13 c org signature was most likely an indicator of moisture and the moisture variation in central kazakhstan was associated with the precipitation in western europe the 13 c org indicated that moisture variation exhibited five stages decreasing during stage 1 ca 46 000 ca 31 500 yr bp increasing during stage 2 ca 31 500 ca 25 500 yr bp again decreasing during stage 3 ca 25 500 ca 19 000 yr bp fluctuating along a constant line during stage 4 ca 19 000 ca 5000 yr bp and increasing during stage 5 last ca 5000 yr our comparison demonstrated a general similarity between the 13 c org indicated moisture variation in central kazakhstan and the reconstructed precipitation variation in western europe the similarity implies that the moisture of the past ca 46 000 yr in central kazakhstan has been controlled or modulated by westerlies that brought water vapor from the north atlantic not only to western europe but also to central kazakhstan

a fractal model for crustal deformation abstract we hypothesize that crustal deformation occurs on a scale invariant matrix of faults for simplicity we consider a two dimensional pattern of hexagons on which strike slip faulting occurs the behavior of the system is controlled by a single parameter the fractal dimension deformation occurs on all scales of faults the fractal dimension determines the fraction of the total displacement that occurs on the first order or primary faults the value of the fractal dimension can be obtained from the frequency magnitude relation for earthquakes our results are applied to the san andreas fault system in central california earthquake studies give d 1 90 we associate the main strand of the san andreas fault with the primary faults of our fractal system we predict that the relative velocity across the main strand is 2 93 cm yr the remainder of the relative velocity of 5 5 cm yr between the pacific and north american plates occurs on higher order faults the predicted value is in reasonably good agreement with the value 3 39 0 29 cm yr obtained from geological studies

insolation values for the climate of the last 10 million years new values for the astronomical parameters of the earth s orbit and rotation eccentricity obliquity and precession are proposed for paleoclimatic research related to the late miocene the pliocene and the quaternary they have been obtained from a numerical solution of the lagrangian system of the planetary point masses and from an analytical solution of the poisson equations of the earth moon system the analytical expansion allows the direct determination of the main frequencies with their phase and amplitude numerical and analytical comparisons with the former astronomical solution ber78 are performed so that the accuracy and the interval of time over which the new solution is valid can be estimated the corresponding insolation values have also been computed this analysis leads to the conclusion that the new values are expected to be reliable over the last 5 ma in the time domain and at least over the last 10 ma in the frequency domain

seismicity and seismic hazard parameters evaluation in the island of crete and the surrounding area inferred from mixed data files abstract a study of the spatial distribution of seismicity and seismic hazard is undertaken for crete and the surrounding area cisa for the estimation of seismicity parameters cisa is divided in rectangular subregions by applying the centroid of strain energy technique we obtain seismicity parameter maps closely related to the tectonics of the area the b value from the magnitude frequency distribution is calculated by a maximum likelihood technique page 1968 bull seism soc am 58 1131 1168 as well as by gumbel s first asymptotic distribution of extreme values technique the b value shows consistent spatial variation along cisa for both techniques low b values are dominant in the western part of cisa while higher b values are present to the east side forming a pattern like a sleeping letter s this pattern may be attributed to the variation of the regional velocity of deformation finally we performed seismic hazard analysis for shallow and intermediate events from mixed historical and instrumental data files we estimated the regional maximum magnitude mmax as well as the other parameters like the activity rate of seismic events and the well known b parameter kijko and sellevoll 1989 bull seismol soc am 79 645 654

temporal variations in the fractal properties of seismicity in the north anatolian fault zone between 31 e and 41 e we investigate the nature of temporal variations in the statistical properties of seismicity associated with the north anatolian fault zone between longitudes 31 41 e during the instrumental period 1900 1992 temporal variations in the seismicb value and the fractal correlation dimensiondc of earthquake epicenters are examined for earthquakes of magnitudems 4 5 using sliding windows of 100 consecutive events b varies temporally between 0 6 and 1 0 anddc between 0 6 and 1 4 both representing significant fluctuations above the errors in measurement technique a strong negative correlation r 0 85 is observed betweenb anddc consistent with previous observation of seismicity in japan and southern california major events early in this century ms 7 are associated with lowb and highdc respectively consistent with greater stress intensity and greater spatial clustering of epicenters both implying a greater degree of stress concentration at this time

evidence for a constant b value above magnitude 0 in the southern san andreas san jacinto and san miguel fault zones and at the long valley caldera california the cumulative b value the slope of the gutenberg richter relationship between earthquake occurrence rate and magnitude is commonly found to be constant 1 network catalogues however reveal a decrease at small magnitudes 3 some recent studies have suggested that this decrease in b value is not just an artifact of catalogue incompleteness but that small earthquakes are really not as numerous as a constant b value extrapolated from larger events would predict brune allen 1967 recorded microseismicity in both the san andreas and san jacinto fault zones in southern california calculating that they were complete to magnitude 0 reyes et al 1975 performed a similar study of the san miguel fault zone baja california estimating completeness above magnitude 0 5 we compare the results of these studies with the occurrence rates of earthquakes on the same faults recorded by the southern california and resnor seismic networks the observed microseismicity rates are in good agreement with the rates predicted by extrapolating the b values of the larger earthquakes in a new microseismicity survey at the long valley caldera mammoth lakes california microearthquakes were recorded and counted within 24 km of stations clk and chs this study is estimated to be complete above 0 6 m at clk and 0 9 m at chs and the microseismicity rates are found to be in good agreement with the rate predicted by extrapolating the b value from the local network recorded seismicity the constant b value in the magnitude range 0 to 5 observed in all four areas considered is consistent with a scale invariant earthquake rupture process

effect of soil conditions on predicted ground motion case study from western anatolia turkey abstract we present a site effect study for the city of izmir western anatolia turkey local amplification was evaluated using state of practice tools ten earthquakes recorded at 16 sites were analysed using spectral ratios relative to a reference site horizontal to vertical spectral ratios and an inversion scheme of the fourier amplitude spectra of the recorded s waves seismic noise records were also used to estimate site effects the different estimates are in good agreement among them although a basic uncertainty of a factor of 2 seems difficult to decrease we used our site effect estimates to predict ground motion in izmir for a possible m6 5 earthquake close to the city using stochastic modelling site effects have a large impact on psv pseudospectral velocity where local amplification increases amplitudes by almost a factor of 9 at 1 hz relative to the firm ground condition our results allow identifying the neighbourhoods of izmir where hazard mitigation measurements are a priority task and will also be useful for planning urban development

association of the northern hemisphere circumglobal teleconnection with the asian summer monsoon during the holocene in a transient simulation this paper provides another look at the response of the asian summer monsoon asm to insolation forcing and oceanic feedback during the holocene using a fully coupled general circulation ocean atmosphere model forced by earth s orbital variations the model results revealed a recurrent circumglobal teleconnection cgt pattern in the summertime june july august mid latitude circulation of the northern hemisphere during the holocene the cgt index showed a decreasing trend before 5 ka bp and a slight increasing trend afterwards affected by the combined effects of summer insolation indian summer monsoon ism north atlantic and indian ocean western pacific ocean sea surface temperature sst the cgt showed a close relationship with asm precipitation and surface air temperature during the holocene and therefore could act as a bridge linking the asm to insolation high latitude forcing north atlantic sst and low latitude forcing tropical ocean sst we emphasize that the mid latitude atmospheri

a detailed study of the active crustal deformation in the aegean and surrounding area abstract a detailed study of the active crustal deformation in the aegean sea and surrounding area is presented the estimation of the deformation velocities is not performed in broad seismic zones but in seismogenic sources of limited spatial extent where the seismic energy is practically released in order to describe the spatial variations of the components of the strain rate tensor the deformation analysis is based on previous work where the seismicity and the available focal mechanisms are used separately for estimating the rate and shape of the deformation respectively the calculations were performed for 63 seismogenic sources identified in the aegean sea and surrounding area which belong to eight belts with an almost uniform orientation of the stress field along the coasts of albania and northwestern greece up to leukada island the collision of the adria plate with eurasia results in a compressional velocity of about 4 mm yr in a direction n49 e almost normal to the coast line the dextral movement with almost 3 cm yr along the cephalonia transform fault with strike n45 e is expressed as an almost equal extension and compression in n s and e w direction respectively along the convex outer part of the hellenic arc a crustal shortening of 1 3 cm yr is observed in a mean direction n34 e the direction of this shortening is almost constant from the southern ionian islands zakynthos up to rodos while the shortening rate does not significantly change from the outer sources to the inner ones the aegean sea and surrounding area is characterised by an extensional deformation the direction of the maximum extension in the northern part of this area shows an anticlockwise rotation from east to west thus this extension has a nne direction in northwestern turkey n11 e a nnw direction in central and northern greece as well as along the southern aegean volcanic arc and its extension to southwestern turkey n12 w and a wnw direction in the westernmost part of this extensional area n72 w the mean value of the extensional velocities in this area is 5 mm yr the northern part of asia minor and of the aegean sea is characterised by the dextral strike slip movement of about 2 cm yr of the north anatolian fault and its continuation in the northern aegean where this movement gradually decreases to about 6 mm yr the vertical crustal upper 10 km of the crust thickening is about 2 mm yr along the convex side of the hellenic arc and the vertical crustal thinning is about 1 mm yr in the aegean sea these values were obtained from the component u 33 of the velocity tensor

variation of east asian monsoon precipitation during the past 21 k y and potential co2 forcing paleoclimatic research can provide critical insight on causes of change in the east asian monsoon which influences the lives of 1 6 billion people today in this study we use paleoclimatic indexes from chinese loess deposits which have clear climatic implications and are independently dated to reconstruct the monsoon precipitation since 21 ka our results show that monsoon precipitation persistently decreased from 21 ka to ca 8 ka and increased after ca 8 ka with a precipitation peak at 8 3 ka these changes in east asian summer monsoon precipitation are synchronous with changes in high northern latitude ice volume ice cover and atmospheric co2 these new data suggest that variation of the monsoon precipitation was probably driven by co2 forced high northern latitude temperature changes shifting the location of the intertropical convergence zone that dominates monsoon precipitation our trace 21000 modeling experiment supports this interpretation

an evaluation of earthquake hazard potential for different regions in western anatolia using the historical and instrumental earthquake data we applied the maximum likelihood method produced by kijko and sellevoll bull seismol soc am 79 645 654 1989 bull seismol soc am 82 120 134 1992 to study the spatial distributions of seismicity and earthquake hazard parameters for the different regions in western anatolia wa since the historical earthquake data are very important for examining regional earthquake hazard parameters a procedure that allows the use of either historical or instrumental data or even a combination of the two has been applied in this study by using this method we estimated the earthquake hazard parameters which include the maximum regional magnitude hat m max the activity rate of seismic events and the well known hat b value which is the slope of the frequency magnitude gutenberg richter relationship the whole examined area is divided into 15 different seismic regions based on their tectonic and seismotectonic regimes the probabilities return periods of earthquakes with a magnitude m m and the relative earthquake hazard level defined as the index k are also evaluated for each seismic region each of the computed earthquake hazard parameters is mapped on the different seismic regions to represent regional variation of these parameters furthermore the investigated regions are classified into different seismic hazard level groups considering the k index according to these maps and the classification of seismic hazard the most seismically active regions in wa are 1 8 10 and 12 related to the aliaga fault and the buyuk menderes graben aegean arc and aegean islands

neotectonic structures in izmir gulf and surrounding regions western turkey evidences of strike slip faulting with compression in the aegean extensional regime abstract of single channel 70 km and 900 km of multi channel seismic reflection data show that izmir gulf and surrounding regions are widely deformed by n s to ne sw trending active transpressional strike slip faults reverse faults and some e w normal faults normal faults are mapped offshore karaburun foca in inner part of izmir gulf offshore alacati teke and offshore kusadasi delimiting the southern scarp of lesvos basin izmir basin northern scarp of ikaria basin and continuation of kucuk menderes graben respectively normal faults are cut by strike slip faults the major strike slip faults are the n s oriented karaburun reverse fault bordering izmir gulf on the west and uplifting the karaburun peninsula and the ne sw oriented strike slip tuzla fault extending from doganbey promontory towards seferihisar ridge onland this fault pattern can be explained by pure shear model indicating that the area is under e w compression n s extension ne sw and nw se strike slip deformation moreover tuzla fault has a regional importance it separates ne sw trending structures of the study area from e w oriented gediz and kucuk menderes grabens and probably continues towards to iznik at north constituting a transition zone between northern transpressional region and southern extensional region in the western anatolia aegean sea

late cenozoic volcanic evolution of the northeastern aegean region abstract late cenozoic volcanism occurred in an extensional tectonic regime in the northeastern aegean activity commenced in northeastern greece during the early oligocene and in northwestern turkey during the late oligocene early miocene the beginning of activity was characterized by calc alkaline intermediate acid volcanism however alkaline intermediate basic volcanism became dominant from the late miocene until the pleistocene this change in nature of volcanism is not related to a change of regional tectonic regime as previously thought instead we propose that the volcanic evolution reflects an increasing asthenospheric contribution facilitated by a thinned extended lithosphere arising from the regional extensional tectonics

correlation of loess paleosol sequences in east and central asia with se central europe towards a continental quaternary pedostratigraphy and paleoclimatic history abstract as recent small climatic fluctuations on a 102 103 year time scale can be correlated worldwide and represent a decline of mean annual temperature of only 1 c major climatic changes on at least a 105 year scale glacial interglacial cycles and probably a 104 year scale the approximate length of an interglacial must be of similar ages throughout the temperate climatic belt of the northern hemisphere this concept allows continental pedostratigraphical correlations detailed knowledge of the genesis of paleosols is needed to establish loess paleosol stratigraphies that can be used for paleoclimatic reconstruction most paleosols however are truncated and largely recalcified from overlying loess micromorphological studies allow primary and secondary carbonates to be distinguished and provide unequivocal evidence of clay illuviation this enables the recognition of typical loess weathered loess and the recognition of different genetic soil horizons such as cb bc ah bw and bt horizons for the brunhes epoch the sequence at karamaydan tadjikistan is more detailed than the corresponding section in luochuan china and even more than in se central europe except for the last glaciation the very good correlation with the deep sea oxygen isotope record which includes the development of an accurate astronomical time scale allows a detailed chronostratigraphical subdivision of the loess paleosol sequence in karamaydan which therefore should be regarded as a key sequence for reconstructing the climatic history of the brunhes epoch this implies that the loess paleosol sequences in se central europe are less complete than thought earlier pedocomplexes in karamaydan correspond with single paleosols in se central europe e g the f6 paleosol in stari slankamen correlates with pedocomplexes pk vi and v at karamaydan which were formed over a period of about 140 ka although pedogenesis was interrupted several times by loess deposition the f6 soil is therefore an example of a welded paleosol as are the f5 the f4 and the f2 paleosols in se central europe for most of the matuyama epoch the central and lower parts of the sequence at chashmanigar show more pronounced paleosols than the equivalent parts at luochuan in se central europe only at stari slankamen are three strongly developed though truncated paleosols f9 f11 above neogene sediments mineralogical investigations of the silt and clay subfractions show that there is little difference in the type and amount of pedogenic clay mineral formation between the holocene soils and the paleosols of the brunhes epoch at karamaydan and of the matuyama epoch at chashmanigar this suggests that the interglacial climates represented by the b or bt horizons of the buried paleosols of late middle and early pleistocene age were similar to that of the holocene

chinese loess record of monsoon climate during the last glacial interglacial cycle the thick loess paleosol succession of central china contains a detailed record of changes in east asian monsoon climate since the late miocene epoch the alternating loess paleosol stratigraphy closely resembles the marine oxygen isotope record implying that episodic dust deposition and pedogenesis are in phase with global ice volume fluctuations and controlled by variations in solar radiation reaching the land surface deposits equivalent to marine isotope stages mis 5 through 1 have been dated by 14c 10be luminescence and magnetic susceptibility and grain size models malan loess mis 4 2 decreases in thickness southeastward from 30 m in the western loess plateau to 5 m east of xi an downwind asian dust is found in japan the north pacific ocean and the greenland ice sheet where it has a chemical signature that points to a primary source in western china during glacial times the mean dust flux in the central loess plateau reached 0 35 mm year whereas in interglacial times it fell to 0 1 mm year times of high dust influx and reduced soil development coincided with strengthened winter monsoon conditions which are inferred from variations in loess grain size times of decreased dust accumulation and strong pedogenesis marked by high values of magnetic susceptibility represent times of strengthened summer monsoon conditions high frequency fluctuations in dust influx during deposition of the malan loess include peaks that likely correlate with north atlantic heinrich events the younger dryas oscillation is recorded in chinese eolian and organic deposits by a shift from cool humid late glacial conditions to cold and dry conditions followed by a return to milder humid climate at the beginning of the holocene warm moist climate associated with a strong summer monsoon characterized the first half of the holocene epoch when a widespread paleosol complex developed on the loess plateau increased dust deposition during the middle to late holocene marked a shift to cooler drier conditions

changes in frequency size relationship from small to large earthquakes the constant b value observed in frequency magnitude distributions of earthquakes has been taken as an indication of self similarity at all magnitudes hence earthquake properties should scale uniformly in the same way from small to large earthquakes it has often been observed however that the seismic moment released in small earthquakes scales differently with rupture length than it does for large events1 2 where the crossover between small and large events is defined at a rupture dimension equal to the down dip width of the seismogenic zone a possible explanation for this contradiction is that frequency size distributions are biased by small earthquakes small events dominate most global earthquake catalogues because of the short time period covered another source of bias in size distributions is the saturation of earthquake magnitudes for large events here we correct biases in calculations of b values and present evidence for a change in b value in frequency size distributions we find that a break in self similarity from small to large earthquakes occurs at a point where the dimension of the event equals the down dip width of the seismogenic layer

holocene moisture evolution in arid central asia and its out of phase relationship with asian monsoon history we synthesize palaeoclimate records from the mid latitude arid asian region dominated today by the westerlies arid central asia aca to evaluate spatial and temporal patterns of moisture changes during the holocene sediment records from i i takes with reliable chronologies and robust proxies were selected to reconstruct moisture histories based on a five class ordinal wetness index with assigned scores from the driest to wettest periods at individual sites for 200 year time slices the proxies used in these records include pollen and diatom assemblages sediment lithology lake levels and geochemistry mainly isotope data the results of our synthesis show that aca as a whole experienced synchronous and coherent moisture changes during the holocene namely a dry early holocene a wetter less dry early to mid holocene and a moderately wet late holocene during the early holocene most of the lakes experienced very low water levels and even dried out before ca 8 ka 1 ka 1000cal a bp hence the effective moisture history in aca is out of phase with that in monsoonal asia as documented by numerous palaeoclimate records in monsoonal asia a strong summer monsoon and humid climate characterized the early holocene and a weakened summer monsoon and drier climate prevailed during the late holocene which were mainly controlled by changes in low latitude summer insolation in contrast we propose that the pattern of holocene effective moisture evolution in the westerly dominated aca was mainly determined by north atlantic sea surface temperatures ssts and high latitude air temperatures that affect the availability amount and transport of water vapor also topography of the tibetan plateau and adjacent asian highlands could have contributed to the intensification of dry climate in aca during the early holocene as a result of strengthening the subsidence of dry air masses associated with stronger uplift motion on the plateau by intense heating under a stronger summer insolation summer insolation might have played a key role in directly controlling moisture conditions in aca but only after the northern hemisphere ice sheets had disappeared in the mid and late holocene c 2007 elsevier ltd all rights reserved

correlating variations of b values and crustal deformations during the 1990s may have pinpointed the rupture initiation of the mw 7 4 izmit earthquake of 1999 august 17 summary the b value increases from 1 1 along straight segments to 1 7 along a releasing bend of the north anatolian fault system between 30 1 e and 30 8 e the tensional nature of the bend is corroborated by extension rates of 0 3 strain yr 1 as obtained from global positioning system gps data fault plane solutions in this area change from abundant right lateral strike slip to oblique slip with normal components in the central part of the bend compatible with the formation of a pull apart basin we suggest that this crustal volume is highly fractured corresponding to a short mean crack length due to the superposition of horizontal and normal faulting as a consequence of low normal stress on the existing cracks frictional sliding is assumed to be the predominant mechanism for the generation of seismic events resulting in high b values the lowest b values b 0 8 in the area investigated are found at the junction between the fault bend and the adjoining segment which runs through the epicentre of the 1999 izmit earthquake at the junction a localized stress concentration is expected from numerical models of seismicity along geometrical barriers thus the site of lowest b has been considered to be the most likely place for a major earthquake a conclusion that is confirmed by the izmit earthquake with epicentre located about 13 km from the anticipated site in early 1992 the spatially averaged b value started to increase along the central and northwestern parts of the fault bend and there was a corresponding period of intensified horizontal extension since no large earthquake was recorded in 1992 it is assumed that the anomalous extension and the associated change in stress have been caused by aseismic fault creep in view of the available seismotectonic information surface displacements due to a slow dislocation at depth were calculated the gps data are reasonably explained by a source of normal fault type at a depth of 10 km and equivalent magnitude mw 5 9 stress changes at seismogenic depths are calculated under the assumption that an increase in b is most likely to be observed along those segments where both deviatoric and mean stress are reduced while the coulomb stress change is positive that is the fault is brought closer to failure for right lateral strike slip the stress condition is fulfilled at the sites of the largest b value increase the surface rupture of the izmit earthquake is associated with known fault traces only in the west and in the east of the study area along the fault bend it detaches itself from mapped fault traces and runs through the regions of positive coulomb stress change caused by the inferred 1992 slow event maximum surface slip 5 m is observed in the immediate vicinity of sites of maximum coulomb stress change 3 bar indicating that the 1992 event could have partially unclamped the rupture plane of the subsequent izmit earthquake we propose that the strong differences in b observed along the complex fault bend can be used to characterize different states of tectonic deformation in space and time

neotectonic structures in the area offshore of alacati doganbey and kusadasi western turkey evidence of strike slip faulting in the aegean extensional province abstract about 400 km of new seismic reflection data has been acquired in the study region offshore of alacati doganbey and kusadasi which enables investigation of the active crustal deformation in this region the deformation onshore in western turkey is dominated by crustal extension and clear evidence of this process is also now available from this offshore area however in the onshore area adjacent to this study region evidence of active right lateral strike slip faulting has also previously been observed this strike slip faulting has previously been thought only to accommodate variations in extension between adjacent normal faults however in the offshore area there is considerable evidence of zones of deformation some of which may link to the strike slip faulting onshore suggesting that strike slip faulting may be of greater importance in this region than previously thought

mapping the frequency magnitude distribution in asperities an improved technique to calculate recurrence times we hypothesize that highly stressed asperities may be defined by mapping anomalously low b values along the san andreas fault near parkfield the asperity under middle mountain with its b 0 46 can be distinguished from all other parts of the fault surface likewise along the calaveras fault the northern asperity of the morgan hill 1984 m6 2 rupture can be identified by its low b of 0 5 as a high stress patch along the fault we add further evidence to the observations that the b value of the frequency magnitude relationship of earthquakes is inversely proportional to stress by showing that it decreases with depth in the parkfield segment of the san andreas and along the calaveras fault in both of these areas b values above and below 5 km depth are 1 2 and 0 8 respectively we propose that probabilistic recurrence times tr based on the seismicity parameters a and b should be calculated from their values within asperities only instead of from the values of the entire rupture area of the maximum expected earthquake the strong patches on faults control the time of rupture because they are capable of accumulating larger stresses than the rest of the fault zone which slips along passively when an asperity breaks therefore no information on tr is contained in the passive fault segments only in the asperities at parkfield the probabilistic estimates of tr derived from the data in the whole rupture and in the asperity only are 72 18 24 and 23 12 18 years respectively compared to the historically observed repeat time of 22 years at morgan hill the tr estimates are 122 46 76 and 78 47 110 years respectively compared to the observed repeat time of 72 years

causes of early holocene desertification in arid central asia paleoclimate records of effective moisture precipitation minus evaporation or p e show a dry low effective moisture period in mid latitude arid semi arid central asia during the early holocene 11 000 8 000 years ago relative to the middle and late holocene in contrast to evidence for greater than present precipitation at the same time in the south and east asian monsoonal areas to investigate the spatial differences in climate response over mid latitude central asia and monsoonal asia we conducted a series of simulations with the community climate system model version 3 coupled climate model for the early middle and late holocene the simulations test the climatic impact of all important forcings for the early holocene including changes in orbital parameters the presence of the remnant laurentide ice sheet and deglacial freshening of the north atlantic model results clearly show the early holocene patterns indicated by proxy records including both the decreased effective moisture in arid central asia which occurs in the model primarily during the winter months and the increase in summer monsoon precipitation in south and east asia the model results suggest that dry conditions in the early holocene in central asia are closely related to decreased water vapor advection due to reduced westerly wind speed and less evaporation upstream from the mediterranean black and caspian seas in boreal winter as an extra forcing to the early holocene climate system the laurentide ice sheet and meltwater fluxes have a substantial cooling effect over high latitudes especially just over and downstream of the ice sheets but contribute only to a small degree to the early holocene aridity in central asia instead most of the effective moisture signal can be explained by orbital forcing decreasing the early holocene latitudinal temperature gradient and wintertime surface temperature we find little evidence for regional subsidence related to a stronger summer asian monsoon in forcing early holocene aridity in central asia as has been previously hypothesized

luminescence dating of the pasado core 5022 1d from laguna potrok aike argentina using irsl signals from feldspar in this paper we develop and test a luminescence chronology for the pasado core 5022 1d taken in the laguna potrok aike maar lake because of unsuitable quartz osl characteristics sand sized k feldspar extracts were chosen as a dosimeter and the dose was measured using a recently developed post ir irsl pirir290 measurement protocol using this approach we were able to access a stable signal and thus avoid the ubiquitous problem of signal instability in feldspar dating extensive laboratory tests show that the chosen pirir290 protocol is applicable to these samples we also develop a new criterion based on the known relative bleaching rates of the conventional irsl signal ir50 and the pirir290 signals and the relationship between the resulting equivalent doses this is used to identify and reject poorly bleached samples fourteen samples out of 35 were rejected based on this criterion the resulting age depth profile is self consistent increases smoothly with depth and is in agreement with the independent age control reclus mt burney and hudson tephras at the top of the core our new luminescence chronology suggests the 5022 1d core reaches back to 65 ka at 96 m below lake floor

multistage exhumation of the menderes massif western anatolia turkey structural analyses along selected transects across the menderes massif and incorporation of existing data have resulted in a synthetic cross section across southwestern turkey the tectonic interpretation has been combined with 40ar 39ar laser probe experiments on two syn kinematic white mica populations which respectively predate and overprint documented early miocene deformational fabrics our results indicate that the regional extension had initiated by eocene oligocene times a 36 2 ma 40ar 39ar age derived from white mica which formed during a regionally observed northward directed tectonic transport suggests that the extension was contemporaneous with the tectonic emplacement of mid crustal continental basement alternatively the age may relate to the regional cooling of the basement sequence and thus postdates the tectonic emplacement in the latter scenario the analysis fails to solve the present ambiguity on the pan african or alpine affinity of the northward directed transport further exhumation of basement rocks is characterized by a dominant displacement along the north dipping gediz detachment at the northern margin of the massif which developed under ductile conditions in the early miocene by partial exploitation of older zones of weakness which originated from an earlier phase of basement emplacement youngest semi ductile activity along the gediz detachment has been recorded as having a 7 1 ma 40ar 39ar age derived from syn kinematic white mica in the top of the detachment following the initiation of the ductile gediz detachment an antithetic semibrittle and south dipping buyuk menderes detachment had developed in the center of the massif which together with the gediz detachment accommodated further doming of the central part of the menderes massif and controlled the architecture of the surrounding supradetachment basins

geodetic determination of the kinematics of central greece with respect to europe implications for eastern mediterranean tectonics we use a new satellite laser ranging global positioning system slr gps solution at seven sites in anatolia and aegea to obtain a better definition of the extrusion motion of the anatolian aegean block with respect to europe we show that this motion can be described in a first approximation by a counterclockwise rotation which transfers most of the motion of arabia to anatolia we combine 78 displacement vectors obtained at common points of two triangulation nets measured in central greece in 1895 and 1975 with the slr gps measurements to compute the velocity field over greece with respect to europe these measurements indicate that central greece is a zone of extension between the anatolian aegean counterclockwise rotation to the south and the northern greece clockwise rotation to the north this extension is principally localized within the gulf of corinth to the east but is distributed to the west we then extrapolate this velocity field to the whole aegea and western anatolia using recently published gps results as well as the slr results the narrow dextral north anatolian fault which limits the velocity field to the north progressively gives way to a much wider boundary zone where extension becomes dominant we show that the collision between the mediterranean ridge and africa began 3 6 ma and we describe the modifications that this collision has produced on the kinematic pattern both in aegea and on the mediterranean ridge

east asian monsoon variations during oxygen isotope stage 5 evidence from the northwestern margin of the chinese loess plateau abstract we present the results of high resolution multi proxy climate studies of the s1 palaeosol corresponding to oxygen isotope stage ois 5 from the northwestern margin of the chinese loess plateau area here s1 is much thicker ca 6 8 m than in the central loess plateau areas ca 2 m where most previous studies have been conducted hence much higher resolution stratigraphic studies are possible yielding more insight into the temporal variations of the east asian monsoon during mis 5 the frequency dependent magnetic susceptibility as well as the concentration of secondary carbonate is used as an indicator of the summer monsoon intensity and the median particle size as an indicator of the winter monsoon intensity the results suggest that the northwestern margin of the chinese loess plateau experienced the strongest summer monsoon intensity in sub stage oiss 5e and the weakest in oiss 5a among the three warmer periods during stage 5 the summer monsoon was weaker in oiss 5b than in oiss 5d a dusty interval interrupted the second warmer period 5c and a soil forming event interrupted the first colder period 5d the results also suggest that the directions of changes in the intensities of summer and winter monsoons may not always have been proportionately opposite for example the weakest summer monsoon occurred in oiss 5a during which the winter monsoon was not the strongest we further conclude that the winter monsoon during the last interglacial was probably driven by global ice volume fluctuations while the summer monsoon was primarily controlled by the northern hemisphere solar insolation and was probably modified by a feedback mechanism that is the climatic buffering effect of low latitudinal oceans may have distorted the response of the summer monsoon to insolation variations finally our results do not show the degree of climatic instability comparable to that recorded in the grip ice core for the last interglacial oiss 5e even though the study area is situated in a region which has been sensitive to climatic changes

mapping asperities by minima of local recurrence time san jacinto elsinore fault zones minima of the local recurrence time tl m are correlated with the locations of historical main shocks in the san jacinto sj elsinore e fault zones of southern california we define tl m as the recurrence time calculated from the local b and a values of the frequency magnitude distribution earthquakes within 6 and 10 km from each point in the sj and e fault zones respectively we propose that anomalously low tl m values map asperities out of six historic main shocks 1899 1968 five ruptured substantial parts of four asperities mapped by our method which uses solely the modern earthquake catalog m 1 2 1981 0 1998 8 we estimate the probability for this correlation to occur at random as 10 2 to 10 3 depending on the scenario chosen it appears that the minima in tl m are tied to minima in b values more than to maxima in a values thus locations of low b values can also be used as an indication where asperities may be located and where main shocks are most likely the anza gap a segment of the san jacinto fault with low a values is mapped as an asperity by our method the heterogeneity in b values is strong throughout the study area the b values range from 0 5 to 1 8 over distances of 10 km volumes with approximately constant b values have radii of r 8 6 km our results suggest that detailed mapping of b values and local recurrence times in volumes with a few kilometers radius reveals important information about the local seismic hazard hitherto untapped by conventional seismicity analyses

high resolution record of climate stability in france during the last interglacial period the last interglacial period 127 110 kyr ago has been considered to be an analogue to the present interglacial period the holocene which may help us to understand present climate evolution but whereas holocene climate has been essentially stable in europe variability in climate during the last interglacial period has remained unresolved because climate reconstructions from ice cores1 2 continental records3 4 and marine sediment cores5 6 give conflicting results for this period7 here we present a high resolution multi proxy lacustrine record of climate change during the last interglacial period based on oxygen isotopes in diatom silica diatom assemblages and pollen climate transfer functions from the ribains maar in france contrary to a previous study8 our data do not show a cold event interrupting the warm interglacial climate instead we find an early temperature maximum with a transition to a colder climate about halfway through the sequence the end of the interglacial period is clearly marked by an abrupt change in all proxy records our study confirms that in southwestern europe the last interglacial period was a time of climatic stability and is therefore still likely to represent a useful analogue for the present climate

the holocene salinity history of bosten lake xinjiang china inferred from ostracod species assemblages and shell chemistry possible palaeoclimatic implications abstract a sediment core from bosten lake the largest freshwater lake in the tianshan mountains and in the northwesternmost province of china provided a high resolution record of environmental change covering the last 8500 cal a bp higher salinity levels of bosten lake were reconstructed from assemblages the stable isotope composition and sr ca and mg ca ratios of ostracod shells between 7800 and 5600 cal a bp a period of low and moderate salinities between 5600 and 4900 cal a bp was followed by the re establishment of higher salinities between 4900 and 4300 cal a bp since then bosten lake has recorded fluctuating conditions with a number of multi centennial phases of low and moderate salinities although the salinity lake level relationship of bosten lake is not fully understood a higher salinity at the core site seems to correspond to periods of higher lake levels this contradictory interpretation is explained tentatively by the changing distance of the core site to the freshwater providing river mouth with changing lake levels and potentially resulting lateral shifts of the salinity distribution pattern within the lake assuming this explanation is correct the record from bosten lake reflects higher moisture availability and a strong climatic influence of the indian monsoon in the early mid holocene until about 4000 cal a bp and more unstable drier conditions susceptible to minor changes in the regional circulation patterns and temperature variations afterwards

moisture dynamics in central asia for the last 15 kyr new evidence from yili valley xinjiang nw china based on high resolution palynological investigations and ams 14 c dating the continuous lacustrine sediments contained in yili valley xinjiang provide an opportunity to reconstruct the effective moisture changes for the last 15 kyr in central asia the relatively warm and humid climate of the bolling allerod 15 12 9 cal kyr bp is a generalization but it seems to show some fluctuations the time of the younger dryas yd interrupted the increasing trend of effective moisture in the study region the climate was cold and relatively dry in the early yd period 12 9 12 0 cal kyr bp whereas the desert vegetation community appeared around 11 8 cal kyr bp almost the driest time since the 15 cal kyr br a sharp increase in effective moisture marked the beginning of the holocene in the yili valley the early holocene 10 6 7 6 cal kyr bp was the wettest time with a developed temperate steppe a dry climate with desert vegetation arose in the early mid holocene 7 6 6 5 cal kyr bp spanning 1100 years a second humid phase emerged between 6 5 and 5 2 cal kyr bp whose vegetation community was represented by temperate steppe moisture was reduced again and the climate became drier between 5 2 and 3 3 cal kyr bp when vegetation was dominated by desert steppe in the yili valley regional comparisons indicate that the moisture changes in yili valley were mainly influenced by the north atlantic ocean ssts through the westerlies the mean position of the siberian high pressure cell probably made a great contribution to the drought between 7 6 and 6 5 cal kyr bp the climate changes were generally consistent between the westerly dominant central asia and asian monsoon regions since the last deglaciation possibly forced by summer insolation conditions in the northern hemisphere c 2011 elsevier ltd all rights reserved

stability and significance tests for b value anomalies example from the tyrrhenian sea 1 we spatially map b values in the southern tyrrhenian subduction zone italy a high b value anomaly 90 200 km beneath the aeolian island volcanoes is interpreted as being related to the origin of magma for the aeolian volcanic district this result is independent of the sample size width of the cross section or its orientation to assess the stability of these findings we develop a new more realistic uncertainty assessment based on a bootstrap method our approach explicitly takes into account the uncertainty in the assessment of the completeness in magnitude reporting to quantify the significance of the results when compared to a chance occurrence we compute monte carlo style simulations based on catalogs with permuted magnitudes our entire tests show that the high b value anomaly is stable and highly significant

orbital and millennial antarctic climate variability over the past 800 000 years a high resolution deuterium profile is now available along the entire european project for ice coring in antarctica dome c ice core extending this climate record back to marine isotope stage 20 2 800 000 years ago experiments performed with an atmospheric general circulation model including water isotopes support its temperature interpretation we assessed the general correspondence between dansgaard oeschger events and their smoothed antarctic counterparts for this dome c record which reveals the presence of such features with similar amplitudes during previous glacial periods we suggest that the interplay between obliquity and precession accounts for the variable intensity of interglacial periods in ice core records

decade scale decrease inb value prior to the m9 class 2011 tohoku and 2004 sumatra quakes 1 the gutenberg richter frequency magnitude distribution of earthquakes has become well established in seismology the slope of the relation between frequency and magnitude b value is typically 1 but it often shows variations around 1 based on an analysis of seismicity prior to the 2011 tohoku and 2004 sumatra earthquakes both in magnitude m 9 class we show that the pronounced decade scale decrease inbvalue was a common precursor to both mega quakes around their hypocenters this is the first report onm9 class quakes to confirm a change inb value which has been predicted based on the results of laboratory experiments we propose that the b value is an important indicator of an impending great earthquake and has great potential in terms of predicting a future large quake off the pacific coast of hokkaido japan

present day kinematics of the middle east and eastern mediterranean the middle east and eastern mediterranean regions contain three major strike slip fault zones the dead sea fault zone dsfz and the north and east anatolian fault zones nafz and eafz these accommodate northward motion of the african and arabian plates relative to eurasia and westward motion of the small turkish plate this study deduces an internally consistent solution for the present day kinematics of these plates which is accurate to better than 20 and applicable throughout time since 5 ma by constraining the slip senses and rates on these strike slip fault zones the 7 0 5 mm yr 1 left lateral slip rate on the dsfz is associated with counterclockwise rotation of arabia relative to africa at 0 33 m y 1 around an eulcr pole near 33 n 23 e the nafz takes up counterclockwise rotation of the turkish plate relative to eurasia at 0 83 m y 1 13 around a pole at 31 n 35 5 e with right lateral slip rate 15 mm yr 1 the resulting prediction for the eafz involves 14 mm yr 1 left lateral motion and 2 mm yr 1 of shortening between arabia and turkey the triple junction of africa arabia and turkey is near the city of kahramanmaras this locality contains a narrow promontory bounded by ssw trending left lateral faults at the edges of the arabian and turkish plates which is loosely attached to the african plate moving westward relative to its interior at 4 mm yr 1

a persistent holocene wetting trend in arid central asia with wettest conditions in the late holocene revealed by multi proxy analyses of loess paleosol sequences in xinjiang china abstract there are significant differences in the interpretation of the moisture precipitation history of arid central asia aca during the holocene as inferred on one hand from speleothem oxygen isotope records and on the other from lake sediments here we present the results of measurements of climatically sensitive magnetic properties and soil color from four well dated loess paleosol sequences from the northern slopes of the tienshan mountains and the yili river valley xinjiang china in the core area of aca our results demonstrate that the characteristic holocene paleosol indicating relatively moist conditions generally formed after 6 ka 1 ka 1000 cal yr bp in the study region and that the accumulation of unweathered loess prevailed during the early holocene indicating a dry climate at that time the magnetic proxies further reveal a trend of generally increasing moisture since the last glacial maximum with the wettest climate occurring during the late holocene this trend of increasing moisture during the holocene is representative of the xinjiang region and possibly of the whole of the core area of aca and is in marked contrast both to the mid holocene moisture maximum observed in the east asian summer monsoon region and to the general decrease in the strength of the indian summer monsoon since the early holocene our findings are supported by the results of a climate simulation which indicate a trend of increasing summer and winter precipitation during the holocene in the core area of aca caused mainly by an increase in the strength of the westerlies effected by an increasing latitudinal insolation gradient and by a negative trend of the arctic oscillation ao or north atlantic oscillation nao

variation and paleoclimatic significance of organic carbon isotopes of ili loess in arid central asia as an indicator for terrestrial paleovegetation the stable isotopic composition of total organic matter delta c 13 org in loess sediments has been widely used for paleoclimatic reconstruction in western europe the great plains of north america and the chinese loess plateau clp however little is known about the variation and paleoclimatic significance of the loess delta c 13 org in arid central asia aca we report delta c 13 org data from an axike axk loess paleosol profile from the eastern ili basin eastern central asia along the profile the delta c 13 org values were more negative in the paleosol layers observed in the field and were confirmed by environmental magnetic proxies and a higher concentration of total organic carbon toc consistent with results for western europe and the northwestern clp our results demonstrate that the loess delta c 13 org in this region documents mainly the response of delta c 13 of locally predominant c 3 plants to paleoclimatic variation especially paleoprecipitation our results also suggest that the loess delta c 13 org values in the area have the potential for quantitative paleoprecipitation reconstruction on the basis of detailed delta c 13 org results from modern plants and surface soils in the future c 2013 elsevier ltd all rights reserved

estimating earthquake hazard parameters from instrumental data for different regions in and around turkey abstract we conducted a study of the spatial distributions of seismicity and earthquake hazard parameters for turkey and the adjacent areas applying the maximum likelihood method the procedure allows for the use of either historical or instrumental data or even a combination of the two by using this method we can estimate the earthquake hazard parameters which include the maximum regional magnitude m max the activity rate of seismic events and the well known b value which is the slope of the frequency magnitude gutenberg richter relationship these three parameters are determined simultaneously using an iterative scheme the uncertainty in the determination of the magnitudes was also taken into consideration the return periods rp of earthquakes with a magnitude m m are also evaluated the whole examined area is divided into 24 seismic regions based on their seismotectonic regime the homogeneity of the magnitudes is an essential factor in such studies in order to achieve homogeneity of the magnitudes formulas that convert any magnitude to an m s surface scale are developed new completeness cutoffs and their corresponding time intervals are also assessed for each of the 24 seismic regions each of the obtained parameters is distributed into its respective seismic region allowing for an analysis of the localized seismicity parameters and a representation of their regional variation on a map the earthquake hazard level is also calculated as a function of the form m max rp 6 0 and a relative hazard scale defined as the index k is defined for each seismic region the investigated regions are then classified into five groups using these parameters this classification is useful for theoretical and practical reasons and provides a picture of quantitative seismicity an attempt is then made to relate these values to the local tectonics

luminescence dating of the stratzing loess profile austria testing the potential of an elevated temperature post ir irsl protocol abstract feldspar infrared stimulated luminescence irsl signals saturate at 2000 gy i e 500 700 ka assuming a dose rate of 3 4 gy ka typical for loess and it is therefore theoretically possible to date middle pleistocene loess however the accuracy of age estimates is hampered by anomalous fading which leads to significant age underestimation fading corrections have been proposed but these corrections are reliant on inherent assumptions and in any case are inapplicable at large doses as the growth curve approaches saturation recent studies have identified a post ir irsl signal that shows less fading and is thus less dependent on accurate fading corrections this study builds upon these investigations and applies a post ir irsl sar dating protocol to polymineral fine grain samples of the loess palaeosol sequence in stratzing lower austria after a preheat at 320 c 60 s and an ir bleach at 50 c 200 s irsl was measured at 290 c for 200 s the same set of conditions were used to measure the response to a test dose recycling ratios recuperation and dose recovery tests show that this protocol is suitable for the loess under investigation although finite residual doses of up to 20 gy are observed for the oldest samples the natural signal is in or close to saturation indicating that fading is negligible in nature this observation is inconsistent with the measured laboratory fading rates of 1 1 5 decade and needs further investigation

the loess record in southern tajikistan and correlation with chinese loess in the present study the chashmanigar loess soil sequence in southern tajikistan is studied this loess section has a paleomagnetic basal age of about 1 77 myr magnetic susceptibility color reflectance and grain size were systematically measured for closely spaced samples from the section paleosols consistently have a finer grain size distribution higher magnetic susceptibility redder color reflectance and lower dust sedimentation rate than loess horizons suggesting a colder drier and dustier environment during glacial periods than in interglacial periods the grain size record was tuned to variations in obliquity and precession of the earth s orbit the resulting magnetic susceptibility grain size and color reflectance time series all show well expressed astronomical periodicities during the pleistocene the mid pleistocene climate transition characterized by a shift of dominant climatic periods from 41 kyr to 100 kyr at about 1 0 0 8 myr is clearly documented in these proxy records comparison of the chashmanigar loess record with the lingtai loess section in china and the odp site 677 n 18 o record shows that during the entire pleistocene the climate cycles recorded by the central asian loess can be well correlated to the chinese loess and deep sea oxygen isotope records it is suggested that alternations of loess and soil horizons both in central asia and china could be basically forced by global ice volume variations although different wind systems have controlled the pleistocene loess transport and sedimentation in the two areas 2002 elsevier science b v all rights reserved

the history and variability of the east asian paleomonsoon climate abstract changes in the east asian paleomonsoon reflect interactions between the global atmosphere ocean land and ice systems and are also an expression of their combined effect within the boundary conditions imposed by the east asian continent and solar radiation the history of the east asian monsoon is an alternation between dominance by the dry cold winter and warm humid summer monsoons high resolution eolian sequences preserved in the chinese loess plateau reveal that the east asian monsoon may have commenced at least 7 2 ma ago they also provide evidence indicating that the pulsed uplift of the tibetan plateau at about 3 4 and 7 2 ma may have played an important role in inducing climate change the palaeoclimatic records of the last glacial cycle show high frequency variability on time scales of 1000 year or even shorter and instability of the east asian paleomonsoon system the high frequency variability could be due to a non linear response to orbital forcing or a result of the coupling processes between different components of the global system cold air activity in northern high latitudes the trans equatorial air streams from the southern hemisphere and possibly enso may have played an important role in east asian monsoon variability the synchroneity of all the palaeoclimatic events along the polar equator polar pep transect is still an open question correlation of limited palaeoclimatic records for the last 30 kyr obtained from east asia and australia suggests that the trans equatorial air streams driven by the monsoon and trade winds may have had an influence on opposite hemispheres

can meddies be detected by satellite altimetry geosat exact repeat mission altimeter data have been used to estimate the sea surface height anomaly relative to a 2 year mean reference surface in the eastern north atlantic ocean horizontal maps of the sea surface height anomaly for various periods were constructed by means of an objective analysis procedure the mean sea level was approximated by the dynamic topography from climatological hydrographic data results were compared to the dynamic topography calculated from hydrographic ground truth data sampled during march 1988 on an eddy resolving station network in the iberian basin despite the low signal to noise ratio of the altimeter data in this part of the ocean the agreement of the altimeter signal with hydrographic measurements is found to be significant individual cyclonic and anticyclonic eddies in the mediterranean outflow are identified in the altimetric maps the information visible in the sea surface height is significantly correlated with the dynamic topography of the layer 500 3000 dbar containing the core of the mediterranean outflow and maximum velocities of the baroclinic eddies the successive development of the identified eddies as studied from a sequence of sea surface height maps indicates a slight westward drift of the most pronounced feature with approximately 1 9 cm s propagation velocity the inferred path of that feature is consistent with additional information from moored current meter data

spatiotemporal analyses of earthquake productivity and size distribution observations and simulations we use relocated catalogs of microearthquakes to investigate earthquake interaction along sections of the sargent calaveras and san andreas faults in cali fornia we examine the stress dependence of seismicity rate change along the three fault segments and find that the seismicity rate following a mainshock decays ap proximately as 1 time the duration of the aftershock activity seems to be independent of distance from the mainshock and the seismicity rate at lag times of up to about 100 sec is nearly constant in the san andreas and the calaveras catalogs where the return of the seismicity rate to the background level is well resolved we find that the return to the background in the distance range of 1 2 rupture radii from a previous earthquake is preceded by a period during which the seismicity rate falls about 30 below the background rate we also examine the effect of a stress step on earthquake size distribution along these faults and find that the exponent of the power law dis tribution of earthquake magnitudes within 10 4 sec of a previous earthquake is sig nificantly lower than that of the long term while the 1 time decay of seismicity rate the independence of aftershock duration from distance from the mainshock and the constant seismicity rate at short lag times are predicted by dieterich s 1994 model the decrease of seismicity rate below the background level and the changes in earth quake size distribution are not for comparison with our observations we simulate earthquake activity on an in herently discrete fault model that is governed by an approximate constitutive friction law similar to the one used by dieterich 1994 we find that the observed response of earthquake productivity and size distribution to a stress step are produced by these simulations the effect of the mainshock is not only to raise the local seismicity rate but also to systematically modify the earthquake size distribution this is because fault patches that are near failure at the time of the stress step are strengthened whereas fault patches that at the same time were far from failure are weakened as a result similar to what is observed for the calaveras and the san andreas segments late during the aftershock sequence the seismicity rate may decrease below the back ground rate we suggest that the time dependent modification of the earthquake size distribution by a stress step can explain observations of lower b values immediately following a stress step

correlating seismicity parameters and subsidence in the tokai region central japan 1 we demonstrate that transients in subsidence rate in the tokai area of central japan correlate with changes in the rate and size distribution of earthquakes three largely independent seismic catalogs cover this region national research institute for earth science and disaster prevention nied japanese meteorological agency jma and japan university network catalog junec comparing seismicity patterns between these three data sets offers a unique opportunity to verify seismicity anomalies based on independent sources a study of data quality magnitude reporting consistency and consistency across the three data sources reveals that the nied data for the period 1981 2002 are best suited for seismicity analysis we spatially and temporally map seismicity rates finding that a significant decrease in the earthquake rate of m 2 0 events coincides with an accelerated subsidence period however this anomaly disappears when including smaller magnitudes in the analysis this relative quiescence of larger events can readily be explained when interpreting the transient in seismicity in the framework of a change in the earthquake size distribution or b value the background b value of about 0 8 increased in the period 1987 5 1989 5 to a value of b 1 2 a highly significant change that can be confirmed in all three data sets the correlation between subsidence and b value change is significant stress tensor inversions of focal mechanism data for the anomalous period show an increase in thrusting type earthquakes while a unique interpretation of the relationship between subsidence and b value is not possible we propose that an increase in the locking stress a slow stick event is consistent with all observations

earthquake statistics at parkfield 1 stationarity of b values 1 in this paper paper 1 we quantitatively show that the heterogeneous pattern of b values of the gutenberg richter relation in the parkfield segment of the san andreas fault is to a high degree stationary for the past 35 years this prepares the grounds for paper 2 where we test the hypothesis that our model of spatially varying b values forecasts future seismicity more accurately than the approach in which one assumes a constant b value equal to the average regional value the method we develop to measure stationarity in the presence of spatial heterogeneity consists of the following steps 1 determine the optimal dimensions of the sampling volume by mapping b values with a wide range of radii and selecting the largest radius that gives the most detailed resolution of the b value heterogeneity along the selected fault segment the high data density permits the definition of the dominant dimensions of the seismotectonic fabric which is about 8 10 km 2 map the difference in b value between two periods selecting numerous possible catalog divisions 3 identify significant changes of b values by the utsu test utsu 1992 along the studied fault segment of 110 km length only one patch of radius 5 km showed a significant increase in b from below average to above as a function of time this change in b initiates around 1993 and thus correlates in space and time with a well documented episode of creep at depth using the derived spatial variable b value distributions we find that the highest probability for earthquakes with magnitude m 6 is in the middle mountain asperity where the 1966 parkfield earthquake nucleated and where all m 4 5 events in the data set occurred in contrast if only the regional average b value of 0 92 is used to predict future seismicity the creeping segment north of parkfield should produce major earthquakes most frequently a conclusion that contradicts the observations

monsoon climate of the early holocene climate experiment with the earth s orbital parameters for 9000 years ago values for the precession and obliquity of the earth 9000 years ago indicate that the global average solar radiation for july 9000 years ago was 7 percent greater than at present when the estimated solar radiation values are used in a low resulation climate model the model simulates an intensified continent scale monsoon circulation this result agrees with paleoclimatic evidence from africa arabia and india that monsoon rains were stronger between 10 000 and 5000 years ago than they are today

the accommodation of large strains in the upper lithosphere of the earth and other solids by self similar fault systems the geometrical origin of b value plate tectonics has provided a method of visualizing the geometry of the deformation of the earth s lithosphere on a large scale the description is so concise that for many purposes it provides an explanation of geological processes that overshadows the need to understand the driving processes the mechanics of the zones between the plates are less well understood particularly in continental regions where large areas are subject to deformation both continuous and discontinuous models have been tried but both have obvious drawbacks

holocene moisture evolution across the mongolian plateau and its surrounding areas a synthesis of climatic records abstract based on the review of 26 high standard holocene climatic reconstructions mainly pollen based from the mongolian plateau and its surrounding areas temporal and spatial patterns of the holocene moisture evolution are synthesized the regionally averaged moisture history from the summer monsoon influenced semiarid belt in china i e region a demonstrates that the moisture index curve is broadly in agreement with the synthesized east asian monsoon strength curve both following the general trend of the west tropical pacific sst that is in turn the delayed response to the northern hemispheric summer solar insolation the regionally averaged moisture indices from the winter monsoon dominated southern siberia including lake baikal area and the altai mountains i e region b exhibit a general declining trends since 10 6 9 6 cal kyr bp being largely consistent with the trends of the annual precipitation and the warm season temperature in the russian plain the consistency might be attributable to the holocene declining trend of the warm season temperature in north atlantic region the predominant feature of the regionally averaged moisture index from the westerlies affected northern xinjiang i e region c is a persistent increasing trend since 8 cal kyr bp the wetting trend of northern xinjiang during the past 8000 years might be attributable to the increasing trend of winter insolation and to the associated increasing trend of cold season temperature in northwestern europe the chronological correspondences between dry phases and warm intervals in the arid areas of the mongolian plateau i e northern mongolian plateau within mongolia and southern mongolian plateau within china region d lend a support to the proposal that the mid holocene dry phase was most likely the result of mid holocene high warm season temperature

brittle ductile transition and associated seismicity experimental and numerical studies and relationship with the b value the acoustic emission ae and the mechanical behavior of granite samples during triaxial compression tests have been analyzed the size of ae events displays power law distributions conforming to the gutenberg richter law observed for earthquakes which is characterized by the b value as the confining pressure increases the macroscopic behavior becomes more ductile for all different stages of the rock mechanical behavior linear nonlinear prepeak nonlinear postpeak shearing there is a systematic decrease of the b value with increasing confining pressure a numerical model based on progressive elastic damage and the finite element method allows simulations of the main experimental observations on ae and of a wide range of macroscopic behaviors from brittleness to ductility the model reproduces a decrease in the b value that appears to be related to the type of macroscopic behavior brittle ductile rather than to the confining pressure both experimental and numerical results suggest a relationship between the b value and the brittle ductile transition moreover these results are consistent with recent earthquake observations and give new insight into the behavior of the earth s crust

temporal variation of seismic b values beneath northeastern japan island arc 1 analysis of a high quality seismic catalog reveals that the average of seismic b values in the crust beneath most part of northeastern japan island arc decreased from 0 86 between 1984 and 1990 to 0 73 between 1991 and 1995 the two areas with the largest decrease are found to be in the same areas where the coupling between the north american and the pacific plates is the highest as suggested by a recent geodetic study in the same time period the annual seismic moment release increased by 10 times in addition there seems to be a corresponding increase in volcanic activities in the same area one of the most likely interpretations for the observations is an increase in the subduction rate starting from 1991 the timing of this possible increase in subduction rate is consistent with an apparent increase in global seismic activity

tectonic evolution of the gediz graben field evidence for an episodic two stage extension in western turkey western turkey is one of the most spectacular regions of widespread active continental extension in the world the most prominent structures of this region are e w trending grabens e g gediz and buyuk menderes grabens and intervening horsts exposing the menderes massif this paper documents the result of a recent field campaign field geological mapping and structural analysis along the southern margin of the modern gediz graben of pliocene 5 ma age this work provides field evidence that the presently low angle ductile brittle detachment fault is cut and displaced by the high angle graben bounding normal faults with total displacement exceeding 2 0 km the evolution of the n s extension along the gediz graben occurred during two episodes each characterized by a distinct structural styles 1 rapid exhumation of menderes massif in the footwall of low angle normal fault core complex mode during the miocene 2 late stretching of crust producing e w grabens along high angle normal faults rift mode during pliocene quaternary times separated by a short time gap the later phase is characterized by the deposition of now nearly horizontal sediments of pliocene age in the hanging walls of the high angle normal faults and present day graben floor sediments the evolution of extension is at variance with orogenic collapse and or back arc extension followed by the combined effect of tectonic escape and subduction rollback processes along the aegean cyprean subduction zone consequently it is misleading to describe the miocene sediments exhumed on shoulders of the gediz graben as simple graben fill

the b parameter in the betic cordillera rif and nearby sectors relations with the tectonics of the region abstract the a and b parameters of the gutenberg richter ratio for intensities and magnitudes are evaluated according to the methods of calculation treatment and quality of the data used when these variability factors have been controlled by the corresponding confidence indices the mean values of these parameters are used to regionalise the iberian maghreb area as regards shallow and intermediate seismicity analysis of the various sectors under consideration seismic groupings differentiated seismic sources in the betic cordillera crustal domains and lithospheric domains provides values of the afore mentioned parameters coherent with the known tectonic evolution of this area we also show that the b parameter is not reliable for small size seismic sources because of the poor statistical representativity of the sample very few years for small regions the b parameter values obtained for both crustal and lithospheric domains are remarkably similar and can be linked with what is to be expected in highly fractured sectors this supports the hypotheses that explain the existence of intermediate seismicity by movement of faults cutting almost the entire lithosphere or even by the possible presence of a zone of incipient subduction

lessons learned from oxygen isotopes in modern precipitation applied to interpretation of speleothem records of paleoclimate from eastern asia abstract variability in oxygen isotope ratios collected from speleothems in chinese caves is often interpreted as a proxy for variability of precipitation summer precipitation seasonality of precipitation and or the proportion of 18o to 16o of annual total rainfall that is related to a strengthening or weakening of the east asian monsoon and in some cases to the indian monsoon we use modern reanalysis and station data to test whether precipitation and temperature variability over china can be related to changes in climate in these distant locales we find that annual and rainy season precipitation totals in each of central china south china and east india have correlation length scales of 500 km shorter than the distance between many speleothem records that share similar long term time variations in 18o values thus the short distances of correlation do not support though by themselves cannot refute the idea that apparently synchronous variations in 18o values at widely spaced 500 km caves in china are due to variations in annual precipitation amounts we also evaluate connections between climate variables and 18o values using available instrumental measurements of 18o values in precipitation these data from stations in the global network of isotopes in precipitation gnip show that monthly 18o values generally do not correlate well with either local precipitation amount or local temperature and the degree to which monthly 18o values do correlate with them varies from station to station for the few locations that do show significant correlations between 18o values and precipitation amount we estimate the differences in precipitation amount that would be required to account for peak to peak differences in 18o values in the speleothems from hulu and dongge caves assuming that 18o scales with the monthly amount of precipitation or with seasonal differences in precipitation insofar as the present day relationship between 18o values and monthly precipitation amounts can be applied to past conditions differences of at least 50 in mean annual precipitation would be required to explain the 18o variations on orbital time scales which are implausibly large and inconsistent with published gcm results similarly plausible amplitudes of seasonal cycles in amounts or in seasonal variations in 18o values can account for less than half of the 4 5 difference between glacial and interglacial 18o values from speleothems in china if seasonal cycles in precipitation account for the amplitudes of 18o values on paleoclimate timescales they might do so by extending or contracting the durations of seasons a frequency modulation of the annual cycle but not by simply varying the amplitudes of the monthly rainfall amounts or monthly average 18o values amplitude modulation allowing that several processes can affect seasonal variability in isotopic content we explore the possibility that one or more of the following processes contribute to variations in 18o values in chinese cave speleothems different source regions of the precipitation which bring different values of 18o in vapor different pathways between the moisture source and the paleorecord site along which exchange of 18o between vapor surface water and condensate might differ a different mix of processes involving condensation and evaporation within the atmosphere or different types of precipitation each may account for part of the range of 18o values revealed by speleothems and each might contribute to seasonal differences between past and present that do not scale with monthly or even seasonal precipitation amounts

fractal dimension of fault systems in japan fractal structure in rock fracture geometry at various scales based on fault maps whether or not the fracture geometry of rocks is self similar was examined by using a box counting algorithm the statistical self similarity fractal structure of the fault fracture systems holds well at the scale of about 2 to 20 km the fractal dimension in japan varied from 1 05 to 1 60 the fractal dimension is about 1 5 1 6 at the central part of the japan arc and decreases with distance from the center at a smaller scale the fractal structure also holds well in the rock fracture geometry the fractal dimension of the north izu peninsula fault system branching faults is 1 49 at the scale of 0 625 to 10 km the fractal dimension of rock fracture geometry at the scale order of 10 1 to 10 2 meters is about 1 49 1 61 the upper limit of the fractal dimension of rock fracture geometry is about 1 6 judging from the estimation of fractal dimension on actual fracture geometry of rocks this value may impose a restraint on modeling of faulting and the fracture process of rocks

variations in earthquake size distribution across different stress regimes the earthquake size distribution follows in most instances a power law1 2 with the slope of this power law the b value commonly used to describe the relative occurrence of large and small events a high b value indicates a larger proportion of small earthquakes and vice versa statistically significant variations of b values have been measured in laboratory experiments mines and various tectonic regimes such as subducting slabs near magma chambers along fault zones and in aftershock zones3 however it has remained uncertain whether these differences are due to differing stress regimes as it was questionable that samples in small volumes such as in laboratory specimens mines and the shallow earth s crust are representative of earthquakes in general given the lack of physical understanding of these differences the observation that b values approach the constant 1 if large volumes are sampled4 was interpreted to indicate that b 1 is a universal constant for earthquakes in general5 here we show that the b value varies systematically for different styles of faulting we find that normal faulting events have the highest b values thrust events the lowest and strike slip events intermediate values given that thrust faults tend to be under higher stress than normal faults we infer that the b value acts as a stress meter that depends inversely on differential stress

nucleation points of recent mainshocks in southern iceland mapped by b values the earthquake catalog in southern iceland between 20 25 w and 21 3 w is complete down to approximately mw 0 and shows no evidence for mag nitude shifts as a function of time since 1991 this means that 6902 earthquakes m 0 1 depth 20 km are available for studies of seismicity patterns preceding the two ms 6 6 mainshocks in 2000 in their source volumes and vicinity 20 25 w and 20 9 w the power law of the frequency magnitude relationship holds down to m0 detailed mapping including 3d mapping of the b value of the frequency magnitude distribution shows that variations from b 0 6 to 1 4 exist over distances of about 2 km this suggests that the tectonic fabric in southern iceland is hetero geneous on a small scale the hypocenters of the two ms 6 6 mainshocks and one additional m 4 5 mainshock are associated with low b values 0 6 0 8 statistically significantly different from volumes in their vicinity therefore one can expect future mainshocks in southern iceland to also emanate from volumes characterized by low b values however the small dimensions of these asperities may render it difficult to identify them before the mainshocks occur low values of estimated local recur rence times 500 2000 years map the two fault zones that ruptured in 2000 against a background of local recurrence times longer than 5000 years the first of the two m 6 6 mainshocks emanated from a volume of short estimated local recurrence time this supports the hypothesis that asperities with short local recurrence times control locations of major ruptures mapping of b values in cross sections shows anomalies of high b at the bottom of the seismogenic crust correlating with the change of its thickness in the middle of the study area these high b value anomalies and other pockets of such anomalies at shallower depths are best interpreted as caused by high pore pressure because evidence of fluids under high pressure is ubiquitous in this area

spatial and temporal b value anomalies preceding the devastating off coast of nw sumatra earthquake of december 26 2004 1 spatial and temporal variations of b values are studied by means of 624 earthquakes in the andaman nicobar islands region during a five year period preceding the giant shock on december 26 2004 sliding time and space windows containing 50 events are used temporal variations reveal two significant drops in b value which coincide with the occurrence of two large shocks ms 7 0 towards the end of 2002 and with the mw 9 0 event in 2004 the spatial distribution shows accumulation of stresses low b around the epicentres of the 2002 and 2004 events and an event in north andaman the area of high stress around the 2004 epicenter extends in nnw sse direction over an area about 450 km long

a tianshan mountains loess paleosol sequence indicates anti phase climatic variations in arid central asia and in east asia abstract paleoclimatic changes in arid central asia aca one of the largest arid regions in the world are complex and the nature of these changes on orbital cycles remains unclear widely distributed loess records in aca potentially provide records of paleoclimatic variation but these records are difficult to interpret due to a lack of robust high resolution chronologies k feldspar pirir dating was employed to date 37 samples from a 13 m loess paleosol sequence section ks15 in an intermontane basin of the tianshan mountains central aca nw china the reliability of the pirir ages was determined by using internal checks of luminescence characteristics of the pir50ir290 and pir200ir290 signals and by comparing pir50ir290 and pir200ir290 ages a high resolution chronology for the loess paleosol sequence spanning 130 45 ka was established using bacon age depth modeling in combination with climate proxy indexes of magnetic susceptibility total organic material and 13 c of organic remains from the sequence our results suggest 1 the pirir ages utilizing pir50ir290 and pir200ir290 signals are consistent for loess samples

space time correlations of seismotectonic parameters examples from japan and from turkey preceding the izmit earthquake analysis of the correlation between fractal attributes of complex seis motectonic variables may offer insights into seismic hazard assessment the guten berg richter moment magnitude and moment source area relations yield a direct fractal relationship among the gutenberg richter b value occurrence rate and the characteristic linear dimension of the fault plane square root of fault surface area in contrast temporal variation in the correlation dimension of epicenters dc i s found in several studies to correlate negatively with the b value in different regions of the world spatial variations between the b value and dc also tend to oppose each other in japan negative correlations are also observed in the regional scale com parisons of the capacity dimension do of active fault systems and the b value however at local scales the relationship yields both positive and negative correla tion the occurrence of positive or negative correlation appears to be controlled by different modes of failure within the active fault complex spatial variations between the b value and dc along the northern anatolian fault zone nafz suggest that on average from 1900 to 1992 earthquake magnitudes were higher and epicenters more scattered within the central nafz than in its eastern and western segments temporal analysis reveals that the relationship between the b value and dc are nonstationary temporal correlations are generally negative a period of positive correlation is observed between 1976 and 1988 during the last 3 yr of this period 1985 1988 both the b value and d c rose significantly suggesting that stress release occurs through increased levels of low magnitude and increasingly scattered seismicity this dispersed pattern of seismicity in combination with higher slip rates in the central nafz may be one that did not adequately relieve stress along the main fault zone this change in behavior and the tendency during the last century for the seismicity to migrate westward along the nafz may point to an increased risk of larger magnitude events such as the i zmit earthquake

global positioning system constraints on plate kinematics and dynamics in the eastern mediterranean and caucasus we present and interpret global positioning system gps measurements of crustal motions for the period 1988 1997 at 189 sites extending east west from the caucasus mountains to the adriatic sea and north south from the southern edge of the eurasian plate to the northern edge of the african plate sites on the northern arabian platform move 18 2 mm yr at n25 5 w relative to eurasia less than the nuvel 1a circuit closure rate 25 1 mm yr at n21 7 w preliminary motion estimates 1994 1997 for stations located in egypt on the northeastern part of africa show northward motion at 5 6 2 mm yr also slower than nuvel ia estimates 10 1 mm yr at n2 4 e eastern turkey is characterized by distributed deformation while central turkey is characterized by coherent plate motion internal deformation of 2 mm yr involving westward displacement and counterclockwise rotation of the anatolian plate the anatolian plate is de coupled from eurasia along the right lateral strike slip north anatolian fault naf we derive a best fitting euler vector for anatolia eurasia motion of 30 7 0 8 n 32 6 0 4 e 1 2 0 1 myr the euler vector gives an upper bound for naf slip rate of 24 1 mm yr we determine a preliminary gps arabia anatolia euler vector of 32 9 1 2 n 40 3 1 1 e 0 8 0 2 myr and an upper bound on left lateral slip on the east anatolian fault eaf of 9 1 mm yr the central and southern aegean is characterized by coherent motion internal deformation of 2 mm yr toward the sw at 30 1 mm yr relative to eurasia stations in the se aegean deviate significantly from the overall motion of the southern aegean showing increasing velocities toward the trench and reaching 10 1 mm yr relative to the southern aegean as a whole

an assessment of the seismicity of the bursa region from a temporary seismic network a temporary earthquake station network of 11 seismological recorders was operated in the bursa region south of the marmara sea in the northwest of turkey which is located at the southern strand of the north anatolian fault zone nafz we located 384 earthquakes out of a total of 582 recorded events that span the study area between 28 50 30 00 e longitudes and 39 75 40 75 n latitudes the depth of most events was found to be less than 29 km and the magnitude interval ranges were between 0 3 ml 5 4 with rms less than or equal to 0 2 seismic activities were concentrated southeast of uludag mountain um in the kestel igdir area and along the gemlik fault gf in the study we computed 10 focal mechanisms from temporary and permanents networks the predominant feature of the computed focal mechanisms is the relatively widespread near horizontal northwest southeast nw se t axis orientation these fault planes have been used to obtain the orientation and shape factor r magnitude stress ratio of the principal stress tensors 1 2 3 the resulting stress tensors reveal 1 closer to the vertical oriented ne sw and 2 3 horizontal with r 0 5 these results confirm that bursa and its vicinity could be defined by an extensional regime showing a primarily normal to oblique slip motion character it differs from what might be expected from the stress tensor inversion for the nafz different fault patterns related to structural heterogeneity from the north to the south in the study area caused a change in the stress regime from strike slip to normal faulting

pleistocene climatic history of east and central asia based on paleopedological indicators in loess paleosol sequences a micromorphological comparison of the loess paleosol sequence of the karamaydan section central asia with the upper part of the luochuan section china clearly indicates that for the brunhes chron the sequence at karamaydan is more detailed than the corresponding section at luochuan single paleosols at luochuan correspond to pedocomplexes at karamaydan for example s 3 at luochuan corresponds to pk iii and s 4 to pk iv and both pks developed in a period longer than one interglacial about 104 years some pedocomplexes at luochuan are represented by more detailed successions at karamaydan for example the s 5 complex at luochuan corresponds to pedocomplexes v and vi the loess paleosol sequence at karamaydan should therefore be regarded as a key sequence for reconstructing the climatic history of the brunhes epoch correlation with the deep sea oxygen isotope record of bassinot et al which includes an accurate astronomical time scale allows a detailed chronostratigraphical subdivision of the loess paleosol sequence in karamaydan for the brunhes epoch the sequence in the central and lower parts of the chashmanigar section also in central asia shows much more pronounced paleosols than the equivalent sequence at luochuan although some ck or ckm horizons indicate the presence of hiatuses nevertheless for this part of the sequence it provides more paleoclimatic detail with cold dry stages represented by loess and warm humid stages interglacials by paleosols than even the deep sea cores

temporal variations in seismic event rate and b values from stress corrosion constitutive laws abstract main i g meredith p g and sammonds p r 1992 temporal variations in seismic event rate and b values from stress corrosion constitutive laws in t mikumo k aki m ohnaka l j ruff and p k p spudich editors earthquake source physics and earthquake precursors tectonophysics 211 233 246 a model is developed to characterise the state of damage for a fractal population of cracks in terms of a mean energy release rate g which depends on the stress the event rate n and the seismic b value n is assumed to be proportional to the total number of potentially active cracks and b to be proportional to the exponent d of the crack length distribution g is then positively correlated with n and negatively correlated with b consistent with experimental observation based on stress intensity as a constitutive variable the model predicts that higher b values are associated either with lower stress intensity or greater material heterogeneity both experiment and theory predict intermediate term seismic quiescence of similar magnitude to that observed in the field 45 90 for only a small simultaneous reduction in stress and stress intensity 2 7 or the equivalent mean energy release rate the theoretical model predicts three different types of quiescence associated with increasing constant or decreasing b value the first two are associated with stable intermediate term quiescence due to a reduction in g and the third is associated with unstable short term quiescence associated with constant or increasing g the theory can be used to infer relative changes in g from acoustic emissions in the laboratory experiments to date show that quiescence of the order 10 can be seen in the laboratory at strain rates of 10 5 s 1 but that this has the characteristics of short term rather than intermediate term quiescence