asian origin of interannual variations of summer climate over the extratropical north atlantic ocean abstractthe authors have identified an interannual relationship between asian tropospheric temperature and the north atlantic ocean sea surface temperature sst during summer may september and discussed the associated features of atmospheric circulation over the atlantic eurasian region when tropospheric temperature is high low over asia positive negative sst anomalies appear in the extratropical north atlantic this relationship is well supported by the changes in background atmospheric circulation and ocean atmosphere land thermodynamic processes when heat transfer from the land surface to the atmosphere over asia strengthens local tropospheric temperature increases and positive temperature anomalies propagate westward from asia to the north atlantic leading to an increase in summer tropospheric temperature over the atlantic eurasian region accordingly a deep anomalous ridge occurs over the extratropical north atlantic ocean with low level southerly anomalies over the western portion of t

fractal structure of spatial distribution of microfracturing in rock summary a constant stress fracture experiment of oshima granite was carried out at the confining pressure of 40mpa hypocentres of 2064 acoustic emissions were located during the experiment using the correlation integral we found that the spatial distribution of hypocentres of acoustic emission is a fractal and that the fractal dimension decreases with the evolution of rock fracturing the spatial distribution of earthquake s hypocentres reveals fractals ranging from regional to worldwide distribution if we extrapolate from laboratory measurements it is possible to predict the occurrence of large earthquakes by the decrease in the fractal dimension

subtropical anticyclones and summer monsoons the summer subtropical circulation in the lower troposphere is characterized by continental monsoon rains and anticyclones over the oceans in winter the subtropical circulation is more strongly dominated by the zonally averaged flow and its interactions with orography here the mechanics of the summer and winter lowertropospheric subtropical circulation are explored through the use of a primitive equation model and comparison with observations by prescribing in the model the heatings associated with several of the world s monsoons it is confirmed that the equatorward portion of each subtropical anticyclone may be viewed as the kelvin wave response to the monsoon heating over the continent to the west a poleward flowing low level jet into a monsoon such as the great plains jet is required for sverdrup vorticity balance this jet effectively closes off the subtropical anticyclone to the east and also transports moisture into the monsoon region the low level jet into north america induced by its monsoon heating is augmented by a remote response to the asian monsoon heating the rossby wave response to the west of subtropical monsoon heating interacting with the midlatitude westerlies produces a region of adiabatic descent it is demonstrated here that a local diabatic enhancement can lead to a strengthening of the descent longitudinal mountain chains act to block the westerly flow and also tend to produce descent in this region below the descent sverdrup vorticity balance implies equatorward flow that closes off the subtropical anticyclone to the west and induces cool upwelling in the ocean through ekman transport feedbacks involving for example sea surface temperatures may further enhance the descent in these regions the conclusion is that the mediterranean type climates of regions such as california and chile may be induced remotely by the monsoon to the east hence it can be argued that the subtropical circulation in summer comprises a set of weakly interacting monsoon systems each involving monsoon rains a low level poleward jet a subtropical anticyclone to the east and descent and equatorward flow to the west in winter it is demonstrated how the nonlinear interaction between the strong zonal mean circulation associated with the winter hadley cell and the mountains can define many of the large scale features of the subtropical circulation the blocking effect of the longitudinal mountain chains is shown to be very important subsequent diabatic effects such as a local diabatic enhancement would appear to be essential for producing the observed amplitude of these features

ground motions in the fukushima hamadori japan normal faulting earthquake a crustal normal faulting earthquake graphic 1 m w 6 7 occurred in eastern tohoku japan on 11 april 2011 k net and kik net stations recorded 82 records from within 100 km of fault rupture these data and data from associated foreshocks and aftershocks will make a critical contribution to future improvements of ground motion prediction for normal faulting earthquakes peak ground accelerations pga and peak ground velocities pgv are compared with four ground motion prediction equations gmpes that include the style of faulting as a predictor parameter for distances under 100 km and using a network average value of v s 30 the average ratio of pga to the selected gmpes the event term is high by factors of 2 3 3 7 event terms for pgv are high by factors of 1 4 1 8 adjusting pga and pgv with customized site terms kawase and matsuo 2004a b the standard deviations of pga and pgv residuals are reduced from 0 59 to 0 43 and from 0 53 to 0 35 respectively the event terms decreased to relatively small factors of 1 1 1 8 for pga and increased slightly to 1 5 2 0 for pgv thus site terms are very important but positive event terms remain the remaining positive event terms are not explained by high stress drop which was typical of crustal events of all mechanisms globally or in japan two subparallel faults ruptured but source inversions which we reviewed revealed that they ruptured sequentially so simultaneous contributions from the two faults did not cause high motions although these observations may tend to suggest that ground motions in large normal faulting events are larger than predicted by the tested models we are not aware of any observations from this event that contradict the precarious rock evidence of brune 2000 that ground shaking is low on the footwall near the rupture 1 embed inline graphic 1 gif

methodology for obtaining constraints on ground motion from precariously balanced rocks precariously balanced rocks provide constraints on the level of ground motion that could have occurred during the time the rocks have been in their current positions field measurements of the quasi static toppling accelerations of precariously balanced rocks provide information for computer modeling of the response of the rocks to given ground motion histories the quasi static toppling acceleration is determined by the ratio of the quasi static force through the center of mass whose moment about the rocking point counterbalances that of gravity and the mass of the rock for an estimate of dynamic toppling peak ground accelerations we use a finite difference numerical code to model the dynamic response of rocks to arbitrarily complex acceleration time histories we test our computational methodology and results using the university of nevada shake table the shake table tests of both idealized rectangular shapes and actual rocks confirm the accuracy of our methodology for estimating dynamic toppling accelerations of precarious rocks for different waveforms representing earthquake ground motion time histories a study of statistical variation of the dynamic toppling acceleration for a suite of seismograms provides constraints on the peak ground acceleration on hard rock sites in mojave desert about 15 km from the san andreas fault of about 0 5 g for synthetic seismograms with relatively high frequency content or about 0 4 g for seismograms with spectra similar to the recent izmit turkey earthquake a major source of uncertainty is the uncertainty in the spectrum of ground motion for large earthquakes waveforms with relatively more low frequencies can topple the rocks with lower peak ground accelerations we describe methods for reducing the uncertainties with further study and more data

role of atlantic air sea interaction in modulating the effect of tibetan plateau heating on the upstream climate over afro eurasia atlantic regions previous studies have demonstrated that atmospheric diabatic heating over the tibetan plateau tp exerts significant influences on the upstream climate of the atlantic african european sector in boreal summer using the ncar community earth system model this study demonstrates that the tp induced change in north atlantic sea surface temperature sst including evident warming over the mid latitude north atlantic and cooling over the south can in turn modulate the above tp impact compared with the tp heating experiment without atlantic sst variation anomalous wave train pattern appears with north northeastward downstream influences when the change in atlantic sst is considered the wave train pattern is characterized by three positive centers over the north atlantic the arctic ocean and east of japan and four negative centers over northeastern north america north europe the mid atlantic and the northwestern pacific it intensifies the northern portions of the tp induced tropospheric anticyclones over the extratropical north atlantic and the cyclones over northeastern north america and north europe correspondingly precipitation decreases over the northwestern atlantic but increases over northeastern north america and north europe due to the easterly anomalies on the southern side of the weakened thermal low over subtropical africa precipitation over the sahel decreases indicating a weakening of tp induced precipitation dipole over the tropical eastern atlantic and west africa when the atlantic sst influence is considered overall the modulation of atlantic sst variation accounts for above 20 percent of the upstream climate signals induced by the tp thermal effect

the evolution of seismicity at parkfield observation experiment and a fracture mechanical interpretation we compare observations of local seismicity sequences with acoustic emissions during rock fracture and find similarities in the distribution of event magnitudes which lead us to consider a model of seismicity which is characterized by fracture growth laws derived from the field of fracture mechanics and which include both negative and positive feedback processes we find that the model predicts the observed negative correlation between the seismic b value and the fractal dimension of the earthquake epicentres the simple short range interactions described in the model give rise to a system with a long range order similar to current models of critical processes

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

consistency of precariously balanced rocks with probabilistic seismic hazard estimates in southern california abstract the overturning fragility of a freestanding block such as a precariously balanced rock pbr has been parameterized as a function of a vector of ground motion intensity measures methodologies are outlined to estimate the failure probabilities of such objects given their residence times for deterministic seismic hazard analyses dshas a pbr is exposed to the scenario earthquakes that occur during its exposure time providing an estimate of the probability that the pbr survives the ensemble of events for probabilistic seismic hazard analyses pshas the pbr overturning fragility is multiplied by the ground motion occurrence rate from a vector valued probabilistic seismic hazard analysis vpsha yielding the marginal overturning rate for each ground motion bin summing the marginal rates over all ground motion bins produces the total overturning rate for time independent poisson based psha estimates the probability of block failure can be easily calculated as a function of exposure time this latter method is used to test vpsha estimates similar to the 2002 u s geological survey usgs national seismic hazard maps via pbr residence times pbr overturning fragilities are estimated at sites in southern california near the san andreas fault between the san jacinto and elsinore faults and near the white wolf fault the resulting failure probabilities for several of the pbrs are very high suggesting that they are inconsistent with the 2002 usgs ground motions an investigation of the hazard calculated with zero aleatory variability in the ground motion prediction equations gmpes suggests that the median ground motions or the earthquake rupture rates are too high at certain pbr sites

cold season africa asia multidecadal teleconnection pattern and its relation to the atlantic multidecadal variability a prominent teleconnection pattern of multidecadal variability of cold season november to april upper level atmospheric circulation over north africa and eurasia na ea is revealed by empirical orthogonal function analysis of the twentieth century reanalysis data this teleconnection pattern is characterized by an eastward propagating wave train with a zonal wavenumber of 5 6 between 20 and 40 n extending from the northwest coast of africa to east asia and thus is referred to as the africa asia multidecadal teleconnection pattern aamt one point correlation maps show that the teleconnectivity of aamt is strong and further demonstrate the existence of the aamt the aamt shapes the spatial structure of multidecadal change in atmospheric circulation over the na ea region and in particular the aamt pattern and associated fields show similar structures to the change occurring around the early 1960s a strong in phase relationship is observed between the aamt and atlantic multidecadal variability amv and this connection is mainly due to rossby wave dynamics barotropic modeling results suggest that the upper level rossby wave source generated by the amv can excite the aamt wave train and rossby wave ray tracing analysis further highlights the role of the asian jet stream in guiding the wave train to east asia the aamt acts as an atmospheric bridge conveying the influence of amv onto the downstream multidecadal climate variability the amv is closely related to the coordinated change in surface and tropospheric air temperatures over northwest africa the arabian peninsula and central china which may result from the adiabatic expansion compression of air associated with the aamt

modulation of the tibetan plateau snow cover on the enso teleconnections from the east asian summer monsoon perspective theeastasiansummermonsoon easm mayexhibitratherlargevariabilitybetweenyearscharacterized by the same enso phase such inconsistency reduces the easm predictability based on enso results in this study show that the tibetan plateau snow cover tpsc exerts a modulating effect on enso teleconnections and enso significantly correlates with the easm only during the reduced tpsc summers three dimensional circulation structures are examined to manifest that the typical enso signals in reduced tpsc summers tend to be stronger than in excessive tpsc summers numerical and theoretical evidences indicate that the anomalously reduced tpsc can force positive geopotential height anomalies at the upper troposphereandweakenthejetstreamsacrosseasternasiaandnorthwesternpacific governedbysuchbasic state zonal flows the extratropical rossby wave response to the enso forcing usually has a larger amplitude and pronounced westward development in such case enso extends its influences to eastern asia and enhances its connection with the easm

estimating erosion rates and exposure ages with 36cl produced by neutron activation the isotopic composition of water soluble cl extracted from mineral grains in granitic rocks appears to reflect the relative age of debris flow fan surfaces and the erosion rate of bedrock outcrops our data indicate that some granitic landforms are stable landscape elements eroding on the order of meters to tens of meters per million years samples collected from debris flow fan surfaces of three distinct relative ages show the expected increase of model age with time but the 36cl exposure ages for boulders on any particular surface vary by a factor of more than five the method we used for extracting cl was designed to isolate the 35cl n 36cl production pathway and to simplify the chemical preparation of samples such isolation from fluid inclusions allows direct interpretation of measured 36cl cl ratios but requires a model to predict the thermal neutron production and absorption profile below the rock surface using such a model we find good agreement between measured and predicted 36cl cl for eight samples collected below the ground surface as well as consistency between several groups of samples collected near one another using elemental abundance data for 129 granitic rocks we modeled 36cl cl supported by radiogenic neutrons and find that it varies from 4 to 125 10 15 mean 21 18 1 however from the surface to a depth of 10 m thermal neutrons resulting from muon interactions have the potential to generate more 36cl than do radiogenic neutrons the production of 36cl in the subsurface has important implications for surface exposure dating of young low altitude samples collected from moraines and debris flow or alluvial fans especially at ages where erosion of the boulder surface is significant or where the source area for boulders is at altitudes much higher than the landform to be dated

sea surface temperature fields associated with west african rainfall anomaly types abstract four west african rainfall anomaly types are defined in relation to the northern summer rainfall departure signs in the sahel and in the guinean region in order to investigate the statistical links between interannual variability of west african rainfall and sea surface temperature sst through the period 1950 90 composite analysis depicts the setup of four different mean sst anomaly fields drought over all of west africa is associated with the growth of positive sst anomalies in the eastern pacific and in the indian ocean and negative sst anomalies in the northern atlantic and in the gulf of guinea in contrast drought limited to the sahel corresponds mostly to a northward expansion of positive sst anomalies in the southern atlantic and negative sst anomalies in the northern atlantic northward expansion of negative sst anomalies in the southern atlantic positive sst departures in the northern atlantic and development of negative sst anomalies in the eastern pacific appear to be synchron

monsoons and the dynamics of deserts the existence of subtropical deserts such as the sahara has often been attributed to the annual mean zonal mean hadley circulation which shows strong descent in the subtropics however the zonal mean hadley circulation shows considerable evolution over the course of the year with very strong subtropical descent during winter but practically no zonal mean subtropical descent during summer when rainfall over the eastern sahara and the mediterranean is least charney 1975 proposed a biosphere albedo feedback mechanism whereby local anthropogenic effects related to over grazing could affect the radiative balance enhancing summertime diabatic descent and leading to desertification of the subtropics in general the present study which uses an idealized model suggests a monsoon desert mechanism for desertification whereby remote diabatic heating in the asian monsoon region can induce a rossby wave pattern to the west integral with the rossby wave solution is a warm thermal structure that interacts with air on the southern flank of the mid latitude westerlies causing it to descend this adiabatic descent is localized over the eastern sahara and mediterranean and over the kyzylkum desert to the south east of the aral sea by the mountains of north africa and south west asia trajectories indicate that the monsoon desert mechanism does not represent a simple walker type overturning cell instead the descending air is seen to be mainly of mid latitude origin it is speculated that the monsoon forced adiabatic descent may result in clear air and therefore a local diabatic enhancement which effectively doubles the strength of descent with this mechanism desertification can be forced by remote changes in monsoon strength rather than by local effects this conclusion is supported by the observed dramatic strengthening of descent over the mediterranean and east sahara during the onset of the asian monsoon and on the longer timescale by relating prehistoric lake levels to milankovitch monsoon forcing the latter may help to explain the perceived discrepancies between the palaeoclimate of the eastern sahara and the strength of a tropic wide monsoon the monsoon desert mechanism may not be confined to the asian monsoon alone and the existence of other monsoon climate regions over the globe may in a similar way explain the observed summertime strengthening of the oceanic sub tropical anticyclones and the existence of western continental deserts and mediterranean type climate regions

interannual variability of the spring atmospheric heat source over the tibetan plateau forced by the north atlantic ssta data analysis indicates that the interannual variability of the spring atmospheric heat source over the tibetan plateau tp depends largely on the intensity of the overlying subtropical westerly jet wj which is closely related to the early spring february march april sea surface temperature anomaly ssta tripole pattern over the north atlantic i e the ssta tripole pattern with a warm core to the southeast of newfoundland and two cold cores to the south of iceland and southeast of bermuda respectively such an ssta pattern can be regarded as a response to the atmospheric forcing of the preceding january february march north atlantic oscillation numerical experiment results from both linear baroclinic model with an idealized diabatic heating profile and an atmospheric general circulation model with prescribed ssta forcing demonstrate that the warm core alone of the tripole pattern can stimulate a steady downstream rossby wave train which further intensifies the spring wj over the tp as a result a positive anomaly of surface sensible heating occurs over most parts of the tp whereas the precipitation and corresponding latent heating is characterized by a seesaw pattern with a positive negative anomaly over the northern southern tp meanwhile the air column radiation cooling effect is enhanced to a certain degree over the plateau further analysis suggests that the early spring ssta over the north atlantic may exert a seasonal lagged impact upon the east asian summer monsoon by modulating the thermal forcing over the tp

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

precursory seismicity changes associated with the mw 7 4 1999 august 17 izmit turkey earthquake summary we investigated precursory seismicity in and around the epicentral zone of the mw 7 4 1999 august 17 izmit turkey earthquake by applying a statistical method the rtl region time length algorithm to earthquake catalogues derived from that for the period 1981 1999 of kandilli observatory and earthquake research institute koeri the derived catalogues are complete for events md 3 in most of western turkey after declustering aftershocks we investigated the seismicity patterns preceding the izmit event at local izmit tectonic zone and national turkey scales the rtl parameter indicates that a period of seismic quiescence started at the end of 1995 and reached a minimum in december 1996 an activation phase lasting about three months followed the main shock in izmit and vicinity did not occur when the seismicity returned to its background level but occurred with a delay of nearly 2 5 yr we present a new parameter to quantify the spatial distribution of seismic quiescence the results from both catalogues indicate that a significant quiescence anomaly appeared in 1996 around the epicenter of the izmit earthquake the primary characteristics of the seismicity patterns prior to the izmit earthquake are similar to those obtained for large events in russia and japan the variations of seismicity patterns revealed by the rtl algorithm may offer better understanding of the physical nature of seismo tectonics and provide useful information for seismic hazard estimation the varying characteristics of the izmit and other events may reflect the difference between seismo tectonics in turkey and in other regions such as russia and japan

eigenoscillations and stability of rocking stones the case study of the hus pulpit in the central bohemian pluton stability of precariously balanced rocks is employed in seismic hazard estimates standard toppling models of these rocks are based on a rigid body motion i e this approximation assumes that their eigenfrequencies are infinite in any position of a rock this assumption is however questionable in the case of rocking stones oscillating with lowest eigenfrequencies of only several hertz when resonance effects facilitating rolling wobbling due to a seismic signal cannot be a priori excluded an example demonstrating existence of such low frequencies is the hus pulpit rocking stone located in the central bohemian pluton 49 568n 14 363e the observed lowest frequencies recorded by a guralp cmg 40t seismometer located on the top of this rocking stone are 3 7 and 9 hz with the quality factors of 60 55 and 77 respectively using the comsol multiphysics software package we model the oscillations of this rocking stone numerically and demonstrate that these observed low frequencies and their dampings can be explained by a force interaction between the stone base and the bedrock that can formally be interpreted as the damped elastic response of the bedrock to its surface deformation by the stone we also numerically study stability of the stone under the presence of such an interaction and conclude that beginning of toppling requires very high horizontal pgv pga for input seismic frequencies even at the resonance frequencies however different numerical models where the seismic displacements are considered as the direct input at the rock base can result in rock instabilities under a presence of an hbox m 7 earthquake at a distance of about 150 km

observed impact of atlantic sst anomalies on the north atlantic oscillation the large scale patterns of covariability between monthly sea surface temperature sst and 500 mb height anomalies z500 in the atlantic sector are investigated as a function of time lag in the ncep ncar reanalysis 1958 97 in agreement with previous studies the dominant signal is the atmospheric forcing of sst anomalies but statistically significant covariances are also found when sst leads z500 by several months in winter a panatlantic sst pattern precedes the north atlantic oscillation nao by up to 6 months such long lead time covariance is interpreted in the framework of the stochastic climate model reflecting the forcing of the nao by persistent atlantic sst anomalies a separate analysis of midlatitudes 208 708n and tropical 208s 208n sst anomalies reveals that the bulk of the nao signal comes from the midlatitudes a dipolar anomaly with warm sst southeast of newfoundland and cold sst to the northeast and southeast precedes a positive phase of the nao and it should provide a prediction of up to 15 of its monthly variance several months in advance since the forcing sst pattern projects significantly onto the tripole pattern generated by the nao these results indicate a positive feedback between the sst tripole and the nao with a strength of up to 25 mk 21 at 500 mb or 2 3 mb k21 at sea level additionally a warming of the tropical atlantic 208s 208n roughly symmetric about the equator induces a negative nao phase in early winter this tropical forcing of the nao is nearly uncorrelated with and weaker than that resulting from the midlatitudes and is associated with shorter lead times and reduced predictive skill

rocking and overturning of precariously balanced rocks by earthquakes abstract precariously balanced rocks in seismically active regions may be used to provide constraints on probabilistic estimates of strong ground motion a computer program is developed to study the rocking response of models of precariously balanced rocks when subjected to various levels of ground accelerations the computer code validated by comparing the numerical and experimental results for simple shaped rigid blocks is used to study the rocking response of rectangular blocks with various aspect ratios to the el centro strong ground motion recording of the 18 may 1940 imperial valley earthquake results show that during earthquakes the horizontal components of ground motion play a dominant role in overturning rocking objects the rederived and corrected housner9s equation 1963 could be used to estimate the minimum overturning acceleration of precarious rocks at different frequencies by measuring the quasi static toppling acceleration in the field

spatial variations of the fractal properties of seismicity in the anatolian fault zones abstract the anatolian fault zones are seismically active strike slip fault zones transcending the anatolian plate in e w and n s directions we investigate the spatial variations of seismicity along these zones in an attempt to investigate fault complexity along strike quantified by the gutenberg richter b value and the fractal correlation dimension of earthquake epicentres using the maximum likelihood method and the correlation integral respectively the investigation covers instrumentally recorded carthquakes of magnitude m 4 5 occurring between 1900 and 1992 we find systematic spatial variations which may be related to structural or mechanical variability along strike in particular the large change in strike at the northern apex of the north anatolian fault zone is associated with the highest correlation dimension and lowest b value for seismicity this century the correlation dimension and b value show a negative correlation with respect to each other similar to results reported in other regional studies of japan and southern california this statistical correlation is stronger when more objective seismic zoning is carried out based on number of events rather than more subjective seismotectonic zoning in common use in seismic hazard analysis

partitioning of strike slip and convergent motion between eurasia and arabia in eastern turkey and the caucasus the plate motion model nuvel 1 de mets et al 1990 predicts a strongly oblique component to the convergence between arabia and eurasia at the longitude of the caucasus earthquake focal mechanisms suggest that this oblique convergence is partitioned into pure right lateral strike slip motion in eastern turkey and pure shortening by thrusting in the greater caucasus such partitioning offers an explanation for the apparent eastward continuation of the right lateral faulting of the north anatolian fault from turkey into iran from a summation of seismic moment tensors between 1911 and 1991 it appears that most of the right lateral strike slip motion in eastern turkey is accommodated by faulting in large earthquakes while most of the shortening in the caucasus appears to occur aseismically

methodology for using precarious rocks in nevada to test seismic hazard models abstract fields of precariously balanced rocks indicate that strong earthquake motions have not occurred at that site since the precarious rocks developed these fields can be characterized with an estimate of the peak acceleration that would be sufficient to topple the rocks and an estimate of how long the rocks have been precarious this article uses this information to test the input to probabilistic seismic hazard analysis the fundamental assumption is that the probability of exceeding a ground motion capable of toppling a precarious rock during a time period equal to the age of the rock is equal to the confidence level at which the inputs to the probabilistic seismic hazard analysis can be rejected we performed a probabilistic seismic hazard analysis for 26 sites of observed precarious rocks in nevada using preliminary estimates of the toppling acceleration and the age of the features two standard models are rejected with over 95 confidence by most of the precarious rock observations we consider several possible explanations for the inconsistency a probabilistic seismic hazard analysis that eliminates the area sources and only includes faults is consistent with the precarious rock observations at most of the sites spatial clustering of small magnitude events could maintain this effect without contradicting the precarious rock observations however it may not be necessary to completely reject the area sources from our probabilistic seismic hazard analysis the physics of rock stability may allow increasing the minimum magnitude to 6 0 in the area sources because the short duration of high frequency accelerations in smaller events may not topple all precarious rocks the precarious rocks could generally have small site effects attenuation models may overestimate ground motions on the foot wall of normal faults and a different attenuation model in general might decrease the ground motion predictions the ergodic assumption that is made in estimating the uncertainty in attenuation models may be contributing to overestimate the hazard individually each of these effects might allow more of the precarious rock sites to be consistent with the area source zones

anomalous seismicity preceding the 1999 izmit event nw turkey summary the 1999 izmit earthquake 1999 august 17 mw 7 4 was one of the largest earthquakes to occur in northwestern turkey during the past 100 yr this earthquake occurred along the izmit sapanca fault within the northern anatolian fault zone variations in the generalized fractal dimensions dq of clustering in time and space the gutenberg richter b value and earthquake frequency n are evaluated in detail over an 8 5 yr time period preceding the izmit event spatial and temporal comparisons of the variations in these parameters reveal anomalous intermediate term behaviour over shorter timescales than previously observed significant correlation is observed between changes in b value with the spatial and temporal fractal dimension of epicentre distribution these correlations oscillate back and forth over 2 3 yr time intervals and suggest occurrence of significant instability in the nature of intermediate term deformation along the fault zone seismotectonic behaviour immediately preceding the izmit event is represented by a significant rise in b value to a maximum of 2 26 accompanied by relatively small increases in d the rapid rise of b is associated with an increased frequency of low magnitude seismicity although d spatial and temporal increase slightly in the 2 3 yr period preceding rupture they remain less than 1 indicating that seismicity remains clustered prior to rupture in areas where earthquake frequency or station density do not permit resolution of short term variations of fractal scaling parameters within a few months of main rupture an accelerated period of low magnitude seismicity high b value concentrated along a fault zone d 1 may suggest heightened probability of a forthcoming large event

remotely forced variability in the tropical atlantic ocean an ensemble of eight hindcasts has been conducted using an ocean atmosphere general circulation model fully coupled only within the atlantic basin with prescribed observational sea surface temperature sst for 1950 1998 in the global ocean outside the atlantic basin the purpose of these experiments is to understand the influence of the external sst anomalies on the interannual variability in the tropical atlantic ocean statistical methods including empirical orthogonal function analysis with maximized signal to noise ratio have been used to extract the remotely forced atlantic signals from the ensemble of simulations it is found that the leading external source on the interannual time scales is the el nino southern oscillation enso in the pacific ocean the enso signal in the tropical atlantic shows a distinct progression from season to season during the boreal winter of a maturing el nino event the model shows a major warm center in the southern subtropical atlantic together with warm anomalies in the northern subtropical atlantic the southern subtropical sst anomalies is caused by a weakening of the southeast trade winds which are partly associated with the influence of an atmospheric wave train generated in the western pacific ocean and propagating into the atlantic basin in the southern hemisphere during boreal fall in the boreal spring the northern tropical atlantic ocean is warmed up by a weakening of the northeast trade winds which is also associated with a wave train generated in the central tropical pacific during the winter season of an el nino event apart from the atmospheric planetary waves these sst anomalies are also related to the sea level pressure slp increase in the eastern tropical atlantic due to the global adjustment to the maturing el nino in the tropical pacific the tropical slp anomalies are further enhanced in boreal spring which induce anomalous easterlies on and to the south of the equator and lead to a dynamical oceanic response that causes cold sst anomalies in the eastern and equatorial atlantic from boreal spring to summer most of these sst anomalies persist into the boreal fall season

faster better shear wave velocity to 100 meters depth from refraction microtremor arrays current techniques of estimating shallow shear velocities for assessment of earthquake site response are too costly for use at most construction sites they require large sources to be effective in noisy urban settings or specialized independent recorders laid out in an extensive array this work shows that microtremor noise recordings made on 200 m long lines of seismic refraction equipment can estimate shear velocity with 20 accuracy often to 100 m depths the combination of commonly available equipment simple recording with no source a wavefield transformation data processing technique and an interactive rayleigh wave dispersion modeling tool exploits the most effective aspects of the microtremor spectral analysis of surface wave sasw and multichannel analysis of surface wave masw techniques the slowness frequency wavefield transformation is particularly effective in allowing accurate picking of rayleigh wave phase velocity dispersion curves despite the presence of waves propagating across the linear array at high apparent velocities higher mode rayleigh waves body waves air waves and incoherent noise two locations illustrate the application of this technique in detail coincident with a large accelerometer microtremor array in reno nevada and atop a borehole logged for shear velocity in newhall california refraction equipment could duplicate microtremor results above 3 hz but could not estimate velocities deeper than 100 m refraction microtremor cannot duplicate the detail in the velocity profile yielded by a suspension logger but can match the average velocity of 10 to 20 m depth intervals and suggest structure below the 100 m logged depth of the hole eight additional examples from southern california and new zealand demonstrate that the refraction microtremor technique quickly produces good results from a wide range of hard and soft sites

on the role of sea surface temperature gradients in forcing low level winds and convergence in the tropics abstract we examine the importance of pressure gradients due to surface temperature gradients to low level p 700 mb flow and convergence in the tropics over time scales 1 month the latter plays a crucial role in determining the distribution of cumulonimbus convection and rainfall our approach is to consider a simple one layer model of the trade cumulus boundary layer wherein surface temperature gradients are mixed vertically consistent with ecmwf analyzed data the top of the layer is taken at 700 mb the influence from higher levels is intentionally suppressed by setting horizontal pressure gradients and frictional stresses to zero at the top of the layer horizontal convergence within the layer is taken up by cumulonimbus mass flux however the development of the cumulonimbus mass flux is associated with a short relaxation time o hr roughly the development time for such convection during this short time horizontal convergence acts to redistribute mass so as to reduce horizontal pressur

on the three dimensional propagation of stationary waves abstract a locally applicable nonzonally averaged conservation relation is derived for quasi geostrophic stationary waves on a zonal flow a generalization of the eliassen palm relation the flux which appears in this relation constitutes it is argued a useful diagnostic of the three dimensional propagation of stationary wave activity this is illustrated by application to a simple theoretical model of a forced rossby wave train and to a northern hemisphere winter climatology results of the latter procedure suggest that the major forcing of the stationary wave field derives from the orographic effects of the tibetan plateau and from nonorographic effects diabatic heating and or interaction with transient eddies in the western north atlantic and north pacific oceans and siberia no evidence is found in the data for wave trains of tropical origin forcing by the orographic effects of the rocky mountains seems to be of secondary importance

new constraints on micro seismicity and stress state in the western part of the north anatolian fault zone observations from a dense seismic array with the aim of extensively investigating the crustal structure beneath the western segment of the north anatolian fault zone where it splays into northern and southern branches a temporary seismic network dense array for north anatolia dana consisting of 70 stations was deployed in early may 2012 and operated for 18 months in the sakarya region during the faultlab experiment out of 2437 events contaminated by explosions we extracted 1371 well located earthquakes the enhanced station coverage having a nominal station spacing of 7 km lead to a minimum magnitude calculation of 0 1 horizontal and vertical location uncertainties within the array do not exceed 0 8 km and 0 9 km respectively we observe considerable seismic activity along both branches of the fault where the depth of the seismogenic zone was mostly confined to 15 km using our current earthquake catalog we obtained a b value of 1 we also mapped the b value variation with depth and observed a gradual decrease furthermore we determined the source parameters of 41 earthquakes with magnitudes greater than 1 8 using p wave first motion polarity method regional moment tensor inversion method was also applied to earthquakes with magnitudes greater than 3 0 focal mechanism solutions confirm that sakarya and its vicinity is stressed by a compressional regime showing a primarily oblique slip motion character stress tensor analysis indicates that the maximum principal stress is aligned in wnw ese direction and the tensional axis is aligned in nne ssw direction

estimates of the ground accelerations at point reyes station during the 1906 san francisco earthquake we have developed an analytical solution for the rocking and overturning response of a two dimensional symmetric rigid block subject to a full sine wave of horizontal ground acceleration we use this solution to provide lower bound estimates of the peak ground acceleration at point reyes station california during the 1906 san francisco earthquake that toppled the san francisco bound train our results for a 3 damping ratio indicate that for a single cycle of a sine wave the minimum toppling accelerations at 1 1 5 and 2 hz are 0 35g 0 5g and 1 05g respectively for more realistic accelerograms the toppling accelerations are about 1 1g complex synthetic and 0 76g lucerne record of the 1992 landers earthquake

impact of the atlantic multidecadal oscillation on the asian summer monsoon 1 the impact of the atlantic multidecadal oscillation amo on the asian summer monsoon is investigated using a coupled atmosphere ocean global general circulation model by imposing the amo associated sea surface temperature anomalies in the atlantic as boundary forcing and allowing atmosphere ocean interactions outside the atlantic the positive amo phase characterized by anomalous warm north atlantic and cold south atlantic leads to strong southeast and east asian summer monsoons and late withdrawal of the indian summer monsoon these changes of monsoons are mainly through coupled atmosphere ocean feedbacks in the western pacific and indian oceans and tropospheric temperature changes over eurasia in response to the imposed forcing in the atlantic the results are in agreement with the observed climate changes in china corresponded to the amo phases they suggest a non local mechanism for the asian summer monsoon variability and provide an alternative view to understanding its interdecadal variation during the twentieth century citation lu r b dong and h ding 2006 impact of the atlantic multidecadal oscillation on the asian summer monsoon geophys res lett 33 l24701 doi 10 1029 2006gl027655

assessment of the site conditions of precariously balanced rocks in the mojave desert southern california we examine whether groups of precariously balanced rocks in the mo jave desert southern california may have remained standing for thousands of years because anomalous site conditions prevent the rocks from toppling during large earth quakes measurements of peak ground velocity at bandwidths of 0 5 1 1 2 2 4 4 8 and 8 16 hz for 56 earthquakes ml 3 5 4 8 at two sites of precarious rocks are compared with velocities recorded for the same earthquakes by three tri net stations located on engineering rock national earthquake hazard reduction program nehrp site class b we find that the residuals the logarithm of the ratio of the amplitudes recorded at the precarious rock sites to the trinet amplitudes for the same earthquake and epicentral distance at frequencies less than about 4 hz are negative i e deamplification of 50 250 whereas the residuals are slightly positive at the higher frequencies i e amplification of up to 25 50 high frequency ground motions e g peak ground acceleration may therefore be slightly amplified at the precarious rock sites which means that site conditions do not appear to explain the existence of the precarious rocks in areas where high peak ground accelerations are predicted in recent probabilistic seismic hazard psh models this discrepancy between the precarious rocks and the psh models should be urgently resolved

evidence for precursory changes in the frequency magnitude b value summary a clear case has been established for a significant increase in the slope of the frequency magnitude relation for periods of up to six years before a number of earthquakes in new zealand and california in a region of about 200 km diameter in central new zealand the b value increased from near unity to more than 2 0 at the end of 1968 and remained abnormally high until the beginning of 1975 an earthquake of magnitude 6 0 followed in 1977 january within 50 km of the location which had registered the highest b value the anomaly was detected in contour maps of b values windowed in space and time then resolved more precisely in time using the cusum technique it was statistically significant at a level higher than 99 99 per cent compared with the average rate of moment release in this region there was a deficit of 1 3 x 10 nm during the anomalous period which is equivalent to an earthquake of magnitude 6 08 this phenomenon of a high b value has been found before all shallow new zealand earthquakes of magnitude 6 0 or more since 1965 wherever the seismicity rate and detection threshold were adequate to resolve it further the only statistically significant occurrences of high b value were those which were followed by large earthquakes two of magnitude 6 8 and 6 0 and a swarm of equivalent magnitude 5 3 the phenomenon has also been found before the san fernando and coalinga earthquakes in california both of which were thrust events but it is not apparent before two large californian earthquakes with strike slip mechanisms observations of high b value are consistent with reported instances of quiescence in background seismicity in fact what has been interpreted as quiescence may probably be more accurately described as a localized high b value the duration of the anomaly is not a simple function of magnitude different strain rates in the regions examined may account for this the available data suggest that careful monitoring of the b value may provide a tool for medium term earthquake prediction although perhaps not in all tectonic environments

fractal geometry in the san andreas fault system it has been noted that the spatial distribution of earthquakes and the mode of strain release in the san andreas fault system is related to the complexity of fault geometry because of their rough appearance over many length scales faults can be regarded as fractal surfaces direct estimates of fractal dimension d of portions of the san andreas fault system between the northern gabilan range and the salton sea including the postulated extent of the great 1857 fort tejon earthquake are obtained from measured fault lengths analogous to the lengths of coastlines as discussed by mandelbrot regions characterized by complicated fault geometry are associated with larger values of d based on fault traces mapped at a scale of 1 750 000 d is 1 3 for this reach of the fault defined as a 30 km wide band about a main fault trace for that part near parkfield which could be associated with the nucleation of the 1857 earthquake d is 1 1 at this same scale d is 1 4 for the san andreas and related faults near san bernardino where the 1857 rupture stopped compared to 1 2 for the san andreas san juan fault segments near the point of arrest of the 1966 parkfield earthquake at finer map scales 1 24 000 and 1 62 500 critical lengths of 500 m and 1 km are identified which might relate to the extent of off san andreas fault offsets the critical lengths also suggest that fault geometry is not self similar if this fractal geometry persists through the seismic cycle it may be possible to use a quantitative measure of complexity to explain the occurrence of great and characteristic earthquakes along a given reach of fault

a correlation between the b value and the fractal dimension from the aftershock sequence of the 1999 chi chi taiwan earthquake summary we analyse large number of aftershock events from the 1999 chi chi taiwan earthquake m l 7 3 recorded around the epicentre area of the main shock in central taiwan where events can be precisely located due to dense coverage of modern seismometers the seismicity is characterized by the b value of the gutenberg richter relation and the fractal correlation dimension d of earthquake hypocenters calculated from sliding windows containing more than 100 events over a span of 6 months after the main shock we find a positive correlation between b and d from the aftershock sequence our result thus suggests that aki s relation d 3b c could be possibly applied to one single fracturing process and its related aftermath

precarious rock evidence for low near source accelerations for trans tensional strike slip earthquakes abstract this paper describes precarious rock evidence for low ground motions associated with extensional sections of strike slip faults recent evidence from physical and numerical models and data regressions has indicated that ground motion for extensional strike slip regions may be lower than for strike slip faults with a large fault normal tectonic stress component and for thrust faults in general data from compressional strike slip and thrust earthquakes dominates the database used in most regression curves for ground acceleration and in the calculation of current probabilistic seismic hazard maps therefore estimates of ground accelerations on these seismic hazard maps may be too high for sites near extensional sections of strike slip faults this paper discusses precariously balanced rock data from three areas near extensional sections of strike slip faulting 1 the region of the honey fault california with an active holocene fault 2 the red rock canyon region of the garlock fault near a dilatational step over and 3 the region just south of beaumont california near the hemet dilatational step over in the san jacinto fault these are all active strike slip faults with at least a few large earthquakes in the holocene and in the case of the san jacinto example historic large earthquakes m 7 thus the precarious rocks at these sites are evidence of relatively low ground motions associated with extensional strike slip faulting the results of this study could be very important in developing more detailed seismic hazard maps in the future

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

precarious rock evidence for low ground shaking on the footwall of major normal faults preliminary interpretations of precarious rock observations suggest relatively low near fault 3 km footwall ground motions for normal faults relative to strike slip faults as reported for a dynamic foam rubber normal fault model by brune and anooshehpoor 1999 since for large normal fault earthquakes there are no instrumental data at such close distances from the fault trace precarious rocks may provide important data for estimating the ground motion for these earthquakes use of empirical curves in the literature based mainly on strike slip data may lead to overestimates of seismic hazard for the near fault footwall of normal faults these preliminary results may warrant more comprehensive and more quantitative followup studies

precarious rock and overturned transformer evidence for ground shaking in the ms 7 7 kern county earthquake an analog for disastrous shaking from a major thrust fault in the los angeles basin precariously balanced rocks and overturned transformers in the vicinity of the white wolf fault provide constraints on ground motion during the 1952 m s 7 7 kern county earthquake a possible analog for an anticipated large earthquake in the los angeles basin shaw et al 2002 dolan et al 2003 on the northeast part of the fault preliminary estimates of ground motion on the footwall give peak accelerations considerably lower than predicted by standard regression curves on the other hand on the hanging wall there is evidence of intense ground shattering and lack of precarious rocks consistent with the intense hanging wall accelerations suggested by foam rubber modeling numerical modeling and observations from previous thrust fault earthquakes there is clear evidence of the effects of rupture directivity in ground motions on the hanging wall side of the fault from both precarious rocks and numerical simulations on the southwest part of the fault which is covered by sediments the thrust fault did not reach the surface blind thrust overturned and damaged transformers indicate significant transfer of energy from the hanging wall to the footwall an effect that may not be as effective when the rupture reaches the surface is not blind transformers near the up dip projection of the fault tip have been damaged or overturned on both the hanging wall and footwall sides of the fault the transfer of energy is confirmed in a numerical lattice model and could play an important role in a similar situation in los angeles we suggest that the results of this study can provide important information for estimating the effects of a large thrust fault rupture in the los angeles basin specially given the fact that there is so little instrumental data from large thrust fault earthquakes

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

possible effect of the tibetan plateau on the upstream climate over west asia north africa south europe and the north atlantic we conduct several experiments using a fully coupled climate model to understand the role of tibetan plateau tp surface heating in the climate variations over west asia south europe north africa and the north atlantic during summer emphasis has been placed on the physical processes and responsible mechanisms that involve the shift of the hadley cell and the important features of rotational and divergent response of the atmosphere to the tp heating the relative importance of the tp to the asian continent is also analyzed a heating of the tp surface leads to local increases in tropospheric temperature and the thickness of the air column due to the so called air pumping effect in the upper troposphere the south asian high intensifies and extends westward to the west of tp especially in west asia south europe north africa and the north atlantic distinguished rossby wave responses to the tp heating occur with anomalous high pressure and uniform warming in the entire troposphere correspondingly descending motions intensify and precipitation decreases however the tropical sahel rainfall increases because of a northward shift of the atlantic intertropical convergence zone and the anomalous westerlies due to the weakening of the southeastern portion of the atlantic subtropical high these effects of the tp heating explain a remarkable portion of the effects by the asian continent heating in addition the impacts of different magnitudes of tp surface heating are also discussed

the major asperities of the 1999 mw 7 4 izmit earthquake defined by the microseismicity of the two decades before it

reply to comment by j zhang and n makris on estimates of the ground accelerations at point reyes station during the 1906 san francisco earthquake by a anooshehpoor t h heaton b shi and j n brune contrary to the comments by zhang and makris hereafter zm our equations of motion governing the rocking response of a rectangular block subjected to a full sine acceleration pulse are correct therefore the first part of zm s discussion which is based primarily upon the assumption that the equations of motion in our article were incorrect is inappropriate in the second part of the discussion zm present new results for mode 2 toppling without impact we did not consider this mode because it was not relevant to the point reyes train which by eyewitness accounts had overturned after experiencing one impact however as explained in this reply toppling with no impact is never the minimum condition for overturning and would in general involve very large horizontal accelerations especially at frequencies where mode 2 is the only overturning mode

low footwall accelerations and variable surface rupture behavior on the fort sage mountains fault northeast california the fort sage mountains fault zone is a normal fault in the walker lane of the western basin and range that produced a small surface rupture 20 cm during an m l 5 6 earthquake in 1950 we investigate the paleoseismic history of the fort sage fault and find evidence for two paleoearthquakes with surface displacements much larger than those observed in 1950 rupture of the fort sage fault 5 6 ka resulted in surface displacements of at least 0 8 1 5 m implying earthquake moment magnitudes m w of 6 7 7 1 an older rupture at 20 5 ka displaced the ground at least 1 5 m implying an earthquake of m w 6 8 7 1 a field of precariously balanced rocks pbrs is located less than 1 km from the surface rupture trace of this holocene active normal fault ground motion prediction equations gmpes predict peak ground accelerations pgas of 0 2 0 3 g for the 1950 rupture and 0 3 0 5 g for the 5 6 ka paleoearthquake one kilometer from the fault surface trace yet field tests indicate that the fort sage pbrs will be toppled by pgas between 0 1 0 3 g we discuss the paleoseismic history of the fort sage fault in the context of the nearby pbrs gmpes and probabilistic seismic hazard maps for extensional regimes if the fort sage pbrs are older than the mid holocene rupture on the fort sage fault zone this implies that current gmpes may overestimate near fault footwall ground motions at this site

dating precariously balanced rocks in seismically active parts of california and nevada precariously balanced boulders that could be knocked down by strong earthquake ground motion are found in some seismically active areas of southern california and nevada in this study we used two independent surface exposure dating techniques rock varnish microlamination and cosmogenic 36 cl dating methodologies to estimate minimum and maximum limiting ages respectively of the precarious boulders and by inference the elapsed time since the sites were shaken down the results of the exposure dating indicate that all of the precarious rocks are 10 5 ka and that some may be significantly older at victorville and jacumba california these results show that the precarious rocks have not been knocked down for at least 10 5 k y a conclusion in apparent conflict with some commonly used probabilistic seismic hazard maps at yucca mountain nevada the ages of the precarious rocks are 10 5 to 27 0 ka providing an independent measure of the minimum time elapsed since faulting occurred on the solitario canyon fault

blind testing of rock varnish microstratigraphy as a chronometric indicator results on late quaternary lava flows in the mojave desert california rock varnish is a manganiferous dark coating ubiquitous in desert landscapes to test the validity of varnish microstratigraphy as a chronometric indicator varnish samples were collected from radiometrically dated and undated late quaternary lava flows in amboy cima and pisgah volcanic fields avf cvf pvf in the mojave desert of california western united states varnish microstratigraphies show a replicable layering sequence that appears to record regional climate changes that likely correspond in time to the younger dryas and heinrich events in the north atlantic region microstratigraphic patterns on these volcanic fields match patterns found in varnishes from other western us sites with available radiometric age constraints based on this regional chronology varnishes from the a flow h flow and a stone pavement surface in the cima volcanic field were estimated to be 16 5 24 74 85 and 74 85 ka respectively these ages are consistent with previously published cosmogenic 3 he ages of 18 20 72 74 and 80 85 ka for these geomorphic surfaces varnishes from the i flow at cima yielded a puzzling age estimate of 39 ka which is consistent with an older 3 he age of 37f6 ka reported for the i flow but inconsistent with a younger 3 he age of 31f7 ka and a cosmogenic 36 cl age of 27f1 3 ka for the same flow reinterpretation of the original varnish age data with knowledge of then available field mapping results of the i flow suggests that the i cone is polycyclic and different flow units were probably unintentionally sampled in the field the revised varnish ages of 30 and 39 ka for the i flow thus may be in good agreement with their corresponding 3 he and 36 cl ages in a blind test of the method varnishes from the phase 1 flow at pisgah an unnamed flow called here the ivflow at cima and the amboy flow were estimated to be 24 30 46 60 and 74 85 ka respectively these ages agree well with 36 cl ages of 22 5f1 3 46f2 and 79f5 ka reported for the same flows by phillips geomorphology 2002 these test results provide convincing evidence that varnish microstratigraphy once radiometrically calibrated can be used as a valid dating tool to estimate surface exposure ages of desert landforms in the western us drylands d 2002 elsevier science b v all rights reserved

history of modern earthquake hazard mapping and assessment in california using a deterministic or scenario approach modern earthquake ground motion hazard mapping in california began following the 1971 san fernando earthquake in the los angeles metropolitan area of southern california earthquake hazard assessment followed a traditional approach later called deterministic seismic hazard analysis dsha in order to distinguish it from the newer probabilistic seismic hazard analysis psha in dsha seismic hazard in the event of the maximum credible earthquake mce magnitude from each of the known seismogenic faults within and near the state are assessed the likely occurrence of the mce has been assumed qualitatively by using late quaternary and younger faults that are presumed to be seismogenic but not when or within what time intervals mce may occur mce is the largest or upper bound potential earthquake in moment magnitude and it supersedes and automatically considers all other possible earthquakes on that fault that moment magnitude is used for estimating ground motions by applying it to empirical attenuation relationships and for calculating ground motions as in neo dsha zuccoloet al 2008 the first deterministic california earthquake hazard map was published in 1974 by the california division of mines and geology cdmg which has been called the california geological survey cgs since 2002 using the best available fault information and ground motion attenuation relationships at that time the california department of transportation caltrans later assumed responsibility for printing the refined and updated peak acceleration contour maps which were heavily utilized by geologists seismologists and engineers for many years some engineers involved in the siting process of large important projects for example dams and nuclear power plants continued to challenge the map s the second edition map was completed in 1985 incorporating more faults improving mce s estimation method and using new ground motion attenuation relationships from the latest published results at that time cdmg eventually published the second edition map in 1992 following the governor s board of inquiry on the 1989 loma prieta earthquake and at the demand of caltrans the third edition map was published by caltrans in 1996 utilizing gis technology to manage data that includes a simplified three dimension geometry of faults and to facilitate efficient corrections and revisions of data and the map the spatial relationship of fault hazards with highways bridges or any other attribute can be efficiently managed and analyzed now in gis at caltrans there has been great confidence in using dsha in bridge engineering and other applications in california and it can be confidently applied in any other earthquake prone region earthquake hazards defined by dsha are 1 transparent and stable with robust mce moment magnitudes 2 flexible in their application to design considerations 3 can easily incorporate advances in ground motion simulations and 4 economical dsha and neo dsha have the same approach and applicability the accuracy of dsha has proven to be quite reasonable for practical applications within engineering design and always done with professional judgment in the final analysis dsha is a reality check for public safety and psha results although psha has been acclaimed as a better approach for seismic hazard assessment it is dsha not psha that has actually been used in seismic hazard assessment for building and bridge engineering particularly in california

effects of mountain uplift on east asian summer climate investigated by a coupled atmosphere ocean gcm abstract to study the effects of progressive mountain uplift on east asian summer climate a series of coupled general circulation model cgcm experiments were performed eight different mountain heights were used 0 no mountain 20 40 60 80 100 control run 120 and 140 the land sea distribution is the same for all experiments and mountain heights are varied uniformly over the entire globe systematic changes in precipitation pattern and circulation fields as well as sea surface temperature sst appeared with progressive mountain uplift in summertime precipitation area moves inland on the asian continent with mountain uplift while the pacific subtropical anticyclone and associated trade winds become stronger the mountain uplift resulted in an sst increase over the western tropical pacific and the maritime continent and an sst decrease over the western indian ocean and the central subtropical pacific there is a drastic change in the east asian circulations with the threshold value

strike slip fault geometry in turkey and its influence on earthquake activity the geometry of turkish strike slip faults has been reviewed and described from this data set it appears that fault geometry the distribution of discontinuities such as bends and stepovers along the main fault trace plays an important role in controlling the location of large earthquake rupture segments along the fault zones large earthquake ruptures generally do not propagate past individual stepovers that are wider than 5 km or bends that have angles greater than about 30 more important than the size of each discontinuity however is the total geometric pattern i e the distribution of adjacent bends and stepovers based not only on distance from one another but also on relative discontinuity size certain geometric patterns restraining single or double bends are particularly common and can be viewed as responsible for strain accumulation along portions of the fault zone fault geometry not only plays a role in the extent of earthquake rupture but also in characteristics of earthquake behavior for example large earthquake epicenters often occur near restraining bends or double bends furthermore aftershocks and swarm activity can often be associated with releasing areas areas along the strike slip fault that are undergoing a relatively large amount of extension

band of precariously balanced rocks between the elsinore and san jacinto california fault zones constraints on ground motion for large earthquakes a spectacular band of precariously and semiprecariously bal anced rocks extends from riverside to near borrego valley cali fornia about halfway between the elsinore and san jacinto fault zones the rocks are distributed in a band a few kilometers wide midway between the san jacinto and elsinore fault zones an in dication that the distribution is caused by attenuation of strong ground motion from numerous large events along these two fault zones these rocks have apparently been in place for thousands of years and thus place important constraints on ground motions from earthquakes on the basis of field tests and photographic analysis the estimated quasi static toppling accelerations for the precariously balanced rocks are 0 32 6 0 10 g g 5 gravitational acceleration the dynamic toppling accelerations are within this range for earthquakes with waveforms similar to those recorded during the izmit and denali earthquakes these constraints are roughly consistent with the median predicted value of ground mo tion for m7 earthquakes but somewhat lower than 11s ground motion curves and much lower than the values from the 2 in 50 yr hazard maps the evidence from these rocks has importance for some of the assumptions that go into calculating probabilistic seismic hazard assessment including median and standard devia tion of ground motion attenuation curves especially for hard rock for which few instrumental data are available the possible exis tence of random background earthquakes and the smoothing dis tance for historical seismicity

fractal analysis applied to characteristic segments of the san andreas fault fractal theory is applied in a quantitative analysis of the san andreas fault saf geometry the method which directly measures the increase in total fault length with a decrease in ruler size gives the fractal dimension d and scaling properties for the chosen length band 0 5 1000 km a physical interpretation of d is that it measures the irregularity of the fault trace in the selected band the fault is subdivided into six segments of distinctive seismic behavior a main fault trace which shows either maximum coseismic slip or creeping was selected for analysis with three alternative branches examined for the saf system south of san bernardino branches of the fault trace are not considered in this work fractal dimensions calculated for the different segments range from 1 0008 to 1 0191 and are different from 1 0 to the 95 confidence interval these small changes reflect the overall smoothness of the main fault trace significant variations in d among segments indicate heterogeneities in the fault smoothness along strike d also changes significantly from the short length band to the long length band where the demarcation point ranges from 1 to 2 km the short length band has larger d values a slight correlation is obtained between the fractal dimension of the main trace and the extent of subparallel faulting this indicates some correspondence between the main fault trace irregularity and the complexity of subsidiary fault traces in plan view

toppling analysis of the echo cliffs precariously balanced rock toppling analysis of a precariously balanced rock pbr can provide insight into the nature of ground motion that has not occurred at that location in the past and by extension can constrain peak ground motions for use in engineering design earlier approaches have targeted 2d models of the rock or modeled the rock pedestal contact using spring damper assemblies that require recalibration for each rock here a method to model pbrs in 3d is presented through a case study of the echo cliffs pbr the 3d model is created from a point cloud of the rock the pedestal and their interface obtained using terrestrial laser scanning the dynamic response of the model under earthquake excitation is simulated using a rigid body dynamics algorithm the veracity of this approach is demonstrated through comparisons against data from shake table experiments fragility maps for toppling probability of the echo cliffs pbr as a function of various ground motion parameters rock pedestal interface friction coefficient and excitation direction are presented these fragility maps indicate that the toppling probability of this rock is low less than 0 2 for peak ground acceleration pga and peak ground velocity pgv lower than 3 m s 2 and 0 75 m s respectively suggesting that the ground motion intensities at this location from earthquakes on nearby faults have most probably not exceeded the above mentioned pga and pgv during the age of the pbr additionally the fragility maps generated from this methodology can also be directly coupled with existing probabilistic frameworks to obtain direct constraints on unexceeded ground motion at a pbr s location

warm events in the tropical atlantic abstract sea surface temperature in the eastern equatorial atlantic ocean undergoes anomalous warming events of 1 2 c every few years the warm anomalies reach their maximum strength in northern hemisphere summer when equatorial upwelling normally brings cold thermocline water to the surface by compositing surface observations from a 28 year record we are able to identify consistent features in anomalies of sst and winds the composites show that the sst anomalies in northern summer are confined to the eastern equatorial region with reduced zonal winds to the west and reduced northward trade winds to the east accompanying these changes in winds are enhanced convection near the equator caused by a southward shift and intensification of the intertropical convergence zone later in the year sst south of the equator becomes elevated as a result by spring of the year following the equatorial anomaly convection in the western side of the basin is much higher than normal to understand the ocean dynami