the earthquake prediction experiment at parkfield california since 1985 a focused earthquake prediction experiment has been in progress along the san andreas fault near the town of parkfield in central california parkfield has experienced six moderate earthquakes since 1857 at average intervals of 22 years the most recent a magnitude 6 event in 1966 the probability of another moderate earthquake soon appears high but studies assigning it a 95 chance of occurring before 1993 now appear to have been over simplified the identification of a parkfield fault segment was initially based on geometric features in the surface trace of the san andreas fault but more recent microearthquake studies have demonstrated that those features do not extend to seismogenic depths on the other hand geodetic measurements are consistent with the existence of a locked patch on the fault beneath parkfield that has presently accumulated a slip deficit equal to the slip in the 1966 earthquake a magnitude 4 7 earthquake in october 1992 brought the parkfield experiment to its highest level of alert with a 72 hour public warning that there was a 37 chance of a magnitude 6 event however this warning proved to be a false alarm most data collected at parkfield indicate that strain is accumulating at a constant rate on this part of the san andreas fault but some interesting departures from this behavior have been recorded here we outline the scientific arguments bearing on when the next parkfield earthquake is likely to occur and summarize geophysical observations to date

indosinian dextral ductile fault system and synkinematic plutonism in the southwest of the ogcheon belt south korea reply abstract the structure of the mylonite belt in the southwestern part of the ogcheon belt has been investigated and interpreted in the light of recent radiometric data the shear belt is composed of several en echelon dextral shear zones relayed by compressional or extensional tectonic bridges the dextral displacement along the fault system which may be extended to the hida zone of japan is of the order of 200 km it has brought into contact the ryeongnam block and its cambrian middle ordovician cover of north china affinity with the southwestern margin of the ogcheon belt characterized by cambrian middle silurian rift facies and shelf deposits of south china affinity synkinematic plutons are emplaced within the shear belt which is postdated by uppermost triassic unfoliated granitoids at the surface the shear belt generated elongated intermontane coal basins initiated as transtensional half grabens because of its post permian pre early jurassic age and its dextral kinematics we correlate the shear belt with the late stages of the akyioshi indosinian collisional orogeny of the east asian margin the synkinematic plutonism that accompanied the shear zone may be due to post collisional crustal stretching and subsequent anatexis at the mantle crust interface

pollen and non pollen palynomorph analyses of upper holocene sediments from dianshan yangtze coastal lowlands china hydrology vegetation history and human activity abstract the coastal deltaic plain of the yangtze river between taihu lake tai and shanghai in eastern china has been the scene of human settlement and agriculture since the early neolithic becoming increasingly intensive in the upper holocene when delta accretion and the establishment of a stable hydrological regime of freshwater lakes and wetlands allowed the development of extensive agriculture and complex society in late prehistoric and dynastic times during this period the area was significantly affected by changes in sea level climate and vegetation resulting in a dynamic and complex environmental history however little research has concentrated on environmental change and human impacts during the last few millennia this study focuses on this late period presenting the results of integrated sedimentary microfossil and radiocarbon analyses from a core near the eastern margin of lake dianshan to the east of taihu after the withdrawal of intertidal conditions and the conversion to freshwater lake at the core site about 2600 cal yr bp pollen and algal spore data show that increased sedimentation gradually reduced freshwater depth until a surface peat formed ca 1500 cal yr bp this also dates the start of a switch in woodlands from sub tropical and warm temperate trees to a mainly cool temperate and coniferous tree flora under climatic cooling and human impact after this time water depths at the site increased greatly partly due to climate change and flooding but also because of the establishment of deepwater paddy agriculture microcharcoal and pollen data show that a major episode of human impact using fire with deforestation and rice cultivation occurred between ca 1500 and 1200 cal yr bp these dates suggest it is one of the latest examples of flooded field paddy cultivation before more intensive agricultural techniques were adopted in the area after ca 800 cal yr bp

changes in fire regimes on the chinese loess plateau since the last glacial maximum and implications for linkages to paleoclimate and past human activity abstract a high resolution black carbon bc record from 27 5 kyr bp to present was reconstructed using a chemical oxidation method on loess and paleosol samples from the lijiayuan section of the chinese loess plateau the black carbon mass sedimentation rates bcmsr and carbon isotopic record reveal a paleofire history and its relationship with climate and vegetation changes at the study site the bcmsr record was decomposed into two components background bcmsr and the bcmsr peaks the background bcmsr represents regional fires and shows high fire activities occurred contemporaneous with the younger dryas older dryas heinrich events and greenland stadials as registered in the loess grain size record this suggests a rapid response of regional fires on the loess plateau to abrupt climate changes spectral analysis of background bcmsr showed two meaningful periodicities of 1620 and 1040 years close to the cyclicity of the east asian monsoon as recorded in the stalagmite 18o record in central china this indicates a tight control of millennial scale wet dry changes in the monsoonal climate on regional fires on the loess plateau by contrast the bcmsr peaks are considered to reflect local fire episodes the occurrences of local fires were more frequent during the last glacial period with a maximum frequency of 6 episodes 1000 years during the last glacial maximum lgm 22 3 to 14 6 kyr bp when the climate was drier and more continuous grassy fuels existed on the landscape during the last glacial interglacial transition lgit period 14 6 to 11 0 kyr bp fire frequency was largely reduced due to an increase in precipitation and more woody vegetation if the lgit period is taken as an analog for the projected near future then future global warming alone may not produce large wildfires in northwestern china wildfires remained infrequent during the early to middle holocene biomass burning increased after 4 0 kyr bp when the climate became drier and land use was more intensive bc carbon isotope ratios may well reflect changes in the vegetation being burnt i e grasses versus trees yielding results consistent with the associated pollen data in the region

detection of a locked zone at depth on the parkfield california segment of the san andreas fault the parkfield california segment of the san andreas fault is transitional in character between the creeping segment of the fault to the northwest and the locked carrizo plain segment to the southeast the rate of shallow fault slip decreases from 25 30 mm yr northwest of the epicenter of the 1966 parkfield earthquake to zero at the southeastern end of the 1966 rupture zone data from a network of trilateration lines spanning the san andreas fault near parkfield and extending to the pacific coast near san luis obispo shed light on the rate of fault slip at depth since the 1966 earthquake in this study average rates of line length change and shallow fault slip were inverted to determine the slip rate at depth on the parkfield fault segment the fault is taken to be a vertical surface with unknown distribution of strike slip displacement in an elastic half space a striking result of the inversions is that all solutions providing acceptable fits to the data exhibit a locked zone essentially coincident with the rupture surface of the 1966 parkfield earthquake the data require that the locked zone extend nearly as far north as the 1966 epicenter however the vertical extent of the locked zone is not well resolved over much of the parkfield segment the fault is slipping faster at the earth s surface than it is at seismogenic depths in order to fit the trilateration measurements it is necessary to include a component of contraction normal to the trend of the san andreas the inversion results suggest a spatially uniform normal strain of 0 06 strain yr the orientation of the contraction is compatible with geologic and seismic evidence of active folding and reverse faulting in the region the magnitude of the contraction is consistent with convergence rates inferred from global plate motion models

rare earth elements geochemistry in surface floodplain sediments from the xiangjiang river middle reach of changjiang river china abstract the xiangjiang river is one of the most important tributaries of the changjiang river in southern china in this study floodplain sediments from the xiangjiang river have been analyzed for sediment grain size and trace and rare earth elements rees the results have been used to characterize the sediments ree composition and distribution and to identify the sediment sources and the effects of industrial pollution the total ree ree concentrations of the river sediments show wide variations ranging from 37 5 to 237 4 g g 1 with an average of 145 6 g g 1 the chondrite normalized ree patterns can be differentiated into two groups whereas the average upper continental crust ucc normalized ree pattern can be classified four groups ree shows strong positive correlations with clay r 0 91 and r 0 89 and strong negative correlations with sand r 0 91 implying that the grain size is an important factor in controlling the ree abundance because rees are preferentially enriched in clay minerals in fine sediments and diluted by quartz and carbonate minerals in coarse sediments ree yields strong positive correlations with mn r 0 78 and fe r 0 97 suggesting that the ree composition of xiangjiang river sediments is controlled by clay mineral compositions the reason is that fe and mn oxyhydroxides accumulate in fine grained sediments and control the ree abundance two stations xj08 and xj14 show different ucc and chondrite normalized ree distribution patterns with relative light rare earth element lree depletion and heavy rare earth element hree enrichment compared with other stations suggesting they have been polluted by industrial effluents therefore rees can be effectively used to trace sediment provenance and pollution sources

seismic moments local magnitudes and coda duration magnitudes for earthquakes in central california onscale seismograms recorded at stations in the u s geological survey s usgs central california seismic network calnet have been used to estimate the seismic moment m and local magnitude ml for earthquakes of 1 ml 4 located on the san juan bautista and parkfield sections of the san andreas fault the coyote lake section of the calaveras fault the sargent fault and near livermore these data together with m and ml estimates for 4 ml 6 earthquakes in these areas cannot be fit with a single linear log m versus ml relation rather the data are consistent with log m 1 5 ml 16 for 3 ml 6 with log m 1 2 ml 17 for 1 1 2 ml 3 1 2 and with a slope of to 1 fro 1 2 ml 1 1 2 whereas usgs coda duration magnitude md is consistent with ml for 1 1 2 ml 3 md is larger than ml at ml 1 1 2 and smaller than ml at ml 3 log m can be estimated to a precision of 0 2 for 1 md 3 1 2 earthquakes in central california by applying log m 1 2 md 17 to the md that have been routinely published by the usgs

slip budget and potential for a m7 earthquake in central california the slip rate budget of the san andreas fault saf in central california which is approximately 33 mm yr is accounted for by a change in the slip release mechanism along the fault in the nw section of the fault between bear valley and monarch peak creep apparently accounts for the slip budget with the seismicity contributing negligibly the section at parkfield marks the transition from a creeping to a locked fault trace since the m8 1857 earthquake five m6 earthquakes have occurred but have not completely accounted for the slip budget southeast of parkfield the saf has been locked since 1857 from cholame to bitterwater valley this section now lags the deep slip by the amount of slip released in 1857 consequently faulting in this section could occur at the time of the next parkfield earthquake if this earthquake releases the slip deficit accumulated in the transition zone and in the locked zone the earthquake will have a moment magnitude m7 2

fault model for preseismic deformation at parkfield california we construct an earthquake instability model to estimate precursory faulting and ground deformation before the next moderate m 5 5 6 earthquake on the san andreas fault near parkfield california the quasi static model simulates fault slip fault shear stress and ground deformation for all stages of repeated earthquake cycles unstable slip which is the analog of a moderate parkfield mainshock is caused by overall failure of a postulated strong area or patch of the fault zone the brittle patch and surrounding weaker viscous fault are defined by the sign of a spatially varying coefficient of a slip rate dependent fault law stable failure of the patch leading up to mainshock failure causes slip rate to increase at depth amplitudes and timescales of the resulting preseismic deformation anomalies are found for the current earthquake cycle at parkfield starting just after the 1966 mainshock in two ways in the first way we vary parameter values in a sequence of simulations so as to find the simulation giving best agreement with locations moments and recurrence times of past moderate earthquakes and also with fault creep and trilateration line length changes since the 1966 mainshock in the second way we assign values of most parameters from laboratory friction experiments and a temperature depth profile inferred from heat flow data overall agreement between model results and observations is comparable for the two methods in all simulations preseismic deformation anomalies arise from slip rate increase near the model earthquake focus and start several years or less before instability preseismic anomalies in surface fault creep and line length are always too small to detect in current measurements however for some simulations constrained mainly by field data the predicted anomalies in borehole dilatation are large enough to detect

black carbon and charcoal records of fire and human land use over the past 1300 years at the tongguan kiln archaeological site china abstract to examine fire patterns and landscape evolution in the xiangjiang river basin over the past 1300 years high resolution charcoal and black carbon bc char and soot records from the tongguan kiln archaeological site of historical ceramic production have been analyzed in combination with robust optically stimulated luminescence osl and accelerator mass spectrometry radiocarbon ams14c dating archaeological documents and paleo environmental proxies i e magnetic susceptibility total organic carbon xrf derived elemental data etc throughout history charcoal and bc have recorded changes in regional land use at the tongguan kiln site peaks in char and macro charcoal contents indicate that local smoldering fire occurrences were typical with large amount of fuel used for kilns between 1300 and 1100 years b p under wet climate conditions these peaks coincided with the size of the tongguan kiln archaeological site which led to reduction of forest cover from nearby mountains and activated soil erosion subsequently the frequency of fire activity declined to a very low level between 1100 and 600 years b p coupling with the decline of the tongguan kiln and with a warm period in the study region over the past 600 years with sharp growth in population regional fires increased to an unprecedented scale for land reclamation for dry crop cultivation during a cold period which in turn resulted in further environmental deterioration in summary shifts of fire patterns in the study site over the past 1300 years have been closely related to 1 climate variation 2 the mode of human land use and 3 vegetation type and fuel combustion efficiency there was an interactive complex relationship between these factors in the xiangjiang river basin and these results suggest that the intensity and pattern of human land use could have further impacts on fire patterns and landscape evolution in response to climatic change of the east asian monsoon in the past as well as in the future

the determination of displacement fields from geodetic data along a strike slip fault observations of angles or distances between stations of a geodetic network are commonly used to infer information about the movement of the surface of the earth the absence of any observations external to the network leads to an ambiguous displacement field existing techniques for eliminating this ambiguity are all unsatisfactory in some respect the best technique an inner coordinate solution is not appropriate for networks located in a strike slip fault environment the inner coordinate solution zeros the rotation of all stations about their center of mass along a strike slip fault like the san andreas however motion normal to the fault is less likely than motion parallel to the fault the solution presented here an outer coordinate solution finds the rotation of the network that minimizes the components of displacement normal to the fault since motion along a strike slip fault is generally expected to be parallel to the fault the displacements obtained with the outer coordinate solution are more reasonable than those obtained with other techniques examination of a trilateration network near san francisco bay demonstrates the large effect that the choice of adjustment technique can have on the inferred relative motion of the two sides of the fault the inner coordinate solution gave a rate of about 1 mm yr whereas the preferred outer coordinate solution rate was 36 mm yr

hydroclimatic changes in china and surroundings during the medieval climate anomaly and little ice age spatial patterns and possible mechanisms abstract investigating hydroclimatic changes during key periods such as the medieval climate anomaly mca 1000 1300 ad and the little ice age lia 1400 1900 ad is of fundamental importance for quantifying the responses of precipitation to greenhouse gas induced warming on regional and global scales this study synthesizes the most up to date and comprehensive proxy moisture precipitation records during the past 1000 years in china and surroundings the proxy data collected include 34 records from arid central asia aca and 37 records from monsoonal asia our results demonstrate a pattern of generally coherent regional moisture variations during the mca and lia in mid latitude asia north of 30 n monsoonal northern china north china and northeast china was generally wetter while aca northwest china and central asia was generally drier during the mca than in the lia a west east mode the boundary between wetter northern china and drier aca was roughly consistent with the modern summer monsoon boundary in monsoonal china to the east of 105 e the northern part was generally wetter while the southern part was generally drier during the mca than in the lia a north south mode with a boundary roughly along the huai river at about 34 n these spatial patterns of moisture precipitation variations are also identified by instrumental data during the past 50 years in order to understand the possible mechanisms related to the moisture variations during the mca and lia we investigate the major sst and atmospheric modes e g the el nino southern oscillation enso the atlantic multidecadal oscillation amo and the north atlantic oscillation nao which affect the moisture precipitation variations in the study region using both the instrumental data and the reconstructed time series it is found that the enso may play an important role in determining hydroclimatic variability over china and surroundings on a multi centennial time scale and that the foregoing spatial patterns could be attributed to the la nina like el nino like condition during the mca lia in addition amo and nao may also have their own contributions

late palaeozoic to early mesozoic geodynamic evolution of the circum pacific orogenic belt in south korea and southwest japan abstract a review of the overall features of the late palaeozoic early mesozoic orogen of southwest japan and its korean hinterland allows a new geodynamic model for the building of the east asian margin to be proposed during middle carboniferous to early permian times an oceanic basin formed in a passive margin environment at a moderate spreading rate as the honshu continental block drifted away from the sino korean continent during that period paralic platform conditions and extensional synsedimentary tectonics prevailed in korea in middle permian times the closure of the oceanic area was responsible for yakuno ophiolite obduction and high pressure metamorphism while highly subsiding coal basins developed in the emerged korean hinterland thereafter in late permian times when the honshu block collided with the asian margin akiyoshi orogeny locally derived terrestrial clastic sedimentation in korea has succeeded coal measure deposition with local unconformity in early triassic times the collision was completed and regional uplift of the thickened crust resulted in the deposition of thick distal siliciclastic rocks in rapidly subsiding hinterland troughs korea and flyschoid deposition in the tamba foreland basin outer zone of southwest japan middle to late triassic medium to low pressure metamorphism large scale transcurrent tectonics and associated calc alkaline synkinematic plutonism in the hida and ogcheon belts represent a post collisional feature of the akiyoshi orogenic event post tectonic intrusives and terrestrial deposits post date intracratonic tectonics at ca 200 ma thus the akiyoshi orogeny of southwest japan is a result of continental drift and ensuing collisional rewelding of a fragment of sino korea the honshu microcontinent

relationship between shear zones and sr isotope compositions of granitic rocks in the hida belt japan the dextral shear zones in the hida belt central japan show close temporal and spatial relationships with some of the late triassic to early jurassic funatsu granitic intrusions the sr isotopic compositions of intrusions associated with the shear zones suggest large crustal contributions to the magma chemistries in contrast granitic intrusions not accompanied by shear zones show less crustal signatures various models could possibly explain the genetic relationship between shear zones and granitic magmas with crustal isotope characteristics though it is not clear which model is most applicable it is suggested that contrasting characteristics in the two types of intrusions reflect different stress conditions the granitic rocks without large crustal contributions are likely to be the products of extensional stress conditions those with a larger amount of crustal contamination seem to be generated in compressional stress situations that accompanied the development of ductile shear zones along the co

crustal development of the hida belt japan evidence from nd sr isotopic and chemical characteristics of igneous and metamorphic rocks abstract chemical and sr nd isotopic investigations were performed on the igneous and metamorphic rocks in the hida belt central japan to clarify their ages and possible sources and to provide constraints on the crustal evolution of the eastern margin of the asian continent igneous rocks of three main stages in the hida belt represented by the late silurian amphibolites first stage the middle carboniferous mafic dikes second stage and the late triassic to early jurassic granite gabbro plutons third stage show alkaline to calc alkaline chemical affinity major and trace element characteristics show that the three stages of igneous rocks were emplaced in a continental margin or continental arc environment the mafic igneous rock suites have relatively high e nd 0 5 to 5 5 and low 87 sr 86 sr 0 7049 to 0 7061 values indicating their origin from upper mantle sources though the third stage granitoids contain recycled crustal components the hida gneisses of clastic origin show two groups of model ages t dm middle proterozoic 1 4 2 2 ga and late proterozoic to early paleozoic 0 55 0 74 ga consistent with geological geochemical and radiometric age data are that the sedimentation and basaltic volcanism occurred in early to middle paleozoic and the protoliths with middle proterozoic model ages are detritals from the proterozoic continental provenances a synthesis of available geological and geochemical data for the basement metamorphic and igneous rocks in eastern asia suggests two possibilities for the paleozoic to early mesozoic history of the hida belt 1 the hida belt was formed at the eastern margin of the north china block with later evolution as a suture zone between the north and south china blocks or 2 it evolved as a part of the east central asian orogenic belt ecaob to the north

recurrence models and parkfield california earthquakes main shocks of the earthquake sequences that occurred on the parkfield section of the san andreas fault in central california in 1922 1934 and 1966 are characterized by southeast rupture expansion over the same 20 to 30 km long section of the fault whereas the seismic moments for the 1922 and 1934 events are identical to within a precision of 10 the seismic moment for 1966 is 20 greater than for the earlier events to within a precision of 20 the parkfield area seismicity in general seems well described by a recurring moderate size characteristic earthquake repeating the same epicenter magnitude seismic moment rupture area and southeast direction of rupture expansion an unexplained 10 year advance of the 1934 event is the only discrepancy in the hypothesis that the parkfield earthquakes in 1857 1881 1901 1922 1934 and 1966 represent a strictly periodic process assuming the strictly periodic model and the absence since 1966 of the perturbations hypothesized for the 1922 to 1934 period the next characteristic parkfield earthquake should occur between 1983 and 1993

recent plate motions and crustal deformation reports by u s workers on geodetic measurements of recent plate motions or crustal deformation published in 1987 1990 are reviewed the review begins with global plate motions proceeds through plate boundaries in california alaska and the pacific northwest and finishes with volcanic phenomena monument stability and longevity and gps relative position measurements 184 refs

introduction to the special issue on the 2004 parkfield earthquake and the parkfield earthquake prediction experiment the 28 september 2004 m 6 0 parkfield earthquake a long anticipated event on the san andreas fault is the world s best recorded earthquake to date with state of the art data obtained from geologic geodetic seismic magnetic and electrical field networks this has allowed the preearthquake and postearthquake states of the san andreas fault in this region to be analyzed in detail analyses of these data provide views into the san andreas fault that show a complex geologic history fault geometry rheology and response of the nearby region to the earthquake induced ground movement although aspects of san andreas fault zone behavior in the parkfield region can be modeled simply over geological time frames the parkfield earthquake prediction experiment and the 2004 parkfield earthquake indicate that predicting the fine details of future earthquakes is still a challenge instead of a deterministic approach forecasting future damaging behavior such as that caused by strong ground motions will likely continue to require probabilistic methods however the parkfield earthquake prediction experiment and the 2004 parkfield earthquake have provided ample data to understand most of what did occur in 2004 culminating in significant scientific advances

source parameters of the 1980 mammoth lakes california earthquake sequence from the more than 1500 mammoth lakes earthquakes recorded on three component digital seismographs spudich et al 1981 150 were used in an analysis of the locations mechanism and source parameters a composite fault plane solution of nine earthquakes 3 9 m 5 1 defines a right lateral strike slip mechanism on a steeply dipping nearly east west plane striking s75 e or left lateral strike slip on a nearly north south plane striking n10 e vertical cross sections of well located aftershocks indicate possibly three east west planes that coincide with the locations of the four largest earthquakes with ml 6 0 using the spectral analysis of s waves brune 1970 source parameters for 67 earthquakes were determined forty eight had magnitudes greater than or equal to 3 0 seismic moments ranged from 9 20 1018 dyn cm to 2 33 1024 dyn cm earthquakes with seismic moment greater than about 1 0 1021 dyn cm had nearly constant stress drops 50 bars earthquakes with seismic moment less than about 1 0 1021 dyn cm had stress drops that apparently decrease as seismic moment decreases

in the shadow of 1857 the effect of the great ft tejon earthquake on subsequent earthquakes in southern california the great 1857 fort tejon earthquake is the largest earthquake to have hit southern california during the historic period we investigated if seismicity patterns following 1857 could be due to static stress changes generated by the 1857 earthquake when post 1857 earthquakes with unknown focal mechanisms were assigned strike slip mechanisms with strike and rake determined by the nearest active fault 13 of the 13 southern california m 5 5 earthquakes between 1857 and 1907 were encouraged by the 1857 rupture when post 1857 earthquakes in the transverse ranges with unknown focal mechanisms were assigned reverse mechanisms and all other events were assumed strike slip 11 of the 13 earthquakes were encouraged by the 1857 earthquake these results show significant correlations between static stress changes and seismicity patterns the correlation disappears around 1907 suggesting that tectonic loading began to overwhelm the effect of the 1857 earthquake early in the 20th century

recent rupture history of the san andreas fault southeast of cholame in the northern carrizo plain california we conducted a paleoseismic study on the san andreas fault saf southeast of cholame california to investigate the record of earthquakes along an 80 km paleoseismic data gap between parkfield and the carrizo plain at the ly4 site located 37 5 km southeast of highway 46 along the saf we excavated a fault perpendicular trench on the distal end of an alluvial fan that emanates from the temblor mountains to the northeast we found evidence of three and possibly four ruptures recorded within the stratigraphy the only age constraints are radiocarbon dates on a paleosol three units 50 cm below the oldest event horizon and the presence of recently introduced exotic pollen species in an upper unit the radiocarbon dates indicate there have been at least three surface rupturing events at the ly4 site since cal a d 1058 1291 exotic historic pollen in the top of a unit possibly cut by the youngest event suggests that an earthquake affected at the ly4 site close to a d 1873 1874 manuscript received 11 january 2000

the 2004 parkfield earthquake the 1985 prediction and characteristic earthquakes lessons for the future the 1985 prediction of a characteristic magnitude 6 parkfield earth quake was unsuccessful since no significant event occurred in the 95 time window 1985 1993 anywhere near parkfield the magnitude 6 earthquake near parkfield in 2004 failed to satisfy the prediction not just because it was late it also differed in character from the 1985 prediction and was expectable according to a simple null hypothesis furthermore the prediction was too vague in several important respects to meet the accepted definition of an earthquake prediction an event occurring by chance and meeting the general description of the predicted one was reasonably probable the original characteristic earthquake model has failed in comprehensive tests yet it is still widely used modified versions employed in recent official seismic hazard calculations allow for interactions between segments and uncertainties in the parameters with more adjustable parameters the modified versions are harder to falsify the characteristic model as applied at parkfield and elsewhere rests largely on selected data that may be biased because they were taken out of context we discuss implications of the 2004 event for earthquake prediction the characteristic earthquake hypothesis and earthquake occurrence in general

a paleoindian response to younger dryas climate change abstract late quaternary changes in north american vegetation and geography reflect the influence of changing climate induced by the retreating ice sheets orbitally driven seasonal insolation patterns increasing carbon dioxide concentrations and relatively rapid internal variations at regional scales these climate changes resulted in ecosystem variability that impacted human access to resources we use paleoenvironmental and archaeological records from 14 000 to 10 000 cal yr bp for new england and maritime canada ne m to propose the impact of rapid climate change on human resource procurement and technology paleoenvironmental reconstructions for the younger dryas chronozone ydc 12 900 11 600 cal yr bp show ecologic responses to colder than earlier conditions at roughly the same time 13 000 11 000 cal yr bp we surmise that fluted points were used to hunt large mammals including caribou which inhabited regions with sub arctic like vegetation environmental changes associated with rapid regional warming at the end of the ydc coincided with the abandonment of fluting technology as conditions warmed vegetation changes led to shifts in animal populations which may be reflected in the development of other point styles by paleoindians and subsequent human groups

charcoal records of fire history in the holocene loess soil sequences over the southern loess plateau of china abstract charcoal preserved in accretionary loess soil profiles within the southern part of the loess plateau has recorded fire history and landscape evolution connected with climatic variations and human activities local wildfires occurred frequently during the late last glacial period and the early holocene before 8500 years bp when steppe vegetation expanded from the inner mongolian plateau southerly over the loess plateau during the holocene climatic optimum between 8500 years bp and 3100 years bp natural wildfires were largely reduced pedogenesis of the luvisols and isohumisols was intensified because of the increased monsoonal precipitation and soil moisture localized fires in connection with human activities occurred in different patterns at the study sites fire seems to have been applied to vegetation clearance for land reclamation for millet cultivation at many places during the neolithic and early bronze age levels of biomass burning were very high during the late holocene when the climate became drier and historical land use became more intensive at some sites the intensity of human disturbance by fire and cultivation increased continuously during the last 3100 years at the other sites local fires occurred most frequently between 3100 years bp and 1500 years bp during the major period of land reclamation for cereal cultivation human burning of the landscape has been reduced since then

geodetic measurements near parkfield california 1959 1984 trilateration measurements have been made by various agencies since 1959 near parkfield california in the transition zone between the central creeping section and the southern locked section of the san andreas fault within the transition zone there are several creep meters and alignment arrays four small aperture trilateration networks and a broad trilateration network extending 70 km southwest from the san andreas fault to the pacific coast line length changes observed after the 1966 ml 5 6 parkfield earthquake indicate a geodetic moment of 4 5 1 0 1025 dyn cm the data are consistent with either 91 8 cm slip on a rupture zone which is 30 km long and extends from 3 to 8 km below the surface or 59 5 cm on a 30 km long zone 2 10 km deep this moment estimate includes some postseismic slip and is a factor of 2 4 greater than the moment determined from seismic surface waves the post 1966 data set is well suited to discriminate between the effects of surface and deep slip surface slip rates determined by creep meters alinement arrays and small aperture trilateration networks decrease from 29 mm yr at slack canyon to zero south of highway 46 a gradient of roughly 0 48 0 01 mm yr km deformation of a subset of the trilateration network between cholame and san luis obispo is consistent with shallow slip of 2 9 1 2 mm yr from the surface to a depth of 16 km and 33 4 5 5 mm yr below 16 km the trilateration data alone do not uniquely constrain both the transition depth from shallow to deep slip and the deep slip rate a transition depth near 16 km is preferred because it provides the best fit to the data and because the predicted slip rate is consistent with independent estimates of the total slip rate across the san andreas fault this simple two dimensional model neglects along strike variations in the deformation the data show no evidence for significant strike slip deformation across faults between the san andreas and the pacific coast

slip along the san andreas fault associated with the great 1857 earthquake historical records indicate that several meters of lateral slip along the san andreas fault accompanied the great 1857 earthquake in central and southern california these records together with dendrochronological evidence suggest that the rupture occurred along 360 to 400 km of the fault including several tens of kilometers of the currently creeping reach in central california geomorphic expressions of late holocene right lateral offsets are abundant along the 1857 rupture along 300 kilometers of the 1857 rupture between cholame and wrightwood the youngest discernible offset ranges from 3 to 9 1 2 meters dormancy of the fault since 1857 almost certainly indicates that this latest offset was created in 1857 fault slip apparently associated with the 1857 earthquake varies in a broadly systematic way along the trace of the fault it is relatively uniform along each of several long segments but changes rather abruptly in value between these segments this nonuniform displacement pattern may imply that some segments of the fault rupture more frequently or experience a slower long term slip rate than others the 1857 offsets indicate a seismic moment m o between 5 3 and 8 7 10 27 dyne cm assuming a 10 to 15 km depth of rupture and relatively uniform slip as a function of depth a comparison with the rupture length average slip value and tectonic setting of the california earthquake of 1906 m s 8 1 4 indicates a value of m 8 1 4 for the 1857 event

earthquake deformation cycle on the san andreas fault near parkfield california six moderate earthquakes are thought to have ruptured the parkfield segment of the san andreas fault since 1857 the similar characteristics of the three seismically recorded events together with the quasi regular 22 year recurrence interval have led to the forecast of a similar event in 1988 5 years in this study the potential for the hypothesized earthquake is assessed by estimating the time required for interseismic straining to recover the strain energy released by the most recent june 1966 parkfield earthquake for a simple model of the earthquake cycle this interval is proportional to the ratio of the 1966 seismic moment to the interseismic moment deficit rate baseline lengths measured before and after the 1966 earthquake are inverted to estimate the magnitude and distribution of the combined coseismic and transient postseismic slip although the geodetic data determine only broad spatial averages of the fault slip they do require that slip at depth exceeded the surface offsets measured in 1966 inversions with extreme prior models are calculated to assess the range of seismic moment and moment deficit rates consistent with the available geodetic data inversions assuming only that the slip distributions are to some degree smooth yield strain energy recovery intervals of 14 25 years extreme values range from as little as 6 years to as much as 29 years in comparison historic recurrence intervals of parkfield earthquakes range from 12 to 32 years these results are consistent with the expectation of a magnitude 5 6 earthquake near parkfield by 1993

wildfire history and climatic change in the semi arid loess tableland in the middle reaches of the yellow river of china during the holocene evidence from charcoal records high resolution macroscopic charcoal and sediment analysis was used to reconstruct fire history and environmental changes from three loess paleosol profiles on the semi arid loess tableland landsca

active tectonic studies in the united states 1987 1990 the techniques and instrumentation used in active tectonic studies are discussed and recent results are reviewed it is suggested that a critical mass of data on several particular regions has been accumulated making possible critical debates and attempts to assess earthquake hazards particular attention is given to studies of the pacific northwest region basin and range deformation studies and distributed deformation and hidden earthquake sources also included is a comprehensive bibliography for the period

fire history and human activity revealed through poly cyclic aromatic hydrocarbon pah records at archaeological sites in the middle reaches of the yellow river drainage basin china abstract disentangling the role of natural and anthropogenic factors is a major challenge in paleofire studies here we introduce the molecular biomarkers of polycyclic aromatic hydrocarbon pahs combined with charcoal and black carbon in sediments of archaeological sites to identify anthropogenic signals of environmental change during the middle holocene in the prehistoric period an intensified fire regime period inferred on the basis of pahs char and macro charcoal levels has been attributed to intensified anthropogenic biomass burning from dry crop cultivation between 6500 and 5000 and 3900 3600 yr bp corresponding to the earliest chinese settlements during the miaodigou banpo iv culture and the development of the erlitou culture under drier climate conditions subsequently the fire frequency decreased notably between 4500 and 4000 yr bp as the climate became wetter and there were shifts in the frequency of high magnitude floods corresponding to the abandonment of late neolithic settlements in the floodplain changes in the pah fluxes in sediments are positively correlated with intensified fire regime periods consistent with the charcoal and black carbon fluxes during those periods principal component analysis of pah fluxes suggests that these intensified fire events have a pyrogenic signature implying that the pahs were derived from biomass burning of fuelwood and other woody plants in this study pahs in loess sediments have been used as the indicators of anthropogenic biomass burning through time meanwhile pahs also record the shift of modes of production and the evolution of human settlements as well as the choices made in response to limited natural resources to comprehensively analyze the paleofire records of pahs charcoal and black carbon combined with multiproxy evidence are needed to understand wildfire history as well as human land use and social and cultural development across the study regions in depth

inferring segment strength contrasts and boundaries along low friction faults using surface offset data with an example from the cholame carrizo segment boundary along the san andreas fault southern california rupture segmentation arises from changes in fault geometry and strength we use boundary element models of frictionless strike slip fault segments to quantify how fault geometry and strength change earthquake surface offset distributions using these relationships between fault geometry strength and surface offsets we can infer fault strength from the surface offsets in cases where the fault geometry can be independently constrained this article includes normalized plots of the surface offset distribution expected from rupture along low friction fault segments with strength contrasts of 1 4 1 3 1 2 1 2 3 and 4 for a range of fault segment geometries these plots may be used with offset data to constrain the strength of two coplanar adjacent fault segments this analysis is applied to the cholame and carrizo segments of the san andreas fault the available surface offset data suggest that the offset increases where the fault deepens in addition the observed offset gradient at the segment boundary requires a 2 3 1 4 strength ratio of the cholame to the carrizo segment

seismomagnetic effects from the long awaited 28 september 2004 m 6 0 parkfield earthquake precise measurements of local magnetic fields have been obtained with a differentially connected array of seven synchronized proton magnetometers located along 60 km of the locked to creeping transition region of the san andreas fault at parkfield california since 1976 the m 6 0 parkfield earthquake on 28 september 2004 occurred within this array and generated coseismic magnetic field changes of between 0 2 and 0 5 nt at five sites in the network no preseismic magnetic field changes exceeding background noise levels are apparent in the magnetic data during the month week and days before the earthquake or expected in light of the absence of measurable precursive deformation seismicity or pore pressure changes obser vations of electric and magnetic fields from 0 01 to 20 hz are also made at one site near the end of the earthquake rupture and corrected for common mode signals from the ionosphere magnetosphere using a second site some 115 km to the northwest along the fault these magnetic data show no indications of unusual noise before the earthquake in the ulf band 0 01 20 hz as suggested may have preceded the 1989 ml 7 1 loma prieta earthquake nor do we see electric field changes similar to those suggested to occur before earthquakes of this magnitude from data in greece uni form and variable slip piezomagnetic models of the earthquake derived from strain displacement and seismic data generate magnetic field perturbations that are con sistent with those observed by the magnetometer array a higher rate of longer term magnetic field change consistent with increased loading in the region is apparent since 1993 this accompanied an increased rate of secular shear strain observed on a two color edm network and a small network of borehole tensor strainmeters and increased seismicity dominated by three m 4 5 5 earthquakes roughly a year apart in 1992 1993 and 1994 models incorporating all of these data indicate increased slip at depth in the region and this may have played a role in the final occurrence of the 28 september 2004 m 6 0 parkfield earthquake the absence of electric and magnetic field precursors for this and other earthquakes with m 5 7 3 elsewhere in the san andreas fault system indicates useful prediction of damaging earthquakes seems unlikely using these electromagnetic data

reassessment of a slip budget along the parkfield segment of the san andreas fault historically the parkfield segment has represented a transition in fault behavior along the san andreas fault saf despite a 33 mm yr long term slip rate along the saf slip has not been observed on the cholame segment since the great 1857 fort tejon earthquake during that time the parkfield segment has experienced slip from at least six m 6 0 earthquakes aseismic fault creep and from minor earthquakes data from aseismic slip rate studies and historical earthquake studies allow us to estimate the total slip released along this portion of the saf since 1857 assuming the saf should slip at the long term slip rate a slip deficit of 5 m exists along the cholame segment since 1857 the slip deficit is approximately equivalent to 1857 offsets measured on the cholame and the southeast portion of the parkfield segment thus the slip deficit in southeast parkfield and cholame may be as great as the slip accommodated along these segments in 1857 the slip deficit abruptly decreases to the northwest across the parkfield segment it is 2 m near the town of parkfield and 0 m northwest of middle mountain an m 7 event rupturing all or part of the cholame segment and the southeastern parkfield segment slip decreasing to the northwest would release the accumulated slip and is plausible importantly this study also shows that the change in the pattern of strain release occurs in the middle of the parkfield segment rather than at its ends online material tables showing aseismic and coseismic slip estimations and calculations

holocene changes in fire frequency in the daihai lake region north central china indications and implications for an important role of human activity abstract black carbon bc content in a sediment core from daihai lake inner mongolia was analyzed to reconstruct a high resolution history of fires occurring in northern china during the holocene and to examine the impacts of natural changes and human activities on the fire regime the black carbon mass sedimentation rate bcmsr was disintegrated into two components the background bcmsr and the bcmsr peak with the bcmsr peak representing the frequency of fire episodes both the background bcmsr and the magnitude of the bcmsr peak display a close relation with the percentage of tree pollen from the same sediment core suggesting that regional vegetation type would be a factor controlling the intensity of fires the inferred fire episode frequency for the holocene exhibits two phases of obvious increases i e the first increase from

black carbon records in chinese loess plateau over the last two glacial cycles and implications for paleofires abstract to study the temporal and spatial changes in paleofires over the chinese loess plateau black carbon concentrations were analyzed on the loess paleosol samples from three sections along a north south transect using the orbitally tuned time scales of the sections the black carbon mass sedimentation rates bcmsr were calculated results show that in the last two glacial cycles the bcmsr values in glacial periods are 2 3 times higher than in interglacial periods and the bcmsr variability has a relatively strong precession associated 23 ky period suggesting that the glacial cold dry climate conditions were apt to induce natural fires over the loess plateau comparison of the bcmsr records among the three loess sections demonstrates that natural fire occurrence was much more intensive and frequent in the northern loess plateau than in the southern part coinciding with the previous conclusion that the northern plateau has experienced a drier climate regime in both glacial and interglacial periods the substantial increase in bcmsr of the upper s0 relative to the lower s0 at lingtai and weinan indicates that human activities have exerted a significant influence on fire regimes in the middle and southern loess plateau during late holocene due to the relatively intensive agricultural usage of land