depositional environments of late eocene lignite bearing strata east central texas late eocene lignites in the brazos river valley area occur in parasequence scale cycles containing mostly marine sediments lignite is present at the base of the marine interval and forms the base of the cycle in a majority of cases less frequently lignite is underlain by a thin interval of nonmarine deposits that form the base of the cycle in both situations the lignite is part of a thin transgressive interval cycles are separated by an exposure surface usually marked by plant rooting and or development of a paleosol in the top of the underlying sediments peat accumulated on top of these exposure surfaces and lignite is preserved where marine flooding allowed ocean waters to cover the peat deposits with fine grained sediments producing high ash lignite horizons of great lateral extent but variable thickness and quality this strandplain model of lignite occurrence provides a better understanding of late eocene lignites in texas than the deltaic or fluvial deltaic models previously used the strandplain model of lignite occurrence is appropriate for most of the yegua jackson lignites middle late eocene of texas and should be considered when evaluating depositional conditions of paleogene lignites in the northern gulf coast region a re evaluation of late eocene stratigraphy of the brazos valley area accompanies the documentation of depositional environments

vegetation distribution across the early eocene depositional landscape from palynological analysis abstract the usefulness of palynomorphs in reconstruction of vegetation in the pre quaternary has been hampered by uncertainty in distinguishing local from transported palynomorphs analysis of palynomorph transport in modern settings suggests that the importance of transported palynomorphs in a nonmarine depositional environment depends on its geomorphologic characteristics aerial transport will be a significant source of palynomorphs only if the environment is open waterborne transport depends on the access of water to the depositional environment the importance of transported palynomorphs relative to the local palynomorphs varies among depositional environments and can be assessed in each case in the early eocene of the bighorn basin wyoming five depositional environments pond levee crevasse splay swamp margin swamp reduced floodplain contain distinct palynomorph assemblages as measured by canonical variates analysis the relative importance of transported palynomorphs is greatest in the pond and progressively decreases in the levee reduced floodplain swamp margin and swamp in the pond reworked marine dinoflagellates and bisaccate conifer pollen are high in abundance reflecting transport taxodiaceae and alnus are rare and did not inhabit the vegetation surrounding the pond corylus ulmaceous and fagaceous taxa lived surrounding the pond the levee like the pond contains marine dinoflagellates and bisaccate pollen but in lower numbers than the pond pollen of fagaceae alnus locally and pteridophyte spores reflect the levee vegetation the abundance of pteridophyte spores results from their ability to respond quickly to substrate disturbance reduced floodplains contain pteridophytes taxodiaceae platycarya and plicatopollis swamp margin and swamp palynofloras are similar and are dominated by local plants taxodiaceae alnus platycarya sparganiaceaepollenites and locally pistillipollenites the palynofloral data is consistent with the megafloral record in the same environments this supports the vegetation reconstruction from palynology

southern san andreas fault seismicity is consistent with the gutenberg richter magnitude frequency distribution the magnitudes of any collection of earthquakes nucleating in a region are generally observed to follow the gutenberg richter gr distribution on some major faults however paleoseismic rates are higher than a gr extrapolation from the modern rate of small earthquakes would predict this along with other observations led to the formulation of the characteristic earthquake hypothesis which holds that the rate of small to moderate earthquakes is permanently low on large faults relative to the large earthquake rate wesnousky et al 1983 schwartz and coppersmith 1984 we examine the rate difference between recent small to moderate earthquakes on the southern san andreas fault ssaf and the paleoseismic record hypothesizing that the discrepancy can be explained as a rate change in time rather than a deviation from gr statistics we find that with reasonable assumptions the rate changes necessary to bring the small and large earthquake rates into alignment agree with the size of rate changes seen in epidemic type aftershock sequence modeling where aftershock triggering of large earthquakes drives strong fluctuations in the seismicity rates for earthquakes of all magnitudes the necessary rate changes are also comparable to rate changes observed for other faults worldwide these results are consistent with paleoseismic observations of temporally clustered bursts of large earthquakes on the ssaf and the absence of m 7 earthquakes on the ssaf since 1857

holocene rate of slip and tentative recurrence interval for large earthquakes on the san andreas fault cajon pass southern california abstract detailed mapping of the san andreas fault zone where it crosses cajon creek southern california has revealed a number of late quaternary deposits and geomorphological features offset by the fault radiocarbon dates from alluvial and swamp deposits provide a detailed chronology with which to characterize the activity of the san andreas fault four independent determinations of the slip rate on the san andreas fault yield an average rate of 24 5 3 5 mm yr for the past 14 400 years the similarity of the four values which span different intervals of time from 5900 to 14 400 years ago suggest that the slip rate has been constant during this period the slip rate confirms that the san andreas fault is accumulating slip faster than any other fault in the plate boundary throughout california also the sum of the slip rates on the san andreas 24 5 mm yr and the san jacinto 10 mm yr faults south of their junction is the same as the san andreas north of their junction 35 mm yr an excavation provided evidence for at least two and up to four earthquakes that caused rupture on the fault between 1290 and 1805 a d and tentative evidence for six earthquakes in about the last 1000 years both lines of evidence imply an average recurrence interval for large earthquakes of about 1 to 2 centuries combined with the historic record this investigation indicates that the last major earthquake at cajon creek was probably at the beginning or middle of the 18th century while the record at cajon creek may suggest that the next major earthquake on the san andreas fault is overdue the data can be interpreted to indicate that the recurrence interval for earthquakes on the san andreas south of the 1857 rupture is 3 to 4 centuries and that the anticipated event should not be expected until the next century

behavior of the southernmost san andreas fault during the past 300 years surficial creep occurs at low rates along the coachella valley segment of the san andreas fault which has not produced a large earthquake during the period of historical record geodetic data indicate however that the crust adjacent to this segment of the san andreas fault is accumulating strain at a high rate furthermore neotectonic and paleoseismic data indicate that the fault does produce very large earthquakes every two to three centuries in view of its long term behavior the occurrence of creep along the surficial trace of the fault in the coachella valley is of particular interest along two short reaches of the san andreas fault in the coachella valley measurements of offset geological deposits and man made structures and from alignment arrays and creep meters show that slip rates of 2 4 mm yr near indio and near the salton sea have persisted for the past three centuries this slow aseismic surficial creep is not a transient precursor to seismic failure of this segment of the fault we suggest that the coachella valley segment of the san andreas fault creeps in its upper few kilometers this behavior may be due to tectonically induced high pore pressures in the coarse sediments that abut the fault

strike slip earthquakes on quasi vertical transcurrent faults inferences for general scaling relations the recent occurrence of several large strike slip earthquakes provides the opportunity to review and complement available data on the scaling of seismic moment mo with length of rupture l for large earthquakes depending on their tectonic setting and mechanism for strike slip earthquakes on quasi vertical transcurrent faults the mo versus l relation has a significant change of slope around mo 0 6 0 8 1020 n m and for larger earthquakes mo scales linearly with l this is compatible with models where slip is controlled by the width of the fault also it appears to be easier to categorize large earthquakes by their mechanism strike slip on vertical transcurrent fault versus pure thrust normal than their tectonic setting interplate intraplate

the seismicity along the dead sea fault during the last 60 000 years abstract evidence for unchanging slip rate and a gutenberg richter relation for earthquake distribution along the dead sea fault during the past 60 000 yr are presented the evidence comes from three different segments approximately 100 km apart and from three different timescales prehistoric paleoseismic historical and modern instrumental records the paleoseismic data are based on two different methods in the southern arava valley and the northern jordan valley segments the amount of normal displacement along several faults is used while in the dead sea basin the appearance of brecciated beds which are considered as seismites is used we found that for the southern arava valley segment a constant dip slip rate of 0 5 mm yr can explain the cumulative normal slip during the past 45 000 yr this suggests that normal faulting is only 10 of the total left lateral strike slip motion we also found that for all three segments the paleoseismic and historical records of strong earthquakes lie on the linear extrapolation of the frequency magnitude relation of the instrumental record the calculated b values for all three segments are between 0 85 and 1 similar to other major strike slip faults in the world it is concluded that the gutenberg richter distribution is a stable mode in the tectonic setting of the dead sea fault during the past 60 000 yr

the gutenberg richter or characteristic earthquake distribution which is it abstract paleoearthquake and fault slip rate data are combined with the cit usgs catalog for the period 1944 to 1992 to examine the shape of the magnitude frequency distribution along the major strike slip faults of southern california the resulting distributions for the newport inglewood elsinore garlock and san andreas faults are in accord with the characteristic earthquake model of fault behavior the distribution observed along the san jacinto fault satisfies the gutenberg richter relationship if attention is limited to segments of the san jacinto that are marked by the rupture zones of large historical earthquakes or distinct steps in fault trace the observed distribution along each segment is consistent with the characteristic earthquake model the gutenberg richter distribution observed for the entirety of the san jacinto may reflect the sum of seismicity along a number of distinct fault segments each of which displays a characteristic earthquake distribution the limited period of instrumental recording is insufficient to disprove the hypothesis that all faults will display a gutenberg richter distribution when averaged over the course of a complete earthquake cycle but given that 1 the last 5 decades of seismicity are the best indicators of the expected level of small to moderate size earthquakes in the next 50 years and 2 it is generally about this period of time that is of interest in seismic hazard and engineering analysis the answer to the question posed in the title of the article at least when concerned with practical implementation of seismic hazard analysis at sites along these major faults appears to be the characteristic earthquake distribution

modeling of seismic guided waves at the dead sea transform 1 on several recordings of linear seismometer arrays crossing the arava fault af in the middle east we see prominent wave trains emerging from in fault explosions which we interpret as waves being guided by a fault zone related low velocity layer the af is located in the arava valley and is considered the principal active fault of the mainly n s striking dead sea transform system in this section observations of these wave trains are confined to certain segments of the receiver lines and occur only for particular shot locations they exhibit large amplitudes and are almost monochromatic we model them by a two dimensional 2 d analytical solution for the scalar wave field in models with a vertical waveguide embedded in two quarter spaces a hybrid search scheme combining genetic algorithm and a local random search is employed to explore the multimodal parameter space resolution is investigated by synthetic tests the observations are adequately fit by models with a narrow only 3 12 m wide waveguide with s wave velocity reduced by 10 60 of the surrounding rock we relate this vertical low velocity layer with the damage zone of the af since the location of receivers observing and of shots generating the guided waves respectively match with the surface trace of the fault the thickness of the damage zone of the af at least at shallow depths seems to be much smaller than in other major fault zones this could be due to less total slip on this fault

a note on adding viscoelasticity to earthquake simulators abstract here i describe how time dependent quasi static stress transfer can be implemented in an earthquake simulator code that is used to generate long synthetic seismicity catalogs most existing seismicity simulators use precomputed static stress interaction coefficients to rapidly implement static stress transfer in fault networks with typically tens of thousands of fault patches the extension to quasi static deformation which accounts for viscoelasticity of earth s ductile lower crust and mantle involves the precomputation of additional interaction coefficients that represent time dependent stress transfer among the model fault patches combined with defining and evolving additional state variables that track this stress transfer the new approach is illustrated with application to a california wide synthetic fault network

variable rates of late quaternary strike slip on the san jacinto fault zone southern california three strike slip displacements of strata with known approximate ages have been measured at two locations on the san jacinto fault zone minimum horizontal offset between 5 7 and 8 6 km in no more than 0 73 m y northeast of anza indicates 8 12 mm yr average slip rate since late pleistocene time two measures of more recent displacement are based on trenching studies of stratigraphic offsets on the coyote creek fault in western imperial valley horizontal slip of 1 7 m has been calculated for the youngest sediment of lake cahuilla since its deposition 275 510 yr b p the corresponding slip rate is 2 8 5 0 mm yr right lateral offset of 10 9 m measured on a buried stream channel older than 5060 yr b p but younger than 6820 yr b p yields average slip rates for the intermediate time periods 400 to 6000 yr b p of 1 2 mm yr the average rates of slip for these three time intervals suggest a relatively quiescent period for the san jacinto fault zone from about 4000 b c to about 1600 a d to the extent that long term variations in seismic activity of major strike slip faults elsewhere are known fluctuations in slip rate for the san jacinto fault would not appear to be abnormal if the san jacinto and adjacent segments of the san andreas fault alternately assume dominant roles in absorbing motion between the pacific and american plates perhaps even more recently than 400 yr ago the san andreas fault south of the transverse ranges expressed most of the motion but has since become relatively inactive

earthquake frequency distribution and the mechanics of faulting the level of intraplate seismicity in japan generally shows a positive correlation with the density of quaternary faulting in southwest japan where intraplate seismicity is concentrated on land rates of seismic moment release m 0 are similar when calculated from either the 400 year historical record of seismicity or geologically determined slip rates of quaternary faults a data set of 18 earthquakes with seismic moments m0 ranging from 0 01 to 3 1027 dyn cm shows a relationship between rupture lengthl and m0 log m0 23 5 1 94 log l when seismic moment on each quaternary fault is assumed to occur in discrete events every t m0 m 0g years where m0 is estimated for a rupture extended over the entire fault length and m 0g is proportional to the slip rate of each quaternary fault the moment frequency distribution of earthquakes log n a b log m0 predicted from the geologic record is virtually identical to that seen with the 400 year record of seismicity in contrast if it is assumed that earthquakes on each fault occur according to the gutenberg richter relation we obtain poor agreement with the observed seismicity thus while regional seismicity satisfies the relation log n a b log m0 or equivalently log n a b log m where m is magnitude it appears that seismicity on individual faults does not this further implies that the primary factor that leads to the magnitude frequency distribution in regional seismicity studies is the relative distribution of the slip rates and lengths of preexisting faults

on the fundamental difference between coal rank and coal type abstract this article addresses the fundamental difference between coal rank and coal type while theoretically settled long ago as being different aspects of coal systems science the two concepts are still often confounded in recent years this has resulted in the publication of several works stating that coal type changes with coal rank coal type refers solely to coals depositional origin and the maceral mineral admixture resulting from that origin coal types typically fall in to two categories humic coals developed from peat and sapropelic coals developed from organic mud either type may be allocthonous or autochthonous and within types further refinement of depositional environment can be made coal rank refers to the changes in geochemistry and resultant changes in reflectance caused by increasing thermal maturity of the coal thus it provides an overprint of maturity on existing coal types with proper techniques such as use of crossed polars and etching maceral forms can be differentiated even at high ranks and the original coal type determined

application of pattern recognition techniques to earthquake catalogs generated by model of segmented fault systems in three dimensional elastic solids techniques and seismicity parameters described by eneva and ben zion 1997 are used to examine synthetic earthquake catalogs generated by ben zion 1996 for precursory patterns of large model events different model realizations represent various levels of fault zone disorder these include models with uniform properties u a parkfield type asperity a fractal brittle properties f and multi size scale heterogeneities m the seismicity parameters used are based on information contained in typical earthquake catalogs reflecting earthquake distribution in space time and size the analysis highlights the complexity of the information content of the synthetic earthquake catalogs simple repetitive precursory signals have not been found however local extrema in the examined parameters are found to have significant association in time with large events thus our techniques and parameters may be useful for intermediate term earthquake prediction especially when parameters are used in combinations some analysis results are the same for all model realizations and some depend on the model features characterizing all catalogs are as follows 1 large model events are statistically predictable on the basis of patterns in the distribution of smaller events 2 for a given parameter the type of precursory extrema maxima or minima is the same for all models 3 the interparameter correlation for any parameter pair has the same sign positive or negative in all models 4 the large events are neither slip nor time predictable based on previous large events results that differ from model to model include the following 1 the degree of predictability of large events correlates with the degree of regularity in the assumed fault properties following the order u f a and m 2 there is no one to one correlation between type of precursory extrema maxima or minima and type of precursory trends increase or decrease this produces great variations in observable trends for any given parameter both from model to model and for different events in the same model 3 the interparameter correlations vary among models with the highest correlations in model f most discussed patterns are in agreement with observations from seismically active zones laboratory models and mining induced seismicity

late quaternary rate of slip along the san jacinto fault zone near anza southern california the anza section of the san jacinto fault southern california has not experienced a groundbreaking earthquake since at least 1918 and probably since before 1899 leading previous workers to designate this 20 km long fault segment as a seismic gap study of displaced pleistocene and holocene alluvial fan and fluvial deposits across the san jacinto fault near anza california dated using 14c and soil development age control indicates a minimum right lateral slip rate of 9 2 2 mm yr since 9 5 ka and a slip rate of 11 9 5 mm yr since 14 ka 12 9 5 mm yr since 17 ka and 13 10 6 mm yr since 50 ka these estimates agree with a previously determined 700 ka to present minimum slip rate of 10 2 mm yr based on an estimated average slip rate of 12 mm yr from the longer term slip rate estimates about 0 8 m of potential slip has accumulated if the 1918 earthquake broke the anza segment over 1 1 m of potential slip has accumulated if the last earthquake occurred prior to 1899 these data attest to the potential for an earthquake m6 5 for this section of the fault

the superstition hills california earthquakes of 24 november 1987 the 24 november 1987 superstition hills earthquakes occurred on the conjugate northwest striking right lateral superstition hills fault and a previously unknown northeast striking left lateral structure defined by a lineation of hypocenters extending from the superstition hills fault to the brawley seismic zone master event locations of the earthquakes using caltech usgs seismic network data reveal the following the first main shock 33 4 9 n 115 47 7 h 10 6 km m s 6 2 0154 gmt on the northeast striking structure and its foreshocks co locate events on the northeast structure cluster in space and time and some aftershocks occur in the brawley seismic zone the second main shock 33 0 9 n 115 50 9 w h 1 9 km m s 6 6 1315 gmt on the superstition hills fault was 12 hr after the first main shock and initiated at shallow depth where the two trends join aftershocks of the second main shock lie in a northwest trend between the superstition hills and superstition mountain faults and have a sharply defined western edge the extent of the northwest trend aftershocks is not coincident with surface rupture on the superstition hills fault in general the earthquakes in the northeast trend are deep and the earthquakes in the northwest trend are shallow we compare the earthquake distribution to the distribution of crystalline basement rocks defined from a refraction study of fuis et al 1982 the earthquake locations and extent of aftershock activity appear to be controlled by the presence of crystalline basement rocks

earthquake statistics at parkfield 2 probabilistic forecasting and testing construct two probabilistic forecasts h 1 with a spatially varying b value and h 2 with a uniform b value and test these hypotheses against each other both hypotheses use a spatially varying seismicity level a value determined from past seismicity we used a range of sampling parameters magnitude threshold cell size etc to assure robust results we found that in most of the tests hypothesis h 1 showed a higher likelihood than h 2 although both are a poor approximation to the seismicity data the most positive results for h 1 are obtained for testing magnitude ranges down to m 1 5 and with sampling radii as defined in paper 1 as appropriate for parkfield the superior performance of h 1 suggests that spatially varying b values should be considered in earthquake forecasts index terms 7215 seismology earthquake parameters 7223 seismology seismic hazard assessment and prediction 7230 seismology seismicity and seismotectonics keywords earthquake statistics probabilistic forecasting parkfield

geological and historical evidence of irregular recurrent earthquakes in japan great m 8 earthquakes repeatedly occur along the subduction zones around japan and cause fault slip of a few to several metres releasing strains accumulated from decades to centuries of plate motions assuming a simple characteristic earthquake model that similar earthquakes repeat at regular intervals probabilities of future earthquake occurrence have been calculated by a government committee however recent studies on past earthquakes including geological traces from giant m 9 earthquakes indicate a variety of size and recurrence interval of interplate earthquakes along the kuril trench off hokkaido limited historical records indicate that average recurrence interval of great earthquakes is approximately 100 years but the tsunami deposits show that giant earthquakes occurred at a much longer interval of approximately 400 years along the japan trench off northern honshu recurrence of giant earthquakes similar to the 2011 tohoku earthquake with an interval of approximately 600 years is inferred from historical records and tsunami deposits along the sagami trough near tokyo two types of kanto earthquakes with recurrence interval of a few hundred years and a few thousand years had been recognized but studies show that the recent three kanto earthquakes had different source extents along the nankai trough off western japan recurrence of great earthquakes with an interval of approximately 100 years has been identified from historical literature but tsunami deposits indicate that the sizes of the recurrent earthquakes are variable such variability makes it difficult to apply a simple characteristic earthquake model for the long term forecast and several attempts such as use of geological data for the evaluation of future earthquake probabilities or the estimation of maximum earthquake size in each subduction zone are being conducted by government committees

distribution of the right lateral strike slip motion from the main recent fault to the kazerun fault system zagros iran evidence from present day gps velocities article i nfo gps measurements across the kazerun fault system in the zagros mountain belt provide first instantaneous velocities on the different segments these results are closely consistent with the geological fault slip rates over 150 ka implying stable velocities over a longer period the present day strike slip motion is distributed from the main recent fault to the n trending kazerun fault system along a preferential en echelon fault zone included in a more distributed fan shape fault pattern the hormuz salt decoupling layer cannot be the only cause of a sedimentary spreading because seismicity attests these faults are rooted in the basement the dena fault 3 7 mm yr transfers the mrf fault slip mainly to the kazerun 3 6 mm yr and slightly to the high zagros and sabz pushan faults 1 5 mm yr and the kazerun fault further to the kareh bas fault 3 4 mm yr total geological horizontal offsets associated with gps slip rates help inferring precise fault slip onset ages the successive onsets deduced by this approach imply that the right lateral strike slip activity of the mrf has propagated in time southeastward to the dena segment and then to the kazerun segment and to the kareh bas fault

characterization of fault zones there are currently three major competing views on the essential geometrical mechanical and mathematical nature of faults the standard view is that faults are possibly segmented and heterogeneous euclidean zones in a continuum solid the continuum euclidean view is supported by seismic gravity and electromagnetic imaging studies by successful modeling of observed seismic radiation geodetic data and changes in seismicity patterns by detailed field studies of earthquake rupture zones and exhumed faults and by recent high resolution hypocenter distributions along several faults the second view focuses on granular aspects of fault structures and deformation fields the granular view is supported by observations of rock particles in fault zone gouge by studies of block rotations and the mosaic structure of the lithosphere which includes the overall geometry of plate tectonics by concentration of deformation signals along block boundaries by correlation of seismicity patterns on scales several times larger than those compatible with a continuum framework and by strongly heterogeneous wave propagation effects on the earth s surface the third view is that faults are fractal objects with rough surfaces and branching geometry the fractal view is supported by some statistical analysis of regional hypocenter locations by long range correlation of various measurements in geophysical boreholes by the fact that observed power law statistics of earthquakes are compatible with an underlying scale invariant geometrical structure by geometrical analysis of fault traces at the earth s surface and by measurements of joint and fault surfaces topography

waveform modeling of the november 1987 superstition hills earthquakes long period body wave data recorded at teleseismic distances and strong motion data at pasadena for the superstition hills earthquakes of 24 november 1987 are modeled to obtain the source parameters we will refer to the event that occurred at 0153 ut as eq1 and the event at 1316 ut as eq2 at all distances the first earthquake appears to be a simple left lateral strike slip event on a fault striking ne it is a relatively deep event with a source depth of 10 km it has a teleseismic moment of 2 7 10 25 dyne cm the second and more complex event was modeled in two ways by using eq1 as the green s function and by using a more traditional forward modeling technique to create synthetic seismograms the first method indicated that eq2 was a double event with both subevents similar but not identical to eq1 and separated by about 7 5 sec from the synthetic seismogram study we obtained a strike of 305 for the first subevent and 320 for the second both have dips of 80 and rakes of 175 the first subevent has a moment of 3 6 10 25 which is half that of the second we obtain depths of at least 6 km the teleseismic data indicate a preferred subevent separation of 30 km with the second almost due south of the first but the error bounds are substantial this would suggest that the subevents occurred on conjugate faults the strong motion data at pas however imply a much smaller source separation with the sources probably produced by asperities

palynology and paleoecology of lignites from the manning formation jackson group outcrop in the lake somerville spillway of east central texas abstract four palynomorph assemblages whose parent plants contributed to the formation of the lignite occur in the lignite seams and associated sediments from the manning formation jackson group outcrop in the lake somerville spillway of texas the cicatricosisporites laevigatosporites fern assemblage occurs in the middle and upper seam and probably derived from a freshwater herbaceous mire community the momipites coryloides arecipites columellus liliacidites assemblage occurs in all three seams and probably derived from a freshwater mire forest with an open canopy or shrub community the momipites coryloides nyssa rhoipites angustus assemblage occurs in the lower and middle seams and probably derived from a different freshwater mire forest the cupuliferoipollenites cupuliferoidaepollenites liblarensis siltaria cf s scabriextima assemblage occurs at the top of the lower and middle seams which are overlain by marine sediments the association between cupuliferoipollenites dominance and the presence of marine diatoms and brackish or marine trace fossils in the lignite suggests that this assemblage may have derived from a mangrove i e marine or brackish mire forest however other factors may influence its distribution ailanthipites berryi possibly derived from a tree or shrub related to the tree of heaven predominates in the claystone underlying the lower lignite seam and may have colonized the coastal plain prior to the initiation of peat accumulation we can differentiate lignite samples dominated by fern spores momipites pollen and cupuliferoipollenites pollen based on gas chromatography mass spectrometry gc ms fragmentograms of triterpanes m z 191 and steranes m z 217 the lignite layers dominated by each palynomorph assemblage appear to have distinct sources and different early diagenetic pre coalification histories

kinematics of present crust and mantle flow in southern california in the southern california region published geologic studies of prehistoric fault offsets yield at least 81 rates of slip covering various periods of time chiefly since the opening of the gulf of california these rates together with the known geometries of active faults are used to constrain a hand fit block model for present horizontal velocity of the crust the assumptions employed are that these rates apply to the present that the blocks are internally rigid down to the greatest depth of earthquakes and that the over all pacific north american plate motion is correctly given by global models the resulting model fits 67 data within their uncertainties 10 more with a small discrepancy 1 mm yr and fails to accommodate only 4 data 2 of which are inconsistent with other data nominal precision is good 3 mm yr but accuracy and uniqueness are both suspect because many block boundaries are questionable despite its many local defects this model suggests four reliable regional conclusions first the rate of shortening on the south side of the transverse ranges varies from 6 to 14 mm yr increasing eastward which implies an unrecognized seismic hazard unless the motion is taken up by folding or fault creep second the pattern of block rotation rates is quite different from the pattern of rotations shown by tertiary paleomagnetic declinations which implies some major pliocene reorganization of blocks third the great bend left step of the plate boundary fault system in the transverse ranges appears to be straightening gradually by a 3 m y clockwise rotation relative to both plates finally if it is assumed that plate shortening has been occurring at this bend since the early pliocene and that crust and upper mantle velocities are similar then this model predicts mantle lithosphere downwelling to at least 250 km depth beneath the transverse ranges this prediction is consistent with upper mantle seismic velocity structure

straightening of the northern san jacinto fault california as seen in the fault structure evolution of the san jacinto valley stepover abstract we investigate a releasing stepover between the casa loma and claremont strands of the northern san jacinto fault zone to evaluate the late quaternary structural evolution of the fault zone and to assess the likelihood of a rupture jumping across the stepover our new cone penetration test cpt and trench observations along the claremont fault at mystic lake indicate that the main strand of the claremont fault has jumped nearly a half kilometer westward into the san jacinto releasing stepover during the late quaternary multiple faults are inferred from the cpt data within a small sag at the northeast side of the stepover that cuts through younger stratigraphy to the west of the basin bounding fault near mystic lake previous seismic reflection data also suggest the presence of a young fault that cuts basin strata beneath the middle of mystic lake farther west of our study area numerous tectono geomorphic features observed in satellite and light detection and ranging digital elevation model lidar dem imagery are interpreted to delineate the location of the currently active faults including a zone of faults that cut across the basin from the northern end of the casa loma fault to the claremont fault seismicity observations suggest the presence of many faults within the stepover zone finally new paleoseismic data from the mystic lake site suggest that some late holocene earthquakes may have jumped the stepover all of these observations suggest that the san jacinto stepover which has been used as the primary basis for segmenting the northern san jacinto fault zone is being bypassed and that the fault zone may now be capable of larger earthquakes than previously expected

heterogeneity and the earthquake magnitude frequency distribution regional earthquake populations are widely observed to have power law magnitude frequency statistics whether earthquake distributions on individual faults are similarly power law is presently the subject of considerable research effort recent careful observations suggest that event statistics on rough faults are power law whereas earthquake distributions on smooth faults are better described by a characteristic model in which there are more large earthquakes than would be expected by extrapolation from the distribution of small events here the relation between heterogeneity and the magnitude frequency distribution is investigated in a cellular automaton that includes new nearest neighbor stress transfer rules which produce realistic stress concentrations the results agree with the suggestion that smooth faults have more characteristic earthquake distributions and support the view that an earthquake s size is controlled by rupture arrest

source parameters of the 1933 long beach earthquake regional seismographic network and teleseismic data for the 1933 m l 6 3 long beach earthquake sequence have been analyzed both the teleseismic focal mechanism of the main shock and the distribution of the aftershocks are consistent with the event having occurred on the newport inglewood fault the focal mechanism had a strike of 315 dip of 80 to the northeast and rake of 170 relocation of the foreshock main shock aftershock sequence using modern events as fixed reference events shows that the rupture initiated near the huntington beach newport beach city boundary and extended unilaterally to the northwest to a distance of 13 to 16 km the centroidal depth was 10 2 km the total source duration was 5 sec and the seismic moment was 5 10 25 dyne cm which corresponds to an energy magnitude of m w 6 4 the source radius is estimated to have been 6 6 to 7 9 km which corresponds to a brune stress drop of 44 to 76 bars both the spatial distribution of aftershocks and inversion for the source time function suggest that the earthquake may have consisted of at least two subevents when the slip estimate from the seismic moment of 85 to 120 cm is compared with the long term geological slip rate of 0 1 to 1 0 mm yr along the newport inglewood fault the 1933 earthquake has a repeat time on the order of a few thousand years

earthquakes quaternary faults and seismic hazard in california data describing the locations slip rates and lengths of quaternary faults are the primary basis in this work for constructing maps that characterize seismic hazard in california the expected seismic moment m0e and the strength of ground shaking resulting from the entire rupture of each mapped fault or fault segment are estimated using empirical relations between seismic moment m0 rupture length source to site distance and strong ground motions assuming a fault model whereby the repeat time t of earthquakes on each fault equals m0e m0g where the moment rate m0g is proportional to fault slip rate it is observed that the moment frequency distribution of earthquakes predicted from the geologic data agrees well with the distribution determined from a 150 year historical record the agreement is consistent with the argument that the geologic record of quaternary fault offsets contains information sufficient to predict the average spatial and size distribution of earthquakes through time in california the estimates of t for each fault are the foundation for constructing maps that depict the average return period of 0 1g peak horizontal ground accelerations and the horizontal components of peak acceleration peak velocity and the pseudovelocity response at 1 period and 5 damping expected to occur at the level of 0 1 probability during a 50 year period of time a map is also formulated to show the probability that 0 1g horizontal ground accelerations will occur during the next 50 years the maps serve to illustrate the potential value of quaternary fault studies for assessing seismic hazard interpretation of available slip rates indicates that the largest and most frequent occurrence of potentially destructive strong ground motions are associated principally with the san andreas san jacinto calaveras hayward and ventura basin fault zones other regions of similarly high hazard may yet remain unrecognized this inadequacy results primarily from an incomplete data set numerous faults for example are mapped along the coastal region of northern california and within the modoc plateau but relatively few studies relating to fault slip rate are reported a similar problem exists for other stretches of coastal california where marine reflection studies provide evidence of active faulting offshore yet yield little or no information of fault slip rate geological and geophysical field studies can work to remove these deficiencies a concerted effort to locate and define rates of activity on all faults in california is the most promising means to further quantify present levels of seismic hazard in california

surficial offsets on the central and eastern garlock fault associated with prehistoric earthquakes geomorphic features offset along the central and eastern garlock fault record the amount of surface slip associated with prehistoric earthquakes along the easternmost 90 km of the fault the smallest offsets cluster around 2 3 m of left lateral slip apparently associated with the most recent earthquake on this portion of the fault larger offsets along this part of the fault especially in pilot knob valley cluster around values consistent with 2 4 m of slip in each of the past several events farther west south of el paso mountains offset geomorphic features suggest that each of the past two earthquakes on this stretch of the garlock fault was produced by about 7 m of slip whereas the third event back was produced by about 4 m of slip vertical displacements of geomorphic features range from 0 to 30 of the left lateral offsets within pilot knob valley along the southern side of the slate range vertical displacements are consistently up on the northern side whereas within the avawatz mountains both north and south side up vertical displacements are present on the basis of the geomorphic offsets the geometry of the garlock fault and the precedents set by historical strike slip earthquakes elsewhere a number of different rupture patterns are plausible these range from rupture of the entire garlock fault in a single event with a maximum magnitude of about mw 7 8 to separate rupture of the western segment and of the central and eastern segments combined with approximate magnitudes mw 1 1 and mw 7 5 respectively to separate rupture of even shorter segments producing earthquakes of magnitudes mw 6 6 to mw 7 5 in conjunction with available slip rates for the garlock fault the geomorphic offsets suggest that average recurrence intervals are probably within the range of 600 1200 years south of el paso mountains about 200 750 years in searles valley about 200 1300 years in pilot knob valley and about 200 3000 years near leach lake and in the avawatz mountains

paleomagnetic measurement of nonbrittle coseismic deformation across the san andreas fault at pallett creek paleomagnetic data have been obtained to address a problem at the pallett creek paleoseismological site the 9 mm yr slip rate determined from three dimensional mapping of late holocene offsets across discrete faults is only a quarter of the expected value we suspected that nonbrittle deformation adjacent to the faults might account for the 26 mm yr discrepancy in our search for the missing slip we collected and analyzed 264 paleomagnetic samples from a 53 m wide transect across the fault zone half the samples came from a unit deposited immediately after a large earthquake of about a d 1480 these samples were affected by two large earthquakes that involved rupture at the site in 1812 and 1857 we collected the other half of the samples from a slightly older bed one that was deposited before the earthquake of about a d 1480 relative to control groups composed of 10 samples and collected 50 m from the fault samples closer to the fault display clockwise rotations of 30 or less if interpreted as block rotations the data from the older unit imply that it has sustained a total of 14 0 2 9 m of dextral warp during the past three major earthquakes and that the younger unit has experienced a total of 8 5 1 0 m of warp during the most recent two combining these values with the amounts of dextral slip across the mapped fault planes yields dextral offsets of 5 5 6 25 and 6 25 m for the events of a d 1480 1812 and 1857 and a slip rate of 35 6 6 7 mm yr this slip rate averaged over the past three complete seismic cycles is consistent with published rates from other sites offsets associated with the past three events are remarkably similar these amounts however appear independent of the length of interseismic cycles these observations suggest 1 that this part of the san andreas fault has a characteristic strength and 2 that conventional concepts of strain accumulation and relief for example time and slip predictable models of earthquake occurrence are unrealistic

implications of fault slip rates and earthquake recurrence models to probabilistic seismic hazard estimates abstract increasingly fault slip rates are being used to constrain earthquake recurrence relationships for site specific probabilistic seismic hazard ground motion assessments this paper shows the sensitivity of seismic hazard assessments to variations in recurrence models and parameters that incorporate fault slip rates two models are considered to describe the partitioning of the slip rate or seismic moment rate into various magnitude earthquakes an exponential magnitude distribution and a characteristic earthquake distribution assuming an exponential distribution the activity rate n m 0 is constrained by the upper bound magnitude m u the b value for the region and the fault slip rate s for a given s variations in m u and b value have significant effects on recurrence and computed hazard depending on whether the assumption is made that the seismicity rate is constant or the moment rate is constant there is increasing evidence that the characteristic earthquake model is more appropriate for individual faults than the exponential magnitude distribution based on seismicity data from areas having repeated large earthquakes a generalized recurrence density function is developed and the resulting recurrence relationship requires only m u b value and s a comparison of the recurrence relationships from this model with the historical seismicity and paleoseismicity data on the wasatch and san andreas faults shows a good match the computed hazard based on the characteristic earthquake model differs from that obtained for the exponential model as a function of the fault to site distance and the acceleration level one check on the recurrence models using slip rate is to compare over large regions activity rates based on seismicity data and slip rate data such a comparison in the western transverse ranges shows a reasonable match for both the exponential and characteristic earthquake models in the moderate to large magnitude range

does maximum earthquake size depend on focal depth abstract while the gutenberg richter law gr with b value of 1 0 is an inexact description of the earthquake frequency magnitude distribution it does provide a convenient statistical basis for identifying when the largest earthquakes in a catalog are either anomalously large or anomalously small when the largest earthquakes are as predicted by the gr distribution it is inappropriate to infer that the largest historically known earthquake is the largest possible only when the largest observed earthquakes are significantly smaller than predicted can we infer that the largest possible earthquakes have occurred analysis of the global historical catalog demonstrates that at nearly all depths the largest deep and intermediate earthquakes have sizes close to those predicted by a gr distribution with b of 1 0 only between about 300 to 450 km and beneath 600 km are the largest known earthquakes somewhat larger than predicted however when geographically isolatable subgroups within catalogs are considered separately largest earthquakes that are either anomalously large or small are quite common often this is because individual regions have b values much different than 1 0 alternatively sometimes there appear to be physical constraints limiting the size of the largest possible earthquake as examples illustrating these assertions this article evaluates two subgroups deep focus earthquakes occurring beneath spain and intermediate depth earthquakes in the bucaramanga colombia nest

statistical evaluation of characteristic earthquakes in the frequency magnitude distributions of sumatra and other subduction zone regions 1 if subduction zone earthquakes conform to a characteristic model in which persistent segments fail at predictable stress levels due to the steady accumulation of tectonic loading historical seismicity may constrain the occurrence of future events we test this model for earthquakes on the sumatra andaman megathrust and other subduction zones using frequency magnitude distributions using simulations we show that poisson confidence intervals correctly account for the counting errors of histogram data these confidence intervals demonstrate that we cannot reject the gutenberg richter distribution in favor of a characteristic model in any of the real catalogues tested a visual bias in power law count data at high magnitudes combined with a sample bias for large earthquakes is sufficient to explain candidate characteristic events this result implies that historical earthquakes are likely poor models for future events and that monte carlo simulations will provide a better assessment of earthquake and associated hazards

fault trace complexity cumulative slip and the shape of the magnitude frequency distribution for strike slip faults a global survey summary we examine whether the shape of the magnitude frequency distribution for strike slip faults is described by the gutenburg richter relationship log n a bm or by the characteristic earthquake model by analysing a data set of faults from california mexico japan new zealand china and turkey for faults within regional seismic networks curves of the form log n yrpl a bm where n yr is the number of events per year equal to magnitude m are fit to the instrumental record of seismicity and geological data are used to estimate independently the size and recurrence rate of the largest expected earthquakes that would rupture the total length of the fault extrapolation of instrumentally derived curves to larger magnitudes agrees with geological estimates of the recurrence rate of the largest earthquakes for only four of the 22 faults if uncertainties in curve slope are considered and significantly underestimates the geological recurrence rates in the remaining cases also if we predict the seismicity of the faults as a function of fault length and slip rate and the predicted seismicity is distributed in accord with the gutenburg richter relationship we find the predicted recurrence rate to be greater than the observed recurrence rates of smaller earthquakes along most faults if individual fault zones satisfy the gutenburg richter relationship over the long term our observations imply that during the recurrence interval of the largest expected earthquakes the recurrence of lesser sized events is not steady but rather strongly clustered in time however if the instrumental records provide an estimate of the long term rate of small to moderate earthquakes along the faults our observations imply that the faults generally exhibit a magnitude frequency distribution consistent with the characteristic earthquake model also we observe that the geometrical complexity of strike slip faults is a decreasing function of cumulative strike slip offset the four faults we observe to be consistent with the gutenburgrichter relationship are among those characterized by the least amount of cumulative slip and greatest fault trace complexity we therefore suggest that the ratio of the recurrence rate of small to large earthquakes along a fault zone may decrease as slip accumulates and the fault becomes smoother

laboratory constraints on models of earthquake recurrence in this study rock friction stick slip experiments are used to develop constraints on models of earthquake recurrence constant rate loading of bare rock surfaces in high quality experiments produces stick slip recurrence that is periodic at least to second order when the loading rate is varied recurrence is approximately inversely proportional to loading rate these laboratory events initiate due to a slip rate dependent process that also determines the size of the stress drop and as a consequence stress drop varies weakly but systematically with loading rate this is especially evident in experiments where the loading rate is changed by orders of magnitude as is thought to be the loading condition of naturally occurring small repeating earthquakes driven by afterslip or low frequency earthquakes loaded by episodic slip the experimentally observed stress drops are well described by a logarithmic dependence on recurrence interval that can be cast as a nonlinear slip predictable model the fault s rate dependence of strength is the key physical parameter additionally even at constant loading rate the most reproducible laboratory recurrence is not exactly periodic unlike existing friction recurrence models we present example laboratory catalogs that document the variance and show that in large catalogs even at constant loading rate stress drop and recurrence covary systematically the origin of this covariance is largely consistent with variability of the dependence of fault strength on slip rate laboratory catalogs show aspects of both slip and time predictability and successive stress drops are strongly correlated indicating a memory of prior slip history that extends over at least one recurrence cycle

probabilities of occurrence of large plate rupturing earthquakes for the san andreas san jacinto and imperial faults california 1983 2003 the san andreas san jacinto and imperial faults in california are divided into 19 segments conditional probabilities are calculated that a particular segment will be the site of a large plate rupturing earthquake i e an event that breaks the entire down dip extent of the seismogenic zone during the next 20 years the sizes of such events which account for most of the slip that occurs seismically appear to vary greatly for different segments of these faults repeat time of large shocks coseismic displacement moment release rupture length and seismic magnitude appear to correlate with one another and to be a function of the tectonic style of different parts of those fault zones tectonic inhomogeneities on a scale of about 1 to 100 km are much larger than displacement in any single seismic event and may be regarded as being invariant in their effects upon earthquake generation over many cycles of large shocks it is this invariance that appears to lead to a given segment of a fault rupturing repeatedly in events of nearly the same size since repeat time varies however for a given segment of a fault a simple probabilistic approach is used to forecast the likelihood of large future earthquakes for each segment using as input the time of the last large shock the average recurrence time and the standard deviation of time intervals between events dates of the last large shocks are available for most of the segments investigated repeat times are estimated from times of historic and prehistoric events tectonic similarity and times calculated from coseismic displacement in the last large shock divided by a rate of fault motion or strain buildup the standard deviation of time intervals divided by the average repeat time is close to 1 3 for three fault segments in california for which data are available on historic and prehistoric earthquakes that normalized value is adopted for all calculations of conditional probability magnitudes and seismic moments of future plate rupturing events are estimated for each fault segment several of the segments have well constrained probabilities for rupture during the next 20 years whereas others have large uncertainties eight of the segments constituting about 40 of the total lengths of the three faults have moderate to high probability and thus should be instrumented and studied extensively so as to provide shorter time warnings in some cases two adjacent segments may be nearly in phase in their loading history and may break in a single event the segment of the san andreas fault from opposite san jose to san juan bautista which ruptured less than 1 5 m in 1906 and which probably also broke in 1838 is calculated to have a moderate to high probability of an earthquake of magnitude 6 to during the next 20 years a 325 km section of the southern san andreas between tejon pass and the salton sea has about a 25 chance of rupturing in a shock of magnitude near 8 during the next 20 years all the other segments have only a small chance i e less than 5 to 10 of rupturing in an event of magnitude near 8 during that interval

holocene slip rate of the central garlock fault in southeastern searles valley california a late pleistocene shoreline at the overflow level of searles lake has been displaced 82 to 106 m preferred value is 90 m in a left lateral sense and 2 5 m net north side up along the garlock fault at the southeastern corner of searles valley previously published radiocarbon dates from both surface and subsurface strata indicate that the most recent highstand of searles lake ended sometime between 10 000 and 13 800 14c years ago the maximum slip rate of the garlock fault in southeastern searles valley is thus 11 mm 14c yr if part of the offset of the shoreline occurred during older lakestands then the slip rate may be somewhat less a channel incised after the most recent highstand however is offset about 68 m indicating that the minimum slip rate is 5 mm 14c yr subjective evaluation of the constraints on the offset and on the age of the shoreline yields a preferred rate of 6 8 mm 14c yr at this site assuming bard et al s 1990 recent calibration of the radiocarbon time scale the calibrated slip rate of the garlock fault is between 4 and 9 mm yr with a preferred value of 5 7 mm yr this estimate is similar to a previous estimate of the holocene slip rate and is slightly less than an estimate derived from modelling of geodetic data extension north of the garlock fault in indian wells and searles valleys contributes no more than 3 mm yr left slip to the garlock fault

irregular recurrence of large earthquakes along the san andreas fault evidence from trees old trees growing along the san andreas fault near wrightwood california record in their annual ring width patterns the effects of a major earthquake in the fall or winter of 1812 to 1813 paleoseismic data and historical information indicate that this event was the san juan capistrano earthquake of 8 december 1812 with a magnitude of 7 5 the discovery that at least 12 kilometers of the mojave segment of the san andreas fault ruptured in 1812 only 44 years before the great january 1857 rupture demonstrates that intervals between large earthquakes on this part of the fault are highly variable this variability increases the uncertainty of forecasting destructive earthquakes on the basis of past behavior and accentuates the need for a more fundamental knowledge of san andreas fault dynamics

production preservation and prediction of source rock facies in deltaic settings abstract this article hypothesizes that production and preservation of source rock type facies in deltaic systems both landward and seaward of a coastline is mutually exclusive time successive and related to the dynamics of relative sea level sedimentologic research in the holocene mississippi and rhone delta complexes suggests that rheotrophic peats and associated organic rich beds preferably accumulate in the accommodation space created behind landward stepping shorelines in a transgressive systems tract tst such a setting also allows for a sufficient supply of recharging fresh nutrient rich groundwater into the peat forming mires kosters e c suter j r 1993 facies relationships and systems tracts in the late holocene mississippi delta plain journal of sedimentary petrology 63 4 727 733 independently carried out quantitative paleoecological studies in the same delta systems and in addition in the orinoco and po deltas suggest that in a progradational setting highstand systems tract hst seasonally discharged nutrient and sediment laden river waters on the shelf may give rise to anoxia or dysoxia subsequent overfertilization of the shelf leads to accumulation of organic rich mud belts on the shelf vanderzwaan g j jorissen f j 1991 biofacial patterns in river induced anoxia in tyson r v pearson t h eds modern and ancient continental shelf anoxia geological society of london special publication no 58 pp 65 82 thus production and preservation of source rock type facies landward of a shoreline as peats and related sediments is preferred in a tst when accommodation space and nutrient supply are landward of the shoreline vice versa production and preservation of such facies seaward of a shoreline as organic rich shelf muds occurs preferentially in a highstand systems tract in that situation accommodation space is on the shelf where river fed nutrients are supplied as well this hypothesis suggests further potential for application of sequence stratigraphic concepts for improved understanding of the occurrence of source rock type facies

a more precise chronology of earthquakes produced by the san andreas fault in southern california improved methods of radiocarbon analysis have enabled us to date more precisely the earthquake ruptures of the san andreas fault that are recorded in the sediments at pallett creek previous dates of these events had 95 confidence errors of 50 100 calendar years new error limits are less than 23 calendar years for all but two of the dated events this greater precision is due to larger sample size longer counting time lower background noise levels more precise conversion of radiocarbon ages to calendric dates and better stratigraphic constraints and statistical techniques the new date ranges with one exception fall within the broader ranges estimated previously but our estimate of the average interval between the latest 10 episodes of faulting is now about 132 years variability about the mean interval is much greater than was suspected previously five of the nine intervals are shorter than a century three of the remaining four intervals are about two to three centuries long despite the wide range of these intervals a pattern in the occurrence of large earthquakes at pallett creek is apparent in the new data the past 10 earthquakes occur in four clusters each of which consists of two or three events earthquakes within the clusters are separated by periods of several decades but the clusters are separated by dormant periods of two to three centuries this pattern may reflect important mechanical aspects of the fault s behavior if this pattern continues into the future the current period of dormancy will probably be greater than two centuries this would mean that the section of the fault represented by the pallett creek site is currently in the middle of one of its longer periods of repose between clusters and sections of the fault farther to the southeast are much more likely to produce the next great earthquake in california the greater precision of dates now available for large earthquakes recorded at the pallett creek site enables speculative correlation of events between paleoseismic sites along the southern half of the san andreas fault a history of great earthquakes with overlapping rupture zones along the mojave section of the fault remains one of the more attractive possibilities

nature of the high speed rupture of the two dimensional burridge knopoff model of earthquakes the nature of the high speed rupture or the main shock of the burridge knopoff spring block model in two dimensions obeying the rate and state dependent friction law is studied by means of extensive computer simulations it is found that the rupture propagation in larger events is highly anisotropic and irregular in shape on longer length scales although the model is completely uniform and the emergent rupture propagation velocity is nearly constant everywhere at the rupture front the manner of the rupture propagation sometimes mimics the successive ruptures of neighbouring asperities observed in real large earthquakes large events tend to be unilateral with its epicentre lying at the rim of its rupture zone the epicentre site of a large event is also located next to the rim of the rupture zone of some past event event size distributions are computed and discussed in comparison with those of the corresponding one dimensional model the magnitude distribution exhibits a power law behaviour resembling the gutenberg richter law for smaller magnitudes which changes over to a more characteristic behaviour for larger magnitudes for very large events the rupture length distribution exhibits mutually different behaviours in one dimension and in two dimensions reflecting the difference in the underlying geometry this article is part of the theme issue statistical physics of fracture and earthquakes

beno gutenberg contribution to seismic hazard assessment and recent progress in the european mediterranean region abstract the fundamental work of beno gutenberg has inspired and guided an appreciable part of research in modern seismology both from the experimental and the theoretical point of view among the several topics of seismology that have benefited from the fundamental contribution of gutenberg we consider particularly relevant the description of the asthenospheric low velocity channel the definition of the surface waves magnitude and the gutenberg richter law since they are pivotal tools for seismic hazard assessment the quite revolutionary model for the lithosphere asthenosphere system in the european area predicts the existence of almost aseismic lithospheric roots these roots are located in correspondence of most of the orogenic belts and interrupt the asthenosphere low velocity channel that has been identified by beno gutenberg in 1948 the model of the european upper mantle proposed for the first time in 1979 and subsequently refined has stimulated a considerable amount of research which has nicely confirmed the major innovative features of the early model at present the subduction of the lithosphere at continent continent collisions supported not only by seismological data is a widely accepted concept within the community of earth scientists even if it contradicts one of the basic dogmas of the original formulation of plate tectonics the proposed model for the alpine apennines area supplies a new and unifying framework for the interpretation of the quaternary magmatism at present generally accepted by petrologists and geochemists the theoretical basis for the gutenberg s surface wave magnitude calibration function has been supplied by the use of complete synthetic seismograms and thus it has been possible to formulate the theoretical m s depth correction the introduction of the depth correction for m s enables the computation of surface wave magnitude for all earthquakes regardless of their focal depth this is especially important for the quantification of subcrustal historical earthquakes for which the seismic moment may be difficult to estimate from recordings of early mechanical seismographs the new m s calibrating function yield both distance and depth independent magnitude estimates the analysis of the global seismicity using the seismotectonic regionalization in subduction zones mid oceanic ridge zones island arcs shows that a single gutenberg richter gr relation is not universally applicable and that a multiscale seismicity model can reconcile two apparently conflicting paradigms the self organized criticality mechanism and the characteristic earthquake concept the multiscale representation has been applied to italy where the zones at the space scale of 400 500 km quite well reproduce the shapes of the regions used to apply the globally tested cn intermediate term earthquake prediction algorithm

fault behavior and characteristic earthquakes examples from the wasatch and san andreas fault zones paleoseismological data for the wasatch and san andreas fault zones have led to the formulation of the characteristic earthquake model which postulates that individual faults and fault segments tend to generate essentially same size or characteristic earthquakes having a relatively narrow range of magnitudes near the maximum analysis of scarp derived colluvium in trench exposures across the wasatch fault provides estimates of the timing and displacement associated with individual surface faulting earthquakes at all of the sites studied the displacement per event has been consistently large measured values range from 1 6 to 2 6 m and the average is about 2 m on the basis of variability in the timing of individual events as well as changes in scarp morphology and fault geometry six major segments are recognized along the wasatch fault on the basis of the most likely number of surface faulting events 18 that have occurred on segments of the wasatch fault zone during the past 8000 years an average recurrence interval of 400 666 years with a preferred average of 444 years is calculated for the entire zone geologic data on the distribution of slip associated with prehistoric earthquakes and slip rates along the south central segment of the san andreas fault suggest that the m 8 1857 earthquake is a characteristic earthquake for this segment comparisons of earthquake recurrence relationships on both the wasatch and san andreas faults based on historical seismicity data and geologic data show that a linear constant b value extrapolation of the cumulative recurrence curve from the smaller magnitudes leads to gross underestimates of the frequency of occurrence of the large or characteristic earthquakes only by assuming a low b value in the moderate magnitude range can the seismicity data on small earthquakes be reconciled with geologic data on large earthquakes the characteristic earthquake appears to be a fundamental aspect of the behavior of the wasatch and san andreas faults and may apply to many other faults as well

multiscale mapping of completeness magnitude of earthquake catalogs we propose a multiscale method to map the spatial variations of the com pleteness magnitude mc of earthquake catalogs the gutenberg richter law describ ing the earthquake frequency magnitude distribution fmd might not hold over the entire magnitude range and small areas may exhibit a specific type of seismicity especially in volcanotectonic contexts for these reasons any scaling relation should be obtained by adapting the dimension of the studied zone to the range of the event magnitude here we associate ranges of larger magnitudes with increasing areas for data selection based on empirical relations in seismotectonics then for each point in space we document the earthquake fmd at all length scales within the corresponding earthquake magnitude ranges high resolution of the mc value is achieved through the determination of the smallest space magnitude scale in which the gutenberg richter law is verified the multiscale procedure isolates the magnitude range that meets the best local seismicity and local record capacity using artificial catalogs and earthquake catalogs of the lesser antilles arc this mc mapping method is shown to be efficient in regions with mixed types of seismicity a variable density of epicenters and various levels of registration

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

statistics of characteristic earthquakes statistical methods are used to test the characteristic earthquake hypothesis several distributions of earthquake size seismic moment frequency relations are described based on the results of other researchers as well as my own tests evidence of the characteristic earthquake hypothesis can be explained either by statistical bias or statistical artifact since other distributions of earthquake size provide a simpler explanation for available information the hypothesis cannot be regarded as proven

aliphatic and aromatic triterpenoid hydrocarbons in a tertiary angiospermous lignite abstract the hydrocarbon biomarker assemlage of a liptinite rich early tertiary angiospermous lignite has been characterized the biomarker fistribution for the lignite confirms the low maturity and previous paleobotanic interpretations the aliphatic hydrocarbon fraction consists predominantly of n alkanes showing a strong odd carbon predominance and numerous de a triterpenoids and triterpenoids derived from higher plants bacterially derived triterpenoids were represented primarily by homohopanes and hopenes the aromatic hydrocarbon fraction contains a series of mono di and triaromatic de a triterpenoids and mono tri and tetraaromatic triterpenoids derived from higher plants the concentration and abundance of monoaromatic triterpenoids containing one to three additonal degress of unsaturation have not seen previously observed in a single deposit as such a diagenetic scheme for angiosperm derived triterpenoids is presented which confirms and extends previous hypothesis

tectonic geomorphology of the san andreas fault zone in the southern indio hills coachella valley california geomorphic investigation of the san andreas fault zone in the indio hills indicates many tectonically produced landforms including beheaded streams right lateral deflected and offset streams sags shutter ridges pressure ridges and fault scarps near biskra palms an alluvial fan pediment complex has an apparent cumulative offset of about 0 7 km along the mission creek fault zone north branch san andreas fault many of the tectonic landforms as well as the fracture pattern that has developed during the pleistocene are explainable by simple shear or uplift associated with a small left bend in the main trace of the mission creek fault the ratio of vertical to horizontal displacement in the vicinity of the bend is about 0 04 exposed in pushawalla canyon 5 km northwest of the alluvial fan pediment complex are 1 a sequence of stream terraces 2 folded plio pleistocene fanglomerates and 3 an example of stream capture following a right lateral deflection or offset of several hundred metres a left step of the mission creek fault in pushawalla canyon is a probably cause of folds and sporadic uplift that produced the stream terraces possible cause of recent stream capture are 1 juxtaposition of pushawalla canyon with a relict canyon moving northwestward along the mission creek fault or 2 right lateral deflection or offset of pushawalla canyon along the fault with simultaneous headward erosion of a shorter steep stream flowing toward the coachella valley estimation of a slip rate and identification of paleoseismicity for the san andreas fault in the indio hills is difficult however degree of topographic dissection formation and preservation of desert pavement and relative soil profile development suggest that the age of the offset fan may be as old as 70 000 yr but that most likely it is on the order of 20 000 to 30 000 yr these age estimates for the offset fan indicate a minimum slip rate for the san andreas fault of 10 to 35 mm yr with about 23 to 35 mm yr the most likely the pattern of observed offset drainages is complex but suggests that during the past few thousand years creep events or moderately large earthquakes have periodically produced several metres of right lateral displacement

behavior of the superstition hills fault during the past 330 years we have investigated the recent prehistoric behavior of the superstition hills fault by examining its effect on the beach deposits of ancient lake cahuilla excavation of these sediments in three dimensions where they are cut by the fault has enabled determination of total offset since the latest highstand of the lake about 330 years ago as of 3 march 1988 total dextral offset was 1106 50 mm about 609 mm of this amount can be attributed to one or more slip events before 1987 the remaining slip occurred during the moderate earthquake of 24 november 1987 and as subsequent aftercreep additional aftercreep here might produce a total of 1210 100 mm for that event thus if afterslip continues according to our prediction slip associated with the penultimate seismic slip event on the superstition hills fault was only about half of the co seismic slip and predicted afterslip associated with the 1987 earthquake this difference established at a single site on the fault may reflect a larger size for the 1987 event than for its predecessor we calculate that the slip rate of the superstition hills fault zone averaged over the past 330 years is between about 2 and at least 6 mm yr at this site during this time the average interval between large surface slip events on the superstition hills fault has been between about 150 and 300 years the pre 1987 slip event documented in our excavations could have occurred at any time between a d 1660 and about a d 1915 these results are significant for understanding earthquake recurrence and patterns of earthquakes in the imperial and coachella valleys

holocene and late pleistocene slip rates on the san andreas fault in yucaipa california using displaced alluvial fan deposits and soil chronology we derived slip rates on the san andreas fault from displacement of alluvial fans and from approximate dating of the fans by the degree of soil development distinctive red purple sedimentary rocks of the miocene potato sandstone exposed on yucaipa ridge in the san bernardino mountains were transported down wilson creek and shed across the modern trace of the san andreas fault soils developed in alluvial fan deposits contain red purple clasts of the potato sandstone and are progressively more developed toward the north west as a result of fault displacement we used soil development to estimate the ages of these alluvial fans and underlying deposits using dated soils from cajon pass and from the central valley of california we estimated ages of wilson creek deposits using a statistical method of maximum likelihood these methods also utilize monte carlo simulations of larger data populations and account for soil variability uncertainty of calibration dates and the limited number of soils described and sampled resulting age estimates have considerable as much as 80 uncertainty resulting largely from quality of calibration dates slip rates for three time intervals were obtained by restoring the medial axis of each displaced fan to wilson creek maximum slip rates were also obtained by restoring the westernmost extent of each fan to wilson creek best estimate rates averaged to the present for 0 to 14 000 yr are 14 to 25 mm yr for 0 to 30 000 yr 22 to 34 mm yr and for 0 to 65 000 or 90 000 yr 12 to 16 mm yr maximum rates averaged to present for 0 to 14 000 yr are as high as 65 mm yr older rates are as high as 80 mm yr when holocene rates are accounted for actual or incremental slip rates for the interval 30 000 to 65 000 or 90 000 yr b p are probably 6 to 13 mm yr these data tentatively suggest that slip rates on the modern trace have increased during the late quaternary uncertainties in slip and age data however allow for rates to have been nearly constant or even decreasing toward the present

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

dilatancy controlled spatiotemporal slip evolution of a sealed fault with spatial variations of the pore pressure summary a range of observations suggest the formation and maintenance of sealed and hence overpressured compartments in fluid infiltrated fault zones it is assumed that hydromechanical properties of regions with variable pore pressure states control the fault s stability and thus its characteristic response that is seismic or aseismic slip accumulation we investigate in a systematic parameter space study the effects of spatial variations in pore pressure on spatiotemporal slip evolution along a hydraulically isolated fault plane the 3 d continuum model is governed by rate and state friction and constitutive laws for porosity reduction we show that the model response is sensitive to the degree of overpressurization and the efficiency of dilatant hardening mechanisms low pore pressures and small dilatancy effects result in unstable response types whereas high pore pressures and large dilatant effects lead to stable and aseismic creep regions with an unstable response are shown to support most of the stresses accumulated during interseismic periods accelerated slip nucleates preferably in regions of low pore pressure statistical properties of model seismicity produce a wide range of event sizes for moderate and large earthquakes in the case where dilatant mechanisms are inefficient in case of efficient slip rate controlled porosity increase less instabilities grow into large earthquakes final slip maps demonstrate the applicability of the chosen method to model seismicity controlled by frictional and hydraulic processes on a planar fault plane the evolution of governing variables that depend on the pore pressure environment provide a conceptual basis for the interpretation of observed response characteristics

lateral offsets and revised dates of large prehistoric earthquakes at pallett creek southern california recent excavation and new radiocarbon dates of sediments at pallett creek are the basis for new conclusions regarding the late holocene history of the san andreas fault systematic dissection of a 50 m long 15 m wide 5 m deep volume of earth centered on the fault enables documentation in three dimensions of fault patterns lateral offsets and vertical deformation associated with large earthquakes of the past the excavations expose evidence for 12 earthquakes that occurred between about 260 and 1857 a d with an average recurrence interval of about 145 years prehistoric slip events that occurred in 1720 50 1550 70 1350 50 1080 65 and 845 75 a d have lateral offsets that are comparable to those of the most recent great earthquake of 1857 thus all of these events represent earthquakes of large magnitude the lateral offsets of two other events in 935 85 and 1015 100 a d are an order of magnitude smaller and may be interpreted in several ways with regard to the size of these events the new data constrain the average recurrence interval for large earthquakes at this site to between 145 and 200 years but suggest a monotonic decrease in individual intervals to below this range during the past 900 years on the basis of these data the probability of a large earthquake with surficial fault rupture at this site is between 0 2 and 5 during 1984 and 7 and 60 by the year 2000