holocene fault scarps near tacoma washington usa airborne laser mapping confirms that holocene active faults traverse the puget sound metropolitan area northwestern continental united states the mapping which detects forest floor relief of as little as 15 cm reveals scarps along geophysical lineaments that separate areas of holocene uplift and subsidence along one such line of scarps we found that a fault warped the ground surface between a d 770 and 1160 this reverse fault which projects through tacoma washington bounds the southern and western sides of the seattle uplift the northern flank of the seattle uplift is bounded by a reverse fault beneath seattle that broke in a d 900 930 observations of tectonic scarps along the tacoma fault demonstrate that active faulting with associated surface rupture and ground motions pose a significant hazard in the puget sound region

serial ruptures of the san andreas fault carrizo plain california revealed by three dimensional excavations 1 it is poorly known if fault slip repeats regularly through many earthquake cycles well documented measurements of successive slips rarely span more than three earthquake cycles in this paper we present evidence of six sequential offsets across the san andreas fault at a site in the carrizo plain using stream channels as piercing lines we opened a latticework of trenches across the offset channels on both sides of the fault to expose their subsurface stratigraphy we can correlate the channels across the fault on the basis of their elevations shapes stratigraphy and ages the three dimensional excavations allow us to locate accurately the offset channel pairs and to determine the amounts of motion for each pair we find that the dextral slips associated with the six events in the last millennium are from oldest to youngest 5 4 0 6 8 0 0 5 1 4 0 5 5 2 0 6 7 6 0 4 and 7 9 0 1 m in this series three and possibly four of the six offset values are between 7 and 8 m the common occurrence of 7 8 m offsets suggests remarkably regular but not strictly uniform slip behavior age constraints for these events at our site combined with previous paleoseismic investigations within a few kilometers allow a construction of offset history and a preliminary evaluation of slip and time predictable models the average slip rate over the span of the past five events between a d 1210 and a d 1857 has been 34 mm yr not resolvably different from the previously determined late holocene slip rate and the modern geodetic strain accumulation rate we find that the slip predictable model is a better fit than the time predictable model in general earthquake slip is positively correlated with the time interval preceding the event smaller offsets coincide with shorter prior intervals and larger offset with longer prior intervals

impact of riser reconstructions on estimation of secular variation in rates of strike slip faulting revisiting the cherchen river site along the altyn tagh fault nw china abstract slip rates are heavily contested for many of the first order strike slip faults within the indo asian collision zone rates determined geodetically are generally lower than those reported using reconstructions of offset landforms and it is unclear if this discrepancy reflects true secular variation in slip history systematic errors in interpretation or both here i examine the methods used to derive slip rates from reconstructions of displaced fluvial risers and show that such rates are subject to potentially important uncertainties that have largely been overlooked review of published data demonstrates that the slip rate can vary by a factor of 1 2 to 5 for the same site depending on whether the reconstruction uses the age of the upper or lower terrace for the initiation of riser offset to reduce this epistemic uncertainty i have developed six geomorphic indices that can be used to identify the most accurate end member reconstruction 1 comparison of riser offset with inset channel width 2 similarity of riser and tread displacements 3 morphological analysis of the scarp profile 4 riser deflection in plan view 5 diachroneity of terrace abandonment and 6 whether riser crests or bases yield the slip vector without the use of these geomorphic observations the epistemic uncertainty associated with current methods for determining slip rate from offset fluvial risers is likely to be so large that there is no resolvable discrepancy between the gps and geologic rates within the indo asian collision zone application of three of these indices to new field mapping of the cherchen he river site 86 4 e along the central altyn tagh fault yields a revised slip rate of 9 4 2 3 mm yr equivalent within error to the rates previously derived from gps and paleoseismic studies although reinterpretation of published data from the sulamu tagh site 87 4 is consistent with this revised rate additional work is needed to reconcile this result with some of the rates reported near aksay 94 e

depth variation of coseismic stress drop explains bimodal earthquake magnitude frequency distribution 1 an essential part of seismic hazard analysis is the earthquake size frequency relationship used to estimate earthquake recurrence time and thus probability a key feature of those distributions is their bimodal character small to moderate magnitude earthquakes follow the gutenberg richter gr inverse power law relation while large magnitude characteristic earthquakes are more frequent than anticipated from gr following approximately a gaussian distribution around the maximum magnitude limited by fault geometry using a numerical earthquake simulator we show that the temperature dependence of friction behavior and therefore the depth variation of coseismic stress drop derived from laboratory friction experiments presents a simple and comprehensive explanation for the observed bimodal seismicity distribution characteristic earthquakes are the result of an abrupt increase in rupture width at the transition from small to large earthquakes

quantifying fault zone activity in arid environments with high resolution topography 1 high resolution airborne laser swath mapping alsm topography illuminates active faulting with unprecedented clarity we contrast alsm topography of two dextral faults in arid regions of california with slip rates that differ by an order of magnitude the lenwood fault with rate of 1 mm yr and the clark fault a strand of the san jacinto fault with net slip rate 10 mm yr visualization of alsm data reveals abundant fault scarps and deflected channels that when reconstructed can yield powerful slip constraints though many of these features may also be detected in existing aerial photography these data are limited by stereo depth resolution and fixed illumination angle

roughness of fault surfaces over nine decades of length scales 1 we report on the topographic roughness measurements of five exhumed faults and thirteen surface earthquake ruptures over a large range of scales from 50 m to 50 km we used three scanner devices lidar laser profilometer white light interferometer spanning complementary scale ranges from 50 m to 10 m to measure the 3 d topography of the same objects i e five exhumed slip surfaces vuache sillingy bolu corona heights dixie valley magnola a consistent geometrical property i e self affinity emerges as the morphology of the slip surfaces shows at first order a linear behavior on a log log plot where axes are fault roughness and spatial length scale covering five decades of length scales the observed fault roughness is scale dependent with an anisotropic self affine behavior described by four parameters two power law exponents h constant among all the faults studied but slightly anisotropic h 0 58 0 07 in the slip direction and h 0 81 0 04 perpendicular to it and two pre factors showing variability over the faults studied for larger scales between 200 m and 50 km we have analyzed the 2 d roughness of the surface rupture of thirteen major continental earthquakes these ruptures show geometrical properties consistent with the slip perpendicular behavior of the smaller scale measurements our analysis suggests that the inherent non alignment between the exposed traces and the along or normal slip direction results in sampling the slip perpendicular geometry although a data gap exists between the scanned fault scarps and rupture traces the measurements are consistent within the error bars with a single geometrical description i e consistent dimensionality over nine decades of length scales

past and future earthquakes on the san andreas fault the san andreas fault in calfornia is one of the best studied earthquake generating faults in the world in their perspective weldon et al discuss recent efforts to construct rupture scenarios that is possible histories of the date location and length of fault rupture of past earthquakes on the fault existing knowledge of the locations and dates of past earthquakes can be explained by different scenarios but the authors argue that the evidence favors the hypothesis that the fault breaks in relatively infrequent large earthquakes they caution that the current 148 year hiatus since the last big earthquake is likely to end within the next 50 years with a large rupture or sequence of ruptures spanning a substantial part of the fault

why the 2002 denali fault rupture propagated onto the totschunda fault implications for fault branching and seismic hazards 1 the propagation of the rupture of the mw7 9 denali fault earthquake from the central denali fault onto the totschunda fault has provided a basis for dynamic models of fault branching in which the angle of the regional or local prestress relative to the orientation of the main fault and branch plays a principal role in determining which fault branch is taken geoearthscope lidar and paleoseismic data allow us to map the structure of the denali totschunda fault intersection and evaluate controls of fault branching from a geological perspective lidar data reveal the denali totschunda fault intersection is structurally simple with the two faults directly connected at the branch point 227 2 km east of the 2002 epicenter the 2002 rupture diverges southeast to become the totschunda fault we use paleoseismic data to propose that differences in the accumulated strain on each fault segment which express differences in the elapsed time since the most recent event was one important control of the branching direction we suggest that data on event history slip rate paleo offsets fault geometry and structure and connectivity especially on high slip rate short recurrence interval faults can be used to assess the likelihood of branching and its direction analysis of the denali totschunda fault intersection has implications for evaluating the potential for a rupture to propagate across other types of fault intersections and for characterizing sources of future large earthquakes

the brittle plastic transition and the depth of seismic faulting a simple rheological model of shearing of the lithosphere that has gained wide acceptance is a two layer model with an upper brittle zone in which deformation takes place by frictional sliding on discrete fault surfaces and a lower plastic zone in which deformation takes place by bulk plastic flow the two are separated by an abrupt brittle plastic transition which is assumed to be indicated by the lower limit of seismicity experimental studies however as well as the deformation structures of mylonites indicate that a broad transitional field of semi brittle behavior lies between these extremes this is a field of mixed mode deformation with a strength that can be expected to be considerably higher than that predicted from the extrapolation of high temperature flow laws for quartzofeldspathic rocks the semi brittle field lies between t1 the onset of quartz plasticity at about 300 c and t2 feldspar plasticity at about 450 c a model is presented in which the transition t1 does not correspond to a transition to bulk flow but to a change from unstable velocity weakening friction to stable velocity strengthening friction t1 thus marks the depth limit of earthquake nucleation but large earthquakes can propagate to a greater depth t3 t3 t2 which corresponds to the lower limit of dynamic frictional behavior in the semi brittle field and approximately to the peak in strength the zone between t1 and t3 is one of alternating behavior with flow occurring m the interseismic period and with co seismic dynamic slip occurring during large earthquakes this zone is characterized by mylonites interlaced by pseudotachylytes and other signs of dynamic faulting the transition t1 is also marked by a change in the generation mechanism of fault rocks from abrasive wear above which produces cataclastites to adhesive wear below which is proposed as an important generation mechanism of mylonites in the upper part of the semi brittle field

a 21 event 4 000 year history of surface ruptures in the anza seismic gap san jacinto fault and implications for long term earthquake production on a major plate boundary fault paleoseismic work completed at hog lake on the san jacinto fault sjf near anza california indicates that at least 21 surface ruptures have occurred in the anza seismic gap over the past 4 000 years the ages of the ruptures are constrained by 111 radiocarbon dates 97 of which fall in stratigraphic order the average recurrence interval for all ruptures for this period is about 185 105 years although some ruptures such as occurred in the april 1918 earthquake caused only minor displacement we rate the expression of each interpreted event in each of the twelve developed field exposures presented in this work by assigning numeric values for the presence of different criteria that indicate rupture to a paleo ground surface weakly expressed ruptures for example the deformation we interpret to be the result of the historical 1918 earthquake received low scores and are interpreted as smaller earthquakes from this analysis we infer that at least fifteen of the identified ruptures are indicative of large earthquakes similar to the penultimate earthquake inferred to be the m w 7 3 22 november 1800 earthquake the adjusted recurrence interval for large earthquakes lengthens to approximately 254 years comparison with the rupture history at the mystic lake paleoseismic site on the claremont strand indicates that it is plausible that several of the large ruptures identified at hog lake could have jumped the hemet step over at mystic lake and continued on the claremont strand or vice versa but most of the event ages do not match between the two sites indicating that most ruptures do not jump the step finally comparison with san andreas fault ruptures both to the north and south of its juncture with the sjf suggest that some northern sjf ruptures identified at mystic lake may correlate with events identified at wrightwood but that these northern ruptures have no match at hog lake and can not indicate rupture of the entire sjf onto the saf

morphologic dating of fault scarps using airborne laser swath mapping alsm data 1 models of fault scarp morphology have been previously used to infer the relative age of different fault scarps in a fault zone using labor intensive ground surveying we present a method for automatically extracting scarp morphologic ages within high resolution digital topography scarp degradation is modeled as a diffusive mass transport process in the across scarp direction the second derivative of the modeled degraded fault scarp was normalized to yield the best fitting in a least squared sense scarp height at each point and the signal to noise ratio identified those areas containing scarp like topography we applied this method to three areas along the san andreas fault and found correspondence between the mapped geometry of the fault and that extracted by our analysis this suggests that the spatial distribution of scarp ages may be revealed by such an analysis allowing the recent temporal development of a fault zone to be imaged along its length

interseismic deformation along the san andreas fault in southern california eight trilateration networks located along the san andreas fault in southern california have been surveyed 8 to 19 times within a 14 to 17 year interval between 1971 and 1992 the data measurements of distances between the same 10 to 32 pairs of geodetic monuments within a network in each of the surveys have been corrected for coseismic offsets from nearby earthquakes calculated from dislocation models the corrected data a total of 2027 measurements are displayed in the form of plots of measured distance versus time for each of the 167 lines measured the hypothesis that the interseismic deformation is steady is tested by examining whether deviations from linear fits to the data in the plots are within the range expected for observational error a significant deviation from steady deformation is found only for the network located neax palmdale california in that network many of the measurements made in the survey of early 1982 deviate from the trend defined by the measurements in other surveys the deviations are not of the form fixed proportional error one would generally expect from systematic survey error if the survey of early 1982 is excluded the remaining data at palmdale are consistent with steady deformation thus the apparent strain event observed near palmdale in 1982 was transient

new empirical relationships among magnitude rupture length rupture width rupture area and surface displacement source parameters for historical earthquakes worldwide are compiled to develop a series of empirical relationships among moment magnitude m surface rupture length subsurface rupture length downdip rupture width rupture area and maximum and average displacement per event the resulting data base is a significant update of previous compilations and includes the additional source parameters of seismic moment moment magnitude subsurface rupture length downdip rupture width and average surface displacement each source parameter is classified as reliable or unreliable based on our evaluation of the accuracy of individual values only the reliable source parameters are used in the final analyses in comparing source parameters we note the following trends 1 generally the length of rupture at the surface is equal to 75 of the subsurface rupture length however the ratio of surface rupture length to subsurface rupture length increases with magnitude 2 the average surface displacement per event is about one half the maximum surface displacement per event and 3 the average subsurface displacement on the fault plane is less than the maximum surface displacement but more than the average surface displacement thus for most earthquakes in this data base slip on the fault plane at seismogenic depths is manifested by similar displacements at the surface log linear regressions between earthquake magnitude and surface rupture length subsurface rupture length and rupture area are especially well correlated showing standard deviations of 0 25 to 0 35 magnitude units most relationships are not statistically different at a 95 significance level as a function of the style of faulting thus we consider the regressions for all slip types to be appropriate for most applications regressions between magnitude and displacement magnitude and rupture width and between displacement and rupture length are less well correlated and have larger standard deviation than regressions between magnitude and length or area the large number of data points in most of these regressions and their statistical stability suggest that they are unlikely to change significantly in response to additional data separating the data according to extensional and compressional tectonic environments neither provides statistically different results nor improves the statistical significance of the regressions regressions for cases in which earthquake magnitude is either the independent or the dependent parameter can be used to estimate maximum earthquake magnitudes both for surface faults and for subsurface seismic sources such as blind faults and to estimate the expected surface displacement along a fault for a given size earthquake

estimating the detachment depth in cross sections involving detachment folds this paper evaluates four different methods that have been proposed for the estimation of the detachment depth beneath detachment folds guidelines are presented in order to use the most suitable method in a particular region deformed by detachment folds these guidelines are constructed considering the assumptions of each method the influence of different parameters on the estimation of the detachment depth folding mechanisms cross sectional area variations position and orientation of the regional datum number of stratigraphic horizons bed length and thickness dip and position of the bounding lines initial thickness of the ductile unit single anticlines or fold trains and the available data ductile unit thickness regional datum detachment depth moreover a new simple method based on two previous methods is presented the advantages of this new method are that the calculations are extremely simple and it uses information from more than one stratigraphic horizon therefore it does not depend strongly on the accuracy of the data at one level the precision of the proposed methods is tested by their application to a number of natural and experimental single anticlines and fold trains it appears that better predictions are obtained when analysing a complete detachment fold train than when dealing with a single detachment anticline the reason might be that ductile material flow beneath the folds along the cross sectional plane is taken into account when dealing with a long enough cross section we also suggest some hypotheses concerning what the shape and dimensions of the detachment folds indicate about the detachment depth in those cases where insufficient data are available to apply the methods proposed

uncertainties in slip rate estimates for the mission creek strand of the southern san andreas fault at biskra palms oasis southern california this study focuses on uncertainties in estimates of the geologic slip rate along the mission creek strand of the southern san andreas fault where it offsets an alluvial fan t2 at biskra palms oasis in southern california we provide new estimates of the amount of fault offset of the t2 fan based on trench excavations and new cosmogenic 10be age determinations from the tops of 12 boulders on the fan surface we present three alternative fan offset models a minimum a maximum and a preferred offset of 660 m 980 m and 770 m respectively we assign an age of between 45 and 54 ka to the t2 fan from the 10be data which is significantly older than previously reported but is consistent with both the degree of soil development associated with this surface and with ages from u series geochronology on pedogenic carbonate from t2 described in a companion paper by fletcher et al this volume these new constraints suggest a range of slip rates between 12 and 22 mm yr with a preferred estimate of 14 17 mm yr for the mission creek strand of the southern san andreas fault previous studies suggested that the geologic and geodetic slip rate estimates at biskra palms differed we find however that considerable uncertainty affects both the geologic and geodetic slip rate estimates such that if a real discrepancy between these rates exists for the southern san andreas fault at biskra palms it cannot be demonstrated with available data

coseismic slip variation assessed from terrestrial lidar scans of the el mayor cucapah surface rupture abstract we analyze high resolution 103 points m2 terrestrial lidar surveys of the 4 april 2010 el mayor cucapah earthquake rupture baja california mexico collected at three sites 12 18 days after the event using point cloud based tools in an immersive visualization environment we quantify coseismic fault slip for hundreds of meters along strike and construct densely constrained along strike slip distributions from measurements of offset landforms uncertainty bounds for each offset determined empirically by repeatedly measuring offsets at each site sequentially illuminate measurement uncertainties that are difficult to quantify in the field these uncertainties are used to define length scales over which variability in slip distributions may be assumed to reflect either recognizable earthquake mechanisms or measurement noise at two sites characterized by 2 3 m of concentrated right oblique slip repeat measurements yield 2 uncertainties of 11 12 each site encompasses 200 m along strike and a smoothed linear slip gradient satisfies all measurement distributions implying along fault strains of 10 3 conversely the common practice of defining the slip curve by the local slip maxima distorts the curve overestimates along fault strain and may overestimate actual fault slip by favoring measurements with large positive uncertainties at a third site characterized by 1 2 5 m of diffuse normal slip repeat measurements of fault throw summed along fault perpendicular profiles yield 2 uncertainties of 17 here a low order polynomial fit through the measurement averages best approximates surface slip however independent measurements of off fault strain accommodated by hanging wall flexure suggest that over the 200 m length of this site a linear interpolation through the average values for the slip maxima at either end of this site most accurately represents subsurface displacement in aggregate these datasets show that given uncertainties of greater than 11 2 slip distributions over shorter scales are likely to be less uneven than those derived from a single set of field or lidar based measurements this suggests that the relatively smooth slip curves we obtain over 102 m distances reflect real physical phenomena whereas short wavelength variability over 100 101 m distances can be attributed to measurement uncertainty

fault slip and earthquake recurrence along strike slip faults contributions of high resolution geomorphic data article i nfo understanding earthquake eq recurrence relies on information about the timing and size of past eq ruptures along a given fault knowledge of a fault s rupture history provides valuable information on its potential future behavior enabling seismic hazard estimates and loss mitigation stratigraphic and geomorphic evidence of faulting is used to constrain the recurrence of surface rupturing eqs analysis of the latter data sets culminated during the mid 1980s in the formulation of now classical eq recurrence models now routinely used to assess seismic hazard within the last decade light detection and ranging lidar surveying technology and other high resolution data sets became increasingly available to tectono geomorphic studies promising to contribute to better informed models of eq recurrence and slip accumulation patterns after reviewing motivation and background we outline requirements to successfully reconstruct a fault s offset accumulation pattern from geomorphic evidence we address sources of uncertainty affecting offset measure ment and advocate approaches to minimize them a number of recent studies focus on single eq slip distribu tions and along fault slip accumulation patterns we put them in context with paleoseismic studies along the respective faults by comparing coefficients of variation cv for eq inter event time and slip per event and find that a single event offsets vary over a wide range of length scales and the sources for offset variability differ with length scale b at fault segment length scales single event offsets are essentially constant c along fault offset accumulation as resolved in the geomorphic record is dominated by essentially same size large offset in crements and d there is generally no one to one correlation between the offset accumulation pattern constrained in the geomorphic record and eq occurrence as identified in the stratigraphic record revealing the higher resolution and preservation potential of the latter while slip accumulation along a fault segment may be dominated by repetition of large nearly constant offset increments timing of surface rupture is less regular

near field deformation from the el mayor cucapah earthquake revealed by differential lidar large moment magnitude m w 7 continental earthquakes often generate complex multifault ruptures linked by enigmatic zones of distributed deformation here we report the collection and results of a high resolution nine returns per square meter airborne light detection and ranging lidar topographic survey of the 2010 m w 7 2 el mayor cucapah earthquake that produced a 120 kilometer long multifault rupture through northernmost baja california mexico this differential lidar survey completely captures an earthquake surface rupture in a sparsely vegetated region with pre earthquake lower resolution 5 meter pixel lidar data the postevent survey reveals numerous surface ruptures including previously undocumented blind faults within thick sediments of the colorado river delta differential elevation changes show distributed kilometer scale bending strains as large as 10 3 microstrains in response to slip along discontinuous faults cutting crystalline bedrock of the sierra cucapah

developing sub 5 m lidar dems for forested sections of the alpine and hope faults south island new zealand implications for structural interpretations abstract kilometre wide airborne light detection and ranging lidar surveys were collected along portions of the alpine and hope faults in new zealand to assess the potential for generating sub 5 m bare earth digital elevation models dems from ground return data in areas of dense rainforest bush cover as an aid to mapping these faults the 34 km long franz whataroa lidar survey was flown along the densely vegetated central most portion of the transpressive alpine fault six closely spaced flight lines 200 m apart yielded survey coverage with double overlap of swath collection which was considered necessary due to the low density of ground returns 0 16 m 2 or a point every 6 m2 under mature west coast podocarp broadleaf rainforest this average point spacing 2 5 m allowed for the generation of a robust high quality 3 m bare earth dem the dem confirmed the zigzagged form of the surface trace of the alpine fault in this area originally recognised by norris and cooper 1995 norris and cooper 1997 and highlights that the surface strike variations are more variant than previously mapped the 29 km long hurunui hope lidar survey was flown east of the main divide of the southern alps along the dextral slip hope fault where the terrain is characterised by lower rainfall and more open beech forest flight line spacings of 275 m were used to generate a dem from the ground return data the average ground return values under beech forest were 0 27 m 2 and yielded an estimated cell size suitable for a 2 m dem in both cases the lidar revealed unprecedented views of the surface geomorphology of these active faults lessons learned from our survey methodologies can be employed to plan cost effective high gain airborne surveys to yield bare earth dems underneath vegetated terrain and multi storeyed canopies from densely forested environments across new zealand and worldwide

stratigraphic evidence for seven meters of dextral slip on the san andreas fault during the 1857 earthquake in the carrizo plain the smallest geomorphic offsets along a 35 km section of the san andreas fault in the carrizo plain vary from 7 to 10 m our three dimensional excavation of alluvial deposits a few km southeast of wallace creek confirms that at least 6 6 to 6 9 m of dextral slip occurred there during the latest large earthquake in 1857 dates on detrital charcoal suggest that the last event prior to the 1857 earthquake occurred before a date within the range a d 1305 to 1623 the 3 m range in smallest offsets along this portion of the fault may reflect either a 3 m variation in slip along the san andreas in 1857 or 2 to 3 m of slip during an event prior to 1857 observations made after the recent landers earthquake are compatible with the hypothesis of large local variations in slip during a single earthquake but do not explain the cause of such variations off fault dextral rotations would be one plausible explanation however paleoseismic data in the carrizo plain are too sparse to allow rejection of the alternative hypothesis that slip in the event prior to 1857 was only 2 to 3 m an amount of slip which would be several times too small to fit a time predictable model

superficial simplicity of the 2010 el mayor cucapah earthquake of baja california in mexico the geometry of faults is usually thought to be more complicated at the surface than at depth and to control the initiation propagation and arrest of seismic ruptures the fault system that runs from southern california into mexico is a simple strike slip boundary the west side of california and mexico moves northwards with respect to the east however the m w 7 2 2010 el mayor cucapah earthquake on this fault system produced a pattern of seismic waves that indicates a far more complex source than slip on a planar strike slip fault here we use geodetic remote sensing and seismological data to reconstruct the fault geometry and history of slip during this earthquake we find that the earthquake produced a straight 120 km long fault trace that cut through the cucapah mountain range and across the colorado river delta however at depth the fault is made up of two different segments connected by a small extensional fault both segments strike n130 e but dip in opposite directions the earthquake was initiated on the connecting extensional fault and 15 s later ruptured the two main segments with dominantly strike slip motion we show that complexities in the fault geometry at depth explain well the complex pattern of radiated seismic waves we conclude that the location and detailed characteristics of the earthquake could not have been anticipated on the basis of observations of surface geology alone

relation between continental strike slip earthquake segmentation and thickness of the crust 1 high resolution maps of large continental strike slip earthquake surface ruptures show that they are formed of fault segments these segments are bounded by fault bends step overs or combinations of the two the lowest limit in size for such segments may not be relevant in the understanding of earthquake mechanics as it pertains to the granular properties of fault zones the maximum limit in segment length however is important as it is directly relates to the maximum extent of seismic rupture to measure the length of the segments a new quantitative method based on piecewise linear fitting is developed and is used to automatically retrieve segments from earthquake rupture maps next this approach is tested against a set of ten continental strike slip earthquake ruptures derived from similar high quality maps the test suggests that segments have a maximum length of 18 km independent of regional tectonic setting slip inversions for earthquakes based on seismological and or geodetic data most often are not unique and can show some variability even for one particular event some basic characteristics however such as total moment release or general source geometry seem to persist that are relevant to earthquake mechanics measurements of the maximum horizontal extent of individual slip patches derived from seismic source inversion for strike slip ruptures show that their strike dimension does not increase infinitely with magnitude but instead reaches a maximum value of 25 km these two independent lines of observations complemented by earlier data and analog experiments suggest that it is the thickness of the seismogenic crust that controls the structural scaling of the length of seismic segments and that it is independent of the ultimate size of individual earthquakes

constitutive behavior and stability of frictional sliding of granite an understanding of the frictional sliding on faults that can lead to earthquakes requires a knowledge of both constitutive behavior of the sliding surfaces and its mechanical interaction with the loading system we have determined the constitutive parameters for frictional sliding of initially bare surfaces of westerly granite using a recently developed high pressure rotary shear apparatus that allows long distances of sliding and therefore a greater assurance of attaining steady state behavior from experiments conducted at room temperature and normal stresses of 27 84 mpa several important results have been found 1 a gouge layer 100 to 200 m thick was developed from the initially bare rock surfaces after 18 to 70 mm of sliding 2 the steady state frictional resistance attained after about 10 mm of sliding is proportional to the negative of the logarithm of the sliding velocity 3 abrup changes in the velocity of sliding result in initial changes in the frictional resistance which have the same sign as the velocity change and are followed by a gradual decay to a new steady state value over a characteristic distance of sliding this velocity weakening behavior is essentially identical with that found by several previous workers on the same material at lower normal stress 4 our results are well described by a two state variable constitutive law the values of the constitutive parameters are quite similar to those found previously at low normal stress but the characteristic distance is about an order of magnitude smaller than that found at 10 mpa normal stress with thicker layers of coarser gouge 5 we have approximated our results with a one state variable constitutive law and compared the results with the predictions of existing nonlinear stability analysis in addition we have extended the stability analysis to systems possessing two state variables with such formulations good agreement is found between the experimentally observed and theoretically predicted transitions between stable and unstable sliding these results allow a better understanding of the instabilities that lead to earthquakes

tectonic geomorphology of the san andreas fault zone from high resolution topography an example from the cholame segment abstract high resolution topographic data along fault zones are important aids in the delineation of recently active breaks a 15 km long portion of the south central san andreas fault saf along the southern cholame segment contains well preserved tectonic landforms such as benches troughs scarps and aligned ridges that indicate recurring earthquake slip recently acquired lidar topographic data along the entire southern saf b4 project have shot densities of 3 4 m 2 computed from the lidar returns digital elevation models dems of 0 25 to 0 5 m resolution using local binning with inverse distance weighting and 0 8 m or larger search radii depict the tectonic landforms at paleoseismic sites well enough to assess them confidently mapping of recently active breaks using a lidar only based approach compares well with aerial photographic and field based methods the fault zone varies in width from meters to nearly 1 km and is comprised of numerous en echelon meter to kilometer length overlapping sub parallel fault surfaces bounding differentially moving blocks that elongate parallel to the saf the semantic variations of what constitutes active and the importance of secondary traces influence the breadth and complexity of the resulting fault trace maps

three dimensional surface displacements and rotations from differencing pre and post earthquake lidar point clouds 1 the recent explosion in sub meter resolution airborne lidar data raises the possibility of mapping detailed changes to earth s topography we present a new method that determines three dimensional 3 d coseismic surface displacements and rotations from differencing pre and post earthquake airborne lidar point clouds using the iterative closest point icp algorithm tested on simulated earthquake displacements added to real lidar data along the san andreas fault the method reproduces the input deformation for a grid size of 50 m with horizontal and vertical accuracies of 20 cm and 4 cm values that mimic errors in the original spot height measurements the technique also measures rotations directly resolving the detailed kinematics of distributed zones of faulting where block rotations are common by capturing near fault deformation in 3 d the method offers new constraints on shallow fault slip and rupture zone deformation in turn aiding research into fault zone rheology and long term earthquake repeatability

slip in the 1857 and earlier large earthquakes along the carrizo plain san andreas fault the moment magnitude mw 7 9 fort tejon earthquake of 1857 with a 350 kilometer long surface rupture was the most recent major earthquake along the south central san andreas fault california based on previous measurements of its surface slip distribution rupture along the 60 kilometer long carrizo segment was thought to control the recurrence of 1857 like earthquakes new high resolution topographic data show that the average slip along the carrizo segment during the 1857 event was 5 3 1 4 meters eliminating the core assumption for a linkage between carrizo segment rupture and recurrence of major earthquakes along the south central san andreas fault earthquake slip along the carrizo segment may recur in earthquake clusters with cumulative slip of 5 meters

evidence for an earthquake barrier model from mw 7 8 kokoxili tibet earthquake slip distribution abstract the slip distribution of the mw 7 8 kokoxili tibet 2001 earthquake has been measured at high resolution using optical correlation of satellite images and provides both the parallel and perpendicular components of the horizontal co seismic slip this reveals a variation of the horizontal slip at a scale of 20 km along strike anti correlation of slip parallel and perpendicular to the fault indicates transfer of slip from the horizontal to the vertical component at the ends of segments these features suggest a rupture model with segments separated by strong persistent geometric barriers the unexpected ending of the rupture south of the main fault can be explain by such a structure but bears important implications for the initiation and rupture directivity of the next earthquake

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

variability of displacement at a point implications for earthquake size distribution and rupture hazard on faults abstract to investigate the nature of earthquake magnitude distributions on faults we compare the interevent variability of surface displacement at a point on a fault from a composite global data set of paleoseismic observations with the variability expected from two prevailing magnitude frequency distributions the truncated exponential model and the characteristic earthquake model we use forward modeling to predict the coefficient of variation cv for the alternative earthquake distributions incorporating factors that would effect observations of displacement at a site the characteristic earthquake model with a characteristic magnitude range of 0 25 produces cv values consistent with the data cv 0 5 only if the variability for a given earthquake magnitude is small this condition implies that rupture patterns on a fault are stable in keeping with the concept behind the model this constraint also bears upon fault rupture hazard analysis which for lack of point specific information has used global scaling relations to infer variability in average displacement for a given size earthquake exponential distributions of earthquakes from m 5 to the maximum magnitude give rise to cv values that are significantly larger than the empirical constraint a version of the model truncated at m 7 however yields values consistent with a larger cv 0 6 determined for small displacement sites although this result allows for a difference in the magnitude distribution of smaller surface rupturing earthquakes it may reflect in part less stability in the displacement profile of smaller ruptures and or the tails of larger ruptures online material global surface displacement data and identified sources of uncertainty

147 sm 143 nd and 176 lu 176 hf systematics of eucrite and angrite meteorites comparative planetary geochemistry provides insight into the origin and evolutionary paths of planetary bodies in the inner solar system the eucrite and angrite achondrite groups are particularly interesting because they show evidence of early planetary differentiation we present 147sm 143nd and 176lu 176hf analyses of eight noncumulate basaltic eucrites two cumulate eucrites and three angrites which together place new constraints on the evolution and differentiation histories of the crusts of the eucrite and angrite parent bodies and their mantle mineralogies the chemical compositions of both eucrites and angrites indicate similar evolutionary paths and petrogenetic models with formation and isolation of differentiated crustal reservoirs associated with segregation of ilmenite we report a 147sm 143nd mineral isochron age for the moama cumulate eucrite of 4519 34 ma mswd 1 3 this age indicates protracted magmatism within deep crustal layers of the eucrite parent body lasting up to about 50 ma after the formation of the solar system we further demonstrate that the isotopic compositions of constituent minerals are compromised by secondary processes hindering precise determination of mineral isochron ages of basaltic eucrites and angrites we interpret the changes in geochemistry and consequently the erroneous 147sm 143nd and 176lu 176hf internal mineral isochron ages of basaltic eucrites and angrites as the result of metamorphic events such as impacts effects from pressure temperature and peak shock duration on the surfaces of the eucrite and angrite parent bodies

evolution of stress in southern california for the past 200 years from coseismic postseismic and interseismic stress changes summary the seismicity of southern california results from stresses that arise from the relative motion of the pacific and north american plates being accommodated along the san andreas fault saf system and the eastern california shear zone ecsz here we calculate how the stress field in southern california has evolved over the past two centuries due to interseismic loading as inferred from current gps observations of surface velocities from redistributions of static stress induced by large m w 6 5 earthquakes since the 1812 wrightwood quake and postseismic viscoelastic relaxation associated with these events that serves to transfer coseismic stresses from the deep warm lower crust and upper mantle to the overlying seismogenic upper crust we calculate coulomb stress changes on vertical strike slip faults striking parallel to the saf and at the hypocenters on the rupture planes of all m w 6 events over the past two centuries our results suggest that the 1857 m w 8 2 fort tejon earthquake by far the largest event to have occurred in the region over the past two centuries had a profound influence on the state of stress in southern california during the 19th century inducing significant stress increases to the north parkfield region and adjoining creeping saf and south southern saf and san jacinto fault and stress relief across the southern ecsz these stress changes were then greatly magnified by postseismic relaxation through the early part of the 20th century slow interseismic build up of stress further loads all major strike slip faults and works to reload the areas of the ecsz where stress was relieved by the 1857 quake our calculations suggest that only 56 of hypocenters were pushed closer to failure by preceding coseismic stress changes suggesting that the occurrence of large earthquakes is not strongly determined by coseismic coulomb stress changes this percentage rises to 70 when postseismic stress changes are also considered our calculations demonstrate the importance of postseismic viscoelastic relaxation in the redistribution of stress following large earthquakes we find however that postseismic processes associated with events more than about a decade old are near completion and thus do not significantly influence the regional velocity field presently observed in southern california

reevaluation of surface rupture parameters and faulting segmentation of the 2001 kunlunshan earthquake mw7 8 northern tibetan plateau china the 14 november 2001 m w 7 8 kunlunshan earthquake ruptured the westernmost part of the kunlun fault northern tibetan plateau the main segment affected by this event was the kusaihu segment field investigations allowed us to constrain the length the width and the coseismic horizontal displacement distribution of the kunlunshan earthquake rupture zone the mapped surface rupture zone starts from 90 257 e in the west and ends at 94 795 e in the east with a total length of 426 km it consists of three main sections the western strike slip section the transtensional section and the eastern strike slip section the rupture zone is oriented n100 10 e on average the distribution of the coseismic horizontal displacements is characterized by multiple peaks departing clearly from a general bell shaped distribution reassessment of the maximum coseismic horizontal left lateral displacement yields a value of 7 6 0 4 m at the site 35 767 n 93 323 e consistent with independent measurements derived from interferometric synthetic aperture radar and seismology from this site the horizontal displacement decreases unevenly to both the west and east coseismic vertical reverse displacement is also noted at the eastern end of the rupture but it remains much smaller than the horizontal component the width of the rupture zone varies from site to site from several meters to few kilometers the maximum width measured reaches 8 km along the yuxi feng subsection where a large number of shaking related cracks were well developed

slip in the 2010 2011 canterbury earthquakes new zealand the 3rd september 2010 mw 7 1 darfield and 21st february 2011 mw 6 3 christchurch new zealand earthquakes occurred on previously unknown faults we use insar ground displacements sar amplitude offsets field mapping aerial photographs satellite optical imagery a lidar dem and teleseismic body wave modeling to constrain the pattern of faulting in these earthquakes the insar measurements reveal slip on multiple strike slip segments and secondary reverse faults associated with the darfield main shock fault orientations are consistent with those expected from the gps derived strain field the insar line of sight displacement field indicates the main fault rupture is about 45 km long and is confined largely to the upper 10 km of the crust slip on the individual fault segments of up to 8 m at 4 km depth indicate stress drops of 6 10 mpa in each event rupture initiated on a reverse fault segment before continuing onto a strike slip segment the non double couple seismological moment tensors for each event are matched well by the sum of double couple equivalent moment tensors for fault slip determined by insar the slip distributions derived from insar observations of both the darfield and christchurch events show a 15 km long gap in fault slip south west of christchurch which may present a continuing seismic hazard if a further unknown fault structure of significant size should exist there

concealed quaternary strike slip fault resolved with airborne lidar and seismic reflection the grizzly valley fault system northern walker lane california 1 the grizzly valley fault system gvfs strikes northwestward across sierra valley a low relief basin situated within a network of active dextral slip faults in the northern walker lane california quaternary motion along the grizzly valley fault system has not been previously documented we used high resolution 0 25 m airborne lidar data in combination with high resolution p wave seismic reflection imaging to evaluate quaternary deformation associated with the gvfs we identified suspected tectonic lineaments using the lidar data and collected seismic reflection data along six profiles across the lineaments the seismic reflection images reveal a deformed basal marker that we interpret to be the top of tertiary volcanic rocks overlain by a 120 450 m thick suite of subhorizontal reflectors that we interpret to be plio pleistocene lacustrine deposits three profiles image features that we interpret to be the principal active trace of the gvfs which is a steeply dipping fault zone that vertically offsets the volcanic rocks and the lacustrine basin fill these data suggest that the gvfs may have been active in latest quaternary time because 1 the lidar data show subtle surficial geomorphic features that are typical of youthful faulting including a topographic lineament marked by an 1 m high ridge composed of discontinuous left stepping lobes and 2 the seismic profiles demonstrate shallow faulting of the lacustrine strata that coincides with the left stepping ridge this investigation illustrates the potential for unidentified low rate strike slip faults in basins and emphasizes the value of high resolution topographic data and subsurface imaging as a means of identifying these structures

1857 slip on the san andreas fault southeast of cholame california sieh and jahns 1984 forecasted that the next moderate parkfield earthquake might trigger a major earthquake along a fault segment greater than 30 km long southeast of cholame their forecast assumed 1 the slip was 3 4 m in 1857 and characteristic of the segment 2 a slip rate of 3 4 cm yr and 3 full strain release in earthquakes this study represents an independent measurement of channel offsets on 1 2400 scale low sun aerial photographs and by field investigation to estimate the amount of 1857 slip although rainfall is only moderate 30 cm yr few reliable offsets of less than 20 m persist here because cattle grazing and agricultural disking of soft sediments on the steep terrain greatly aggravate erosion reconstruction of offset geometry and size depends heavily on assumptions made about the post 1857 erosion most of the apparent 3 to 4 m offsets of sieh and jahns 1984 can also be measured as 2 to 3 m larger with equal or lower uncertainty the four offsets judged as most reliable range between 5 4 and 6 7 m and the 11 offsets of medium high reliability average 5 8 0 3 m data are too sparse and ambiguous to resolve details of the 1857 slip for this segment but it is distinctly less than the 9 m of the carrizo plain and more than the 3 4 m previously estimated further trenching may refine some measurements but probability calculations for a cholame segment earthquake must allow for large observer dependent uncertainty in the 1857 slip although the probability of an m 7 cholame event seems less than that suggested by a 3 5 m characteristic earthquake model it remains among the highest in the state

finding the buried record of past earthquakes with gpr based palaeoseismology a case study on the hope fault new zealand in places where sedimentation and erosion compete at fast rates part of the record of past earthquakes on faults may be buried hence hidden in the first few metres below the surface we developed a novel form of palaeoseismology of geophysical type based on the use of a dense pseudo 3 d ground penetrating radar gpr survey to investigate such possible buried earthquake traces on a long fast slipping strike slip fault hope fault new zealand at a site terako where marked alluvial conditions prevail we first used lidar data to analyse the ground surface morphology of the 2 km2 site at the greatest resolution nineteen morphological markers were observed mainly alluvial terrace risers and small stream channels that are all dextrally offset by the fault by amounts ranging between 3 and 200 m the measurements document about 10 past earthquake slip events with a mean coseismic slip of 3 3 1 m with the most recent earthquake event having a slip of 3 0 5 m we then investigated a detailed area of the site 400 x 600 m2 with pseudo 3 d gpr we measured 56 similar to 400 m long 510 m spaced gpr profiles 250 mhz parallel to the fault and evenly distributed on either side the analysis revealed the existence of a palaeosurface buried at about 3 m depth corresponding to the top of alluvial terraces of different ages that buried surface is incised by a dense network of stream channels that are all dextrally offset by the fault we measured 48 lateral offsets in the buried channel network more than twice than at the surface these offsets range between 6 and 108 m as observed at the surface yet provide a more continuous record of the fault slip the similarity of the successive slip increments suggests a slip per event averaging 4 4 1 m fairly similar to that estimated from surface data from the total surface and buried 67 offset collection we infer that a minimum of 30 large earthquakes have broken the hope fault at the terako site in the last about 67 kyr with an average coseismic slip of 3 2 1 m a minimum average recurrence time of about 200 yr and a magnitude of at least mw 7 07 4 our study therefore confirms that part of the record of past earthquakes may indeed reside in the first few metres below the surface where it may be explored with geophysical gpr based palaeoseismology developing such a new palaeoseismological tool should provide rich information that may complement surface observations and help to document the past earthquakes on faults

fault stability inferred from granite sliding experiments at hydrothermal conditions seismicity on crustal faults is concentrated in the depth interval 1 3 to 12 15km tse and rice 1986 suggested that the lower bound on seismicity is due to a switch with increasing temperature from velocity weakening destabilizing to velocity strengthening stabilizing friction they inferred this transition from friction data for dry granite however pore fluids exist at elevated temperatures throughout the crust and may strongly influence strength and sliding behavior we present new data from sliding experiments on granite at elevated t 23 to 600 plus elevated ph2o 100 mpa our results show velocity strengthening at room temperature but velocity weakening from 100 to 350 c except at 250 from 350 to 600 there are systematic trends from velocity weakening to strong velocity strengthening and from high to low friction neither trend was seen in tests on dry granite the velocity dependence data imply the potential for unstable slip in the interval 100 to 350 using a geotherm to map temperature to depth this interval closely matches the observed earthquake distribution

coseismic fault zone deformation revealed with differential lidar examples from japanese mw 7 intraplate earthquakes abstract we use two recent japanese earthquakes to demonstrate the rich potential as well as some of the challenges of differencing repeat airborne light detection and ranging lidar topographic data to measure coseismic fault zone deformation we focus on densely vegetated sections of the 14 june 2008 iwate miyagi m w 6 9 and 11 april 2011 fukushima hamadori m w 7 1 earthquake ruptures each covered by 2 m resolution pre event and 1 m resolution post event bare earth digital terrain models dtms obtained from commercial lidar providers three dimensional displacements and rotations were extracted from these datasets using an adaptation of the iterative closest point icp algorithm these displacements remain coherent close to surface fault breaks as well as within dense forest despite intervals of 2 years iwate miyagi and 4 years fukushima hamadori encompassed by the lidar scenes differential lidar analysis is thus complementary to interferometric synthetic aperture radar insar and sub pixel correlation techniques which often break down under conditions of long time intervals dense vegetation or steep displacement gradients although the icp displacements are much noisier than overlapping insar line of sight displacements they still provide powerful constraints on near surface fault slip in the fukushima hamadori case near fault displacements and rotations are consistent with decreased primary fault slip at very shallow depths of a few tens of meters helping to account for the large along strike heterogeneity in surface offsets observed in the field this displacement field also captures long wavelength deformation resulting from the 11 march 2011 tohoku great earthquake

strain accumulation across the carrizo segment of the san andreas fault california impact of laterally varying crustal properties 1 major strike slip faults juxtapose geologically dissimilar terrain which may vary in mechanical properties leading to an asymmetric pattern of strain accumulation we present new gps data on the carrizo segment of the san andreas fault separating the salinian block southwest of the fault from franciscan terrane northeast of the fault to better quantify asymmetric strain accumulation we also present a series of finite element models to investigate the possible role of variable elastic layer thickness and material properties of the upper crust the geodetic data are well fit with a simple model comprising a weak upper crustal zone 10 25 km wide northeast of the fault this model is also consistent with geologic data on the distribution of major rock types and corresponding laboratory data on their material properties as well as paleoseismic seismic and magnetotelluric data using this model we estimate a long term average over several seismic cycles slip rate for the san andreas fault of 36 1 5 2 mm yr in agreement with the known holocene rate within uncertainties and a viscosity for the combined lower crust upper mantle of 2 5 1019 pa s

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

lidar and field observations of slip distribution for the most recent surface ruptures along the central san jacinto fault we measured offsets on tectonically displaced geomorphic features along 80 km of the clark strand of the san jacinto fault sjf to estimate slip per event for the past several surface ruptures we identify 168 offset features from which we make over 490 measurements using b4 light detection and ranging lidar imagery and field observations our results suggest that lidar technology is an exemplary supplement to traditional field methods in slip per event studies displacement estimates indicate that the most recent surface rupturing event mre produced an average of 2 5 2 9 m of right lateral slip with maximum slip of nearly 4 m at anza a m w 7 2 7 5 earthquake average multiple event offsets for the same 80 kms are 5 5 m with maximum values of 3 m at anza for the penultimate event cumulative displacements of 9 10 m through anza suggest the third event was also similar in size paleoseismic work at hog lake dates the most recent surface rupture event at ca 1790 a poorly located large earthquake occurred in southern california on 22 november 1800 we relocate this event to the clark fault based on the mre at hog lake we also recognize the occurrence of a younger rupture along 15 20 km of the fault in blackburn canyon with 1 25 m of average displacement we attribute these offsets to the 21 april 1918 m w 6 9 event these data argue that much or all of the clark fault and possibly also the casa loma fault fail together in large earthquakes but that shorter sections may fail in smaller events online material topographic contour maps and hillshades generated from b4 lidar data corresponding field photographs and data tables comparing lidar based and field based slip measurements for individual geomorphic features along the clark fault

airborne lidar analysis and geochronology of faulted glacial moraines in the tahoe sierra frontal fault zone reveal substantial seismic hazards in the lake tahoe region california nevada usa we integrated high resolution bare earth airborne light detection and ranging lidar imagery with field observations and modern geochronology to characterize the tahoe sierra frontal fault zone which forms the neotectonic boundary between the sierra nevada and the basin and range province west of lake tahoe the lidar imagery clearly delineates active normal faults that have displaced late pleistocene glacial moraines and holocene alluvium along 30 km of linear right stepping range front of the tahoe sierra frontal fault zone herein we illustrate and describe the tectonic geomorphology of faulted lateral moraines we have developed new three dimensional modeling techniques that utilize the high resolution lidar data to determine tectonic displacements of moraine crests and alluvium the statistically robust displacement models combined with new ages of the displaced tioga 20 8 1 4 ka and tahoe 69 2 4 8 ka 73 2 8 7 ka moraines are used to estimate the minimum vertical separation rate at 17 sites along the tahoe sierra frontal fault zone near the northern end of the study area the minimum vertical separation rate is 1 5 0 4 mm yr which represents a two to threefold increase in estimates of seismic moment for the lake tahoe basin from this study we conclude that potential earthquake moment magnitudes m w range from 6 3 0 25 to 6 9 0 25 a close spatial association of landslides and active faults suggests that landslides have been seismically triggered our study underscores that the tahoe sierra frontal fault zone poses substantial seismic and landslide hazards

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

paleoearthquakes at frazier mountain california delimit extent and frequency of past san andreas fault ruptures along 1857 trace large earthquakes are infrequent along a single fault and therefore historic well characterized earthquakes exert a strong influence on fault behavior models this is true of the 1857 fort tejon earthquake estimated m7 7 7 9 on the southern san andreas fault ssaf but an outstanding question is whether the 330 km long rupture was typical new paleoseismic data for six to seven ground rupturing earthquakes on the big bend of the ssaf restrict the pattern of possible ruptures on the 1857 stretch of the fault in conjunction with existing sites we show that over the last 650 years at least 75 of the surface ruptures are shorter than the 1857 earthquake with estimated rupture lengths of 100 to 300 km these results suggest that the 1857 rupture was unusual perhaps leading to the long open interval and that a return to pre 1857 behavior would increase the rate of m7 3 m7 7 earthquakes

surficial slip distribution on the central emerson fault during the june 28 1992 landers earthquake california we present the results of our mapping of a 5 6 km length of the central emerson fault that ruptured during the 1992 landers earthquake in the southwestern mojave desert california the right lateral slip along this portion of the rupture varied from about 150 to 530 cm along the main rupture zone in some locations a total of up to 110 cm of additional right lateral slip occurred on secondary faults up to 1 7 km away from the main rupture zone other secondary faults carried up to several tens of centimeters of left lateral or thrust displacement the maximum net vertical displacement was 175 cm east side up the sense of vertical slip across the main fault zone varied along strike but in most cases it was consistent with the sense of vertical slip in previous earthquakes as indicated by the locations of areas of older uplifted and abandoned alluvial fan surfaces although variations in surficial slip have been reported along previous strike slip ruptures our closely spaced slip measurements allow a much more detailed study of slip variability than was possible previously we document variations in slip as large as 1 m or more over distances ranging from 1 2 km to a few tens of meters suggesting that strains of the order of 10 1 may have occurred locally within the surficial sediments the long wavelength kilometer scale variations in surficial slip may be influenced by fault geometry and perhaps by the thickness of unconsolidated sediments the slip variations over shorter length scales tens of meters may be caused by variations in the proportion of the total shear that occurs on visible brittle fractures versus that which occurs as distributed shear warping or rotation the variability of slip along the ruptures associated with the landers earthquake calls for caution in interpreting geomorphic offsets along prehistoric fault ruptures

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

paleoseismic event dating and the conditional probability of large earthquakes on the southern san andreas fault california we introduce a quantitative approach to paleoearthquake dating and apply it to paleoseismic data from the wrightwood and pallett creek sites on the southern san andreas fault we illustrate how stratigraphic ordering sedimentolog ical and historical data can be used quantitatively in the process of estimating earth quake ages calibrated radiocarbon age distributions are used directly from layer dating through recurrence intervals and recurrence probability estimation the method does not eliminate subjective judgements in event dating but it does provide a means of systematically and objectively approaching the dating process date dis tributions for the most recent 14 events at wrightwood are based on sample and contextual evidence in fumal et al 2002 and site context and slip history in weldon et al 2002 pallett creek event and dating descriptions are from published sources for the five most recent events at wrightwood our results are consistent with pre viously published estimates with generally comparable or narrower uncertainties for pallett creek our earthquake date estimates generally overlap with previous results but typically have broader uncertainties some event date estimates are very sensitive to details of data interpretation the historical earthquake in 1857 ruptured the ground at both sites but is not constrained by radiocarbon data radiocarbon ages peat accumulation rates and historical constraints at pallett creek for event x yield a date estimate in the earliest 1800s and preclude a date in the late 1600s this event is almost certainly the historical 1812 earthquake as previously concluded by sieh et al 1989 this earthquake also produced ground deformation at wrightwood all events at pallett creek except for event t about a d 1360 and possibly event i about a d 960 have corresponding events at wrightwood with some overlap in age ranges event t falls during a period of low sedimentation at wrightwood when conditions were not favorable for recording earthquake evidence previously pro posed correlations of pallett creek x with wrightwood w3 in the 1690s and pallett creek event v with w5 around 1480 fumal et al 1993 appear unlikely after our dating reevaluation apparent internal inconsistencies among event layer and dating relationships around events r and v identify them as candidates for further inves tigation at the site conditional probabilities of earthquake recurrence were estimated using poisson lognormal and empirical models the presence of 12 or 13 events at wrightwood during the same interval that 10 events are reported at pallett creek is reflected in mean recurrence intervals of 105 and 135 years respectively average poisson model 30 year conditional probabilities are about 20 at pallett creek and 25 at wrightwood the lognormal model conditional probabilities are somewhat higher about 25 for pallett creek and 34 for wrightwood lognormal variance rln estimates of 0 76 and 0 70 respectively imply only weak time predictability conditional probabilities of 29 and 46 respectively were estimated for an em pirical distribution derived from the data alone conditional probability uncertainties are dominated by the brevity of the event series dating uncertainty contributes only secondarily wrightwood and pallett creek event chronologies both suggest varia tions in recurrence interval with time hinting that some form of recurrence rate modulation may be at work but formal testing shows that neither series is more ordered than might be produced by a poisson process

structure from motion photogrammetry a low cost effective tool for geoscience applications abstract high resolution topographic surveying is traditionally associated with high capital and logistical costs so that data acquisition is often passed on to specialist third party organisations the high costs of data collection are for many applications in the earth sciences exacerbated by the remoteness and inaccessibility of many field sites rendering cheaper more portable surveying platforms i e terrestrial laser scanning or gps impractical this paper outlines a revolutionary low cost user friendly photogrammetric technique for obtaining high resolution datasets at a range of scales termed structure from motion sfm traditional softcopy photogrammetric methods require the 3 d location and pose of the camera s or the 3 d location of ground control points to be known to facilitate scene triangulation and reconstruction in contrast the sfm method solves the camera pose and scene geometry simultaneously and automatically using a highly redundant bundle adjustment based on matching features in multiple overlapping offset images a comprehensive introduction to the technique is presented followed by an outline of the methods used to create high resolution digital elevation models dems from extensive photosets obtained using a consumer grade digital camera as an initial appraisal of the technique an sfm derived dem is compared directly with a similar model obtained using terrestrial laser scanning this intercomparison reveals that decimetre scale vertical accuracy can be achieved using sfm even for sites with complex topography and a range of land covers example applications of sfm are presented for three contrasting landforms across a range of scales including an exposed rocky coastal cliff a breached moraine dam complex and a glacially sculpted bedrock ridge the sfm technique represents a major advancement in the field of photogrammetry for geoscience applications our results and experiences indicate sfm is an inexpensive effective and flexible approach to capturing complex topography

quasi periodic recurrence of large earthquakes on the southern san andreas fault it has been 153 yr since the last large earthquake on the southern san andreas fault california united states but the average interseismic interval is only 100 yr if the recurrence of large earthquakes is periodic rather than random or clustered the length of this period is notable and would generally increase the risk estimated in probabilistic seismic hazard analyses unfortunately robust characterization of a distribution describing earthquake recurrence on a single fault is limited by the brevity of most earthquake records here we use statistical tests on a 3000 yr combined record of 29 ground rupturing earthquakes from wrightwood california we show that earthquake recurrence there is more regular than expected from a poisson distribution and is not clustered leading us to conclude that recurrence is quasi periodic the observation of unimodal time dependence is persistent across an observationally based sensitivity analysis that critically examines alternative interpretations of the geologic record the results support formal forecast efforts that use renewal models to estimate probabilities of future earthquakes on the southern san andreas fault only four intervals 15 from the record are longer than the present open interval highlighting the current hazard posed by this fault

straightforward reconstruction of 3d surfaces and topography with a camera accuracy and geoscience application topographic measurements for detailed studies of processes such as erosion or mass movement are usually acquired by expensive laser scanners or rigorous photogrammetry here we test and use an alternative technique based on freely available computer vision software which allows general geoscientists to easily create accurate 3d models from field photographs taken with a consumer grade camera the approach integrates structure from motion sfm and multi view stereo mvs algorithms and in contrast to traditional photogrammetry techniques it requires little expertise and few control measurements and processing is automated to assess the precision of the results we compare sfm mvs models spanning spatial scales of centimeters a hand sample to kilometers the summit craters of piton de la fournaise volcano with data acquired from laser scanning and formal close range photogrammetry the relative precision ratio achieved by sfm mvs measurement precision observation distance is limited by the straightforward camera calibration model used in the software but generally exceeds 1 1000 i e centimeter level precision over measurement distances of 10s of meters we apply sfm mvs at an intermediate scale to determine erosion rates along a 50 m long coastal cliff seven surveys carried out over a year indicate an average retreat rate of 0 70 0 05 m a 1 sequential erosion maps at 0 05 m grid resolution highlight the spatio temporal variability in the retreat with semivariogram analysis indicating a correlation between volume loss and length scale compared with a laser scanner survey of the same site sfm mvs produced comparable data and reduced data collection time by 80

six similar sequential ruptures of the san andreas fault carrizo plain california we document the precise sizes but not the dates of the six latest offsets across the san andreas fault at wallace creek california three and perhaps four of these including the latest in 1857 show dextral offset of 7 5 8 m the third and fourth offsets however are just 1 4 and 5 2 m the predominance of similar offsets for the latest six events suggests that the fundamental properties of the fault system that control slip size do not vary greatly from event to event the large offsets imply that ruptures involving this site are typically more than 200 km long

a reevaluation of the pallett creek earthquake chronology based on new ams radiocarbon dates san andreas fault california 1 the pallett creek paleoseismic record occupies a keystone position in most attempts to develop rupture histories for the southern san andreas fault previous estimates of earthquake ages at pallett creek were determined by decay counting radiocarbon methods that method requires large samples which can lead to unaccounted sources of uncertainty in radiocarbon ages because of the heterogeneous composition of organic layers in contrast accelerator mass spectrometry ams radiocarbon dates may be obtained from small samples that have known carbon sources and also allow for a more complete sampling of the section we present 65 new ams radiocarbon dates that span nine ground rupturing earthquakes at pallett creek overall the ams dates are similar to and reveal no dramatic bias in the conventional dates for many layers however individual charcoal samples were younger than the conventional dates leading to earthquake ages that are overall slightly younger than previously reported new earthquake ages are determined by bayesian refinement of the layer ages based on stratigraphic ordering and sedimentological constraints the new chronology is more regular than previously published records in large part due to new samples constraining the age of event r the closed interval from event c to 1857 has a mean recurrence of 135 years 83 2 years and a quasiperiodic coefficient of variation cov of 0 61 we show that the new dates and resultant earthquake chronology have a stronger effect on cov than the specific membership of this long series and dating precision improvements from sedimentation rates

high resolution satellite imagery mapping of the surface rupture and slip distribution of the mw 7 8 14 november 2001 kokoxili earthquake kunlun fault northern tibet china the mw 7 8 kokoxili earthquake of 14 november 2001 which ruptured a 450 km long stretch of the sinistral kunlun strike slip fault at the northeastern edge of the tibet plateau china ranks as the largest strike slip event ever recorded instrumentally in asia newly available high resolution satellite hrs images pixel size 1 m acquired in the months following the earthquake proved a powerful tool to complement field investigations and to produce the most accurate map to date of the coseismic displacements along the central kusai hu segment of the rupture the coseismic rupture geometry south and west of buka daban feng near the earthquake epicenter was also investigated in detail along the kusai hu segment slip parti tioning is for the first time observed to occur simultaneously during a single event with two parallel strands 2 km apart localizing almost pure strike slip and normal faulting in all 83 new hrs coseismic offset measurements some of which calibrated by field work show large well constrained variations 100 of the slip function over distances of only25 km tension cracks opening ahead of the shear dislocation and later offset by the upward propagating strike slip rupture were observed dem onstrating that the rupture front propagated faster at depth than near the surface the triple junction between the central kusai hu segment the kunlun pass fault where the rupture ended and the xidatan dongdatan segment which could be the next segment to fail along the main kunlun fault acted as a strong barrier implying that direct triggering of earthquake rupture on the xidatan dongdatan segment by kokoxili type earthquakes may not be the rule

detection of subtle tectonic geomorphic features in densely forested mountains by very high resolution airborne lidar survey abstract despite successes elsewhere in the world 2 m resolution dems from a standard airborne lidar survey failed to detect small tectonic geomorphic features in densely forested high relief mountains of central japan our new 0 5 m dems from an unprecedentedly high resolution lidar survey along the neodani fault now reveal a number of previously unknown fault scarps as well as other hidden geomorphic features the survey achieves a ground return density of 6 2 m 2 out of a total shot density of as much as 12 7 m 2 the main factor to gain sufficient ground returns in unfavorable conditions is a large side lap of 70 between flight swaths which means that any specific area in the target zone is scanned three or more times from different angles evaluation of dems with resolution from 0 25 to 10 m assures that a 0 5m resolution lidar dem is necessary for the detection of subtle tectonic breaks another key factor for complete detection of small tectonic geomorphic features is the application of a recently developed dem visualization red relief image map rrim which allows mapping of all the small features with various sizes orientations and morphology overcoming major drawbacks of classic dem visualizations a very high resolution lidar survey aided with rrim visualization as used in this study provides a more reliable approach for the detailed mapping of slight active fault traces hidden under dense vegetation

near field investigations of the landers earthquake sequence april to july 1992 the landers earthquake which had a moment magnitude m w of 7 3 was the largest earthquake to strike the contiguous united states in 40 years this earthquake resulted from the rupture of five major and many minor right lateral faults near the southern end of the eastern california shear zone just north of the san andreas fault its m w 6 1 preshock and m w 6 2 aftershock had their own aftershocks and foreshocks surficial geological observations are consistent with local and far field seismologic observations of the earthquake large surficial offsets as great as 6 meters and a relatively short rupture length 85 kilometers are consistent with seismological calculations of a high stress drop 200 bars which is in turn consistent with an apparently long recurrence interval for these faults