strain partitioning in the transition area between oblique subduction and continental collision hikurangi margin new zealand spatial differences in late quaternary structural style and deformation rates indicate a complex pattern of strain partitioning within the transition area from oblique subduction beneath southern north island to oblique continental collision in northern south island new zealand the late quaternary structure of the offshore southern hikurangi margin is determined here using seismic reflection profiles mr1 side scan sonar swath images em12dual multibeam swath bathymetry and backscatter images and sediment core and dredge samples where oblique 50 subduction of the oceanic hikurangi plateau is occurring beneath southern wairarapa region the steep dissected upper margin consists of a wedge of rocks that are being deformed by strike slip and reverse faults beneath the lower margin an accretionary wedge of quaternary age has developed rapidly by frontal accretion of a thick succession of turbidites on the pacific plate estimates of late quaternary geological strain rates have been made on two margin perpendicular transects across southern north island and the offshore margin to budget the predicted nuvel 1a plate motion more than 33 55 of the total plate motion is expressed in the offshore part of the upper plate above the subduction detachment in the central hikurangi margin between 40 s and 41 s this offshore deformation could potentially include margin parallel fault slip of up to 14 15 mm yr across the upper plate strain is partitioned into zones of folding and thrust faulting and possibly more than one zone of strike slip faulting but the partitioning may be incomplete with oblique slip thrusting an important component of the deformation the wide distribution of deformation within the upper plate partially reflects strong coupling between the subducting oceanic plateau and the leading edge of the overriding plate this coupling increases toward the southwest where the continental part of the subduction zone beneath marlborough may now be inactive or very strongly coupled toward the southwest the transpressive deformation style of the upper wairarapa margin continues into the upper marlborough margin and onshore into the strike slip marlborough fault system of northern south island in contrast the accretionary wedge narrows to the southwest and terminates in southeastern cook strait approximately above the transition from subducted oceanic crust to subducted continental crust of the pacific plate farther southwest beneath the lower marlborough margin low strain folding and thrust faulting is occurring but the style of deformation is not typical of the accretionary wedge this shortening results either from a small amount of subduction slip beneath marlborough and or from contractional strain partitioned to the southeast of the continental transpression zone whereas the initial onset of continental collision occurs in marlborough the surface expression of deformation of the pacific plate occurs south of 42 30 s normal faulting of the northwestern margin of the continental chatham rise possibly reflects flexural extension of the pacific plate crust at the southern end of the subduction zone whereas folding and thrust faulting of the north canterbury coastal region results from nw se contraction of the delaminated upper crust entering the southern alps collision zone

infrared stimulated luminescence dating of late quaternary aggradation surfaces and their deformation along an active fault southern north island of new zealand abstract loess and silt that overlies and forms the matrix of late quaternary fluvial aggradation surfaces from the central wairarapa valley southern north island new zealand have been dated using infrared stimulated luminescence irsl of k feldspar in fine grained 4 11 m diameter mineral fractions three irsl protocols were used involving both the additive dose with thermal transfer correction and regeneration methods and from four samples using both the additive dose method and the single aliquot regeneration method eight luminescence ages of between and 16 1 1 6 and 10 0 0 9 kyr date the most extensive and youngest fluvial aggradation surface that has been deformed by wairarapa fault the most active fault of the north island dextral shear zone the ages provide absolute rates of dextral and vertical slip on the fault over the last 30 kyr that deforms two aggradation surfaces an average horizontal slip rate of 11 5 0 5 mm yr and variable vertical slip rates of between 0 09 and 1 7 mm yr that correlate with compressional bulges developed on the upthrown side of the fault caused by left lateral sidesteps and reversals of the upthrown side of the fault the horizontal slip rate indicates that one third of the 33 mm yr strike slip motion of oblique convergence between the australian and pacific plates is taken up by the wairarapa fault three younger luminescence ages of

finite faults and inverse theory with applications to the 1979 imperial valley earthquake abstract using a representation theorem from elastodynamics subsurface slip on a known fault is formulated as the solution to an inverse problem in which recorded surface ground motion is the data two methods of solution are presented the least squares method which minimizes the squared differences between theory and data and the constrained least squares method which simultaneously maintains a set of linear inequalities instabilities in the solution are effectively eliminated in both methods and the sensitivity of the solution to small changes in the data is quantitatively stated the inversion methodology is applied to 77 components of near field ground acceleration recorded during the 15 october 1979 imperial valley earthquake the faulting is constrained to propagate bilaterally away from the epicenter at an average velocity of 90 per cent of the shear wave speed on a vertical fault plane extending from the surface to 10 km depth inequality constraints are used to keep the faulting sequence physically reasonable by maintaining right lateral motion and positive slip velocity the preferred solution is stable and provides a good fit to the data it is also realistic and consistent with observed surface offsets and independent estimates of seismic moment

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

direct marine terrestrial correlations wanganui basin new zealand the last 1 million years abstract wanganui basin a back arc basin in north island new zealand contains a detailed sequence of interfingering terrestrial and shallow marine sediments spanning the entire quaternary rhyolite tephras erupted from the taupo volcanic zone together with magnetostratigraphy and biostratigraphy facilitate correlations between wanganui basin and the astronomically calibrated oxygen isotope chronology of deep sea cores particularly over the last 1 ma eustatic changes are interpreted from both marine shelf sediments and marine terraces within the basin non marine sediments including loess dunesand and alluvial deposits coupled with pollen analyses are used to interpret climatic changes they can also be directly related to the marine record through stratigraphic relations between marine and non marine deposits in the basin

five thousand years of surface ruptures on the wellington fault new zealand implications for recurrence and fault segmentation new paleoseismic studies have been undertaken on the wellington hutt valley w hv segment of the wellington fault to characterize its late holocene record of surface rupturing earthquakes trenches and radiocarbon dates from te kopahou and te marua have provided evidence and improved timing for the four most recent earthquake ruptures these events have been recognized on the basis of upward terminating faults coseismic deposition progressive displacement and faulting of colluviums at te kopahou colluvial and scree deposition resulting from surface rupture and strong earthquake shaking buries old ground surfaces associated with peat and or soil development at te marua the timing of the two youngest events has been refined by bracketing the ages of the youngest faulted and unfaulted alluvial terraces of the hutt river assuming that the w hv segment acts as a rupture segment along its length the approximate timings of these faulting events is as follows the most recent faulting event event i occurred between 110 and 310 cal yr b p a d 1640 1840 the penultimate faulting event event ii between 790 and 930 cal yr b p event iii occurred between 1835 and 2340 cal yr b p and event iv between 2460 and 4900 yr b p the minimum and maximum earthquake recurrence intervals derived from the four youngest events are 715 and 1575 yr respectively with a median value of 1145 yr revisions of the earthquake timing recurrence interval data and recently the single event displacement and slip rate collectively reduce the seismic hazard for the w hv segment of the wellington fault a four event paleoearthquake record from the pahiatua section of the wellington fault is statistically similar to that from the w hv segment this has significant implications with respect to the rupture length and magnitude or clustering of future surface rupturing earthquakes on the wellington fault

a 2300 year paleoearthquake record of the southern alpine fault and fiordland subduction zone new zealand based on stacked turbidites turbidites from three sedimentary basins data and probably the a d 1826 fiordland earthquake and the well dated a d 1717 alpine fault earthquake the recurrence intervals are shorter than recently published recurrence data from the alpine fault on land reflecting mixed fault source earthquake records and potentially increased alpine fault segmentation offshore online material details of the laboratory methods and analytical techniques applied to sedimentrary cores photos of seafloor substrates and fan core oxcal codes and results and sediment transport analysis 1 embed inline graphic 1 gif

coseismic strike slip at a point during the last four earthquakes on the wellington fault near wellington new zealand 1 we analyze progressively displaced late quaternary 12 ka fluvial terraces along the wellington fault near wellington new zealand optically stimulated luminescence dating indicates that degradational terraces were produced at a rate of about one terrace per 1000 years similar to the rate of earthquake surface rupturing along the hutt river near te marua we measured the strike slip of 15 terrace risers and paleochannels on the lowest 8 of these terraces of holocene age the river after earthquakes was generally capable of smoothing its faulted riverbanks the dextral offsets appear to fall into several groupings that record slip accumulation during the last four earthquakes we calculate a mean single event slip of 5 0 0 24 m 95 confidence with an rms scatter 1 of slips about the mean of 1 5 m the coefficient of variation cv of single event slip is thus 0 30 this cv is slightly less than a recently compiled global average for point measurements on strike slip faults suggesting that the southernmost wellington fault has behaved in a more nearly characteristic way we speculate that recent large earthquake ruptures have been bounded on their southern end by the wellington fault s offshore fault termination and perhaps on their northern end by a 2 km wide releasing step over such persistent sources of rupture arrest might have led to a relative uniformity of rupture dimensions and slip amounts we infer a late holocene dextral slip rate of 4 5 0 4 mm yr 1 and 8 2 mm yr and a mean earthquake recurrence interval of 610 1100 years

slip rate on the wellington fault new zealand during the late quaternary evidence for variable slip during the holocene we investigate fault offset fluvial terraces at two sites along the hutt river near wellington new zealand to determine horizontal slip rates for the southern part of the wellington fault for the last 100 ka using photogrammetric analysis of historic aerial photos we measured the original displacements of terrace risers at emerald hill which have been modified by urban development fourteen sediment samples from this site and from another location dry creek were analyzed using optically stimulated luminescence osl methods yielding ages of between 10 ka and 100 ka from our displacement age relations we estimate an average slip rate of graphic 1 2 during the last 100 ka however slip on the wellington fault has not been steady throughout this time during the holocene there was a phase of heightened ground rupture activity between 10 and 8 ka when an incremental dextral displacement of 32 m accrued this was followed by a period of relative quiescence between 8 and 4 5 ka with 5 m of displacement during this time another period of heightened activity followed resulting in a further 20 m of slip during the last 4 5 ka our inference of variable slip during the holocene accords with independent evidence from paleoseismological studies at other sites along the wellington fault slip on the wellington fault and its variability through time may be influenced by activity on neighboring faults online material part i optically stimulated luminescence osl dating technical report and results part 2 stratigraphic logs 1 embed inline graphic 1 gif

geodynamic model for the palaeozoic crustal consolidation of western and central europe abstract the crystalline basement of western and central europe consists of a mosaic of crustal elements which were consolidated during pre grenvillian the grenvillian dalslandian morarian cadomian caledonian and hercynian orogenic cycles contemporaneous with the caledonian suturing of the precambrian laurentia greenland and fennosarmatian shields a number of gondwana derived cadomian micro cratons were accreted to the southern margin of laurasia following the late caledonian paroxysm the devonian and early carboniferous evolution of europe was dominated by continued northward subduction of the proto tethys plate at an arc trench system parallelling the southern margin of laurasia the accretion of additional gondwana derived continental fragments back arc rifting and a sinistral translation of major proportions between the laurentia greenland and the fennosarmatian sub plates the acadian and bretonian orogenies were of the pacific type the visean collision of gondwana with laurasia marked the onset of the himalayan type variscan orogeny during which collision related compressive stresses overpowered the devonian early carboniferous back arc rift systems and caused the development reactivation of a subduction zones the central armorican and saxothuringian successor basins became folded and destroyed during the latest visean whilst the variscan foredeep became scooped out in part by nappes involving the basement during the late westphalian major crustal shortening during the variscan diastrophism was accompanied by the anatectic remobilisation of subducted crustal and upper mantle material and a widespread syn and late orogenic magmatism the latest carboniferous early permian reorientation of the convergence direction between gondwana and laurasia induced the development of a complex wrench fault system transecting the variscan fold belt and an extensive post orogenic volcanism the hypotheses summarised here require confirmation by further palaeomagnetic and radiometric data and faunal analyses

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

variscan to alpine heterogeneous palaeo stress field above a major palaeozoic suture in the carpathian foreland southeastern poland abstract the tectonic evolution of the region adjacent to the sw border of the east european craton is crucial for understanding the palaeozoic amalgamation of europe and its later evolution we present a structural analysis of the brittle deformation fault slip data inversion and folding carried out in the cambrian to cenozoic rocks of the european platform in se poland to characterize the late palaeozoic maastrichtian palaeocene and miocene tectonics of this region the variscan late carboniferous palaeo stress pattern was characterized by n s to nne ssw oriented compression as inferred from the folding of the palaeozoic mainly devonian rocks the compression was associated with the northwesterly present day coordinates motion of gondwana towards the northerly situated laurussia subsequently the mid polish trough mpt developed in an extensional regime the stress regime changed to compressional at the maastrichtian palaeocene transition in response to the africa europe plate kinematics the compressional regime induced the tectonic inversion of the mid polish trough the stress pattern was characterized by ne sw oriented compression in the holy cross mts hcm area and in the radomsko high folds and faults in the mesozoic cover revealed a sinistral reactivation of the holy cross fault hcf and of nw se trending faults the alpine stress patterns were related to the subduction of the european platform beneath the carpathian orogen the flexural bending of the subducted lithosphere induced a homogeneous middle miocene n s extension in the carpathian foreland subsequently the northward propagation of the carpathian front resulted in late middle miocene n s compression restricted to the proximal area of the frontal thrusts implied by a strain partitioning at a low friction contact between the carpathian nappes and the european platform since the palaeozoic the teisseyre tornquist zone ttz behaved as lithospheric weak zone which has been reactivated during the maastrichtian palaeocene change in stress regime it resulted in the tectonic inversion of the polish trough inherited faults conditioned superficial stress perturbations and focused the deformation

using synthetic seismicity to evaluate seismic hazard in the wellington region new zealand summary a computer synthetic seismicity program for the wellington region has been implemented and used to infer the effect of the 1848 awatere and 1855 wairarapa mega earthquakes on the timing of the next characteristic magnitude 7 35 or more earthquake on the wellington hutt valley section of the wellington fault we find that on average over several hundred cases a wellington fault event is delayed by 259 years the synthetic catalogue of 500 000 events magnitude 5 5 or more also gives the average recurrence time of characteristic wellington fault events 960 yr and their coefficient of variation 0 40 there is also a strong retarding effect on moderate magnitude wellington fault events magnitude 6 5 7 3 sensitivity tests indicate that these results are robust the synthetic model contains 58 known major faults and 3000 randomly placed small faults to reproduce the rate and spatial distribution of background seismicity observed recently from the synthetic catalogue it is possible to determine the average recurrence rate for all major faults also there is strong evidence of the short term 10 yr temporal clustering of large events throughout the region a factor that contributes to a highly variable moment release rate over time spans of a few hundred years

an assessment of source parameters of earthquakes in the cordillera of the western united states abstract source parameters for 50 earthquakes occurring between 1915 and 1988 have been used to examine the faulting characteristics of magnitude 5 5 to 7 8 earthquakes within the western u s cordillera an area extending from the eastern sierra nevada to the great plains and from northwestern montana to trans pecos texas source parameters used in this study include seismic information from first motion analyses body and surface waveform modeling geodetic studies and geological studies of surface faulting the principal results of this analysis include 1 all earthquakes occurred on faults dipping 38 or more and no evidence for listric of low angle planar faulting was found 2 all m 7 0 earthquakes occurred at depths 12 km and were composed of multiple subevents 3 most earthquakes 70 per cent had unilateral ruptures and 4 no individual subevent had a rupture length 21 km

source complexity of the 1988 armenian earthquake evidence for a slow after slip event we analyzed teleseismic p and s waves using a multiple event deconvolution method to investigate the source process of the spitak armenia earthquake of december 7 1988 teleseismic long period body waves exhibit complex waveforms significantly more complex than those normally seen for an event of this size we identified two groups of subevents one is a group of strike slip events during the first 20 s the other is a dip slip event initiating at about 30 s after the initial rupture the tensor sum of all the subevents is essentially strike slip strike 302 dip 59 rake 143 with a scalar moment of 1 47 10 19 n m the seismic moment of the dip slip event strike 89 dip 60 rake 88 is 5 6 10 18 n m nearly 40 of the total and the moment release rate is slower than the other subevents with a strike slip mechanism we call this event a slow after slip event the mechanism of the after sup event is consistent with the present day deformation pattern in the caucasus where north south compression is predominant due to the continental collision between the arabian plate and the russian platform this result suggests that in a region where both strike slip motion and crustal shortening are taking place like southern california a large strike slip event may accompany large thrust events and vice versa in order to determine the total coseismic deformation pattern it is essential to resolve these multiple events in time space and mechanism

integrated outcrop reservoir characterization modeling and simulation of the jackfork group at the baumgartner quarry area western arkansas implications to gulf of mexico deep water exploration and production the lower pennsylvanian jackfork group in arkansas has been the subject of studies field trips and publications for many years because of excellent outcrop exposures of different deep water architectural elements this latest study is focused on the baumgartner quarry located near kirby arkansas which exposes a series of vertical walls in three dimensions this quarry has not been as well documented as other popular exposures although three dimensional 3 d quarry faces exist and the quarry strata comprise part of a complete 600 m 1970 ft thick near continuous jackfork stratigraphic sequence not unlike younger deep water stratigraphic exploration targets in the gulf of mexico and elsewhere subsurface problems including reservoir uncertainties and reservoir performance of lobe versus channel fill deposits are addressed based on our work in the quarry a 3 d sequence stratigraphic model was developed using a correlation of seven measured stratigraphic sections in the quarry the 180 m 590 ft thick quarry strata consist of a lower lowstand systems tract lst lower sandstones dominated by channel fill sandstones overlain by a shaly transgressive systems tract condensed section and then by an upper lst upper sandstones dominated by sheet or lobe sandstones this model was translated into an updip against salt field which is analogous to some deep water gulf of mexico reservoirs performance simulation was conducted on the model using a one injector water well and two vertical producing wells one of which was connected to the injector via a channel sandstone and the other of which was offset from the channel sandstone results yielded 60 more production from the connected injector producer pair than from the nonconnected pair comparison between the lower channel prone sandstones and the upper sheet prone sandstones revealed that the sheet prone sandstone is more sustainable whereas the channel prone sandstone exhibits a larger drop in production rate during a 10 yr production period these results illustrate the value of 3 d outcrop models for reservoir performance simulation for development planning of deep water fields with limited data control such as in the deep water gulf of mexico

broadband study of the 1989 loma prieta earthquake we determined the source characteristics of the oct 18 1989 loma prieta california earthquake using teleseismic data the solution from body waves gives a mechanism with dip 70 rake 138 and strike 128 and a seismic moment of 3 10 26 dyne cm m w 6 9 this solution is similar to those obtained from long period rayleigh and love waves p nl waves and first motion data the body wave form suggests a depth of about 15 km the effective duration of the source is 6 sec which suggests a fault length of 30 km and 15 km for bilateral and unilateral faulting respectively considering the extent of the aftershock area we used 35 km as an estimate of the total rupture length the strike slip and the thrust components of the coseismic slip are 177 and 159 cm respectively the large thrust component raises an important question regarding the recurrence pattern if the loma prieta earthquake is a characteristic earthquake with a recurrence interval of about 100 years the 159 cm displacement implies a long term uplift rate of about 1 cm year which appears too large for this region three hypotheses for reconciling this apparent conflict are 1 the geometry of plate motion along the santa cruz mountain segment changes over a time scale of several thousand years so that the coseismic displacement has not accumulated enough to produce high topographic relief 2 the coseismic shp direction varies from event to event 3 the slip plane of the 1989 loma prieta earthquake is different from the major boundary between the pacific and the north american plates if this is the case the loma prieta earthquake is a rather rare non characteristic event the surface slip of about l m for the 1906 san francisco earthquake is one of the key data in long term forecasting no surface slip was observed for the 1989 loma prieta earthquake even if the horizontal slip at depth is as large as 1 8 m this points to a risk of relying too heavily on surface observations for long term seismic risk analysis

an integrated chemo and sequence stratigraphic framework of the early pennsylvanian deepwater outcrops near kirby arkansas usa and its implications on remnant basin tectonics abstract the jackfork group in arkansas u s a is a major training ground for academics students and petroleum industry geoscientists interested in deep water exploration and development several superb outcrop sections are exposed and over the years numerous papers have been published on these rocks the kirby sections in western arkansas provide a unique opportunity to build a complete and continuous sequence stratigraphic framework for early pennsylvanian time in the ancient ouachita basin there are 25 outcrops including 12 roadcuts on highway 27 and 13 measured sections in the baumgartner quarry all the measurements and interpretations on the outcrops were integrated with previous work using modern concepts of deepwater turbidite geology including 1 regional tectonic and sequence stratigraphic framework of the stanley group jackfork group and johns valley shale in the ouachita basin 2 deepwater outcrop characterization and correlation from the degray lake section dierks section and big rock quarry which are on the trend of the depositional fairway 3 chemostrata data from key shale layers which are considered as potential correlative condensed sections twenty five key shale samples from kirby degray and dierks sections have been tested using inductively coupled plasma and mass spectrometry icp ms tests an additional 525 samples were later collected for handheld x ray fluorescence xrf tests for both major and trace elements results of sequence and chemostrata analysis indicate that the entire kirby sections consist of at least three 3rd order sequences from the bottom of the jackfork group to the middle of the johns valley group and over ten 4th order sequences caused by a combined effect of tectonic uplift eustatic sea level change mixed sediment provenance and shifting of depositional fairways when the ouachita basin was transitioning from a passive margin to a remnant marine basin rare earth and trace element results are compared with known tectonic data to further pinpoint the tectonic environment of the ouachita basin during early pennsylvanian time which is dominantly a continental arc setting

luminescence dating of poorly bleached sediments from scotland abstract two types of poorly bleached sediment are differentiated and the applicability of various luminescence dating methods is assessed the methods are applied to three fluvioglacial sediments from scotland it is shown that it is possible to detect sediments that contain a mixture of well bleached and unbleached grains using the single aliquot additive dose method or the analysis of the scatter in aultiple aliquot additive dose growth curve

source mechanisms of three moderate california earthquakes of july 1986 abstract we studied the source processes of three moderate size earthquakes in california the m s 6 0 event of july 8 1986 near palm springs the m s 5 8 shock of july 13 1986 offshore of oceanside and the m s 6 2 event of july 21 1986 in the chalfant valley on the east side of the sierra nevada the centroidal source parameters are estimated by inversion of long period p and sh waves recorded at teleseismic distances by seismographs of worldwide networks a more detailed description of the source is then obtained by analyzing broadband seismograms the north palm springs earthquake had a simple rupture process most of the seismic moment was released in the first 3 sec in a single step the strike of the source fault plane follows the average trend of the banning fault and its dip agrees with the dip of the fault plane delineated by the aftershocks the faulting mechanism of the main shock is right lateral strike slip with a sizable reverse component that is consistent with uplift north of the banning fault the earthquake offshore of oceanside had a slightly more complex rupture process the far field source time function consists of two pulses that represent the release of most of the moment in the first 3 sec the source mechanism indicates reverse faulting with the compressional axis trending northeast almost perpendicular to the trend of mapped faults offshore the event does not appear to be associated with major mapped faults in the area but the strike of one of the nodal planes agrees with the trend of the major mapped faults offshore and its mechanism is consistent with the missing component of plate convergence not taken up by the onshore strike slip fault systems and the idea of a weak san andreas fault system the rupture process of the chalfant valley earthquake was yet more complicated the source time function indicates that in a 4 sec time window three asperities were broken the source mechanism indicates right lateral strike slip faulting with a small normal faulting component on a fault that dips approximately 50 southwest earthquake activity suggests that presently the deformation in the northern part of the owens valley which includes the chalfant valley is dominated by conjugate strike slip faults which strike obliquely to the main range bounding normal faults the waveforms indicate the presence of a low velocity zone at a depth of about 20 km in the crust in the chalfant valley a synthesis of information from waveform modeling first motion fault plane solutions and aftershock distributions indicates that the nucleation and or termination of rupture for the north palm springs and the chalfant valley events were controlled by preexisting fault geometry

reinterpretation of depositional processes in a classic flysch sequence pennsylvanian jackfork group ouachita mountains arkansas and oklahoma discussion the pennsylvanian jackfork group in the ouachita mountains of arkansas and oklahoma has conventionally been interpreted by many workers including us as a classic flysch sequence dominated by turbidites in a submarine fan setting however normal size grading and bouma sequences indicative of turbidite deposition are essentially absent in these sandstone beds they appear massive i e structureless in outcrop but when slabbed reveal diagnostic internal features these beds exhibit sharp and irregular upper bedding contacts inverse size grading floating mudstone clasts a planar clast fabric lateral pinch out geometries moderate to high detrital matrix up to 25 sigmoidal deformation duplex structures and contorted layers all these features indicate sand mplacement by debris flows mass flows and slumps mud matrix in these sandstones was sufficient to provide cohesive strength to the flow discrete units of current ripples and horizontal laminae have been interpreted to represent traction processes associated with bottom current reworking the dominance of sandy debris flow and slump deposits nearly 70 at degray spillway section and bottom current reworked deposits 40 at kiamichi mountain section and the lack of turbidites in the jackfork group have led us to propose a slope setting our rejection of a submarine fan setting has important implications for predicting sand body geometry and continuity because deposits of fluidal turbidity currents in fans are laterally more continuous than those of plastic debris flows and slumps on slopes a turbidite dominated fan model would predict an outer fan environment with laterally continuous sheetlike sandstones for the jackfork group in southern oklahoma and western arkansas whereas a debris flow slump model would predict predominantly a slope environment with disconne ted sandstone bodies for the same area

centroid moment tensor solutions for 35 earthquakes in western north america 1977 1983 abstract seismic records from the gdsn sro asro dwwssn rstn and ida networks were used to obtain long period t 45 sec focal mechanisms for 35 earthquakes in western north america longitude 140 to 110 latitude 30 to 60 employing the centroid moment tensor method of dziewonski et al 1981 and dziewonski and woodhouse 1983 the same algorithm was applied to all events the smallest m 0 6 4 10 23 dyne cm being an aftershock to the 1979 imperial valley california earthquake and the largest m 0 8 5 10 26 dyne cm the 1980 eureka california earthquake all events were analyzed with and without the constraint m r m r 0 on the moment tensor an ad hoc criterion on the relative variance reduction was employed to determine a favored solution our solutions show general agreement with other published results as well as with tectonic structures agreement with results obtained using the abundant local and regional data confirms the adequacy of the method in determining long period source parameters and verifies its applicability in regions where local and regional data are scarce or nonexistent in some cases disagreement between our solution and results from first motion studies appears to be related to source complexities our moment tensor represents the total stress release of the composite event a consistent westward movement of the centroid locations reflects lateral heterogeneities in the crust and mantle

luminescence dating and its application to key pre late devensian sites in scotland abstract relatively few sites have been identified in scotland that contain records that predate the peak of the late devensian glaciation ca 18 ka bp where such records have been identified they have assumed a key role in developing our understanding of climate change in scotland radiocarbon dating has been the primary chronological tool applied to these sites but the reliability of age determinations in excess of 30 ka is questionable in this paper we describe the results of a programme which applies luminescence dating methods to eight key pre late devensian sites in scotland methods were developed and tested to enable the identification of samples for which luminescence dating was only able to provide an upper limit on the age because of the limited light exposure that the sample experienced at deposition these new approaches were applied to four sites where independent age control was available this meant that the choice of sediments from test sites was restricted to those sediments which were formed in the last 40 000 years and hence were amenable to radiocarbon dating the luminescence age estimates for the control sites and the pre late devensian sites are discussed within the context of any existing chronological control on a site by site basis

coseismic rupture and preliminary slip estimates for the papatea fault and its role in the 2016 mw 7 8 kaikōura new zealand earthquake coseismic rupture of the 19 km long north striking and west dipping sinistral reverse papatea fault and nearby structures and uplift translation of the papatea block are two of the exceptional components of the 14 november 2016 mw 7 8 kaik ura earthquake the dual stranded papatea fault comprising main sinistral reverse and western dip slip strands ruptured onshore and offshore from south of waipapa bay to george stream in the north bounding the eastern side of the papatea block fault rupture mapping was aided by the acquisition of multibeam bathymetry light detection and ranging lidar topography and other imagery as well as differential lidar d lidar from along the coast and clarence river valley on land vertical throw and sinistral offset on the papatea fault was assessed across an aperture of 100 m using uncorrected d lidar and field data to develop preliminary slip distributions the maximum up to the west throw on the main strand is 9 5 0 5 m and the mean throw across the papatea fault is 4 5 0 3 m the maximum sinistral offset measured near the coast on the main strand is 6 1 0 5 m from these data and considering fault dip we calculate a maximum net slip of 11 5 2 m and an average net slip of 6 4 0 2 m for the papatea fault surface rupture in 2016 large sinistral reverse displacement on the papatea fault is consistent with uplift and southward escape of the papatea block as observed from interferometric synthetic aperture radar insar and optical image correlation datasets the throw and net slip are exceedingly high for the length of the papatea fault such large movements likely only occur during multifault kaik ura type earthquakes that conceivably have recurrence times of 5000 12 000 yrs the role of the papatea fault in the kaik ura earthquake has significant implications for characterizing complex fault sources in seismic hazard models

successive episodes of normal faulting and fracturing resulting from progressive extension during the uplift of the holy cross mountains poland conjugate normal faults extension fractures and mesh fracture structures were investigated in devonian carbonate rocks from the southern part of the holy cross mountains hcm central poland strata folded during variscan deformations were later subject to uplift resulting in increasing extension in the upper part of the rock mass at a relatively shallow depth faults and fractures developed in an orderly vertical succession first mesh fracture structures and conjugate normal fault sets enclosing acute dihedral angles 2 of over 45 were formed next conjugate normal faults with 2 less than 45 and sub vertical extension fractures developed the occurrences of conjugate normal sets enclosing different dihedral acute angles and extension fractures with similar strikes juxtaposed with each other at the same stratigraphic level point to the fact that the uplifted rock mass underwent successive changes in a stress regime leading to the formation of these structures the first sets of conjugate normal faults and fractures developed when the hcm were uplifted during a late stage of variscan deformations the next sets of extension fractures and conjugate normal faults developed during the following uplift events interrupted by periods of sedimentation of the mesozoic and younger strata

estimating surface rupture length and magnitude of paleoearthquakes from point measurements of rupture displacement we present a method to estimate paleomagnitude and rupture extent from measurements of displacement at a single point on a fault the variability of historic ruptures is summarized in a histogram of normalized slip then scaled to give the probability of finding a given displacement within a rupture for any magnitude considered the histogram can be inverted assuming any magnitude earthquake is as likely as another yielding probability density functions of magnitude and rupture length for any given displacement measurement to improve these distributions we include a term to account for the probability that the earthquake would cause ground rupture and two alternative distributions of earthquake magnitude the gutenberg richter magnitude distribution predicts shorter rupture lengths and smaller magnitudes than does a uniform distribution where any magnitude earthquake is considered equally likely longer ruptures and larger magnitudes than the uniform model are predicted by an alternative magnitude distribution designed to return site average displacement this model is a generalization of the characteristic earthquake model and reasonably describes paleoseismic findings on the southern san andreas fault where slip is accommodated by average displacements of a few meters and earthquake recurrence times of 100 250 years our results should increase the value of paleoseismic displacement measurements for hazard assessment in particular they quantify probability estimates of earthquake magnitude and rupture length where point observations of rupture displacement are available and so can contribute to probabilistic seismic hazard analyses online material rupture profiles used to sample rupture variability

surface rupture earthquakes over the last 1000 years in the wellington region new zealand and implications for ground shaking hazard the wellington region is cut by five active right lateral strike slip faults wairarapa wellington ohariu shepherds gully pukerua and wairau faults that have average recurrence intervals of meter scale surface rupture that range from 500 years to 5000 years and lateral slip rates that range from 1 to 10 mm yr only the wairarapa fault has ruptured since european settlement since circa a d 1840 paleoseismological studies on these faults have allowed the compilation of a complete record of surface rupture events over the past 1000 years in the wellington region within this time period there does not appear to be any temporal clustering of surface rupture events on adjacent faults the m 8 a d 1855 wairarapa earthquake did not trigger rupture on any other fault in the region the most recent surface faulting event on the wellington fault 290 440 cal years b p cal years are calendar years before a d 1950 does not coincide with rupture of any other onland fault and over 300 years separate the timing of the second most recent rupture on the wellington fault 660 720 cal years b p and the most recent rupture of the ohariu fault 1060 1140 cal years b p the most recent rupture of the shepherds gully pukerua fault is probably older than that of the ohariu fault the apparent nonclustering of surface rupture earthquakes in the wellington region has been documented only for the on land strike slip faults there are other possible seismogenic sources in the region and thus important issues remain to be addressed regarding the history of large earthquakes in the wellington region 1 the seismogenic potential and earthquake recurrence interval of the subduction thrust beneath wellington is not known 2 the timing of rupture events on the offshore portion of the wairau fault is not known and 3 paleoseismic data are not available for the section of the wellington fault north of the wellington hutt valley segment estimates of earthquake hazard in the wellington region for all return times greater than 50 years that incorporate paleoseismicity data are between one and two modified mercalli mm intensity units higher than the hazard based solely on the historical seismicity catalog and the hazard is spatially more variable using a deterministic attenuation model the level of shaking hazard approaches near maximum values within a return time of 500 years largely reflecting the recurrence interval 500 770 years of surface rupture earthquakes on the wellington fault inclusion of a plausible model for magnitude 8 subduction zone earthquakes does not affect the level of mm intensity in wellington region at return times greater than 500 years but does make a small contribution to the hazard at return times between 50 and 500 years

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

stratigraphic architecture and fault offsets of alluvial terraces at te marua wellington fault new zealand revealed by pseudo 3d gpr investigation 1 past earthquake slips on faults are commonly determined by measuring morphological offsets at current ground surface because those offsets might not always be well preserved we examine whether the first 10 m below ground surface contains relevant information to complement them we focus on the te marua site new zealand where 11 alluvial terraces have been dextrally offset by the wellington fault we investigated the site using pseudo 3d ground penetrating radar and also produced a high resolution digital elevation model dem of the zone to constrain the surface slip record the gpr data reveal additional information 1 they image the 3d stratigraphic architecture of the seven youngest terraces and show that they are strath terraces carved into graywacke bedrock each strath surface is overlain by 3 5 m of horizontally bedded gravel sheets including two pronounced and traceable reflectors 2 thanks to the multilayer architecture terrace risers and channels are imaged at three depths and their lateral offsets can be measured three to four times constraining respective offsets and their uncertainties more reliably and 3 the offsets are better preserved in the subsurface than at the ground surface likely due to subsequent erosion deposition on the latter from surface and subsurface data we infer that te marua has recorded six cumulative offsets of 2 9 7 6 18 23 2 26 and 31 m 1 2 m large earthquakes on southern wellington fault might produce 3 5 m of slip slightly less than previously proposed pseudo 3d gpr thus provides a novel paleoseismological tool to complement and refine surface investigations

relations between earthquake magnitude and fault rupture dimensions how regionally variable are they data on subsurface rupture dimensions and seismic moments have been gathered for earthquakes in new zealand screened for data quality and analyzed along with the multiregion rupture area data of hanks and bakun 2002 regression analyses have been carried out for relations among magnitude and rupture length subsurface width area slip and aspect ratio statistical comparisons show that there are significant differences between the regressions of new zealand and multiregion data the new zealand relations among magnitude area and displacement are linear those among magnitude subsurface rupture length and width are bilinear whereas those between magnitude and rupture aspect ratio l w are trilinear the magnitudes predicted from rupture subsurface lengths widths or areas by multiregion relations are about 0 4 units smaller than those obtained from relations based on new zealand data the multiregion relations predict ruptures that are untenably large for new zealand on the basis of structural and other evidence separate regressions were carried out for the california china and japan subsets of the multiregion data and it was found that there were statistically significant differences between new zealand and california new zealand and japan new zealand and china and japan and california the respective contributions of rupture area and mean displacement to seismic moment are very different in new zealand from those in california japan and china suggesting that rupture styles differ with geological region in a manner yet to be appropriately defined thus multiregion relations are a poor approximation of the new zealand data and perhaps also of the data of other regions where geological conditions differ substantially from the multiregion average

late quaternary strike slip on the eastern part of the awatere fault south island new zealand new zealand straddles the obliquely convergent boundary between the pacific and australian plates in central south island plate motion is accommodated by oblique collision of continental crust along the alpine fault in the southern alps and in north island by subduction of oceanic crust beneath the continental hikurangi margin between these two zones oblique convergence is accommodated across the 150 km wide marlborough fault system which is transitional between the two different styles of margins dextral slip in the marlborough fault system is partitioned among four principal faults of which the awatere fault is one our data on the eastern part of the awatere fault provide insight into styles of surface faulting and active deformation in continental transpression zones we 1 document the segmentation and kinematics of oblique slip on the fault including a discrepency between long term and short term accumulation of vertical motion 2 describe an along strike gradient in the degree of slip partitioning of oblique plate motion 3 measure late quaternary strike slip rates of 6 8 mm yr at several sites along the fault rates that decrease eastward to

variscan tectonics in the holy cross mountains poland and the role of structural inheritance during alpine tectonics abstract the present study was carried out in the holy cross mountains hcm of south central poland and includes computation of palaeostresses following angelier s method and field structural analysis the palaeozoic basement of the hcm comprises two tectonic units separated by the major wnw ese striking holy cross fault hcf fold analysis indicates a n s to nne ssw direction of variscan shortening micro structures and fold analysis from upper devonian rocks further reveal 1 a brittle tectonic event due to a nw se compression preceding folding that could be related to pre late carboniferous tectonics due to block transport within the tornquist teisseyre zone ttz and 2 polyphase variscan folding comprising a an early stage of n s shortening marked by north verging ramps b a main folding event and axial cleavage formation involving n s to nne ssw shortening and c a late stage of shortening deforming older folds and cleavage a mainly extensional tectonic regime dominated from the permian until the cretaceous during which time the hcf was reactivated as a normal fault large nw se faults bordering the mid polish trough mpt developed subsequent tectonic inversion of the mpt resulted in basin uplift mid polish swell mps palaeostress computations from mesozoic strata suggest a ne sw direction for the main maastrichtian paleocene shortening phase in addition to two minor brittle events resulting from n s and e w compression analysis of local folds in the mesozoic cover indicates a causal relationship with the maastrichtian paleocene reactivation of older faults in particular en echelon folds in the radomsko elevation suggest a sinistral reactivation of the palaeozoic hcf folds in the southwestern part of the hcm argue for reactivation in the reverse mode of a nw se trending fault bordering the mps that originated in the mesozoic in palaeozoic strata post variscan brittle deformation and micro fault reactivation are attributed to the tectonic events of maastrichtian paleocene age reactivation of n s fractures is demonstrated in the rzepka quarry where fractures in devonian dolomites are filled by calcite probably formed during a late variscan event and by younger late permian early triassic sediments they were subsequently reactivated as dextral strike slip faults during the ne sw maastrichtian paleocene compression

structural evolution along the inner forearc of the obliquely convergent hikurangi margin new zealand the accretionary margin of the hikurangi forearc on the southeast coast of the north island of new zealand is part of the leading edge of the australian plate which is overriding the obliquely converging pacific plate we investigate the last 10 m y of deformation history of the innermost western quarter of the total width of the forearc through analysis of the sedimentologic and structural evolution of the eketahuna area on the east coast of the north island the eketahuna area is ideal for such a study because emergence of the margin in the quaternary has exposed a complete late neogene rock record this record has allowed us to chronicle the strain history from 10 ma to about 2 5 ma this forearc region was the locus of subsidence and marine deposition in the latest pliocene this part of the margin began to shorten through folding and reverse faulting bringing an end to basin filling the period of shortening was brief and by the late pleistocene reverse faulting had ceased and was immediately succeeded by dextral strike slip faulting in some cases along the same faults presently the dominant strain regime in the inner quarter of the forearc is strike slip faulting this structural history illustrates that over time the pattern of strain partitioning has changed in the hikurangi forearc the switch from crustal shortening to dextral shear along the major faults in this area in the last 1 m y may be a response to more than 10 of clockwise rotation in the southern hikurangi forearc in pliocene and pleistocene time this rotation is a consequence of the fact that the accretionary margin is undergoing continuous deformation between the obliquely converging australian and pacific plates in this area at the southernmost end of the kermadec hikurangi subduction system the inboard portion of this young accretionary margin is exceptionally well exposed today probably in part because of the late neogene subduction of relatively thick buoyant crust of the hikurangi chatham plateau

the iapetus model a plate tectonic concept for the variscan belt of europe abstract a plate tectonic model is presented explaining the evolution of the variscan belt of europe it regards the iapetus ocean and its branch the tornquist sea as the only ocean involved in the caledonian variscan and alleghenian mega orogen the iapetus and its marginal basins disappeared through oblique subduction and collision in the following sequence 1 1 northeastern iapetus including the tornquist sea caledonian orogeny 2 2 central iapetus acadian orogeny 3 3 adjacent marginal basins variscan orogeny and 4 4 southwestern iapetus alleghenian orogeny the area of the variscides was part of the continental margin of gondwana made up of ridges and ensialic basins no ocean lay within the variscan area during the palaeozoic although patches of oceanic crust probably existed in rift basins e g the lizard ophiolite after the silurian early devonian closure of northwestern and central iapetus the variscan area was surrounded by cratons on three sides in a manner similar to that around the modern mediterranean sea the subsequent variscan orogeny was essentially an ensialic thrusting and folding induced by a further approach of gondwana toward laurentia after the variscan collision gondwana rotated clockwise to the west by moving along a strike slip zone this rotation during the carboniferous opened the palaeo tethys in the east and caused the alleghenian collision in the west the middle ordovician to permian palaeogeography is presented on a series of maps modelling tectonic displacement and plate motions avalonia is interpreted as the ordovician volcanic island arc of gondwana separated from mainland gondwana by an oceanic gulf or a back arc basin the iberian arc may have originated by a continental escape of iberia from the center of collision into the oceanic gulf the variscan austro alpine and southern alpine units are today located near their earliest early carboniferous position

statistical analysis of turbidite bed thickness patterns from the alpine fold and thrust belt of western and southeastern greece abstract a statistical evaluation of turbidite bed thickness was performed for 11 turbidite successions which constitute part of foreland basins formed along the alpine fold and thrust belt of western and southeastern greece the purpose was to compare the results from this study with previously published investigations and discuss if and how statistical approaches could contribute to the environmental analysis of turbidite deposits in tectonically complex areas bed thickness datasets exhibit a clear non normal signal in their distribution behavior statistical analysis was focused on i fitting of widely used non normal theoretical distribution models using robust non parametric goodness of fit statistical tests and ii detecting the possible presence of asymmetric bed thickness cycles and or non random bed thickness clustering results indicate that the studied bed thickness datasets are well characterized by a bimodal lognormal distribution model probably reflecting deposition from both high and low density turbidity currents several datasets exhibit distributions characterized by power law tails exponential distribution types were not observed all datasets exhibit non random thinning upward bed thickness trends probably due to tectonically induced gravity flows proposed methods for identifying depositional sub environments using turbidite bed thickness statistics were found to have limited applicability observations of the present study may prove useful for the environmental analysis of turbidite deposits in fold and thrust belt areas characterized by limited outcrop exposures

the 1971 san fernando earthquake a double event evidence is presented which suggest that the 1971 san fernando earthquake may have been a double event that occurred on two separate subparallel thrust faults it is postulated that the initial event took place at depth on the sierra madre fault zone which runs along the base of the san gabriel mountains rupture is postulated to have occurred from a depth of about 15 km to a depth of about 3 km a second event is thought to have initiated about 4 sec later on another steeply dipping thrust fault which is located about 4 km south of the sierra madre fault zone the surface trace of this fault coincides with the san fernando fault zone which was the principal fault associated with surface rupture it is postulated that rupture propagated from a depth of 8 km to the free surface the moments of the first and second events are approximately 0 7 10 26 dyne cm and 1 0 10 26 dyne cm respectively this model is found to explain the combined data sets of strong ground motions teleseismic p and s waveforms and static offsets better than previous models which consist of either a single fault plane or a plane having a dip angle which shallows with decreasing depth nevertheless many features of the observed motions remain unexplained and considerable uncertainty still exists regarding the faulting history of the san fernando earthquake

late neoproterozoic to early palaeozoic palaoegeography of the holy cross mountains central europe an integrated approach study of geochemistry examination of isotope ages of detrital minerals palaeomagnetic analysis and a study of the trilobites were performed to provide constraints on the palaeogeographical position of the holy cross mountains in late ediacaran early palaeozoic time the geochemical results indicate an active continental margin or continental island arc provenance of the ediacaran sediments sediments from a passive continental margin were deposited here during the cambrian and ordovician the palaeomagnetic pole isolated from cambrian rocks of the malopolska region of the holy cross mountains corresponds to the cambrian segment of the baltic apparent polar wander path isotope age estimations indicate that cambrian sediments of the malopolska region contain detritus not only from a latest neoproterozoic source but also from sources with ages of c 0 8 0 9 ga 1 5 ga and 1 8 ga the malopolska brunosilesia dobrugea and moesia terranes which originally developed near the present southern edge of baltica and were partly involved in the cadomian orogen were dextrally relocated along its trans european suture zone margin the first stage of this movement took place as early as latest ediacaran time while baltica rotated anticlockwise anticlockwise rotation of baltica at the cambrian ordovician boundary implies further dextral movement of the malopolska block

application of an iterative least squares waveform inversion of strong motion and teleseismic records to the 1978 tabas iran earthquake an iterative least squares technique is used to simultaneously invert the strong motion records and teleseismic p waveforms for the 1978 tabas iran earthquake to deduce the rupture history the method solves for both slip amplitudes and rupture times on a finite fault several inversions of the data are done to determine the best fitting hypocenter average rupture velocity and source time function within the range of our parameter search the effects of using different data sets and different parametrizations of the problem linear versus nonlinear are also considered teleseismic body waves are shown to be essential to obtain a reliable solution due to the sparse coverage of the fault plane by strong motion stations a simple triangular source time function is compared with a modified kostrov source time function for a circular rupture and a constant propagating stress drop although the waveforms used in the inversions can not resolve between these two time functions the kostrov source time function gives a moment estimate and maximum fault displacement more consistent with long period surface waves and field observations the results of the iterative inversion for slip amplitudes and rupture times are compared with the results of a linear inversion for slip amplitudes in which the rupture velocity is fixed flexibility in the sequence of faulting for the linear inversion is obtained by allowing multiple rupture intervals a consensus of all the inversion runs indicates a complex multiple source for the tabas earthquake with four main source regions over a fault length of 90 km and an average rupture velocity of 2 5 km sec

facies of slurry flow deposits britannia formation lower cretaceous north sea implications for flow evolution and deposit geometry mud rich sandstone beds in the lower cretaceous britannia formation uk north sea were deposited by sediment flows transitional between debris flows and turbidity currents termed slurry flows much of the mud in these flows was transported as sand and silt sized grains that were approximately hydraulically equivalent to suspended quartz and feldspar in the eastern britannia field individual slurry beds are continuous over long distances and abundant core makes it possible to document facies changes across the field most beds display regular areal grain size changes in this study fining trends especially in the size of the largest grains are used to estimate palaeoflow and palaeoslope directions in the middle part of the britannia formation stratigraphic zones 40 and 45 slurry flows moved from south west and south towards the north east and north most zone 45 beds lens out before reaching the northern edge of the field apparently by wedging out against the northern basin slope zone 40 and 45 beds show downflow facies transitions from low mud content dish structured and wispy laminated sandstone to high mud content banded units in zone 50 at the top of the formation flows moved from north to south or north west to south east and their deposits show transitions from proximal mud rich banded and mixed slurried beds to more distal lower mud content banded and wispy laminated units the contrasting facies trends in zones 40 and 45 and zone 50 may reflect differing grain size relationships between quartz and feldspar grains and mud particles in the depositing flows in zones 40 and 45 quartz grains average 0 30 0 32 mm in diameter 0 10 mm coarser than in zone 50 the medium grained quartz in zones 40 and 45 flows may have been slightly coarser than the associated mud grains resulting in the preferential deposition of quartz in proximal areas and downslope enrichment of the flows in mud in zone 50 flows mud was probably slightly coarser than the associated fine grained quartz resulting in early mud sedimentation and enrichment of the distal flows in fine grained quartz and feldspar mud particles in all flows may have had an effective grain size of 0 25 mm both mud content and suspended load fallout rate played key roles in the sedimentation of britannia slurry flows and structuring of the resulting deposits during deposition of zones 40 and 45 the area of the eastern britannia field in block 16 26 may have been a locally enclosed subbasin within which the depositing slurry flows were locally ponded slurry beds in the eastern britannia field are lumpy sheet like bodies that show facies changes but little additional complexity there is no thin bedded facies that might represent waning flows analogous to low density turbidity currents the dominance of laminar cohesion dominated shear layers during sedimentation prevented most bed erosion and the deposystem lacked channel levee and overbank facies that commonly make up turbidity current dominated systems britannia slurry flows although turbulent and capable of size fractionating even fine grained sediments left sand bodies with geometries and facies more like those deposited by poorly differentiated laminar debris flows

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

the july 1986 oceanside ml 5 3 earthquake sequence in the continental borderland southern california an earthquake of m l 5 3 occurred at 32 58 7 n 117 51 5 w southwest of oceanside in san diego county at 13 47 13 july 1986 ut this main shock was followed by an extensive aftershock sequence with 55 events of m l 3 0 during july 1986 the epicenters of the main shock and aftershocks are located at the northern end of the san diego trough bahia soledad fault zone sdt bs where it changes strike from northwest to a more westerly direction through a left offset or a bend in the fault the northwest striking sdt bs is one of three strike slip fault systems that constitute the offshore agua blanca fault system the spatial distribution of the aftershocks indicates a unilateral 7 to 9 km long rupture to the east southeast away from the epicenter of the main shock the focal mechanism of the main shock also has an east southeast striking and south dipping plane with mostly reverse movement on it focal mechanisms of the m l 3 0 aftershocks show both reverse and strike slip movement the reverse focal mechanisms indicate that this sequence may have occurred on a thrust fault that provides for a left stepping offset or a bend in the san diego trough fault as movement is transferred to the west along the santa cruz catalina island escarpment some of the aftershocks that are located to the southeast of the main shock and have strike slip focal mechanisms suggest activation of the northwest trending san diego trough fault a stress inversion of the focal mechanism data shows that the maximum principal stress determined from the focal mechanisms of the main shock and 22 aftershocks that occurred within 36 hours of the main shock has an azimuth of s30 w plunging 18 the maximum principal stress determined from 30 aftershocks that occurred from 15 july to 2 october 1986 has an azimuth of s20 w plunging 18 the values the measure of the relative sizes of the principal stresses are approximately 0 07 and 0 1 respectively indicating that the intermediate and minimum principal stress are of similar magnitude the results of the stress inversion and the focal mechanisms that showed reverse faulting suggest that the inner continental borderland offshore from oceanside is not currently a pure strike slip tectonic regime but rather a strike slip mixed with reverse faulting regime when the 52 aftershock focal mechanisms are divided into four groups and the stress inversion is repeated the change in stress can be described as a progressive counter clockwise rotation of 14 of the orientation of the maximum principal stress to a more southerly direction with the greatest change in stress orientation observed shortly after the main shock the abundance of aftershocks may be related to the large temporal variation in stress orientation that in turn may have resulted from the small stress drop of the main shock

rates of active faulting during late quaternary fluvial terrace formation at saxton river awatere fault new zealand a flight of faulted fluvial terraces at saxton river on the awatere fault northeast south island new zealand preserves the incremental slip history and detailed paleoearthquake chronology of this major strike slip fault here six fluvial terraces have been progressively displaced across the inland molesworth section of the fault with horizontal displacements ranging from 6 m for an ephemeral channel on the youngest terrace to 81 m for the riser above the oldest terrace new optically stimulated luminescence ages for abandonment of the two oldest terrace treads are 14 5 1 5 and 6 7 0 7 ka when combined with new measurements of incremental horizontal displacements and previous age data these new ages indicate that strike slip on this part of the awatere fault has been occurring at a near constant rate of 5 6 0 8 mm yr since ca 15 ka this rate is similar to recent slip rate estimates for an adjoining section of the same fault to the east which suggests that there is near complete slip transfer across the junction between the two fault strands comparison of the magnitudes and ages of the terrace riser displacements to the timing of paleoearthquakes on the molesworth section allows the mean per event horizontal displacement over the eight most recent surface rupture events to be estimated at 4 4 0 8 m between ca 5 ka and ca 2 ka surface rupturing earthquakes increased in frequency and decreased in their mean coseismic displacements to 2 6 m during this time the sense of local dip slip also shifted from north side up to south side up rapid incision of saxton river in the mid holocene may have caused a perturbation in the near surface stress directions acting on the fault plane beneath the saxton river valley forcing a change in the near surface fault geometry that resulted in the shift in sense of dip slip

kinematics and paleoseismology of the vernon fault marlborough fault system new zealand implications for contractional fault bend deformation earthquake triggering and the record of hikurangi subduction earthquakes the 40 km long vernon fault in the marlborough fault system of new zealand is characterized by dextral slip with subordinate reverse slip and exhibits abrupt variations in strike of up to 90 onshore fieldwork paleoseismic trenching and offshore high frequency seismic reflection data are integrated together to identify the kinematics and paleoseismic history of three sections of the fault 1 the nne striking vernon hills section which branches off from the awatere fault 2 the ne striking big lagoon section which borders big lagoon to the south and extends 9 km offshore to the east and 3 the e w striking wairau basin section which is entirely submarine the vernon fault can be shown to have a dextral slip rate of 0 8 4 9 mm yr with a preferred estimate of 0 9 mm yr on the big lagoon section we infer that a further unrecognized 3 4 mm yr of dextral slip has been accommodated off fault as a result of accumulated slip on small and or blind reverse faults adjacent to a 6 km wide restraining bend in the main fault the onshore and offshore paleoseismic records are in good agreement these indicate three to five events at eight sites and a mean recurrence interval of 3 9 1 2 ka over the past 16 kyr with the last event taking place at 3 3 ka earthquakes on the vernon fault are responsible for 25 of the holocene subsidence rate of big lagoon over the last 13 ka most of the subsidence of this lagoon has been the result of surface deformation related with southern hikurangi megathrust earthquakes

reinterpretation of depositional processes in a classic flysch sequence pennsylvanian jackfork group ouachita mountains arkansas and oklahoma discussion authors reply

temporal variations in latest quaternary slip across the australian pacific plate boundary northeastern south island new zealand rates of latest quaternary slip from stream terraces and moraines displaced by faults of the alpine shear system in ne south island new zealand vary in space and time detailed histories of fault slip are obtained from combining displacement data with estimates of the age of the surface from weathering characteristics precision in surface ages is 5 20 using rock weathering rinds and 15 50 using soil properties the oldest surfaces examined are 15 20 ka and have right lateral fault offsets up to 400 600 m the main faults of the in the ne south island the wairau awatere clarence hope kekerengu and porters pass faults have average latest quaternary right lateral slip rates of 3 10 5 10 7 10 25 40 5 7 and 3 4 mm yr respectively every fault has undergone a substantial decrease in lateral slip rate in the last 3 5 kyr summed across the plate boundary the average latest quaternary slip rates are comparable to long term rates of horizontal slip across the australian pacific plate boundary around 40 mm yr parallel to the boundary and rates of geodetic strain and seismic moment release over the last 50 100 years approximately the same however sums of lateral fault slip rates over the interval from 15 to 5 ka exceed the plate motions whereas late holocene lateral fault slip rates are less than half the long term average the best explanation of these variations is slip across the plate boundary is episodic varying over perhaps 5 kyr intervals this implies that 15 20 kyr is the time interval necessary to average out shorter 5 kyr episodic variations in plate boundary motions

allogenic vs autogenic controls on megaflute formation abstract megaflutes are large concave up erosional scours within turbidite successions and have been described from modern and ancient settings they are interpreted to represent the passage of erosive largely bypassing turbidity currents here two categories of megaflute are distinguished 1 allogenic corresponding to the case above where erosion is associated with sediment bypass leading to deposition farther into the basin e g the classical megaflutes of the ross formation 2 autogenic where the erosion occurs during aggradation of the host bed both types are illustrated with examples from the carboniferous succession of northern england the distinction is important because the formative processes are different leading to distinct facies associations for each group for example allogenic flutes are interpreted to form in systems with large variations in flow magnitude and imply significant down dip sediment accumulation whereas autogenic megaflutes are thought to be formed by unsteady flows and imply less significant bypass autogenic megaflutes occur above inversely graded poorly sorted sandstones which improve in sorting and decrease in mud content upwards to the megaflute surface which is overlain by a well sorted mantle of the coarsest sediment found within the bed detailed grain size profiles suggest that autogenic megaflutes develop in response to waxing of flows from a depositional to an erosional state cannibalizing the already deposited sand bed as the flow wanes reverting to a depositional state the coarsest grained fraction of its remaining load is deposited first forming the basal part of a variably well developed normally graded and overall finer grained interval thus it is interpreted that flow unsteadiness promotes the formation of these features which has implications for the reconstruction of paleoenvironmental conditions specifically the generation mechanisms return periods flow routing into the basin and the resultant flow characteristics of turbidity currents

evidence from gps measurements for contemporary interplate coupling on the southern hikurangi subduction thrust and for partitioning of strain in the upper plate the spatial extent and strength of contemporary coupling between the pacific and australian plates on the hikurangi subduction interface beneath the wellington region of new zealand are not well known consequently the potential for the plate interface to produce great thrust earthquakes or to load the major wellington and wairarapa faults in the overlying plate is also unknown to address these issues a gps network across the southern north island has been partially or wholly surveyed six times between 1992 and 1999 and yields well determined relative velocities between 82 points the relative velocity of the east coast with respect to the west coast across the 80 km width of the southern end of the north island is 14 mm yr 1 at an azimuth of 258 this is about one third of and closely parallel to the nuvel 1a relative velocity of the pacific with respect to the australian plate 39 4 mm yr 1 at 261 strain rate solutions indicate partitioning of contemporary strain with a 35 change in principal axis orientations across the network using elastic dislocation theory an inversion of the observed point velocities and their full variance covariance matrix determines the variation with depth of contemporary coupling at the subduction interface if uniform coupling is assumed then 100 coupling occurs from very shallow depths down to 29 1 km however if variable coupling is assumed it reaches 100 at depths between 16 and 24 km at greater depths there is a transition zone at least 20 km wide down to a depth of at least 40 km over which contemporary coupling diminishes to zero these depth ranges correlate moderately well with low angle thrust focal mechanisms recently obtained by other workers and indicate that the downdip width of the interface over which a great thrust earthquake could occur exceeds 100 km elastic dislocation models also explain the observed partitioning of strain with coulomb stress calculations indicating that the wairarapa fault is being loaded at seismogenic depths

field study of a highly active fault zone the xianshuihe fault of southwestern china the xianshuihe fault of western sichuan province china is one of the world s most active faults having produced 4 earthquakes during this century of magnitude 7 along a 350 km length of the fault at least 8 such events have occurred since 1725 in the more limited 150 km long segment including luhuo and daofu major earthquakes in 1904 1923 1973 and 1981 m 7 7 7 6 6 9 were associated with overlapping surficial fault ruptures and with individual left lateral displacements as large as 3 6 m field studies indicate that this high degree of activity is typical of the fault s longer term history the holocene left lateral slip rate on the north western segment of the fault has been 15 5 mm yr decreasing to about 5 mm yr on its southeastern segment based on radiometrically dated offset stream channel and terrace deposits and on offset glacial moraines physiographic features of active faulting are fully as diagrammatic as those of california s san andreas fault mainly because of high altitude preservation and the absence of cultural modification on this eastern margin of the tibetan plateau detailed en echelon tensional and pushup features resulting from surface ruptures in 1973 1955 1923 and 1893 can still be recognized today and new data have been collected bearing on the offsets and fault rupture lengths during these and other events the locations and magnitudes of historic earthquakes suggest that the characteristic earthquake model may apply to the xianshuihe fault obvious geometric segmentation of the fault has controlled the initiation and termination of ruptures in some events whereas segmentation control for others remains obscure based on the historic record repeat times estimated from slip rates and current seismic gaps two segments are particularly likely sites for m 7 earthquakes in the near future the 65 km long segment between daofu and qianning and the 135 km long segment bracketing kangding continuing creep has been documented along some segments of the fault and this together with the high degree of activity and other unique attributes makes the xianshuihe fault one of the most promising sites in the world for earthquake prediction and hazard evaluation studies

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

location and geometry of the wellington fault new zealand defined by detailed three dimensional georadar data 1 earthquakes with surface wave magnitudes of 7 3 7 9 are estimated to be associated with the rupture of the wellington fault at relatively regular intervals of 500 770 years the last such earthquake probably happened between ad 1510 and 1660 along its southern segment the wellington fault passes through wellington new zealand s capital and the densely populated hutt valley it is considered to be a highly hazardous structure to map the shallow geometry of the wellington fault we have collected 3 d ground penetrating radar georadar data at two sites along the fault in the hutt valley at one site the first ever georadar fault plane reflections from an active strike slip fault are observed they coincide with conspicuous diffractions generated by abrupt truncations of structures against the fault plane these georadar data provide the most vivid shallow images of any active fault surveyed to date at the second site apparent offsets of lineaments in the sedimentary sections on either side of the fault are consistent with 20 m of dextral displacement estimated from the offset of a nearby terrace riser the dips and minimum depth extents of the primary zones of fault displacement at the two sites are 55 75 se and 20 m and 72 84 se and 12 m respectively although the georadar defined zones of faulting are a few meters wide prominent reflection fabrics suggest that shearing fracturing and crushing extend for several tens of meters on either side of the fault

displacement transfer between intersecting regional strike slip and extensional fault systems interaction and displacement transfer between active intersecting strike slip or transform and extensional fault systems are examined outcrop data from a well preserved strike slip fault and rift intersection in new zealand are compared to a global data set of 13 such intersections in both continental and oceanic crust displacement transfer between strike slip and normal faults is typically accomplished by gradual changes of fault orientations and slip vectors close to the intersection zone for two and three plate configurations these changes result in sub parallelism of the slip vectors of the component faults with their line of intersection the dimensions of the area over which fault strike and slip vectors change are principally controlled by the extent to which displacements on the dominant of the two intersecting fault systems are confined to a single slip surface or distributed across a zone where slip is spatially distributed the region in which the two displacement fields are superimposed produces transtension and associated oblique slip this distributed off fault deformation facilitates the development of a quasi stable configuration of the fault intersection region maintaining both the regional geometry and kinematics of the intersection zone which in many cases would not be possible for rigid block translations the dimensions of the transition zone are larger for continental crust than for oceanic crust because oceanic crust is thinner fault geometries in oceanic crust are simpler two plate configurations and the slip vectors of the component intersecting fault systems are sub parallel

the significance of the variscan orogeny in the świetokrzyskie mountains mid polish uplands the wietokrzyski horst created during the laramide phase is situated in the central part of the mid polish uplands it is composed of folded paleozoic rocks partly covered by mesozoic sediments in this area two tectonostratigraphic units can be distinguished the kielce unit to the s and the ysogory unit to the n

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

correlation of fluvial terraces within the hikurangi margin new zealand implications for climate and baselevel controls abstract a correlation of fluvial terraces is presented for eight non glacial catchments of the eastern north island new zealand within the actively uplifting hikurangi margin using a combination of loess and tephra coverbed stratigraphy and radiocarbon and osl dating of fluvial deposits and loess coverbeds we demonstrate correlation of four fill terraces t1 t4 the available age constraints suggest t1 15 30 ka t2 31 50 ka t3 50 70 ka and t4 115 ka but the association and temporal link with loess deposits suggest correlation with cold periods and thus the refinement of t2 late mis 3 31 40 ka t3 mis 4 55 70 ka t4 mi substage 5b 90 ka 5d 110 ka or mis 6 140 160 ka the ability to correlate terraces between catchments plus the lack of independent evidence for tectonic triggering events indicates terraces have probably formed in response to either climate terrestrial or baselevel sea level control climate control is indicated by the temporal link of post glacial incision with re establishment of forest cover and of lgm aggradation with limited grass and shrub cover and periglacial processes aggradation due to increased sediment supply under reduced vegetation is dramatically demonstrated by formation of the taupo pumice alluvium terrace in response to inundation by volcanic deposits unwelded ignimbrite following the 1 8 ka taupo eruption and the response to post settlement

rupture complexity of a moderate sized mb 6 0 earthquake broadband body wave analysis of the north yemen earthquake of 13 december 1982 abstract the occurrence of the north yemen earthquake of 13 december 1982 provides an important opportunity to study source properties of earthquakes in the southern arabian peninsula although moderate in size m b 6 0 this earthquake is the largest to have occurred in the region since the deployment of the global digital seismograph network p waves recorded at teleseismic distances can be obtained from stations of this network and of the graefenberg array that are flat to displacement and velocity in the frequency range from 0 01 to 5 0 hz the broad bandwidth of the data is necessary for deriving a dynamic description of the earthquake as well as the static properties of the source in contrast inversions using only long period data provide much less insight into the complexity of rupture by fitting the displacement pulse shapes with synthetics we find that the yemen earthquake was a complex rupture consisting of two events that occurred about 3 0 sec apart the depth of both hypocenters is estimated to be 7 km the focal mechanisms of the events each have a nodal plane that strikes 340 and dips 60 to the east however the slip directions of the focal mechanisms are in slightly different directions 230 and 300 respectively the total moment of the earthquake is 3 0 10 25 dyne cm with the second event having three times the moment of the initial event by inverting p wave arrival time differences at each station we find the second hypocenter is located 7 5 km from the initial hypocenter in a direction that is nearly colinear with the nnw striking nodal plane of the focal mechanisms of each event the trend of extensional ground cracks in the epicentral region and the predominant strike of composite focal mechanisms of locally recorded aftershocks are also in a nnw direction from the consistency of these observations we infer that the east dipping nnw striking nodal planes are the fault planes the static stress drop of the first and second events are 44 and 31 bars respectively inverting the energy flux in the velocity waveforms we find the energy radiated by the earthquake is 4 8 10 20 dyne cm this implies an average apparent stress of 4 bars at different times during the aftershock sequence seismicity tended to cluster about one or another of two different planes which although having roughly the same strike had conjugate dips one of these planes delineated late in the aftershock sequence coincides with the inferred fault plane for the main shock the complexity of the main shock and of the aftershock sequence suggests that strain accumulated on a system of strongly interdependent faults as the region became critically loaded the effect of a major rupture was to critically stress faults adjacent to the initial nucleation the second event of the main shock represents the rapid release of stress from the fault system while the ensuing aftershock sequence represents the gradual release of stress

the pyrenean earthquake of february 29 1980 an example of complex faulting abstract an m b 5 1 earthquake occurred on february 29 1980 in the western pyrenees near arudy france the telemetred network of the i p g p operating in this area since 1978 allowed a good localization of this earthquake 43 4 21 n 0 24 59 w depth 4km during the two years preceding this earthquake the seismic activity exhibited a gradual decrease a foreshock of magnitude 1 6 was recorded three hours before the main shock a temporary network set up in the epicentral area a few days after the main shock permitted a precise study of the aftershock sequence fifty fault plane solutions for earthquakes ranging from magnitude 1 5 4 were obtained a complex pattern of faulting was revealed with both strike slip and normal faulting however a regional tectonic stress tensor can be proposed from a detailed investigation of the aftershock sequence this stress tensor is in agreement with previous results in this area

faulting associated with large earthquakes and the average rate of deformation in central and eastern asia we determine approximate average rates of deformation in portions of eastern and central asia for the last 80 years these rates are based on estimates of source dimensions average displacements seismic moments and orientations of faults of all large earthquakes m 7 5 and as many other major earthquakes m 7 0 as possible in asia since 1900 a major part of this study is the compilation of these data for separate parts of asia we combine seismic moment tensors to estimate the average rotational strain or deformation tensors for these regions for the last 80 years we estimate that shortening across the tien shan has occurred at 11 mm yr between 5 and 19 mm yr left lateral shear on easterly trending planes in mongolia in northwestern tibet gansu and ningxia and on the xianshuihe fault in western sichuan has been very rapid more than 10 mm yr in each region and apparently as rapid as 40 mm yr in northwestern tibet gansu and ningxia slower rates of a few to 10 mm yr appear to characterize east west extension and conjugate north south shortening of tibet the earthquake history of the himalaya is consistent with rates of underthrusting of more than 10 mm yr but is probably less than the convergence rate of india with eurasia of about 50 mm yr the overall strain field is consistent with a large part of india s penetration into eurasia being absorbed by the extrusion of material out of india s way as a result southeast china moved at about 21 mm yr east southeast with respect to eurasia in the last 80 years with an uncertainty of about a factor of 2 in this estimated rate

three dimensional modeling of a shoreface shelf parasequence reservoir analog part 2 geologic controls on fluid flow and hydrocarbon recovery wave dominated shoreface shelf parasequences are commonly modeled as simple layer cake reservoirs yet analysis of modern and ancient analogs demonstrates that these intervals contain a more complex physical stratigraphy we investigate the impact of depositional and diagenetic heterogeneity associated with gently dipping clinoform surfaces on fluid flow and recovery during water flooding using a three dimensional model reconstructed from a well exposed outcrop analog we demonstrate that the volume of oil in place is affected by variations in facies thickness associated with interfingering along clinoforms whereas waterflood sweep efficiency is affected by barriers to flow along clinoform surfaces such as calcite cemented layers mudstones and siltstones sweep efficiency is low when water flooding is down depositional dip because oil is bypassed at the toe of each clinothem as water flows preferentially through high quality sandstone facies in the upper part of the parasequence sweep efficiency is higher when water flooding is up depositional dip because the gravity driven downward flow of water sweeps poorer quality sandstone facies in the lower part of the parasequence in both cases injectors may offer limited pressure support to producers water flooding along depositional strike yields good pressure support but poor sweep because the gravity driven flow of water into the lower part of the parasequence is significantly reduced this yields highly variable fluid saturations but a uniform pressure gradient which is consistent with pressure and fluid saturation data from the mature rannoch formation reservoir brent field united kingdom north sea simple layer cake models fail to capture the range of flow behaviors described above and overpredict recovery by up to 20 as a result

paleoseismic evidence of clustered earthquakes on the san andreas fault in the carrizo plain california exposures we have excavated across the san andreas fault contradict the hypothesis that part of the fault in the carrizo plain is unusually strong and experiences relatively infrequent rupture the exposures record evidence of at least seven surface rupturing earthquakes which have been approximately dated by accelerated mass spectrometry radiocarbon analysis of detrital charcoal and buried in situ plants five large earthquakes have occurred since 1218 a d the most recent earthquake event a was the 1857 fort tejon earthquake which we have associated with 6 6 10 m of dextral slip along the main fault trace the penultimate earthquake event b most likely occurred within the period a d 1405 1510 slip from either events b and c combined or from event b alone totals 7 11 m three earthquakes events c d and e occurred in a temporal cluster prior to event b and after approximately a d 1218 the average recurrence interval within this cluster is 73 116 years depending on assumptions events f and g occurred after 200 years b c a depositional hiatus between events e and f may hide evidence of additional earthquakes events b and d within the carrizo cluster of a d 1218 1510 may correlate with events t a d 1329 1363 and v a d 1465 1495 at pallett creek on the mojave segment of the fault this suggests two fault ruptures similar in length to that of 1857 events c and e apparently did not rupture the mojave section which suggests that the carrizo segment has ruptured independently or in combination with segments to the north irregular repeat times of large earthquakes suggest a pattern of clustered events at the end of seismic supercycles

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

estimating prehistoric earthquake magnitude from point measurements of surface rupture abstract we have developed a method for estimating the magnitude of prehistoric earthquakes using displacement data that usually can be collected from paleoseismic investigations this method is necessary because essentially all current magnitude estimates for prehistoric events rely on determining the total length of coseismic surface rupture which is rarely measurable or rely on segmentation scenarios for which uncertainties cannot be quantified although surface rupture length is a better predictor of magnitude than displacement for historic earthquakes paleoseismic investigations are better at providing measurements of the amount of displacement at a site along a fault the key to our method is to incorporate the variability in displacement observed in 14 modern events which allows a formal uncertainty in magnitude to be assigned to prehistoric ruptures we show how multiple measurements along a preserved fraction of a rupture can be combined to reduce the uncertainty in the estimate of magnitude our analysis shows that uncertainty asymptotically approaches the natural variability of ruptures so 5 to 10 displacement measurements are sufficient to characterize paleomagnitude we conclude that sampling of scarps with lengths of even 10 of the original rupture can provide magnitude values that reasonably estimate the earthquake tests of the method using randomly sampled data from the 1992 m w 7 3 landers and 1954 m s 6 8 dixie valley earthquakes provide close approximations of the actual magnitudes

rupture patterns and preshocks of large earthquakes in the southern san jacinto fault zone we relocated the large 1937 1942 and 1954 earthquakes in the san jacinto fault zone the epicenters of the main shocks aftershocks and some preshocks were determined using empirical station corrections from recent small events in the study areas the 1937 ml 5 9 earthquake has an epicenter between the surface traces of the san jacinto and buck ridge faults and aftershocks suggest about 7 km of rupture predominantly to the northwest a significant increase in small earthquake activity occurred about formula yr before this event the 1954 m l 6 2 earthquake is located at the southeast end of the mapped trace of the san jacinto fault and aftershocks suggest about 15 km of rupture further southeast into an area of folded young sediments with no surface fault trace this event was preceded by a cluster of small earthquakes which occurred within an 8 hr period 10 weeks before the main event and in the eventual rupture zone the 1942 m l 6 3 earthquake is located southwest of the southeast end of the coyote creek fault large aftershocks of this event are spread over a 15 by 18 km area southwest of the coyote creek fault and are not associated with any one fault the relation of the 1942 event to the san jacinto fault zone is not simple

the kinematics of a transition from subduction to strike slip an example from the central new zealand plate boundary 1 we develop a kinematic model for the transition from subduction beneath the north island new zealand to strike slip in the south island constrained by gps velocities and active fault slip data to interpret these data we use an approach that inverts the kinematic data for poles of rotation of tectonic blocks and the degree of interseismic coupling on faults in the region convergence related to the hikurangi subduction margin becomes very low offshore of the northern south island indicating that in this region the majority of the relative plate motion has been transferred onto faults within the upper plate as suggested by previous studies this result has implications for understanding the likely extent of subduction interface earthquake rupture in central new zealand easterly trending strike slip faults such as the boo boo fault are the key features that facilitate the transfer of strike slip motion from the northern south island faults further north into the southern north island and onto the hikurangi subduction thrust our results also indicate that the transition from rapid forearc rotation adjacent to the hikurangi subduction margin to a strike slip dominated plate boundary with negligible vertical axis rotation in the south island occurs via a crustal scale hinge or kink in the upper plate compatible with paleomagnetic and structural geological data despite the ongoing tectonic evolution of the central new zealand region our study highlights a remarkable consistency between data sets spanning decades gps thousands of years active faulting data and millions of years paleomagnetic data and bedrock structure

comment on a paper by zou et al 2017 entitled an integrated chemo and sequence stratigraphic framework of the early pennsylvanian deepwater outcrops near kirby arkansas usa and its implications on remnant basin tectonics