porosity and permeability in volcanic rocks a case study on the serie tobifera south patagonia argentina the middle to late jurassic serie tobifera belongs to the chon aike province and extends all over patagonia and the antarctic peninsula it consists largely of ignimbrites epiclastics and rhyolitic lavas and was considered only a minor reservoir rock for oil with fracture permeability petrographic and petrophysical data in selected core samples from the austral basin were collected to determine the processes controlling the porosity and permeability of these volcanic rocks the sequence of processes occurring during cooling and in the post cooling stages can modify sometimes substantially their original petrophysic characteristics the results show that the highest porosity and permeability occur in rocks with quench fractured glasses and in non welded ignimbrites with gas pipe structures followed by autobrecciated rhyolites welded ignimbrites massive glasses and fresh rhyolites have the lowest permeabilities the new data indicate that tectonic fracturing is not as significant as was considered before and application of these concepts are relevant in the assesment of volcanic reservoir quality

searching for eustasy in deglacial sea level histories abstract perturbations to the earth s gravity field and solid surface associated with glacial isostatic adjustment gia cause the total observable sea level change to depart from the eustatic curve which is defined as a spatially uniform height shift of the ocean surface to accommodate any mass gained lost from grounded ice in this study we apply a state of the art model of gia induced sea level change to quantify the magnitude and spatial form of this departure at the global scale for a range of model parameters with an aim to identify regions that are well suited to obtain accurate and precise estimates of eustatic sea level and therefore past grounded ice volume in general our results indicate that eustatic sea level is not a directly measurable quantity and so must be estimated by subtracting a model derived estimate of non eustatic contributions from observations in this regard we use our results to isolate regions where this procedure can be applied with optimal accuracy and precision that is where 1 the gia predictions are relatively insensitive to plausible ranges in input parameters and 2 where the non eustatic contribution is small i e the predicted sea level closely approximates the eustatic value we present maps that can be employed by the field community to identify areas where sea level reconstructions would be well suited to arrive at robust estimates of eustatic sea level note that sea level changes associated with tectonic motion and changes in ocean water temperature salinity which also lead to departures from eustasy are not considered in this analysis

the temporal and spatial scales of rocky coast geomorphology a commentary rocky shores are complex landforms that result from marine erosion and subaerial weathering they are time integrated features where their present day form is the result of instantaneous erosion often on the millimetre to sub metre scale occurring for centuries to millennia as a result research on rocky coasts focuses on a range of temporal and spatial scales from granular scale swelling of a rock surface and instantaneous wave impact to modelling millennial scale sea level drivers the challenge for rocky coast researchers is either to upscale or to downscale their results to the human timescales of greatest interest to managers the research presented in earth surface processes and landforms over the past 3 years highlights the range of spatial and temporal approaches to the study of coastal cliffs and shore platforms we identify a key temporal and spatial gap in current research seasonal annual timeframes over hundreds of metres to kilometre scale studies appear to be lacking and are likely critical in understanding the future evolution of rocky coasts especially their response to climate change copyright 2017 john wiley sons ltd

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

a guide to current uses of vertical seismic profiles vertical seismic profiles vsps are small scale seismic surveys in which geophones are lowered into a well to record waves traveling both down into the earth direct waves from the surface source and downgoing multiples and back toward the surface primary reflections and upgoing multiples vsps thus contain information about the reflection and transmission properties of the earth with a coverage that depends upon the geometry of the vsp experiment and the structure near the well this article describes the uses of vsps in seismic exploration that have been published in the last three years and is designed to complement the more detailed surveys by hardage 1983 and balch and lee 1984 when the earth is horizontally layered the well is vertical and the source is close to the wellhead upgoing and downgoing waves recorded by the vsp travel vertically and the vsp can be used to calibrate surface seismic sections by providing the time to depth curve and allowing a detailed analysis of reflection and

middle to late holocene relative sea level changes at puerto deseado patagonia argentina stratigraphic morphologic and radiocarbon data from puerto deseado coastal area santa cruz province argentina indicate that the holocene coastline formed in response to the discontinuous aggradation of coarse gravely beaches since c 6300 cal yr bp related to a progressive falling of relative sea level beach ridge crests crudely approximate to the sea level showing at least three steps of aggradation and relative sea level lowering two inactive abrasive notches at c 7 9 and 3 4 m a s l have recorded this sea level trend suggesting two important phases when sea level was stationary this allows the estimation of a rate of relative sea level fall in the last c 3500 years of c 1 8 mm yr moreover notches and morphological data indicate that the crest of the beach ridges exceeded the sea level height by c 2 0 5 m this value provides a reasonable regional estimate to be applied to produce comparable relative sea level curve for atlantic patagonia coast

n view reconstruction a new method for morphological modelling and deformation measurement in volcanology abstract we present a method of reconstructing volcanic morphology using multiple digital views n view captured at different angles around an object this approach uses recent advances in the field of computer vision to provide accurate 3 d measurements of volcanic surfaces videogrammetry digital image reconstruction is used as it is best adapted to numerical processing the method is tested and now used in the laboratory on analogue volcanic cones the method begins with calibrating the camera and finding image positions using an accurate n view calibration method this is done by estimating internal and external parameters of the camera using several views of a specially constructed calibration target the n view reconstruction of the real object is then done by iteratively deforming an initial theoretical model of the surface laboratory tests show that reconstruction accuracy is about 10 4 m for a distance between the object and the camera of 0 5 m and is potentially several orders of magnitude higher for surfaces of finer texture and using higher precision sensors this is easily high enough to be useful for the accuracy required for morphological studies it is also sufficient for monitoring most types of volcano deformation the technique has the potential to detect morphology changes of the order of mm use of the method in the field requires a slightly different approach from that in the laboratory textures and lighting are more variable and the sensor and ground control point location and model calibration must be done differently we provide case studies from laboratory tests and qualitative image analysis for two field cases piton de la fournaise indian ocean and santaguito guatemala these illustrate the technique s potential and explore problems of field application using current sensors the method has the potential to provide sufficient precision for fine mm cm scale reconstruction and will represent a valuable simple and flexible tool when compared with classical stereophotogrammetry techniques

stress orientation inferred from shear wave splitting in basement rock at cajon pass s waves generated by mode conversion of p waves from surface compressional sources and recorded by oriented geophones at depths between 1300 and 1820 meters in the cajon pass scientific drillhole arrive at higher apparent velocities when polarized along the direction n70 e than when polarized in the orthogonal direction the observed polarization dependent velocities are consistent with seismic anisotropy due to in situ fractures or cracks that are preferen tially aligned n70 e subnormal to the san andreas fault this result is consistent with the maximum principal horizontal stress direction at cajon pass also being subnormal to the san andreas fault

site amplifications for generic rock sites seismic shear wave velocity as a function of depth for generic rock sites has been estimated from borehole data and studies of crustal velocities and these velocities have been used to compute frequency dependent amplifications for zero attenuation for use in simulations of strong ground motion we define a genetic rock site as one whose velocity at shallow depths equals the average of those from the rock sites sampled by the borehole data most of the boreholes are in populated areas for that reason the rock sites sampled are of particular engineering significance we consider two genetic rock sites rock corresponding to the bulk of the borehole data and very hard rock such as is found in glaciated regions in large areas of eastern north america or in portions of western north america the amplifications on rock sites can be in excess of 3 5 at high frequencies in contrast to the amplifications of less than 1 2 on very hard rock sites the consideration of unattenuated amplification alone is computationally convenient but what matters for ground motion estimation is the combined effect of amplification and attenuation for reasonable values of the attenuation parameter k 0 the combined effect of attenuation and amplification for rock sites peaks between about 2 and 5 hz with a maximum level of less than 1 8 the combined effect is about a factor of 1 5 at 1 hz and is less than unity for frequencies in the range of 10 to 20 hz depending on t using these amplifications we find provisional values of about ao 70 bars and k 0 0 035 sec for rock sites in western north america by fitting our empirically determined response spectra for an m 6 5 event to simulated values the borehole data yield shear velocities 033o of 618 and 306 rrdsec for rock and soil sites respectively when averaged over the upper 30 m from this we recommend that v30 equals 620 and 310 m sec for applications requiring the average velocity for rock and soil sites in western north america by combining the amplifications for rock sites and the site factors obtained from our analysis of strong motion data we derive amplifications for sites with 17 3o 520 m sec nehrp class c corresponding to a mix of rock and soil sites and v3o 310 and 255 m sec average soil and nehrp class d sites respectively for the average soil site the combined effect of amplification and attenuation exceeds a factor of 2 0 for frequencies between 0 4 and about 4 hz with a peak site effect of 2 4 the peak of the nehrp class d site effect is 2 7

fracture detection using p wave and s wave vertical seismic profiling at the geysers in a pilot vertical seismic profiling study p wave and cross polarized s wave vibrators were used to investigate the potential utility of shear wave anisotropy measurements in characterizing a fractured rock mass the caprock at the geysers geothermal field was found to exhibit about an 11 percent velocity variation between sh waves and sv waves generated by rotating the s wave vibrator orientation to two orthogonal polarizations for each survey level in the well the effect is generally consistent with the equivalent anisotropy expected from the known fracture geometry

evaluation of anisotropy by shear wave splitting the polarizations of three component shear wavetrains carry unique information about the internal structure of the rock through which they pass specifically commonly observed shear wave splitting may contain information about the orientation of crack distributions this information cannot usually be recovered from shear waves recorded at the free surface because of interference with the interaction of the shear wave with the surface even for nearly vertical incidence however shear wave splitting in synthetic three component vertical seismic profiles in some cases may be interpreted directly in terms of the direction of strike of vertical cracks because the human eye is not skilled at identifying the phase relationships between three component seismograms played out conventionally as parallel time series the polarizations are displayed in orthogonal sections of the particle displacements to facilitate recognition and evaluation of the shear wave splitting estimating the orientations of cracks an

evidence of large prehistoric offshore earthquakes deduced from uplifted holocene marine terraces in pangasinan province luzon island philippines abstract uplifted holocene marine terraces in pangasinan province westernmost luzon island philippines are reported here for the first time as geomorphic evidence of large prehistoric offshore earthquakes we recognized up to three holocene terrace steps elevations of shoreline angles are ti 1 to 5 m tii 2 to 7 m and tiii 4 to 11 m above mean sea level amsl the lateral variation in the elevation of terrace steps indicates differential uplift along the coast the staircase topography characterized by horizontal abrasion platforms meter scale terrace risers and wave cut notches suggests that these geomorphic features were formed by large coseismic uplift events terrace morphology and radiocarbon ages further suggest that at least three coseismic coastal uplift events have occurred since the culmination of the post glacial sea level rise 6000 years ago we interpret tiii to be the holocene transgressive surface 6000 ybp and estimated a maximum uplift rate of 1 7 mm yr which is almost the same as the late pleistocene uplift rate of 1 3 mm yr we infer that proximity to offshore seismic sources has contributed to the deformation pattern of holocene terraces and variation in the number of terrace steps uplift patterns of marine terraces also suggest that the magnitude and location of prehistoric earthquakes may have varied between individual coseismic uplift events we conducted simple elastic dislocation modeling to evaluate the source parameters of the causative faults our preliminary models show that a landward dipping offshore reverse fault located at the base of a steep slope separating the fore arc basin and continental shelf could be responsible for coastal uplift along the western pangasinan peninsula

holocene tectonic uplift patterns in northeastern sicily evidence from marine notches in coastal outcrops abstract marine notches are groove like features formed in rocky coastal outcrops in relation to past sea levels and are widely used as indicators of rates and patterns of tectonic activity examination of uplifted notches in the complex plate boundary setting of northeast sicily reveals the need for considerable care in their interpretation present notch forming processes are dominated by carbonate dissolution aided by microbial activity as waves surge and recede at the base of the cliffs and produce notches approximately 0 5 m above present biological mean sea level i e above an organic constructional rim of coralline algae used to define sea level at sea level dissolution is restricted through saturation and the bedrock protected by the outbuilding algal rim this assemblage varies in response to fetch exposure and uplift rate typically producing a complex band of uplifted notch features exposed above sea level correlations based on height of the shallow and discontinuous notch indentations within this band are unreliable however the upper margin of the band marked by the roof of the uppermost notch is a prominent and laterally persistent feature easily recognised as the boundary between subaerial and marine processes we propose that this is an approximately coeval datum formed when post glacial sea level rise decelerated in the mid holocene to match the rate of tectonic uplift a notion strengthened by the available dates of about 5 ka for this feature subsequent uplift outpaced later sea level rise taking the notches above sea level this proposed datum varies in height from about 2 m at capo milazzo on the north coast to about 5 m on the east coast bordered by the messina fault system the height differential is consistent with the respective elevations of nearby marine terraces dating from the last interglacial at about 125 ka but also exhibits shorter term variations suggesting holocene increases in activity rates on more localised structures affecting the localities involved regionally northeast sicily is characterised by long term differential uplift rather than behaving as a coherent block the highest uplift rate probably exceeding 2 mm a 1 calculated using the sea level curve from fairbanks r g 1989 a 17000 year glacio eustatic sea level record influence of glacial melting rates on the younger dryas event and deep ocean circulation nature 342 637 642 is suggested for a notch locality on the upthrown side of the malta escarpment rates of about 2 mm a 1 are indicated by the 5 m notch at localities bordered by the messina fault system and a rate close to 1 mm a 1 is suggested for the undated 2 m notch at capo milazzo

modeling the accumulation and dynamics of beaches on shore platforms a mathematical model was used to study the development and dynamics of beaches on shore platforms the model was based on assumptions that the gradient of the beachface at its seaward edge must be greater than platform gradient beach sediment tends to move landwards and beach occurrence and extent depends upon the amount of sediment available equilibrium beachface gradient was related to breaker height wave period and sediment grain size three grain sizes were used representing fine and coarse sand and pebble two deep water wave sets representing storm wave and west coast swell wave environments and two tidal ranges of 9 1 and 3 3 m runs were made using linear concave and convex platform profiles with gradients ranging between about 0 6 and 8 because platform and beachface gradients are normally quite similar shore platforms are unable to store much sediment for a linear platform with a lower gradient than the beachface sediment first accumulates at the cliff base and then depending on the sediment available extends increasingly seawards beach development first occurs on the gently sloping seaward portions of concave platforms and on the more landward portions of convex profiles the amount of available material partly determines the landward and seaward extent of these beaches respectively although it is also controlled by beachface and platform gradients beaches on shore platforms become thinner and more gently sloping during storms and they may disappear completely depending on such factors as sediment grain size platform gradient the amount of sediment that can be stored during calm conditions wave characteristics and the duration of the storm the response of beaches on rocky coasts to rising sea level will be different from those on sedimentary coasts and will depend in part on the morphology of the rocky foundation

esr dating stratigraphically well constrained marine terraces along the patagonian atlantic coast argentina abstract esr dating of marine mollusc shells is an important tool in coastal geomorphology as well as in palaeosea level and other research some severe problems however remain as far as the accuracy of the dating results are concerned case studies of patagonian middle and younger quaternary marine terraces help to illustrate the potential of an improved esr dating technique it can be demonstrated that a discrimination of holocene last interglacial penultimate interglacial and older samples is possible a chronostratigraphic separation of the well known last interglacial substages 5a 5c and 5e is still missing partly due to the misleading accuracy of esr dating results consequently it cannot be decided yet whether the morphologically well conserved last and penultimate interglacial age substages result from a relative sea level fall glacioeustatic and or decreasing wind intensities during the one and the same interglacial highstand shortly after the 5e or 7 transgression maximum or whether they were deposited during the much younger sea level sub highstands e g 5c 5a or 7c or 7a

innovative tidal notch detection using tls and fuzzy logic implications for palaeo shorelines from compressional crete and extensional gulf of corinth tectonic settings abstract tidal notches are a generally accepted sea level marker and maintain particular interest for palaeoseismic studies since coastal seismic activity potentially displaces them from their genetic position the result of subsequent seismic events is a notch sequence reflecting the cumulative coastal uplift in order to evaluate preserved notch sequences an innovative and interdisciplinary workflow is presented that accurately highlights evidence for palaeo sea level markers the workflow uses data from terrestrial laser scanning and iteratively combines high resolution curvature analysis high performance edge detection and feature extraction based on the assumptions that remnants such as the roof of tidal notches form convex patterns edge detection is performed on principal curvature images in addition a standard algorithm is compared to edge detection results from a custom fuzzy logic approach the results pass through a hough transform in order to extract continuous line features of an almost horizontal orientation the workflow was initially developed on a single distinct and sheltered exposure in southern crete and afterwards successfully tested on laser scans of different coastal cliffs from the perachora peninsula this approach allows a detailed examination of otherwise inaccessible locations and the evaluation of lateral and 3d geometries thus evidence for previously unrecognised sea level markers can be identified even when poorly developed high resolution laser scans of entire cliff exposures allow local variations to be quantified edge detection aims to reduce information on the surface curvature and hough transform limits the results towards orientation and continuity thus the presented objective methodology enhances the recognition of tidal notches and supports palaeoseismic studies by contributing spatial information and accurate measurements of horizontal movements beyond that recognised during traditional surveys this is especially useful for the identification of palaeo shorelines in extensional tectonic environments where coseismic footwall uplift only 1 2 to 1 4 of net slip per event is unlikely to raise an entire notch above the tidal range

analysis of states of stress between provinces of constant stress recent studies have indicated the existence of crustal provinces or domains within which the state of stress shows little apparent horizontal variation between provinces the state of stress may undergo substantial changes often over remarkably short distances as analyzed here the transition in stress state between adjacent domains is caused by shear tractions acting on the base of the elastic brittle layer and is mediated by a stress field within a zone between the provinces that can be determined by solving the equations of force equilibrium and stress compatibility the component of horizontal stress oriented perpendicular to the provincial boundary changes smoothly across the transition zone from one province to the other whereas the horizontal stress oriented parallel to the boundary shows smaller but discontinuous changes the horizontal component of shear stress is unlikely to change from one province to another because of the implausible nature of the required basal traction thus in this regard states of stress in adjacent domains appear to be coupled the coincidence of a number of stress transition zones with boundaries defined by heat flow suggests that in many cases the basal tractions are the result of thermally induced mass transport below the elastic brittle layer in the direction of increasing horizontal compressive stress this analysis provides a quantitative relationship between changes in the stress field measured in the upper portion of the crust and shear stresses acting on the base of the elastic brittle layer

last interglacial sea level high stand deduced from well preserved abrasive notches exposed on the galilee coast of northern israel abstract this study investigates the morphometry and structure of abrasive notches exposed along the tectonically stable micro tidal galilee coast israel south eastern mediterranean since they can serve as past sea level indicators the characteristics of the notches height h vertex d distance of maximum retreat point from cliff face height of retreat point from the floor and roof h f and h r respectively etc were surveyed using lidar and a digital laser rangefinder and elevations were measured using dgps rock resistance was measured by schmidt hammer tests which show that the most developed and best preserved notches were formed within the more resistant host rocks of the cenomanian chalk and the pleistocene aeolianite sandstone the elevations of the abrasive floors of the exposed notches indicated a sea level slightly higher than at present at the beginning of mis5e with an upper limit between 0 5 and 0 75 m the morphometry of the mis5e notches which are larger than modern notches in the study area suggests mechanical erosion by broken waves where an energetic wave dominant sea batters a sheltered coastal cliff two sub units of mis5e the yasaf mb were deposited within the notches a a conglomerate containing the diagnostic fossil strombus bubonius which was found on the notch floor and b a younger bioclastic sandstone sub unit which fills and covers parts of the notches these unique field relationships link the formation of the notches to the beginning of mis5e indicating an erosive phase which parallels large scale mis5e sea level evidence suggesting relatively long stand stills at an elevation of about 1 m the early mis5e erosive phase was followed by a depositional phase during the later stage of mis5e

acquisition and preliminary analysis of oriented multi component multioffset vsp data dosecc cajon pass deep scientific drillhole in october 1987 a four offset vsp vertical seismic profile was acquired at the cajon pass deep scientific drillhole preliminary velocity analysis of the p wave direct arrival has identified zones in the upper crystalline section of the borehole where interval velocities derived from a long spaced sonic log differ greatly from the vsp interval velocities large velocity differences were observed between the three near offset vsps in the upper crystalline section of the borehole these differences are interpreted as being associated with the complex geologic structure near the cajon pass borehole two source positions one 35 m from the borehole and one 346 m from the borehole were used to analyze the horizontal component holograms of the p wave direct arrival the near offset hodograms exhibited particle motion directions which were not coincident with the vsp source direction when the downhole receiver was in crystalline rock the far offset hodograms exhibited particle motion directions which were generally consistent with the source direction

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

flexure of the crust estimated from in situ stress measurements and its relation to tectonics abstract in a previous study the author proposed a numerical method to estimate the static flexure of the uppermost crust and the force causing the flexure he applied the method to in situ stress data measured in the kanto tokai area where the active margin of three tectonic plates meet and estimated the static flexure and the force causing the flexure he found that the estimated flexure is consistent with the tectonics of the area and that it is caused by the subduction of the philippine sea plate the present paper presents the solution to the problem of the reference state of stress which remained unsolved in the previous study the previous results are reviewed in the light of additional information and the following conclusions are reached 1 1 the vertical cross section of the estimated flexure shows a good resemblance to that of the vertical deformation of the earth s surface numerically estimated from a two dimensional finite element model which calculate the influence on the japanese islands of the drag along the interface between the islands and the descending oceanic plate from a rough comparison it is inferred that the accumulated drag on the interface is 1 2 km 2 2 the vertical movement in recent years around the kanto tokai area shows a positive correlation with the estimated static flexure suggesting that stress is presently accumulating

multiply polarized shear wave vsps from the cajon pass drillhole a 3 component vsp data set was acquired in the cajon pass drillhole with a multiply polarized shear wave source and a conventional p wave source producing a 9 component data set the vsp data show effects on the full wavefield from the sediment granite interface mode converted waves are identified with significant scattering of s wave energy from the leading p wavefront hodographs are used to display s wave particle motions in two dimensions shear wave splitting is observed in the hodographs the shear wave particle motion is used to infer anisotropy orientation with respect to the local strike of the san andreas fault stress induced fracturing is assumed to be a possible cause of the shear wave splitting a variation of particle motion orientation with depth is observed implying a variation in anisotropy orientation as a function of depth

abrasive notches along the atlantic patagonian coast and their potential use as sea level markers the case of puerto deseado santa cruz argentina patagonia argentina is a key area for the study of sea level changes in the southern hemisphere but the availability of reliable sea level markers in this area is still problematic in fact the storm deposits beach ridge commonly used here to reconstruct past sea level oscillations introduce a wide error along the puerto deseado coast santa cruz morphometric analyses of 11 features were carried out using traditional measurement tools and a digital software based method tested on one selected feature with the aim to investigate the possibility of their use as sea level markers by undertaking accurate topographic profiles we identified the relationship between notches and current sea level in detail we identified two clusters of notch retreat point elevations with a very low internal variability the lower was located a little below the mean high tide level mht and the upper located at least 0 5 m above the maximum high tide level mht field observations of tidal levels and the position of notches suggest that the lower notches are active and the upper are inactive this study on the abrasive notches attests their quality as sea level markers and opens up the use of fossil abrasive notches as palaeo sea level markers because the error linked to these features is substantially smaller than that introduced by beach ridges commonly used in the study area copyright 2014 john wiley sons ltd

regional correlations of vs30 and velocities averaged over depths less than and greater than 30 meters using velocity profiles from sites in japan california turkey and europe we find that the time averaged shear wave velocity to 30 m vs30 used as a proxy for site amplification in recent ground motion prediction equations gmpes and building codes is strongly correlated with average velocities to depths less than 30 m vsz with z being the averaging depth the correlations for sites in japan corresponding to the kik net network show that vs30 is systematically larger for ag ivenvsz than for profiles from the other regions the difference largely results from the placement of the kik net station locations on rock and rocklike sites whereas stations in the other regions are generally placed in urban areas underlain by sediments using the kik net velocity profiles we provide equations relating vs30 to vsz for z ranging from 5 to 29 m in 1 m increments these equations and those for california velocity profiles given in boore 2004b can be used to estimate vs30 from vsz for sites in which velocity profiles do not extend to 30 m the scatter of the residuals decreases with depth but even for an averaging depth of 5 m a variation in logvs30 of 1 standard deviation maps into less than a 20 uncertainty in ground motions given by recent gmpes at short periods the sensitivity of the ground motions to vs30 uncertainty is considerably larger at long periods but is less than a factor of 1 2 for averaging depths greater than about 20 m we also find that vs30 is correlated with vsz for z as great as 400 m for sites of the kik net network providing some justification for using vs30 as a site response variable for predicting ground motions at periods for which the wavelengths far exceed 30 m online material estimates of vs30 at k net stations

direct determination of tidal levels for engineering applications based on biological observations abstract the scarcity of tide gauges in a global scale and the variability of the tidal levels along contiguous coasts mainly due to changing hydrographic conditions make the determination of tidal levels especially of the mean sea level not an easy task determination of such levels with a precision of about 10 cm necessary for most coastal engineering works is usually based on records of temporary tide gauges or on geomorphological techniques in this paper we present an alternative approach permitting to accurately identify tidal levels with a precision suitable for civil engineering applications based on biological observations on rocky shores including breakwaters and quays more specifically we present evidence that the biological zonation i e the distribution of coastal species in well defined sub horizontal belts is practically insensitive to seasonal and other small scale fluctuations of the sea level and is clearly related to certain levels mostly the mean low water mlw this approach somewhat similar to what has been used in the past for instance for the determination of the geodetic vertical datum in the republic of venice italy till approximately ad 1800 permits direct determination of the mean sea level or of other tidal levels on the basis of biological observations without statistical analyses of tide gauge records with an accuracy of 5 10 cm especially in microtidal low energy coasts

shear wave splitting in the anza seismic gap southern california temporal variations as possible precursors shear wave splitting above small earthquakes in the anza seismic gap on the san jacinto fault southern california displays the effective anisotropy of vertical fluid filled microcracks the delays between the split shear waves increase significantly over the 3 years of available records at the only station with arrivals from a wide range of azimuths and angles of incidence these changes can be modeled by increasing the aspect ratio bowing of stressoriented microcracks which is one of the expected elastic effects of an increase of stress on a rock mass containing a distribution of fluid filled microcracks this is the first time that temporal variations of shear wave splitting have been observed and suggests that shear wave splitting can be used to monitor the detailed changes in the buildup of stress before an earthquake

marine notches in coastal cliffs indicators of relative sea level change perachora peninsula central greece abstract in several sites in the complex faulted western part of perachora peninsula central greece three principal marine notches in rocky coasts are present in each site no holocene notches occur above the upper of the three notches only subaerial weathering affected the rocks lateral variation in the heights of notches demonstrates differential uplift due to fault control and illustrates the complexity of application of marine notches in interpretation of tectonic history the lower undated notch is prominent in places coincides with modern sea level and is interpreted to be forming now it suggests that the western part of the peninsula has been stable for a considerable time the middle and upper notches vary in height between sites and may not be time equivalent but represent earlier sea level positions in the harbour adjacent to the heraion archaeological site the middle and upper notches are preserved in most places as notch roofs so that gradual uplift led to removal of notch floors by physical chemical and biotic processes in exposed locations however within a few hundred metres west of the harbour four uplifted plus a fifth forming now notches have been illustrated by pirazzoli et al tectonophysics 229 1994 201 that cannot be readily correlated to the harbour site and indicate differential uplift by fault displacement in a more complex situation at mylokopi 6 km ne of heraion three different notch profiles occur in three blocks separated by two faults however within the central block of the three two very different profiles are preserved only tens of metres apart beneath one continuous upper notch roof at the same height this complex arrangement interpreted as variability of exposure to marine processes on different parts of this irregular embayment such that one profile containing three notches was controlled largely by abrasion and formed notches that are vertically more extensive while the other profile containing five narrow notches formed by dissolution and or biological erosion at the same time in the protected east end of the block however if only one or the other profile was visible very different tectonic interpretations would result the bedrock of perachora peninsula also shows important variations in resistance to erosion affecting the resulting notch profiles and some sites are influenced by structurally controlled differential subaerial weathering forming ridges and grooves giving the false impression of extra minor notches the distinction between dissolution controlled and structure controlled minor notches may not be possible in some places the interpretations of notch profiles can be highly complex and influence views of tectonic history in a given region overall the occurrence of three principal notches beneath one uplifted notch roof in several sites indicates that a holocene uplift rates outpaced post glacial sea level rise b there were three principal periods of relative sea level stillstand affecting the perachora peninsula and c uplift of the entire western part of the perachora peninsula is an important component of its tectonic processes probably more important than fault movement within the peninsula

shear wave anisotropy in the parkfield varian well vsp abstract a vertical seismic profile vsp survey was run to 1334 m depth in the instrumented varian well 1 4 km from the san andreas fault trace at parkfield california to test the sensor string shortly after its permanent installation the cable subsequently failed near the 1000 m level so the test survey represents the deepest data acquired in the study a shear wave vibrator source was used at three ofsets and two orthogonal orientations and the data have been processed for p and s wave velocities and for s wave velocity anisotropy velocities are well determined 3 3 and 1 9 km sec respectively at the deeper levels and the s waves are seen clearly to be split by anisotropy below about 400 m some 8 per cent velocity difference is apparent between polarizations parallel to and perpendicular to the san andreas fault faster and slower respectively and the difference seems to decrease with distance from the fault suggesting that the cause may be the fabric of the fault zone repeated surveys at the 1000 m depth are being conducted as part of the parkfield monitoring program

hydraulic fracturing stress measurements and in situ stress field in the kanto tokai area japan abstract hydraulic fracturing stress measurements have been made in fifteen boreholes of various depths from 100 to 800 m in the kanto tokai area since 1978 about 90 sets of in situ stresses have been obtained successfully the maximum and minimum horizontal compressive stresses increase linearly with depth in each borehole the difference between the maximum and minimum principal stresses also increases with depth the increase of stress difference with depth is interpreted in terms of large stress relaxation in shallow parts of the boreholes where low confining pressure and many pre existing microcracks are dominant the maximum shear stress at a depth of 400 m ranges from 1 to 8 mpa depending on the site it is not always the case that the regions of small shear stresses are inactive in microseismicity and crustal movement this phenomenon is attributed to the relaxation of shear stress at the measured depths and to the regional variation in increasing rate of shear stress the maximum compressive stress direction is obtained from detection of the fracture azimuth after hydraulic fracturing stress direction measured at each borehole agrees well with that estimated from geologic and seismic methods near the measurement site several stress provinces where the stress directions appear almost uniform are defined in the kanto tokai area the regional distribution of the stress directions is understood in terms of the relative movement of three plates the philippine sea pacific and eurasian plates which are in contact with each other in this area

coastal notches their morphology formation and function deep coastal notches develop through undercutting of steep coastal slopes consisting of rocks that are strong enough to support the weight of the overburden notches are found from the tropics to the poles and in a wide range of rock types virtually tideless to megatidal seas and high to low wave energy environments the emphasis in the literature has been on notches in calcareous rocks in warm microtidal seas and with the general assumption that they have been produced by bioerosion or chemical dissolution few scientifically rigorous attempts have been made to determine the processes responsible for notch formation in different environments and rock types however or to determine whether different processes produce distinct notch morphologies within the same tidal and wave environments the use of notches as palaeo sea level markers and to determine rates of tectonic uplift has been particularly important in the mediterranean notches are more difficult to employ for this purpose in the middle latitudes where higher waves and tides amplify the range of elevations over which the erosional mechanisms are effective as well as increasing the exposure and effect of rocks of variable resistance to erosion to maximize the utility of notches as sea level markers and to better understand and model their development in a wide range of environments we need to understand and be able to quantify the relationship between notch shape and size and the elevational efficacy of the various erosional processes

three dimensional imaging of steeply dipping structure near the san andreas fault parkfield california shot gathers from the parkfield california deep crustal seismic reflection line recorded in 1977 by cocorp reveal coherent events having horizontal to reverse moveouts these events were migrated using a multioffset three dimensional kirchhoff summation method this method is a ray equation back projection inversion of the acoustic wave field which is valid under the born wkbj and far field assumptions migration of full wave acoustic synthetics having the same limitations in geometric coverage as the cocorp survey demonstrates the utility of the imaging process the images obtained from back projection of the survey data suggest that the gold hill fault carries ultramafic rocks from the surface to 3 km depth at a dip greater than 45 degrees where it joins the san andreas fault which may cut through more homogeneous materials at shallow depths to the southwest a 2 km tertiary sedimentary section appears to terminate against a near vertical fault the zone between this fault and the san andreas may be floored at 3 km by flat lying ultramafics lateral velocity inhomogeneities are not accounted for in the migration but in this case do not seriously hinder the reconstruction of reflectors

modelling holocene relative sea level observations from the caribbean and south america abstract holocene data from the caribbean and the atlantic coast of south america have been critically assessed and a subset of the best quality data are presented these data cover a large north south geographic extent and display a distinct spatial variation we make the first comparisons of this data set to predictions based on a realistic model of glaciation induced sea level change with the main aims of understanding the cause of the observed spatial trend and estimating a eustatic signal for the holocene the spatial variation is dominated by the influence of the ice and ocean mass redistribution on sea level change with the ice induced effect dominating the observed north south trend a best fitting model is applied to estimate a holocene eustatic signal from the observations we find that the model corrected data are consistent with a relatively rapid rise of 7 8 mm yr in the early holocene with a marked reduction in this rate around 7 cal kyr bp from this time until present the model corrected data suggest that the volume of mass transfer between ice sheets and oceans was no more than 1 m eustatic sea level equivalent

paleoshoreline record of relative holocene sea levels on pacific islands abstract understanding the history of relative holocene sea levels on pacific islands is important for constraining fundamental geodynamic theories interpreting the environments of early human occupation sites and forecasting future environmental conditions on the islands an observational paleoshoreline record is provided by emergent paleoshoreline indicators formed at higher relative sea levels hence standing at higher elevations than modern counterparts emergent paleoshoreline notches in limestone seacliffs record paleo high tide levels and emergent paleoreef flats record paleo low tide levels whereas emergent paleobeachrock locally records paleo intertidal levels both paleonotches and paleoreefs occur along the coasts of high standing islands exposing volcanic bedrock and uplifted reef complexes but low lying coralline atolls lack sufficient relief to preserve paleonotches controls on relative holocene sea level include global eustatic and regional hydro isostatic changes in ambient sea level relative to island landmasses and shifts in the elevations of islands relative to sea level caused by thermal subsidence of the oceanic lithosphere or thermally rejuvenated loci of hotspot volcanism by flexure of the lithosphere under the load of growing volcanic edifices hawaii samoa society islands by arching of the lithosphere over trench forebulges loyalty islands niue bellona rennell and by tectonism within forearc belts between active volcanic chains and trenches mariana islands tonga vanuatu the dominant pattern of relative sea level change where not overprinted by local tectonism or lithospheric flexure was a uniform early holocene rise in eustatic sea level followed by a regionally variable late holocene hydro isostatic drawdown in sea level the resultant was a mid holocene highstand in relative sea level that affected the development of shoreline morphology throughout the tropical pacific ocean the earliest human migrations into intra oceanic island groups of both the northwestern and southwestern pacific ocean followed close on the heels of the mid holocene sea level highstand and took advantage of newly attractive coastal environments engendered by sea level drawdown the effects of the mid holocene highstand were modified to varying degrees in different island groups by geodynamic uplift or subsidence

microearthquake s wave observations from 0 to 1 km in the varian well at parkfield california abstract high gain three component seismometers from 0 to 1 km deep along the varian a 1 well at parkfield california were used to record the waveforms of nearby microearthquakes despite being in the thick tertiary sediments of the parkfield syncline the s wave amplification at this site is only about a factor of 3 the spectral content and spectral ratios of s waves along the well show that the average qs in the top 1 km at this site is 37 with the qs in different subintervals varying between 8 and 65 based on initial s wave polarizations a complex s wave velocity structure must exist at and below the varian site this structure appears to include position dependent anisotropy as well as steep lateral velocity gradients at a depth of 1 km s wave splitting parallel and normal to the san andreas fault zone is consistently observed this splitting scales at roughly 0 01 sec km subsequent to the split s waves the particle motion seems to be controlled by event focal mechanism above 1 km the upgoing s waves attenuate and change directions of polarization with a new splitting rate of 0 1 sec km uniquely for some events on the san andreas fault immediately below the varian site large post s wave signals with normal dispersion are present we propose that these phases are fault zone guided waves channeled from the san andreas fault to the varian site along the gold hill fault

radiation patterns of a shear wave vibrator in near surface shale two shallow surface to borehole field tests were conducted to investigate the radiation patterns of a shear wave vibrator in near surface shale in the in line direction for which baseplate motion is transverse to the source geophone raypath the vibrator produces a broadband high amplitude signal of the sh type and virtually no signal of the sv or p types the amplitude of the sh radiation is approximately constant as a function of polar angle but it falls off as the cosine of the azimuthal angle measured with respect to the in line direction in the broadside direction the vibrator produces a strong uncontaminated signal of the sv type the radiation pattern of the sv signature is lobate in the polar plane and peaks at an incident angle of 30 to 35 degrees in the horizontal plane the sv radiation varies as the sine of the azimuthal angle measured with respect to the in line direction the field tests were conducted on a permian shale in oklahoma and an eocene shale in east texas comparison between sh and sv wave surfaces indicates that both shales behave approximately like transversely isotropic solids with a vertical axis of symmetry theoretical wave surfaces are fit to the observed data by using elastic moduli determined from the field measurements and by making the assumption that the near surface shale at each field site is a single homogeneous inherently transversely isotropic material the analyses indicate that horizontal sh group velocity is about 30 percent greater than horizontal sv group velocity in the permian shale and about 25 percent greater in the eocene shale

p wave spectra for ml 5 foreshocks aftershocks and isolated earthquakes near parkfield california abstract wood anderson seismograms recorded at mount hamilton mhc 185 km 327 santa barbara sbc 180 km 158 and tinemaha tin 240 km 56 provide data for comparing p wave spectra for two immediate 17 min foreshocks one early 55 hr foreshock two aftershocks and two isolated parkfield earthquakes all are m l 5 0 shocks with epicenters within 7 km of the common epicenter of the 1934 and 1966 parkfield main shocks the set of events is well suited for testing the hypothesis that foreshocks are high stress drop sources calculated stress drops are controlled by source directivity at azimuths aligned with the fault break at mhc and sbc p wave radiation from the three foreshocks is focused along one fault trace azimuth suggesting that foreshock sources are characterized by pronounced unilateral rupture expansion at tin broadside to the fault where directivity has minimum effect on calculated relative stress drop the two immediate foreshocks are higher stress drop sources the early foreshock is a low to average stress drop source indicating the possibility that stress concentration is a rapidly occurring phenomenon in rupture nucleation alternatively the stress field is highly variable on the scale of 2 to 3 km in the focal region of an impending earthquake with a rupture length of 20 to 30 km

quaternary marine terraces sea level changes and uplift history of patagonia argentina comparisons with predictions of the ice 4g vm2 model of the global process of glacial isostatic adjustment abstract quaternary marine terraces have been investigated along a 1000 km stretch of the coast of argentinian patagonia fossil mollusc shells most in living position and collected from raised beaches were dated using the u series esr and 14 c methods our analyses show that holocene sea level in this region culminated 7000 to 8000 bp at 6 7 m amsl this beach slightly increases in altitude southward the last interglacial stage 5e was identified at 16 17 m amsl whereas the highest and morphologically most distinctive radiometrically dated terrace at 250 000 to 330 000 bp exists at an elevation of 33 35 m amsl we estimate a constant rate of tectonic uplift of 0 09 m 1000 yr since the middle pleistocene using this estimate of the local rate of tectonic uplift we correct relative sea level r s l observations for the holocene epoch in turn the inferred holocene sea level histories are compared with those predicted using the ice 4g vm2 model of the global process of glacial isostatic adjustment this model accurately predicts r s l history from all sites along the northern part of the east coast of the south american continent venezuela brazil however along the southern part of the coast of argentinian patagonia there is evidence of an influence that is not accurately represented in this version of the model of the global process of glacial isostatic adjustment we suggest that this influence could be connected to the presence of the broad continental shelf that is located offshore of this region but the influence of significant neotectonic uplift cannot be dismissed

production of jurassic rhyolite by anatexis of the lower crust of patagonia abstract the mid jurassic marifil and chon aike volcanic rocks of eastern patagonia are part of one of the largest silicic igneous provinces known rb sr geochronology indicates eruptive ages of 175 190 ma for the marifil complex mostly toarcian aalenian the majority of the rocks are isotopically uniform with initial 87sr 86sr 0 7067 0 0003 and endt 4 2 primary magmas of andesitic composition were generated by partial melting of mafic grenvillian lower crust indentified by depleted mantle model ages of 1150 1600 ma lower crustal pyroxene granulite xenoliths can be modelled as residual jurassic source although they may alternatively be co genetic cumulates the dacite rhyolite suite formed by crystal liquid fractionation processes from the primary andesites involving multistage crystallization and re melting during magma ascent with the later stages of evolution being explicable by fractional crystallization of plagioclase amphibole and accessory minerals the province represents large scale lower crustal reworking associated with the unique tectonic and igneous environment of gondwana break up

the chon aike province of patagonia and related rocks in west antarctica a silicic large igneous province the field occurrence age classification and geochemistry of the mesozoic volcanic rocks of patagonia and west antarctica are reviewed using published and new information dominated by rhyolitic ignimbrites which form a bimodal association with minor mafic and intermediate lavas these constitute one of the largest silicic igneous provinces known equivalent in size to many mafic lips diachronism is recognized between the early middle jurassic volcanism of eastern patagonia marifil and chon aike formations and the middle jurassic earliest cretaceous volcanism of the andean cordillera el quemado ibanez and tobifera formations this is accompanied by a change in geochemical characteristics from relatively high zr and nb types in the east to subalkaline arc related rocks in the west although the predominance of rhyolites remains a constant factor all of the associated mafic rocks are well fractionated compared to direct mantle derivatives petrogenetic models favour partial melting of immature lower crust as a result of the intrusion of basaltic magmas possibly with some hybridisation of the liquids and subsequent fractionation by crystal settling or solidification and remelting the formation of large amounts of intracrustal silicic melt acted as a density barrier against the further rise of mafic magmas which are thus rare in the province

holocene and pleistocene sea level indicators at the coast of jericoacoara ceara ne brazil abstract beach rock exposures provide a record of holocene sea level rise along the 560 km long northeast facing coast of ceara brazil that differs from the record available along the other 4300 km of brazilian coastline further south whereas documentation is available from southern brazil to show holocene sea levels as much as 5 m above today s level our observations along the northeastern coast indicate that sea level here was not above the present day level during the holocene near jericoacoara about 240 km northwest of fortaleza characterized by strong surf precambrian rocks crop out from under a temporary cover of sand in small protected locations with less surf here in this upper tidal zone beach rock is being formed while it is being dismembered synchronously by erosion at lower tide levels this shows a rising sea level along the entire coast of ceara west of ponta grossa the absence of beach rock higher than spring tide level indicates that sea level was not above its present day level during the holocene notches in bedrock situated between 2 m and 6 m above spring tide high water level that we formerly described as holocene are now believed to be sangamonian

mid holocene relative sea level changes along atlantic patagonia new data from camarones chubut argentina this paper concerns the relative sea level changes associated with the atlantic patagonian coast derived from sea level index points whose elevation was determined by a differential global position system dgps bioencrustations from outcrops located near camarones chubut argentina consist of autochthonous deposits characterized by austromegabalanus psittacus molina 1782 encrusting acervulinid foraminifera coralline red algae and bryozoans the association of the different organisms is interpreted as being associated with an intertidal environment and they have been used as index points to establish the relative sea level position the main conclusion is that the relative sea level between c 7000 and 5300 cal yr bp was in the range of c 2 4 m a s l with a mean value of c 3 5 m a s l our data seem to support the existence of different rates of relative sea level fall in different sectors of atlantic patagonia during the holocene and highlight the importance of a more precise and accurate r

analysis of p and s wave vertical seismic profile data from the salton sea scientific drilling project as part of the salton sea scientific drilling project at california state well 2 14 vertical seismic profile vsp data were collected from p and s wave sources at two distances from the well use of a three component geophone along with rotation of the recorded data traces into a wave front based coordinate system allows analysis of many aspects of seismic wave propagation properties around the well standard vsp analysis techniques were used to measure interval p and s wave velocities and to identify reflecting horizons both within and below the survey interval from 455 to 1735 m a reflection from below the survey interval seen with both p and s sources seems to be associated with a fractured reservoir near 2100 m indications of fracturing were observed including vertical scattering of p waves from a zone near 915 m orthogonally polarized shear waves were generated at each offset to study anisotropy by travel time measurement and particle motion analysis of the shear wave arrivals three component particle motion analysis of shear wave arrivals was found to be effective for characterizing the subtleties in the s wave splitting throughout the various zones in the well the sht source horizontal and transverse to the well produced complicated elliptical particle motion while the sv source in line with the well produced linear particle motion the difference in linearity of particle motion from orthogonally polarized shear wave sources was unexpected and may be related to regional tectonics anomalous zones may be related to transition depths in the salton sea geothermal field travel time difference between sv and sh waves while clearly observable indicates only about 1 average anisotropy

timing and magnitude of holocene sea level changes along the middle and south patagonian atlantic coast derived from beach ridge systems littoral terraces and valley mouth terraces abstract geomorphologic and chronostratigraphic investigations in various coastal localities along the middle and south patagonian atlantic coast from bahia vera 44 s in the north to san julian 49 s in the south confirm a rich sequence of holocene beach ridge systems and littoral and valley mouth terraces beach ridges are present up to 10 m above current highest tide level htw and date to the early mid holocene transgression maximum beach ridge deposits represent high energy wave dominated coastal environments whereas valley mouth terraces and littoral terraces elevations of 5 5 6 5 m above htw developed in wave protected coastal environments the surface elevation of these littoral forms suggest that the middle and south patagonian atlantic coast is likely undergoing a slow glacio isostatic uplift on the order of 0 3 0 4 mm a since the mid holocene the early holocene sea level rise reached the modern coastline by 8100 14 c years ago c 8600 cal bp at the latest sea level at that time was most likely near its present position the holocene transgression maximum lasted from 6900 to at least 6200 14 c bp c 7400 to 6600 cal bp raising relative sea level to about 2 m to a maximum of 3 m above the present level after which sea level declined to the present level two significant sea level falls of at most 1 m occurred a between 6200 and 6000 14 c bp c 6600 to 6400 cal bp and b between 2600 and 2400 14 c bp c 2300 to 2050 cal bp we assume that both significant sea level falls were predominantly driven by eustatic changes of ocean volume whereas both thermo steric changes and changes of tides may also have contributed to these relatively strong sea level drops gravitational changes driven by greenland ice growth sensu mitrovica et al 2001 may also have amplified any eustatic portion of sea level fall the trend of a general sea level decline since the mid holocene transgression maximum seems to be predominantly glacio isostatically driven

relative sea level fall since the last interglacial stage are coasts uplifting worldwide the growing interest in quantification of vertical ground motion stems from the need to understand in detail how the earth s crust behaves for both scientific and social reasons however only recently has the refinement of dating techniques made possible the use of paleoshorelines as reliable tools for tectonic studies although there are many local studies of quaternary vertical motions of coastlines we know of no comprehensive worldwide synthesis here we provide a compilation of 890 records of paleoshoreline sequences with particular emphasis on the last interglacial stage marine isotopic stage mis 5e 122 ka the quality of dating mis 5e makes it a reliable marker to evaluate vertical ground motion rates during the late quaternary on a global scale the results show that most coastal segments have risen relative to sea level with a mean uplift rate higher than 0 2 mm yr i e more than four times faster than the estimated eustatic drop in sea level the results also reveal that the uplift rate is faster on average for active margins than for passive margins neither dynamic topography nor glacio hydro isostasy may explain sustained uplift of all continental margins as revealed by the wide distribution of uplifted sequences of paleoshorelines instead we suggest that only plate tectonic processes reconcile all observations of quaternary coastal uplift we propose that long term continental accretion has led to compression of continental plates and uplift of their margins therefore this study concludes that plate tectonics processes impact all margins and emphasizes the fact that the notion of a stable platform is unrealistic these results therefore seriously challenge the evaluation of past sea levels from the fossil shoreline record

reanalysis of the cocorp deep seismic reflection profile across the san andreas fault parkfield california in 1977 cocorp recorded a short seismic reflection test line across the san andreas fault through parkfield california where the salinian crustal block is juxtaposed against a contrasting terrane of franciscan and overlying material although analysis of this seismic line has been limited by crooked geometry lack of cross lines complex terrain possible recording noise and perhaps most of all its short length gross crustal features are discernible after extensive reprocessing and reanalysis the salinian block southwest of the san andreas consists of a maximum of 2 km of relatively underformed sediments overlying a reflective and inhomogeneous basement which exhibits deep subhorizontal layering at 8 to 10 km depth density and amplitude of reflections markedly decay perhaps corresponding to the base of a salinian granitic crust which overlies franciscan or other contrasting material northeast of the san andreas subhorizontal reflections suggest that franciscan material may extend as deeply as 13 km below which is a nonreflective zone which might represent relict oceanic crust reflections from moho depths differ across the san andreas fault beneath the salinian block is a thick zone of reflections beginning at about 22 km depth while less layered and weaker reflections seem to define the moho discontinuity at 29 km beneath the franciscan terrane the san andreas fault zone appears to be traceable as a distinct feature on the reflection section throughout the entire crust forming a near vertical zone about 3 km wide in the seismogenic upper crust down to 15 km the fault zone is marked by sharp structural truncations and short reflection or diffraction segments at depth it seems to be distinguished by a nonreflective column this vertical change in reflection character may correspond to the transition from a brittle to a ductile deformation regime

shear wave polarizations near the north anatolian fault ii interpretation in terms of crack induced anisotropy summary the polarizations of shear waves recorded by networks of digital thxee component seismometers immediately above small earthquakes near the north anatolian fault in turkey display shear wave splitting on almost all shear wave seismograms recorded within the shear wave window this splitting is incompatible with source radiation patterns propagating through simple isotropic structures but is compatible with effective anisotropy of the internal structure of the rock along the ray paths this paper interprets the phenomena in terms of widespread crack induced anisotropy distributions of stress induced cracks model many features of the observations and synthetic polarization diagrams calculated for propagation through simulated cracked rock are similar to the observed patterns this evidence for widespread crack induced anisotropy lends strong support to the hypothesis of extensive dilatancy anisotropy eda suggested by laboratory experiments in subcritical crack growth the crucial evidence confirming some form of eda would be observations of temporal changes in shear wave splitting as the stress field alters the crack density and crack geometry there is some weak evidence for such temporal changes at one site but further analysis of suitable digital three component seismometer networks in seismic areas is required to confirm eda

synthetic seismogram modeling of shear wave splitting in vsp data from the geysers california a vertical seismic profile data set showing shear wave splitting from the geysers california can be approximately fit with synthetic seismograms calculated with geometrical ray theory for anisotropic models of aligned cracks in the uppermost crust limited agreement between data and synthetics can be obtained if the cracks are constrained to be vertical but a much better fit is possible if the cracks dip at an angle of 55 degrees