crustal attenuation and site effects at parkfield california at parkfield california the san andreas fault separates strongly contrasting rock types high velocity salinian granite to the sw and lower velocity franciscan basement to the ne i use the recordings of nine earthquakes in 10 boreholes 1000 m deep and calculate p and s wave spectral ratios between borehole recordings at different depths to eliminate the source i then invert for q on each side of the san andreas fault i find that the attenuation on the ne side of the fault q ne 100 is approximately twice that on the sw side q sw 200 in the depth range 200 m to 5 km q p and q s are similar but their ratio is not well resolved i estimate q p 50 and q s 80 in the fault zone itself by combining recordings at a site within the fault zone with the inversion results and confirm that it is a low q zone q is also observed to increase with depth and the rate of this increase decreases as the depth increases in the upper 1 km at the varian well on the ne side of the san andreas fault q p 30 and q s 20 with q p increasing from 20 between 0 and 300 m to 55 between 600 and 900 m this study demonstrates that the borehole seismometers at parkfield are not deep enough for the effects of attenuation to be ignored in analysis of small earthquakes also the attenuation below 1 km on the ne side of the fault is actually larger than that below 200 m on the sw side the results of this study suggest that the attenuation at depths of a few hundred to a few thousand meters should be considered when estimating site effects in seismic hazard studies

gk17 ground motion prediction equation for horizontal pga and 5 damped psa from shallow crustal continental earthquakesgk17 gmpe for horizontal pga and 5 damped psa from shallow crustal continental earthquakes

coastline uplift in oregon and washington and the nature of cascadia subduction zone tectonics coastline deformation resulting from great shallow thrust earthquakes can provide information concerning the paleoseismicity of a subduction zone and thus information on the nature of potential seismicity the cascadia subduction zone is different from most other subduction zones in that it has been quiescent with respect to great earthquakes for at least the past 200 yr the washington oregon coastline also differs from most other coastlines associated with subduction zones in its lack of uplifted holocene shoreline features and low overall rate of late quaternary uplift 0 2 0 6 mm yr the uplift differences suggest that repeated great earthquakes have not occurred along the cascadia subduction zone at least during the late holocene alternatively if the plate interface has generated earthquakes the differences may be explained by longer recurrence intervals for great earthquakes smaller magnitude earthquakes or a mechanism that does not result in uplift of the coastline where expected

site amplification in the los angeles basin from three dimensional modeling of ground motion it is well established that sedimentary basins can significantly amplify earthquake ground motion however the amplification at any given site can vary with earthquake location to account for basin response in probabilistic seismic hazard analysis therefore we need to know the average amplification and intrinsic variability standard deviation at each site given all earthquakes of concern in the region due to a dearth of empirical ground motion observations theoretical simu lations constitute our best hope of addressing this issue here 0 0 5 hz finite difference finite fault simulations are used to estimate the three dimensional 3d response of the los angeles basin to nine different earthquake scenarios amplifi cation is quantified as the peak velocity obtained from the 3d simulation divided by that predicted using a regional one dimensional 1d crustal model average ampli fication factors are up to a factor of 4 with the values from individual scenarios typically differing by as much as a factor of 2 5 the average amplification correlates with basin depth with values near unity at sites above sediments with thickness less than 2 km and up to factors near 6 above the deepest 9 km and steepest dipping parts of the basin there is also some indication that amplification factors are greater for events located farther from the basin edge if the 3d amplification factors are divided by the 1d vertical sh wave amplification below each site they are lowered by up to a factor of 1 7 the duration of shaking in the 3d model is found to be longer by up to more than 60 seconds relative to the 1d basin response the simu lation of the 1994 northridge earthquake reproduces recorded 0 0 5 hz particle velocities relatively well in particular at near source stations the synthetic and observed peak velocities agree within a factor of two and the log standard deviation of the residuals is 0 36 this is a reduction of 54 and 51 compared to the values obtained for the regional 1d model and a 1d model defined by the velocity and density profile below a site in the middle of the basin dow respectively this result suggests that long period ground motion estimation can be improved consid erably by including the 3d basin structure however there are uncertainties con cerning accuracy of the basin model model resolution the omission of material with shear velocities lower than 1 km s and the fact that only nine scenarios have been considered therefore the amplification factors reported here should be used with caution until they can be further tested against observations however the results do serve as a guide to what should be expected particularly with respect to increased amplification factors at sites located above the deeper parts of the basin

sea99 a revised ground motion prediction relation for use in extensional tectonic regimes we present sea99 a revised predictive relation for geometric mean horizontal peak ground acceleration and 5 damped pseudovelocity response spec trum appropriate for estimating earthquake ground motions in extensional tectonic regimes which we demonstrate to have lower ground motions than other tectonic regimes sea99 replaces sea96 a relation originally derived by spudich et al 1996 1997 the data set used to develop sea99 is larger than that for sea96 and minor errors in the sea96 data set have been corrected in addition a one step regression method described by joyner and boore 1993 1994 was used rather than the two step method of joyner and boore 1981 sea99 has motions that are as much as 20 higher than those of sea96 at short distances 5 30 km and sea99 s motions are about 20 lower than sea96 at longer periods 1 0 2 0 sec and larger distance 40 100 km sea99 dispersions are significantly less than those of sea96 sea99 rock motions are on the average 20 lower than motions predicted by boore et al 1994 except for short distances at periods around 1 0 sec where sea99 motions exceed those predicted by boore et al 1994 by as much as 10 com parison of ground motions from normal faulting and strike slip events in our data set indicates that normal faulting horizontal ground motions are not significantly different from extensional regime strike slip ground motions

evaluating the compatibility of dynamic rupture based synthetic ground motion with empirical ground motion prediction equation we performed an assessment of a database of synthetic ground motion generated by a suite of dynamic rupture simulations to verify compatibility of the peak ground amplitudes with respect to empirical ground motion prediction equations gmpes the dynamic rupture model database developed by dalguer and mai 2011 is composed of 360 earthquake scenarios with moment magnitudes in the range of 5 5 7 for three mechanisms of faulting reverse normal and strike slip and for both buried faults and surface rupturing faults having depth and non depth dependent normal stresses initial shear stress distribution follows a von karman stochastic distribution overall we show quantitatively that the upper frequency limit of the suite of simulations is 1 0 hz up to this frequency the synthetic data are compatible with the empirical model which means that the residuals defined as the differences between observed and predicted ground motions fall in the range of of the empirical gmpe characteristics of the mean values along distance 10 45 km and period t 1 0 s including standard deviation of the synthetic response spectra and peak ground velocity are comparable to their counterpart empirical gmpe at very near source 1 2 km synthetics show supersaturation of the mean peak values which is different from the saturation features predicted by the gmpes the effect of source parameters such as stress drop peak slip velocity and rupture speed and of surface and buried rupture as well as hanging wall and footwall are highly sensitive to ground motion suggesting that these effects contribute to the variability of ground motion near the source and that inclusion of them in the source terms may contribute to reducing uncertainties in gmpes

frequency dependent lg q within the continental united states frequency dependent crustal attenuation 1 q is determined for seven distinct physiographic tectonic regions of the continental united states using high quality lg waveforms recorded on broadband stations in the frequency band 0 5 to 16 hz lg attenuation is determined from time domain amplitude measurements in one octave frequency bands centered on the frequencies 0 75 1 0 3 0 6 0 and 12 0 hz modeling errors are determined using a delete j jackknife resampling technique the frequency dependent quality factor is modeled in the form of q q 0 f regions were initially selected based on tectonic provinces but were eventually limited and adjusted to maximize ray path coverage in each area earthquake data was recorded on several different networks and constrained to events occurring within the crust m b 3 5 in size a singular value decomposition inversion technique was applied to the data to simultaneously solve for source and receiver terms along with q for each region at specific frequencies the lowest crustal q was observed in northern and southern california where q is described by the functions q 152 37 f 0 72 0 16 and q 105 26 f 0 67 0 16 respectively the basin and range province pacific northwest and rocky mountain states also display lower q and a strong frequency dependence characterized by the functions q 200 40 f 0 68 0 12 q 152 49 f 0 76 0 18 and q 166 37 f 0 61 0 14 respectively in contrast in the central and northeast united states q functions are q 640 225 f 0 344 0 22 and q 650 143 f 0 36 0 14 respectively show a high crustal q and a weaker frequency dependence these results improve upon previous lg modeling by subdividing the united states into smaller distinct tectonic regions and using significantly more data that provide improved constraints on frequency dependent attenuation and errors a detailed attenuation map of the continental united states can provide significant input into hazard map mitigation both scattering and intrinsic attenuation mechanisms are likely to play a comparable role in the frequency range considered in the study

development of organic porosity in the woodford shale with increasing thermal maturity abstract using a combination of focused ion beam milling and scanning electron microscopy we describe the evolution of secondary organic porosity in eight woodford shale late devonian early mississippian samples with mean random vitrinite reflectance values ranging from 0 51 ro to 6 36 ro organic porosity was observed to be absent in samples with vitrinite reflectance values of up to 0 90 ro with the first appearance of secondary pores starting with the 1 23 ro sample porosity in the organic matter was unexpectedly absent in a sample with a vitrinite reflectance of 2 00 ro however organic pores were again found in samples with higher thermal maturities porosity when present did not appear to be uniformly distributed among the organic matter that was within less than a micron of each other suggesting important differences in composition of the organic matter thin regions of organic matter were observed between grains raising the possibility that small amounts of the deposited organic matter were compacted between grains to form thin layers and or the structures are part of the secondary organic matter interpreted to be post oil bitumen which was left behind as a residue during oil migration through the shale some regions of porous organic matter appeared to be grain protected whereas others did not which indicates that these non protected porous organic regions may be stress supporting with porosity intact under in situ reservoir conditions these observations suggest that thermal maturity alone is insufficient to predict porosity development in organic shales and other factors such as organic matter composition complicate porosity development

a modified ground motion attenuation relationship for southern california that accounts for detailed site classification and a basin depth effect the attenuation relationship presented by boore et al 1997 has been evaluated and customized with respect to southern california strong motion data for peak ground acceleration pga and 0 3 1 0 and 3 0 sec period spectral acceleration this study was motivated by the recent availability of a new site classification map by wills et al 2000 which distinguishes seven different site categories for california based on the 1994 nehrp classification with few exceptions each of the five site types represented in the southern california strong motion database exhibit distinct amplification factors supporting use of the wills et al 2000 map for microzonation purposes following other studies a basin depth term was also found to be significant and therefore added to the relationship sites near the center of the la basin exhibit shaking levels up to a factor of 2 greater on average than otherwise equivalent sites near the edge relative to boore et al 1997 the other primary difference here is that pga exhibits less variation among the wills et al 2000 site types in fact the pga amplification implied by the basin depth effect is greater than that implied by site classification the model does not explicitly account for nonlinear sediment effects which if important will most likely influence rock site pga predictions the most evidence for a magnitude dependent variability or prediction uncertainty is also found and included as an option

accelerating and spatially varying crustal uplift and its geomorphic expression san andreas fault zone north of san francisco california abstract marine terraces that bevel the western flank of the point reyes peninsula were used to measure crustal uplift rates west of the san andreas fault segment north of san francisco field measurements of platform inner edges and luminescence ages from overlying marine sediments suggest the youngest platform was cut by waves during the 80 ka sea level high stand mis 5a since 80 ka the platform has been uplifted slowly throughout most of the peninsula but more rapidly in the southern part where uplift reaches a rate of 1 m ka analyses of the spatial distributions of hillslope gradient and elevation are consistent with the terrace data correlations of older terrace levels to high stand ages suggest that crustal uplift has accelerated in the southern part of the peninsula during the past 300 ky probably as a result of a contractional zone that has been migrating northward this study is the first to quantify the rate and style of crustal uplift west of this san andreas fault segment although the transform motions in this region are well documented the complex nature of interacting fault strands are only beginning to be understood these results imply that other faults with reverse motions are also active and potentially contributing to earthquake hazards

effect of low q sediments and crustal q on lg attenuation in the united states q values for lg and its coda exhibit significant lateral variations across the united states some of which correlate with known variations in the thickness of shallow sedimentary layers the possibility that all variations in lg attenuation are caused by changes in the thickness of shallow sediments is investigated by computing multi mode synthetic seismograms for crustal models with various thicknesses of low q sediments using crustal velocity and q models obtained in previous studies and reasonable values for the thicknesses and intrinsic q values of sediments in several regions we find that the variation of lg q values between the appalachian and rocky mountains can easily be produced by varying accumulations of sandstone and shale of mesozoic age and younger by contrast throughout most of the western united states neither the low lg q values which have been observed nor the regional variation of those values can be explained by accumulations of low q sediments instead their explanation appears to require low and laterally varying values of q in the crystalline crust

uncertainty in the velocity between the mass center and surface of earth 1 using spectral analysis and data decimation we estimate the uncertainty in the velocity between the cumulative mass center of earth cm and geodetic sites on earth s surface knowing this velocity is crucial for evaluating space geodetic observations of continental uplift and subsidence in terms of postglacial rebound and sea level rise we find slr observations of satellite lageos to constrain the x and y components of the velocity of cm to 0 4 mm yr and the z component to 0 9 mm yr 95 confidence limits x is in the direction of 0 n0 e y of 0 n9 0 e and z of 90 n the uncertainty in z is high so that the estimate includes the independent inference made jointly using site velocities the rigid plate hypothesis and models of postglacial rebound that the true velocity of cm has a z component of 0 5 1 0 mm yr relative to that in itrf2008 uncertainty in scale rate an intermediate parameter in the determination of an itrf is 0 36 mm yr for vlbi 0 52 mm yr for slr and 0 20 mm yr for gps the scale of gps depends on that of vlbi and slr but the low gps uncertainty indicates that gps results are for the first time unbiased by changing satellite block types evidently due to newly incorporated satellite phase center variations gps constrains the velocity of cm nearly as well as slr representing a technical advance given that a gps satellite is not a sphere and responds strongly to solar radiation pressure citation argus d f 2012 uncertainty in the velocity between the mass center and surface of earth j geophys res 117 b10405 doi 10 1029 2012jb009196

on post glacial sea level i general theory summary modern analyses of sea level changes due to glacial isostatic adjustment gia are based on the classic sea level equation derived by farrell clark 1976 geophys j r astr soc 46 647 667 the connection between global sea level variations and changes to ocean height that is assumed within this equation breaks down in the presence of a time varying shoreline geometry we present a generalized sea level equation that overcomes this difficulty we also derive analytic expressions for and present schematic illustrations of the error in the ocean height change over finite time intervals introduced in published efforts to incorporate shoreline evolution into the theory of gia induced sea level change this comparison includes studies of shoreline migration due to either local sea level changes or the growth and ablation of marine based ice we conclude that the theories applied by johnston 1993 geophys j int 114 615 634 milne 1998 phd thesis university of toronto toronto and co workers are more accurate than the procedure advocated by peltier 1994 science 265 195 201 1998a geophys res lett 25 3955 3958 1998b rev geophys 114 615 634 although an improvement in the latter has recently been reported peltier drummond 2002 geophys res lett 29 10 1029 2001gl014273 our generalized theory is valid for any earth model in a companion paper we derive the equations necessary to treat the special case of a spherically symmetric linear viscoelastic and rotating earth and we quantify errors associated with previous work

age estimates and uplift rates for late pleistocene marine terraces southern oregon portion of the cascadia forearc marine terraces are prominent landforms along the southern oregon coast which forms part of the forearc region of the cascadia subduction zone interest in the cascadia subduction zone has increased because recent investigations have suggested that slip along plates at certain types of convergent margins is characteristically accompanied by large earthquakes in addition other investigations have suggested that convergent margins can be broadly classified by the magnitude of their uplift rates with these hypotheses in mind we generated new uranium series amino acid and stable isotope data for southern oregon marine terrace fossils these data along with terrace elevations and two alternative estimates of sea level at the time of terrace formation allow us to determine terrace ages and uplift rates uranium series analysis of fossil coral yields an age of 83 5 ka for the whisky run terrace at coquille point in bandon oregon a combination of amino acid and oxygen isotope data suggest ages of about 80 and 105 ka for the lowest two terraces at cape blanco these ages indicate uplift rates of 0 45 1 05 and 0 81 1 49 m kyr for coquille point and cape blanco respectively late quaternary uplift rates of marine terraces yield information about deformation in the overriding plate but it is unclear if such data vary systematically with convergent margin type in order to assess the utility of the southern oregon uplift rates for predicting the behavior of the cascadia subduction zone we compared late quaternary uplift rates derived from terrace data from subduction zones around the world on the basis of this comparison the southern oregon rates of vertical deformation are not unusually high or low furthermore late quaternary uplift rates show little relationship to the type of convergent margin these observations suggest that local structures may play a large role in uplift rate variability in addition while the type of convergent margin may place an upper limit on possible uplift rate greater upper limits serve to increase the range of possible uplift rates in the case of the southern oregon coast variability in uplift rate probably reflects local structures in the overriding plate and the rate of uplift cannot be used as a simple index of the potential for great earthquakes along the southern cascadia subduction zone

a site conditions map for california based on geology and shear wave velocity one simple way of accounting for site conditions in calculating seismic hazards is to use the shear wave velocity in the shallow subsurface to classify materials the average shear wave velocity to 30 m v 30s has been used to develop site categories that can be used for modifying a calculated ground motion to account for site conditions we have prepared a site category map of california by first classifying the geologic units shown on 1 250 000 scale geologic maps our classification of geologic units is based on v 30s measured in 556 profiles and geological similarities between units for which we have v s data and the vast majority of units for which we have no data we then digitized the geologic boundaries from those maps that separated units with different site classifications v s data for california shows that several widespread geologic units have ranges of v 30s values that cross the boundaries between nehrp ubc site categories the franciscan complex has v 30s values across ubc categories b and c with a mean value near the boundary between those two categories older alluvium and late tertiary bedrock have v 30s values that range from about 300 to about 450 m sec across the boundary between categories c and d to accommodate these units we have created intermediate categories which we informally call bc and cd geologic units that have or are interpreted to have v 30s values near the boundary of the ubc categories are placed in these intermediate units in testing our map against the available v 30s measurements we have found that 74 of the measured v 30s values fall within the range assigned to the v s category where they fall on the map this ratio is quite good considering the inherent problems in plotting site specific data on a regional map and the variability of physical properties in geologic units we have also calculated the mean and distribution of v 30s for each of our map units and prepared composite profiles showing the variation of v s in the upper 100 m from the available v s data these data show that the map categories that we have defined based on geologic units have different v s properties that can be taken into account in calculating seismic hazards

sea level paleogeography and archeology on california s northern channel islands abstract sea level rise during the late pleistocene and early holocene inundated nearshore areas in many parts of the world producing drastic changes in local ecosystems and obscuring significant portions of the archeological record although global forces are at play the effects of sea level rise are highly localized due to variability in glacial isostatic adjustment gia effects interpretations of coastal paleoecology and archeology require reliable estimates of ancient shorelines that account for gia effects here we build on previous models for california s northern channel islands producing more accurate late pleistocene and holocene paleogeographic reconstructions adjusted for regional gia variability this region has contributed significantly to our understanding of early new world coastal foragers sea level that was about 80 85 m lower than present at the time of the first known human occupation brought about a landscape and ecology substantially different than today during the late pleistocene large tracts of coastal lowlands were exposed while a colder wetter climate and fluctuating marine conditions interacted with rapidly evolving littoral environments at the close of the pleistocene and start of the holocene people in coastal california faced shrinking land intertidal and subtidal zones with important implications for resource availability and distribution

sea level change and paleogeographic reconstructions southern vancouver island british columbia canada abstract forty eight new and previously published radiocarbon ages constrain deglacial and postglacial sea levels on southern vancouver island british columbia sea level fell rapidly from its high stand of about 75 m elevation just before 14 000 cal bp 12 000 radiocarbon yrs bp to below the present shoreline by 13 200 cal bp 11 400 radiocarbon years bp the sea fell below its present level 1000 years later in the central strait of georgia and 2000 years later in the northern strait of georgia reflecting regional differences in ice sheet retreat and downwasting direct observations only constrain the low stand to be below 11 m and above 40 m analysis of the crustal isostatic depression with equations utilizing exponential decay functions appropriate to the cascadia subduction zone however places the low stand at 30 5 m at about 11 200 cal bp 9800 bp the inferred low stand for southern vancouver island when compared to the sea level curve previously derived for the central strait of georgia to the northwest generates differential isostatic depression that is consistent with the expected crustal response between the two regions morphologic and sub bottom features previously interpreted to indicate a low stand of 50 to 65 m are re evaluated and found to be consistent with a low stand of 30 5 m submarine banks in eastern juan de fuca strait were emergent at the time of the low stand but marine passages persisted between southern vancouver island and the mainland the crustal uplift presently occurring in response to the late pleistocene collapse of the southwestern sector of the cordilleran ice sheet amounts to about 0 1 mm yr the small glacial isostatic adjustment rate is a consequence of low viscosity mantle in this tectonically active region

a cool eastern pacific ocean at the close of the last interglacial complex abstract new high precision thermal ionization mass spectrometric tims u series ages of solitary corals balanophyllia elegans from several marine terrace localities along the california and southern oregon coasts date to the 80 000 yr bp high stand of sea correlative with marine isotope substage 5a late in the last interglacial complex ages of multiple corals from localities north of point ano nuevo central california and san nicolas island southern california suggest that this high sea stand could have lasted at least 8000 yr from 84 000 to 76 000 yr bp these ages overlap with those from marine deposits on tectonically stable bermuda and tectonically emergent barbados higher elevation terraces at two california localities in the palos verdes hills and on san nicolas island have corals with ages that range mostly from 121 000 to 116 000 yr bp correlative with marine isotope substage 5e these ages are similar to those reported for other terraces in southern california but are younger than some ages reported from hawaii barbados and the bahamas marine terrace faunas are excellent proxies for nearshore marine paleotemperatures during past high sea stands terraces on the palos verdes hills and san nicolas island dated to the 120 000 yr bp high sea stand have dominantly zoogeographically neutral species in exposed coastal localities indicating nearshore waters similar to those of today in contrast 80 000 yr bp exposed coastal localities typically have molluscan faunas characterized by numerous extralimital northern species and a lack of extralimital southern species these fossil assemblages are indicative of nearshore water temperatures that were cooler than modern temperatures at 80 000 yr bp waters at least as warm as today s at 120 000 yr bp and cooler than present at 80 000 yr bp are in excellent agreement with marine alkenone records and coastal vegetation records derived from pollen data from both southern and northern california decreased insolation or increased upwelling seem inadequate to explain the cool waters off the pacific coast from southern oregon to southern california at 80 000 yr bp we propose that a stronger california current or at least one with a greater component of subarctic waters may explain cooler than modern coastal waters during the 80 000 yr bp high sea stand

late quaternary relative sea level in southern california and monterey bay abstract few records of late quaternary relative sea level rsl are available for the pacific coast of north america south of san francisco bay a region where rsl data would be particularly useful for constraining vertical rates of tectonic motion this paper provides the first regional uplift corrected late quaternary rsl history for southern california derived from a compilation of 132 previously published and unpublished radiocarbon ages from nearshore estuarine and freshwater deposits in sediment cores from coastal southern california we also provide a local uplift corrected rsl history for monterey bay central california generated from 48 radiocarbon ages from elkhorn slough and surrounding environments our resulting compilations show rapid sea level rise from 15 ka which begins to decelerate to present mean sea level pmsl between 6 and 8 ka late holocene

empirical model for basin effects accounts for basin depth and source location empirical relationships are developed to predict amplification factors for 5 damped response spectral acceleration that incorporate basin response effects the parameters considered are depth to the 1 5 km sec shear wave isosurface z 1 5 as well as the location of the source beneath or outside the perimeter of the basin in which the site is located sites located in a basin overlying the source are denoted as having coincident source and site basin locations cbl and are differentiated from distinct source and site basin locations dbl amplification factors for cbl and dbl sites are evaluated from simulated data developed by others and strong motion data amplification factors derived from strong motion recordings are taken as residuals of rock attenuation relations coupled with amplification factors for shallow site conditions models relating amplification to z 1 5 were developed separately for the cbl and dbl data groups the results indicate that the use of basin models is generally worthwhile for periods t 0 75 sec at those long periods residuals are significantly sensitive to z 1 5 for cbl but not for dbl the standard deviation is also reduced for long periods to an extent that the standard deviations for long and short periods are similar

strong motion from surface waves in deep sedimentary basins it is widely recognized that long period surface waves generated by conversion of body waves at the boundaries of deep sedimentary basins make an important contribution to strong ground motion the factors controlling the amplitude of such motion however are not widely understood a study of pseudovelocity response spectra of strong motion records from the los angeles basin shows that late arriving surface waves with group velocities of about 1 km sec dominate the ground motion for periods of 3 sec and longer the rate of amplitude decay for these waves is less than for the body waves and depends significantly on period with smaller decay for longer periods the amplitude can be modeled by the equation batchmode documentclass fleqn 10pt legalpaper article usepackage amssymb usepackage amsfonts usepackage amsmath pagestyle empty begin document mathrm log y f mathbf m r mathrm e c br mathrm b end document where y is the pseudovelocity response f m r e is an attenuation relation based on a general strong motion data set m is moment magnitude r e is the distance from the source to the edge of the basin r b is the distance from the edge of the basin to the recording site and b and c are parameters fit to the data the equation gives values larger by as much as a factor of 3 than given by the attenuation relationships based on general strong motion data sets for the same source site distance it is clear that surface waves need to be taken into account in the design of long period structures in deep sedimentary basins the ground motion levels specified by the earthquake provisions of current building codes in california at least accommodate the long period ground motions from basin edge generated surface waves for periods of 5 sec and less and earthquakes with moment magnitudes of 7 5 or less located more than 20 km outside the basin there may be problems at longer periods and for earthquakes located closer to the basin edge the results of this study suggest that anelastic attenuation may need to be included in attempts to model long period motion in deep sedimentary basins to obtain better data on surface waves in the future operators of strong motion networks should take special care for the faithful recording of the long period components of ground motion it will also be necessary to insure that at least some selected recorders once triggered continue to operate for a time sufficient for the surface waves to traverse the basin with velocities of about 1 km sec that time will be as long as 100 sec for a basin the size of the los angeles basin

interpreting quaternary uplift rates at the mendocino triple junction northern california from uplifted marine terraces analysis of the altitudinal spacing of 14 flights of marine terraces indicates a spatial pattern of varying uplift rates that agrees with that determined from previously dated terraces for the past 3 81 ka and temporal changes in uplift rates from 1 m ka to 3 5 m ka that may reflect response to changes in tectonic regime during passage of the mendocino triple junction mtj a possible mechanism for regional uplift is growth of a slab window south of the mtj the region of most rapid uplift is 25 43 km south of the mtj immediately south of the northern boundary of the slab window the coastline is tilted upward to the south in the region directly above the southern edge of the subducted gorda plate at point delgada 55 km south of the present mtj where the northern edge of the slab window passes approximately 300 ka uplift rates have been 1 2 m ka for at least 330 ka more than 1 4 m y after passage of the southern edge of the subducted slab at the mendocino coast uplift rates have been less than 0 4 m ka for at least 330 ka

summary of the gk15 ground motion prediction equation for horizontal pga and 5 damped psa from shallow crustal continental earthquakes we present a revised ground motion prediction equation gmpe for computing medians and standard deviations of peak ground acceleration pga and 5 damped pseudospectral acceleration psa response ordinates of the horizontal component of randomly oriented ground motions to be used for seismic hazard analyses and engineering applications this gmpe is derived from the expanded next generation attenuation nga west 1 database see data and resources 1 chiou et al 2008 the revised model includes an anelastic attenuation term as a function of quality factor q to capture regional differences in far source beyond 150 km attenuation and a new frequency dependent sedimentary basin scaling term as a function of depth to the 1 5 km s shear wave velocity isosurface to improve ground motion predictions at sites located on deep sedimentary basins the new graizer kalkan 2015 gk15 model developed to be simple is applicable for the western united states and other similar shallow crustal continental regions in active tectonic environments for earthquakes with moment magnitudes m 5 0 8 0 distances 0 250 km average shear wave velocities in the upper 30 m v s 30 200 1300 m s and spectral periods t 0 01 5 s our aleatory variability model captures interevent between event variability which decreases with magnitude and increases with distance the mixed effect residuals analysis reveals that the gk15 has no trend with respect to the independent predictor parameters compared to our 2007 2009 gmpe the pga values are very similar whereas spectral ordinates predicted are larger at t 0 2 s and they are smaller at longer periods 1 sec 21

testing long period ground motion simulations of scenario earthquakes using the mw 7 2 el mayor cucapah mainshock evaluation of finite fault rupture characterization and 3d seismic velocity models using a suite of five hypothetical finite fault rupture models we test the ability of long period t 2 0 s ground motion simulations of scenario earthquakes to produce waveforms throughout southern california consistent with those recorded during the 4 april 2010 m w 7 2 el mayor cucapah earthquake the hypothetical ruptures are generated using the methodology proposed by graves and pitarka 2010 and require as inputs only a general description of the fault location and geometry event magnitude and hypocenter as would be done for a scenario event for each rupture model two southern california earthquake center three dimensional community seismic velocity models cvm 4m and cvm h62 are used resulting in a total of 10 ground motion simulations which we compare with recorded ground motions while the details of the motions vary across the simulations the median levels match the observed peak ground velocities reasonably well with the standard deviation of the residuals generally within 50 of the median simulations with the cvm 4m model yield somewhat lower variance than those with the cvm h62 model both models tend to overpredict motions in the san diego region and underpredict motions in the mojave desert within the greater los angeles basin the cvm 4m model generally matches the level of observed motions whereas the cvm h62 model tends to overpredict the motions particularly in the southern portion of the basin the variance in the peak velocity residuals is lowest for a rupture that has significant shallow slip 5 km depth whereas the variance in the residuals is greatest for ruptures with large asperities below 10 km depth overall these results are encouraging and provide confidence in the predictive capabilities of the simulation methodology while also suggesting some regions in which the seismic velocity models may need improvement

glacial isostatic adjustment along the pacific coast of central north america abstract we infer the gia signal and its uncertainty along the central pacific coast of north america using 680 sea level index points and over 20 000 model runs sampling 700 1 d earth viscosity models and 29 ice sheet reconstructions due to the large spatial extent and different tectonic settings of the study area we divided it into three sub regions northern central and southern for which model parameters were inferred separately also given that this region is tectonically active the influence of this process as well as sediment isostatic adjustment was accounted for where possible by removing it from the data using published estimates our results indicate that it is not possible to produce an acceptable to for all of the rsl data with a single set of model parameters suggesting significant lateral variability in viscous structure specifically low viscosities 1019 1020 pas are inferred in the upper mantle within the northern region southwestern british columbia and northwest washington compared to those inferred 2 5 1020 pas for the central and southern regions extending from southern washington to southern california high quality model fits were obtained for all data except those from the northern region where no single parameter set was able to capture both the rapid and large rsl fall during the late glacial and the monotonic rise during the mid to late holocene at all localities this suggests the need for an earth model that incorporates departures from a linear maxwell rheology as applied here and or lateral variations in viscosity structure using our optimal model parameter sets we show that gia is a significant contributor to both contemporary vertical land motion and relative sea level change in our study region and so should be considered when interpreting observations of these signals and for making future relative sea level projections model output of present day vertical land motion at 483 gps stations and sea level change at 56 tide gauge stations is provided with estimated uncertainty so that these data can be used to study non gia processes more accurately

regionalization of crustal coda q in the continental united states a contour map of crustal q sub 0 values for the entire united states is presented based on a scattering model to explain the coda waves of local and near regional earthquakes these coda q sub 0 values are in good agreement with q of lg waves data are obtained from over 250 local earthquakes with most magnitudes between 3 0 and 5 0 recorded by 25 wwssn and 27 lrsm stations throughout the continental united states these two sets of data provide a range of frequencies from 0 5 to 3 5 hz a frequency dependence of q is observed in the range of frequencies considered a power law dependence of the form q q sub 0 f f sub 0 sup eta is assumed the value of frequency dependence eta is found to be maximum in the tectonically active western united states and least in the stable regions of the central and south central united states the lowest q sub 0 values are obtained in the western united states with values ranging from 140 to 200 in the coastal plains average crustal q sub 0 values for the basin and range province vary from 200 to 300 increasing gradually to 400 in the colorado plateau region q sub 0 valuesmore in the columbia plateau vary from 200 to 400 q sub 0 values increase very rapidly along the central and southern rocky mountains from 400 to 800 east of the rocky mountains q sub 0 values increase gradually in the interior plains to a maximum value of around 1300 in the mississippi embayment region farther east q sub 0 values decrease gradually to an almost constant value of 1000 along the appalachian mountains coastal regions of eastern and northeastern united states have a crustal q sub 0 value between 900 to 700 regions of north central and gulf coastal plains show low q sub 0 values ranging from 600 to 400 and less the source factor b f sub p a measure of the intensity of scattering was obtained for several different regions of the continental united states regions of high q sub 0 values exhibit low intensity of scattering less

postglacial rebound at the northern cascadia subduction zone postglacial rebound is the response of the earth to the decay of ice sheets a postglacial rebound model explains crustal tilting and rapid uplift at the northern cascadia subduction zone that occurred during retreat of the cordilleran ice sheet observations explained by the model include the shoreline tilts of two proglacial lakes that formed at 13 5 14 ka 14c yr ago and rapid sea level fall land uplift at 12 12 5 ka modelled mantle viscosity values range from 5 1018 to 5 1019 pa s and are consistent with previous viscosity inferences from observations of crustal deformation following subduction zone earthquakes 1018 1019 pa s no lower limit to subduction zone mantle viscosity is apparent from our model but viscosity values equal to or larger than 1020 pa s are de nitely ruled out our modelled subduction zone viscosity values are smaller than most upper mantle viscosity estimates derived from postglacial rebound studies of tectonically less active regions 1020 1021 pa s the rapid observed uplift at 12 ka requires in addition to a low mantle viscosity rapid unloading from a sudden collapse of remaining coastal portions of the southern cordilleran ice sheet the sudden collapse provides 0 18 m of global eustatic sea level rise approximately 0 7 of the sea level rise associated with melt water pulse ia predictions of a global postglacial rebound model ice 3g with a 1021 pa s upper mantle viscosity were previously applied to geodetic data from this region to isolate signals associated with the earthquake cycle owing to the low viscosity values and resulting rapid recovery of glacial deformation our model predicts present day postglacial rebound uplift rates at least 10 times smaller than ice 3g less than about 0 1 mm yr as the ice 3g adjustments were substantial this indicates the need for re evaluation of the geodetic data 2000 elsevier science ltd all rights reserved

modeling geometrical spreading and the relative amplitudes of vertical and horizontal high frequency ground motions in eastern north america abstract horizontally layered velocity models were used with point source and finite fault sources to investigate geometrical spreading and the relative amplitudes of vertical and horizontal ground acceleration within 120 km of the source full wave field simulations were done for a range of focal depths and for strike slip and reverse focal mechanisms the attenuation of the geometric mean of randomly oriented horizontal component maximum acceleration amplitudes averaged over all azimuths significantly exceeds the theoretical geometrical spreading for far field body waves in a homogeneous whole space for hypocentral distances less than approximately 60 km the behavior of the vertical component is different from the horizontal vertical attenuation near the epicenter is greater and is more dependent on source mechanism and depth because of the rapid near source decay of the direct s wave reflections from the mid lower crust and moho control the maximum amplitude of the vertical component acceleration in the 60 120 km hypocenter distance range resulting in a flattening of the vertical amplitude distance relation near source vertical maximum amplitudes averaged over all source receiver azimuths tend to be less than the geometric mean horizontal amplitude for strike slip focal mechanisms but near the source for reverse faults the azimuthally averaged vertical component amplitude exceeds that of the geometric mean horizontal the modeling indicates that similar vertical and horizontal component geometrical spreading and approximately constant horizontal vertical amplitude ratios observed in connection with the lg phase at distances greater than approximately 100 km in eastern north america may not hold at smaller distances ground motion prediction models for the vertical component near the source may need to incorporate strong geometrical spreading and dependence on radiation pattern

observations of basin ground motions from a dense seismic array in san jose california we installed a dense array of 41 digital seismographs in san jose california to evaluate in detail the effects of a deep sedimentary basin and shallow sedimentary deposits on earthquake ground motions this urban array is located near the eastern edge of the santa clara valley and spans the evergreen sedimentary basin identified by gravity data average station spacing is 1 km with three stations initially spaced 110 m apart despite the high noise urban environment the stations of the array successfully triggered on and recorded small local earthquakes m 2 5 2 8 at 10 25 km distance and larger regional events such as the m 5 0 bolinas earthquake 90 km distance m 4 6 5 6 earthquakes near mammoth lakes 270 km distance m 4 9 5 6 events in western nevada 420 km distance and the m 7 1 hector mine earthquake 590 km distance maps of spectral ratios across the array show that the highest amplitudes in all frequency bands studied 0 125 8 hz are generally observed at stations farther from the eastern edge of the santa clara valley larger spectral amplitudes are often observed above the western edge of the evergreen basin snapshots of the recorded wavefield crossing the array for regional events to the east reveal that large low frequency 0 125 0 5 hz arrivals after the s wave travel from south to north across the array a moving window cross correlation analysis finds that these later arrivals are surface waves traveling from the south the timing and propagation direction of these arrivals indicates that they were likely produced by scattering of incident s waves at the border of the santa clara valley to the south of the array it is remarkable that the largest low frequency phases at many of the valley sites for regional events to the east are basin surface waves coming from a direction about 70 degrees different from that of the epicenters basin surface waves emanating from the eastern edge of the valley are also identified by the cross correlation analysis

trinet strong motion data from the m 7 1 hector mine california earthquake of 16 october 1999 the m w 7 1 hector mine earthquake of october 16 1999 was recorded by more than 300 stations of trinet which is administered cooperatively by the california division of mines and geology s california strong motion instrumentation program cdmg csmip california institute of technology and the u s geological survey usgs the earthquake occurred in a remote part of the mojave desert approximately 190 km northeast of downtown los angeles and there were no strong motion stations close to the surface rupture the nearest station hector is about 27 km north of the epicenter it recorded a peak horizontal ground acceleration of 0 33g the two next closest stations amboy and joshua tree are to the east and south both at epicentral distances of about 50 km each recorded peak ground accelerations of about 0 2g the new digital instruments installed for the trinet project recorded a large set of reliable data at epicentral distances up to 275 km these data can significantly improve empirical peak ground motion attenuation relationships which are usually developed for distances only up to 100 km boore et al 1993 1997 because adequate data have not been available at greater distances hector mine peak ground motions demonstrate reasonable agreement with empirical attenuation relationships for acceleration in contrast higher than expected ground velocities and displacements were recorded at epicentral distances of about 150 to 220 km especially in the los angeles sedimentary basin where anomalously high amplitude displacements with periods of 6 to 7 sec were recorded in los angeles long beach and other areas these long period surface or basin generated waves can have significant effects on large structures the m w 7 3 landers earthquake of 1992 similarly produced strong long period waves in the basin the peak ground motions produced by the landers earthquake were on average 1 6 times higher than for the hector mine earthquake in the los angeles area ground motion data recorded by digital instruments were uniformly processed in the frequency band 0 067 to 46 hz 0 022 15 sec the processed data set includes records from 213 ground response stations in an effort to make strong motion data available quickly to the engineering and scientific communities important records from this event were made available by file transfer protocol ftp beginning the day of the earthquake

rheological stratification of the lithosphere a direct inference based upon the geodetically observed pattern of the glacial isostatic adjustment of the north american continent 1 a sequence of new analyses of the process of glacial isostatic adjustment gia is described the focus is upon the resolution of a recognized flaw in the currently prevalent model of this process that denoted ice 5g vm2 the flaw concerns a previously noted inability of the model to simultaneously reconcile the vlbi and gps measured rates of vertical and horizontal motion in the region of the north american continent that lay outboard and to the south of the laurentide ice sheet lis at last glacial maximum this characteristic misfit of the model to the data has been suggested to be reconcilable only by recourse to models that explicitly incorporate the influence of lateral viscosity heterogeneity it is demonstrated herein that on the contrary this flaw is entirely and unambiguously attributable to the rheological stratification of the lithosphere an influence not previously accounted for in global models of the gia process but which must exist on a priori grounds

the crustal seismicity of the western andean thrust central chile 33 34 s implications for regional tectonics and seismic hazard in the santiago areathe crustal seismicity of the western andean thrust central chile 33 34 s