a next generation vs30 map for california based on geology and topography abstract correlations between geologic units and shear wave velocity form the basis of a series of maps developed over the past 15 years to estimate the time averaged shear wave velocity in the upper 30 m v s 30 the wills et al 2000 site condition map for california was found to correlate with seismic amplification field 2000 and was adopted as a standard depiction for many applications of seismic shaking estimates shakemap for example wills and clahan 2006 modified that map to show simplified geologic units and corresponding v s 30 values preparation of this map raised a number of questions on how best to distinguish units within younger alluvium wills and gutierrez 2011 found that a simple system based on surface slope could be used to subdivide the younger alluvium into three classes that have distinct v s 30 ranges the classes defined by slope have approximately the same variability in v s 30 as the previously defined classes but the total number of classes is reduced and the system can be easily applied to other tectonically active areas we have now applied the system of wills and gutierrez 2011 to create a new map of california using the most detailed available geologic maps use of more detailed geologic maps from 1 250 000 scale to 1 24 000 for much of california results in a much more detailed and accurate depiction of the surficial geology and we anticipate a more detailed and accurate depiction of seismic amplification due to the near surface materials online material site condition map of california at a scale of 1 1 500 000 as well as in arcgis formats

crystallization and vesiculation of the 1984 eruption of mauna loa calculations based on existing thermodynamic models for silicate melts are used to model the physical and chemical evolution of the 1984 mauna loa magma specifically the calculations simulate the vesiculation induced crystallization of the ascending magma the calculations provide a physiochemical model to explain the increase in crystallization under isothermal conditions the evolution of the mauna loa magma is modeled in three separate stages corresponding to 1 the subsurface crystallization of the phenocryst assemblage 2 the crystallization and vesiculation of the magma during its ascent from depth and 3 the crystallization and vesiculation of the lavas at the surface the preeruptive crystallization of olivine and orthopyroxene phenocrysts began at 1155 c and 0 2 gpa olivine and plagioclase alone crystallized during the ascent of the magma the bulk of the crystallization and vesiculation of the mauna loa magma occurred at pressures less than 20 mpa under lithostatic pressures this corresponds to depths as shallow as 600 700 m ancillary calculations have established the net heat effect of the prescribed ascent path and demonstrate that the heat associated with vesiculation easily compensates for the heats of crystallization the calculations suggest that the near surface processes can be quite endothermic depending on the initial h2o content of the magma for a magma with 1 wt dissolved h2o the heat balance demands approximately 5 10 c cooling further calculations predict the liquid line of descent for this ascent path and document the corresponding variations in the physical properties of the melt phase

nonlinear ground motion amplification by sediments during the 1994 northridge earthquake it has been known since at least 1898 ref 1 that sediments can amplify earthquake ground motion relative to bedrock for the weak ground motion accompanying small earthquakes the amplification due to sediments is well understood in terms of linear elasticity hooke s law 2 but there has been a long standing debate regarding the amplification associated with the strong ground motion produced by large earthquakes the view of geotechnical engineers based largely on laboratory studies is that hooke s law breaks down at larger strains causing a reduced nonlinear amplification seismologists on the other hand have tended to remain sceptical of this nonlinear effect mainly because the relatively few strong motion observations seemed to be consistent with linear elasticity although some recent earthquake studies have demonstrated nonlinear behaviour under certain circumstances3 4 the significance of nonlinearity for the type of stiff soil sites found in the greater los angeles region remains unresolved5 here we report that ground motion amplification due to sediments for the main shock of the 1994 northridge earthquake was up to a factor of two less than the amplification observed for its aftershocks these observations imply significant nonlinearity in such amplification and bring into question the use of measurements of weak ground motion to predict the strong ground motion at sedimentary sites

a terrain based site conditions map of california with implications for the contiguous united states abstract we present an approach based on geomorphometry to predict material properties and characterize site conditions using the v s 30 parameter time averaged shear wave velocity to a depth of 30 m our framework consists of an automated terrain classification scheme based on taxonomic criteria slope gradient local convexity and surface texture that systematically identifies 16 terrain types from 1 km spatial resolution 30 arcsec shuttle radar topography mission digital elevation models srtmdems using 853 v s 30 values from california we apply a simulation based statistical method to determine the mean v s 30 for each terrain type in california we then compare the v s 30 values with models based on individual proxies such as mapped surface geology and topographic slope and show that our systematic terrain based approach consistently performs better than semiempirical estimates based on individual proxies to further evaluate our model we apply our california based estimates to terrains of the contiguous united states comparisons of our estimates with 325 v s 30 measurements outside of california as well as estimates based on the topographic slope model indicate our method to be statistically robust and more accurate our approach thus provides an objective and robust method for extending estimates of v s 30 for regions where in situ measurements are sparse or not readily available

observed relationships between the el nino southern oscillation and the extratropical zonal mean circulation abstract there is increasing evidence indicating that the climate response to variations in the el nino southern oscillation enso includes not only thermally forced zonal wind anomalies in the subtropics but also eddy driven zonal wind anomalies that extend into the mid high latitudes of both hemispheres in this study new insights into the observed seasonally varying signature of enso in the extratropical zonal mean circulation are provided and the associated linkages with the dominant patterns of extratropical variability are examined the zonal mean extratropical atmospheric response to enso is characterized by two principal features an equivalent barotropic dipole in the southern hemisphere sh zonal mean zonal flow with centers of action located near 40 and 60 during austral summer and a weaker but analogous dipole in the northern hemisphere nh with centers of action located near 25 and 45 during early and late boreal winter both structures are accompanied by eddy momentum flux ano

global to regional nested grid climate simulations in the gfdl high resolution atmospheric model abstracta two way nested grid version of the geophysical fluid dynamics laboratory high resolution atmosphere model hiram has been developed that uses simple methods for providing nested grid boundary conditions and mass conserving nested to global communication nested grid simulations over the maritime continent and over north america were performed each at two different resolutions a 110 km mean grid cell width refined by a factor of 3 and a 50 km mean grid cell width refined by a factor of 2 nested grid simulations were compared against uniform resolution simulations and against reanalyses to determine the effect of grid nesting on both the modeled global climate and the simulation of small scale features orographically forced precipitation was robustly found to be simulated with more detail and greater realism in a nested grid simulation compared with when only the coarse grids were simulated alone tropical precipitation biases were reduced in the maritime continent region when a nested grid

unified structural representation of the southern california crust and upper mantle we present a new 3d description of crust and upper mantle velocity structure in southern california implemented as a unified structural representation usr the usr is comprised of detailed basin velocity descriptions that are based on tens of thousands of direct velocity vp vs measurements and incorporates the locations and displacement of major fault zones that influence basin structure these basin descriptions were used to developed tomographic models of crust and upper mantle velocity and density structure which were subsequently iterated and improved using 3d waveform adjoint tomography a geotechnical layer gtl based on vs30 measurements and consistent with the underlying velocity descriptions was also developed as an optional model component the resulting model provides a detailed description of the structure of the southern california crust and upper mantle that reflects the complex tectonic history of the region the crust thickens eastward as moho depth varies from 10 to 40 km reflecting the transition from oceanic to continental crust deep sedimentary basins and underlying areas of thin crust reflect neogene extensional tectonics overprinted by transpressional deformation and rapid sediment deposition since the late pliocene to illustrate the impact of this complex structure on strong ground motion forecasting we simulate rupture of a proposed m 7 9 earthquake source in the western transverse ranges the results show distinct basin amplification and focusing of energy that reflects crustal structure described by the usr that is not captured by simpler velocity descriptions we anticipate that the usr will be useful for a broad range of simulation and modeling efforts including strong ground motion forecasting dynamic rupture simulations and fault system modeling the usr is available through the southern california earthquake center scec website http www scec org

uncertainty in vs30 based site response abstract methods that account for site response range in complexity from simple linear categorical adjustment factors to sophisticated nonlinear constitutive models seismic hazard analysis usually relies on ground motion prediction equations gmpes within this framework site response is modeled statistically with simplified site parameters that include the time averaged shear wave velocity to 30 m v s 30 and basin depth parameters because v s 30 is not known in most locations it must be interpolated or inferred through secondary information such as geology or topography in this article we analyze a subset of stations for which v s 30 has been measured to address effects of v s 30 proxies on the uncertainty in the ground motions as modeled by gmpes the stations we analyze also include multiple recordings which allow us to compute the repeatable site effects or empirical amplification factors eafs from the ground motions although all methods exhibit similar bias the proxy methods only reduce the ground motion standard deviations at long periods when compared to gmpes without a site term whereas measured v s 30 values reduce the standard deviations at all periods the standard deviation of the ground motions are much lower when the eafs are used indicating that future refinements of the site term in gmpes have the potential to substantially reduce the overall uncertainty in the prediction of ground motions by gmpes

a test of various site effect parameterizations in probabilistic seismic hazard analyses of southern california we evaluate the implications of several attenuation relationships including three customized for southern california in terms of accounting for site effects in probabilistic seismic hazard studies the analysis is carried out at 43 sites along a profile spanning the los angeles basin with respect to peak acceleration and 0 3 1 0 and 3 0 sec response spectral acceleration values that have a 10 chance of being exceeded in 50 years the variability among currently viable attenuation relationships espistemic uncertainty is an approximate factor of 2 biases between several commonly used attenuation relationships and southern california strong motion data imply hazard differences that exceed 10 however correcting each relationship for the southern california bias does not necessarily bring hazard estimates into better agreement a detailed subclassification of site types beyond rock versus soil is found to be both justified by data and to make important distinctions in terms of hazard levels a basin depth effect is also shown to be important implying a difference of up to a factor of 2 in ground motion between the deepest and shallowest parts of the los angeles basin in fact for peak acceleration the basin depth effect is even more influential than the surface site condition questions remain however whether basin depth is a proxy for some other site attribute such as distance from the basin edge the reduction in prediction error sigma produced by applying detailed site and or basin depth corrections does not have an important influence on the hazard in fact the sigma reduction is less than epistemic uncertainties on sigma itself due to data limitations it is impossible to determine which attenuation relationship is best however our results do indicate which site conditions seem most influential this information should prove useful to those developing or updating attenuation relationships and to those attempting to make more refined estimates of hazard in the near future

climatology of the low level jet east of the andes as derived from the ncep ncar reanalyses characteristics and temporal variability abstract a climatology of the south american low level jet east of the andes sallj is developed using the 1950 2000 circulation and moisture fields from the ncep ncar reanalyses and available upper air observations made in bolivia and paraguay since 1998 upper and low level circulation fields were derived for seasonal means and sallj composites during the warm and cold seasons the bonner criterion 1 was applied for sites in central bolivia and downstream near northern paraguay to determine the spatial and temporal characteristics of the sallj on the circulation characteristics sallj composites during the warm season show the enhanced low level meridional moisture transport coming from equatorial south america as well as an upper level wave train emanating from the west pacific propagating toward south america the intensification of the warm season sallj follows the establishment of an upper level ridge over southern brazil and a trough over most of argentina the circulation anomalies at upper a

impact of variable resolution meshes on midlatitude baroclinic eddies using cam mpas a abstractthe effects of a variable resolution mesh on simulated midlatitude baroclinic eddies in idealized settings are examined both aquaplanet and held suarez experiments are performed using the model for prediction across scales atmosphere mpas a hydrostatic dynamical core implemented within the national science foundation department of energy nsf doe community atmosphere model cam mpas a in the real world midlatitude eddy activity is organized by orography land sea contrasts and sea surface temperature anomalies in these zonally symmetric idealized settings transients should have an equal probability of occurring at any longitude however the use of a variable resolution mesh with a circular high resolution region centered at 30 n results in a maximum in eddy kinetic energy on the eastern side and downstream of this high resolution region in both aquaplanet and held suarez cam mpas a simulations the presence of a geographically confined maximum in both simulations suggests this response

assessment of seismic site conditions a case study from guwahati city northeast india the 1897 great shillong earthquake revealed considerable seismic susceptibility in guwahati city such as soil liquefaction landslides and surface fissures in an attempt to quantify the seismic vulnerability of the city based on geological seismological and geotechnical aspects concerning seismic site characterization in depth analysis was performed using a microtremor survey with recordings of five small to moderate magnitude 4 8 mb 5 4 earthquakes that occurred in 2006 and geotechnical investigations using the standard penetration test spt additionally the basement topography was established using vertical electrical resistivity sounding and selected drill hole information region specific relationships are derived by correlating the estimated values of predominant frequency shear wave velocity and basement depth indicating conformity with the predominant frequency distribution and the basin topography underlain by a hard granitic basement most parts of the city adhere to the predominant frequency range of 0 5 3 5 hz setting aside areas of deep sediment fills or hilly tracts suggesting that the existing moderate rise rc buildings in the territory are seismically vulnerable furthermore the geotechnical assessment of the soil liquefaction potential reveals widespread susceptibility across the terrain eventually a site classification map of the city is prepared following the national earthquake hazard program nehrp provision the average site amplification factor from geotechnical modeling for site class d is about 3 in the frequency range of 2 4 hz in addition earthquake data yield an average site amplification factor of 4 6 in the frequency range of 1 2 5 0 hz at the seismic stations located in site class e and f high site amplifications of around 5 5 and 7 5 at 2 hz respectively are observed at amtron and irrig seismic stations which are located in the proximity of precambrian rocks indicating probable basin edge effects scattering and diffraction of incident energy interplay of dispersed valleys surrounded by small hillocks in the study region is likely to induce micro basin effects where the sediment thickness depth vis a vis predominant frequency and basin geometry in conjunction play pivotal roles in the augmentation of site response

observed southern hemisphere eddy statistics at 500 mb frequency and spatial dependence abstract nearly eight years of daily southern hemisphere analyses at 500 mb have been used to define the spatial dependence of the variance fields of geopotential height and the two geostrophic wind components the corresponding covariance fields and the transient kinetic energy the fields are further examined in the frequency domain by using lorenz 1979 poor man s spectral analysis technique in view of the small variation in eddy statistics as a function of the time of the year in the sh this study removes the first four harmonies of the annual cycle and then considers all data together so that contributions from all time scales from 2 to 4096 days 11 years can be resolved the main results are based on analyses from may 1972 january 1978 but are verified with analyses from the relatively data rich fgge period results for the zonal mean statistics are compared with those from previous studies the zonal means of the geopotential height and westerly wind component have spectra which roughly

track deflection of typhoon nesat 2017 as realized by multiresolution simulations of a global model abstracttyphoon nesat 2017 headed west northwestward toward taiwan but took a relatively larger northward deflection about 300 km away and then a leftward deflection after landfall at northern ta

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

assessment of the site conditions of precariously balanced rocks in the mojave desert southern california we examine whether groups of precariously balanced rocks in the mo jave desert southern california may have remained standing for thousands of years because anomalous site conditions prevent the rocks from toppling during large earth quakes measurements of peak ground velocity at bandwidths of 0 5 1 1 2 2 4 4 8 and 8 16 hz for 56 earthquakes ml 3 5 4 8 at two sites of precarious rocks are compared with velocities recorded for the same earthquakes by three tri net stations located on engineering rock national earthquake hazard reduction program nehrp site class b we find that the residuals the logarithm of the ratio of the amplitudes recorded at the precarious rock sites to the trinet amplitudes for the same earthquake and epicentral distance at frequencies less than about 4 hz are negative i e deamplification of 50 250 whereas the residuals are slightly positive at the higher frequencies i e amplification of up to 25 50 high frequency ground motions e g peak ground acceleration may therefore be slightly amplified at the precarious rock sites which means that site conditions do not appear to explain the existence of the precarious rocks in areas where high peak ground accelerations are predicted in recent probabilistic seismic hazard psh models this discrepancy between the precarious rocks and the psh models should be urgently resolved

crystallization history of the 1984 mauna loa lava flow during a 3 week eruption in 1984 mauna loa produced vent lavas that increased in crystallinity from 1 to 30 and 27 km long flows that increased in crystallinity as they moved downstream we examined the crystallization history of these lavas using crystal size distribution csd analysis to study the rates of crystallization viscosity increase and latent heating typical average growth and nucleation rates were 5 10 9 cm s 1 and 5 cm 3 s 1 for microphenocrysts 20 to 500 m size crystals nucleated in the rift zone and 5 10 8 cm s 1 and 5 104 cm 3 s 1 for microlites 1 to 20 m size crystals nucleated in the channel these crystallization rates are high compared with those found in other csd studies of igneous rocks probably due to highly nonequilibrium conditions brought on by rapid degassing in the rift zone and cooling in the lava channel growth and nucleation rates decreased with time at the vent and with distance downstream the maximum downstream total crystallinity measured is 39 25 microlites 14 microphenocrysts in a quenched sample 14 km from the vent growth and nucleation rates cannot be calculated for postemplacement samples but they place upper limits of 53 58 on the amount of crystallization in the channel 9 20 km from the vent crystallization could have been mostly responsible for the 105 fold downstream increase in apparent viscosity although degassing and increasing incorporation of solid lava fragments also contributed another effect of crystallization on the lava flow was the sizeable latent heating 0 01 j g 1 s 1 over the first half of the flow length if the crystallinity of downstream quench samples is representative of the hot fluid core which may have been counteracted by entrainment of cooler material measurements of crystallization are shown to be crucial in the study of lava flow emplacement dynamics

replication of apparent nonlinear seismic response with linear wave propagation models it is necessary to understand ground motion amplification by sediment defined as the ratio of ground motions at sediment sites to those at rock sites to predict seismic loadings for earthquake engineering at sediment sites observed weak motion amplifications from magnitude 3 to 4 aftershocks of the 1994 northridge earthquake were twice as large as magnitude 6 7 mainshock amplifications amplitude dependent nonlinear amplification by sediment is one explanation however earthquake simulations with empirical impulse responses and elastic finite difference calculations with weakly heterogeneous random three dimensional 3d crustal velocity variations show that linear wave propagation can explain observed apparently nonlinear sediment responses random 3d velocity variations also reproduce the observed log normal dispersion of peak ground motions deterministic wave propagation models are not adequate to quantify the scaling and dispersion of near source ground motions

predictions of shear wave velocities in southern california using surface geology a new model of the average shear wave velocity in the uppermost 30 m has been generated by extrapolation of discrete velocity profiles using surface geology at several scales statistical methods have been applied to create a map that is no more complicated than is supported by the velocity data several geologic units with similar responses are grouped together the resulting map is simpler than previous ones and yet fits the observed velocity profiles better than earlier more complicated maps analysis within a geographic information system will permit updates and modification of the map as new velocity data are added

fluid volcanism on miranda and ariel flow morphology and composition several types of volcanic units have been recognized on the icy uranian satellites miranda and ariel on miranda ridges characterized by crest grooves are up to 10 km wide and 500 m high a continuous flat topped flow band also 10 km wide and 500 m high forms the outer southern margin of elsinore corona elsinore coronae at least appears to comprise coalesced flow bands and ridges on ariel in addition to at least one ridge unit similar to these on miranda flood plains material has covered the floors of deep chasmata grabens and an irregular depression flows on both satellites are characterized by linear vent geometries and distinct topographic margins which indicate extrusion of a relatively viscous material the topography of the flows can be used to estimate flow viscosity or yield strength using a bingham plastic model extrusion viscosity estimates incorporating plausible volcanologically based emplacement time scales and a rigid crust correction range from 107 to 109 p 1013 p in the unlikely absence of a chilled crust viscosity estimates are dependent on the assumed emplacement time scale however and could be as high as 1016 p if a solid stale based time scale is assumed bingham models indicate that it is yield strength that controls the final flow width and thickness that we see yield strength estimates are probably more reliable because of uncertainties in the viscous flow time scale yield strength estimates range from 10 1 to 10 2 bars consistent with yield strengths of partially crystallized silicate melts on other planets nevertheless both the viscosities and yield strengths are well within the range of and in some cases lower than silicate flows silicate compositions are not possible for these flows because of the ice rich composition of these satellites measured properties of ammonia water liquid crystal mixtures are consistent with the observed and estimated flow rheologic properties however and extrusion of such material s is a viable alternative to solid state extrusion for the origin of these flow features

impact of lateral boundary errors on the simulation of clouds with a nonhydrostatic regional climate model abstracta nonhydrostatic regional climate limited area model lam was used to analyze lateral boundary condition lbc errors and their influence on the uncertainties of regional models simulations using the fully compressible nonhydrostatic lam d nicam were compared against the corresponding global quasi uniform grid nonhydrostatic icosahedral atmospheric model nicam and a stretched grid counterpart s nicam by this approach of sharing the same dynamical core and physical schemes possible causes of model bias and lbc errors are isolated the simulations were performed for a 395 day period from march 2011 through march 2012 with horizontal grid intervals of 14 28 and 56 km in the region of interest the resulting temporal mean statistics of the temperatures at 500 hpa were generally well correlated between the global and regional simulations indicating that lbc errors had a minor impact on the large scale flows however the time varying statistics of the surface precipitation showed that the

three dimensional simulation of a magnitude 7 75 earthquake on the san andreas fault simulation of 2 minutes of long period ground motion in the los angeles area with the use of a three dimensional finite difference method on a parallel supercomputer provides an estimate of the seismic hazard from a magnitude 7 75 earthquake along the 170 kilometer section of the san andreas fault between tejon pass and san bernardino maximum ground velocities are predicted to occur near the fault 2 5 meters per second and in the los angeles basin 1 4 meters per second where large amplitude surface waves prolong shaking for more than 60 seconds simulated spectral amplitudes for some regions within the los angeles basin are up to 10 times larger than those at sites outside the basin at similar distances from the san andreas fault

three dimensional seismic velocity structure in the sichuan basin china we present a new three dimensional velocity model of the crust in the eastern margin of the tibetan plateau the model describes the velocity structure of the sichuan basin and surrounding thrust belts the model consists of 3 d surfaces representing major geologic unit contacts and faults and is parameterized with vp velocity depth functions calibrated using sonic logs the model incorporates data from 1166 oil wells industry isopach maps geological maps and a digital elevation model the geological surfaces were modeled based on structure contour maps for various units from oil wells and seismic reflection profiles these surfaces include base quaternary mesozoic paleozoic and proterozoic horizons the horizons locally exhibit major offsets that are compatible with the locations and displacements of important faults systems this layered upper crustal 3 d model extends down to 10 15 km depth and illustrates lateral and vertical variations of velocity that reflect the complex evolution of tectonics and sedimentation in the basin the model also incorporates 3 d descriptions of vs and density for sediments that are obtained from empirical relationships with vp using direct measurements of these properties in borehole logs to illustrate the impact of our basin model on earthquake hazards assessment we use it to calculate ground motions and compare these with observations for the 2013 lushan earthquake the result demonstrates the effects of basin amplification in the western sichuan basin the sichuan cvm model is intended to facilitate fault systems analysis strong ground motion prediction and earthquake hazards assessment for the densely populated sichuan region

northern winter stationary waves theory and modeling a review is provided of stationary wave theory the theory for the deviations from zonal symmetry of the climate to help focus the discussion the authors concentrate exclusively on northern winter several theoretical issues including the external rossby wave dispersion relation and vertical structure critical latitude absorption the nonlinear response to orography and the interaction of forced wave trains with preexisting zonal asymmetries are chosen for discussion while simultaneously presenting a decomposition of the wintertime stationary wave field using a nonlinear steady state model

uncertainty of southern california basin depth parameters we validate a model for the velocity structure of basin sediments in southern california against sonic log data and evaluate the bias and uncertainty of basin depth terms basin depth as measured by depth to the 1 5 km sec shear wave isosurface is underpredicted near the basin margins where the basin is relatively shallow and overpredicted near the middle of the basin the standard deviation of the residuals is approximately 410 m when the bias trends are not considered and approximately 240 m when they are considered the effects of the bias on estimated ground motions are likely small because the available empirical models utilized this same velocity model and hence inherently incorporate the bias effects the effect of uncertainty in basin depths can introduce uncertainty in ground motions of up to 0 1 in natural log units which is small compared to typical error terms in attenuation relations

influence of the tropics on the southern annular mode abstractperturbations in the southern annular mode sam are shown to be significantly correlated with sst anomalies in the central tropical pacific during austral winter and sst anomalies in the eastern tropical pacific during austral summer the sam signature in the pacific sector resembles a tropically forced rossby wave train the so called pacific south american pattern while the signature in the indian ocean sector is a zonally elongated meridional dipole thus the sam contains strong zonally asymmetric variability and tends to behave differently in the eastern and western hemispheres with internal dynamics prevailing in the indian ocean sector and the forced response to tropical sst anomalies exerting a strong influence in the pacific sector the tropically forced component of the sam in the pacific sector is related to a geographically fixed active rossby wave source to the east of australia within the core of the subtropical jet in addition to the well documented positive trend in summer the

nonlinear soil response a reality geotechnical models consistently indicate that the stress strain relationship of soils is nonlinear and hysteretic especially at shear strains larger than 10 5 to 10 4 nonlinear effects such as an increase in damping and reduction in shear wave velocity as excitation strength increases are commonly recognized in the dynamic loading of soils on the other hand these effects are usually ignored in seismological models of ground motion prediction because of the lack of compelling corroborative evidence from strong motion observations the situation is being changed by recently obtained data explicit evidence of strong motion deamplification accompanied by changes in resonant frequencies are found in the data from the 1985 michoacan mexico and the 1989 loma prieta california earthquakes the events recorded by the vertical and surface accelerograph arrays in taiwan as well as a number of other events throughout the world evidence of nonlinear behavior becomes apparent beyond a threshold acceleration of 100 to 200 gal nonlinearity is considerable in cohesionless soil but may be negligible in stiff soils the findings of recent years indicate that nonlinear site effects are more common than previously recognized in strong motion seismology

full 3d tomography for the crustal structure of the los angeles region we apply full 3d tomography f3dt to a regional dataset in the los angeles area in f3dt the starting model as well as the model perturbation is three dimensional and the sensitivity frechet kernels are computed using numerical schemes that account for the full physics of 3d wave propagation f3dt can account for the nonlinearity of structural inverse problem through iteration thus providing the most efficient means for assimilating seismic observations into dynamic ground motion models we have successfully applied a scattering integral si formulation of f3dt to improve a 3d elastic structure model the southern california earthquake center scec community velocity model version 3 0 cvm3 0 with lowest shear velocity clamped at 1 km sec in the los angeles region our data are time and frequency localized measurements of phase delay anomalies relative to synthetics computed from the 3d elastic starting model the frechet kernels for our measurements were computed by convolving the earthquake wave fields generated by point earthquake sources with the receiver green tensors rgts which are the spatial temporal fields produced by three orthogonal unit impulsive point forces acting at the receiver locations we inverted 7364 phase delay measurements of p and s body waves by using the lsqr method the revised 3d model laf3d provides substantially better fit to the observed waveform data than the 3d starting model to our knowledge this study is the first successful application of f3dt using real data in structural seismology

error and energy budget analysis of a nonhydrostatic stretched grid global atmospheric model abstracta nonhydrostatic stretched grid sg model is used to analyze the large scale errors generated by stretching horizontal grids and their influence on a region of interest simulations by a fully compressible nonhydrostatic global atmospheric model the nonhydrostatic icosahedral atmospheric model nicam and its sg regional model stretched nicam were performed for the months of march april and may of 2011 using various resolutions and stretching factors a comparison of week long accumulative precipitation amounts between the tropical rainfall measuring mission trmm satellite data and the quasi uniform and sg simulations showed that a stretched run better represents storms and associated precipitation because the errors generated in the outer regions with coarser grid spacing do not significantly affect the inner domain centered at the focal point for season long simulations in one particular set of stretched runs with the focal point located in the eastern united states the artificial s

strong ground motion in the taipei basin from the 1999 chi chi taiwan earthquake the taipei basin located in northwest taiwan about 160 km from the epicenter of the chi chi earthquake is a shallow triangular shaped basin filled with low velocity fluvial deposits there is a strong velocity contrast across the basement interface of about 600 m sec at a depth of about 600 700 m in the deeper section of the basin suggesting that ground motion should be amplified at sites in the basin in this article the ground motion recordings are analyzed to determine the effect of the basin both in terms of amplifications expected from a 1d model of the sediments in the basin and in terms of the 3d structure of the basin residuals determined for peak acceleration from attenuation curves are more positive amplified in the basin average of 5 3 cm sec 2 compared to 24 2 cm sec 2 for those stations outside the basin and between 75 and 110 km from the surface projection of the faulted area a 40 increase in peak ground acceleration residuals for peak velocity are also significantly more positive at stations in the basin 31 8 cm sec compared to 20 0 cm sec out the correlation of peak motion with depth to basement while minor in peak acceleration is stronger in the peak velocities record sections of ground motion from stations in and around the taipei basin show that the largest long period arrival which is coherent across the region is strongest on the vertical component and has a period of about 10 12 sec this phase appears to be a rayleigh wave probably associated with rupture at the north end of the chelungpu fault records of strong motion from stations in and near the basin have an additional higher frequency signal nearest the deepest point in the basin the signal is characterized by frequencies of about 0 3 0 4 hz these frequencies are close to simple predictions using horizontal layers and the velocity structure of the basin polarizations of the s wave are mostly coherent across the array although there are significant differences along the northwest edge that may indicate large strains across that edge of the basin the length of each record after the main s wave are all longer at basin stations compared to those outside this increase in duration of ground shaking is probably caused by amplification of ground motion at basin stations although coda q 0 67 1 30 hz is slightly larger inside the basin compared to those at local stations outside the basin durations correlate with depth to basement these motions are in the range that can induce damage in buildings and may have contributed to the structural collapse of multistory buildings in the taipei basin

the seismic response of the los angeles basin california using strong motion data recorded in the los angeles region from the 1992 mw 7 3 landers earthquake we have tested the accuracy of existing three dimensional 3d velocity models on the simulation of long period 2 sec ground motions in the los angeles basin and surrounding san fernando and san gabriel valleys first the overall pattern and degree of long period excitation of the basins were identified in the observations within the los angeles basin the recorded amplitudes are about three to four times larger than at sites outside the basins amplitudes within the san fernando and san gabriel valleys are nearly a factor of 3 greater than surrounding bedrock sites then using a 3d finite difference numerical modeling approach we analyzed how variations in 3d earth structure affect simulated waveforms amplitudes and the fit to the observed patterns of amplification significant differences exist in the 3d velocity models of southern california that we tested magistrale et al 1996 graves 1996a hauksson and haase 1997 major differences in the models include the velocity of the assumed background models the depth of the los angeles basin and the depth location and geometry of smaller basins the largest disparities in the response of the models are seen for the san fernando valley and the deepest portion of the los angeles basin these arise in large part from variations in the structure of the basins particularly the effective depth extent which is mainly due to alternative assumptions about the nature of the basin sediment fill the general ground motion characteristics are matched by the 3d model simulations validating the use of 3d modeling with geologically based velocity structure models however significant shortcomings exist in the overall patterns of amplification and the duration of the long period response the successes and limitations of the models for reproducing the recorded ground motions as discussed provide the basis and direction for necessary improvements to earth structure models whether geologically or tomographically derived the differences in the response of the earth models tested also translate to variable success in the ability to successfully model the data and add uncertainty to estimates of the basin response given input scenario earthquake source models

the dependence of peak horizontal acceleration on magnitude distance and site effects for small magnitude earthquakes in california and eastern north america abstract one hundred and ninety free field accelerograms recorded on deep soil 10 m deep were used to study the near source scaling characteristics of peak horizontal acceleration for 91 earthquakes 2 5 m l 5 0 located primarily in california of the six attenuation relationships developed in this study the one considered most reliable is given by the expression ln p h a 2 5 0 1 0 6 2 3 m l 1 0 ln r 7 2 8 where pha is the mean of the two horizontal components of peak acceleration in g m l is local magnitude r is epicentral distance in kilometers and is a random error term with mean of zero and standard deviation of 0 506 an analysis of residuals based on an additional 171 near source accelerograms from 75 earthquakes indicated that accelerograms recorded in building basements sited on deep soil have 30 per cent lower accelerations and that free field accelerograms recorded on shallow soil 10 m deep have 82 per cent higher accelerations than free field accelerograms recorded on deep soil accelerations recorded on rock were found to be similar in amplitude to those recorded on deep soil a separate analysis of site effects for the imperial valley and oroville regions of california indicated that peak accelerations from individual sites can depart significantly from predictions based on broad site classifications an analysis of residuals based on 27 selected strong motion recordings from 19 earthquakes in eastern north america indicated that near source accelerations associated with frequencies less than about 25 hz are consistent with predictions based on attenuation relationships derived for california once site effects and differences in regional magnitude scales are taken into account

on the coherence of ground motion in the san fernando valley we present an analysis of the coherence of seismic ground motion recorded on alluvial sediments in the san fernando valley california using aftershocks of the 17 january 1994 m w6 7 earthquake recorded at a quasi dense array of portable stations we analyze the coherence of three well recorded magnitude 3 7 to 4 0 events over the frequency range 0 5 to 15 hz and a distance range of 0 5 to 5 3 km all stations are located at sites with broadly similar near site geology characterized by medium to fine grain quaternary alluvial sediments on average relatively high values of coherence are observed for distances up to 3 to 4 km and frequencies up to 2 to 3 hz coherence drops sharply at frequencies near and above 3 hz although average coherence functions are described reasonably well by a log linear relationship with frequency the curves at all distances exhibit a flattening at low frequencies that is not consistent with previous observations of coherence at hardrock sites the distance decay of coherence is also markedly less strong with high coherence values observed over station separations corresponding to multiple wavelengths this may reflect fundamental differences in shallow wave propagation in the two environments with high frequency scattering relatively more dominant in regions of hard rock near surface geology within a sedimentary basin or valley the site response itself generally reflects a resonance phenomenon that may tend to give rise to more uniform ground motions however previous studies have demonstrated the existence of pathological focusing and amplification effects within complex sedimentary basin environments such as the greater los angeles region our results undoubtedly do not quantify the full range of ground motion variability at all sites but rather represent the level of that variability that can be expected and quantified for typical source receiver paths

band of precariously balanced rocks between the elsinore and san jacinto california fault zones constraints on ground motion for large earthquakes a spectacular band of precariously and semiprecariously bal anced rocks extends from riverside to near borrego valley cali fornia about halfway between the elsinore and san jacinto fault zones the rocks are distributed in a band a few kilometers wide midway between the san jacinto and elsinore fault zones an in dication that the distribution is caused by attenuation of strong ground motion from numerous large events along these two fault zones these rocks have apparently been in place for thousands of years and thus place important constraints on ground motions from earthquakes on the basis of field tests and photographic analysis the estimated quasi static toppling accelerations for the precariously balanced rocks are 0 32 6 0 10 g g 5 gravitational acceleration the dynamic toppling accelerations are within this range for earthquakes with waveforms similar to those recorded during the izmit and denali earthquakes these constraints are roughly consistent with the median predicted value of ground mo tion for m7 earthquakes but somewhat lower than 11s ground motion curves and much lower than the values from the 2 in 50 yr hazard maps the evidence from these rocks has importance for some of the assumptions that go into calculating probabilistic seismic hazard assessment including median and standard devia tion of ground motion attenuation curves especially for hard rock for which few instrumental data are available the possible exis tence of random background earthquakes and the smoothing dis tance for historical seismicity

physical models of volcanic eruptions abstract our present understanding of the dynamics of volcanic eruptions is summarized a few important facts about volcanic eruptions are reviewed and outstanding problems are identified current research efforts are aimed at explaining why an eruption may alternate between and pass through different dynamical regimes the basic physics of eruptions are explained from a dynamical point of view with emphasis on the processes acting to fix the gas content of the erupted material the coupling between flow processes and pressure release leads to large changes of decompression rate during ascent in a volcanic conduit the decompression rate may reach very high values which suggests that the kinetics of degassing play an important role accurate values of the solubility of the major magmatic volatile species are required at pressures of

magnitude dependent variance of peak ground acceleration abstract we examine the variability of peak horizontal and vertical accelerations of the large california strong motion data set for the time period 1957 to 1991 and find a statistically significant dependence of the standard error on earthquake magnitude specifically the standard error decreases with increasing magnitude the analysis was conducted using a rigorous methodology that examines both earthquake to earthquake inter event variability and within earthquake intra event variability the magnitude dependence is stronger for inter event variability than intra event variability and stronger for horizontal peak acceleration than for vertical peak acceleration the data from the recent landers big bear and northridge earthquakes are consistent with these results

the effect of time steps and time scales on parametrization suites the problem of intense truncation scale storms that form in high resolution versions of the community atmosphere model version 4 cam4 is studied these storms are characterized by extreme vertical motion and heavy precipitation this problem arises when some individual parametrizations do not produce an atmospheric like state because they are restrained by the time scales assumed in their formulation other unconstrained parametrizations that follow then work in unintended ways the behaviour of the moist parametrization components is examined in cam4 for one typical strong cell at t340 spectral truncation with a 5 min time step the deep and shallow convection parametrizations do not remove instabilities and supersaturation because they have time scales of 1 h and 30 min respectively then the prognostic cloud water scheme which is not constrained by a time scale does remove supersaturation that local release of latent heat drives very strong vertical motion and horizontal convergence which transports even more water vapour into the column exacerbating the problem two simple model problems are introduced that illustrate the ramifications of the time scale and time step mismatch when either the time scales are shortened or the time step is lengthened the convection parametrizations are more active and strong storms do not form copyright 2012 royal meteorological society

aquaplanet experiments using cam s variable resolution dynamical core abstracta variable resolution option has been added within the spectral element se dynamical core of the u s department of energy doe ncar community atmosphere model cam cam se allows for static refinement via conforming quadrilateral meshes on the cubed sphere this paper investigates the effect of mesh refinement in a climate model by running variable resolution var res simulations on an aquaplanet the variable resolution grid is a 2 222 km grid with a refined patch of 0 25 28 km resolution centered at the equator climatology statistics from these simulations are compared to globally uniform runs of 2 and 0 25 a significant resolution dependence exists when using the cam version 4 cam4 subgrid physical parameterization package across scales global cloud fraction decreases and equatorial precipitation increases with finer horizontal resolution resulting in drastically different climates between the uniform grid runs and a physics induced grid imprinting in the var res simulation

exploring a multiresolution approach using amip simulations abstractthis study presents a diagnosis of a multiresolution approach using the model for prediction across scales atmosphere mpas a for simulating regional climate four atmospheric model intercomparison project amip experiments were conducted for 1999 2009 in the first two experiments mpas a was configured using global quasi uniform grids at 120 and 30 km grid spacing in the other two experiments mpas a was configured using variable resolution vr mesh with local refinement at 30 km over north america and south america and embedded in a quasi uniform domain at 120 km elsewhere precipitation and related fields in the four simulations are examined to determine how well the vrs reproduce the features simulated by the globally high resolution model in the refined domain in previous analyses of idealized aquaplanet simulations characteristics of the global high resolution simulation in moist processes developed only near the boundary of the refined region in contrast amip simulations with vr g

topographic slope as a proxy for seismic site conditions and amplification we describe a technique to derive first order site condition maps directly from topographic data for calibration we use global 30 arc sec topographic data and v s 30 measurements here v s 30 refers to the average shear velocity down to 30 m aggregated from several studies in the u s as well as in taiwan italy and australia v s 30 values are correlated against topographic slope to develop two sets of parameters for deriving v s 30 one for active tectonic regions where topographic relief is high and one for stable shields where topography is more subdued by taking the gradient of the topography and choosing ranges of slope that maximize the correlation with shallow shear velocity observations we can recover to first order many of the spatially varying features of sitecondition maps developed for california our site condition map for the low relief mississippi embayment also predicts the bulk of the v s 30 observations in that region despite rather low slope ranges we find that maps derived from the slope of the topography is often well correlated with other independently derived regional scale site condition maps but the latter maps vary in quality and continuity and subsequently also in their ability to match observed v s 30 measurements contained therein alternatively the slope based method provides a simple approach to uniform site condition mapping

new evidence for degassing processes during explosive eruptions measurements of pore size distribution in five samples of pumice formed during explosive eruptions of plinian type show three distinct sizes of vesicle the characteristics of the three pore size populations are similar in the samples although they were collected from plinian deposits of five different volcanoes we interpret the pore size populations as representing the degassing of silicic magma on three very different time scales the coarse population 60 m represents slow vesiculation within the magma chamber over periods of weeks months or years at small levels of gas supersaturation the medium sized population 50 5 m represents rapid vesiculation of magma on ascent to the surface during the plinian eruption over periods of minutes to hours the fine population 5 0 5 m represents bubbles formed during explosive disruption of magma and rapid ejection into the atmosphere involving short time scales a few seconds but large decompression rates

making the most of available site information for empirical ground motion prediction this article proposes a new framework for the inclusion of site effects in empirical ground motion prediction equations gmpes by characterizing stations through their one quarter wavelength velocities and assessed confidence limits the approach is demonstrated for 14 stations of the french accelerometric network reseau accelerometrique permanent this method can make use of all the available information about a given site for example the surface geology the soil profile standard penetration test measurements near surface velocity estimated from the topographic slope depth to bedrock and crustal structure these data help to constrain the velocity profile down to a few kilometers based on a statistical study of 858 real profiles from three different regions japan western north america and france physically realistic profiles are generated that comply with the information available for each site in order to evaluate the confidence limits for the shear wave velocity profiles and derived site amplifications for each station a stochastic method is adopted several thousand profiles are randomly generated based on parameters derived in the statistical study and the constraints available for each station then the one quarter wavelength assumption is used to estimate the amplification for each station it is found that a good knowledge of near surface attenuation i e or q is mandatory for obtaining precise amplification estimates at high frequencies nevertheless the proposed scheme highlights the important differences in the uncertainties of the site amplifications depending on the information available for a given station we suggest that these results could therefore be used when developing gmpes by weighting records from each station depending on the variability in the computed one quarter wavelength velocities this approach relies on the assumption that local site effects are only one dimensional which is far from true especially in sedimentary basins however most gmpes only model one dimensional site effects so this is not an issue specific to this study finally a way to improve this technique is to use earthquakes or noise recorded at the stations to further constrain the shear wave velocity profiles and to consequently derive more accurate one quarter wavelength velocities

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

early crystallization history of alkali olivine basalts diamond craters oregon abstract basaltic lavas form the isolated quaternary volcanic centers of diamond craters and occur at cow lakes in s e oregon the exposed rocks are olivine and plagioclase phyric alkali olivine basalts the holocrystalline groundmasses contain plagioclase titanaugite olivine fe ti oxides and minor apatite and occur in the high alumina greater than 17 petrographic province of the northwestern great basin the whole rock and phenocryst compositions provide enough information to define the equilibrium state of the magmas the solutions to the thermodynamic equations are valid for systems of known bulk composition and can be used to evaluate whether rock compositions are close to magma compositions two of the lavas from diamond craters have whole rock and phenocryst compositions consistent with their being natural melts rock compositions that reflect the effects of crystal separation open systems are recognized by significant differences in predicted versus observed phenocryst modes the p t conditions of phenocryst saturation and the crystallization history of the magmas can be inferred from petrologic data combined with thermodynamic modelling and mass balance constraints the initial melts are inferred to have equilibrated at 0 8 1 0 gpa and 1210 1240 c the majority of the lavas from diamond craters have compositions that reflect olivine and plagioclase crystal separation these lavas can be related to two possible parent rock compositions by small amounts 2 8 by weight of olivine and plagioclase separation

structure and seismic hazard of the ventura avenue anticline and ventura fault california prospect for large multisegment ruptures in the western transverse ranges abstract the ventura avenue anticline is one of the fastest uplifting structures in southern california rising at 5 mm yr we use well data and seismic reflection profiles to show that the anticline is underlain by the ventura fault which extends to seismogenic depth fault offset increases with depth implying that the ventura avenue anticline is a fault propagation fold a decrease in the uplift rate since 30 10 ka is consistent with the ventura fault breaking through to the surface at that time and implies that the fault has a recent dip slip rate of 4 4 6 9 mm yr to the west the ventura fault and fold trend continues offshore as the pitas point fault and its associated hanging wall anticline the ventura pitas point fault appears to flatten at about 7 5 km depth to a detachment called the sisar decollement then step down on a blind thrust fault to the north other regional faults including the san cayetano and red mountain faults link with this system at depth we suggest that below 7 5 km these faults may form a nearly continuous surface posing the threat of large multisegment earthquakes holocene marine terraces on the ventura avenue anticline suggest that it grows in discrete events with 5 10 m of uplift with the latest event having occurred 800 years ago rockwell 2011 uplift this large would require large earthquakes m w 7 7 8 1 involving the entire ventura pitas point system and possibly more structures along strike such as the san cayetano fault because of the local geography and geology such events would be associated with significant ground shaking amplification and regional tsunamis

origins of the 1954 1960 lavas kilauea volcano hawaii major element constraints on shallow reservoir magmatic processes in the 1954 1960 period kilauea volcano hawaii erupted four times summit eruptions occurred in 1954 halemaumau and 1959 kilauea iki and flank eruptions occurred in the lower east rift zone in 1955 and 1960 our analysis demonstrates that the chemical compositions of lavas from each eruption are related solely through fractionation and sorting of the observed phenocryst assemblages we have used pearce element ratio diagrams to make the following observations and inferences 1 the conserved element ratio p k for each eruption has less variance than is expected from analytical uncertainty thus we cannot reject the hypothesis each set of lavas represents a comagmatic suite of compositions 2 where each of the four groups of lava analyses is plotted on a pearce element ratio diagram with axes of si k and 0 5 mg fe 1 5ca 2 75na 0 25al k the data fit a slope of 1 0 therefore we cannot reject the hypothesis the chemical variation in each data set is consistent with sorting of ol pl au 3 each of the 4 groups of lavas has the same mean p k ratio as a result we cannot reject the hypothesis the 1954 1960 lavas originated from a single magma batch or several magmas with identical p k values finally using the most magnesian glass analysis in the kilauea data suite 1959 sg 05 we have modelled the differentiation path with thermodynamic based calculations these calculations predict a liquid line of descent that is consistent with the path inferred from rock and glass analyses therefore the simulations provide an additional test of our hypotheses and corroborate the postulated differentiation model additionally these calculations suggest that differentiation took place at less than 0 3 gpa and extended over a temperature range of between 100 c and 150 c

accounting for site effects in probabilistic seismic hazard analyses of southern california overview of the scec phase iii report this article presents an overview of the southern california earthquake center scec phase iii effort to determine the extent to which probabilistic seismic hazard analysis psha can be improved by accounting for site effects the contri butions made in this endeavor are represented in the various articles that compose this special issue of bssa given the somewhat arbitrary nature of the site effect distinction it must be care fully defined in any given context with respect to psha we define the site effect as the response relative to an attenuation relationship averaged over all damaging earthquakes in the region a diligent effort has been made to identify any attributes that predispose a site to greater or lower levels of shaking the most detailed maps of quaternary geology are not found to be helpful either they are overly detailed in terms of distinguishing different amplification factors or present southern california strong motion observations are inadequate to reveal their superiority a map based on the average shear wave velocity in the upper 30 m however is found to delineate significantly different amplification factors a correlation of amplification with basin depth is also found to be significant implying up to a factor of two difference between the shallowest and deepest parts of the los angeles basin in fact for peak accel eration the basin depth correction is more influential than the 30 m shear wave ve locity questions remain however as to whether basin depth is a proxy for some other site attribute in spite of these significant and important site effects the standard deviation of an attenuation relationship the prediction error is not significantly reduced by making such corrections that is given the influence of basin edge induced waves subsur face focusing and scattering in general any model that attempts to predict ground motion with only a few parameters will have a substantial intrinsic variability our best hope for reducing such uncertainties is via waveform modeling based on first principals of physics finally questions remain with respect to the overall reliability of attenuation re lationships at large magnitudes and short distances current discrepancies between viable models produce up to a factor of 3 difference among predicted 10 in 50 yr exceedance levels part of which results from the uncertain influence of sediment nonlinearity

introduction to special section on how volcanoes work part 2 the special section on how volcanoes work is a collection of some of the nearly 300 papers presented at the hawaii symposium on how volcanoes work held in hilo in january 1987 tilling 1987a the response of the symposium participants to the invitation to submit their papers for consideration in the special section exceeded expectations in all more than 70 manuscripts were received reviewed and handled following regular jgr editorial procedures part 1 of the special section composed of the papers that were processed and accepted in time to meet the production schedule was published in the december 1987 issue of the journal of geophysical research solid earth and planets tilling 1987a even though part 1 contained only eight papers it nonetheless provided a representative sampling of the multidisciplinary nature of the investigations undertaken to improve our understanding of volcanic systems the papers published in part 1 included ground deformation studies on caldera systems dzurisin and yamashita 1987 mortensen and hopkins 1987 geochemical and observational studies of the lava fountains and of volcanic fume during the 1983 1984 activity of pu u o o in kilauea s east rift zone crowe et al 1987 head and wilson 1987 magmatic crystal stratigraphy and theoretical petrology pearce et al 1987 russell 1987 dynamics of active lava lakes tilling 1987b and seismic evidence for a subcrustal intrusive complex beneath the island of oahu hawaii ten brink and brocher 1987

site amplification and attenuation via downhole array seismogram inversion a comparative study of the 2003 miyagi oki aftershock sequence weak motion geotechnical array recordings at 38 stations of the japanese strong motion network kik net from the 2003 m w 7 0 miyagi oki aftershock sequence are used here to quantify the amplification and attenuation effects of near surface formations to incident seismic motion initially a seismic waveform optimization algorithm is implemented for the evaluation of high resolution low strain velocity v s attenuation q s and density profiles at the sites of interest based on the inversion results v s versus q s correlations are developed and scattering versus intrinsic attenuation effects are accounted for in their physical interpretation surface to downhole traditional spectral ratios ssr cross spectral ratios c ssr and horizontal to vertical h v site response estimates are next evaluated and compared while their effectiveness is assessed as a function of the site conditions classified on the basis of the weighted average vs of the upper 30 m v s30 of the formations single and reference station site response estimates are successively compared to surface to rock outcrop amplification spectra and are evaluated by deconvolution of the downhole records based on the inversion results comparison of the observed ssr and estimated surface to rock outcrop amplification spectra illustrates the effects of destructive interference of downgoing waves at the downhole instrument level as a function of the site class site amplification factors are successively computed in reference to the national earthquake hazards reduction program nehrp b c boundary site conditions v s30 760 m sec and results are compared to published values developed on the basis of strong motion data and site response analyses finally weak motion ssr estimates are compared to the mainshock spectra and conclusions are drawn for the implications of soil nonlinearity in the near surface results presented in this article suggest that currently employed site classification criteria need to be reevaluated to ensure intraclass consistency in the assessment of amplification potentials and nonlinearity susceptibility of near surficial soil formations

sensitivity of simulated climate to model resolution abstract dynamical measures of the climate e g winds eddy fluxes simulated by a general circulation model are compared at different horizontal and vertical resolutions for the december january and february period the simulations of the troposphere are found to improve significantly as the horizontal resolution increases in the range of spectral truncations from t21 to t63 little sensitivity is found to changes in vertical resolution between about 2 8 km and 0 7 km vertical grid spacing the improvements in the southern hemisphere troposphere are greater than in the northern hemisphere as the horizontal resolution increases the eddy momentum fluxes and kinetic energies in both hemispheres increase monotonically with horizontal resolution at t63 the southern hemisphere winds eddy fluxes and eddy kinetic energies agree favorably with observations while serious discrepancies are present at lower resolutions in the northern hemisphere the eddy momentum flux at t63 is slightly larger than obser

a scale interaction study on east asian cyclogenesis using a general circulation model coupled with an interactively nested regional model this study newly developed the interactively nested climate model incl using a general circulation model gcm interactively nested with a regional atmospheric model ram one interactive experiment with finer ram topography and another with coarser topography as well as offline versions of each experiment were performed to investigate the effects of subsynoptic scale eddies and subsynoptic scale mountains in northeast asia on the larger scale climate using the gcm with t42 atmosphere and the ram with 40 km mesh size in the incl system the subsynoptic scale eddy effect restrictively increased synoptic scale eddy activity within the ram domain in contrast subsynoptic scale mountains had the effect of robust anticyclonic circulation around the sea of japan and effectively forced larger scale circulation the effect was positively fed back to the mean field and amplified the anticyclonic circulation accompanied by suppressed storm activity in northeast asia the results suggest that subsynoptic scale mountains affect not only subsynoptic scale eddies but also the global climate

calibration of the specific barrier model to earthquakes of different tectonic regions the specific barrier model proposed and developed by papageorgiou and aki 1983a b 1985 provides the most complete yet parsimonious self consis tent description of the faulting process it applies both in the near fault and in the far field region thus allowing for consistent ground motion simulations over the entire frequency range and for all distances of engineering interest the model has been implemented in the stochastic method and calibrated with extended databases of response spectral amplitudes from earthquakes of intraplate regions mainly east ern north america events interplate regions and regions of tectonic extension spu dich et al 1999 database the ensemble average value of a key parameter of the specific barrier model the local stress drop dr l i s 161 bars for interplate earth quakes 114 bars for extensional regime earthquakes and 180 bars for intraplate earthquakes the high frequency source spectral levels of interplate and extensional regime earthquakes deviate significantly from self similar scaling the deviation is most likely caused by the effective source area and or irregularities in the rupture kinematics we account for their overall effects through a high frequency source complexity factor f in the source spectrum of the specific barrier model as a result inter and intraplate source spectra show similar high frequency levels at moderate magnitudes but intraplate earthquakes have higher spectral levels at the larger mag nitudes the interplate soil residuals show clear signs of nonlinear site response whereas only slight signs of such nonlinearity are observed for the extensional data set the regional models calibrated in this study are in reasonably good agreement with other regional attenuation relationships and provide a reliable and physically realistic yet computationally efficient way to model strong ground motions with implications for seismic hazard and risk analysis online material strong motion station and event station pair information

one two and three phase viscosity treatments for basaltic lava flows 1 lava flows comprise three phase mixtures of melt crystals and bubbles while existing one phase treatments allow melt phase viscosity to be assessed on the basis of composition water content and or temperature two phase treatments constrain the effects of crystallinity or vesicularity on mixture viscosity however three phase treatments allowing for the effects of coexisting crystallinity and vesicularity are not well understood we investigate existing one and two phase treatments using lava flow case studies from mauna loa hawaii and mount etna italy and compare these with a three phase treatment that has not been applied previously to basaltic mixtures at etna melt viscosities of 425 30 pa s are expected for well degassed 0 1 w h2o and 135 10 pa s for less well degassed 0 4 wt h2o melt at 1080 c application of a three phase model yields mixture viscosities 45 crystals 25 35 vesicles in the range 5600 12 500 pa s this compares with a measured value for etnean lava of 9400 1500 pa s at mauna loa the three phase treatment provides a fit with the full range of field measured viscosities giving three phase mixture viscosities upon eruption of 110 140 pa s 5 crystals no bubble effect due to sheared vesicles to 850 1400 pa s 25 30 crystals 40 60 spherical vesicles the ability of the three phase treatment to characterize the full range of melt crystal bubble mixture viscosities in both settings indicates the potential of this method in characterizing basaltic lava mixture viscosity

evaluation of empirical ground motion relations in southern california regression analysis to develop empirical ground motion relations that predict ground motion characteristics as a function of magnitude and distance are an essential part of seismic design and probabilistic seismic hazard assessment several different ground motion relations have been presented based on different data and assumptions this study evaluates five that were judged likely to be appropriate for southern california we test them against the strong motion data recorded in this region between 1933 and 1994 for magnitudes between 5 0 and 7 5 and for distances up to 150 km the ground motion parameters examined are peak acceleration and response spectral acceleration sa at 0 3 1 0 and 3 0 sec periods some of the ground motion relations are more consistent than others with the limited set of southern california data but none of them stand out as either best or unacceptable residuals from all of these models indicate that as the magnitude increases the standard deviation decreases at high frequencies but increases for sa 3 0 sec among those found to be most consistent significant differences remain with respect to predicting ground motion under conditions not yet sampled by the existing observational data set e g near source shaking for large earthquakes theoretical simulations are used elsewhere in this report ni et al 2000 anderson 2000 to help resolve these ambiguities the implications with respect to probabilistic seismic hazard assessment are explored in field and petersen 2000

variability of site response in the los angeles urban area this article addresses the variability of site response in the los angeles area and possible structural causes for the observations aftershock records from 231 sites in the san fernando and los angeles basins and the surrounding mountains are used in this study spectral ratios taken with respect to a low amplitude reference site are used to document the variation in site amplification in the frequency range 2 to 6 hz both spatially and with backazimuth to the source at higher frequencies 6 to 10 hz spectral ratios are shown to have greater spatial variability interstation spectral ratios are used to measure the standard deviation among source as a function of station separation an increase in the variation in ground motion is shown to take place at a station separation of 1 km relative site response estimates between nearby stations are used to demonstrate that preferred directions of motion can exist even in areas with no surface topographic effects significant variations in site response exist over short baselines up to a factor of 2 over 200 m that are not explained by differences in surficial geology or shallow shear wave velocity a variety of investigative approaches is used including spectral ratios arrival time variations 1d and 2d waveform modeling and comparison with seismic reflection lines to determine the most likely causes of these observations a correlation is demonstrated between late arrival times of p and s waves and larger site amplification in sherman oaks and northridge this observation in conjunction with waveform modeling and seismic reflection profiles is used to infer that sedimentary structures in the upper 1 to 2 km and topography on the sediment basement interface play an important role in determining site amplification these structures in the form of folds and buried basins focus energy in spatially restricted areas at the surface comparison of displacement waveforms at nearby stations having disparate site amplifications complemented by known shallow shear wave velocities at selected sites is used to support the argument that these structures in some cases can be the dominant factor in the modification of local ground motions

the pacific south american modes and tropical convection during the southern hemisphere winter abstract atmospheric circulation features and convection patterns associated with two leading low frequency modes in the southern hemisphere sh are examined in multiyear global reanalyses produced by ncep ncar and nasa dao the two leading modes referred to as the pacific south american psa modes are represented by the first two eof patterns the two patterns are in quadrature with each other and are dominated by wavenumber 3 in midlatitudes with large amplitudes in the pacific south american sector in the pacific anomalies in the subtropics and in the midlatitudes are opposite in phase taken together the two psa modes represent the intraseasonal oscillation in the sh with periods of roughly 40 days the evolution of the psa modes shows a coherent eastward propagation a composite analysis was conducted to study the evolution of tropical convection and the corresponding circulation changes associated with the psa modes outgoing longwave radiation olr anomaly composites during the mature phase

amplification factors for spectral acceleration in tectonically active regions empirical relationships are developed to predict amplification factors for 5 damped response spectral acceleration period range t 0 01 5 sec as a function of site category we evaluate amplification factors by normalizing response spectral accelerations computed from recordings by reference spectral accelerations derived from a modified attenuation relationship for active regions strong motion sites are categorized according to several schemes which are based on surface geology age only age depositional environment and age material texture shallow 30 m shear wave velocity and geotechnical data criteria for selection of the optimal classification scheme are that the amplification models for categories within the scheme 1 minimize the global dispersion of prediction residuals and 2 are significantly distinct across a broad period range the results of the regressions indicate that the greatest levels of distinction in amplification levels across categories occur for the shallow shear wave velocity scheme but that the dispersion of residuals for this scheme are relatively high for soil sites although not for rock sites conversely schemes based on detailed surface geology generally have the smallest dispersion for soil sites but amplification levels across quaternary categories are only significantly distinct at small periods these findings suggest that detailed surface geology provides an effective means of soil site categorization at small periods whereas shallow shear wave velocity provides an effective means for rock site categorization at small periods at longer periods none of the schemes are optimized relative to both the dispersion and distinction criteria the principal application of the amplification factors is as a modifier of attenuation relations much like a site term the present results significantly reduce the bias associated with the site terms in a widely used attenuation relationship for rock and soft soil site conditions manuscript received 25 february 2002

the scec southern california reference three dimensional seismic velocity model version 2 we describe version 2 of the three dimensional 3d seismic velocity model of southern california developed by the southern california earthquake center and designed to serve as a reference model for multidisciplinary research activities in the area the model consists of detailed rule based representations of the major southern california basins los angeles basin ventura basin san gabriel valley san fernando valley chino basin san bernardino valley and the salton trough embedded in a 3d crust over a variable depth moho outside of the basins the model crust is based on regional tomographic results the model moho is represented by a surface with the depths determined by the receiver function technique shallow basin sediment velocities are constrained by geotechnical data the model is implemented in a computer code that generates any specified 3d mesh of seismic velocity and density values this parameterization is convenient to store transfer and update as new information and verification results become available

determination of shallow shear wave velocity profiles in the cologne germany area using ambient vibrations summary we have used both single station and array methods to determine shallow shear velocity site profiles in the vicinity of the city of cologne germany from ambient vibration records based on fk analysis we assume that fundamental mode rayleigh waves dominate the analysed wavefield in the frequency range of 0 7 2 2 hz according to this view a close relation exists between h v spectral ratios and the ellipticity of the contributing rayleigh waves the inversion of the shape of h v spectral ratios then provides quantitative information concerning the local shear wave velocity structure however based on tests with synthetic data believed to represent a typical situation in the lower rhine embayment dispersion curves were found to provide stronger constraints on the absolute values of the velocity depth model than the ellipticities the shape of the ellipticities was found to be subject to a strong trade off between the layer thickness and the average layer velocity we have made use of this observation by combining the inversion schemes for dispersion curves and ellipticities such that the velocity depth dependence is essentially constrained by the dispersion curves while the layer thickness is constrained by the ellipticities in order to test this method in practice we have used array recordings of ambient vibrations from three sites where the subsurface geology is fairly well known and geotechnical information is at least partially available in order to keep the parameter space as simple as possible we attempted to fit only a single layer over a half space model however owing to earlier studies from the region we assume a power law depth dependence for sediment velocities for all three sites investigated the inversion resulted in models for which the shear wave velocity within the sediment layer both in absolute value at the surface and in depth dependence are found to be remarkably similar to the results obtained by budny from downhole measurements this is strong support for the interpretation of h v spectral ratios as rayleigh wave ellipticities for all three sites the predicted sh wave site amplification factors at the fundamental frequency are of the order of 5 6 with a slightly smaller value south of cologne

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

stationary eddy response to surface boundary forcing idealized gcm experiments abstract a set of atmospheric general circulation model agcm experiments under idealized conditions is performed to investigate atmospheric response to surface boundary forcing by extratropical land sea contrast large scale orography and tropical sea surface temperature sst distribution stationary eddies forced by the extratropical land sea distribution are strongest in high latitudes but their amplitudes are modest and comparable to internal chaotic variability by contrast the stationary eddy response to zonal variations in tropical sst is strong and robust in both the subtropics and midlatitudes while these sst forced stationary waves are trapped within the troposphere those induced by orography show a strong vertical propagation into the stratosphere analysis of transient eddies indicates that orography is effective in generating a zonally localized storm track while extratropical land sea contrast has little effect on the zonal variation of upper level storm activity a vorticity budget a

single station earthquake characterization for early warning we use data from 50 earthquakes in southern california to test the accuracy of event parameter determination using single seismic stations for the pur pose of early warning earthquake magnitude hypocentral distance and backazimuth are all estimated using p wave arrivals only there is a wide range in the accuracy of event parameters determined by different seismic stations one quarter of the stations produced magnitude estimates with errors less than 0 3 magnitude units hypocentral distances within 15 km and backazimuth calculations within 20 this accuracy is sufficient to provide useful early warning using p wave arrivals is the most rapid method of delivering earthquake early warning and may permit a few seconds notice of impending ground motion even in the epicentral region our results show that networks using a p wave detection approach for early warning can increase the accuracy of magnitude estimations by determining station specific scaling rela tions between the predominant period of the p wave and event magnitude and by utilizing stations with optimal relations further because individual stations are able to deliver an accurate early warning the option of utilizing the technology in regions that lack a dense seismic network but are in need of seismic hazard mitigation be comes possible

lillooet glacier basalts southwestern british columbia canada products of quaternary glaciovolcanism the retreat of lillooet glacier lg has exposed a succession of pillow basalt and subordinate amounts of breccia and hyaloclastite the lithofacies and physiographic setting suggest that the deposits have a glaciovolcanic origin and represent a partially dissected basaltic pillow dominated tindar chemically the lg volcanic rocks are basalt to basaltic andesite and as a group they represent the highest silica quaternary mafic products in the garibaldi volcanic belt gvb like other northern gvb alkaline basalts they lack the nb ta depletion signature typically associated with subduction related products geochemical and petrologic analysis indicates that the lg basalts are comagmatic and that chemical variations within the suite are consistent with sorting of the observed phenocryst assemblage olivine plagioclase thermodynamic modeling establishes shallow crustal pre eruptive storage conditions at 2 kbar 1 kbar 100 mpa or 7 5 km and an h2o content of 0 5 1 wt we estimate that the

groundmass crystallization of mount st helens dacite 1980 1986 a tool for interpreting shallow magmatic processes the 1980 1986 eruption of mount st helens volcano provides an unprecedented opportunity to observe the evolution of a silicic magma system over a short time scale groundmass plagioclase size measurements are coupled with measured changes in matrix glass plagioclase and fe ti oxide chemistry to document increasing groundmass crystallinity and thus to better constrain proposed physical models of the post may 18 1980 magmatic reservoir measurements of plagioclase microlite and microphenocryst sizes demonstrate that relatively rapid growth approximately 10 9 cm s of groundmass plagioclase occurred immediately subsequent to may 18 relatively rapid plagioclase growth continued through the end of 1980 at an average rate of 3x10 11 cm s plagioclase growth rates then decreased to 1x10 11 cm s through 1986 changes in groundmass crystallinity are reflected in changes in both matrix glass and plagioclase microphenocryst rim chemistry although the matrix glass composition appears to have remained approximately constant from 1981 1986 after a rapid compositional change from may 18 until the end of 1980 plagioclase microphenocrysts show increasingly more complex zoning patterns with time microphenocryst core compositions are commonly positively correlated with crystal size both of these observations indicate continuous groundmass plagioclase growth through 1986 magmatic temperatures estimated from fe ti oxide pairs are approximately constant through 1981 at eruption temperatures of 930 c and at log fo2 of 10 8 by 1985 1986 oxide temperatures decreased to 870 c chemical and textural changes can be explained by 1 rapid degassing and crystallization in response to the intrusion of magma into a shallow 4 5 km reservoir toward the end of the may 18 1980 eruption 2 continued crystallization at a much reduced rate through 1986 due to slow cooling of the shallow magma reservoir growth rates and consequent chemical changes appear to decrease at the end of 1980 this is coincident with the change in eruption style from explosive eruptions sometimes followed by dome growth to solely extrusive dome building events and can be explained by the expected viscosity increase of both degassing and increasing crystallinity the model of twostage crystallization of magma in a shallow reservoir is consistent with conclusions from gas studies casadevall et al 1983 gerlach and casadevall 1986 a b patterns of crater deformation chadwkck et al 1988 and post 1980 seismicity endo et al 1990 although it does not explain the experimental data of hill and rutherford 1989 on the growth rate of amphibole reaction rims textural measurements on mount st helens dacite can also be used to evaluate crystallization kinetics in silicic magmas systems for which experimental data is almost non existent plagioclase growth rates are 5 10 times slower than estimated plagioclase growth rates in basaltic systems a result consistent with the higher viscosity of a more silicic melt furthermore patterns of textural change both average crystal size and number density are similar to those observed during the 1984 mauna loa eruption by lipman and banks 1987 suggesting that the only modification to the crystallization behavior of plagioclase required in extrapolation from basaltic systems is a moderate decrease in rates such that the rate of crystallization scales with the melt viscosity

site response in southern california for probabilistic seismic hazard analysis this study determines site response factors that can be applied as cor rections to a rock attenuation relationship for use in probabilistic seismic hazard analysis the site response factors are amplitude and site class dependent these amplification factors are determined by averaging ratios between observed and pre dicted ground motions for peak ground acceleration pga and for 5 damped re sponse spectral acceleration at 0 3 1 0 and 3 0 sec oscillator periods the observa tions come from the strong motion database of the southern california earthquake center scec and the predictions are based on the sadigh 1993 rock attenuation relation when separated and averaged according to surface geology significantly different site response factors are found for quaternary and mesozoic units but a subclassification of quaternary is generally not justified by the data the low input motion amplification factors are consistent with those obtained from independent aftershock studies at the pga and 0 3 second period an observed trend of decreasing quaternary site amplification with higher input motion is consistent with nonlinear soil behavior however the trend exists for mesozoic sites as well implying that this may be an artifact of the sadigh relationship there is a correlation between larger site response factors and lower average shear wave velocity in the upper 30 m for low predicted pga input motions with an increase in the correlation with increasing period the 0 3 sec site response factors for quaternary data in southern california determined in this study are consistent with 0 3 sec nehrp site response correction factors however at 1 0 sec period some inconsistencies remain a trend is also seen with respect to sediment basin depth where deeper sites have higher average site response factors these results constitute a customized attenuation relationship for southern california the implication of these customized attenuation models with respect to probabilistic hazard analysis is examined in field and petersen 2000

the impact of convection on enso from a delayed oscillator to a series of events abstract the ncar community climate system model version 3 ccsm3 exhibits persistent errors in its simulation of the el nino southern oscillation enso mode of coupled variability the amplitude of the oscillation is too strong the dominant 2 yr period too regular and the width of the sea surface temperature response in the pacific too narrow with positive anomalies extending too far into the western pacific two changes in the parameterization of deep convection result in a significant improvement to many aspects of the enso simulation the inclusion of convective momentum transport cmt and a dilution approximation for the calculation of convective available potential energy cape are used in development integrations and a striking improvement in enso characteristics is seen an increase in the periodicity of enso is achieved by a reduction in the strength of the existing short circuited delayed oscillator mode the off equatorial response is weaker and less tropically confined largely as a

nonlinear sediment response during the 1994 northridge earthquake observations and finite source simulations we have addressed the long standing question regarding nonlinear sediment response in the los angeles region by testing whether sediment amplification was similar between the northridge earthquake and its aftershocks comparing the weak and strong motion site response at 15 sediment sites we find that amplification factors were significantly less for the main shock implying systematic nonlinearity the difference is largest between 2 and 4 hz a factor of 2 and is significant at the 99 confidence level between 0 8 and 5 5 hz the inference of nonlinearity is robust with respect to the removal of possibly anomalous sediment sites and how the reference site motion is defined furthermore theoretical ground motion simulations show no evidence of any bias from finite source effects during the main shock nonlinearity is also suggested by the fact that the four sediment sites that contain a clear fundamental resonance for the weak motion exhibit a conspicuous absence of the peak in the strong motion although we have taken the first step of establishing the presence of nonlinearity it remains to define the physics of nonlinear response and to test the methodologies presently applied routinely in engineering practice the inference of nonlinearity implies that care must be exercised in using sediment site data to study large earthquakes or predict strong ground motion

response spectral attenuation relations for shallow crustal earthquakes in taiwan article i nfo attenuation relationship crustal earthquakes strong ground motion peak ground acceleration spectral acceleration hanging wall effect in this study a local set of response spectral attenuation equations developed for seismic hazard analysis in taiwan are introduced as an example for determining the local strong motion attenuation relationship for a region strong ground motion data for shallow crustal earthquakes are obtained from the taiwan strong motion instrumentation program tsmip these data are used to establish peak ground acceleration pga and response spectral acceleration sa attenuation equations taking into consideration both hanging wall effects and site conditions the obtained results show that the local set of attenuation equations gives significantly lower values of pga and sa for structural periods shorter than 0 3 s as compared to a set of global relations obtained from international data the sas obtained for structural periods longer than 0 3 s are similar to those obtained for global sets this indicates that developing a local set of ground motion attenuation equations is necessary for more accurate prediction of ground motion values

the scec phase iii strong motion database as part of the southern california earthquake center scec phase iii effort to include site effects in hazard models for southern california a regional database of strong motion observations was developed the observations consist of the peak ground acceleration pga and 5 damped response spectral acceleration sa at 0 3 1 0 and 3 0 sec periods from 28 earthquakes and 281 stations a total of 449 pairs of horizontal pga and sa observations that were taken from the scec strong motion database smdb are presented here the phase iii database includes earthquakes with moment magnitudes larger than 5 0 and stations in southern california with locations between 32 and 36 north latitude observations from buildings with more than two stories and dam abutments or crests are excluded from the database observations with distances of 150 km or greater were also excluded the agencies that provided the data to smdb are the u s geological survey california strong motion instrumentation program university of southern california and the los angeles department of water and power the database also contains site classification information for each station a first general classification is based on the 1 750 000 california map of quaternary tertiary and mesozoic geologic units by jennings 1977 as modified by park and elrick 1998 a second more detailed classification is based on quaternary mapping in the los angeles region by tinsley and fumal 1985 as modified by park and elrick 1998 a third classification is based on the correlation of surface geology with shear wave velocity in the upper 30 m wills et al 2000 an arbitrary depth to basement parameter is assigned to stations that are located within the boundary of the 3d velocity model used by olsen 2000 which is based on the scec 3d velocity model version 1 this parameter is defined as the depth to the 2 5km sec velocity isosurface special parameters associated with particular attenuation relations such as different distance measures a hanging wall flag and fault type flag are also assigned to each observation these data are all presented within the tables and figures of this article and also have been made available via a downloadable file on the internet http smdb crustal ucsb edu phase3

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

mechanical models favor a ramp geometry for the ventura pitas point fault california recent investigations have provided new and significantly revised constraints on the subsurface structure of the ventura pitas point fault system in southern california however few data directly constrain fault surfaces below 6 km depth here we use geometrically complex three dimensional mechanical models driven by current geodetic strain rates to test two proposed subsurface models of the fault system we find that the model that incorporates a ramp geometry for the ventura pitas point fault better reproduces both the regional long term geologic slip rate data and interseismic gps observations of uplift in the santa ynez mountains the model calculated average reverse slip rate for the ventura pitas point fault is 3 5 0 3 mm yr although slip rates are spatially variable on the fault surface with 8 mm yr predicted on portions of the lower ramp section at depth

effects of the hanging wall and footwall on ground motions recorded during the northridge earthquake abstract systematic differences in ground motion on the hanging wall and footwall during the northridge earthquake are evaluated using empirical data an empirical model for the hanging wall effect is developed for the northridge earthquake this empirical model results in up to a 50 increase in peak horizontal accelerations on the hanging wall over the distance range of 10 to 20 km relative to the median attenuation for the northridge earthquake in contrast the peak accelerations on the footwall are not significantly different from the median attenuation over this distance range recordings from other reverse events show a similar trend of an increase in the peak accelerations on the hanging wall indicating that this systematic difference in hanging wall peak accelerations is likely to be observed in future reverse events

site response for urban los angeles using aftershocks of the northridge earthquake ground motion records from aftershocks of the 1994 northridge earthquake are used to estimate site response in the urban los angeles area over 1300 shear wave records from 61 sources and 90 sites are used in a linear inversion for source and site response spectra the methodology makes no assumptions about the shape of the source spectrum to obtain a stable unique inverse a q model and geometrical spreading factor are assumed in addition the site response at a hard rock site is constrained to be approximately 1 0 with a kappa of 0 02 the site response spectra compare favorably with the results of previous and on going investigations in los angeles a couple of first order effects are lower site response in the surrounding mountains dominated by mesozoic and tertiary rocks and higher values in the san fernando and los angeles basins containing surficial pleistocene and holocene alluvial deposits results show good correlation of high site response spectral values with localized areas of severe damage interstate 10 collapse sherman oaks northridge interstate 5 14 collapse however widespread trends in site response across the sedimentary basins are not obvious the data suggest that site responses are lower near the southern margin of the san fernando valley for sources to the north due to north dipping sedimentary structures but the general pattern of site response is characterized by high variability on length scales less than a kilometer variations of a factor of 2 in site response are observed over the length scale of 200 m and for the same surficial geologic unit for some of the alluvial basin sites surface wave generation is a significant contributor to elevated site response at lower frequencies below 2 hz the total damage pattern for the northridge earthquake is influenced by strong source directivity to the north and strong local site effects the correlation of weak motion site response estimates with areas of significant damage demonstrates the value of these field measurements in future urban planning and in the reduction of seismic risk in urban areas

influences of north pacific ocean domain extent on the western u s winter hydroclimatology in variable resolution cesm author s rhoades am jones ad o brien ta o brien jp ullrich pa zarzycki cm abstract 2020 american geophysical union all rights reserved variable resolution global climate models vrgcms are a dynamical downscaling method that can reach spatiotemporal scales needed for regional climate assessments over the years several users of vrgcms have assumed where the location and extent of the refinement domain should be based on knowledge of the prevailing storm tracks and resolution dependence of important regional climate processes e g atmospheric rivers ars and orographic uplift but the effect of high resolution domain size and extent on the simulation of downstream hydroclimatic phenomena has not been systematically evaluated here we use variable resolution in the community earth system model vr cesm to perform such a test to do this three vr cesm grids were generated that span the entire two thirds and one third of the north pacific and evaluated for a 30 year climatology using atmospheric model intercomparison project protocols simulations are compared with reanalysis products offshore fifth generation of the european centre for medium range weather forecasts atmospheric reanalysis era5 and onshore livneh 2015 https doi org 10 1038 sdata 2015 42 and parameter elevation regressions on independent slopes model prism of the western united states the westward expansion of refinement domain influenced integrated vapor transport ivt which was generally high biased but minimally impacted ar characteristics due to slight differences in landfalling ar counts in the western united states california winter precipitation generally improved with westward expansion of the refinement domain western u s mountain snowpack and surface temperatures were insensitive to refinement domain size and were more influenced by changes in topographic resolution and or land surface model version given minimal dependence of simulated western u s hydroclimate on refinement domain size over the north pacific we advise future vr cesm studies to focus grid resolution on better resolving land surface heterogeneity

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

the zonal asymmetry of the southern hemisphere winter storm track atmospheric general circulation model experiments have been performed to investigate how the significant zonal asymmetry in the southern hemisphere sh winter storm track is forced by sea surface temperature sst and orography an experiment with zonally symmetric tropical ssts expands the sh upper tropospheric storm track poleward and eastward and destroys its spiral structure diagnosis suggests that these aspects of the observed storm track result from rossby wave propagation from a wave source in the indian ocean region associated with the monsoon there the lower tropospheric storm track is not sensitive to this forcing however an experiment with zonally symmetric midlatitude ssts exhibits a marked reduction in the magnitude of the maximum intensity of the lower tropospheric storm track associated with reduced sst gradients in the western indian ocean experiments without the elevation of the south african plateau or the andes show reductions in the intensity of the major storm track downstream of them due to reduced cyclogenesis associated with the topography these results suggest that the zonal asymmetry of the sh winter storm track is mainly established by stationary waves excited by zonal asymmetry in tropical sst in the upper troposphere and by local sst gradients in the lower troposphere and that it is modified through cyclogenesis associated with the topography of south africa and south america

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

density changes during the fractional crystallization of basaltic magmas fluid dynamic implications the dynamical behaviour of basaltic magma chambers is fundamentally controlled by the changes that occur in the density of magma as it crystallizes in this paper the term fractionation density is introduced and defined as the ratio of the gram formula weight to molar volume of the chemical components in the liquid phase that are being removed by fractional crystallization removal of olivine and pyroxene whose values of fractionation density are larger than the density of the magma causes the density of residual liquid to decrease removal of plagioclase with fractionation density less than the magma density can cause the density of residual liquid to increase during the progressive differentiation of basaltic magma density decreases during fractionation of olivine olivine pyroxene and pyroxene assemblages when plagioclase joins these mafic phases magma density can sometimes increase leading to a density minimum calculations of melt density changes during fractionation show that compositional effects on density are usually greater than associated thermal effects in the closed system evolution of basaltic magma several stages of distinctive fluid dynamical behaviour can be recognised that depend on the density changes which accompany crystallization as well as on the geometry of the chamber in an early stage of the evolution where olivine and or pyroxenes are the fractionating phases compositional stratification can occur due to side wall crystallization and replenishment by new magma with the most differentiated magma tending to accumulate at the roof of the chamber when plagioclase becomes a fractionating phase a zone of well mixed magma with a composition close to the density minimum of the system can form in the chamber the growth of a zone of constant composition destroys the stratification in the chamber a chamber of well mixed magma is maintained while further differentiation occurs unless the walls of the chamber slope inwards in which case dense boundary layer flows can lead to stable stratification of cool differentiated magma at the floor of the chamber in a basaltic magma chamber replenished by primitive magma the new magma ponds at the base and evolves until it reaches the same density and composition as overlying magma successive cycles of replenishment of primitive magma can also form compositional zonation if successive cycles occur before internal thermal equilibrium is reached in a chamber in a chamber containing well mixed plagioclase saturated magma the primitive magma can be either denser or lighter than the resident magma in the first case the new magma ponds at the base and fractionates until it reaches the same density as the evolved magma mixing then occurs between magmas of different temperatures and compositions in the second case a turbulent plume is generated that causes the new magma to mix immediately with the resident magma