integrated use of seismograph and strong motion data to determine soil amplification response of the fraser river delta to the duvall and georgia strait earthquakes we present a new method to estimate site amplification in which re gional seismographic data are used to constrain the input motions to the soil profile the empirical inferred amplification is determined as the ratio of the fourier spec trum of the recorded motion on soil to the spectrum of the inferred input motion at the underlying bedrock interface the method is demonstrated for sites on the fraser river delta british columbia b c that recorded the 1996 m 5 1 duvall wash ington and 1997 m 4 3 georgia strait b c earthquakes regional seismographic recordings on rock sites are used to determine the apparent source spectra of these events these spectra are attenuated to sites in the fraser river delta then input to a specified soil profile we compare the empirical inferred amplification to alternative estimates of the soil amplification based on 1 the quarter wavelength approach and 2 the assumption that the amplification is approximately equal to the observed h v ratio the empirical inferred amplification estimates are grossly consistent with the theoretical amplification estimates but have larger peaks at specific frequencies probably due to resonant effects not accounted for in the quarter wavelength ap proach the h v ratio appears to be a simple and useful first approximation to the site response the fraser river delta amplifies weak motions by factors of three to six over a broad frequency range from 0 2 to 4 hz high frequency motions f 10 hz are attenuated the long period amplifications pose a serious concern in the event of strong earthquake shaking from large earthquakes a useful by product of the analysis is the determination of apparent source spectra for the events the apparent source spectrum of the georgia strait earthquake is in good agreement with the brune point source model with a stress drop of approxi mately 45 bars the apparent source spectrum of the slightly larger duvall earthquake is in reasonable agreement with the brune model with a stress drop of about 70 bars however for the duvall earthquake there is evidence of a sag in spectral amplitudes relative to the brune model at intermediate frequencies 0 3 to 1 hz this inter mediate frequency sag is an expected result of source complexity it is well dem onstrated by the broadband seismic data

moment magnitude local magnitude calibration for earthquakes off canada s west coast local magnitude m l values of earthquakes off canada9s west coast are known to be underestimated by at least 0 5 magnitude units compared with other magnitude scales moment magnitude m w derived from moment tensor analysis provides the most robust estimate of the magnitude of earthquakes moment tensor analysis of regional seismic data in western canada is now possible due to the installation of more than 40 three component broadband stations in western canada the u s pacific northwest and southeast alaska moment tensor solutions are now possible down to m 4 0 more than 230 regional moment tensor solutions have been calculated off canada9s west coast at the geological survey of canada for 1995 2002 these solutions along with 14 previous solutions by oregon state university in 1994 1995 and 13 harvard solutions for 1984 1993 allow a systematic m w m l calibration for earthquakes in this region the study area extends from the queen charlotte islands region in the north to the area off the west coast of southern vancouver island at the northern end of the study area where there is little oceanic crust in the source receiver travel path m w is systematically larger than m l by 0 28 0 08 magnitude units at the southern end of the study area where there is a significant amount of ocean crust in the source receiver travel path m w is systematically larger than m l by 0 62 0 08 magnitude units calibration of m l with m w will allow the western canadian earthquake database to be used more effectively for tectonic studies and seismic hazard analysis

deep weathering of a group of thick argillaceous limestone rocks near three gorges reservoir central china rock mass characterization is one of the most basic and important tasks in rock mechanics and engineering literature review indicates that although there are many publications available on weathered rocks there are few reports in english on weathered argillaceous limestone rocks and their chemical and mechanical properties this paper presents a case study of characterizing a group of highly weathered thick argillaceous limestone rocks most importantly they can be easily and quickly decomposed into soils after they are exposed due to excavation consequently they would substantially lose their mechanical strengths geohazards such as landslides and sinkholes could occur in uncovered highly weathered argillaceous limestone rocks the problematic weathered rocks were found during the development of a new town in upper mountains above the three gorges reservoir on yangtze river in central china in the past 20 years the factual data are presented on the changes of chemical compositions and mechanical properties of the weathered argillaceous limestone rocks due to chemical weathering some empirical correlations are given to quantify the changes in their uniaxial compressive strength and deformation moduli in terms of their contents of calcium carbonate the data and findings presented in the paper can be useful to future urban development in geologically poor mountainous environments occupied by highly weathered argillaceous limestone rocks in the world

a comparison of ground motions from the 2001 m 6 8 in slab earthquakes in cascadia and japan are earthquake source and propagation properties for in slab earthquakes in the cascadia region british columbia and washington state similar to those in the subduction zone of southwest japan to answer this question we compare ground motions for two recent earthquakes of similar magnitude and depth the comparisons are made for horizontal component 5 damped response spectral acceleration at frequencies from 0 5 to 10 hz the selected cascadia event is the nisqually earthquake of 28 february 2001 which occurred within the subducting juan de fuca plate with a moment magnitude of m 6 8 at a depth of 51 km the japan event is the geiyo earthquake of 24 march 2001 with m 6 8 at a depth of 60 km within the subducting philippine sea plate generally the response spectral amplitudes from the two events overlay each other when amplitudes are plotted against distance an interesting relationship is observed however at low frequencies 0 5 1 hz the nisqually data tend to have higher amplitudes whereas at high frequency 5 10 hz the nisqually data have lower amplitudes in comparison to the geiyo data the observed drop through of the nisqually data relative to the geiyo data as frequency increases could be due to either source effects or site effects it is not a path effect because there is no indication of differences in the slope of the attenuation curve if the observed frequency dependent amplitude differences are due to source effects this could imply that in slab earthquakes in japan are fundamentally different from those that occur in the cascadia subduction zone this would have important implications as it would cast doubt on the applicability of lessons learned in japan to hazard assessment in cascadia on the other hand if the observed differences are attributable to site effects then japanese observations and results are applicable to cascadia once we have accounted for differences in site effects to address the origin of the observed differences in ground motion between the nisqually and geiyo earthquakes we evaluate the influence of site effects on the recorded motions we correct all response spectra to an equivalent rock motion using amplifications derived from quarter wavelength site response calculations for representative regional soil profiles the site corrected rock motions from nisqually and geiyo are in reasonable agreement with each other at all frequencies with the exception of some nisqually observations from west seattle we conclude that the observed differences between the nisqually and geiyo ground motions are attributable to regional differences in site response

empirical ground motion relations for subduction zone earthquakes and their application to cascadia and other regions ground motion relations for earthquakes that occur in subduction zones are an important input to seismic hazard analyses in many parts of the world in the cascadia region washington oregon northern california and british columbia for example there is a significant hazard from megathrust earthquakes along the subduction interface and from large events within the subducting slab these hazards are in addition to the hazard from shallow earthquakes in the overlying crust we have compiled a response spectra database from thousands of strong motion record ings from events of moment magnitude m 5 8 3 occurring in subduction zones around the world including both interface and in slab events the 2001 m 6 8 nis qually and 1999 m 5 9 satsop earthquakes are included in the database as are many records from subduction zones in japan kyoshin net data mexico guerrero data and central america the size of the database is four times larger than that available for previous empirical regressions to determine ground motion relations for subduc tion zone earthquakes the large dataset enables improved determination of attenu ation parameters and magnitude scaling for both interface and in slab events soil response parameters are also better determined by the data we use the database to develop global ground motion relations for interface and in slab earthquakes using a maximum likelihood regression method we analyze regional variability of ground motion amplitudes across the global database and find that there are significant regional differences in particular amplitudes in cascadia differ by more than a factor of 2 from those in japan for the same magnitude distance event type and national earthquake hazards reduction program nehrp soil class this is believed to be due to regional differences in the depth of the soil profile which are not captured by the nehrp site classification scheme regional correction factors to account for these differences are proposed for cascadia and japan the results of this study differ significantly from previous analyses based on more limited data and have important implications for seismic hazard analysis the ground motion relations predict that a great megathrust earthquake m 8 at a fault distance of about 100 km would produce pseudoacceleration psa 5 damped horizontal component on soil sites of about 110 cm sec 2 at 0 5 hz 660 cm sec 2 at 2 5 hz and 410 cm sec 2 at 5 hz with a peak ground acceleration of about 180 cm sec 2 these damaging levels of motion would be experienced over a very large area corresponding to a rectangular area about 300 km wide by 500 km long large in slab events m 7 5 would produce even higher psa values within 100 km of the fault but the in slab motions attenuate much more rapidly with distance thus the hazard posed by moderate to large in slab events such as the 2001 nisqually earth quake is modest compared to that of a cascadia megathrust earthquake of m 8 in terms of the area that would experience damaging levels of ground motion

ambient noise cross correlation observations of fundamental and higher mode rayleigh wave propagation governed by basement resonance measurement of basement seismic resonance frequencies can elucidate shallow velocity structure an important factor in earthquake hazard estimation ambient noise cross correlation which is well suited to studying shallow earth structure is commonly used to analyze fundamental mode rayleigh waves and increasingly love waves here we show via multicomponent ambient noise cross correlation that the basement resonance frequency in the canterbury region of new zealand can be straightforwardly determined based on the horizontal to vertical amplitude ratio h v ratio of the first higher mode rayleigh waves at periods of 1 3 s the first higher mode is evident on the radial radial cross correlation functions but almost absent in the vertical vertical cross correlation functions implying longitudinal motion and a high h v ratio a one dimensional regional velocity model incorporating a 1 5 km thick sedimentary layer fits both the observed h v ratio and rayleigh wave group velocity similar analysis may enable resonance characteristics of other sedimentary basins to be determined

high frequency ground motion scaling in the pacific northwest and in northern and central california abstract large data sets of vertical and horizontal seismograms from the pacific northwest seismic network northern california seismic network and berkeley digital seismic network are used to study the high frequency 0 25 16 hz ground motion scaling characteristics in washington oregon northern california 39 n to 42 n and 119 w to 124 w and central california 35 n to 39 n and 118 w to 123 w we used peak filtered ground velocities to characterize the propagation excitation and site terms the regression results for propagation were modeled using a geometrical spreading function g r and a frequency dependent attenuation q f q 0 f for the pacific northwest the best q model that fits the observation is expressed by q f 280 f 0 55 the eastern central california and western central california results are parameterized with q f 280 f 0 50 and q f 240 f 0 35 respectively the northern california results are not easy to model and require using a frequency dependent and a frequency dependent geometrical spreading the geometrical spreading effect for the frequencies higher than 5 hz is very strong in that region the excitation terms for the small events studied were modeled using a brune s source model an average stress drop of 30 bars was obtained for the pacific northwest the northern california average value for stress drop is 90 bars the observations of eastern central california were modeled with a stress drop of 49 bars while the best fit for the western part required 80 bars the range of the values obtained for q g r and indicates that the ground motion parameters for one region should not be used for another as an example our results show that the ground motion amplitude due to an m w 5 0 earthquake at a distance of 50 km is different by a factor of 1 5 between the pacific northwest and eastern central california

bending of the subducting oceanic plate and its implication for rupture propagation of large interplate earthquakes off miyagi japan in the japan trench subduction zone 1 we present the results of an onshore offshore wide angle refraction and reflection experiment off miyagi in the central japan trench forearc region there are two rupture zones of large interplate earthquakes here the landward rupture zone and the trenchward rupture zone to examine the influence of plate boundary geometry on the distributions of the rupture zones we determined reflector geometries from reflections the subducting oceanic plate increases its dip from about 5 to 13 around 143 2 e this bending point in the oceanic plate corresponds to the eastern edge of the trenchward rupture zone moreover another bending point may be present at approximately 142 3 e which corresponds to the eastern edge of the landward rupture zone the coincidence between bending points in the oceanic plate and the edges of rupture zones suggests that changes in the plate boundary geometry may affect rupture propagation of interplate earthquakes in the direction of plate convergence

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

estimation of moment magnitude from ground motions at regional distances abstract we present a simple and robust approach to estimate moment magnitude m for events of m m can be estimated from 1 hz response spectral amplitudes for events in north america with an uncertainty standard deviation of residuals of m across regions and that it provides relationships that are consistent with the predictions of a stochastic point source model for typical regional attenuation models online material table of events for which the moment magnitude was estimated

ground motion attenuation source and site effects for the 26 september 2003 m 8 1 tokachi oki earthquake sequence abstract on 26 september 2003 a megathrust earthquake of m 8 1 occurred at the kurile trench northern japan we used accelerograms recorded on more than 300 k net stations ranging in distance from 40 to 500 km to determine source attenuation and site effects for the mainshock and four aftershocks with m 7 3 6 4 5 9 and 5 5 the analyses are based on linear regression applied to the fourier spectra data of each event the ground motion attenuation for all the events can be modeled using an assumed geometric spreading coefficient b 1 1 0 with an associated anelastic attenuation model given by an apparent q 135 f 0 76 by using dummy variables in the regression site amplifications relative to national earthquake hazard reduction program nehrp c sites are determined for d and e sites nonlinear site amplification was investigated for the m 8 1 data but was not significant in determining the overall amplification factors fourier spectra data were corrected to a reference near source distance and site condition hard rock the source spectrum for each event was compared to that of the theoretical brune model spectrum in order to compute seismic moment and stress drop seismic moments obtained in this manner agree with those of other studies stress drops range from 100 to 200 bars with no apparent dependence on magnitude the mainshock stress drop was 120 bars a similar value 100 bars was calculated for an interface aftershock events with the highest stress drops near 200 bars may have been in slab events

ground motions for earthquakes in southwestern british columbia and northwestern washington crustal in slab and offshore events regional ground motion generation and propagation must be charac terized to adequately assess seismic hazard in the cascadia region of southwestern british columbia and northwestern washington the ground motion issues are par ticularly complex because of the contributions to hazard from five distinct types of events all of which behave differently in terms of their ground motion propagation characteristics 1 shallow earthquakes occurring in the continental crust 2 shallow earthquakes occurring offshore in oceanic crust 3 earthquakes occurring within the subducting juan de fuca slab beneath the continent e g puget sound 4 earth quakes occurring within the subducting juan de fuca slab at the edge of the continent e g transitional events along the west coast of vancouver island and 5 great subduction earthquakes on the interface between the subducting juan de fuca plate and the overriding north american plate in this study empirical data recorded within the cascadia region are used to evaluate the source and attenuation characteristics of ground motion amplitudes from the first four of these event types crustal off shore in slab and transitional and examine their implications for regional ground motion relations for crustal earthquakes in cascadia a simple application of the hybrid empirical approach is used to suggest appropriate regional ground motion relations the ground motions are obtained by multiplying california ground motion relations by a frequency dependent factor to account for regional differences in crustal amplifica tion the developed ground motion relations for cascadia earthquakes are in rea sonable agreement with recorded ground motions in the region the proposed rela tions are the first region specific ground motion relations to be developed for the cascadia region and they provide a useful alternative to california relations for use in seismic hazard analysis

weathering effects on the strength and deformational behaviour of crystalline rocks under uniaxial compression state uniaxial compression tests were performed on different categories of weathering of three lithological units malanjkhand granite nagpur basalt and delhi quartzite occurring in central and northern parts of india the deformational behaviour is studied in terms of variation in tangent modulus et50 and initial modulus ei due to weathering the power relationship between uniaxial compressive strength c and et50 shows strong correspondence for weathering sequence of common rock types this relationship has been established by regression analysis and significant correlation parameter coefficient of determination r2 0 87 for crystalline rocks it is shown that there is a systematic decrease in stiffness ratio that is ratio of tangent modulus and uniaxial compressive strength with increased weathering state comparison of et50 and ei values has shown that et50 decreases more gradually than ei and reduction is more drastic for ei values with an increased degree of weathering in all the three rock types the mode of failure has been found to be influenced by weathering extent in rocks a brief account is given of the intrinsic characteristics of fresh and weathered rocks and mineralogical changes produced by weathering investigated quantitatively correlation drawn between the petrographical and mechanical indices has shown that mechanical properties are apparently dependent on the intrinsic characteristics of weathered rocks

ams ultrasonic p wave velocity and rock strength analysis in quartzites devoid of mesoscopic foliations implications for rock mechanics studies abstract in this study anisotropy of magnetic susceptibility ams measurements are made on quartzites that do not contain visible foliations using ams data the magnetic foliation is recognized in the quartzites ultrasonic p wave velocity and point load strength which is a proxy for uniaxial compressive strength are determined in cores drilled parallel as well as perpendicular to the magnetic foliation ultrasonic p wave velocity is greater in the direction parallel to the foliation and lower perpendicular to the same conversely point load strength is lower in the direction parallel to the magnetic foliation and greater perpendicular to it ams data are compared with the anisotropy of p wave velocity as well as rock strength anisotropy it is noted that quartzites with a strong magnetic fabric also have a high p wave velocity anisotropy as well as rock strength anisotropy based on the results usefulness of ams in identification of principal testing directions for rock mechanics investigations in rocks devoid of mesoscopic foliations is discussed

predicted ground motions for great interface earthquakes in the cascadia subduction zone ground motions for earthquakes of moment magnitude m 7 5 9 0 on the cascadia subduction zone interface are simulated based on a stochastic finite fault model and used to estimate average response spectra for firm site conditions in vancouver victoria and seattle we also express the response spectra as ground motion prediction equations gmpes for cascadia events the simulations are calibrated by modeling the wealth of ground motion data from the m 8 1 tokachi oki earthquake sequence of japan adjustments to the calibrated model are made to consider average source attenuation and site parameters for the cascadia region we perform best estimate simulations for a preferred set of input parameters typical results suggest mean values of 5 damped pseudoacceleration in the range from about 100 to 200 cm sec2 at frequencies from 1 to 4 hz for firm ground conditions in vancouver victoria and seattle uncertainty in stress drop causes uncertainty in simulated response spectra of about 50 uncertainties in the attenuation model produce even larger uncertainties in response spectral amplitudes a factor of about 2 at 100 km becoming even larger at greater distances it is thus important to establish the regional attenuation model for ground motion simulations furthermore combining data from regions with different attenuation characteristics in particular japan and mexico into a global subduction zone database for development of global empirical gmpes may not be a sound practice time histories of acceleration for the stochastically simulated motions are provided for reference sites in vancouver victoria and seattle an alternative set of motions based on lightly modifying real recordings from the tokachi oki earthquake to match expected conditions for cascadia cities are also provided these alternative records have similar spectral content to the simulated motions but contain additional complexity and more realistic phasing the provision of alternative record sets allows users to conduct studies to determine the importance of these effects for structural response

evaluation of the impact of pyrite oxidation on rock characteristics and environment by laboratory tests pyrite is a common and abundant sulfidic mineral subject to oxidation the weathering characteristics of rock bearing pyrite sometimes impose serious influences on the surrounding environment as the oxidation of pyrite fes2 generates acid drainage that results in the acceleration of rock weathering and the discharge of heavy metals into the environment such an accelerated weathering of rocks can reduce its mechanical properties and therefore menace the stability of rock structures such as excavated slopes and tunnels the evolution of physical properties of rocks and the chemical composition of drainage were evaluated in this study by a weathering test using a double soxhlet extractor for 1 month in a laboratory setting three groups of biotite gneiss classified according to their pyrite content were used for the soxhlet extraction experiment group a with less than 0 1 wt of pyrite group b with about 3 3 wt of disseminated pyrite group c with about 5 65 wt of vein type pyrite the massive groups a and b had limited weathering on the surface however group c with the pyrite vein experienced weathering on the surface as well as along the pyrite vein the weathering type regulated by the occurrence of pyrite apparently controlled the mechanical properties of the rock samples and the chemistry of the drainage groups a and b showed no significant quick absorption ratio after the 1 month experiment however group c had about 10 increase in value the uniaxial compressive strength of the three groups decreased about 20 10 and 45 for groups a b and c respectively the mechanical properties of the samples and the chemical compositions of the drainage indicate that the oxidation of pyrite contained in the samples accelerated weathering resulting in deterioration of mechanical properties of the rocks and could result in the discharge of heavy metals and acid into the environment with the drainage

the relationship between magnetic anisotropy rock strength anisotropy and vein emplacement in gold bearing metabasalts of gadag south india abstract in this study the importance of rock strength and its anisotropy in controlling vein emplacement is evaluated by integrating anisotropy of magnetic susceptibility ams with rock mechanics data from massive visibly isotropic metabasalts of gadag region dharwar craton south india orientation of magnetic foliation mf is first recognized from ams subsequently rock mechanics tests viz ultrasonic p wave velocity vp uniaxial compressive strength ucs and point load strength is 50 are done in cores extracted parallel and perpendicular to mf vp is found to be higher in direction parallel to mf than perpendicular to it in contrast rock strength ucs and is 50 is greater in direction perpendicular to mf than parallel to it this proves that rocks from the gold mineralized belt of gadag have rock strength anisotropy orientation of mf in gadag region is nw se which is also the mean orientation of quartz veins previous studies indicate that emplacement of veins in the region took place during regional d3 nw se shortening based on the present study it is concluded that vein emplacement took place in nw se orientation because the rocks have strength anisotropy and are weaker in this direction orientation of mf which dilated to accommodate fluid flow in addition vein intensities are measured along three traverses and found to be variable it is argued that since mineralization is favoured when the system gets saturated with fluid variation in fluid flow could not have been responsible for variation in vein intensities in the study area since the rock strength of the different blocks investigated here is not uniform it is envisaged that variation in rock strength played an important role in controlling the vein intensities it is concluded that rock strength variation controlled strain partitioning and channelized fluid flow thus influencing vein emplacement and mineralization and formation of lodes

the effect of crustal structure on strong ground motion attenuation relations in eastern north america strong ground motion attenuation relations are usually described by smoothly decreasing functions of distance however consideration of wave propagation in the crust suggests that attenuation relations should be more complex such complexity may be present in strong ground motion data for eastern north american earthquakes which show amplitudes in the distance range of 60 to 150 km that lie above the trends at smaller and greater distances using a wavenumber integration method to compute green s functions and close in recordings of several earthquakes as empirical source functions we have generated synthetic seismograms that are in good agreement with regional and strong motion recordings of eastern north american earthquakes from these synthetic seismograms we have shown that the observed interval of relatively high amplitudes may be attributable to postcritically reflected s waves from the moho the presence and location of the interval of relatively high amplitudes is highly dependent on the crustal velocity structure and may therefore be expected to show regional variation however for any realistic structure model there will be a transition in the attenuation relation from an interval at shorter distances less than about 100 km that is dominated by direct waves to an interval at greater distances that is dominated by postcritically reflected waves the synthetic seismograms have response spectral velocities that match those of the recorded data and their m blg values are in good agreement with observed values

millimeter scale tsunami detected by a wide and dense observation array in the deep ocean fault modeling of an mw 6 0 interplate earthquake off sanriku ne japan

the slow earthquake spectrum in the japan trench illuminated by the s net seafloor observatories investigating slow earthquake activity in subduction zones provides insight into the slip behavior of megathrusts which can provide important clues about the rupture extent of future great earthquakes using the s net ocean bottom seismograph network along the japan trench we mapped a detailed distribution of tectonic tremors which coincided with very low frequency earthquakes and a slow slip event compiling these and other related observations including repeating earthquakes and earthquake swarms we found that the slow earthquake distribution is complementary to the tohoku oki earthquake rupture we used our observations to divide the megathrust in the japan trench into three along strike segments characterized by different slip behaviors we found that the rupture of the tohoku oki earthquake which nucleated in the central segment was terminated by the two adjacent segments

empirical attenuation of ground motion spectral amplitudes in southeastern canada and the northeastern united states a database of 1700 digital seismograms from 186 earthquakes of mag nitude mn 2 5 5 6 that occurred in southeastern canada and the northeastern united states from 1990 to 2003 was compiled maximum likelihood regression analysis of the database was performed to determine a model for the attenuation of fourier spectral amplitudes for the shear window for the vertical and horizontal component of motion for frequencies from 0 2 to 20 hz fourier amplitudes follow a hinged trilinear attenuation model fourier spectral amplitudes decay as r 1 3 where r is hypocentral distance within 70 km of the source there is a transition zone from 70 to 140 km as the direct waves are joined by strong postcritical reflections where the attenuation is described as r 0 2 spectral amplitudes actually increase with distance in this range for low frequencies beyond 140 km the attenuation is well described by r 0 5 corresponding to geometric spreading in two dimensions the associated model for the regional quality factor for frequencies greater than 1 hz can be ex pressed as q 893f 032 q can be better modeled over a wider frequency range 0 2 20 hz by a polynomial expression log q 3 052 0 393 log f 0 945 log f 2 0 327 log f 3 the polynomial expression accommodates the observation that q values are at a minimum about 1000 near 1 hz and rise at both lower and higher frequencies correction factors for the spectral amplitude model that describe the effects of focal depth on the amplitudes and their attenuation are developed using the subset of events with known focal depth the attenuation model is similar to that determined from an earlier study with more limited data atkinson and mereu 1992 but the enlarged database indicates more rapid near source amplitude decay and higher q the attenuation model is used to play back attenuation effects to determine the apparent source spectrum for each earthquake in the database and hence determine moment magnitude m and brune stress drop the events have moment magnitude in the range from 2 5 to 5 stress drop increases with moment magnitude for events of m 4 3 then appears to attain a relatively constant level in the range from 100 to 200 bars for the larger events as previously noted in atkinson 1993b the results of this study provide a useful framework for improving regional ground motion relations in eastern north america they further our understanding of attenuation in the region through analysis of an enlarged ground motion database in particular the inclusion of the three component broadband data gathered over the last decade allows extension of attenuation models to both horizontal and vertical components over a broad frequency range 0 2 20 hz

regional differences in ground motion amplitudes of small to moderate earthquakes across north america abstract we studied the response spectral amplitudes and peak ground acceleration pga of earthquakes with moment magnitude m from 3 0 to 6 0 to investigate regional differences in ground motion amplitudes across north america on a nonparametric basis for a common national earthquake hazards reduction program b c site condition e g shear wave velocity of 760 m s in the top 30 m of the soil column we use southern california as the reference region because it has the most plentiful data against which to compare other regions amplitudes of response spectra in eastern canada northeastern united states become increasingly larger than those in southern california as distance frequency and magnitude increases in the central united states ground motion amplitudes are larger than those in southern california at distances more than 100 km and lower at distances less than 100 km over all frequency and magnitude ranges studied amplitudes for crustal events in the pacific northwest british columbia are lower than those in southern california at frequencies 1 hz over all magnitude and distance ranges but have similar amplitudes below 1 hz amplitudes in northern california are similar to those in southern california at low frequencies below 3 3 hz but have lower amplitudes at high frequencies pga over all distances and magnitudes we conclude that regional amplitude differences are largely attributable to complex frequency dependent differences in regional attenuation for example the slope of apparent geometric spreading at distances less than 100 km is significantly steeper more negative in eastern canada northeastern united states than other regions and may be frequency dependent the regional attributes of the attenuation comparisons appear to be the same for both vertical and horizontal components at least for b c site conditions online material figures of region dependent ground motion amplitudes apparent geometric spreading statistical tests of the ground motions and figures and table of ratios of ground motions relative to those from southern california

in situ gamma ray spectrometric study of weathered volcanic rocks in hong kong in situ gamma ray spectrometry grs measurements were conducted at 35 sites in hong kong where volcanic rocks with varying extent of weathering were exposed elemental analyses using x ray fluorescence spectrometry and inductively coupled plasma mass spectrometry were carried out on samples collected from these 35 plus 22 other locations to assess the feasibility of using the grs method to quantify the extent of weathering the parker weathering index varying within a range of 0 0 0 8 for the samples studied was used as a geochemically based reference scheme for correlating the gamma ray spectrometric results with the extent of weathering for the former 35 sites the concentrations of the three major radioelements k u and th determined by in situ grs were compared to laboratory determined values from the samples the study reveals that no significant change occurs to the contents of the three radioelements during the initial state of weathering but once the rocks become highly weathered further progression of weathering is accompanied by a systematic removal of k and an increased dispersion of u and th the results show that k content which is indicative of the extent of weathering can be retrieved reliably with the gamma ray spectrometry technique the study has given support to the potential use of the downhole spectral gamma method for evaluation of weathering grade and the detection of subsurface clay rich levels copyright 2002 john wiley sons ltd

the shape of ground motion attenuation curves in southeastern canada the shape of the attenuation curve of the fourier spectrum of acceleration is established for southeastern canada from empirical data the dataset is comprised of 1200 digital vertical component seismograms from 100 earthquakes recorded on 30 stations of the eastern canada telemetered network the distance range of the observations is 10 to 1700 km focal depths are from 5 to 30 km results indicate that the attenuation curve has three distinct sections at distances less than 70 km corresponding to attenuation of the direct wave amplitudes decay slightly more rapidly than 1 r r 1 1 between 70 and 130 km where the direct wave is joined by sms spectral amplitudes are approximately constant beyond 130 km corresponding to the lg phase amplitudes decay at a rate that is consistent with r 0 5 and q 670 f 0 33 the findings support the hypothesis of burger et al 1987 that postcritical reflections from the moho discontinuity play an important role in determining the shape of the attenuation curve however the influence of sms is subtle allowing the shape to be approximated by simple functional forms for example the commonly assumed bilinear form r 1 r 0 5 with frequency dependent q fits well if the transition from direct wave to lg spreading is placed at approximately 60 km a linear form r 1 over all distances with constant q 2000 also provides a satisfactory fit overall we find little evidence for the dependence of attenuation on focal depth or tectonic province

a revised magnitude recurrence relation for shallow crustal earthquakes in southwestern british columbia considering the relationships between moment magnitude and regional magnitudes an important component of seismic hazard analysis is the magnitude recurrence relation which provides the cumulative rate of occurrence of earthquakes within a seismic source zone as a function of magnitude in the national seismic hazard maps developed for the 2005 national building code of canada the magnitude recurrence relation for the cascade mountains zone of southwestern british columbia casr the seismic zone in which vancouver and victoria are located is based mainly on earthquakes measured on the local scale m l richter scale but other scales including body wave magnitude m b coda duration magnitude m c and moment magnitude m have been used for some of the events the mixture of magnitude types is a potential source of bias in the relations by using data from recently calculated regional moment tensor solutions a local magnitude moment magnitude relationship is developed for magnitudes of 2 9 m l 6 0 in the casr zone this relation along with relations from other sources for m b and m c and specific moment magnitude values where available are used to develop a homogeneous moment magnitude catalog for use in the formulation of a new casr zone magnitude recurrence relation the use of a homogeneous moment magnitude scale produces a significant change in the shape of the magnitude recurrence curve in the casr zone perhaps more importantly the use of a homogeneous catalog reduces the uncertainty in the recurrence rates of moderate to large earthquakes in casr by nearly an order of magnitude we conclude that the use of a homogeneous magnitude scale is critical to producing unbiased magnitude recurrence relations

earthquake early warning shakealert in the pacific northwest we evaluate the performance of earthquake early warning algorithm elarms 2 earthquake alarm system v 2 in the pacific northwest real time and prerecorded seismic data from oregon california and washington in the united states and british columbia in canada are used the earthquakes tested range up to moment magnitude 7 2 the limit for which the elarms 2 magnitude method is accurate elarms 2 reliably detects catalog magnitude 3 and larger earthquakes within the network but the cut off magnitude for accurate event recognition is higher for events offshore and on the edges of the network we have made several adjustments that make the elarms 2 algorithm less likely to falsely report multiple alerts for earthquakes replaying of past earthquakes shows that the new settings improve the algorithm s behavior for edge cases while not degrading previously well constrained solutions within the dense part of the network we expect few false alerts none that would predict significant shaking anywhere in our region even though elarms 2 assumes a fixed earthquake depth the epicenter and magnitude estimates are accurate enough to provide good predictions of shaking intensities online material tables listing parameters of 31 calibration earthquakes elarms 2 real time detections and comparison of elarms 2 performance for calibration events before and after adjusting configuration

observations on regional variability in ground motion amplitudes for small to moderate earthquakes in north america abstract the regional variability in earthquake ground motion amplitudes for a given magnitude and distance in western north american environments was examined using shakemap data from small to moderate events the abundance of data for small to moderate events in california allows average ground motion levels as a function of magnitude and distance to be resolved with a high level of confidence ground motion amplitudes in northern california are lower on average than those for southern california for events of the same magnitude at distances in the range from 120 to 250 km over all frequencies the observed regional variations could be indicative of regional differences in attenuation effects or site effects an unexpected result of the study is the finding that ground motions for events of m m m m

non destructive testing for the assessment of granite decay in heritage structures compared to quarry stone several types of granite found in two architectural heritage monuments were assessed with two non destructive portable techniques schmidt hammer rebound and ultrasound velocity vp similar assessments were conducted on the rock from which the granite was originally quarried for comparison the results obtained which revealed the existence of a direct correlation constitute a useful indication of decay particularly if the approximate dates of construction are known and conversely if they are not such stone assessments may provide a rough estimate of when the structure was built both of these convenient portable and non destructive techniques may be used as reliable indicators of the degree of stone decay

attenuation and source parameters of earthquakes in the cascadia region digital ground motion data recorded by the western canada telemetered network wctn are used to examine the attenuation and source parameters of earthquakes in the cascadia region of southwestern british columbia and northwestern washington the data base is comprised of over 1000 vertical component fourier spectra from earthquakes of magnitude 3 to 7 at distances from 10 to 500 km regression analyses determine the shape and coefficients of the regional attenuation curve and source spectra for 68 earthquakes seismic moment and stress drop are inferred from the amplitudes of the source spectra shallow h 10 km earthquakes have an attenuation curve with a complex shape exhibiting significant flattening no apparent geometric spreading in the distance range from 75 to 230 km this shape is probably a result of strong reflected phases from mid crustal discontinuities and the subducting slab events within the subducting slab and the lower crust exhibit a simple r 1 attenuation curve the anelastic attenuation coefficient for the region as a whole is given by q 380 f 0 39 the duration of motion for each wctn record is determined as the value that yields the observed relationship between time domain and spectral domain amplitudes according to random process theory these durations are approximately constant within 50 km of the source then increase with distance as 0 07 r the high frequency ground motions from cascadia earthquakes are relatively weak cascadia source spectra are characterized by an average brune stress drop of about 30 bars this is significantly lower than the average california stress drop of 70 to 100 bars and dramatically lower than the average eastern stress drop of 150 to 200 bars it is concluded that there are significant regional variations in source parameters hazard estimates for the cascadia region based on california groundmotion relations may be overly conservative

the effect of weathering on pore geometry and compressive strength of selected rock types from turkey weathering processes cause important changes in rock porosity besides porosity distribution of pore sizes is significant for the identification of changes due to rock weathering and its effects on fabric the formation of secondary porosity in different types of rock taken from different parts of turkey was examined and the results are presented in this paper the aim of this study was to observe changes in porosity due to weathering effective porosity mercury intrusion porosimetry and optical and scanning electron microscopy were used to evaluate the changes in pore geometry of the rocks additionally the dry density water absorption and uniaxial compressive strength of the rocks at different weathering stages were determined analysis of experimental data showed that microstructure of the rocks in relation to weathering is the main feature which controls their physical and mechanical properties the study revealed that fabric characteristics particularly the pore and fracture geometry are very important characteristics for assessment of the behaviour of weathered rock

global comparisons of earthquake source spectra a key question in earthquake seismology is whether earthquake sources in different tectonic regions are functionally equivalent in terms of radiated ground motion this article compares the apparent earthquake source radiation for six different regions japan mexico turkey california british columbia b c western canada and eastern north america ena the source path and site effects were consistently separated to the extent possible to allow interregional comparisons of apparent source radiation large fourier spectra databases were created for both horizontal and vertical components for earthquakes with magnitude between 2 5 and 7 5 regional parameters characterizing source path and site properties including crustal and near surface site amplifications were investigated to isolate apparent source spectra based on the vertical component spectra at a reference distance of 1 km a new magnitude scale m 1 was defined from the spectral level at 1 hz the magnitude scale m 1 is a natural complement to existing magnitude scales that measure the low frequency and high frequency spectral amplitudes moment magnitude m and high frequency m hf respectively in all regions the apparent source spectra for small to moderate earthquakes m 6 show good agreement with the single corner brune 1970 1971 point source model 2 spectrum suggesting a stress parameter of about 100 bars 10 mpa a two corner source model better matches the spectra for large magnitude earthquakes m 6 especially at intermediate frequencies for small to moderate events the two source models are nearly equal apparent source spectra from small to moderate earthquakes e g m 1 3 5 6 5 suggest a general similarity between the different tectonic regions studied although minor discrepancies appear in some cases there are no noticeable regional characteristics no evident depth effects were found on the apparent source spectra manuscript received 1 april 2001

estimating absolute site effects the authors use previously determined direct wave attenuation functions as well as stable coda derived source excitation spectra to isolate the absolute s wave site effect for the horizontal and vertical components of weak ground motion they used selected stations in the seismic network of the eastern alps and find the following 1 all hard rock sites exhibited deamplification phenomena due to absorption at frequencies ranging between 0 5 and 12 hz the available bandwidth on both the horizontal and vertical components 2 hard rock site transfer functions showed large variability at high frequency 3 vertical motion site transfer functions show strong frequency dependence and 4 h v spectral ratios do not reproduce the characteristics of the true horizontal site transfer functions 5 traditional relative site terms obtained by using reference rock sites can be misleading in inferring the behaviors of true site transfer functions since most rock sites have non flat responses due to shallow heterogeneities resulting from varying degrees of weathering they also use their stable source spectra to estimate total radiated seismic energy and compare against previous results they find that the earthquakes in this region exhibit non constant dynamic stress drop scaling which gives further support for a fundamental difference in rupture dynamics between small and large earthquakes to correct the vertical and horizontal s wave spectra for attenuation they used detailed regional attenuation functions derived by malagnini et al 2002 who determined frequency dependent geometrical spreading and q for the region these corrections account for the gross path effects i e all distance dependent effects although the source and site effects are still present in the distance corrected spectra the main goal of this study is to isolate the absolute site effect as a function of frequency by removing the source spectrum moment rate spectrum from the distance corrected s wave spectra typically removing the s wave source spectrum is difficult because of inadequate corrections for the source radiation pattern directivity and random interference in addition to complexities near the source 2 d and 3 d structure beneath the recording site will result in an azimuth dependent site effect since the direct wave only samples a narrow range in take off and back azimuth angles multi station averaging is needed to minimize the inherent scatter to minimize these complicating effects they apply the coda methodology outlined by mayeda et al 2003 to obtain stable moment rate spectra this methodology provides source amplitude and derived source spectra that are a factor of 3 to 4 times more stable than those derived from direct waves since the coda is commonly thought of as scattered energy that samples all ray parameters and back azimuths it is not very sensitive to the source radiation pattern and 3 d structure this property makes it an excellent choice for use in obtaining average properties of the source site and path effects in a region due to the characteristics of the techniques used in this study all the inverted quantities are azimuthally averaged since the aximuthal information is lost in the processing

p and s velocity structure in the groningen gas reservoir from noise interferometry noise interferometry has proven to be a powerful tool to image seismic structure in this study we used data from 10 geophones located in a borehole at 3 km depth within the groningen gas reservoir in the netherlands the continuous data cross correlations show that noise predominantly comes in from above the observed daily and weekly variations further indicate that the noise has an anthropogenic origin the direct p wave emerges from the stacked vertical component cross correlations with frequencies up to 80 hz and the direct s wave is retrieved from the horizontal components with frequencies up to 50 hz the measured inter geophone travel times were used to retrieve the p and s velocity structure along the borehole and a good agreement was found with well log data in addition from the s wave polarizations we determined azimuthal anisotropy with a fast direction of n65 w 18 and an estimated magnitude of 4 2 the fast polarization direction corresponds to the present direction of maximum horizontal stress measured at nearby boreholes but is also similar to the estimated paleostress direction

estimation of uniaxial compressive strength of rock materials by index tests using regression analysis and fuzzy inference system abstract this paper presents a comparative evaluation of efficacies of different index tests and analysis techniques i e regression analyses and fuzzy inference system in predicting uniaxial compressive strength ucs of granite schist and sandstone ucs and indices such as block punch index point load strength schmidt rebound hardness ultrasonic p wave velocity and physical properties effective porosity and density were determined for the concerned rocks from simple regression analyses it was apparent that for granite and sandstone performances of all six indices are reasonably good in predicting ucs in case of granite block punch index and point load strength are the best indices whereas effective porosity point load strength and schmidt rebound hardness are the most efficient indices for sandstone in case of schist however ultrasonic p wave velocity does not seem to be a competent index unlike other indices where point load strength proves to be the best one from the critical analysis of the tests results it was demonstrated and subsequently concluded that index test results of different rock types with different geology should not be clubbed together for statistical correlation with any rock mechanical parameter like ucs both multiple regression analyses and the fuzzy inference system exhibited better predictive performances for ucs than simple regression analyses in addition to the coefficient of correlation the variance account for vaf and the root mean square error rmse were also calculated to check the predictive performances of these two models and it was found that the predictive performances of both models are comparable however one should be cautious while employing multiple regression analysis in predicting ucs as there is always a chance of cumulating plausible errors that might have remained within individual index test results on the other hand fuzzy inference system seems to be an efficient tool in predicting ucs of rock materials from indices because of its efficacy in handling uncertainties in the test results with transparency

an empirical study of earthquake source spectra for california earthquakes we generalize source path and site effects for california earthquakes as functions of magnitude and distance based on regression analysis of 1000 fourier acceleration spectra from 43 california earthquakes in the moment magnitude range from 4 4 to 7 4 recorded at rupture distances from 1 to 200 km empirically derived source spectra for california earthquakes are generally inconsistent with the spectral shape implied by a brune omega squared point source model this is manifested by magnitude and frequency dependence of the brune model parameters for ex ample the brune stress parameter that best matches the data at high frequencies decreases from a value of about 120 bars at m5 5 to a value near 50 bars at m7 5 at frequencies below 1 hz though source spectra have much lower spectral ampli tudes than predicted by the brune point source model for these values of stress this discrepancy grows with increasing magnitude finite fault simulations indicate that this is a consequence of the breakdown of the validity of the point source approxi mation for large ruptures a stochastic finite fault model in which the fault is dis cretized as a number of subfaults each of which is represented by a brune omega squared point source correctly matches the observed spectral shapes and amplitudes the spectral decay parameter kappa representing average near surface attenuation of high frequency motion at rock sites increases with increasing magnitude from values near 0 035 sec at m5 5 to 0 050 sec at m7 5 magnitude dependence of kappa may be interpreted as evidence of nonlinearity for typical california sites subjected to strong ground motion comparisons of our empirical source spectra for california to corresponding spec tra for eastern north america suggest that the spectral amplitudes are similar in the two regions for low frequency motions f 2 hz for m5 5 f 0 5 hz for m7 5 for equivalent crustal conditions the eastern events appear to have enhanced high frequency near source amplitudes relative to the california events this is particularly pronounced for large magnitude earthquakes

site effect evaluation using spectral ratios with only one station the spectral ratio technique is a common useful way to estimate empirical transfer function to evaluate site effects in regions of moderate to high seismicity the purpose of this paper is to show that it is possible to estimate empirical transfer function using spectral ratios between horizontal and vertical components of motion without a reference station the technique originally proposed by nakamura to analyze rayleigh waves in the microtremor records is presented briefly and it is discussed why it may be applicable to study the intense s wave part in earthquake records results are presented for three different cities in mexico oaxaca oax acapulco gro and mexico city these cities are very different by their geological and tectonic contexts and also by the very different epicentral distances to the main seismogenic zones affecting each city each time we compare the results of nakamura s technique with standard spectral ratios in all three cases the results are very encouraging we conclude that if site effects are caused by simple geology a first estimate of dominant period and local amplification level can be obtained using records of only one station

deep ocean sound speed characteristics passively derived from the ambient acoustic noise field the propagation of acoustic waves in the ocean strongly depends on the temperature lowfrequency acoustic waves can penetrate the ocean down to depths where few in situ measurements are available it is therefore attractive to obtain a measure of the deep ocean temperature from acoustic waves the latter is especially true if the ambient acoustic noise field can be used instead of deterministic transient signals in this study the acoustic velocity and hence the temperature is derived in an interferometric approach from hydrophone array recordings the arrays were separated by over 125 km near ascension island in the atlantic ocean at a depth of 850 m furthermore the dispersive characteristics of the deep ocean sound channel are resolved based on the retrieved lag times for different modes in addition it is shown how the resolution of the interferometric approach can be increased by cross correlating array beams rather than recordings from single sensor pairs the observed acoustic lag times between the arrays corresponds well to modelled values based on full wave modelling through best known oceanic models

continuous gps array and present day crustal deformation of japan a gps array with about 1 000 permanent stations is under operation in japan the gps array revealed coseismic deformations associated with large earthquakes and ongoing secular deformation in the japanese islands based on daily coordinate data of the gps stations strain rate distribution is estimated most regions with a large strain rate are related to plate boundaries and active volcanoes in addition the niigata kobe tectonic zone nktz is recognized as a region of large strain rate along the japan sea coast and in the northern chubu and kinki districts this newly found tectonic zone may be related to a hypothetical boundary between the eurasian or amurian and the okhotsk or north america plates precise observation of crustal deformation provides important boundary conditions on numerical modeling of earthquakes and other crustal activities appropriate computation methods of continuous deformation field are directly applicable to data assimilation for such numerical simulations

attenuation and apparent source characteristics in the northern indian oceanic crust surrounding sri lanka a data analysis of 171 broadband vertical component records of 62 shallow crustal distant events in the northern indian ocean region was undertaken to investigate the far source geometric attenuation rate high frequency cutoff filter parameter kappa and apparent source characteristics event magnitude varied from 4 0 to 5 9 in the short period body wave magnitude m b scale and hypocentral distance ranged between 2 3 260 km and 14 1 1578 km for the dataset the far source geometric attenuation rate was estimated by fitting data to a predefined attenuation equation at a frequency range of 0 5 8 5 hz using the multiple linear regression method a secondary regression in the frequency domain on constants resulting from the main first regression was performed to find kappa and the second hinge point of the trilinear geometric attenuation function source characteristics stress drop corner frequency and moment magnitude of selected events were determined using the brune 1970 1971 model the average far source geometric attenuation rate was determined to be r 0 5 r is hypocentral distance for the selected frequency range but at low frequencies below about 2 hz slightly lower rates than the average were observed kappa was found to be 0 041 0 009 s the second hinge point of the geometric attenuation function was estimated to be 120 30 km and the complete form of the function after considering compliancy with actual records was collated as graphic 1 average static stress drops were found to be 9 5 and 16 0 mpa for the m b 4 5 and 5 6 magnitude bands respectively corner frequencies approximately fell within 1 0 7 0 hz for the dataset derived attenuation parameters were also validated using a ground motion comparison between recorded and stochastically simulated events online material tables of regression parameters estimated source parameters and stochastic simulation parameters and a figure comparing the ground motion for simulated and recorded events 1 embed inline graphic 1 gif

effects of seismicity models and new ground motion prediction equations on seismic hazard assessment for four canadian cities seismicityratesandground motionpredictionequations gmpes arethe key uncertainties in probabilistic seismic hazard analysis psha we explore the impact of new findings and knowledge from seismological and ground motion studies on seismic hazard assessment for eastern and western canada updated information includes the reevaluation of seismicity rates and their interpretation in terms of seismic source zones and the use of new gmpes we refer to our model as an interim updated seismic hazard model as it does not treat all uncertainties comprehensively rather we address the impact of key uncertainties based on our updated interim seismic hazard model uniform hazard spectra uhs at four major cities across canada are obtained and compared with uhs in the current seismic hazard maps of canada 2005 2010 whicharebasedona1995seismichazardmodeldevelopedbythegeologicalsurveyof canada sensitivity analysis highlights the significant impact of seismicity smoothing in low to moderate seismic regions eastern canada while gmpes are important for all regions moreover our interim updated seismic hazard model can readily produce seismic hazard curves as well as seismic hazard deaggregation results for various site conditionsandformultipleprobabilitylevels thiscapabilityisessentialforcarryingout advanced earthquake engineering analyses

the influence of weathering on the geotechnical properties and slope angles of mudstone in the mineoka earth slide area japan three active earth slide slopes of tertiary mudstone were investigated slope 1 has an angle of 17 4 slope 2 of 12 9 and slope 3 of 11 6 infinite slope analysis indicated that the instability of these three slopes can be well explained by using the residual strength parameters of earth slide soils near the sliding surface in conjunction with the highest ground water table the residual angle of shearing resistance o r plays an important role in the determination of slope angle because it differs greatly among slopes mineralogical studies and x ray diffraction analyses were performed for the clay minerals included in the slope material the results showed that illite and chlorite were found in slope 1 and also in slopes 2 and 3 together with interstratified illite montmorillonite and montmorillonite the degree of weathering is progressive in order of slopes 1 2 and 3 the alteration of clay minerals by weathering causes the reduction in o r values i e 19 4 in slope 1 steep less weathered and 12 1 9 2 in slopes 2 and 3 gentle much more weathered this result indicates that the degree of weathering has a great influence on the value of o r which in turn determines the slope angle

three dimensional crustal s wave velocity structure in japan using microseismic data recorded by hi net tiltmeters 1 we developed a three step method for three dimensional 3 d s wave velocity tomography by fitting synthetic cross spectra to the observed ones of ambient seismic noise we applied this method to the recording of hi net tiltmeters in japan at 679 stations from june 2004 to december 2004 first we calculated normalized cross spectra between radial components and those between transverse components for every pair of stations the first step is local 1 d s wave velocity inversion for each station assuming small lateral heterogeneity under a 100 km circle of a station we measured the dispersion curves of fundamental rayleigh waves fundamental love waves and first overtone of love waves by fitting the synthetic cross spectra to the observed ones between pairs of stations within the circle we inverted the measured dispersion curves for obtaining a 1 d s wave velocity model the second step is the inversion of the observed cross spectra for obtaining path averaged 1 d s wave velocity structure the third step is the inversion of the resultant path averaged structures for obtaining 3 d s wave velocity structure 0 1 0 1 1 km grid from the surface to a depth of 50 km using ray approximation the resultant s wave velocity structures show clear low velocity anomalies along tectonic lines from the surface to a depth of 20 km in particular along the hidaka mountain range we observed s wave perturbation more extreme than 20 they also show low velocity anomalies under volcanoes in kyusyu and tohoku in the southwestern part of shikoku our results show a clear low velocity anomaly corresponding to an accretional belt shimanto belt below 20 km we observe a low velocity anomaly in the center of japan which suggests a thick crust citation nishida k h kawakatsu and k obara 2008 three dimensional crustal s wave velocity structure in japan using microseismic data recorded by hi net tiltmeters j geophys res 113 b10302 doi 10 1029 2007jb005395

ground motion amplification at rock sites across canada as determined from the horizontal to vertical component ratio we determine the frequency dependent amplification inherent in hard rock sites across canada under the assumption that it can be estimated from the ratio of the horizontal to vertical h v components of ground motion the use of h v as an estimate of amplification was originally proposed by nakamura 1989 for microtremors and then generalized to earthquake ground motions by lermo and chavez garcia 1993 the h v method was applied to a fourier spectra database compiled from 424 earthquakes of magnitude greater than or equal to 2 recorded on 32 three component stations of the canadian national seismograph network cnsn all sited on rock shear wave velocity 1500 m sec in each case we analyzed the s wave portion of the seismograms including the direct s and other strong s phases such as lg the average amplification h v for rock sites does not vary significantly across the country it is weakly frequency dependent increasing from a factor near unity at 0 5 hz to a maximum in the range from 1 2 to 1 6 at 10 hz this amplification is consistent with what would be expected from a gradual decrease in shear wave velocity as the seismic waves approach the surface due to factors such as near surface weathering the interpretation of the h v ratio as a measure of site response is consistent with the general geological conditions of the recording sites in particular the 5 hz h v ratio can be correlated with local geological conditions the central canada sites have the lowest estimated site amplification this is consistent with competent hard rock site conditions with high near surface shear wave velocities there are two stations that show anomalous h v ratios that suggest significant local site effects these are edm near edmonton which may be influenced by topographic amplification and a61 a station in the charlevoix seismic zone

assessment of ground motion models for use in the british columbia north coast region canada abstract the 28 october 2012 m w 7 8 haida gwaii earthquake was the second largest earthquake instrumentally recorded in canada s territory and was strongly felt across the british columbia north coast bcnc region data from the haida gwaii sequence and other events in the region are compiled for 56 earthquakes between moment magnitude m w 4 6 and 7 8 that occurred between 1996 and 2014 pseudospectral accelerations psa at 5 damping are calculated and compared against several modern ground motion models gmms using different binning criteria e g distance magnitude mechanism source to site azimuth and event chronology overall no single model is found to be appropriate for the bcnc region with gmms generally overestimating recorded near source i e earthquake motions recorded prior to and including the 2012 m w 7 8 earthquake were generally more comparable with some gmms at longer spectral periods but still possessed significant biases based on residual analyses additionally earthquakes with normal mechanisms gave less short to mid period shaking relative to strike and reverse slip events online materials summary of the candidate ground motion prediction equations indicating their distance metrics and conditions of use

engineering properties of fresh and decomposed igneous rocks from hong kong abstract the influence of degree of decomposition on the strength and elasticity of fresh to highly decomposed igneous rocks in hong kong is described and summarized assessments of degree of decomposition by rock grade rock quality designation apparent porosity ultra sonic velocity and point load index are discussed from the point of view of estimating rock behaviour for engineering purposes a sufficiently precise measure of decomposition could be based on the point load index and a sufficiently reliable estimate of elastic modulus could be calculated from the ultra sonic velocity

earthquake magnitude measurements for puerto rico reliable determination of earthquake magnitude is a fundamental building block of seismic hazard assessment the seismicity catalog for puerto rico is dominated by small earthquakes m 5 mostly m d a local magnitude based on duration and m b body wave magnitude there is considerable uncertainty over the interpretation of m d to reduce this uncertainty we evaluate moment magnitude m and m 1 1 hz magnitude for events within the catalog and develop relationships between these and other magnitude measures the available seismographic data are mostly short period records because broadband instruments in puerto rico have been installed only recently a difficulty with the calculation of moment magnitude is that short period data do not generally extend to sufficiently low frequencies to reliably obtain the displacement spectrum at low frequencies moment magnitudes for small earthquakes in puerto rico are thus estimated from a single broadband station and subject to much uncertainty to get around this difficulty we used m 1 which closely tracks moment magnitude for small to moderate events chen and atkinson 2002 m 1 is obtained from the spectral amplitude at 1 hz and is defined such that it will equal moment magnitude for earthquakes following a brune point source model unlike moment magnitude m 1 can be determined from short period seismograms our values of m and m 1 are in close agreement with each other for small to moderate earthquakes there is a systematic difference between m 1 or m and catalog magnitudes m b or m d with the catalog magnitude exceeding moment magnitude by about 0 4 units on average it is recommended that m 1 be used as a regional magnitude scale for earthquakes in puerto rico and as an estimate of m for events of m 5 online material list of earthquakes in puerto rico from 1993 through 2002