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NGA ground motion model for the geometric mean horizontal component of PGA, PGV, PGD, and 5%-damped linear elastic response spectra for periods ranging from 0.01 to 10 s, Earthquake Spectra
, 2008
"... We present a new empirical ground motion model for PGA, PGV, PGD and 5 % damped linear elastic response spectra for periods ranging from 0.01–10 s. The model was developed as part of the PEER Next Generation Attenuation (NGA) project. We used a subset of the PEER NGA database for which we excluded r ..."
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Cited by 102 (4 self)
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We present a new empirical ground motion model for PGA, PGV, PGD and 5 % damped linear elastic response spectra for periods ranging from 0.01–10 s. The model was developed as part of the PEER Next Generation Attenuation (NGA) project. We used a subset of the PEER NGA database for which we excluded recordings and earthquakes that were believed to be inappropriate for estimating free-field ground motions from shallow earthquake mainshocks in active tectonic regimes. We developed relations for both the median and standard deviation of the geometric mean horizontal component of ground motion that we consider to be valid for magnitudes ranging from 4.0 up to 7.5–8.5 (depending on fault mechanism) and distances ranging from 0–200 km. The model explicitly includes the effects of magnitude saturation, magnitude-dependent attenuation, style of faulting, rupture depth, hanging-wall geometry, linear and nonlinear site response, 3-D basin response, and inter-event and intra-event variability. Soil nonlinearity causes the intra-event standard deviation to depend on the amplitude of PGA on reference rock rather than on magnitude, which leads to a decrease in aleatory uncertainty at high levels of ground shaking for sites located on soil. DOI: 10.1193/1.2857546
Earthquake ground-motion prediction equations for Eastern North America
- Bulletin of the Seismological Society of America
, 2006
"... In our recent ground-motion article (Atkinson and Boore, 2006), equation (6) describes an adjustment factor that can be applied to our ground-motion prediction equa-tions to accommodate a factor of 2 difference in stress drop from our preferred value of 140 bars. The text following this equation des ..."
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Cited by 53 (10 self)
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In our recent ground-motion article (Atkinson and Boore, 2006), equation (6) describes an adjustment factor that can be applied to our ground-motion prediction equa-tions to accommodate a factor of 2 difference in stress drop from our preferred value of 140 bars. The text following this equation describes how the factor may be scaled to accom-modate other stress parameter values. This allows the user to adjust the equations for any arbitrary stress parameter of their choosing (within the tested range from 35 to 560 bars). The descriptive text of how the scaling should work is in error. The scale factor that multiplies log SF2 should be as follows: Scale factor log(stress/140) / log (2). Thus the scale factor by which we multiply log SF2 (where log SF2 is as given in equation 6) has a value of 0 for stress 140, a value of 1 for stress 280, and a value of1 for stress 70. For the example given in the text of a desired stress of 210 bars, the factor is log(210/140)/log(2) 0.58. In this case, we would add 0.58 log SF2 to the predicted log PSA values.
Stochastic modeling of California ground motions
"... Abstract Ground-motion relations are developed for California using a stochastic simulation method that exploits the equivalence between finite-fault models and a two-corner point-source model of the earthquake spectrum. First, stochastic simu-lations are generated for finite-fault ruptures, in orde ..."
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Cited by 51 (11 self)
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Abstract Ground-motion relations are developed for California using a stochastic simulation method that exploits the equivalence between finite-fault models and a two-corner point-source model of the earthquake spectrum. First, stochastic simu-lations are generated for finite-fault ruptures, in order to define the average shape and amplitude level of the radiated spectrum at near-source distances as a function of earthquake size. The length and width of the fault plane are defined based on the moment magnitude of the earthquake and modeled with an array of subfaults. The radiation from each subfault is modeled as a Brune point source using the stochastic model approach; the subfault spectrum has a single-corner frequency. An earthquake rupture initiates at a randomly chosen subfault (hypocenter), and propagates in all directions along the fault plane. A subfault is triggered when rupture propagation reaches its center. Simulations are generated for an observation point by summing the subfault time series, appropriately lagged in time. Fourier spectra are computed for records simulated at many azimuths, placed at equidistant observation points around the fault. The mean Fourier spectrum for each magnitude, at a reference near-
Three-dimensional simulations of ground motions in the San Bernardino Valley, California, for hypothetical earthquakes on the San Andreas fault
, 1993
"... Abstract We used the 3D finite-difference method to model observed seismo-grams of two earthquakes (ML 4.9 and 3.5) in the Seattle region and to simulate ground motions for hypothetical M 6.5 and M 5.0 earthquakes on the Seattle fault, for periods greater than 2 sec. A 3D velocity model of the Seatt ..."
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Cited by 50 (3 self)
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Abstract We used the 3D finite-difference method to model observed seismo-grams of two earthquakes (ML 4.9 and 3.5) in the Seattle region and to simulate ground motions for hypothetical M 6.5 and M 5.0 earthquakes on the Seattle fault, for periods greater than 2 sec. A 3D velocity model of the Seattle Basin was con-structed from studies that analyzed seismic-reflection surveys, borehole logs, and gravity and aeromagnetic data. The observations and the simulations highlight the importance of the Seattle Basin on long-period ground motions. For earthquakes occurring just south of the basin, the edge of the basin and the variation of the thickness of the Quaternary deposits in the basin produce much larger surface waves than expected from flat-layered models. The data consist of seismograms recorded by instruments deployed in Seattle by the USGS and the University of Washington (UW). The 3D simulation reproduces the peak amplitude and duration of most of the seismograms of the June 1997 Bremerton event (ML 4.9) recorded in Seattle. We found the focal mechanism for this event that best fits the observed seismograms in Seattle by combining Green’s functions determined from the 3D simulations for the six fundamental moment couples. The February 1997 event (ML 3.5) to the south of the Seattle Basin exhibits a large surface-wave arrival at UW whose amplitude is matched by the synthetics in our 3D velocity model, for a source depth of 9 km. The M 6.5 simulations incorporated a fractal slip distribution on the fault plane. These simulations produced the largest ground motions in an area that includes downtown Seattle. This is mainly caused by rupture directed up dip toward downtown, radiation pattern of the source, and the turning of S waves by the velocity gradient in the Seattle basin. Another area of high ground motion is located about 13 km north of the fault and is caused by an increase in the amplitude of higher-mode Rayleigh waves caused by the thinning of the Quaternary deposits.
2002c), Aftershock zone scaling
- Bull. Seismol. Soc. Am
"... Abstract We investigate the distribution of aftershock zones for large earthquakes (scalar seismic moment M 1019.5 N m, moment magnitude, m 7). Mainshocks are selected from the Harvard centroid moment tensor catalog, and aftershocks are selected from the Preliminary Determination of Epicenters (NEIC ..."
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Cited by 39 (14 self)
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Abstract We investigate the distribution of aftershock zones for large earthquakes (scalar seismic moment M 1019.5 N m, moment magnitude, m 7). Mainshocks are selected from the Harvard centroid moment tensor catalog, and aftershocks are selected from the Preliminary Determination of Epicenters (NEIC) catalog. The af-tershock epicenter maps are approximated by a two-dimensional Gaussian distribu-tion; the major ellipse axis is taken as a quantitative measure of the mainshock focal zone size. The dependence of zone length, l, on earthquake size is studied for three representative focal mechanisms: thrust, normal, and strike slip. Although the num-bers of mainshocks available for analysis are limited (maximum a few tens of events in each case), all earthquakes show the same scaling (M l3). No observable scaling break or saturation occurs for the largest earthquakes (M 1021 N m, m 8). There-fore, it seems that earthquake geometrical focal zone parameters are self-similar.
Stochastic finite-fault modeling based on a dynamic corner frequency
- Bulletin of the Seismological Society of America
, 2005
"... Abstract In finite-fault modeling of earthquake ground motions, a large fault is divided into N subfaults, where each subfault is considered as a small point source. The ground motions contributed by each subfault can be calculated by the stochastic point-source method and then summed at the observa ..."
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Cited by 35 (6 self)
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Abstract In finite-fault modeling of earthquake ground motions, a large fault is divided into N subfaults, where each subfault is considered as a small point source. The ground motions contributed by each subfault can be calculated by the stochastic point-source method and then summed at the observation point, with a proper time delay, to obtain the ground motion from the entire fault. A new variation of this approach is introduced based on a “dynamic corner frequency. ” In this model, the corner frequency is a function of time, and the rupture history controls the frequency content of the simulated time series of each subfault. The rupture begins with a high corner frequency and progresses to lower corner frequencies as the ruptured area grows. Limiting the number of active subfaults in the calculation of dynamic corner frequency can control the amplitude of lower frequencies. Our dynamic corner frequency approach has several advantages over previous formulations of the stochastic finite-fault method, including conservation of radiated energy at high frequencies regardless of subfault size, application to a broader mag-nitude range, and control of the relative amplitude of higher versus lower frequencies.
Empirical ground-motion Relations for Subduction-Zone Earthquakes and Their Applications to Cascadia and other regions
- Bull. Seism. Soc. Am
, 2003
"... Abstract 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 megath ..."
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Cited by 35 (1 self)
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Abstract 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 recordings 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 Nisqually 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 subduction-zone earthquakes. The large dataset enables improved determination of attenuation parameters and magnitude scaling, for both interface and in-slab events. Soil
Worldwide doublets of large shallow earthquakes
- Bull. Seismol. Soc. Am
, 1999
"... Abstract We investigated all the pairs of Mw>-- 7.5 shallow earthquakes in the Harvard catalog that occurred at a centroid istance of less than 100 km. We showed that most of these pairs have similar focal mechanisms. Because these earthquakes generally should have focal regions in excess of 100 ..."
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Cited by 30 (7 self)
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Abstract We investigated all the pairs of Mw>-- 7.5 shallow earthquakes in the Harvard catalog that occurred at a centroid istance of less than 100 km. We showed that most of these pairs have similar focal mechanisms. Because these earthquakes generally should have focal regions in excess of 100 km diameter, their rupture zones apparently intersect. For all these pairs, the time interval is significantly less than the time span needed for plate motion to accumulate the strain released by the first event. These observations conflict strongly with quasi-periodic recurrence models on which the seismic gap hypothesis i based. Power-law recurrence fits these earthquake ob-servations much better.
Recalculated probability of M 7 earthquakes beneath the Sea of Marmara
, 2004
"... [1] New earthquake probability calculations are made for the Sea of Marmara region and the city of Istanbul, providing a revised forecast and an evaluation of time-dependent interaction techniques. Calculations incorporate newly obtained bathymetric images of the North Anatolian fault beneath the Se ..."
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Cited by 27 (3 self)
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[1] New earthquake probability calculations are made for the Sea of Marmara region and the city of Istanbul, providing a revised forecast and an evaluation of time-dependent interaction techniques. Calculations incorporate newly obtained bathymetric images of the North Anatolian fault beneath the Sea of Marmara [Le Pichon et al., 2001; Armijo et al., 2002]. Newly interpreted fault segmentation enables an improved regional A.D. 1500– 2000 earthquake catalog and interevent model, which form the basis for time-dependent probability estimates. Calculations presented here also employ detailed models of coseismic and postseismic slip associated with the 17 August 1999 M = 7.4 Izmit earthquake to investigate effects of stress transfer on seismic hazard. Probability changes caused by the 1999 shock depend on Marmara Sea fault-stressing rates, which are calculated with a new finite element model. The combined 2004–2034 regional Poisson probability of M 7 earthquakes is 38%, the regional time-dependent probability is 44 ± 18%, and incorporation of stress transfer raises it to 53 ± 18%. The most important effect of adding time dependence and stress transfer to the calculations is an increase in the 30 year probability of a M 7 earthquake affecting Istanbul. The 30 year Poisson
2001b). Source parameters of earthquakes in eastern and western North America based on finite-fault modeling
"... Abstract The ground motion from large earthquakes is often predicted based on finite-fault modeling, in which the fault plane is discretized into small independently rupturing subfaults; the radiation from all subfaults is summed at the observation point. Despite the success of the method in matchin ..."
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Cited by 27 (10 self)
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Abstract The ground motion from large earthquakes is often predicted based on finite-fault modeling, in which the fault plane is discretized into small independently rupturing subfaults; the radiation from all subfaults is summed at the observation point. Despite the success of the method in matching observed ground-motion characteristics, the physical interpretation of the subfaults has remained largely unclear, and a rationale for the choice of the subfault attributes has been lacking. Two key parameters—the subfault size and the maximum slip velocity on the fault—govern the amplitude of the source spectrum at intermediate and high frequencies, respectively. We determined these key source parameters, on an event-by-event basis, for all well-recorded moderate to large earthquakes in western North America (WNA) by fitting simulated to observed response spectra. We compare the values of these source parameters with those obtained previously for eastern North America (ENA) and the Michoacan, Mexico, earthquakes (a total of 26 modeled events). We find that the characteristic subevent size increases linearly with moment magnitude in an apparently deterministic manner. The subevent size relationship obtained
