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Giovanni Costa - One of the best experts on this subject based on the ideXlab platform.
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On the incorporation of the effect of Crustal Structure into empirical strong ground motion estimation
Bulletin of Earthquake Engineering, 2015Co-Authors: John Douglas, Peter Suhadolc, Giovanni CostaAbstract:This article has two purposes. Firstly, a validation exercise of the modal summation technique for the computation of synthetic strong-motion records is performed for two regions of Europe (Umbria-Marche and south Iceland), using a variety of region specific Crustal Structure models, by comparing the predicted ground motion amplitudes with observed motions. It is found that the rate of decay of ground motions is well predicted by the theoretical decay curves but that the absolute size of the ground motions is underpredicted by the synthetic time-histories. This is thought to be due to the presence of low-velocity surface layers that amplify the ground motions but are not included in the Crustal Structure models used to compute the synthetic time-histories.
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The importance of Crustal Structure in explaining the observed uncertainties in ground motion estimation
Bulletin of Earthquake Engineering, 2007Co-Authors: John Douglas, Peter Suhadolc, Hideo Aochi, Giovanni CostaAbstract:In this short article, the possible reduction in the standard deviation of empirical ground motion estimation equations through the modelling of the effect of Crustal Structure is assessed through the use of ground-motion simulations. Simulations are computed for different source-to-site distances, focal depths, focal mechanisms and for Crustal models of the Pyrenees, the western Alps and the upper Rhine Graben. Through the method of equivalent hypocentral distance introduced by Douglas et al. [(2004) Bull Earthquake Eng 2(1): 75–99] to model the effect of Crustal Structure in empirical equations, the scatter associated with such equations derived using these simulated data could be reduced to zero if real-to-equivalent hypocentral distance mapping functions were derived for every combination of mechanism, depth and Crustal Structure present in the simulated dataset. This is, obviously, impractical. The relative importance of each parameter in affecting the decay of ground motions is assessed here. It is found that variation in focal depth is generally more important than the effect of Crustal Structure when deriving the real-to-equivalent hypocentral distance mapping functions. In addition, mechanism and magnitude do not have an important impact on the decay rate.
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The importance of Crustal Structure in explaining the observed uncertainties in ground motion estimation
2005Co-Authors: John Douglas, Peter Suhadolc, Hideo Aochi, Giovanni CostaAbstract:In this paper, the possible reduction in standard deviation of empirical ground motion estimation equations through the incorporation of Crustal Structure is assessed through the use of ground-motion simulations. Simulations are computed for different source-to-site distances, focal depths, focal mechanisms and for Crustal models of the Pyrenees, the western Alps and the upper Rhine Graben. Through the use of the method of equivalent hypocentral distance introduced by Douglas et al. (2004) to model the effect of Crustal Structure in empirical equations the scatter associated with ground motion estimation equations derived using these simulated data could be reduced to zero if real-to-equivalent hypocentral distance mapping functions were derived for every combination of mechanism, depth and Crustal Structure present in the simulated dataset. This is, obviously, unrealistic for a practical use of the method. The relative importance of each parameter in affecting the decay of ground motions is assessed here. It is found that variation in focal depth is generally more important than the effect of Crustal Structure when deriving the real-to-equivalent hypocentral distance mapping functions.
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On the Incorporation of the Effect of Crustal Structure into Empirical Strong Ground Motion Estimation
Bulletin of Earthquake Engineering, 2004Co-Authors: John Douglas, Peter Suhadolc, Giovanni CostaAbstract:This article has two purposes. Firstly, a validation exercise of the modal summation technique for the computation of synthetic strong-motion records is performed for two regions of Europe (Umbria-Marche and south Iceland), using a variety of region specific Crustal Structure models, by comparing the predicted ground motion amplitudes with observed motions. It is found that the rate of decay of ground motions is well predicted by the theoretical decay curves but that the absolute size of the ground motions is underpredicted by the synthetic time-histories. This is thought to be due to the presence of low-velocity surface layers that amplify the ground motions but are not included in the Crustal Structure models used to compute the synthetic time-histories. Secondly, a new distance metric based on the computed theoretical decay curves is introduced which should have the ability to model the complex decay of strong ground motions. The ability of this new distance metric to reduce the associated scatter in empirically derived equations for the estimation of strong ground motions is tested. It is found that it does not lead to a reduction in the scatter but this is thought to be due to the use of Crustal Structure models that are not accurate or detailed enough for the regions studied.
John Douglas - One of the best experts on this subject based on the ideXlab platform.
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On the incorporation of the effect of Crustal Structure into empirical strong ground motion estimation
Bulletin of Earthquake Engineering, 2015Co-Authors: John Douglas, Peter Suhadolc, Giovanni CostaAbstract:This article has two purposes. Firstly, a validation exercise of the modal summation technique for the computation of synthetic strong-motion records is performed for two regions of Europe (Umbria-Marche and south Iceland), using a variety of region specific Crustal Structure models, by comparing the predicted ground motion amplitudes with observed motions. It is found that the rate of decay of ground motions is well predicted by the theoretical decay curves but that the absolute size of the ground motions is underpredicted by the synthetic time-histories. This is thought to be due to the presence of low-velocity surface layers that amplify the ground motions but are not included in the Crustal Structure models used to compute the synthetic time-histories.
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The importance of Crustal Structure in explaining the observed uncertainties in ground motion estimation
Bulletin of Earthquake Engineering, 2007Co-Authors: John Douglas, Peter Suhadolc, Hideo Aochi, Giovanni CostaAbstract:In this short article, the possible reduction in the standard deviation of empirical ground motion estimation equations through the modelling of the effect of Crustal Structure is assessed through the use of ground-motion simulations. Simulations are computed for different source-to-site distances, focal depths, focal mechanisms and for Crustal models of the Pyrenees, the western Alps and the upper Rhine Graben. Through the method of equivalent hypocentral distance introduced by Douglas et al. [(2004) Bull Earthquake Eng 2(1): 75–99] to model the effect of Crustal Structure in empirical equations, the scatter associated with such equations derived using these simulated data could be reduced to zero if real-to-equivalent hypocentral distance mapping functions were derived for every combination of mechanism, depth and Crustal Structure present in the simulated dataset. This is, obviously, impractical. The relative importance of each parameter in affecting the decay of ground motions is assessed here. It is found that variation in focal depth is generally more important than the effect of Crustal Structure when deriving the real-to-equivalent hypocentral distance mapping functions. In addition, mechanism and magnitude do not have an important impact on the decay rate.
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The importance of Crustal Structure in explaining the observed uncertainties in ground motion estimation
2005Co-Authors: John Douglas, Peter Suhadolc, Hideo Aochi, Giovanni CostaAbstract:In this paper, the possible reduction in standard deviation of empirical ground motion estimation equations through the incorporation of Crustal Structure is assessed through the use of ground-motion simulations. Simulations are computed for different source-to-site distances, focal depths, focal mechanisms and for Crustal models of the Pyrenees, the western Alps and the upper Rhine Graben. Through the use of the method of equivalent hypocentral distance introduced by Douglas et al. (2004) to model the effect of Crustal Structure in empirical equations the scatter associated with ground motion estimation equations derived using these simulated data could be reduced to zero if real-to-equivalent hypocentral distance mapping functions were derived for every combination of mechanism, depth and Crustal Structure present in the simulated dataset. This is, obviously, unrealistic for a practical use of the method. The relative importance of each parameter in affecting the decay of ground motions is assessed here. It is found that variation in focal depth is generally more important than the effect of Crustal Structure when deriving the real-to-equivalent hypocentral distance mapping functions.
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On the Incorporation of the Effect of Crustal Structure into Empirical Strong Ground Motion Estimation
Bulletin of Earthquake Engineering, 2004Co-Authors: John Douglas, Peter Suhadolc, Giovanni CostaAbstract:This article has two purposes. Firstly, a validation exercise of the modal summation technique for the computation of synthetic strong-motion records is performed for two regions of Europe (Umbria-Marche and south Iceland), using a variety of region specific Crustal Structure models, by comparing the predicted ground motion amplitudes with observed motions. It is found that the rate of decay of ground motions is well predicted by the theoretical decay curves but that the absolute size of the ground motions is underpredicted by the synthetic time-histories. This is thought to be due to the presence of low-velocity surface layers that amplify the ground motions but are not included in the Crustal Structure models used to compute the synthetic time-histories. Secondly, a new distance metric based on the computed theoretical decay curves is introduced which should have the ability to model the complex decay of strong ground motions. The ability of this new distance metric to reduce the associated scatter in empirically derived equations for the estimation of strong ground motions is tested. It is found that it does not lead to a reduction in the scatter but this is thought to be due to the use of Crustal Structure models that are not accurate or detailed enough for the regions studied.
D.a. Forsyth - One of the best experts on this subject based on the ideXlab platform.
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Modeling wide-angle seismic data for Crustal Structure: southeastern Grenville Province
Journal of Geophysical Research, 1994Co-Authors: Colin A. Zelt, D.a. ForsythAbstract:A modeling methodology for obtaining two-dimensional (2-D) Crustal Structure from wide-angle seismic data is applied to data from the southeastern Grenville Province. Pre-modeling steps include (1) assignment of arrival pick uncertainties for appropriate data fitting and weighting using an empirical relationship based on signal-to-noise ratio, (2) using a modified form of travel time reciprocity to avoid unreasonable levels of model heterogeneity, and (3) identifying data unsuitable for 2-D modeling. The goal of the travel time inversion-amplitude modeling approach is to obtain a minimum-Structure and minimum-parameter model that takes into account both horizontal and vertical variations in the resolution of typical wide-angle data. Each step of a layer-stripping procedure involves a series of inversions in which a one-dimensional or simple starting model is improved with additional velocity and/or interface nodes until a satisfactory trade-off between travel time fit, parameter resolution and complete ray coverage of all source-receiver pairs is achieved. Using zero vertical-velocity gradient layers and head waves during preliminary first-arrival inversion can (1) decrease the number of intermediate models, (2) allow greater lateral heterogeneity to be imaged, and (3) simplify incorporation of amplitude modeling constraints into the final model. Using amplitude-distance curves allows quantitative modeling of the relative amplitude and offset variations of phases. Discrepancies between observed and calculated reflection amplitudes are used to infer fundamental, non step-like velocity changes at layer boundaries. Later arrivals due to unresolved velocity anomalies are modeled using reflecting segments that “float” within the model without an associated velocity Structure. These reflectors provide a spatial image like that obtained from vertical-incidence reflection data, as opposed to a velocity image. The model of Grenville Crustal Structure is more detailed than a model obtained from a previous interpretation of the data and includes elements analogous to those imaged in nearby deep reflection data. A Crustal-scale zone of wide-angle reflectors with an average easterly apparent dip of 13° defines a major Grenvillian terrane boundary.
Peter Suhadolc - One of the best experts on this subject based on the ideXlab platform.
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On the incorporation of the effect of Crustal Structure into empirical strong ground motion estimation
Bulletin of Earthquake Engineering, 2015Co-Authors: John Douglas, Peter Suhadolc, Giovanni CostaAbstract:This article has two purposes. Firstly, a validation exercise of the modal summation technique for the computation of synthetic strong-motion records is performed for two regions of Europe (Umbria-Marche and south Iceland), using a variety of region specific Crustal Structure models, by comparing the predicted ground motion amplitudes with observed motions. It is found that the rate of decay of ground motions is well predicted by the theoretical decay curves but that the absolute size of the ground motions is underpredicted by the synthetic time-histories. This is thought to be due to the presence of low-velocity surface layers that amplify the ground motions but are not included in the Crustal Structure models used to compute the synthetic time-histories.
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The importance of Crustal Structure in explaining the observed uncertainties in ground motion estimation
Bulletin of Earthquake Engineering, 2007Co-Authors: John Douglas, Peter Suhadolc, Hideo Aochi, Giovanni CostaAbstract:In this short article, the possible reduction in the standard deviation of empirical ground motion estimation equations through the modelling of the effect of Crustal Structure is assessed through the use of ground-motion simulations. Simulations are computed for different source-to-site distances, focal depths, focal mechanisms and for Crustal models of the Pyrenees, the western Alps and the upper Rhine Graben. Through the method of equivalent hypocentral distance introduced by Douglas et al. [(2004) Bull Earthquake Eng 2(1): 75–99] to model the effect of Crustal Structure in empirical equations, the scatter associated with such equations derived using these simulated data could be reduced to zero if real-to-equivalent hypocentral distance mapping functions were derived for every combination of mechanism, depth and Crustal Structure present in the simulated dataset. This is, obviously, impractical. The relative importance of each parameter in affecting the decay of ground motions is assessed here. It is found that variation in focal depth is generally more important than the effect of Crustal Structure when deriving the real-to-equivalent hypocentral distance mapping functions. In addition, mechanism and magnitude do not have an important impact on the decay rate.
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The importance of Crustal Structure in explaining the observed uncertainties in ground motion estimation
2005Co-Authors: John Douglas, Peter Suhadolc, Hideo Aochi, Giovanni CostaAbstract:In this paper, the possible reduction in standard deviation of empirical ground motion estimation equations through the incorporation of Crustal Structure is assessed through the use of ground-motion simulations. Simulations are computed for different source-to-site distances, focal depths, focal mechanisms and for Crustal models of the Pyrenees, the western Alps and the upper Rhine Graben. Through the use of the method of equivalent hypocentral distance introduced by Douglas et al. (2004) to model the effect of Crustal Structure in empirical equations the scatter associated with ground motion estimation equations derived using these simulated data could be reduced to zero if real-to-equivalent hypocentral distance mapping functions were derived for every combination of mechanism, depth and Crustal Structure present in the simulated dataset. This is, obviously, unrealistic for a practical use of the method. The relative importance of each parameter in affecting the decay of ground motions is assessed here. It is found that variation in focal depth is generally more important than the effect of Crustal Structure when deriving the real-to-equivalent hypocentral distance mapping functions.
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On the Incorporation of the Effect of Crustal Structure into Empirical Strong Ground Motion Estimation
Bulletin of Earthquake Engineering, 2004Co-Authors: John Douglas, Peter Suhadolc, Giovanni CostaAbstract:This article has two purposes. Firstly, a validation exercise of the modal summation technique for the computation of synthetic strong-motion records is performed for two regions of Europe (Umbria-Marche and south Iceland), using a variety of region specific Crustal Structure models, by comparing the predicted ground motion amplitudes with observed motions. It is found that the rate of decay of ground motions is well predicted by the theoretical decay curves but that the absolute size of the ground motions is underpredicted by the synthetic time-histories. This is thought to be due to the presence of low-velocity surface layers that amplify the ground motions but are not included in the Crustal Structure models used to compute the synthetic time-histories. Secondly, a new distance metric based on the computed theoretical decay curves is introduced which should have the ability to model the complex decay of strong ground motions. The ability of this new distance metric to reduce the associated scatter in empirically derived equations for the estimation of strong ground motions is tested. It is found that it does not lead to a reduction in the scatter but this is thought to be due to the use of Crustal Structure models that are not accurate or detailed enough for the regions studied.
Robert W. Clayton - One of the best experts on this subject based on the ideXlab platform.
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Deep Crustal Structure of the Adare and Northern Basins, Ross Sea, Antarctica, from sonobuoy data
Earth and Planetary Science Letters, 2014Co-Authors: Michelle M. Selvans, Joann M. Stock, Robert W. Clayton, Steven C. Cande, Roi GranotAbstract:Extension associated with ultraslow seafloor spreading within the Adare Basin, in oceanic crust just north of the continental shelf in the Ross Sea, Antarctica, extended south into the Northern Basin. Magnetic and gravity anomaly data suggest continuity of Crustal Structure across the continental shelf break that separates the Adare and Northern Basins. We use sonobuoy refraction data and multi-channel seismic (MCS) reflection data collected during research cruise NBP0701, including 71 new sonobuoy records, to provide constraints on Crustal Structure in the Adare and Northern Basins. Adjacent 1D sonobuoy profiles along several MCS lines reveal deep Crustal Structure in the vicinity of the continental shelf break, and agree with additional sonobuoy data that document fast Crustal velocities (6000–8000 m/s) at shallow depths (1–6 km below sea level) from the Adare Basin to the continental shelf, a Structure consistent with that of other ultraslow-spread crust. Our determination of Crustal Structure in the Northern Basin only extends through sedimentary rock to the basement rock, and so cannot help to distinguish between different hypotheses for formation of the basin.
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Regional mapping of the Crustal Structure in southern California from receiver functions
Journal of Geophysical Research, 2007Co-Authors: Zhimei Yan, Robert W. ClaytonAbstract:Lateral variations of the Crustal Structure in southern California are determined from receiver function (RF) studies using data from the Southern California Seismic Network broadband stations and Los Angeles Regional Seismic Experiment surveys. The results include Crustal thickness estimates at the stations themselves, and where possible, cross sections are drawn. The large-scale Moho depth variation pattern generally correlates well with the current status of the Mesozoic batholith: Deep Moho of 35–39 km is observed beneath the western Peninsula Ranges, Sierra Nevada, and San Bernardino Mountains, where the batholith is relatively intact, and shallow Moho of 26–32 km is observed in the Mojave Desert, where the batholith is highly deformed and disrupted. High-resolution lateral variations of the Crustal Structure for individual geographic provinces are investigated, and distinctive features are identified. The Crustal Structure is strongly heterogeneous beneath the central Transverse Ranges, and deep Moho of 36–39 km is locally observed beneath several station groups in the western San Gabriel Mountains. Moho is relatively flat and smooth beneath the western Mojave Desert but gets shallower and complicated to the east. Anomalous RFs are observed at two stations in the eastern Mojave Desert, where a Moho step of ∼8–10 km is found between the NW and SE back-azimuthal groups of station DAN in the Fenner Valley. Asymmetric extension of the Salton Trough is inferred from the Moho geometry. Depth extension of several major faults, such as the San Andreas Fault and San Gabriel Fault, to the Moho is inferred.