Earthquake Magnitude and Lg Q Variations between the Grenville and Northern Appalachian Geologic Provinces of Eastern Canada

2020 ◽  
Vol 110 (2) ◽  
pp. 698-714 ◽  
Author(s):  
H. K. Claire Perry ◽  
Allison L. Bent ◽  
Daniel E. McNamara ◽  
Stephen Crane ◽  
Michal Kolaj
Keyword(s):  
Seismic Hazard ◽  
Hazard Analysis ◽  
Vertical Component ◽  
Earthquake Magnitude ◽  
Waveform Analysis ◽  
Eastern Canada ◽  
Frequency Dependent ◽  
Motion Models ◽  
Anelastic Attenuation ◽  
Specific Frequency

ABSTRACT This article assesses the ability of regionally specific, frequency-dependent crustal attenuation (1/Q) to reduce mean magnitude discrepancies between seismic stations in the northern Appalachian and Grenville provinces (NAP and GP) of Canada. LgQ(f) is an important parameter in ground-motion models used in probabilistic seismic hazard analysis. Discrepancies in regional magnitude estimates have long been noted to exist between stations in the two provinces for common event origins. Such discrepancies could arise from systematic site condition variations between the geologic provinces or from varying crustal attenuative properties. To evaluate the effect of frequency-dependent anelastic attenuation, LgQ(f) on estimated magnitudes, we analyze Lg amplitudes from >6000 waveforms recorded by Grenville and northern Appalachian receivers from 420 natural earthquakes of MN magnitude 3–5.6. Waveform analysis is strictly limited to analyst-reviewed, vertical-component waveforms in which Lg is clearly identified, ensuring that the datasets exhibit dominant, high-frequency energy in the Lg velocity window. LgQ(f) is found to be higher in the GP than in the northern Appalachians. In the Grenville, Q(f)=761(±145)f0.25(±0.014), and in the northern Appalachians, attenuation is higher: Q(f)=506(±172)f0.33(±0.310). Earthquake magnitude determined using the peak amplitude of the Lg phase (mbLg) for eastern Canada is corrected to incorporate the frequency-dependent, regionally specific LgQ(f) determined in this study. Using the new LgQ(f) values diminishes and nearly resolves magnitude discrepancies between the provinces. Correcting regional magnitude discrepancies between provinces is critical for reliable regional seismic hazard estimates because magnitude error in a particular region could lead to increased uncertainty in seismic hazard models.

The High-Frequency Decay Slope of Spectra (Kappa) for M≥3.5 Earthquakes on Rock Sites in Eastern and Western Canada

2020 ◽  
Vol 110 (2) ◽  
pp. 471-488 ◽  
Author(s):  
Samantha M. Palmer ◽  
Gail M. Atkinson
Keyword(s):  
Ground Motion ◽  
Classical Method ◽  
Vertical Component ◽  
Western Canada ◽  
S Wave ◽  
Motion Modeling ◽  
Eastern Canada ◽  
General Observation ◽  
Anelastic Attenuation ◽  
Two Parameters

ABSTRACT Spectral decay of ground-motion amplitudes at high frequencies is primarily influenced by two parameters: site-related kappa (κ0) and regional Q (quality factor, inversely proportional to anelastic attenuation). We examine kappa and apparent Q-values (Qa) for M≥3.5 earthquakes recorded at seismograph stations on rock sites in eastern and western Canada. Our database contains 20 earthquakes recorded on nine stations in eastern Canada and 404 earthquakes recorded on eight stations in western Canada, resulting in 105 and 865 Fourier amplitude spectra, respectively. We apply two different methods: (1) a modified version of the classical S-wave acceleration method; and (2) a new stacking method that is consistent with the use of kappa in ground-motion modeling. The results are robust with respect to the method used and also with respect to the frequency band selected, which ranges from 9 to 38 Hz depending on the region, event, and method. Kappa values obtained from the classical method are consistent with those of the stacked method, but the stacked method provides a lower uncertainty. A general observation is that kappa is usually larger, and apparent Q is smaller, for the horizontal component in comparison to the vertical component. We determine an average regional κ0=7  ms (horizontal) and 0 ms (vertical) for rock sites in eastern Canada; we obtain κ0=19  ms (horizontal) and 14 ms (vertical) for rock sites in western Canada. We note that kappa measurements are quite sensitive to details of data selection criteria and methodology, and may be significantly influenced by site effects, resulting in large site-to-site variability.

Ranking of Ground-Motion Models (GMMs) for Use in Probabilistic Seismic Hazard Analysis for Iran Based on an Independent Data Set

2020 ◽  
Author(s):  
Zoya Farajpour ◽  
Milad Kowsari ◽  
Shahram Pezeshk ◽  
Benedikt Halldorsson
Keyword(s):  
Seismic Hazard ◽  
Ground Motion ◽  
Selection Process ◽  
Hazard Analysis ◽  
Probabilistic Seismic Hazard Analysis ◽  
Seismic Hazard Analysis ◽  
Probabilistic Seismic Hazard ◽  
Data Set ◽  
Motion Models ◽  
Ground Motion Models

ABSTRACT We apply three data-driven selection methods, log-likelihood (LLH), Euclidean distance-based ranking (EDR), and deviance information criterion (DIC), to objectively evaluate the predictive capability of 10 ground-motion models (GMMs) developed from Iranian and worldwide data sets against a new and independent Iranian strong-motion data set. The data set includes, for example, the 12 November 2017 Mw 7.3 Ezgaleh earthquake and the 25 November 2018 Mw 6.3 Sarpol-e Zahab earthquake and includes a total of 201 records from 29 recent events with moment magnitudes 4.5≤Mw≤7.3 with distances up to 275 km. The results of this study show that the prior sigma of the GMMs acts as the key measure used by the LLH and EDR methods in the ranking against the data set. In some cases, this leads to the resulting model bias being ignored. In contrast, the DIC method is free from such ambiguity as it uses the posterior sigma as the basis for the ranking. Thus, the DIC method offers a clear advantage of partially removing the ergodic assumption from the GMM selection process and allows a more objective representation of the expected ground motion at a specific site when the ground-motion recordings are homogeneously distributed in terms of magnitudes and distances. The ranking results thus show that the local models that were exclusively developed from Iranian strong motions perform better than GMMs from other regions for use in probabilistic seismic hazard analysis in Iran. Among the Next Generation Attenuation-West2 models, the GMMs by Boore et al. (2014) and Abrahamson et al. (2014) perform better. The GMMs proposed by Darzi et al. (2019) and Farajpour et al. (2019) fit the recorded data well at short periods (peak ground acceleration and pseudoacceleration spectra at T=0.2  s). However, at long periods, the models developed by Zafarani et al. (2018), Sedaghati and Pezeshk (2017), and Kale et al. (2015) are preferable.

Ranking of several ground-motion models for seismic hazard analysis in Iran

2008 ◽  
Vol 5 (3) ◽  
pp. 301-310 ◽  
Author(s):  
H Ghasemi ◽  
M Zare ◽  
Y Fukushima
Keyword(s):  
Seismic Hazard ◽  
Ground Motion ◽  
Hazard Analysis ◽  
Seismic Hazard Analysis ◽  
Motion Models ◽  
Ground Motion Models

scholarly journals A seismic hazard analysis considering uncertainty during earthquake magnitude conversion

2013 ◽  
Vol 1 (3) ◽  
pp. 2109-2126
Author(s):  
J. P. Wang ◽  
Y. Xu
Keyword(s):  
Seismic Hazard ◽  
Hazard Analysis ◽  
Analytical Framework ◽  
Earthquake Magnitude ◽  
Seismic Hazard Analysis ◽  
Local Magnitude ◽  
Empirical Relationships ◽  
Magnitude Conversion ◽  
Earthquake Magnitude Conversion ◽  
Earthquake Data

Abstract. The magnitude of earthquakes can be described with different units, such as moment magnitude Mw and local magnitude ML. A few empirical relationships between the two have been suggested, such as the model calibrated with the earthquake data in Taiwan. Understandably, such a conversion relationship through regression analysis is associated with some error because of inevitable data scattering. Therefore, the underlying scope of this study is to conduct a seismic hazard analysis, during which the uncertainty from earthquake magnitude conversion was properly taken into account. With a new analytical framework developed for this task, it was found that there is a 10% probability in 50 yr that PGA could exceed 0.28 g at the study site in North Taiwan.

Definition of Lateral Spread Displacement for Regional Risk Assessments of Pipeline Vulnerability

2010 ◽  
Author(s):  
Douglas G. Honegger ◽  
Mujib Rahman ◽  
Humberto Puebla ◽  
Dharma Wijewickreme ◽  
Anthony Augello
Keyword(s):  
Risk Assessment ◽  
British Columbia ◽  
Seismic Hazard ◽  
Seismic Risk ◽  
Hazard Analysis ◽  
Earthquake Magnitude ◽  
Seismic Hazard Analysis ◽  
Lateral Spread ◽  
Probabilistic Seismic Hazard ◽  
Ground Shaking

Terasen Gas Inc. (Terasen) operates a natural gas supply and distribution system situated within one of the zones of the highest seismic activity in Canada. The region encompasses significant areas underlain by marine, deltaic, and alluvial soil deposits, some of which are considered to be susceptible to liquefaction and large ground movements when subjected to earthquake ground shaking. Terasen undertook an assessment of seismic risks to its transmission and key intermediate pressure pipelines in the Lower Mainland in 1994 [1]. The seismic assessment focused on approximately 500 km of steel pipelines ranging from NPS 8 to NPS 42 and operating at pressures from 1900 to 4020 kPa. The 1994 risk assessment provided the basis for detailed site-specific assessment and seismic upgrade programs to retrofit its existing system to reduce risks to acceptable levels. While the general approach undertaken in 1994 remains technically sound, advancements have been made over the past 15 years in the understanding of earthquake hazards and their impact on pipelines. In particular, estimates of the earthquake ground shaking hazard in British Columbia as published by Geological Survey of Canada (GSC) have recently been updated and incorporated into the 2005 National Building Code of Canada (NBCC). In addition, empirical methods of estimating lateral spread ground displacements have been improved as new case-history information has become available. Given these changes, Terasen decided in 2009 to reexamine the seismic risk to Terasen’s pipelines. The scope of the updated seismic risk study was expanded over that in 1994 to include pipelines on Vancouver Island and the Interior of British Columbia. For regional assessments, estimates of lateral spread displacements are necessarily based upon empirical formulations that relate displacement to variables of earthquake severity (earthquake magnitude and distance), susceptibility to liquefaction (density, grain size, fines content), and topography (distance from a river bank or ground slope). Implementing empirical formulae with the results of probabilistic seismic hazard calculations is complicated by the fact that the empirical approach requires earthquake magnitude and distance, as a parametric couple, to be related to the ground shaking severity. However, but such a relationship does not exist in the estimates of mean or modal earthquake magnitude and distance disaggregated from a probabilistic seismic hazard analysis. This paper presents an overview of the approach to regional risk assessment undertaken by Terasen and discusses the unique approach adopted for determining lateral spread displacements consistent with the probabilistic seismic hazard analysis.

Non-Ergodic Site Response in Seismic Hazard Analysis

2017 ◽  
Vol 33 (4) ◽  
pp. 1385-1414 ◽  
Author(s):  
Jonathan P. Stewart ◽  
Kioumars Afshari ◽  
Christine A. Goulet
Keyword(s):  
Standard Deviation ◽  
Seismic Hazard ◽  
Ground Motion ◽  
Site Response ◽  
Hazard Analysis ◽  
Specific Site ◽  
Uniform Hazard Spectra ◽  
Motion Models ◽  
Site Term ◽  
Site Variability

Probabilistic seismic hazard analyses are usually performed with semi-empirical ground motion models (GMMs) following the ergodic assumption whereby average source, path, and site effects from global databases apply for a specific site of interest. Site-specific site response is likely to differ from the global average conditional on site parameters used in GMMs (typically V S30 and basin depth). Non-ergodic site response can be evaluated using on-site ground motion recordings and/or one-dimensional wave propagation analyses, and allows site-to-site variability to be removed from the within-event standard deviation. Relative to ergodic, non-ergodic hazard analyses often reduce ground motions at long return periods. We describe procedures for replacing the site term in GMMs with a non-ergodic nonlinear mean over its appropriate range of periods (returning to the ergodic mean outside that range). We also present procedures for computing non-ergodic standard deviation by removing site-to-site variability while considering effects of soil nonlinearity. We illustrate application of these procedures, and their effect on hazard curves and uniform hazard spectra, as implemented in OpenSHA.

Probabilistic Seismic Hazard Analysis in California Using Nonergodic Ground Motion Models

2019 ◽  
Vol 109 (4) ◽  
pp. 1235-1249 ◽  
Author(s):  
Norman Abrahamson ◽  
Nicolas Kuehn ◽  
Melanie Walling ◽  
Niels Landwehr
Keyword(s):  
Seismic Hazard ◽  
Ground Motion ◽  
Hazard Analysis ◽  
Probabilistic Seismic Hazard Analysis ◽  
Seismic Hazard Analysis ◽  
Probabilistic Seismic Hazard ◽  
Motion Models ◽  
Ground Motion Models

scholarly journals Selection and ranking of ground motion models for seismic hazard analysis in the Pyrenees

2007 ◽  
Vol 11 (1) ◽  
pp. 87-100 ◽  
Author(s):  
Stéphane Drouet ◽  
Frank Scherbaum ◽  
Fabrice Cotton ◽  
Annie Souriau
Keyword(s):  
Seismic Hazard ◽  
Ground Motion ◽  
Hazard Analysis ◽  
Seismic Hazard Analysis ◽  
Motion Models ◽  
Ground Motion Models ◽  
Selection And Ranking
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