Report on workshop to incorporate basin response in the design of tall buildings in the Puget Sound region, Washington

Chang, Susan W.; Frankel, Arthur; Weaver, Craig S.

doi:10.3133/ofr20141196

Cited by 14 publications

(16 citation statements)

References 20 publications

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“…However, these sites are observed to have amplification of factors of two to three relative to rock sites with similar V S30 values south of the Seattle basin, for crustal and intraslab earthquakes, and in this region, Z 2.5 -based models of basin amplification better reproduce observed ground motion trends with basin depth (e.g. Chang et al, 2014; Frankel et al, 2009). Furthermore, the two workshop reports pointed out that the NGA-West2 data set included few strong-motion recordings from sites with conditions similar to what is observed in the Seattle basin (deep basins with V S30 values of 400–700 m/s), and the NGA-West2 models of basin amplification were largely based on data from California and Japan, and did not consider data from the Seattle region.…”

Section: Basin Amplification Of Ground Shaking In the Wusmentioning

confidence: 72%

“…In 2013 and 2018, workshops of engineers and seismologists were convened by the city of Seattle and the USGS to discuss incorporation of basin amplification effects into the Risk-Targeted Maximum Considered Earthquake (MCE R ) ground motions used in the design of high-rise buildings in Seattle (Chang et al, 2014; Wirth et al, 2018a, 2018b). An important recommendation from the 2013 workshop was to use Z 2.5 rather than Z 1.0 to characterize basin amplification in Seattle.…”

Section: Basin Amplification Of Ground Shaking In the Wusmentioning

confidence: 99%

“…There are several alternative ways to account for basin amplification and deamplification effects in the NSHMs, and we considered several methods. For the final hazard assessment, we ended up simply adding the basin depth term from CB14 to the ground motions obtained from the V S30 amplified GMMs as done by Chang et al (2014). This is a simple method that allows for inclusion of the native V S30 terms while still including basin effects using the CB14 GMM which does not depend directly on the V S30 term.…”

Section: Basin Amplification Of Ground Shaking In the Wusmentioning

confidence: 99%

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The 2018 update of the US National Seismic Hazard Model: Overview of model and implications

et al. 2019

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During 2017–2018, the National Seismic Hazard Model for the conterminous United States was updated as follows: (1) an updated seismicity catalog was incorporated, which includes new earthquakes that occurred from 2013 to 2017; (2) in the central and eastern United States (CEUS), new ground motion models were updated that incorporate updated median estimates, modified assessments of the associated epistemic uncertainties and aleatory variabilities, and new soil amplification factors; (3) in the western United States (WUS), amplified shaking estimates of long-period ground motions at sites overlying deep sedimentary basins in the Los Angeles, San Francisco, Seattle, and Salt Lake City areas were incorporated; and (4) in the conterminous United States, seismic hazard is calculated for 22 periods (from 0.01 to 10 s) and 8 uniform VS30 maps (ranging from 1500 to 150 m/s). We also include a description of updated computer codes and modeling details. Results show increased ground shaking in many (but not all) locations across the CEUS (up to ~30%), as well as near the four urban areas overlying deep sedimentary basins in the WUS (up to ~50%). Due to population growth and these increased hazard estimates, more people live or work in areas of high or moderate seismic hazard than ever before, leading to higher risk of undesirable consequences from forecasted future ground shaking.

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Section: Basin Amplification Of Ground Shaking In the Wusmentioning

confidence: 72%

Section: Basin Amplification Of Ground Shaking In the Wusmentioning

confidence: 99%

Section: Basin Amplification Of Ground Shaking In the Wusmentioning

confidence: 99%

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The 2018 update of the US National Seismic Hazard Model: Overview of model and implications

et al. 2019

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“…Currently enforced basin amplification factors in the city of Seattle 40 for performance‐based seismic design projects require amplification factors of 1‐2 for periods in the range 0‐2 s, and amplification factors of 2 for periods greater than 2 s. These observations were derived from the selection of a reference site immediately outside the Seattle basin. Similar basin amplification factors are reported in this study when using a reference site immediately outside the basin, i.e., West Vancouver (REF‐B in Figure 1A).…”

Section: Spectral Acceleration Basin Amplification Factors In Metro Vmentioning

confidence: 99%

Impacts of simulated M9 Cascadia Subduction Zone earthquakes considering amplifications due to the Georgia sedimentary basin on reinforced concrete shear wall buildings

Kakoty

Dyaga

Hutt

2020

Earthq Engng Struct Dyn

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Southwest British Columbia has the potential to experience large-magnitude earthquakes generated by the Cascadia Subduction Zone (CSZ). Buildings in Metro Vancouver are particularly vulnerable to these earthquakes because the region lies above the Georgia sedimentary basin, which can amplify the intensity of ground motions, particularly at medium-to-long periods. Earthquake design provisions in Canada neglect basin amplification and the consequences of accounting for these effects are uncertain. By leveraging a suite of physicsbased simulations of M9 CSZ earthquakes, we develop site-specific and perioddependent spectral acceleration basin amplification factors throughout Metro Vancouver. The M9 simulations, which explicitly account for basin amplification for periods greater than 1s, are benchmarked against the 2016 BC Hydro ground motion model (GMM), which neglects such effects. Outside the basin, empirical and simulated seismic hazard estimates are consistent. However, for sites within the basin and periods in the 1-5 s range, GMMs significantly underestimate the hazard. The proposed basin amplification factors vary as a function of basin depth, reaching a geometric mean value as high as 4.5 at a 2-s period, with respect to a reference site located just outside the basin. We evaluate the impact of the M9 simulations on tall reinforced concrete shear wall buildings, which are predominant in the region, by developing a suite of idealized structural systems that capture the strength and ductility intended by historical seismic design provisions in Canada. Ductility demands and collapse risk conditioned on the occurrence of the M9 simulations were found to exceed those associated with ground motion shaking intensities corresponding to the 975 and 2475-year return periods, far exceeding the ∼500-year return period of M9 CSZ earthquakes.

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“…For example, the Southern California Earthquake Center (SCEC) developed site-specific, risk-adjusted, maximum considered earthquake (MCE R ) spectra for the metropolitan Los Angeles area that consider the effects of basins, predicted using empirical ground-motion models and three-dimensional (3D) physics-based simulations (using the CyberShake computational platform, Crouse et al, 2018). The City of Seattle (Director’s Rule 5, City of Seattle Department of Planning and Developments, 2015) required that basin effects be considered within performance-based design (PBD) procedures for buildings above 73 m (240 ft) without a dual lateral-force resisting system (Chang et al, 2014). The basin amplification factors were then increased and applied to all projects that use a site-specific hazard analysis in 2018 (Director’s Rule 20, City of Seattle Department of Planning and Developments, 2018; Wirth et al, 2018a).…”

Section: Introductionmentioning

confidence: 99%

Design strategies to achieve target collapse risks for reinforced concrete wall buildings in sedimentary basins

et al. 2020

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Studies of recorded ground motions and simulations have shown that deep sedimentary basins can greatly increase the damage expected during earthquakes. Unlike past earthquake design provisions, future ones are likely to consider basin effects, but the consequences of accounting for these effects are uncertain. This article quantifies the impacts of basin amplification on the collapse risk of 4- to 24-story reinforced concrete wall building archetypes in the uncoupled direction. These buildings were designed for the seismic hazard level in Seattle according to the ASCE 7-16 design provisions, which neglect basin effects. For ground motion map frameworks that do consider basin effects (2018 USGS National Seismic Hazard Model), the average collapse risk for these structures would be 2.1% in 50 years, which exceeds the target value of 1%. It is shown that this 1% target could be achieved by: (1) increasing the design forces by 25%, (2) decreasing the drift limits from 2.0% to 1.25%, or (3) increasing the median drift capacity of the gravity systems to exceed 9%. The implications for these design changes are quantified in terms of the cross-sectional area of the walls, longitudinal reinforcement, and usable floor space. It is also shown that the collapse risk increases to 2.8% when the results of physics-based ground motion simulations are used for the large-magnitude Cascadia subduction interface earthquake contribution to the hazard. In this case, it is necessary to combine large changes in the drift capacities, design forces, and/or drift limits to meet the collapse risk target.

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Report on workshop to incorporate basin response in the design of tall buildings in the Puget Sound region, Washington

Cited by 14 publications

References 20 publications

The 2018 update of the US National Seismic Hazard Model: Overview of model and implications

The 2018 update of the US National Seismic Hazard Model: Overview of model and implications

Impacts of simulated M9 Cascadia Subduction Zone earthquakes considering amplifications due to the Georgia sedimentary basin on reinforced concrete shear wall buildings

Design strategies to achieve target collapse risks for reinforced concrete wall buildings in sedimentary basins

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