Estimating Basin Effects Using M9 and Recent Research for Tall Building Design in Seattle

COSMOS Technical Session Susan Chang, Ph.D., P.E. I November 16, 2018 1 Seattle Basin

Data courtesy of Richard Blakely

2 Tall Buildings in Seattle (100+ m, 328+ ft)

Columbia Center Rainier Square Tower 1984, 933 ft 2020, 850 ft

Russell Investments Center F5 Tower 2006, 598 ft 2017, 660 ft 1201 3rd Avenue 1988, 772 ft

Smith Tower 1914, 462 ft

Background Source: www.skyscrapercenter.com/city/seattle 31 buildings 31 buildings

Figure from Doug Lindquist, Hart Crowser 3 March 4, 2013 Workshop Chang, S.W., Frankel., A.D., and Weaver, C.S., 2014, Report on Workshop to Incorporate Basin Response in the Design of Tall Buildings in the Puget Sound Region, Washington: U.S. Geological Survey Open-File Report 20- 14-1196, 28 p., https://pubs.usgs.gov/of/2014/1196/

• Basin amplification factors from crustal ground motion models (amplification factors a function of Z2.5 and Z1.0)

• Applied to MCER from PSHA for all EQ source types

Photo by Doug Lindquist, Hart Crowser

4 Recent Research Effect of Deep Basins on Structural Collapse During Large Subduction Earthquakes By Marafi, Eberhard, Berman, Wirth, and Frankel, Earthquake Spectra, August 2017

• Basin amplification factors for sites with Z2.5 > 3 km

Marafi et al. (2017) 5 Recent Research

Observed amplification of spectral response values for stiff sites in Seattle Basin referenced to Seward Park station – thin soil over firm rock 2003 under Olympics, M4.8 outside of basin

2001 near Satsop, M5.0

6 Recent Research Broadband Synthetic Seismograms for Magnitude 9 Earthquakes on the Cascadia Megathrust Based on 3D Simulations and Stochastic Synthetics (Part 1): Methodology and Overall Results By Frankel, Wirth, Marafi, Vidale, and Stephenson, submitted to BSSA January 2018, completed USGS internal review

7 USGS/SDCI March 22, 2018 Workshop Attendees Peer reviewers Geotechnical Consultants • C.B. Crouse (AECOM Seattle) • Doug Lindquist and Michael • Steve Dickenson (New Albion) Chamberlain (Hart Crowser) • • Ivan Wong (Lettis Consultants) Hamilton Puangnak and Melanie Walling (GeoEngineers) • Ali Shahbazian and Matt Gibson GMM developers and (Shannon & Wilson) seismologists • Reda Mikhail and Feng Li (Golder) • Norm Abrahamson (UC Berkeley) • Ken Campbell (CoreLogic) • Andreas Skarlatoudis (AECOM LA)

8 USGS/SDCI March 22, 2018 Workshop Attendees USGS/M9 SDCI • Art Frankel (USGS /M9) • Susan Chang • Erin Wirth (USGS /M9) • Scott Pawling • Marc Eberhard (UW /M9) • Steve Kramer (UW/M9)

Organizational Representatives • Kevin Aswegan (MKA, ASCE 7 Seismic Committee) • Andy Taylor (KPFF, SEAW EEC) • Douglas Beck (City of Bellevue)

9 Agenda • Basin factors from Ground Motion Models • How basin terms were developed for crustal GMMs • Presentations by Campbell and Abrahamson (Seyhan called in for part of workshop) • Incorporation of Basin Response in Seattle • What have we been doing since the 2013 workshop? • Presentations by GeoEngineers and Hart Crowser • Recent Research • Effect of Deep Basins on Structural Collapse During Large Subduction Earthquakes, Marafi et al., EQ Spectra, August 2017 • Broadband Synthetic Seismograms for M9 Earthquakes on the Cascadia Megathrust based on 3D Simulations and Stochastic Synthetics, Frankel et al., submitted to BSSA January 2018 • Basin Amplification Factors for Cascadia Based on the 2011 Tohoku, Japan Earthquake, Skarlatoudis et al., 11th NCEE, June 2018 (also USGS Final Technical Report, October 2015) • Site-specific MCER Response Spectra for Los Angeles Region based on 3D Numerical Simulations and the NGA West 2 Equations, Crouse, 11th NCEE, June 2018

10 Agenda

• Code Updates and Structural Design • ASCE 7-16 and 7-22 (C.B. Crouse) • Upcoming structural code changes (Andy Taylor) • Structural impacts (Kevin Aswegan)

• Discussion and Recommendations

11 Discussion and Recommendations

• We should continue with the general procedure from 2013 workshop: MCER spectrum multiplied by basin amplification factor. • Basin amplification factors developed from crustal earthquakes are not appropriate for subduction zone earthquakes (different from 2013 workshop)

Z2.5,REF = 1.0

Discussion and Recommendations

Z2.5,REF = 3.0

Figures from N. Marafi 2 13 New Consensus Approach for Development of BAFs

• Interface Subduction Hazard (based on recorded motions and M9 project) • BAF = 1 at T=0 sec • BAF = 2 at T > 2 sec

• Deep Intraslab Hazard • Use recorded ground motions from local and regional earthquakes (e.g. M6.8 Nisqually, M6.4 Vancouver Island)

• Shallow Crustal Hazard • Use basin factors from Campbell and Bozorgnia (2014) GMM

14 Example Spectra

• Increase from old to new spectra

• T=1 sec, 10%

• T=2 sec, 24%

• T=5 sec, 15%

15 Implementation of March Workshop Results

• Structural community concerned about immediate implementation • Telephone conference May 16 with geotechnical and structural peer reviewers, geotechnical consultants to discuss potential delay in implementation • Schedule of implementation • Director’s Rule 20-2018 • December 1, 2018 • All designs using site-specific ground motion procedures shall incorporate basin effects

16 On the horizon…

• NGA Subduction GMMs • Will they include basin terms? • Geotechnical and seismological community will need to evaluate applicability to the Seattle Basin

• How do we incorporate NGA Subduction and M9 results? • Had initial discussion during March 2018 workshop

• 2018 National Seismic Hazard Map update to include basin factors from 2013 SDCI/USGS workshop

17 QUESTIONS?

Susan Chang, Ph.D., P.E. [email protected] 206.386.9785 www.seattle.gov/sdci

Data courtesy of Richard Blakely (USGS)