Translating the 2009 Provisions into ASCE 7-10: Ground Motions Maps

1. Translating the 2009 Provisions into ASCE 7-10: Ground Motions Maps Nicolas Luco Research Structural Engineer National Seismic Hazard Mapping Project (Golden, CO) Project ‘07 Team (SDPRG) & ASCE 7 SSC 20 January 2010

2. Outline of Presentation • Description of ground motion maps in 2009 Provisions • Calculation of MCER ground motions from maps in 2009 Provisions • Maps of MCER ground motions (for Site Class B) in ASCE 7-10 • Risk Coefficient maps for Chapter 21 (“Site-Specific …”) of 2009 Provisions & ASCE 7-10 • USGS Web Application for ground motion values from 2009 Provisions & ASCE 7-10

5. Uniform-Hazard Ground Motion Maps • In 2009 Provisions … • Spectral response accelerations that have an exceedance probability of 2% in 50-years (a.k.a., a 2475-yr return period) • Denoted SSUH (for T=0.2s) & S1UH (for T=1s) • For Site Class B • In the direction of maximum horizontal response, so different than the USGS “geomean” hazard maps • In ASCE 7-10 … • Not included

7. Risk Coefficient Maps • In 2009 Provisions … • Derived using entire hazard curves (of exceedance probability vs. ground motion) from which uniform-hazard values are read • = Risk-Targeted GM / Uniform-Hazard GM • Denoted CRS (for T=0.2s) & CR1 (for T=1s) • <0.85 near New Madrid Seismic Zone, Charleston, & coastal Oregon; >1.15 near Sacramento; 0.85-1.15 almost everywhere else • In ASCE 7-10 … • Only included for use in site-specific ground motion hazard analysis (Ch. 21), “Method 1”

8. Research Needs after ‘09 Provisions

9. Deterministic Ground Motion Maps • In 2009 Provisions … • Considering characteristic earthquakes on all know active faults … • SSD (not SDS!) = max( 84th-%ile Sa(0.2s) ; 1.5g ) S1D (not SD1!) = max( 84th-%ile Sa(1.0s) ; 0.6g ) • For Site Class B • In the direction of maximum horizontal response, like uniform-hazard ground motions • In ASCE 7-10 … • Not included

10. MCER Ground Motions (Site Class B) • In 2009 Provisions … • SS = lesser of SSUHCRS (Equation 11.4-1) & SSD (Equation 11.4-2) • S1 = lesser of S1UHCR1 (Equation 11.4-3) & S1D (Equation 11.4-4) • Called “Risk-Targeted Maximum Considered Earthquake (MCER) Ground Motions” • In direction of maximum horizontal response, like SSUH & S1UH and SSD & S1D • In ASCE 7-10 (& 2012 IBC) … • Maps of SS & S1 are provided …

13. ASCE 7-10 MCER Ground Motion Maps Note: “Risk-Adjusted” terminology on MCER maps on 2009 Provisions CD has since been changed to “Risk-Targeted”, consistent with terminology in 2009 Provisions

15. Long-Period Transition Period (TL) Maps • In 2009 Provisions … • Same as in ASCE 7-05, except map sizes are smaller • In ASCE 7-10 … • Same as in ASCE 7-05 (& in 2009 Provisions)

17. Peak Ground Acceleration (PGA) Maps • In 2009 Provisions … • “MCE Geometric Mean PGA, %g, Site Class B” • Lesser of probabilistic (2% in 50-year) & deter-ministic PGA’s, like old MCE (not MCER) maps • For geometric mean spectral response acceleration across two horizontal comp-onents, also like old MCE (not MCER) maps • In ASCE 7-10 … • Same as in 2009 Provisions, except labeled “Maximum Considered Earthquake Geometric Mean (MCEG) PGA, %g, Site Class B”

19. http://earthquake.usgs.gov/designmaps

23. Site-Specific Ground Motions Method 1 Probabilistic (Risk-Targeted) GM = Uniform-Hazard (2% in 50-year) GM x Mapped Risk Coefficient

24. Google “EERI NGA Seminar Presentations” for Video or email nluco@usgs.gov for just PowerPoint

25. Summary (without TL & PGA Maps) Uniform-Hazard Maps Risk Coefficient Maps Deterministic Maps MCER Maps ─ In 2009 Provisions ─ In ASCE 7-10