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
My role with the USGS is to conduct research that makes use of the seismic hazard mapping results, and to provide the seismologist and geophysicists at the USGS with feedback that make their results even more useful. In this capacity, …
20 January 2010

2. Outline of Presentation
Description of ground motion maps in 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; 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 ) & SSD (Equation )
S1 = lesser of S1UHCR1 (Equation ) & S1D (Equation )
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”

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

24. Google “EERI NGA Seminar Presentations” for Video
or for just PowerPoint

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