Updates to Maps for the 2015 NEHRP Recommended

Updates to Maps for the 2015 NEHRP Recommended Seismic Provisions Buildingon Seismic Council (BSSC) Webinar. Models EERI Seminar Next. Safety Generation Attenuation Nicolas Luco Research Structural Engineer, USGS (Golden, CO) BSSC PUC Design Mapping Issue Team (“IT-11”) (Bachman, Crouse, Harris, Hooper, Kircher, Caldwell)

ASCE/SEI 7 -10 Ground-Motion Maps • Risk Target = 1% Probability of Collapse in 50 years • Maximum-direction spectral response accelerations • Deterministic caps FIGURE 22 -1/2 RISK-TARGETED MAXIMUM CONSIDERED EARTHQUAKE (MCER) … SPECTRAL RESPONSE ACCELERATION …, SITE CLASS B Building Seismic Safety Council (BSSC) Webinar EERI Seminar on Next Generation Attenuation Models “New USGS Seismic Hazard Models & their Impacts on ASCE/SEI 7 -16, ” N. Luco (USGS) et al February 16, 2016

ASCE/SEI 7 -10 Ground-Motion Maps • Uniform-Hazard, 2% Probability of Exceedance in 50 years • Geometric mean PGA across two horizontal components • Deterministic caps FIGURE 22 -7 MAXIMUM CONSIDERED EARTHQUAKE GEOMETRIC MEAN (MCEG) PGA …, SITE CLASS B … Building Seismic Safety Council (BSSC) Webinar EERI Seminar on Next Generation Attenuation Models “Updates to Maps for the 2015 NEHRP Recommended Seismic Provisions, ” N. Luco (USGS) et al March 22, 2016

Outline of this presentation • Updates to MCER (& MCEG) maps for conterminous US for 2015 NEHRP Provisions • Comparisons with values from ASCE 7 -10 • Comparisons with previous editions of ASCE 7 -05 and ASCE 7 -02/7 -98 • Summary • Updated USGS Seismic Design Maps web tool • Status of adoption into ASCE 7 -16, IBC, IRC Building Seismic Safety Council (BSSC) Webinar EERI Seminar on Next Generation Attenuation Models “Updates to Maps for the 2015 NEHRP Recommended Seismic Provisions, ” N. Luco (USGS) et al March 22, 2016

Reasons for Updated Design Maps 1) 2014 USGS National Seismic Hazard Model (including NGAWest 2, UCERF 3, CEUS-SSC) 2) Fragility curve b = 0. 8 b = 0. 6, for consistency with the sitespecific ground motion chapter (Ch. 21) of ASCE 7 -10 Building Seismic Safety Council (BSSC) Webinar EERI Seminar on Next Generation Attenuation Models “Updates to Maps for the 2015 NEHRP Recommended Seismic Provisions, ” N. Luco (USGS) et al March 22, 2016

USGS Hazard Model Updates • Project Name Lead(s) Duration Sponsors Central & Eastern US Seismic Source Characterization for Nuclear Facilities (CEUS-SSC) Consultants 20082011 US DOE, EPRI, US NRC Uniform California Earthquake Rupture Forecast, Version 3 (UCERF 3) USGS, CGS, SCEC (WGCEP) 20102013 CEA PEER 20102013 CEA, Caltrans, PG&E Next Generation Attenuation Relations for Western US, Version 2 (NGA-West 2) • Others listed in Chapter 22 Commentary and explained in December 2015 Special Issue of Earthquake Spectra journal Building Seismic Safety Council (BSSC) Webinar EERI Seminar on Next Generation Attenuation Models “Updates to Maps for the 2015 NEHRP Recommended Seismic Provisions, ” N. Luco (USGS) et al March 22, 2016

Fragility b=0. 8 b=0. 6 Update • For 2009 NEHRP Provisions MCER ground motions & sitespecific ground motion chapter (Ch. 21), the BSSC Seismic Design Procedures Reassessment Group settled on b = 0. 8 • For 2010 ASCE 7 Standard Ch. 21 (but not MCER maps), the Seismic Subcommittee (SSC) Ad-Hoc Ground Motion Committee updated to b = 0. 6, based on … Building Seismic Safety Council (BSSC) Webinar EERI Seminar on Next Generation Attenuation Models “Updates to Maps for the 2015 NEHRP Recommended Seismic Provisions, ” N. Luco (USGS) et al March 22, 2016

Changes at 34 High-Risk Locations … Building Seismic Safety Council (BSSC) Webinar EERI Seminar on Next Generation Attenuation Models “Updates to Maps for the 2015 NEHRP Recommended Seismic Provisions, ” N. Luco (USGS) et al March 22, 2016

Changes at 34 High-Risk Locations … Building Seismic Safety Council (BSSC) Webinar EERI Seminar on Next Generation Attenuation Models “Updates to Maps for the 2015 NEHRP Recommended Seismic Provisions, ” N. Luco (USGS) et al March 22, 2016

34 City Locations from 2009 Provisions Building Seismic Safety Council (BSSC) Webinar EERI Seminar on Next Generation Attenuation Models “Updates to Maps for the 2015 NEHRP Recommended Seismic Provisions, ” N. Luco (USGS) et al March 22, 2016

Charleston Las Vegas San Diego Santa Barbara Irvine Changes in MCER & MCEG Values Building Seismic Safety Council (BSSC) Webinar EERI Seminar on Next Generation Attenuation Models “Updates to Maps for the 2015 NEHRP Recommended Seismic Provisions, ” N. Luco (USGS) et al March 22, 2016

Underlying Components of SS and S 1 • As laid out in the 2009 NEHRP Provisions (& Ch. 21) … … SS = min( CRS SSUH, SSD ) S 1 = min( CR 1 S 1 UH, S 1 D ) Building Seismic Safety Council (BSSC) Webinar EERI Seminar on Next Generation Attenuation Models “Updates to Maps for the 2015 NEHRP Recommended Seismic Provisions, ” N. Luco (USGS) et al March 22, 2016

Las Vegas San Diego Santa Barbara Changes in USGS Uniform-Hazard Values Building Seismic Safety Council (BSSC) Webinar EERI Seminar on Next Generation Attenuation Models “Updates to Maps for the 2015 NEHRP Recommended Seismic Provisions, ” N. Luco (USGS) et al March 22, 2016

Changes at Las Vegas Location • In ASCE 7 -10 maps, rate of earthquakes on Eglington fault is ~1/14, 000 yrs. • Based on recent publications (references in de. Polo et al, 2013), … • Nevada Bureau of Mines & Geology recommended, in effect, a rate of ~1/600 yrs. • Through additional communication with USGS, all agreed on ~1/2, 100 yrs. Building Seismic Safety Council (BSSC) Webinar EERI Seminar on Next Generation Attenuation Models “Updates to Maps for the 2015 NEHRP Recommended Seismic Provisions, ” N. Luco (USGS) et al March 22, 2016

Changes at Santa Barbara Location Building Seismic Safety Council (BSSC) Webinar EERI Seminar on Next Generation Attenuation Models “Updates to Maps for the 2015 NEHRP Recommended Seismic Provisions, ” N. Luco (USGS) et al March 22, 2016

Changes at Santa Barbara Location • ASCE 7 -10 maps are based on NGA-West 1 for Western on UCERF 2 in California. U. S. crustal earthquakes. • UCERF 3 includes more multi-fault earthquakes (like • NGA-West 2 includes recent data from 2009 M 6. 3 L’Aquila, 2011 M 7. 2 El Mayor 2008 M 7. 9 Wenchuan & 5 Cucapah), in part to remove other earthquakes on dipping UCERF 2 over-prediction of faults, as well as 130, 000 M 6. 5 -7 earthquakes. ground motion simulations. • This, in effect, lowers rate of earthquakes that dominate • The effect was to decrease best estimates of ground hazard in Santa Barbara. motions over reverse faults near Santa Barbara. Building Seismic Safety Council (BSSC) Webinar EERI Seminar on Next Generation Attenuation Models “Updates to Maps for the 2015 NEHRP Recommended Seismic Provisions, ” N. Luco (USGS) et al March 22, 2016

Commentary on Additional Changes Building Seismic Safety Council (BSSC) Webinar EERI Seminar on Next Generation Attenuation Models “Updates to Maps for the 2015 NEHRP Recommended Seismic Provisions, ” N. Luco (USGS) et al March 22, 2016

Changes in Risk Coefficients Building Seismic Safety Council (BSSC) Webinar EERI Seminar on Next Generation Attenuation Models “Updates to Maps for the 2015 NEHRP Recommended Seismic Provisions, ” N. Luco (USGS) et al March 22, 2016

Changes in Deterministic Values Building Seismic Safety Council (BSSC) Webinar EERI Seminar on Next Generation Attenuation Models “Updates to Maps for the 2015 NEHRP Recommended Seismic Provisions, ” N. Luco (USGS) et al March 22, 2016

Deterministic Earthquakes • UCERF 3 includes multi-fault ruptures (M 8+), in part to remove UCERF 2 overprediction of M 6. 5 -7 earthquakes. Building Seismic Safety Council (BSSC) Webinar EERI Seminar on Next Generation Attenuation Models “Updates to Maps for the 2015 NEHRP Recommended Seismic Provisions, ” N. Luco (USGS) et al March 22, 2016

Deterministic Earthquakes • UCERF 3 also includes low-activity-rate faults, e. g. , … Building Seismic Safety Council (BSSC) Webinar EERI Seminar on Next Generation Attenuation Models “Updates to Maps for the 2015 NEHRP Recommended Seismic Provisions, ” N. Luco (USGS) et al March 22, 2016

Deterministic Earthquakes From ASCE 7 -10 site-specific • For 2015 NEHRP Provisions, ground motion chapter (Ch. 21): characteristic earthquakes from UCERF 2 (& ASCE 7 -10) have been updated and used in lieu of UCERF 3 multi-fault ruptures, and … • “Active” faults have been defined as those with Holocene (last ~12 K years) displacement/slip, or with slip rate > 0. 1 mm/year. All other faults have been excluded. Building Seismic Safety Council (BSSC) Webinar EERI Seminar on Next Generation Attenuation Models “Updates to Maps for the 2015 NEHRP Recommended Seismic Provisions, ” N. Luco (USGS) et al March 22, 2016

Previous Changes in MCE(R) Values Building Seismic Safety Council (BSSC) Webinar EERI Seminar on Next Generation Attenuation Models “Updates to Maps for the 2015 NEHRP Recommended Seismic Provisions, ” N. Luco (USGS) et al March 22, 2016

Precision vs. Uncertainty

Comment from ASCE 7 -16 Main Committee “These maps continue to change both up and down each cycle which is causing a lack of confidence in them by the design community. The maps need to stabilize for a few cycles for the users of the standard to develop confidence in them. I would recommend that we stay with the current maps. ” Three other Main Committee members made similar (but longer) comments. Building Seismic Safety Council (BSSC) Webinar EERI Seminar on Next Generation Attenuation Models “Updates to Maps for the 2015 NEHRP Recommended Seismic Provisions, ” N. Luco (USGS) et al March 22, 2016

Precision vs. Uncertainty

Summary • Conterminous US updates include (i) 2014 USGS NSHM, (ii) b=0. 6, and (iii) definition of “active faults” for deterministic ground motions. • Amongst 34 high-risk locations, 9/10 -ths of design map changes are within +/-20%, 2/3 -rds are within +/-10%. • Most of the >20% changes are due to significant USGS hazard model updates. • Seismic Design Categories change in relatively small areas, mostly at relatively low-risk locations. • Uncertainty in design ground motions desired for perspective. Building Seismic Safety Council (BSSC) Webinar EERI Seminar on Next Generation Attenuation Models “Updates to Maps for the 2015 NEHRP Recommended Seismic Provisions, ” N. Luco (USGS) et al March 22, 2016

Deeper Explanations of Changes Building Seismic Safety Council (BSSC) Webinar EERI Seminar on Next Generation Attenuation Models “Updates to Maps for the 2015 NEHRP Recommended Seismic Provisions, ” N. Luco (USGS) et al March 22, 2016

Updated Design Maps Web Tool http: //earthquake. usgs. gov/designmaps/beta/us/ Building Seismic Safety Council (BSSC) Webinar EERI Seminar on Next Generation Attenuation Models “Updates to Maps for the 2015 NEHRP Recommended Seismic Provisions, ” N. Luco (USGS) et al March 22, 2016

Updated Design Maps Web Tool Building Seismic Safety Council (BSSC) Webinar EERI Seminar on Next Generation Attenuation Models “Updates to Maps for the 2015 NEHRP Recommended Seismic Provisions, ” N. Luco (USGS) et al March 22, 2016

Updated Design Maps Web Tool Building Seismic Safety Council (BSSC) Webinar EERI Seminar on Next Generation Attenuation Models “Updates to Maps for the 2015 NEHRP Recommended Seismic Provisions, ” N. Luco (USGS) et al March 22, 2016

Updated Design Maps Web Tool Building Seismic Safety Council (BSSC) Webinar EERI Seminar on Next Generation Attenuation Models “Updates to Maps for the 2015 NEHRP Recommended Seismic Provisions, ” N. Luco (USGS) et al March 22, 2016

Updated Design Maps Web Tool Building Seismic Safety Council (BSSC) Webinar EERI Seminar on Next Generation Attenuation Models “Updates to Maps for the 2015 NEHRP Recommended Seismic Provisions, ” N. Luco (USGS) et al March 22, 2016

Updated Design Maps Web Tool Building Seismic Safety Council (BSSC) Webinar EERI Seminar on Next Generation Attenuation Models “Updates to Maps for the 2015 NEHRP Recommended Seismic Provisions, ” N. Luco (USGS) et al March 22, 2016

Updated Design Maps Web Tool Building Seismic Safety Council (BSSC) Webinar EERI Seminar on Next Generation Attenuation Models “Updates to Maps for the 2015 NEHRP Recommended Seismic Provisions, ” N. Luco (USGS) et al March 22, 2016

Status of Adoption for ASCE 7 -16, etc. • After initially being rejected, the updated maps are one editorial step away from adoption into ASCE 7 -16 • The updated maps have been proposed for the International Building Code (IBC) • An alternate IBC proposal would simply reference ASCE 7 -16 • Corresponding Seismic Design Category maps have been proposed for the International Residential Code Building Seismic Safety Council (BSSC) Webinar EERI Seminar on Next Generation Attenuation Models “Updates to Maps for the 2015 NEHRP Recommended Seismic Provisions, ” N. Luco (USGS) et al March 22, 2016