& the nehrp design maps€¦ · mind that the latter were not computed via seismic hazard...

EERI Seminar on Next Generation Attenuation Models

New USGS Hazard Models & the NEHRP Design Maps

BSSC Colloquium: Seismic Design Technology for New Buildings

Nicolas Luco Research Structural Engineer, USGS (Golden, CO)

BSSC PUC Design Mapping Issue Team (“IT-11”) (Bachman, Crouse, Harris, Hooper, Kircher, Caldwell)


Map-Related Changes

“New USGS Hazard Models & the NEHRP Design Maps,” N. Luco (USGS) & IT-11 February 11, 2015

BSSC Colloquium: Seismic Design Technology for New Buildings – The 2015 NEHRP Recommended Seismic Provisions

1) New MCER, MCEG & Risk Coefficient maps for Guam, the Northern Mariana Islands, & American Samoa

2) Reference to underlying uniform-hazard and deterministic ground motion maps & values on USGS website

3) Updated maximum-response scale factors (Part 3)

4) Updated MCER, MCEG & Risk Coefficients maps for the conterminous US

5) “Site Specific Design Requirements and Parameters” (Kircher presentation)


1) Guam & Tutuila in ASCE 7-10




1) USGS Hazard Model for Guam




1) USGS Hazard Model for Tutuila




1) Hazard Model Design Maps




1) MCER Maps for 2015 Provisions

“Development of Corresponding Building Code ‘Design’ Maps,” N. Luco, USGS September 26, 2012

Workshop on Seismic Hazards of Guam/Northern Mariana Islands


1) MCER Maps for 2015 Provisions

“Development of Corresponding Building Code ‘Design’ Maps,” N. Luco, USGS October 2, 2012

Workshop on Seismic Hazards of American Samoa


1) 2015 Provisions Ch. 22 Commentary



… In comparing the MCER ground motion maps derived from these USGS hazard models to the geographically-constant values stipulated for Guam and American Samoa (Tutuila) in the 2010 and previous editions of ASCE/SEI 7, it is important to bear in mind that the latter were not computed via seismic hazard modeling. According to the commentary of the 1997 Provisions, the geographically-constant values were merely conversions, via rough approximations, from values on the 1994 Provisions maps that had been in use for nearly 20 years. As such, they did not take into account the 1993 Guam earthquake that was the largest ever recorded in the region and caused considerable damage, the 2009 earthquake near American Samoa that caused a tsunami, nor the 2008 “Next Generation Attenuation (NGA)” and another 2006 empirical ground motion prediction equation that have now been used for both Guam/NMI and American Samoa. …


Map-Related Changes









2) Ground Motions in 2009 Provisions




2) 2015 Provisions Ch. 22 Commentary



UNIFORM-HAZARD AND DETERMINISTIC GROUND MOTION MAPS

As alluded to above, implicit in the MCER ground motion, MCEG PGA, and risk coefficient maps provided are uniform-hazard (2%-in-50-years ground motion exceedance probability) and deterministic (84th percentile) ground motions. The 2009 Provisions provided maps of such uniform-hazard and deterministic ground motions, but ASCE/SEI 7-10 and the 2015 Provisions do not. Instead, uniform-hazard and deterministic ground motion maps consistent with this chapter are provided via a USGS website (http://earthquake.usgs.gov/hazards/designmaps/). Furthermore, values from these maps can be obtained via the ground motion software tool described above. …


2) USGS Design Maps Web Tool




Map-Related Changes









3) Max-Direction Factors in ASCE 7-10



21.2 RISK-TARGETED MAXIMUM CONSIDERED EARTHQUAKE (MCER) GROUND MOTION HAZARD ANALYSIS

… If the spectral response accelerations predicted by the attenuation relations do not represent the maximum response in the horizontal plane, then the response spectral accelerations computed from the hazard analysis shall be scaled by factors to increase the motions to the maximum response. If the attenuation relations predict the geometric mean or similar metric of the two horizontal components, then the scale factors shall be: 1.1 for periods less than or equal to 0.2 sec; 1.3 for a period of 1.0 sec, and, 1.5 for periods greater than or equal to 5.0 sec, unless it can be shown that other scale factors more closely represent the maximum response, in the horizontal plane, to the geometric mean of the horizontal components. Scale factors between these periods shall be obtained by linear interpolation. …


3) Updated Factors from PEER



Reference: Shahi & Baker, 2013. “NGA-West2 Models for Ground-Motion Directionality,” PEER Report 2013/10.

SARotD100 ÷ SARotD50 SARotD100 ÷ SAGMRotI50


3) Proposed ÷ ASCE 7-10 Factors



Conclusion: Incorporate updated factors into maps next cycle, concurrently with improvements to long-period ground motions.

0 1 2 3 4 5 6 7 8 9 10

0.8

0.9

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Period (s)

Rat

io

Proposed ÷ ASCE/SEI 7-10Proposed ÷ Shahi & Baker


3) Max-Direction Factors in ASCE 7-10



21.2 RISK-TARGETED MAXIMUM CONSIDERED EARTHQUAKE (MCER) GROUND MOTION HAZARD ANALYSIS

… If the spectral response accelerations predicted by the attenuation relations do not represent the maximum response in the horizontal plane, then the response spectral accelerations computed from the hazard analysis shall be scaled by factors to increase the motions to the maximum response. If the attenuation relations predict the geometric mean or similar metric of the two horizontal components, then the scale factors shall be: 1.1 for periods less than or equal to 0.2 sec; 1.3 for a period of 1.0 sec, and, 1.5 for periods greater than or equal to 5.0 sec, unless it can be shown that other scale factors more closely represent the maximum response, in the horizontal plane, to the geometric mean of the horizontal components. Scale factors between these periods shall be obtained by linear interpolation. …


Map-Related Changes









2) Fragility curve β = 0.8 β = 0.6, for consistency with the site-specific ground motion chapter (Ch. 21) of ASCE 7-10

4) Reasons for Updated Design Maps

1) 2014 USGS National Seismic Hazard Model (including NGA-West2, UCERF3, CEUS-SSC)



10-1

100

101

0

0.1

0.2

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0.5

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1

Spectral Acceleration (1.0 sec), a [g]

P [

Col

laps

e | S

A =

a ]

β = 0.8β = 0.6


4) USGS Hazard Model Updates



• See 10NCEE Paper 1698: Petersen et al, Updates for the 2014 National Seismic Hazard Maps: A summary of changes to seismic source and ground motion models, e.g., …

• Project Name Lead(s) Duration Sponsors Central & Eastern US Seismic Source Characterization for Nuclear Facilities (CEUS-SSC)

Consultants 2008-2011

US DOE, EPRI, US NRC

Uniform California Earthquake Rupture Forecast, Version 3 (UCERF3)

USGS, CGS, SCEC (WGCEP)

2010-2013

CEA

Next Generation Attenuation Relations for Western US, Version 2 (NGA-West2)

PEER 2010-2013

CEA, Caltrans, PG&E


4) Fragility β=0.8 β=0.6 Update



• For 2009 NEHRP Provisions MCER ground motions & site-specific ground motion chapter (Ch. 21), the BSSC Seismic Design Procedures Reassessment Group settled on β = 0.8

• For 2010 ASCE 7 Standard Ch. 21 (but not MCER maps), the Seismic Subcommittee (SSC) Ad-Hoc Ground Motion Committee updated to β = 0.6, based on …


4) Changes at 34 High-Risk Locations



Name Latitude Longitude Name Population

Los Angeles 34.05 -118.25Century City 34.05 -118.40Northridge 34.20 -118.55Long Beach 33.80 -118.20Irvine 33.65 -117.80 Orange 3,002,048Riverside 33.95 -117.40 Riverside 2,026,803San Bernardino 34.10 -117.30 San Bernardino 1,999,332San Luis Obispo 35.30 -120.65 San Luis Obispo 257,005San Diego 32.70 -117.15 San Diego 2,941,454Santa Barbara 34.45 -119.70 Santa Barbara 400,335Ventura 34.30 -119.30 Ventura 799,720

22,349,098 Population - 8 Counties 21,374,778Oakland 37.80 -122.25 Alameda 1,502,759Concord 37.95 -122.00 Contra Costa 955,810Monterey 36.60 -121.90 Monterey 421,333Sacramento 38.60 -121.50 Sacramento 1,233,449San Francisco 37.75 -122.40 San Francisco 776,733San Mateo 37.55 -122.30 San Mateo 741,444San Jose 37.35 -121.90 Santa Clara 1,802,328Santa Cruz 36.95 -122.05 Santa Cruz 275,359Vallejo 38.10 -122.25 Solano 423,473Santa Rosa 38.45 -122.70 Sonoma 489,290

14,108,451 Population - 10 Counties 8,621,978

Total Population - S. California

RegionCity and Location of Site County or Metropolitan Statistical Area

9,948,081Los AngelesN

orth

ern

Cal

iforn

iaSo

uthe

rn C

alifo

rnia

Total Population - N. California …


4) Changes at 34 High-Risk Locations



Name Latitude Longitude Name Population

RegionCity and Location of Site County or Metropolitan Statistical Area

Seattle 47.60 -122.30 King WA 1,826,732Tacoma 47.25 -122.45 Pierce WA 766,878Everett 48.00 -122.20 Snohomish WA 669,887Portland 45.50 -122.65 Portland Metro OR (3) 1,523,690

10,096,556 Population - 6 Counties 4,787,187Salt Lake City 40.75 -111.90 Salt Lake UT 978,701Boise 43.60 -116.20 Ada/Canyon ID (2) 532,337Reno 39.55 -119.80 Washoe NV 396,428Las Vegas 36.20 -115.15 Clarke NV 1,777,539

6,512,057 Population - 5 Counties 3,685,005St. Louis 38.60 -90.20 St. Louis MSA (16) 2,786,728Memphis 35.15 -90.05 Memphis MSA (8) 1,269,108Charleston 32.80 -79.95 Charleston MSA (3) 603,178Chicago 41.85 -87.65 Chicago MSA (7) 9,505,748New York 40.75 -74.00 New York MSA (23) 18,747,320

48,340,918 Population - 57 Counties 32,912,082

Total Population - ID/UT/NV

Total Population - MO/TN/SC/IL/NY

CEU

SO

ther

WU

SPa

cific

N

orth

wes

t

Total Population - OR and WA

…


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 1718 19 20 21 22 23 24 25 2627 28 29 30 31 32 33 340.6

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Southern California Northern California PacNW IMW CEUS

SS (MCER)

S1 (MCER)

PGA (MCEG)

4) Changes in MCER & MCEG Values



San

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Las

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Irvin

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San

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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 1718 19 20 21 22 23 24 25 2627 28 29 30 31 32 33 340.6

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und

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ion

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ASCE 7-10 ÷ ASCE 7-05 , SS

ASCE 7-10 ÷ ASCE 7-05 , S1

ASCE 7-05 ÷ ASCE 7-98 , SS

ASCE 7-05 ÷ ASCE 7-98 , S1

4) Previous Changes in MCE(R) Values




4) Underlying Values



• As laid out in the 2009 NEHRP Provisions (& Ch. 21) … …


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 1718 19 20 21 22 23 24 25 2627 28 29 30 31 32 33 340.6

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SSUHS1UH"PGAUH"

4) Changes in USGS Uniform-Hazard Values



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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 1718 19 20 21 22 23 24 25 2627 28 29 30 31 32 33 340.6

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4) Changes in Risk Coefficients




4) Changes in Deterministic Values



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 1718 19 20 21 22 23 24 25 2627 28 29 30 31 32 33 340.6

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SSDS1D"PGAD"


• UCERF3 includes multi-fault ruptures (M8+), in part to remove UCERF2 overprediction of M6.5-7 earthquakes.

4) Deterministic Earthquakes




• UCERF3 also includes low-activity-rate faults, e.g., …





From ASCE 7-10 site-specific ground motion chapter (Ch. 21):




• For 2015 NEHRP Provisions, characteristic earthquakes from UCERF2 (& ASCE 7-10) have been updated and used in lieu of UCERF3 multi-fault ruptures, and …

• “Active” faults have been defined as those with Holocene (last ~12K years) displacement/slip, or with slip rate > 0.1 mm/year. All other faults have been excluded.


4) Changes in Site Coefficients



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 1718 19 20 21 22 23 24 25 2627 28 29 30 31 32 33 340.6

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FaFvFPGA


4) Changes in Seismic Design Categories



SDC BC (Red) & CB (Blue) for Site Class D, Risk Category II


4) Conclusions



• 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.

• Some of the >20% changes are due to a compounding of the USGS hazard model updates with the fragility β update.

• Alone, the fragility β update typically changes the design maps by less than +/-10%.

• Seismic Design Categories change in relatively small areas, mostly at low-risk locations.


4) Future Work – Project ‘17



• BSSC/FEMA-USGS Collaboration; Planning committee chaired by Ron Hamburger; Potential topics include …

• Ground motions for spectral periods other than 0.2s & 1.0s, and Site Classes other than B, with due consideration of sedimentary basin effects

• Utilization of physics-based simulations of ground motions (e.g., CyberShake from SCEC, USGS Urban Hazard Maps for Seattle & Salt Lake City)

• Reassessment of deterministic ground motions

• Consideration of hazard modeling uncertainty when updating design maps (e.g., for NGA-East)


Map-Related Changes








& the nehrp design maps€¦ · mind that the latter were not computed via seismic hazard...

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