Multi-Period & Multi -Vs30 Design Ground Motions for 2020 ...

Multi-Period & Multi-Vs30 Design Ground Motions for 2020 NEHRP Seismic Provisions (ASCE 7-22) based on the 1998/2001 Hawaii Hazard Model

Sanaz RezaeianResearch Structural EngineerUSGS, Golden, CO

September 18, 2019University of Hawaii at Manoa, Honolulu, HI

NSHMP Update of the Hawaii Seismic Hazard Model Workshop

(Figure 22-5, 2020 NEHRP, Default Site Class)


“Hawaii Multi-Period & Multi-Vs30 Design Ground Motions for 2020 NEHRP, based on 1998/2001 Hazard Model” Sanaz Rezaeian Sept 18, 2019

Outline

Ø “Design” ground motions: SS & S1 in 2015 NEHRP

Ø Updates to SS & S1 calculations for 2020 NEHRP (based on 1998/2001 hazard model)

Ø Deriving Multi-Period Response Spectrum (MPRS), SMS & SM1 for 2020 NEHRP

Discussion: future design needs from the new Hawaii hazard model? - Directionality of GMMs? - Are GMMs available for all periods & site classes? - Deterministic caps (deaggs)?

SS Map in 2015 NEHRP(BC Site Class)

SMS Map for 2020 NEHRP(Default Site Class)



“Design” Ground Motions

Site-Specific Ground Motion Procedures of

Ch21…

USGS Seismic Hazard Model

Risk-Targeted Maximum Considered Earthquake (MCER) Ground Motion Maps

ASCE 7 Standard

Included:maxdir, RTGM, DetCaps

Site Amplification CoefficientsSimplified Spectral Shape

In the past:PGA, 0.2s, 1.0s

BC site class

BSSC PUC“Hazard” Curves

Next Generation: 22 Periods & 8 Site Classes

2020 NEHRP(Project ‘17 Recommendation)

Hawaii: 1998 Model2001 Klein et al., BSSA

modified



1. Maximum Horizontal Direction Ground Motion

Typical GMMs are in the direction of Geometric Mean, GMRotI50, or RotD50

-0.5 -0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4 0.5

-0.5

-0.4

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

0.4

0.5

Acc. in FNdirection (g)

Acc.

in FP

direc

tion (

g)

X

Y

Sa(X)

Sa(Y)

Sa(Max)

“Design” Ground Motions (2015 NEHRP and prior):

Hazard curves for BC reference site at 0.2s & 1.0s are used to calculate SS & S1 (starting in 2009NEHRP/ASCE7-10):

SS maxdir factor: 1.1S1 maxdir factor: 1.3*PGA: geomean

Hawaii GMMs were assumed to be maxdirection à no factors in 2009NEHRP/ASCE7-10 & 2015NEHRP/ASCE7-16




2. Risk-Targeted Ground Motions (defined by Project ‘07)

Same “2500-yr” GMs First iteration

+

Hazard Curve Fragility

GM that gives 1% probability of building collapse in 50 years

“Probabilistic GM”

*PGA: Uniform Hazard (Not Risk-Targeted)






2. Risk-Targeted Ground Motions

3. Deterministic Cap

MCER = min ( Prob. , Det. )

(the largest 84th percentile acceleration calculated for the characteristic earthquakes on all known active faults within the region, floored at a deterministic lower limit)

Ss Map S1 Map

(Figure from 2015 NEHRP)

Two Deterministic Zone Boundaries

Deterministic Lower Limits1.5g & 0.6g








4. Site Amplification Coefficients (updated in 2015NEHRP/ASCE7-16)

SMS = Fa x SS

SM1 = Fv x S1

Table 11.4-2 Long-Period Site Coefficient, Fv

Table 11.4-1 Short-Period Site Coefficient, Fa








4. Site Amplification Coefficients

5. Simplified Spectral Shape

Acceleration Domain

Velocity Domain

Displacement Domain

SDS = 2/3 x SMS = 2/3 x Fa x Ss

TS = SD1/SDS

SD1 = 2/3 x SM1 = 2/3 x Fv x S1

Site-Specific Multi-Period Response Spectrum

Figure 11.4-1, ASCE 7-05, ASCE 7-10 and ASCE 7-16 with annotation (from Kircher)





Updates to 2020 NEHRP Procedures:

Updated site-specific procedures of Ch21

1. Updating the max-direction factors2. No change to risk-targeted calcs3. Modifying deterministic caps based on deagg. of probabilistic hazard4&5. Using multi-period multi-Vs30 response spectrum (MPRS)

MPRS issue directly influenced the 2018 update of USGS NSHM (selected GMMs applicable for all periods and site classes). Models for OCONUS (including Hawaii) do not have this capability à MPRS Study

Summary of BSSC Project ‘17 Recommendations:

A joint USGS-BSSC effort to develop consensus among practicing engineers and earth science communities engaged in formulating the rules by which next-generation seismic design value maps will be developed. (2020 NEHRP, ASCE 7-22, 2024 IBC)



1. Update of Max Direction Factors (2020 NEHRP):

Period sec New Factors0.0 1.200

0.01 1.2000.02 1.2000.03 1.2000.05 1.200

0.075 1.2000.1 1.200

0.15 1.2000.2 1.200

0.25 1.2030.3 1.2060.4 1.2130.5 1.219

0.75 1.2341.0 1.2501.5 1.2532.0 1.2563.0 1.2614.0 1.2675.0 1.2727.5 1.286

10.0 1.300

Project ‘17: Update maximum-direction factors based on Shahi & Baker (NGA-West2) study

ASCE 7-10 & 7-16

Shahi & Baker for 2020 NEHRP/ASCE 7-22 Hawaii:GMMs were assumed to be maxdirection in 1998, so no adjustments are made for 2020 NEHRP.

*PGA: with that assumption, PGA is technically maxdir and should be divided by 1.2 to arrive at geomean, however, we decided not to do this to avoid decreasing PGA by too much until an updated hazard model is available.

Old Factors:*PGA: geomean

Ss : 1.1

S1 : 1.3

Generic fragility curve equation:

𝑷[𝑪𝒐𝒍𝒍𝒂𝒑𝒔𝒆|𝑺𝑨 = 𝒂] =

𝜱0𝐥𝐧𝒂 − (𝐥𝐧𝑹𝑻𝑮𝑴+ 𝟏. 𝟐𝟖 × 𝟎. 𝟔)

𝟎. 𝟔C

where

𝜱[∙] ≡ 𝐍𝐨𝐫𝐦𝐚𝐥/𝐆𝐚𝐮𝐬𝐬𝐢𝐚𝐧𝐂𝐃𝐅



2. Update of Risk-Targeted Calculations (2020 NEHRP):

Project ‘17: No change to risk-targeted calculations of 2015NEHRP/ASCE7-16

Hawaii-Specific Updates:Risk-targeted ground motions were outdated. We used the 1998 hazard curves to recalculate probabilistic GMs.1. Changed β from 0.8 to 0.62. Updated interpolation of hazard curves (linear to log)3. Truncated hazard curves (10-4)

11

0.8 in ASCE 7-10 site-specific procedures



2. Update of Risk-Targeted Calculations (2020 NEHRP):

Project ‘17: No change to risk-targeted calculations of 2015NEHRP/ASCE7-16

Hawaii-Specific Updates:Risk-targeted ground motions were outdated. We used the 1998 hazard curves to recalculate probabilistic GMs.1. Changed β from 0.8 to 0.62. Updated interpolation of hazard curves (linear to log)3. Truncated hazard curves

Det-Prob mix

Det-Prob mix

Big Island

MauiO’ahu

Prob. SSP (g) ASCE 7-16 Prob. S1P (g) ASCE 7-16

Prob

. SSP

(g) 2

020

NEH

RP

Prob

. S1P

(g) 2

020

NEH

RP

Kaua’iDeterministically capped

Deterministically capped

Prob Prob



3. Update of Deterministic Caps (2020 NEHRP):

Project ‘17: Modify deterministic caps based on deaggregation of probabilistic hazard

21.2.2 Deterministic (MCER) Ground Motions.

The deterministic spectral response acceleration at each period shall be calculated as an 84th-percentile 5% damped spectral response acceleration in the direction of maximum horizontal response computed at that period. The largest such acceleration calculated for the characteristic scenario earthquakes on all knownactive faults within the region shall be used. The scenario earthquakes shall be determined from deaggregation for the probabilistic spectral response acceleration at each period. Scenario earthquakes contributing less than 10% of the largest contributor at each period shall be ignored.

Hawaii:Cannot update to this new definition until new hazard model and deagg tools are available. (previous: two det zone boundaries in HI)

Hawaii-Specific Updates (minor):Fixed some discrepancies:1. 84th percentile factor updated to 1.8 (was 1.5 in older codes)2. As a consequence of above, deterministic switches to probabilistic for some sites



Summary of Updates to SS & S1 in Hawaii (2020 NEHRP):

Determinist increasing (~20%)

Det. switching to prob.

or increasing

Probabilistic updates (beta & interpolation)

SS (g) S1 (g)

Big Island

Maui

O’ahuKaua’i Determinist

increasing (~20%)


or increasingProbabilistic updates

(beta & interpolation)

Big Island

Maui

O’ahuKaua’i



2% in 50 Years Probability of Exceedance 0.2s Ground Motion (g)

Site Lat Lon 1998/2001 Approx. Changes

Hilo 19.7 -155.06 1.8 124%

Kona 19.66 -156 2.43 57%

Kahului 20.9 -156.5 0.97 83%

Honolulu 21.3 -157.86 0.61 94%

Lihue 21.96 -159.36 0.25 19%

Possible Future Changes (beyond 2020 NEHRP)Probabilistic values from prelim model:

Will likely be deterministically capped!

Will likely increase but uncertain by how much!

Max direction will likely increase all values by ~20%


Above table for softer soils, will likely change less for BCDeterminist increasing (~20%)


or increasing

Probabilistic updates (beta & interpolation)

SS (g)

Big Island

Maui

O’ahuKaua’i




No change to the USGS hazard models or deterministic calculations

1. No change to max direction

2. Updated the risk-targeted ground motion calculations (decreases down to about -15%):a) Changed β from 0.8 to 0.6b) Interpolation of hazard curves from linear to logc) Truncated hazard curves

3. Updated to the deterministic ground motions (increases up to about 20%)a) 84th percentile factor updated (1.5 to 1.8)b) As a consequence, deterministic switches to probabilistic for some sites



4&5. Multi-Period Response Spectrum (MPRS) Update:

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

2.2

2.4

2.6

0.1 1.0 10.0

Res

pons

e Sp

ectra

l Acc

eler

tatio

n (g

)

Period (seconds)

MCEr Multi-Period Response Spectrum - Site Class BCMCEr Multi-Period Response Spectrum - Site Class CDesign Multi-Period Response Spectrum - Site Class CELF Design Spectrum (Cs x R/Ie) - ASCE 7-16 w/o SSAF

ELF Design SpectrumSs = 1.5Fa = 1.2SMS = Fa x Ss = 1.8SDS = 2/3 x SMS = 1.2

S1 = 0.6Fv = 1.4SM1 = Fv x S1 = 0.84SD1 = 2/3 x SM1 = 0.56

M7.0 earthquake (at RX = 6.8 km) – Site Class C

Kircher & Associates, 2015, prepared for BSSC

Background and Root Cause of the Problem (ASCE 7-10): Long period ground motions underestimated for large magnitude earthquakes on soft site classes

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

2.2

2.4

2.6

0.1 1.0 10.0

Res

pons

e Sp

ectra

l Acc

eler

tatio

n (g

)

Period (seconds)

MCEr Multi-Period Response Spectrum - Site Class BCMCEr Multi-Period Response Spectrum - Site Class DDesign Multi-Period Response Spectrum - Site Class DELF Design Spectrum (Cs x R/Ie) - ASCE 7-16 w/o SSAF


S1 = 0.72Fv = 1.7SM1 = Fv x S1 = 1.22SD1 = 2/3 x SM1 = 0.82

M8.0 earthquake (at RX = 9.9 km) – Site Class D

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

2.2

2.4

2.6

0.1 1.0 10.0

Res

pons

e Sp

ectra

l Acc

eler

tatio

n (g

)

Period (seconds)

MCEr Multi-Period Response Spectrum - Site Class BCMCEr Multi-Period Response Spectrum - Site Class EDesign Multi-Period Response Spectrum - Site Class EELF Design Spectrum (Cs x R/Ie) - ASCE 7-16 w/o SSAF


S1 = 0.72Fv = 2.0SM1 = Fv x S1 = 1.44SD1 = 2/3 x SM1 = 0.96

M8.0 earthquake (at RX = 9.9 km) – Site Class E

Period 5%-Damped Response Spectral Acceleration or PGA by Site Class (g)T (s) A B BC C CD D DE E0.00

0.0100.0200.0300.0500.0750.100.150.20 1.5000.250.300.400.500.751.0 0.6001.52.03.04.05.07.510

PGA G 0.500



4&5. Multi-Period Response Spectrum (MPRS) Update:

Background and Root Cause of the Problem (ASCE 7-10): Long period ground motions underestimated for large magnitude earthquakes on soft site classes

Interim ASCE 7-16 Solution:Site-specific ground motion procedures required for most sitesOr use conservative values of site amplification coefficients

Long-Term Solution (for ASCE 7-22):Calculate spectrum directly from hazard curves at many periods (22) and site classes (8)

SS

S1

PGA

Problem: for OCONUS (including Hawaii) our hazard models do not have this capability yet



4&5. Multi-Period Response Spectrum (MPRS) Study:

MPRS Study Developed Generic Shapes:“Procedures for Developing Multi-Period Response Spectra of Non-Conterminous United States Sites.” FEMA-funded ATC-report(Submitted to BSSC PUC, June 2019)

Response Spectrum Shape Parameters (RSSPs), developed based on WUS data, functions of (SS, S1, TL)

Figure B-17. Plots of probabilistic response spectrum shape parameters (RSSPs) by site class for Table B-17. GTL12S3R2.

SS = 1 Probabilistic RSSP = f(site class, TL, SS, S1)• Five 𝑇" regions• Five ground motion levels (𝑆$)• Five spectral response ratio levels (𝑅 = 𝑆$/𝑆()

à15 Deterministic RSSPsDeterministic RSSP = f(site class, SS, S1)

à41 Probabilistic RSSPs




Long Period Transition period (Ch22), TL:

Hilo: TL = 12secHonolulu: TL = 4sec




Validation of the Model:

0.00

0.25

0.50

0.75

1.00

1.25

1.50

1.75

2.00

0.01 0.10 1.00 10.00

Res

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n (g

)

Response Period (seconds)

B-DRBC-DRC-DRCD-DRD-DRDE-DRB-22BC-22C-22CD-22D-22DE-22

Irvine, CA

Solid Lines: Predicted values from Ss & S1Dashed Lines: Exact values calculated for 2020 NEHRP

0.00

0.25

0.50

0.75

1.00

1.25

1.50

1.75

2.00

2.25

2.50

2.75

3.00

0.01 0.10 1.00 10.00

Res

pons

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eler

atio

n (g

)


B-DRBC-DRC-DRCD-DRD-DRDE-DRB-22BC-22C-22CD-22D-22DE-22

San Mateo, CA

Period 5%-Damped Response Spectral Acceleration (g)T (s) A B BC C CD D DE E Default0.00 0.700 0.782 0.910 0.998 1.015 0.947 0.843 0.791 1.0150.01 0.704 0.787 0.914 1.003 1.021 0.954 0.850 0.798 1.0210.02 0.732 0.815 0.941 1.019 1.028 0.956 0.846 0.787 1.0280.03 0.864 0.945 1.056 1.099 1.074 0.970 0.834 0.764 1.0990.05 1.240 1.327 1.380 1.362 1.257 1.087 0.912 0.830 1.3620.08 1.591 1.715 1.777 1.726 1.559 1.340 1.140 1.056 1.7260.10 1.690 1.865 2.012 1.989 1.811 1.572 1.358 1.274 1.9890.15 1.665 1.887 2.243 2.310 2.146 1.877 1.624 1.524 2.3100.20 1.490 1.718 2.165 2.459 2.349 2.072 1.791 1.682 2.4590.25 1.319 1.536 2.003 2.459 2.473 2.221 1.941 1.838 2.4730.30 1.183 1.380 1.845 2.346 2.538 2.339 2.077 1.982 2.5380.40 0.994 1.160 1.595 2.111 2.498 2.398 2.180 2.097 2.4980.50 0.860 1.002 1.406 1.908 2.347 2.369 2.195 2.141 2.3690.75 0.657 0.744 1.066 1.484 1.921 2.063 2.010 2.019 2.0631.0 0.521 0.576 0.837 1.189 1.594 1.827 1.916 1.993 1.8271.5 0.358 0.386 0.553 0.805 1.117 1.405 1.687 1.916 1.4052.0 0.280 0.300 0.407 0.592 0.840 1.133 1.517 1.872 1.1333.0 0.204 0.219 0.277 0.404 0.584 0.811 1.132 1.436 0.8114.0 0.164 0.173 0.210 0.303 0.432 0.593 0.819 1.032 0.5935.0 0.139 0.146 0.169 0.240 0.336 0.454 0.616 0.768 0.4547.5 0.090 0.093 0.102 0.138 0.186 0.243 0.318 0.388 0.24310 0.062 0.064 0.069 0.090 0.117 0.148 0.187 0.222 0.148




Example Application:

Derived probabilistic MPRS: • Select generic RSSP

TL=12s, S5, R4 à “GTL12S5R4” (Table B-23)

• Scale to Ss à “short-period” MPRS• Scale to S1 à “long-period” MPRS• “Blend” for mid-range periods

TL = 12 s region, probabilistic SSP = 2.165g and S1P = 0.837g, deterministic SSD = 1.500g and S1D = 0.600g.

RSSP

Hilo HI (-155.1, 19.7)

Period 5%-Damped Response Spectral Acceleration (g)T (s) A B BC C CD D DE E Default0.00 0.501 0.565 0.658 0.726 0.741 0.694 0.607 0.547 0.7410.01 0.503 0.568 0.662 0.730 0.748 0.703 0.617 0.547 0.7480.02 0.519 0.583 0.676 0.739 0.749 0.703 0.617 0.547 0.7490.03 0.596 0.662 0.750 0.792 0.778 0.703 0.617 0.547 0.7920.05 0.811 0.888 0.955 0.958 0.888 0.758 0.620 0.551 0.9580.08 1.040 1.142 1.214 1.193 1.076 0.900 0.713 0.624 1.1930.10 1.119 1.252 1.371 1.368 1.241 1.040 0.825 0.724 1.3680.15 1.117 1.291 1.535 1.606 1.497 1.266 1.002 0.875 1.6060.20 1.012 1.194 1.500 1.710 1.662 1.440 1.153 1.010 1.7100.25 0.897 1.075 1.397 1.714 1.766 1.584 1.299 1.153 1.7660.30 0.810 0.976 1.299 1.665 1.829 1.705 1.443 1.301 1.8290.40 0.689 0.833 1.138 1.525 1.823 1.802 1.607 1.484 1.8230.50 0.598 0.724 1.009 1.385 1.734 1.803 1.681 1.596 1.8030.75 0.460 0.536 0.760 1.067 1.407 1.566 1.598 1.589 1.5661.0 0.368 0.417 0.600 0.859 1.168 1.388 1.512 1.578 1.3881.5 0.261 0.288 0.410 0.600 0.839 1.086 1.348 1.540 1.0862.0 0.207 0.228 0.309 0.452 0.640 0.877 1.192 1.458 0.8773.0 0.152 0.167 0.214 0.314 0.449 0.632 0.889 1.111 0.6324.0 0.120 0.132 0.164 0.238 0.339 0.471 0.655 0.815 0.4715.0 0.100 0.109 0.132 0.188 0.263 0.359 0.492 0.607 0.3597.5 0.063 0.068 0.080 0.110 0.148 0.194 0.256 0.311 0.19410 0.042 0.045 0.052 0.069 0.089 0.113 0.144 0.170 0.113

0.00

0.25

0.50

0.75

1.00

1.25

1.50

0.01 0.10 1.00 10.00

Res

pons

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n (g

)


ABBCCCDDDEEDefault





Derived deterministic MPRS: • Select generic RSSP

SsDxS1D & SsD/S1D à (Tables C-1 & C-2)

• Scale to Ss à “short-period” MPRS• Scale to S1 à “long-period” MPRS• “Blend” for mid-range periods• Apply Deterministic Lower Limit

TL = 12 s region, probabilistic SSP = 2.165g and S1P = 0.837g, deterministic SSD = 1.500g and S1D = 0.600g.

RSSP

Hilo HI (-155.1, 19.7)





Honolulu, HI(prediction)

matching to updated 1998 Ss & S1

Hilo, HI(prediction)

matching to updated 1998 Ss & S1



Updated Site Amplifications:

FT = Sa at a site class ÷ Sa at BC

Fv

BC

D

B

CD

Fa

Fv=0 refers to sitespecific analysis requirement for site D



New Definitions of SMS & SM1:

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

2.2

2.4

0.1 1.0 10.0

Res

pons

e Sp

ectra

l Acc

eler

atio

n (g

)

Period (seconds)

MCEr Multi-Period Response Spectrum - Site Class BCMCEr Multi-Period Response Spectrum - Site Class DEDesign Multi-Period Response Spectrum - Site Class DETwo-Period Design Spectrum - Site Class DE

SDS = Max(0.9 x Sa[0.2s ≤ T ≤ 5s])

SD1/T = max(Sa1,T x 0.9 x Sa[1s ≤ T ≤ 2s])/T vS30 > 1,200 fpsmax(Sa1, T x 0.9 x Sa[1s ≤ T ≤ 5s])/T vS30 ≤ 1,200 fps



Summary of Updates to SMS & SM1 in Hawaii:

(Figure 22-5 proposed for 2020 NEHRP, Default Site Class)

Default Site Class: max C , CD , D



Summary:

1. Updated SS & S1 calculations for 2020 NEHRP (based on 1998/2001 hazard model)

• Updated the risk-targeted ground motion calculations (decreases down to about -15%):a) Changed β from 0.8 to 0.6b) Interpolation of hazard curves from linear to logc) Truncated hazard curves

• Updated the 84th percentile factor of deterministic ground motions (increases up to about 20%)

2. Derived Multi-Period Response Spectrum (MPRS) for 2020 NEHRP using the “MPRS study”

3. Made maps of SMS & SM1 for default site class for 2020 NEHRP

• Updated site coefficients, spectral shapes, sigma, etc



Questions & Discussion:

What are the future design needs from the New Hawaii Hazard Model?

1. Directionality of GMMs (application of max direction factor)

2. Are GMMs available for all periods & site classes? What to do if they are not? We could continue to use the MPRS study (do site amplifications in HI agree with the NGA-W2 models)?

3. Deterministic caps must be re-calculated using the new deaggregation tool. How would the new sources change this deagg results?

Date post:	18-Dec-2021
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