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Incorporating SCEC CyberShake Ground Motions in Seismic Design Spectra for Southern California (MCER)Christine Goulet, SCEC Robert Graves, USGSC.B. Crouse, AECOM

PEER 2019 Annual Meeting25th Anniversary of Northridge EarthquakeJanuary 17, 2019 @ UCLA

Questions and comments: cgoulet@usc.edu

Talk Outline

n UGMS project and team n CyberShake basicsn MCER using 3-D Simulation & GMPE

approachesn Results using the SCEC UGMS look-up tool

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UGMS Committee Members

n C. Crouse (chair) – AECOM

n T Jordan – SCEC

n N. Luco – USGS

n R. Bachman

n J. Hooper – MKA

n J. Bielak – CMU

n C. Kircher

n M. Hudson – Wood plc

n M. Lew – Wood plc

n R. Hamburger - SGH

n A. Frankel – USGS

n N. Abrahamson – PG&E

n R. Graves – USGS

n F. Naeim

n A. Sumer – OSHPD

n P. Somerville – AECOM

n Jack Baker – Stanford

n J. Anderson – UNR

n S. Rezaeian – USGS

n C. Goulet – SCEC

UGMS: Utilization of Ground Motion SimulationsFormed in 2013 by SCEC as a Technical Activity Group (TAG)

Earthquake Rupture Forecast (e.g. UCERF2)

Kinematic source models 3D velocity model + wave propagation

Seismogramsand intensity measures

+ + =

Hazard Curves andfault disaggregation

M, R, εdisaggregation Hazard maps

CyberShake: PSHA from Physics-Based Simulations

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Simulated Motions computed at 336 CyberShake Sites3-D physics-based model of fault rupture and wave propagation for S. CA EQsn 400,000 simulations

n 40,000 regional earthquakes (M ≥ 6)n Multiple hypocenters and slip models

for each given M on given fault ; e.g., 140 models for M6.7 on Northridge fault

GMPE Comparisons

Compare CyberShake intensities to NGA-West2 GMPE distributions for magnitude and distance ranges where GMPEs are well constrained

Pasadena Site (rock)All rupture variations:● M6.5-7● 40-80 km source/site

distance

Yellow region is a factor of 2

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All LA Area (336 Sites)

GMPE Comparisons (cont)

USC (Deep Soil)

Data Comparisons: Northridge

Compare CyberShakesimulation intensity distribution with Northridge recordings• Include all ruptures on the

UCERF2 “Northridge” source, M6.65-6.75

• Distribution: gray histogram• Mean: black line

• Compare with nearby record(s)• green lines

• Compare with mean of GMPEs• blue line

LA Downtown

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Data Comparisons: Northridge (cont)

Compton (deep basin)Century City (basin edge)

Data Comparisons: Northridge (cont)

Compton (deep basin)Century City (basin edge)

Computing Site Specific MCER

GMPEs (0 – 10 sec)

1. Use UCERF3 recurrence

models

2. Select ground-motion

eqns.

• Four NGA-West 2 eqns.

• shear-wave vel. (VS30), input

• basin depth (Z1.0 or Z 2.5), from

CVM

3. Proceed with PSHA/DSHA

(C. 21, ASCE 7-16)

4. MCER Response Spectra

1. Use UCERF2 fault

recurrence models

2. Do simulations

H1 & H2 accel. a(t)

response spectra, Sa(T)

median Sa(T) & sln

3. Proceed with PSHA/DSHA

(C. 21, ASCE 7-16)

4. MCER Response Spectra

CyberShake (2 – 10 sec)

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UCERF2 CyberShake 0 0.2 0.3 0.4 0.5

Source Model GM Models Weights

GMPE Collective Weights for Periods, T - sec

NGA West2

IndividualWeight

< 2 2 3 4 ≥ 5

ASK 0.25

UCERF3 BSSA 0.25 1 0.8 0.7 0.6 0.5CB 0.25CY 0.25

Weighted Averaging of MCER Response Spectra

End Products of UGMS Project

n Site-Specific MCER for L. A. arean Alternative to ASCE 7-16 “maps” (Ch 22)

for Southern California and Fa & Fv (Ch 11)n Resource to bldg. officials & engineers

n SCEC/UGMS look-up tool n ~ USGS web app tool

https://data2.scec.org/ugms-mcerGM-tool_v18.4

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SCEC UGMS MCER Look-Up Tool

Downtown Los Angeles (LADT) Example

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LADT Site-Specific MCER Response Spectra

LADT MCER Response Spectra

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LADT Final Site-Specific MCER from Averaging

% Difference between Site-Specific & NGA West2 MCER

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Reports and output

New MCER as Improvement to MCER from Ch. 11 in ASCE 7-16 or from Ch. 21 using GMPEs only

n Site-Specific for Los Angeles Region

n Accounts for:n local & regional geologyn fault directivity & fling (CyberShake)n coupling of 3-D effects of fault rupture &

basin structure on ground motion (CyberShake)

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Future work

n Incorporate BSE (seismic rehabilitation of buildings per ASCE 41-17) and SLE (LATBSDC) design spectra

n Provide disaggregation resultsn Provide vetted set of time series from

CyberShake for nonlinear time history analyses

Thank you…

John HooperGideon JuveAndreas SkarlatoudisJesus AcostaPhil MaechlingNaeem KoshnevisRicardo TabordaCurt HaseltonJack BakerJohn AndersenRob GravesGreg DeierleinNorm AbrahamsonRon HamburgerAmit ChourasiaScott CallaghanTing Lin

Sanaz RezaeianMarshall LewJacobo BielakPaul SomervilleMorgan MoschettiFarzin ZareianChris TokasNenad BijelicEwa DeelmanFeng WangRalph ArchuletaBob BachmanChristineGouletFarzad NaeimJosh GebeleinKaran VahiC.B. Crouse

Art FrankelYifeng CuiTom JordanWen-Yi YenCharlie KircherAli SumerNico LucoMarty HudsonKevin MilnerDawei MuKim Olsen…

SCEC Workshop on Simulations