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Site-Specific MCER Response Spectra for
L.A. Region from 3-D Numerical Simulations &
NGA West2 GMPEs
C.B. Crouse
AECOM
UGMS Meeting: November 8, 2017
MCER Spectra Developed by the SCEC
Utilization of Ground-Motion Simulations Committee (UGMS)
Formed in 2013
UGMS Committee Members
n C. Crouse – Chairn T Jordan – SCEC
n N. Luco – USGSn R. Bachman
n J. Hooper – MKAn J. Bielak – CMUn C. Kircher
n M. Hudson – AMECn M. Lew – AMEC
n R. Hamburger - SGH
n A. Frankel – USGSn N. Abrahamson – PG&E
n R. Graves – USGSn F. Naeim
n C. Hazelton – CSCn P. Somerville – AECOMn Jack Baker – Stanford
n J. Anderson – UNRn S. Rezaeian – USGS
n C. Goulet – SCEC
3-D Simulation Approach
1. Use UCERF2 Mw 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 Computational Platform used for Simulations
n 3-D physics-based model of fault rupture and wave propagation for S. CA EQs
n 40,000 regional earthquakes (MW ≥ 6) simulated from UCERF2.0 (2008)n Multiple hypocenter and slip models for each
given MW on given faultn e.g., 140 models for Mw6.7 on Northridge
fault (~ no. for other Mw on this fault)
n 440,000 ground-motion simulations for each of ~300 sites
Simulated Motions computed at ~300 CyberShake Sites
Advantages of 3D Simulations for L.A. Region
a(t)
Basin
FaultRock
Basin Structure, Vp, Vs, & Q – Well known for modeling propagation of longer period waves.
Validation of Simulations
a(t)
Basin
FaultRock
Validated against recordings from moderate M events.
UGMS has done limited validations for 1994 Mw 6.7 Northridge earthquake.
M8 Simulation on San Andreas
Site-Specific Approach using NGA West2 GMPEs
1. Use UCERF3 Mwrecurrence models
2. Select ground-motion eqns.
• Four NGA West 2 eqns.
- basin depth (Z1.0 or Z 2.5)
- Shear-wave vel. (VS30)
• Substitute Z1.0, Z 2.5 , VS30 values into eqns.
3. Proceed with PSHA/DSHA(C. 21, ASCE 7-16)
4. MCER Response Spectra
2013 NGA West2 Equations with Basin Depth Terms
n Abrahamson et al – Z1.0
n Boore et al – Z1.0
n Campbell & Bozorgnia – Z2.5
n Chiou & Youngs – Z1.0
Site
Z1.0
Z2.5
V = 1 km/sS
V = 2.5 km/sS
Depth
Basin Profile
VS30
Why New MCER are Improvement to MCER from Chapter 11 ASCE 7-16
n Site-Specific for Los Angeles Region
n Better job in accounting for:n local & regional geologyn fault directivity & fling (CyberShake)n 3-D effects of fault rupture & basin structure
on ground motion (CyberShake)
Why New MCER are Improvement to MCER from Chapter 11 ASCE 7-16
n Eliminates need for Fa & Fv tables, which:n Don’t directly account for basin effectsn Have step changes at site-class boundariesn Are constant for each site class, which
covers broad range of Vs30
MCER Response Spectra
n CyberShake (T = 2 – 10 sec)
n NGA West2 GMPEs (0 – 10 sec)
Determination of MCER Response Spectra, T = 2 - 10 sec
n Computed MCER from both approaches at selected sites in L.A. area
n Developed procedure for combining two MCER
n Checked final MCER for many L.A. area sites
Transform Sa to PSV
PSV = (T/2π)Sa
Sa
TTO TS TL
log PSV
log TTO TS TL1.0
0
1
2
3
4
5
6
1 2 3 4 5 6 7
Depth-km
Z1.0
Z2.5
LAPD PAS P22 LADT CCP S429 COO
200
400
2 3 5100
1000
1 10
PSV-cm/sec
T- sec
LAPD(Palmdale)- rocksite
NGAWest2CyberShake
LAPD
LAPD
200
400
2 3 510
100
1 10
PSV-cm/sec
T- sec
PAS(oldCITseismoclab)- rocksite
NGAWest2CyberShake
50
200
2 3 5PAS
PAS
100
1000
1 10
PSV-cm/sec
T- sec
P22(VenturaFreeway)- basinedge
NGAWest2CyberShake
P22
200
400
2 3 5
P22
100
1000
1 10
PSV-cm/sec
T- sec
LADT(DowntownL.A.)- basinedge
NGAWest2CyberShake
LADT
200
400
2 3 5
LADT
100
1000
1 10
PSV-cm/sec
T- sec
CPP(CenturyCityPlaza)- basinedge
NGAWest2CyberShake
CCP
200
400
2 3 5
CCP
100
1000
1 10
PSV-cm/sec
T- sec
s429(Carson)- deepbasin
NGAWest2CyberShake
s429
200
400
2 3 5
s429
100
1000
1 10
PSV-cm/sec
T- sec
COO(Compton)- deepbasin
NGAWest2CyberShake
COO
200
400
2 3 5
COO
MCER PSV for 7 Sites to Illustrate Trends
SourceModel G-MModels Weights
GMPE CollectiveWeightsforPeriods,T- secNGAWest2
IndividualWeight
<2 2 3 4 ≥5
AKS 0.25
UCERF3 BASS 0.25 1 0.8 0.7 0.6 0.5CB 0.25CY 0.25
Weighted Averaging of MCER Response Spectra
UCERF2 CyberShake 0 0.2 0.3 0.4 0.5
COO (Compton) - Deep Basin
400
2 53
200
100
1000
1 10
PSV-cm/sec
T- sec
NGAWest2CyberShakewt ave haz curvewt ave spectrum
MCER: COO (Compton) - Deep Basin
100
1000
1 10
PSV-cm/sec
T- sec
MCER:COO(Compton)- deepbasin
400
2 53
200
MCER: COO (Compton) - Deep Basin
0.0
0.5
1.0
1.5
2.0
2.5
0 1 2 3 4 5 6 7 8 9 10
Sa-g
T- sec
MCER:COO(Compton)- deepbasin
0
1
2
3
4
5
6
1 2 3 4 5 6 7 8
Depth-km
Z1.0
Z2.5
10
100
1 10
PSV-cm/sec
T- sec
MCER:s395(SanGrabrielMnts)- rocksite
8
8
200
300
50
2 3 510
100
1 10
PSV-cm/sec
T- sec
MCER:s393(E.Pasadena)- basinedge
7
7
200
300
50
2 3 510
100
1 10
PSV-cm/sec
T- sec
MCER:s391(L.A.)- basinedge
6
6
200
300
50
2 3 510
100
1 10
PSV-cm/sec
T- sec
MCER:s389(L.A.)- deepbasin
5
5
200
300
50
2 3 510
100
1 10
PSV-cm/sec
T- sec
MCER:s388(CentralL.A.)- deepbasin
4
4
200
300
50
2 3 510
100
1 10
PSV-cm/sec
T- sec
MCER:s387(CentralL.A.)- deepbasin
3
3
200
300
50
2 3 510
100
1 10
PSV-cm/sec
T- sec
MCER:s385(Torrance)- basin
2
2
200
300
50
2 3 510
100
1 10
PSV-cm/sec
T- sec
MCER:s383(PalosVerdes)- rocksite
1
1
200
300
50
2 3 5
Line 1
0
1
2
3
4
5
6
1 2 3 4 5 6
Depth-km
Z1.0
Z2.5
Line 2
10
100
1 10
PSV-cm/sec
T- sec
MCER:s520(LaVerne)- shallowbasin
6
6
200
300
50
2 3 510
100
1 10
PSV-cm/sec
T- sec
MCER:s518(Walnut)- shallowbasin
5
5
200
300
50
2 3 510
100
1 10
PSV-cm/sec
T- sec
MCER:s516(Brea)- basin
4
4
200
300
50
2 3 510
100
1 10
PSV-cm/sec
T- sec
MCER:s514(Fullerton)- deepbasin
3
3
200
300
50
2 3 510
100
1 10
PSV-cm/sec
T- sec
MCER:s512(GardenGrove)- deepbasin
2
2
200
300
50
2 3 510
100
1 10
PSV-cm/sec
T- sec
MCER:s510(SealBeach)- deepbasin
1
1
200
300
50
2 3 5
Intermediate Goal of UGMS
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 city/county officials &
geotechnical & structural engineers
n SCEC/UGMS look-up tool n ~ USGS web app tool
SCEC/UGMS Look-Up Tool
Provides site-specific MCER, DE & PGAM
Beta version available
Future Additions to Look-Up Tool
n Deaggregation Datan M-Distancen Fault
n Acceleration Time Historiesn San Andreas M~8 events
n BSE-1 & BSE-2 (ASCE 41-13)
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