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)