Velocity Model Attenuation Source Code CompletionDomain Size

Halfspace None (Elastic) Point SourceLarge

1D Crustal Model None (Elastic) Point SourceLarge

1D Crustal Model Freq. Indep. Q Point SourceLarge

1D Crustal Model Freq. Dep. Q Point SourceLarge

3D Crustal Model Freq. Indep. Q Point SourceLarge

3D Crustal Model Freq. Indep. Q Finite FaultLarge

3D Crustal Model Freq. Dep. Q Finite FaultLarge

3D Crustal Model Freq. Indep. Q Point SourceSmall

3D Crustal Model Freq. Indep. Q Finite F. (Wei)Small

3D Crustal Model Freq. Indep. Q Finite F. (G&P)Small

Verification and Validation of High-Frequency (fmax = 5 Hz) Ground Motion Simulations of the 2014 Mw 5.1 La Habra, California, earthquake

1: University of Memphis; 2: San Diego State University; 3: United States Geological Survey; 4: Southern California Earthquake Center;5: Carnegie Mellon University; 6: San Diego Super Computer Center; 7: University of Southern California.

Ricardo Taborda,1 Kim B. Olsen,2 Robert W. Graves,3 Fabio Silva,4 Naeem Khoshnevis,1 William Savran,2 Daniel Roten,2 Zheqiang Shi,2 Christine Goulet,4 Jacobo Bielak,5 Phil J. Maechling,4 Yifeng Cui,6 Thomas H. Jordan4,7

Department of Geological SciencesCollege of Sciences

The Southern California Earthquake Center (SCEC) High-F project seeks to advance physics-based, deterministic earthquake simulation with the long-term objective of im-proving ground motion prediction and seismic hazard models. An important aspect of this involves the verification of models and simulation methods, and the validation of synthetics with respect to data. The present study describes a recent concerted effort to verify different simulation methods, and attempts to reproduce the ground motions from the 2014 M 5.1 La Habra, California, earthquake in the greater Los Angeles region over a simulation domain of 180 km x 135 km, and 62 km in depth. The simulations are done using three high-performance computing codes; two of them implement the finite difference method and the third one implements a finite element approach. The models are tailored to satisfy a maximum frequency of 5 Hz and a minimum shear wave velocity of 500 m/s. We rely on the latest version of the community velocity model CVM-S, ver-sion 4.26.M01, and use a point source and two finite source models. The point source model is defined by a mechanism derived from strong-motion data and a slip-time signal obtained from a dynamic rough-fault rupture model. The two finite source models come from (i) an independent source inversion study, and (ii) a simulation done with a kinematic rupture generator also used in the SCEC Broadband Platform. At the verifica-tion stage, we compared synthetics from the three codes for the point source model, using the 3D regional structure and frequency independent attenuation (Q) models. The comparisons between the three codes exhibit very good agreement. For the validation stage, we compared seismograms collected at 300+ recording stations from different regional strong-motion seismic monitoring networks with synthetics obtained for the three different source models. Initial results indicate that extended source models, even for a moderate-size earthquake like the one considered here, tend to lead to better fits with data. Current and future efforts concentrate on defining the best possible source model based on goodness-of-fit comparison metrics, and testing the influence of other parameters such as a frequency dependent Q model and small scale heterogeneities. Simulations have been carried out on NCSA Blue Waters and on OLCF Titan.

Name:Date:Time:Magnitude:

Longitude:Latitude:Depth:

Strike/Dip/Rake:(Lee et al., 2014)

La Habra03-29-201404:09:42.97

Mw 5.1

117.930°33.922°5.0 km

239/70/38

Large Simulation Domain:180 km x 135 km x 61.875 km

Small Simulation Domain(green box):

28 km x 28 km x 14 km

Large Domain Bounding Box:-119.288842°, 34.120549°-118.354016°, 35.061096°-116.846030°, 34.025873°-117.780976°, 33.096503°

Rotation Angle: 39.9°

Avail. Records: 350+ stations

-116°30’-117°00’-117°30’-118°00’-118°30’-119°00’-119°30’

33°30’

34°00’

35°00’

33°00’

34°30’

135 k

m 180 km

Los Angeles

LongBeach

Riverside

Mission Viejo

Northridge

Santa Clarita

CatalinaIsland

Pacif ic Ocean

Chino Fault

Whittier Fault

Sierra Madre Fault Zone

San Andreas Fault Zone

Newport-Inglewood Fault

Yorb

a Lin

da

Trend

G

CI

CI.F

LS

RX

La Habra3-29-2014Mw 5.1

Los Angeles

LAX

SantaMonica

SanFernando

Malibu

SimiValley

SantaClarita

LongBeach

Oxnard

Glendora

AnaheimMission Viejo

LancasterSan

Bernardino

Riverside

Yucaipa

Ontario

Fontana

Pasadena

ThousandOaks

HuntingtonBeach

CoronaPomona

LakePerris

PalosVerdes

CI.FULCI.BRE

CI.DLACI.BHP

CI.GR2

CE.24945

CI.Q0049

CI.PTD

CI.AGO

180 Km

135

Km

28 km

28 km

Material ModelsHalfspace Model:Vs = 1.0 km/sVp = 2.0 km/sDensity = 2.1 g/cm3

a)

1D Crustal Model:Based on the Los Angeles basin model used in the SCEC Broadband Platform (BBP); linearly smoothed.Vsmin = 500 m/s

b)

3D Crustal Model:SCEC CVM-S4.26.M01Vsmin = 500 m/s

c)

Attenuation Parameters:Coarse-grain (finite difference codes)BKT model (finite element code)Qs = 100Vs (Vs in km/s)Qp = 2QsQ = Qo (frequency independent)Q = Qo·f0.8 (frequency dependent)

d)

7.06.01.54.03.02.01.00 km

Depth to Vs = 2.5 km/s

Dep

th (k

m)

0

5

10

15

20

25

301 3 5 70 2 4 6

Vp (km/s)Vs (km/s)Density (g/cm3)

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5−0.2

0

0.2

0.4

0.6

0.8

1.0

1.2Normalized Slip Rate

Time (s)0 1 2 3 4 5 6 7 8

0

0.2

0.4

0.6

0.8

1.0Normalized Slip Rate Fourier Amplitude

Frequency (Hz)

Obtained from a dynamic rupture simulation using SORD. The simulation corresponded to a rough fault model used in a previous study, not directly linked to the La Habra earth-quake. The selected slip function was rich in frequency content above 4 Hz. For our sim-ulations, the slip function was low-pass filtered at fc = 5 Hz (Butterworth, N = 4, 2 passes).

We consider two finite fault models. The first of these models (left) corresponds to the in-dependent inversion by Wei et al. (2014). The second model (right) corresponds to a kinematic rupture generated using the method introduced by Graves and Pitarka (2016). The latter method is one of the rupture generators implemented in the SCEC Broadband Platform.

We compute ground motions using three simulation codes. Two of these codes imple-ment the finite difference method (FDM) and the other implements the finite elment method (FEM) to solve wave propagations problems in anelastic media. All three codes have been used extensively in the past for large-scale ground motion earthquake simula-tions at low frequencies (< 1 Hz) and and in a reduced number of simulations at higher frequencies (> 1 Hz). This study evaluates their performance—through verification and validation—for the case of simulations in the 0–5 Hz frequency range. For some verifica-tion purposes we also used the wavenumber (f-K) code developed by Lupei Zhu (LSU).

We have designed a plan of simulations intended to verify the codes with various model-ing setups and to learn about the influence of different modeling conditions. Runs com-pleted thus far are indicated with filled colors associated to the simulation codes. Those runs alredy used in validation are indicated by the red frame.

In order to handle validation of synthetics against data, we developed software tools to process records from the Center for Engineering Strong Motion Data (V1 and V2) and the Southern California Earthquake Data Center. All synthetics and data are converted into a common format (same used in the SCEC Broadband Platform).

We validate simulations based on quantitative comparisons using the goodness-of-fit (GOF) method proposed by Anderson (2004), with minor modifications by Taborda and Bielak (2013). The method compares synthetics against data using eleven individual parameters: Arias intensity integral (C1), energy integral (C2), Arias intensity value (C3), total energy (C4), peak acceleration (C5), peak velocity (C6), peak displacement (C7), response spectrum (C8), Fourier amplitude spectrum (C9), cross correlation (C10), and strong-phase duration (C11). Each parameter is mapped onto a numerical scale rang-ing from 0 to 10, where a score of 10 corresponds to a perfect match. The scores are computed for different frequency bands, and ultimately combined into a final score.

Verification and validation evaluations are handled independently by SCEC. Our three simulation groups pass results to SCEC developers who run the comparison software and share results back to the simulators for group analysis. Standardizing and automat-ing this process was a major milestone in this effort.

Although codes have been verified before with respect to each other, a systematic ap-proach was necessary, including simple models such as halfspace and one-dimen-sional layered models.Point sources for small-magnitude events are appropriate for low-frequency simula-tions but not so for high-frequency simulations, especially in the vicinity of the epicen-ter. For moderate and large magnitude events, extended fault models are necessary even for low frequencies.It is critical to build the necessary software infrastructure for seismogram processing, and independent verification and validation with standard procedures.

Anderson, J. (2004). Quantitative Measure of the Goodness-of-fit of Synthetic Seismograms, in Proc. 13th World Conf. Earthquake Eng., No. 243, Vancouver, British Columbia, Canada.

Graves, R. W. and Pitarka, A. (2016). Kinematic Ground‐Motion Simulations on Rough Faults Includ-ing Effects of 3D Stochastic Velocity Perturbations, Seismol. Res. Lett., published online August 2016, doi: 10.1785/0120160088.

Lee, E.-J., Chen, P. and Jordan, T. H. (2014). Testing Waveform Predictions of 3D Velocity Models against Two Recent Los Angeles Earthquakes, Seismol.~Res.~Lett. 85 (6): 1275-1284, doi: 10.1785/0220140093.

Taborda, R. and Bielak, J. (2013). Ground-Motion Simulation and Validation of the 2008 Chino Hills, California, Earthquake, Bull. Seismol. Soc. Am. 103 (1): 131-156, doi: 10.1785/0120110325.

Wei, S., Yu, J., Bai,K., and Helmberger, D. (2014). Path calibration and finite fault modeling of the 2014 Mw 5.1 La Habra Earthquake, in Abs. SCEC Ann. Meet., No. 171, Palm Springs, California.

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–

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ξ = 5%

ξ = 5%

ξ = 5%

ξ = 5%

ξ = 5%

ξ = 5%

ξ = 5%

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Slip (cm) � 0 / 4 / 18

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Rise Time (s) � 0.0 / 0.4 / 0.8

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Peak Slip-rate (cm/s) � 0 / 36 / 350

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0102030405060

Cou

nt

0 1 2 3 4 5 6 7 8 9 10Score

0 1 2 3 4 5 6 7 8 9 10Score

0 1 2 3 4 5 6 7 8 9 10Score

0 1 2 3 4 5 6 7 8 9 10Score

0

10

Cou

nt

0 1 2 3 4 5 6 7 8 9 10Score

DataRWG

FEMHercules

FDMAWP-ODC

FDMAWP-RWG

F-KL. Zhu

Use

d in

val

idat

ion

Abstract

Event and Region of Interest

Point Source Model

Finite Fault Models

Simulation Verification and Validation Plan

3D Simulation Codes

Comparison Criteria and Software Validation Results

Verification ResultsStation CI.FUL

Station CI.DLA

Time (s) Frequency (Hz) Period (s)

Time (s) Frequency (Hz) Period (s)

Time (s) Time (s)

Station CI.BRE – Filtered

0.1–5 Hz

0.1–1 Hz

1–2 Hz

2–3 Hz

3–4 Hz

4–5 Hz

GOF MapsFinal Score, Large Domain, Point Source

Hercules SDSU

Analysis by Frequency Bands (Hercules)

Final Score, Small Domain, Source Models Comparison (RWG)Point Source Finite Fault - Wei Finite Fault - G&P

Time (s) Frequency (Hz) Period (s)

Point Source

Finite Fault - Wei

Finite Fault - G&P

0.1–0.5 Hz 1–2 Hz0.5–1 Hz 2–4 Hz

Lessons Learned

Relevant References

Station CI.DLA

CI.DLA