Single-Station Sigma Using NGA-West2 Data

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1 SSHAC Level 3 Southwestern U.S. Ground Motion Characterization WS-1, March 21, 213 Oakland, CA Single-Station Sigma Using NGA-West2 Data Linda Al Atik Resource Expert

2 Sigma Background GMPEs: ln Y T ( M, F, R, Vs3,...) es es e e es s es Bommer (21) 2

3 Residual Components Strasser et al. (29) B W es e es B e : Between-event (inter-event) residual for earthquake e W : Within-event (intra-event) es residual at station s for earthquake e 2 2 : Between-event standard deviation : Within-event standard deviation 3

4 Single-Station Sigma: Approach Given multiple recordings of GM at an individual site, S, allows estimating the systematic site effects, S2S S, and removing them from the GM variability: Single-Station Sigma S S 2 S represents the systematic deviation of the observed amplification at this site from the median amplification predicted by the model 4

5 Single-Station Sigma: Approach (cont d) WS W S2S es es s S S : systematic deviation of the observed 2 S amplification at this site from the median amplification at this site predicted by the model SS :Single-station within-event standard deviation SS :Single-station standard deviation SS 2 2 SS 5

6 Application to PSHA Removing the site-to-site residual from the GM variability leads to a reduced aleatory variability However, the median GM at the SITE needs to be estimated: ln Y ( T) ( M, R, T,...) S2S B WS es es e es s e es If site-specific knowledge is limited, use of single-station sigma SHOULD be accompanied with an INCREASE in epistemic uncertainty 6

7 Terminology Ergodic Partially Non-Ergodic Within-event residual, Single-station within-event residual, WS W S2S W es es es s Within-event standard deviation, Total standard deviation, 2 2 Single-station within-event standard deviation, SS Single-station standard deviation, SS 2 2 SS Al Atik et al. (21) 7

8 Data Needs Minimum of 5 recordings per earthquake in order to compute a reliable event term, B e Minimum of 5 recordings per site in order to compute the average site-to-site residual, S S 2 s 8

9 NGA-West2 Dataset CA SMM and global LM dataset: 21,539 recordings from 6 eqks 163 recordings with Sa = -999 eliminated 3 recordings missing magnitude eliminated 34 recordings missing distance measures eliminated 12 recordings missing station info eliminated 21,327 recordings from 578 eqks at 4,96 stations 9

10 Nb of Recordings NGA-West2 Dataset with Periods Period (sec) 1

11 Magnitude NGA-West2: Data Distribution Rrup (km) California Japan China Italy New Zealand Taiwan CA: 15,264 recs Taiwan: 1,986 recs Japan: 1,946 recs China: 1,332 recs Italy: 333 recs NZ: 217 recs Other (Alaska, Iran, Greece, Turkey, ): 249 recs 21,327 recordings from 578 eqks of 2.99 M

12 Frequency NGA-West2: Data Distribution (cont d) Total number of earthquakes: earthquakes with 5 or more recordings > 1 Nb. of Recordings per Eqk 12

13 Frequency NGA-West2: Data Distribution (cont d) > 1 Nb. of Recordings per Station For events with minimum of 5 recordings: Total number of stations: 4, stations have 5 recordings or more 399 stations have 1 recordings or more 13

14 Magnitude NGA-West2: Data Distribution (cont d) Minimum of 5 recs per eqk and per station: 15,592 recs from 364 eqks at 838 stations 8 7 Region Nrecs CA 13,162 Taiwan 1,339 China 1,76 Italy Rrup (km) California Taiwan China Italy 14

15 Frequency of Recs NGA-West2: Data Distribution (cont d) Minimum of 5 recs per eqk and per station: 15,592 recs from 364 eqks at 838 stations > 12 Vs3 (m/sec) 15

16 Magnitude Preliminary PhiSS Results: NGA-West2 Using preliminary AS13 within-event residuals: Minimum of 3 recs per eqk 15,619 recs from 326 eqks at 3,164 stations 8 7 Region Nrecs CA 12,25 Japan 1,7 Taiwan 1,535 Italy 175 New Zealand 72 China 48 Iran + Turkey 43 Others Rrup (km) CA Japan Taiwan Other 16

17 Frequency AS13 Dataset at PGA >1 Nb. of Recordings per Station Total number of stations: 3, stations have 5 recordings or more 322 stations have 1 recordings or more 17

18 Magnitude AS13 Dataset at PGA (cont d) Minimum of 5 recs per station: 11,188 recs 8 7 Region Nrecs CA 1,123 Taiwan 1,49 Italy Rrup (km) CA Taiwan Italy 18

19 Frequency of Recs AS13 Dataset at PGA (cont d) Minimum of 5 recs per station: 11,188 recs > 12 Vs3 (m/sec) 19

20 Standard Deviation Preliminary Results Period (sec) PhiSS All Phi PhiSS-CA PhiSS PhiSS-Taiwan 2

21 CA PhiSS Preliminary Results PhiSS s PGA Nb of Recordings 1.4 T 1 sec PhiSS s Nb of Recordings 21

22 PhiSS PhiSS Magnitude Dependence: CA.6 PGA Mag T 1. sec Mag 22

23 PhiSS PhiSS Distance Dependence: CA.8 PGA Rrup (km) T 1. sec Rrup (km) 23

24 PhiSS PhiSS M-R Dependence: CA 1 PGA Rrup (km) M 3 to 5 M 5 to 6 M 6 to 8 1 T 1. sec Rrup (km) M 3 to 5 M 5 to 6 M 6 to 8 24

25 PhiSS PhiSS V S3 Dependence: CA.7 PGA Vs3 (m/sec).6 T 1. sec Vs3 (m/sec) 25

26 References (I) Al Atik, L., N. Abrahamson, J. Bommer, F. Scherbaum, F. Cotton, N., Kuehn (21). The variability of ground-motion prediction models and its components, Seism. Res. Let., 81(5), Bommer, J. J. (21). Sigma: What it is, why it matters and what we can do with it, NGA-East workshop presentation, February 1, 21. Strasser, F.O., N.A. Abrahamson and J.J. Bommer (29). Sigma: Issues, insights and challenges, Seism. Res. Let., 8(1),

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