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COMPILATION OF STRONG MOTION DATA FROM EASTERN CANADA FOR NGA-EAST PROJECT

COMPILATION OF STRONG MOTION DATA FROM EASTERN CANADA FOR NGA-EAST PROJECT. Lan Lin Postdoctoral Fellow, Geological Survey of Canada. Motivation. Ground motion data are very important for seismologists and earthquake engineers.

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COMPILATION OF STRONG MOTION DATA FROM EASTERN CANADA FOR NGA-EAST PROJECT

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  1. COMPILATION OF STRONG MOTION DATA FROM EASTERN CANADA FOR NGA-EAST PROJECT Lan Lin Postdoctoral Fellow, Geological Survey of Canada

  2. Motivation • Ground motion data are very important for seismologists and earthquake engineers. • Processed data are useful for the development of attenuation relations for eastern North America. • Strong motion data from eastern Canada have not been complied and processed.

  3. Strong Motion Monitoring In Eastern Canada • Started in 1970s (AR-240 instruments). • First record: 1979 Charlevoix mN 5.0 earthquake. • Analog (SMA-1) Network deployed in 1970s to record “next” Charlevoix earthquake on rock sites. -- recorded Saguenay mainshock, Quebec -- 1988/11/25 -- magnitude mN=6.5, distance from 43 to 200 km

  4. Strong Motion Monitoring In Eastern Canada • Analog (SMA-1) instruments deployed during aftershock sequences: -- Miramichi, New Brunswick, 1982, magnitude mN=5.8 -- Nahanni, Northwest Territories, 1985, magnitude mN=6.1 • 33 SMA records from Saguenay Eq, 14 from Miramichi Eq, 16 from Nahanni Eq.

  5. Strong Motion Monitoring In Eastern Canada • SMA-1 instruments replaced by ETNA (on-site digital recording) (1997-2004). • ETNAs supplemented by Internet Accelerometers (IA) 2004 onwards. ETNA Instrument IA Instrument

  6. Quebec Charlevoix Region New Brunswick Ottawa Ontario Eastern Canadian Strong-Motion Network GSC ETNA Stations (does not include IA instruments or instruments operated by Hydro-Quebec, etc)

  7. ETNA Station Information • Total 33 stations. • 13 on free field 20 in basement of 1-2 storey buildings. • 26 on bedrock, 7 on soft soil.

  8. ETNA Station Information Registered station code

  9. Characteristics of ETNA • Data type: acceleration • Number of components recorded: two orthogonal horizontal, one vertical • Sampling rate: 200s/s (i.e., ΔT=0.005s) • 10 seconds of pre-event duration • Unit: Volt

  10. Selected ETNA Records for Canadian Archive • Number of records selected: 76 • Number of components: 228 (=76*3) • Maximum PGA: 0.2g • Maximum magnitude: mN 5.4 (2005/03/06)

  11. Typical Record Information Magnitude is currently mN - will be changed to moment magnitude

  12. “SEED” Convention Band code Orientation code Instrument code Storage of ETNA Data • Canadian National Waveform Archive i.e., accessible to all through web-based tools • Data type: raw data, without baseline correction and filtering • Data format: CA • Data unit: nVolt (=109*Volt) • Channel code: HNN (N-S) HNZ (Vertical) HNE (E-W)

  13. Storage Procedure • Step 1: Extract original event file (.EVT) for every record. • Step 2: Convert .EVT file into ASCII file, generate 3 data files, for N-S, V, and E-W comp. • Step 3: Modify ASCII file. (a) add header information, i.e., station code, channel code, event start time, sample rate, and number of data points. (b) change units (Volt nVolt, i.e., multiply by 109). • Step 4: Generate CA file.

  14. Storage Test • Event considered: Riviere-du-Loup Eq. 2005/03/06, mN=5.4 • Station: A11 • Component: N-S • Software for analysis: SAC

  15. Acceleration (nVolt) Time (s) N-S waveform recorded at station A11 from 2005/03/06 earthquake

  16. Weak-Motion Monitoring Instruments • Seismometers • Data type: VELOCITY • Number of components recorded: two horizontal components, one vertical component • Sampling rate: 40s/s, 100s/s • Unit: Count

  17. Waveforms Similarity Analysis(ETNA vs. Seismometer Records) • Extract data from weak-motion database • Same event: 2005/03/06 • Same station: A11 • Same component: N-S

  18. N-S waveform recorded at station A11 for 2005/03/06 earthquake (weak-motion instrument) Velocity waveform Velocity (Count) Time (s)

  19. Acceleration waveform Acceleration (Count/s) Time (s)

  20. Acceleration (nVolt) Time-lag (s) Acceleration (Count/s) strong motion waveform by ETNA weak motion waveform by seismometer Time (s)

  21. Time-lag=52.25s Cross-correlation Functions CCF Time-lag, n (s)

  22. Correlation coefficient=0.993 GOOD AGREEMENT!!! Time-traces for segment 10s15s

  23. Comparison of FFT Spectra +10% -10% 20.00Hz Ratio of FFT (strong-motion over weak-motion) Fourier Spectra • small difference for 1 to 20 Hz. • 10% difference for frequency higher than 20 Hz, and lower than 1.0 Hz.

  24. Conclusions • Meta-data for records have been assembled. About 300 records for storage. • Waveform storage procedure for ETNA data is established. Similar procedure can be used for SMA data and IA data. • Data from eastern Canada are ready for uploading to Canadian National Waveform Archive.

  25. Future Work • Compilation of GSC IA data. • Compilation of digitized SMA-1 data from Saguenay, Miramichi and Nahanni Eqs. • Assembly of strong motion data from other operators, e.g., Hydro-Quebec, if allowed. • Compilation of analogdata – how to make available.

  26. Thank you!

  27. Characteristics of IA • Data type: acceleration • Number of components recorded: two orthogonal horizontal, one vertical • Sampling rate: 100s/s (i.e., ΔT=0.01s) • Internet-connected (real-time) • 2 days continuous data plus triggers recorded on internal flash card • NTP clock, drifts ~0.01 sec • Price about $2500 • GSC design, now available from Geosig.com

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