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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 Lan Lin Postdoctoral Fellow, Geological Survey of Canada
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.
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
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.
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
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)
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.
ETNA Station Information Registered station code
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
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)
Typical Record Information Magnitude is currently mN - will be changed to moment magnitude
“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)
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.
Storage Test • Event considered: Riviere-du-Loup Eq. 2005/03/06, mN=5.4 • Station: A11 • Component: N-S • Software for analysis: SAC
Acceleration (nVolt) Time (s) N-S waveform recorded at station A11 from 2005/03/06 earthquake
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
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
N-S waveform recorded at station A11 for 2005/03/06 earthquake (weak-motion instrument) Velocity waveform Velocity (Count) Time (s)
Acceleration waveform Acceleration (Count/s) Time (s)
Acceleration (nVolt) Time-lag (s) Acceleration (Count/s) strong motion waveform by ETNA weak motion waveform by seismometer Time (s)
Time-lag=52.25s Cross-correlation Functions CCF Time-lag, n (s)
Correlation coefficient=0.993 GOOD AGREEMENT!!! Time-traces for segment 10s15s
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.
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.
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.
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