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

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 mN6.5, 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 mN5.8
• -- Nahanni, Northwest Territories, 1985,
  magnitude mN6.1
• 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
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., ?T0.005s)
• 10 seconds of pre-event duration
• Unit Volt

10
Selected ETNA Records for Canadian Archive

• Number of records selected 76
• Number of components 228 (763)
• 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
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 (109Volt)
• 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, mN5.4
• Station A11
• Component N-S
• Software for analysis SAC

15
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
Time (s)
21
Cross-correlation Functions
CCF
Time-lag, n (s)
22
Correlation coefficient0.993
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 analog data 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., ?T0.01s)
• 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