Transcript COMPILATION STRONG MOTION DATA FOR EASTERN CANADA

COMPILATION OF STRONG MOTION
DATA FROM EASTERN CANADA FOR
NGA-EAST PROJECT
Lan Lin
Postdoctoral Fellow, Geological Survey of Canada
Motivation
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Ground motion data are very important for
seismologists and earthquake engineers.
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Processed data are useful for the development of
attenuation relations for eastern North America.
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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
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Analog (SMA-1) instruments deployed during
aftershock sequences:
-- Miramichi, New Brunswick, 1982, magnitude mN=5.8
-- Nahanni, Northwest Territories, 1985, magnitude mN=6.1
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33 SMA records from Saguenay Eq,
14 from Miramichi Eq, 16 from Nahanni Eq.
Strong Motion Monitoring In
Eastern Canada
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SMA-1 instruments replaced by ETNA (on-site digital recording)
(1997-2004).
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ETNAs supplemented by Internet Accelerometers (IA) 2004
onwards.
ETNA Instrument
IA Instrument
Eastern Canadian
Strong-Motion Network
GSC ETNA Stations
Quebec
Charlevoix
Region
New
Brunswick
Ottawa
Ontario
(does not include IA instruments or instruments operated by Hydro-Quebec, etc)
ETNA Station Information
• Total 33 stations.
• 13 on free field
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20 in basement of 1-2 storey buildings.
26 on bedrock, 7 on soft soil.
ETNA Station Information
Registered station code
Characteristics of ETNA
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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
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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
Storage of ETNA Data
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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)
“SEED”
HNZ (Vertical)
Convention
HNE (E-W)
Band code
Instrument
code
Orientation code
Storage Procedure
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Step 1: Extract original event file (.EVT) for every record.
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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.
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2005/03/06, mN=5.4
Station: A11
Component: N-S
Software for analysis: SAC
Acceleration (nVolt)
N-S waveform recorded at station A11
from 2005/03/06 earthquake
Time (s)
Weak-Motion Monitoring Instruments
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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)
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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 (Count)
Velocity waveform
Time (s)
Acceleration (Count/s)
Acceleration waveform
Time (s)
Acceleration
(nVolt)
strong motion waveform
by ETNA
Time-lag (s)
Acceleration
(Count/s)
Time (s)
weak motion waveform
by seismometer
Cross-correlation Functions

( f  g )[n]   f  [m]g[n  m]
CCF

Time-lag, n (s)
Time-lag=52.25s
0.01
HNN
0.008
HHN
0.006
Acceleration (g)
0.004
Correlation
coefficient=0.993
0.002
0
0
5
10
15
20
25
30
35
40
-0.002
-0.004
-0.006
GOOD
AGREEMENT!!!
-0.008
-0.01
Time (s)
0.01
HNN
0.008
HHN
0.006
Acceleration (g)
0.004
0.002
0
10
10.5
11
11.5
12
12.5
-0.002
-0.004
-0.006
-0.008
-0.01
Time (s)
13
13.5
14
14.5
15
Time-traces
for segment
10s15s
Comparison of FFT Spectra
1.5
1800000
HNN
1600000
1.4
HHN
1.3
FFT ratio (HNN/HHN)
1400000
FFT
1200000
1000000
800000
600000
1.2
1.1
1.0
0.9
0.8
400000
0.7
200000
0.6
0
0
5
10
15
20
25
30
35
40
45
50
Frequency (Hz)
Fourier Spectra
+10%
0.10
-10%
0.5
1.00
10.00
20.00Hz
100.00
Frequency (Hz)
Ratio of FFT
(strong-motion over weak-motion)
• small difference for 1 to 20 Hz.
• 10% difference for frequency higher than 20 Hz, and lower than 1.0 Hz.
Conclusions
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Meta-data for records have been assembled.
About 300 records for storage.
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Waveform storage procedure for ETNA
data is established. Similar procedure can be
used for SMA data and IA data.
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Data from eastern Canada are ready for
uploading to Canadian National Waveform
Archive.
Future Work
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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.
Thank you!
Characteristics of IA
• Data type: acceleration
• Number of components recorded: two orthogonal
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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