2006/02/25 01:39:22 45.6500 -75.2300 20.0 4.50 Quebec, Canada
USGS Felt map for this earthquake
USGS Felt reports page for Eastern Canada
SLU Moment Tensor Solution
2006/02/25 01:39:22 45.6500 -75.2300 20.0 4.50 Quebec, Canada
Best Fitting Double Couple
Mo = 3.39e+21 dyne-cm
Mw = 3.62
Z = 16 km
Plane Strike Dip Rake
NP1 145 50 85
NP2 333 40 96
Principal Axes:
Axis Value Plunge Azimuth
T 3.39e+21 84 20
N 0.00e+00 4 148
P -3.39e+21 5 239
Moment Tensor: (dyne-cm)
Component Value
Mxx -8.81e+20
Mxy -1.48e+21
Mxz 4.92e+20
Myy -2.44e+21
Myz 3.71e+20
Mzz 3.32e+21
--------------
#########-------------
--##############------------
--#################-----------
----###################-----------
-----#####################----------
------######################----------
-------########################---------
-------########################---------
---------########### ##########---------
---------########### T ###########--------
----------########## ###########--------
-----------########################-------
-----------#######################------
------------######################------
- ---------####################-----
P -----------#################-----
-------------###############----
---------------############---
------------------#######---
---------------------#
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Harvard Convention
Moment Tensor:
R T F
3.32e+21 4.92e+20 -3.71e+20
4.92e+20 -8.81e+20 1.48e+21
-3.71e+20 1.48e+21 -2.44e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20060225013922/index.html
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STK = 145
DIP = 50
RAKE = 85
MW = 3.62
HS = 16.0
The waveform inversion is preferred.
The following compares this source inversion to others
SLU Moment Tensor Solution
2006/02/25 01:39:22 45.6500 -75.2300 20.0 4.50 Quebec, Canada
Best Fitting Double Couple
Mo = 3.39e+21 dyne-cm
Mw = 3.62
Z = 16 km
Plane Strike Dip Rake
NP1 145 50 85
NP2 333 40 96
Principal Axes:
Axis Value Plunge Azimuth
T 3.39e+21 84 20
N 0.00e+00 4 148
P -3.39e+21 5 239
Moment Tensor: (dyne-cm)
Component Value
Mxx -8.81e+20
Mxy -1.48e+21
Mxz 4.92e+20
Myy -2.44e+21
Myz 3.71e+20
Mzz 3.32e+21
--------------
#########-------------
--##############------------
--#################-----------
----###################-----------
-----#####################----------
------######################----------
-------########################---------
-------########################---------
---------########### ##########---------
---------########### T ###########--------
----------########## ###########--------
-----------########################-------
-----------#######################------
------------######################------
- ---------####################-----
P -----------#################-----
-------------###############----
---------------############---
------------------#######---
---------------------#
--------------
Harvard Convention
Moment Tensor:
R T F
3.32e+21 4.92e+20 -3.71e+20
4.92e+20 -8.81e+20 1.48e+21
-3.71e+20 1.48e+21 -2.44e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20060225013922/index.html
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The focal mechanism was determined using broadband seismic waveforms. The location of the event and the and stations used for the waveform inversion are shown in the next figure.
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The program wvfgrd96 was used with good traces observed at short distance to determine the focal mechanism, depth and seismic moment. This technique requires a high quality signal and well determined velocity model for the Green functions. To the extent that these are the quality data, this type of mechanism should be preferred over the radiation pattern technique which requires the separate step of defining the pressure and tension quadrants and the correct strike.
The observed and predicted traces are filtered using the following gsac commands:
hp c 0.12 n 3 lp c 0.50 n 3The results of this grid search from 0.5 to 19 km depth are as follow:
DEPTH STK DIP RAKE MW FIT
WVFGRD96 0.5 225 75 50 3.25 0.3320
WVFGRD96 1.0 230 65 40 3.31 0.3356
WVFGRD96 2.0 225 65 50 3.26 0.3249
WVFGRD96 3.0 35 90 -35 3.29 0.3013
WVFGRD96 4.0 35 90 -35 3.32 0.2806
WVFGRD96 5.0 225 35 -95 3.38 0.2650
WVFGRD96 6.0 50 45 90 3.42 0.2544
WVFGRD96 7.0 265 35 -45 3.43 0.2580
WVFGRD96 8.0 80 35 -60 3.47 0.2794
WVFGRD96 9.0 65 35 -70 3.48 0.2831
WVFGRD96 10.0 330 35 90 3.54 0.2903
WVFGRD96 11.0 335 40 90 3.55 0.3041
WVFGRD96 12.0 145 50 75 3.57 0.3157
WVFGRD96 13.0 150 45 85 3.59 0.3614
WVFGRD96 14.0 150 50 80 3.60 0.3652
WVFGRD96 15.0 145 50 80 3.61 0.3818
WVFGRD96 16.0 145 50 85 3.62 0.3837
WVFGRD96 17.0 145 45 85 3.62 0.3792
WVFGRD96 18.0 150 50 95 3.63 0.3829
WVFGRD96 19.0 145 45 85 3.62 0.3791
WVFGRD96 20.0 325 45 90 3.63 0.3526
WVFGRD96 21.0 140 45 85 3.64 0.3596
WVFGRD96 22.0 135 40 65 3.63 0.3364
WVFGRD96 23.0 155 35 15 3.72 0.3346
WVFGRD96 24.0 130 40 60 3.64 0.3310
WVFGRD96 25.0 155 35 15 3.72 0.3292
WVFGRD96 26.0 155 30 15 3.73 0.3496
WVFGRD96 27.0 150 35 10 3.75 0.3489
WVFGRD96 28.0 150 35 10 3.74 0.3397
WVFGRD96 29.0 155 35 15 3.72 0.3254
The best solution is
WVFGRD96 16.0 145 50 85 3.62 0.3837
The mechanism correspond to the best fit is
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The best fit as a function of depth is given in the following figure:
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The comparison of the observed and predicted waveforms is given in the next figure. The red traces are the observed and the blue are the predicted. Each observed-predicted componnet is plotted to the same scale and peak amplitudes are indicated by the numbers to the left of each trace. The number in black at the rightr of each predicted traces it the time shift required for maximum correlation between the observed and predicted traces. This time shift is required because the synthetics are not computed at exactly the same distance as the observed and because the velocity model used in the predictions may not be perfect. A positive time shift indicates that the prediction is too fast and should be delayed to match the observed trace (shift to the right in this figure). A negative value indicates that the prediction is too slow. The bandpass filter used in the processing and for the display was
hp c 0.12 n 3 lp c 0.50 n 3
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| Focal mechanism sensitivity at the preferred depth. The red color indicates a very good fit to thewavefroms. Each solution is plotted as a vector at a given value of strike and dip with the angle of the vector representing the rake angle, measured, with respect to the upward vertical (N) in the figure. |
Should the national backbone of the USGS Advanced National Seismic System (ANSS) be implemented with an interstation separation of 300 km, it is very likely that an earthquake such as this would have been recorded at distances on the order of 100-200 km. This means that the closest station would have information on source depth and mechanism that was lacking here.
Dr. Harley Benz, USGS, provided the USGS USNSN digital data. The digital data used in this study were provided by Natural Resources Canada through their AUTODRM site http://www.seismo.nrcan.gc.ca/nwfa/autodrm/autodrm_req_e.php, and IRIS using their BUD interface.
Thanks also to the many seismic network operators whose dedication make this effort possible: University of Alaska, University of Washington, Oregon State University, University of Utah, Montana Bureas of Mines, UC Berkely, Caltech, UC San Diego, Saint L ouis University, Universityof Memphis, Lamont Doehrty Earth Observatory, Boston College, the Iris stations and the Transportable Array of EarthScope.
The CUS used for the waveform synthetic seismograms and for the surface wave eigenfunctions and dispersion is as follows:
MODEL.01 CUS Model with Q from simple gamma values ISOTROPIC KGS FLAT EARTH 1-D CONSTANT VELOCITY LINE08 LINE09 LINE10 LINE11 H(KM) VP(KM/S) VS(KM/S) RHO(GM/CC) QP QS ETAP ETAS FREFP FREFS 1.0000 5.0000 2.8900 2.5000 0.172E-02 0.387E-02 0.00 0.00 1.00 1.00 9.0000 6.1000 3.5200 2.7300 0.160E-02 0.363E-02 0.00 0.00 1.00 1.00 10.0000 6.4000 3.7000 2.8200 0.149E-02 0.336E-02 0.00 0.00 1.00 1.00 20.0000 6.7000 3.8700 2.9020 0.000E-04 0.000E-04 0.00 0.00 1.00 1.00 0.0000 8.1500 4.7000 3.3640 0.194E-02 0.431E-02 0.00 0.00 1.00 1.00
Here we tabulate the reasons for not using certain digital data sets
The following stations did not have a valid response files:
DATE=Tue Nov 25 10:23:01 CST 2008