Location

2015/01/16 13:05:28 49.42 -66.79 10.0 3.8 Quebec

Arrival Times (from USGS)

Arrival time list

Felt Map

USGS Felt map for this earthquake

USGS Felt reports main page

Focal Mechanism

 USGS/SLU Moment Tensor Solution
 ENS  2015/01/16 13:05:28:0  49.42  -66.79  10.0 3.8 Quebec
 
 Stations used:
   CN.A11 CN.A16 CN.A21 CN.A61 CN.A64 CN.BATG CN.DMCQ CN.LMQ 
   NE.EMMW NE.PQI NE.WVL TA.D59A TA.D60A TA.D61A TA.D62A 
   TA.D63A TA.E60A TA.E61A TA.E63A TA.E64A TA.F59A TA.F60A 
   TA.F61A TA.F63A TA.F64A TA.G60A TA.G61A TA.G62A TA.G63A 
   TA.G64A TA.G65A TA.H61A TA.H62A TA.H63A TA.H64A TA.H66A 
   US.LBNH US.PKME 
 
 Filtering commands used:
   cut o DIST/3.3 -30 o DIST/3.3 +60
   rtr
   taper w 0.1
   hp c 0.03 n 3 
   lp c 0.07 n 3 
   br c 0.12 0.25 n 4 p 2
 
 Best Fitting Double Couple
  Mo = 3.76e+21 dyne-cm
  Mw = 3.65 
  Z  = 19 km
  Plane   Strike  Dip  Rake
   NP1      335    60    70
   NP2      191    36   121
  Principal Axes:
   Axis    Value   Plunge  Azimuth
    T   3.76e+21     68     204
    N   0.00e+00     17     345
    P  -3.76e+21     13      79

 Moment Tensor: (dyne-cm)
    Component   Value
       Mxx     3.07e+20
       Mxy    -4.56e+20
       Mxz    -1.33e+21
       Myy    -3.37e+21
       Myz    -1.33e+21
       Mzz     3.06e+21
                                                     
                                                     
                                                     
                                                     
                     #######-------                  
                 -----###--------------              
              --------###-----------------           
             -------#######----------------          
           --------##########----------------        
          --------#############---------------       
         --------###############---------------      
        --------#################---------------     
        -------###################-----------        
       --------####################---------- P -    
       --------#####################---------   -    
       -------#######################------------    
       -------##########   ##########------------    
        ------########## T ###########----------     
        -------#########   ###########----------     
         ------#######################---------      
          ------######################--------       
           ------#####################-------        
             -----####################-----          
              -----###################----           
                 ---#################--              
                     --############                  
                                                     
                                                     
                                                     
 Global CMT Convention Moment Tensor:
      R          T          P
  3.06e+21  -1.33e+21   1.33e+21 
 -1.33e+21   3.07e+20   4.56e+20 
  1.33e+21   4.56e+20  -3.37e+21 


Details of the solution is found at

http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20150116130528/index.html
        

Preferred Solution

The preferred solution from an analysis of the surface-wave spectral amplitude radiation pattern, waveform inversion and first motion observations is

      STK = 335
      DIP = 60
     RAKE = 70
       MW = 3.65
       HS = 19.0

The NDK file is 20150116130528.ndk The waveform inversion is preferred.

Moment Tensor Comparison

The following compares this source inversion to others
SLU
 USGS/SLU Moment Tensor Solution
 ENS  2015/01/16 13:05:28:0  49.42  -66.79  10.0 3.8 Quebec
 
 Stations used:
   CN.A11 CN.A16 CN.A21 CN.A61 CN.A64 CN.BATG CN.DMCQ CN.LMQ 
   NE.EMMW NE.PQI NE.WVL TA.D59A TA.D60A TA.D61A TA.D62A 
   TA.D63A TA.E60A TA.E61A TA.E63A TA.E64A TA.F59A TA.F60A 
   TA.F61A TA.F63A TA.F64A TA.G60A TA.G61A TA.G62A TA.G63A 
   TA.G64A TA.G65A TA.H61A TA.H62A TA.H63A TA.H64A TA.H66A 
   US.LBNH US.PKME 
 
 Filtering commands used:
   cut o DIST/3.3 -30 o DIST/3.3 +60
   rtr
   taper w 0.1
   hp c 0.03 n 3 
   lp c 0.07 n 3 
   br c 0.12 0.25 n 4 p 2
 
 Best Fitting Double Couple
  Mo = 3.76e+21 dyne-cm
  Mw = 3.65 
  Z  = 19 km
  Plane   Strike  Dip  Rake
   NP1      335    60    70
   NP2      191    36   121
  Principal Axes:
   Axis    Value   Plunge  Azimuth
    T   3.76e+21     68     204
    N   0.00e+00     17     345
    P  -3.76e+21     13      79

 Moment Tensor: (dyne-cm)
    Component   Value
       Mxx     3.07e+20
       Mxy    -4.56e+20
       Mxz    -1.33e+21
       Myy    -3.37e+21
       Myz    -1.33e+21
       Mzz     3.06e+21
                                                     
                                                     
                                                     
                                                     
                     #######-------                  
                 -----###--------------              
              --------###-----------------           
             -------#######----------------          
           --------##########----------------        
          --------#############---------------       
         --------###############---------------      
        --------#################---------------     
        -------###################-----------        
       --------####################---------- P -    
       --------#####################---------   -    
       -------#######################------------    
       -------##########   ##########------------    
        ------########## T ###########----------     
        -------#########   ###########----------     
         ------#######################---------      
          ------######################--------       
           ------#####################-------        
             -----####################-----          
              -----###################----           
                 ---#################--              
                     --############                  
                                                     
                                                     
                                                     
 Global CMT Convention Moment Tensor:
      R          T          P
  3.06e+21  -1.33e+21   1.33e+21 
 -1.33e+21   3.07e+20   4.56e+20 
  1.33e+21   4.56e+20  -3.37e+21 


Details of the solution is found at

http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20150116130528/index.html
	

Magnitudes

mLg Magnitude


(a) mLg computed using the IASPEI formula; (b) mLg residuals ; the values used for the trimmed mean are indicated.

ML Magnitude


(a) ML computed using the IASPEI formula for Horizontal components; (b) ML residuals computed using a modified IASPEI formula that accounts for path specific attenuation; the values used for the trimmed mean are indicated. The ML relation used for each figure is given at the bottom of each plot.


(a) ML computed using the IASPEI formula for Vertical components (research); (b) ML residuals computed using a modified IASPEI formula that accounts for path specific attenuation; the values used for the trimmed mean are indicated. The ML relation used for each figure is given at the bottom of each plot.

Context

The next figure presents the focal mechanism for this earthquake (red) in the context of other events (blue) in the SLU Moment Tensor Catalog which are within ± 0.5 degrees of the new event. This comparison is shown in the left panel of the figure. The right panel shows the inferred direction of maximum compressive stress and the type of faulting (green is strike-slip, red is normal, blue is thrust; oblique is shown by a combination of colors).

Waveform Inversion

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.
Location of broadband stations used for waveform inversion

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:

cut o DIST/3.3 -30 o DIST/3.3 +60
rtr
taper w 0.1
hp c 0.03 n 3 
lp c 0.07 n 3 
br c 0.12 0.25 n 4 p 2
The results of this grid search from 0.5 to 19 km depth are as follow:

           DEPTH  STK   DIP  RAKE   MW    FIT
WVFGRD96    1.0   340    65   -85   3.57 0.5189
WVFGRD96    2.0   330    60   -50   3.57 0.5188
WVFGRD96    3.0   325    65   -60   3.65 0.5140
WVFGRD96    4.0   320    65   -65   3.69 0.5093
WVFGRD96    5.0   320    90    60   3.60 0.5032
WVFGRD96    6.0   320    90    60   3.58 0.5166
WVFGRD96    7.0   140    90   -55   3.57 0.5259
WVFGRD96    8.0   325    85    55   3.57 0.5343
WVFGRD96    9.0   330    75    60   3.57 0.5423
WVFGRD96   10.0   330    75    60   3.60 0.5486
WVFGRD96   11.0   335    70    65   3.61 0.5571
WVFGRD96   12.0   340    65    70   3.63 0.5648
WVFGRD96   13.0   340    65    70   3.63 0.5718
WVFGRD96   14.0   335    65    70   3.62 0.5774
WVFGRD96   15.0   335    65    70   3.63 0.5817
WVFGRD96   16.0   335    65    70   3.63 0.5849
WVFGRD96   17.0   330    65    65   3.63 0.5870
WVFGRD96   18.0   335    60    70   3.65 0.5884
WVFGRD96   19.0   335    60    70   3.65 0.5889
WVFGRD96   20.0   330    65    70   3.66 0.5888
WVFGRD96   21.0   330    65    70   3.67 0.5878
WVFGRD96   22.0   330    65    70   3.67 0.5857
WVFGRD96   23.0   330    65    70   3.68 0.5828
WVFGRD96   24.0   325    65    65   3.69 0.5794
WVFGRD96   25.0   325    65    65   3.69 0.5754
WVFGRD96   26.0   325    65    65   3.70 0.5707
WVFGRD96   27.0   325    65    65   3.71 0.5653
WVFGRD96   28.0   325    65    65   3.71 0.5590
WVFGRD96   29.0   320    65    65   3.71 0.5523

The best solution is

WVFGRD96   19.0   335    60    70   3.65 0.5889

The mechanism correspond to the best fit is
Figure 1. Waveform inversion focal mechanism

The best fit as a function of depth is given in the following figure:

Figure 2. Depth sensitivity for waveform mechanism

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 component is plotted to the same scale and peak amplitudes are indicated by the numbers to the left of each trace. A pair of numbers is given in black at the right of each predicted traces. The upper number 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 lower number gives the percentage of variance reduction to characterize the individual goodness of fit (100% indicates a perfect fit).

The bandpass filter used in the processing and for the display was

cut o DIST/3.3 -30 o DIST/3.3 +60
rtr
taper w 0.1
hp c 0.03 n 3 
lp c 0.07 n 3 
br c 0.12 0.25 n 4 p 2
Figure 3. Waveform comparison for selected depth. Red: observed; Blue - predicted. The time shift with respect to the model prediction is indicated. The percent of fit is also indicated.
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.

A check on the assumed source location is possible by looking at the time shifts between the observed and predicted traces. The time shifts for waveform matching arise for several reasons:

Assuming only a mislocation, the time shifts are fit to a functional form:

 Time_shift = A + B cos Azimuth + C Sin Azimuth

The time shifts for this inversion lead to the next figure:

The derived shift in origin time and epicentral coordinates are given at the bottom of the figure.

Discussion

Acknowledgements

Thanks also to the many seismic network operators whose dedication make this effort possible: University of Nevada Reno, University of Alaska, University of Washington, Oregon State University, University of Utah, Montana Bureas of Mines, UC Berkely, Caltech, UC San Diego, Saint Louis University, University of Memphis, Lamont Doherty Earth Observatory, the Iris stations and the Transportable Array of EarthScope.

Velocity Model

The CUS model 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 

Quality Control

Here we tabulate the reasons for not using certain digital data sets

The following stations did not have a valid response files:

Last Changed Mon Dec 7 00:00:03 CST 2015