Location

2013/05/17 13:43:22 45.819 -76.377 5.0 5.0 Ontario

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  2013/05/17 13:43:22:0  45.82  -76.38   5.0 5.0 Ontario
 
 Stations used:
   CN.A16 CN.A21 CN.A54 CN.A61 CN.A64 CN.ACTO CN.ALFO CN.BANO 
   CN.BMRO CN.BRCO CN.BUKO CN.BWLO CN.CHGQ CN.DELO CN.DMCQ 
   CN.DRCO CN.GAC CN.KAPO CN.KGNO CN.KILO CN.KLBO CN.LATQ 
   CN.LMQ CN.LSQQ CN.MATQ CN.MEDO CN.MNTQ CN.ORIO CN.OTT 
   CN.PECO CN.PKRO CN.PLVO CN.SADO CN.STCO CN.SUNO CN.TOBO 
   CN.TORO CN.VABQ CN.VLDQ IU.HRV IU.SSPA LD.ACCN LD.ALLY 
   LD.BRNJ LD.FRNY LD.KSCT LD.KSPA LD.LUPA LD.NCB LD.ODNJ 
   LD.PAL LD.WVNY NE.BCX NE.HNH NE.QUA2 NE.TRY NE.VT1 NE.WES 
   NE.WSPT NE.WVL NE.YLE TA.D47A TA.D48A TA.D49A TA.D51A 
   TA.D52A TA.D54A TA.E46A TA.E47A TA.E50A TA.E51A TA.E52A 
   TA.E53A TA.E54A TA.F48A TA.F49A TA.F51A TA.F52A TA.G47A 
   TA.G53A TA.H48A TA.H52A TA.H55A TA.H56A TA.I47A TA.I49A 
   TA.I51A TA.I52A TA.I53A TA.I55A TA.J48A TA.J52A TA.J54A 
   TA.J55A TA.K50A TA.K51A TA.K52A TA.K55A TA.L53A TA.L55A 
   TA.M52A TA.M53A TA.M54A TA.M55A TA.M65A TA.N53A TA.N54A 
   TA.N55A TA.N59A TA.O56A TA.P60A US.BINY US.ERPA US.GLMI 
   US.LBNH US.LONY US.PKME 
 
 Filtering commands used:
   hp c 0.02 n 3
   lp c 0.10 n 3
 
 Best Fitting Double Couple
  Mo = 6.84e+22 dyne-cm
  Mw = 4.49 
  Z  = 13 km
  Plane   Strike  Dip  Rake
   NP1      135    50    65
   NP2      351    46   117
  Principal Axes:
   Axis    Value   Plunge  Azimuth
    T   6.84e+22     71     338
    N   0.00e+00     19     152
    P  -6.84e+22      2     242

 Moment Tensor: (dyne-cm)
    Component   Value
       Mxx    -8.38e+21
       Mxy    -3.05e+22
       Mxz     2.07e+22
       Myy    -5.27e+22
       Myz    -5.53e+21
       Mzz     6.10e+22
                                                     
                                                     
                                                     
                                                     
                     ######--------                  
                 #############---------              
              ##################----------           
             #####################---------          
           --######################----------        
          ---#######################----------       
         ----########################----------      
        -----############   ##########----------     
        ------########### T ##########----------     
       -------###########   ###########----------    
       --------########################----------    
       ---------#######################----------    
       ----------######################----------    
        -----------####################---------     
        ------------###################---------     
            ----------#################--------      
          P ------------##############--------       
            ---------------###########-------        
             ------------------######------          
              ----------------------######           
                 -----------------#####              
                     ------------##                  
                                                     
                                                     
                                                     
 Global CMT Convention Moment Tensor:
      R          T          P
  6.10e+22   2.07e+22   5.53e+21 
  2.07e+22  -8.38e+21   3.05e+22 
  5.53e+21   3.05e+22  -5.27e+22 


Details of the solution is found at

http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20130517134322/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 = 135
      DIP = 50
     RAKE = 65
       MW = 4.49
       HS = 13.0

The NDK file is 20130517134322.ndk The waveform inversion is preferred.

Moment Tensor Comparison

The following compares this source inversion to others
SLU
USGSMT
 USGS/SLU Moment Tensor Solution
 ENS  2013/05/17 13:43:22:0  45.82  -76.38   5.0 5.0 Ontario
 
 Stations used:
   CN.A16 CN.A21 CN.A54 CN.A61 CN.A64 CN.ACTO CN.ALFO CN.BANO 
   CN.BMRO CN.BRCO CN.BUKO CN.BWLO CN.CHGQ CN.DELO CN.DMCQ 
   CN.DRCO CN.GAC CN.KAPO CN.KGNO CN.KILO CN.KLBO CN.LATQ 
   CN.LMQ CN.LSQQ CN.MATQ CN.MEDO CN.MNTQ CN.ORIO CN.OTT 
   CN.PECO CN.PKRO CN.PLVO CN.SADO CN.STCO CN.SUNO CN.TOBO 
   CN.TORO CN.VABQ CN.VLDQ IU.HRV IU.SSPA LD.ACCN LD.ALLY 
   LD.BRNJ LD.FRNY LD.KSCT LD.KSPA LD.LUPA LD.NCB LD.ODNJ 
   LD.PAL LD.WVNY NE.BCX NE.HNH NE.QUA2 NE.TRY NE.VT1 NE.WES 
   NE.WSPT NE.WVL NE.YLE TA.D47A TA.D48A TA.D49A TA.D51A 
   TA.D52A TA.D54A TA.E46A TA.E47A TA.E50A TA.E51A TA.E52A 
   TA.E53A TA.E54A TA.F48A TA.F49A TA.F51A TA.F52A TA.G47A 
   TA.G53A TA.H48A TA.H52A TA.H55A TA.H56A TA.I47A TA.I49A 
   TA.I51A TA.I52A TA.I53A TA.I55A TA.J48A TA.J52A TA.J54A 
   TA.J55A TA.K50A TA.K51A TA.K52A TA.K55A TA.L53A TA.L55A 
   TA.M52A TA.M53A TA.M54A TA.M55A TA.M65A TA.N53A TA.N54A 
   TA.N55A TA.N59A TA.O56A TA.P60A US.BINY US.ERPA US.GLMI 
   US.LBNH US.LONY US.PKME 
 
 Filtering commands used:
   hp c 0.02 n 3
   lp c 0.10 n 3
 
 Best Fitting Double Couple
  Mo = 6.84e+22 dyne-cm
  Mw = 4.49 
  Z  = 13 km
  Plane   Strike  Dip  Rake
   NP1      135    50    65
   NP2      351    46   117
  Principal Axes:
   Axis    Value   Plunge  Azimuth
    T   6.84e+22     71     338
    N   0.00e+00     19     152
    P  -6.84e+22      2     242

 Moment Tensor: (dyne-cm)
    Component   Value
       Mxx    -8.38e+21
       Mxy    -3.05e+22
       Mxz     2.07e+22
       Myy    -5.27e+22
       Myz    -5.53e+21
       Mzz     6.10e+22
                                                     
                                                     
                                                     
                                                     
                     ######--------                  
                 #############---------              
              ##################----------           
             #####################---------          
           --######################----------        
          ---#######################----------       
         ----########################----------      
        -----############   ##########----------     
        ------########### T ##########----------     
       -------###########   ###########----------    
       --------########################----------    
       ---------#######################----------    
       ----------######################----------    
        -----------####################---------     
        ------------###################---------     
            ----------#################--------      
          P ------------##############--------       
            ---------------###########-------        
             ------------------######------          
              ----------------------######           
                 -----------------#####              
                     ------------##                  
                                                     
                                                     
                                                     
 Global CMT Convention Moment Tensor:
      R          T          P
  6.10e+22   2.07e+22   5.53e+21 
  2.07e+22  -8.38e+21   3.05e+22 
  5.53e+21   3.05e+22  -5.27e+22 


Details of the solution is found at

http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20130517134322/index.html
 USGS/SLU Moment Tensor Solution
 ENS  2013/05/17 13:43:23:8  45.75  -76.34  14.5 5.0 Quebec
 
 Stations used:
   CN.A16 CN.A21 CN.A54 CN.A61 CN.A64 CN.ACTO CN.ALFO CN.BANO 
   CN.BMRO CN.BRCO CN.BUKO CN.BWLO CN.CHGQ CN.DELO CN.DMCQ 
   CN.DRCO CN.GAC CN.KAPO CN.KGNO CN.KILO CN.KLBO CN.LATQ 
   CN.LMQ CN.LSQQ CN.MATQ CN.MEDO CN.MNTQ CN.ORIO CN.OTT 
   CN.PECO CN.PKRO CN.PLVO CN.SADO CN.STCO CN.SUNO CN.TOBO 
   CN.TORO CN.VABQ CN.VLDQ IU.HRV IU.SSPA LD.ACCN LD.ALLY 
   LD.BRNJ LD.FRNY LD.KSCT LD.KSPA LD.LUPA LD.NCB LD.ODNJ 
   LD.PAL LD.WVNY NE.BCX NE.HNH NE.QUA2 NE.TRY NE.VT1 NE.WES 
   NE.WSPT NE.WVL NE.YLE TA.D47A TA.D48A TA.D49A TA.D51A 
   TA.D52A TA.D54A TA.E46A TA.E47A TA.E50A TA.E51A TA.E52A 
   TA.E53A TA.E54A TA.F48A TA.F49A TA.F51A TA.F52A TA.G47A 
   TA.G53A TA.H48A TA.H52A TA.H55A TA.H56A TA.I47A TA.I49A 
   TA.I51A TA.I52A TA.I53A TA.I55A TA.J48A TA.J52A TA.J54A 
   TA.J55A TA.K50A TA.K51A TA.K52A TA.K55A TA.L53A TA.L55A 
   TA.M52A TA.M53A TA.M54A TA.M55A TA.M65A TA.N53A TA.N54A 
   TA.N55A TA.N59A TA.O56A TA.P60A US.BINY US.ERPA US.GLMI 
   US.LBNH US.LONY US.PKME 
 
 Filtering commands used:
   hp c 0.02 n 3
   lp c 0.10 n 3
 
 Best Fitting Double Couple
  Mo = 6.84e+22 dyne-cm
  Mw = 4.49 
  Z  = 13 km
  Plane   Strike  Dip  Rake
   NP1      135    50    65
   NP2      351    46   117
  Principal Axes:
   Axis    Value   Plunge  Azimuth
    T   6.84e+22     71     338
    N   0.00e+00     19     152
    P  -6.84e+22      2     242

 Moment Tensor: (dyne-cm)
    Component   Value
       Mxx    -8.38e+21
       Mxy    -3.05e+22
       Mxz     2.07e+22
       Myy    -5.27e+22
       Myz    -5.53e+21
       Mzz     6.10e+22
                                                     
                                                     
                                                     
                                                     
                     ######--------                  
                 #############---------              
              ##################----------           
             #####################---------          
           --######################----------        
          ---#######################----------       
         ----########################----------      
        -----############   ##########----------     
        ------########### T ##########----------     
       -------###########   ###########----------    
       --------########################----------    
       ---------#######################----------    
       ----------######################----------    
        -----------####################---------     
        ------------###################---------     
            ----------#################--------      
          P ------------##############--------       
            ---------------###########-------        
             ------------------######------          
              ----------------------######           
                 -----------------#####              
                     ------------##                  
                                                     
                                                     
                                                     
 Global CMT Convention Moment Tensor:
      R          T          P
  6.10e+22   2.07e+22   5.53e+21 
  2.07e+22  -8.38e+21   3.05e+22 
  5.53e+21   3.05e+22  -5.27e+22 


Details of the solution is found at

http://www.eas.slu.edu/Earthquake_Center/MECH.NA/20130517134323/index.html
	
us usb000gxna-neic-mwr

Type
    Mwr
Moment
    4.97e+15 N-m
Magnitude
    4.4
Percent DC
    92%
Depth
    10.0 km
Author
    neic
Updated
    2013-05-17 14:39:09 UTC

Principal Axes
Axis	Value	Plunge	Azimuth
T	5.064	50°	338°
N	-0.188	38°	134°
P	-4.876	12°	234°
Nodal Planes
Plane	Strike	Dip	Rake
NP1	115°	67°	48°
NP2	1°	47°	147°


        

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:

hp c 0.02 n 3
lp c 0.10 n 3
The results of this grid search from 0.5 to 19 km depth are as follow:

           DEPTH  STK   DIP  RAKE   MW    FIT
WVFGRD96    0.5    75    45   -90   4.29 0.5340
WVFGRD96    1.0    75    45   -90   4.34 0.5375
WVFGRD96    2.0    95    70   -65   4.43 0.5071
WVFGRD96    3.0   100    75   -60   4.40 0.5057
WVFGRD96    4.0   100    75   -60   4.39 0.5134
WVFGRD96    5.0   100    75   -55   4.38 0.5279
WVFGRD96    6.0   160    30   100   4.41 0.5584
WVFGRD96    7.0   135    40    65   4.43 0.6096
WVFGRD96    8.0   135    45    65   4.44 0.6537
WVFGRD96    9.0   130    50    60   4.45 0.6868
WVFGRD96   10.0   135    50    65   4.48 0.7040
WVFGRD96   11.0   135    50    65   4.48 0.7236
WVFGRD96   12.0   135    50    65   4.49 0.7332
WVFGRD96   13.0   135    50    65   4.49 0.7353
WVFGRD96   14.0   130    55    60   4.50 0.7322
WVFGRD96   15.0   130    55    60   4.50 0.7253
WVFGRD96   16.0   130    55    60   4.51 0.7151
WVFGRD96   17.0   130    55    60   4.52 0.7019
WVFGRD96   18.0   130    55    60   4.52 0.6868
WVFGRD96   19.0   130    55    60   4.53 0.6697
WVFGRD96   20.0   135    55    65   4.55 0.6501
WVFGRD96   21.0   130    60    60   4.56 0.6320
WVFGRD96   22.0   130    60    65   4.56 0.6132
WVFGRD96   23.0   130    60    65   4.57 0.5934
WVFGRD96   24.0   130    60    65   4.57 0.5729
WVFGRD96   25.0   130    60    65   4.58 0.5517
WVFGRD96   26.0   130    60    65   4.58 0.5295
WVFGRD96   27.0   125    65    60   4.58 0.5073
WVFGRD96   28.0   125    65    60   4.58 0.4884
WVFGRD96   29.0   125    55    50   4.58 0.4740

The best solution is

WVFGRD96   13.0   135    50    65   4.49 0.7353

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

hp c 0.02 n 3
lp c 0.10 n 3
Figure 3. Waveform comparison for selected depth
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.

Surface-Wave Focal Mechanism

The following figure shows the stations used in the grid search for the best focal mechanism to fit the surface-wave spectral amplitudes of the Love and Rayleigh waves.
Location of broadband stations used to obtain focal mechanism from surface-wave spectral amplitudes

The surface-wave determined focal mechanism is shown here.


  NODAL PLANES 

  
  STK=     134.99
  DIP=      50.00
 RAKE=      64.99
  
             OR
  
  STK=     350.95
  DIP=      46.04
 RAKE=     116.73
 
 
DEPTH = 10.0 km
 
Mw = 4.61
Best Fit 0.8702 - P-T axis plot gives solutions with FIT greater than FIT90

First motion data

The P-wave first motion data for focal mechanism studies are as follow:

Sta Az    Dist   First motion

Surface-wave analysis

Surface wave analysis was performed using codes from Computer Programs in Seismology, specifically the multiple filter analysis program do_mft and the surface-wave radiation pattern search program srfgrd96.

Data preparation

Digital data were collected, instrument response removed and traces converted to Z, R an T components. Multiple filter analysis was applied to the Z and T traces to obtain the Rayleigh- and Love-wave spectral amplitudes, respectively. These were input to the search program which examined all depths between 1 and 25 km and all possible mechanisms.
Best mechanism fit as a function of depth. The preferred depth is given above. Lower hemisphere projection

Pressure-tension axis trends. Since the surface-wave spectra search does not distinguish between P and T axes and since there is a 180 ambiguity in strike, all possible P and T axes are plotted. First motion data and waveforms will be used to select the preferred mechanism. The purpose of this plot is to provide an idea of the possible range of solutions. The P and T-axes for all mechanisms with goodness of fit greater than 0.9 FITMAX (above) are plotted here.


Focal mechanism sensitivity at the preferred depth. The red color indicates a very good fit to the Love and Rayleigh wave radiation patterns. 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. Because of the symmetry of the spectral amplitude rediation patterns, only strikes from 0-180 degrees are sampled.

Love-wave radiation patterns

Rayleigh-wave radiation patterns

Broadband station distribution

The distribution of broadband stations with azimuth and distance is
Listing of broadband stations used

Waveform comparison for this mechanism

Since the analysis of the surface-wave radiation patterns uses only spectral amplitudes and because the surfave-wave radiation patterns have a 180 degree symmetry, each surface-wave solution consists of four possible focal mechanisms corresponding to the interchange of the P- and T-axes and a roation of the mechanism by 180 degrees. To select one mechanism, P-wave first motion can be used. This was not possible in this case because all the P-wave first motions were emergent ( a feature of the P-wave wave takeoff angle, the station location and the mechanism). The other way to select among the mechanisms is to compute forward synthetics and compare the observed and predicted waveforms.

The fits to the waveforms with the given mechanism are show below:

This figure shows the fit to the three components of motion (Z - vertical, R-radial and T - transverse). For each station and component, the observed traces is shown in red and the model predicted trace in blue. The traces represent filtered ground velocity in units of meters/sec (the peak value is printed adjacent to each trace; each pair of traces to plotted to the same scale to emphasize the difference in levels). Both synthetic and observed traces have been filtered using the SAC commands:

hp c 0.02 n 3
lp c 0.10 n 3

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.

Appendix A


Spectra fit plots to each station

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 00:21:12 CST 2015