Location

2013/11/12 18:16:48 63.079 -150.930 134.0 4.7 Alaska

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  2013/11/12 18:16:48:0  63.08 -150.93 134.0 4.7 Alaska
 
 Stations used:
   AK.BAL AK.BPAW AK.BRLK AK.BRSE AK.BWN AK.CAST AK.CCB 
   AK.COLD AK.DHY AK.EYAK AK.FID AK.GLB AK.GLI AK.HIN AK.KNK 
   AK.KTH AK.MCAR AK.MCK AK.MLY AK.NEA AK.PAX AK.PPLA AK.RC01 
   AK.RND AK.SAW AK.SCM AK.SGA AK.SLK AK.SSN AK.SWD AK.TRF 
   AK.WAT1 AK.WAT2 AK.WAT4 AK.WAT5 AK.WAT6 AK.WAT7 AK.WRH 
   AT.SVW2 IM.IL31 IU.COLA TA.HDA TA.TCOL TA.TOLK YE.PIC1 
   YE.PIC2 YE.PIC3 
 
 Filtering commands used:
   cut a -30 a 120
   rtr
   taper w 0.1
   hp c 0.02 n 3 
   lp c 0.10 n 3 
 
 Best Fitting Double Couple
  Mo = 1.23e+23 dyne-cm
  Mw = 4.66 
  Z  = 132 km
  Plane   Strike  Dip  Rake
   NP1      240    82   -96
   NP2       95    10   -55
  Principal Axes:
   Axis    Value   Plunge  Azimuth
    T   1.23e+23     37     335
    N   0.00e+00      6     240
    P  -1.23e+23     53     143

 Moment Tensor: (dyne-cm)
    Component   Value
       Mxx     3.63e+22
       Mxy    -9.07e+21
       Mxz     1.00e+23
       Myy    -1.87e+21
       Myz    -6.10e+22
       Mzz    -3.45e+22
                                                     
                                                     
                                                     
                                                     
                     ##############                  
                 ######################              
              ############################           
             ########   ###################          
           ########## T #####################        
          ###########   #####################-       
         ###############################-------      
        ############################------------     
        ########################----------------     
       ######################--------------------    
       ##################------------------------    
       ###############---------------------------    
       -############----------------------------#    
        #########-------------------------------     
        -######------------------   -----------#     
         -##--------------------- P ----------#      
          #----------------------   ---------#       
           ##-------------------------------#        
             ##---------------------------#          
              ###----------------------###           
                 ####--------------####              
                     ##############                  
                                                     
                                                     
                                                     
 Global CMT Convention Moment Tensor:
      R          T          P
 -3.45e+22   1.00e+23   6.10e+22 
  1.00e+23   3.63e+22   9.07e+21 
  6.10e+22   9.07e+21  -1.87e+21 


Details of the solution is found at

http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20131112181648/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 = 95
      DIP = 10
     RAKE = -55
       MW = 4.66
       HS = 132.0

The NDK file is 20131112181648.ndk The waveform inversion is preferred.

Moment Tensor Comparison

The following compares this source inversion to others
SLU
 USGS/SLU Moment Tensor Solution
 ENS  2013/11/12 18:16:48:0  63.08 -150.93 134.0 4.7 Alaska
 
 Stations used:
   AK.BAL AK.BPAW AK.BRLK AK.BRSE AK.BWN AK.CAST AK.CCB 
   AK.COLD AK.DHY AK.EYAK AK.FID AK.GLB AK.GLI AK.HIN AK.KNK 
   AK.KTH AK.MCAR AK.MCK AK.MLY AK.NEA AK.PAX AK.PPLA AK.RC01 
   AK.RND AK.SAW AK.SCM AK.SGA AK.SLK AK.SSN AK.SWD AK.TRF 
   AK.WAT1 AK.WAT2 AK.WAT4 AK.WAT5 AK.WAT6 AK.WAT7 AK.WRH 
   AT.SVW2 IM.IL31 IU.COLA TA.HDA TA.TCOL TA.TOLK YE.PIC1 
   YE.PIC2 YE.PIC3 
 
 Filtering commands used:
   cut a -30 a 120
   rtr
   taper w 0.1
   hp c 0.02 n 3 
   lp c 0.10 n 3 
 
 Best Fitting Double Couple
  Mo = 1.23e+23 dyne-cm
  Mw = 4.66 
  Z  = 132 km
  Plane   Strike  Dip  Rake
   NP1      240    82   -96
   NP2       95    10   -55
  Principal Axes:
   Axis    Value   Plunge  Azimuth
    T   1.23e+23     37     335
    N   0.00e+00      6     240
    P  -1.23e+23     53     143

 Moment Tensor: (dyne-cm)
    Component   Value
       Mxx     3.63e+22
       Mxy    -9.07e+21
       Mxz     1.00e+23
       Myy    -1.87e+21
       Myz    -6.10e+22
       Mzz    -3.45e+22
                                                     
                                                     
                                                     
                                                     
                     ##############                  
                 ######################              
              ############################           
             ########   ###################          
           ########## T #####################        
          ###########   #####################-       
         ###############################-------      
        ############################------------     
        ########################----------------     
       ######################--------------------    
       ##################------------------------    
       ###############---------------------------    
       -############----------------------------#    
        #########-------------------------------     
        -######------------------   -----------#     
         -##--------------------- P ----------#      
          #----------------------   ---------#       
           ##-------------------------------#        
             ##---------------------------#          
              ###----------------------###           
                 ####--------------####              
                     ##############                  
                                                     
                                                     
                                                     
 Global CMT Convention Moment Tensor:
      R          T          P
 -3.45e+22   1.00e+23   6.10e+22 
  1.00e+23   3.63e+22   9.07e+21 
  6.10e+22   9.07e+21  -1.87e+21 


Details of the solution is found at

http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20131112181648/index.html
	

Magnitudes

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 a -30 a 120
rtr
taper w 0.1
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    2.0   335    80   -15   3.65 0.2201
WVFGRD96    4.0   160    75    10   3.77 0.2696
WVFGRD96    6.0   340    70    -5   3.85 0.3048
WVFGRD96    8.0   340    70    10   3.94 0.3370
WVFGRD96   10.0   340    75     5   3.99 0.3504
WVFGRD96   12.0   340    75    -5   4.03 0.3502
WVFGRD96   14.0   340    80   -10   4.05 0.3422
WVFGRD96   16.0   340    80   -10   4.08 0.3290
WVFGRD96   18.0   340    80   -10   4.09 0.3136
WVFGRD96   20.0   185    70    10   4.09 0.3025
WVFGRD96   22.0   185    70     5   4.10 0.2936
WVFGRD96   24.0    65    80   -10   4.14 0.2908
WVFGRD96   26.0    65    80    -5   4.15 0.3024
WVFGRD96   28.0    65    80    -5   4.17 0.3126
WVFGRD96   30.0    70    80     5   4.19 0.3193
WVFGRD96   32.0    70    80    10   4.21 0.3291
WVFGRD96   34.0    70    80    10   4.22 0.3361
WVFGRD96   36.0    70    75    10   4.24 0.3374
WVFGRD96   38.0    70    80    10   4.27 0.3448
WVFGRD96   40.0    70    70    10   4.33 0.3576
WVFGRD96   42.0    70    75    10   4.35 0.3645
WVFGRD96   44.0    70    75    15   4.38 0.3716
WVFGRD96   46.0    70    75    15   4.40 0.3781
WVFGRD96   48.0    70    75    15   4.42 0.3840
WVFGRD96   50.0    75    70    25   4.44 0.3926
WVFGRD96   52.0    75    70    25   4.46 0.4029
WVFGRD96   54.0    75    70    25   4.47 0.4127
WVFGRD96   56.0    75    70    25   4.48 0.4217
WVFGRD96   58.0    75    75    30   4.49 0.4314
WVFGRD96   60.0    75    75    30   4.50 0.4418
WVFGRD96   62.0    75    75    30   4.51 0.4492
WVFGRD96   64.0    75    75    30   4.51 0.4571
WVFGRD96   66.0    75    75    30   4.52 0.4621
WVFGRD96   68.0    75    75    30   4.52 0.4668
WVFGRD96   70.0    70    90    75   4.56 0.4665
WVFGRD96   72.0    70    90    80   4.57 0.4853
WVFGRD96   74.0   245    90   -80   4.57 0.5034
WVFGRD96   76.0    65    90    80   4.58 0.5212
WVFGRD96   78.0    65    90    80   4.58 0.5370
WVFGRD96   80.0    65    90    80   4.59 0.5499
WVFGRD96   82.0    65    90    85   4.59 0.5628
WVFGRD96   84.0    65    90    85   4.60 0.5753
WVFGRD96   86.0    65    90    85   4.60 0.5855
WVFGRD96   88.0   240    85   -85   4.61 0.5983
WVFGRD96   90.0    40     5  -110   4.62 0.6086
WVFGRD96   92.0   210    -5    60   4.62 0.6187
WVFGRD96   94.0   160    -5     5   4.61 0.6196
WVFGRD96   96.0   240    85   -90   4.63 0.6345
WVFGRD96   98.0   210    -5    60   4.63 0.6424
WVFGRD96  100.0    80     5   -70   4.63 0.6483
WVFGRD96  102.0    90     5   -60   4.63 0.6540
WVFGRD96  104.0    90     5   -60   4.64 0.6588
WVFGRD96  106.0    90     5   -60   4.64 0.6654
WVFGRD96  108.0    90     5   -60   4.64 0.6666
WVFGRD96  110.0    90     5   -60   4.64 0.6728
WVFGRD96  112.0    90     5   -60   4.64 0.6732
WVFGRD96  114.0    80     5   -70   4.64 0.6785
WVFGRD96  116.0   100    10   -50   4.65 0.6801
WVFGRD96  118.0   100    10   -50   4.66 0.6847
WVFGRD96  120.0   100    10   -50   4.66 0.6883
WVFGRD96  122.0   100    10   -50   4.66 0.6903
WVFGRD96  124.0   100    10   -50   4.66 0.6932
WVFGRD96  126.0   100    10   -50   4.66 0.6931
WVFGRD96  128.0   100    10   -50   4.66 0.6976
WVFGRD96  130.0    95    10   -55   4.66 0.6960
WVFGRD96  132.0    95    10   -55   4.66 0.6990
WVFGRD96  134.0    95    10   -55   4.67 0.6971
WVFGRD96  136.0    95    10   -55   4.67 0.6987
WVFGRD96  138.0    95    10   -55   4.67 0.6970
WVFGRD96  140.0    95    10   -55   4.67 0.6967
WVFGRD96  142.0    95    10   -55   4.67 0.6958
WVFGRD96  144.0    95    10   -55   4.67 0.6936
WVFGRD96  146.0   100    10   -50   4.67 0.6903
WVFGRD96  148.0   100    10   -50   4.67 0.6904

The best solution is

WVFGRD96  132.0    95    10   -55   4.66 0.6990

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 a -30 a 120
rtr
taper w 0.1
hp c 0.02 n 3 
lp c 0.10 n 3 
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 WUS model used for the waveform synthetic seismograms and for the surface wave eigenfunctions and dispersion is as follows:

MODEL.01
Model after     8 iterations
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
     1.9000     3.4065     2.0089     2.2150  0.302E-02  0.679E-02   0.00       0.00       1.00       1.00    
     6.1000     5.5445     3.2953     2.6089  0.349E-02  0.784E-02   0.00       0.00       1.00       1.00    
    13.0000     6.2708     3.7396     2.7812  0.212E-02  0.476E-02   0.00       0.00       1.00       1.00    
    19.0000     6.4075     3.7680     2.8223  0.111E-02  0.249E-02   0.00       0.00       1.00       1.00    
     0.0000     7.9000     4.6200     3.2760  0.164E-10  0.370E-10   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 00:23:43 CST 2015