Location

2010/11/14 04:59:49 63.1990 -150.5960 126.0 4.70

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  2010/11/14 04:59:49:0  63.20 -150.60 126.0 4.7 
 
 Stations used:
   AK.BPAW AK.BWN AK.CAST AK.DHY AK.KTH AK.MCK AK.MDM AK.PAX 
   AK.PPLA AK.RND AK.SAW AK.SCM AK.SSN AK.TRF AK.WRH AT.PMR 
   IU.COLA 
 
 Filtering commands used:
   hp c 0.02 n 3
   lp c 0.0625 n 3
 
 Best Fitting Double Couple
  Mo = 1.07e+23 dyne-cm
  Mw = 4.62 
  Z  = 134 km
  Plane   Strike  Dip  Rake
   NP1        9    77   128
   NP2      115    40    20
  Principal Axes:
   Axis    Value   Plunge  Azimuth
    T   1.07e+23     44     317
    N   0.00e+00     37     180
    P  -1.07e+23     23      71

 Moment Tensor: (dyne-cm)
    Component   Value
       Mxx     1.99e+22
       Mxy    -5.54e+22
       Mxz     2.68e+22
       Myy    -5.60e+22
       Myz    -7.26e+22
       Mzz     3.61e+22
                                                     
                                                     
                                                     
                                                     
                     ###########---                  
                 ###############-------              
              ##################----------           
             ###################-----------          
           #####################-------------        
          #########   ##########--------------       
         ########## T ##########---------------      
        -##########   ##########----------   ---     
        --######################---------- P ---     
       ---######################----------   ----    
       ----####################------------------    
       -----###################------------------    
       ------##################------------------    
        ------################------------------     
        --------##############------------------     
         ---------############-----------------      
          -----------########----------------#       
           --------------###--------------###        
             ---------------###############          
              -------------###############           
                 ---------#############              
                     ----##########                  
                                                     
                                                     
                                                     
 Global CMT Convention Moment Tensor:
      R          T          P
  3.61e+22   2.68e+22   7.26e+22 
  2.68e+22   1.99e+22   5.54e+22 
  7.26e+22   5.54e+22  -5.60e+22 


Details of the solution is found at

http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20101114045949/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 = 115
      DIP = 40
     RAKE = 20
       MW = 4.62
       HS = 134.0

The waveform inversion is preferred.

Moment Tensor Comparison

The following compares this source inversion to others
SLU
 USGS/SLU Moment Tensor Solution
 ENS  2010/11/14 04:59:49:0  63.20 -150.60 126.0 4.7 
 
 Stations used:
   AK.BPAW AK.BWN AK.CAST AK.DHY AK.KTH AK.MCK AK.MDM AK.PAX 
   AK.PPLA AK.RND AK.SAW AK.SCM AK.SSN AK.TRF AK.WRH AT.PMR 
   IU.COLA 
 
 Filtering commands used:
   hp c 0.02 n 3
   lp c 0.0625 n 3
 
 Best Fitting Double Couple
  Mo = 1.07e+23 dyne-cm
  Mw = 4.62 
  Z  = 134 km
  Plane   Strike  Dip  Rake
   NP1        9    77   128
   NP2      115    40    20
  Principal Axes:
   Axis    Value   Plunge  Azimuth
    T   1.07e+23     44     317
    N   0.00e+00     37     180
    P  -1.07e+23     23      71

 Moment Tensor: (dyne-cm)
    Component   Value
       Mxx     1.99e+22
       Mxy    -5.54e+22
       Mxz     2.68e+22
       Myy    -5.60e+22
       Myz    -7.26e+22
       Mzz     3.61e+22
                                                     
                                                     
                                                     
                                                     
                     ###########---                  
                 ###############-------              
              ##################----------           
             ###################-----------          
           #####################-------------        
          #########   ##########--------------       
         ########## T ##########---------------      
        -##########   ##########----------   ---     
        --######################---------- P ---     
       ---######################----------   ----    
       ----####################------------------    
       -----###################------------------    
       ------##################------------------    
        ------################------------------     
        --------##############------------------     
         ---------############-----------------      
          -----------########----------------#       
           --------------###--------------###        
             ---------------###############          
              -------------###############           
                 ---------#############              
                     ----##########                  
                                                     
                                                     
                                                     
 Global CMT Convention Moment Tensor:
      R          T          P
  3.61e+22   2.68e+22   7.26e+22 
  2.68e+22   1.99e+22   5.54e+22 
  7.26e+22   5.54e+22  -5.60e+22 


Details of the solution is found at

http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20101114045949/index.html
	

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 0.0625 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  110.0   120    40    25   4.58 0.5118
WVFGRD96  111.0   120    40    25   4.58 0.5146
WVFGRD96  112.0   120    40    25   4.58 0.5171
WVFGRD96  113.0   120    40    25   4.58 0.5196
WVFGRD96  114.0   120    40    25   4.58 0.5217
WVFGRD96  115.0   120    40    25   4.58 0.5235
WVFGRD96  116.0   120    40    25   4.59 0.5260
WVFGRD96  117.0   120    40    25   4.59 0.5275
WVFGRD96  118.0   120    40    25   4.59 0.5293
WVFGRD96  119.0   120    40    25   4.59 0.5313
WVFGRD96  120.0   120    40    25   4.59 0.5319
WVFGRD96  121.0   120    40    25   4.59 0.5336
WVFGRD96  122.0   120    40    25   4.59 0.5352
WVFGRD96  123.0   115    40    20   4.61 0.5360
WVFGRD96  124.0   115    40    20   4.61 0.5372
WVFGRD96  125.0   115    40    20   4.61 0.5384
WVFGRD96  126.0   115    40    20   4.61 0.5387
WVFGRD96  127.0   115    40    20   4.61 0.5400
WVFGRD96  128.0   115    40    20   4.61 0.5410
WVFGRD96  129.0   115    40    20   4.61 0.5408
WVFGRD96  130.0   115    40    20   4.61 0.5412
WVFGRD96  131.0   115    40    20   4.62 0.5419
WVFGRD96  132.0   115    40    20   4.62 0.5419
WVFGRD96  133.0   115    40    20   4.62 0.5419
WVFGRD96  134.0   115    40    20   4.62 0.5423
WVFGRD96  135.0   115    40    20   4.62 0.5419
WVFGRD96  136.0   115    40    20   4.62 0.5413
WVFGRD96  137.0   115    40    20   4.62 0.5416
WVFGRD96  138.0   115    40    20   4.62 0.5414
WVFGRD96  139.0   115    40    20   4.62 0.5405

The best solution is

WVFGRD96  134.0   115    40    20   4.62 0.5423

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 0.0625 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.

Discussion

The Future

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.

Acknowledgements

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.

Velocity Model

The WUS 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:

DATE=Thu Dec 30 09:40:35 MST 2010

Last Changed 2010/11/14