Location

2014/01/10 04:17:37 62.247 -149.301 39.9 3.8 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  2014/01/10 04:17:37:0  62.25 -149.30  39.9 3.8 Alaska
 
 Stations used:
   AK.DHY AK.FIRE AK.KNK AK.KTH AK.PAX AK.PPLA AK.RND AK.SAW 
   AK.SKN AK.SSN AK.WAT1 AK.WAT4 AK.WAT6 AK.WAT7 AT.PMR 
 
 Filtering commands used:
   cut a -30 a 180
   rtr
   taper w 0.1
   hp c 0.02 n 3 
   lp c 0.06 n 3 
 
 Best Fitting Double Couple
  Mo = 1.40e+22 dyne-cm
  Mw = 4.03 
  Z  = 60 km
  Plane   Strike  Dip  Rake
   NP1      210    60   -75
   NP2        2    33   -114
  Principal Axes:
   Axis    Value   Plunge  Azimuth
    T   1.40e+22     14     289
    N   0.00e+00     13      22
    P  -1.40e+22     71     154

 Moment Tensor: (dyne-cm)
    Component   Value
       Mxx     2.10e+20
       Mxy    -3.49e+21
       Mxz     4.94e+21
       Myy     1.15e+22
       Myz    -4.94e+21
       Mzz    -1.17e+22
                                                     
                                                     
                                                     
                                                     
                     ###########---                  
                 #################---##              
              ###################---######           
             #################--------#####          
           #################-----------######        
          ################--------------######       
            ############-----------------######      
        # T ###########------------------#######     
        #   ##########--------------------######     
       ##############---------------------#######    
       #############----------------------#######    
       ############-----------------------#######    
       ###########-----------   ----------#######    
        ##########----------- P ---------#######     
        #########------------   ---------#######     
         ########-----------------------#######      
          #######-----------------------######       
           ######----------------------######        
             ####--------------------######          
              ###-------------------######           
                 -----------------#####              
                     ----------####                  
                                                     
                                                     
                                                     
 Global CMT Convention Moment Tensor:
      R          T          P
 -1.17e+22   4.94e+21   4.94e+21 
  4.94e+21   2.10e+20   3.49e+21 
  4.94e+21   3.49e+21   1.15e+22 


Details of the solution is found at

http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20140110041737/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 = 210
      DIP = 60
     RAKE = -75
       MW = 4.03
       HS = 60.0

The NDK file is 20140110041737.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  2014/01/10 04:17:37:0  62.25 -149.30  39.9 3.8 Alaska
 
 Stations used:
   AK.DHY AK.FIRE AK.KNK AK.KTH AK.PAX AK.PPLA AK.RND AK.SAW 
   AK.SKN AK.SSN AK.WAT1 AK.WAT4 AK.WAT6 AK.WAT7 AT.PMR 
 
 Filtering commands used:
   cut a -30 a 180
   rtr
   taper w 0.1
   hp c 0.02 n 3 
   lp c 0.06 n 3 
 
 Best Fitting Double Couple
  Mo = 1.40e+22 dyne-cm
  Mw = 4.03 
  Z  = 60 km
  Plane   Strike  Dip  Rake
   NP1      210    60   -75
   NP2        2    33   -114
  Principal Axes:
   Axis    Value   Plunge  Azimuth
    T   1.40e+22     14     289
    N   0.00e+00     13      22
    P  -1.40e+22     71     154

 Moment Tensor: (dyne-cm)
    Component   Value
       Mxx     2.10e+20
       Mxy    -3.49e+21
       Mxz     4.94e+21
       Myy     1.15e+22
       Myz    -4.94e+21
       Mzz    -1.17e+22
                                                     
                                                     
                                                     
                                                     
                     ###########---                  
                 #################---##              
              ###################---######           
             #################--------#####          
           #################-----------######        
          ################--------------######       
            ############-----------------######      
        # T ###########------------------#######     
        #   ##########--------------------######     
       ##############---------------------#######    
       #############----------------------#######    
       ############-----------------------#######    
       ###########-----------   ----------#######    
        ##########----------- P ---------#######     
        #########------------   ---------#######     
         ########-----------------------#######      
          #######-----------------------######       
           ######----------------------######        
             ####--------------------######          
              ###-------------------######           
                 -----------------#####              
                     ----------####                  
                                                     
                                                     
                                                     
 Global CMT Convention Moment Tensor:
      R          T          P
 -1.17e+22   4.94e+21   4.94e+21 
  4.94e+21   2.10e+20   3.49e+21 
  4.94e+21   3.49e+21   1.15e+22 


Details of the solution is found at

http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20140110041737/index.html
	
Moment
1.51e+15 N-m
Magnitude
4.1
Percent DC
80%
Depth
59.0 km
Updated
2014-01-10 15:02:47 UTC
Author
us
Catalog
ak
Contributor
us
Code
us_c000lztg_mwr
Principal Axes

Axis	Value	Plunge	Azimuth
T	1.437	14	289
N	0.137	13	23
P	-1.573	70	155
Nodal Planes

Plane	Strike	Dip	Rake
NP1	210	60	-75
NP2	1	33	-115
        

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 180
rtr
taper w 0.1
hp c 0.02 n 3 
lp c 0.06 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     5    45    90   3.23 0.1844
WVFGRD96    1.0   185    45    90   3.26 0.1807
WVFGRD96    2.0     5    45    90   3.38 0.2391
WVFGRD96    3.0     5    45    90   3.43 0.2365
WVFGRD96    4.0   100    80    25   3.39 0.2221
WVFGRD96    5.0    95    90    30   3.42 0.2309
WVFGRD96    6.0    95    90    30   3.44 0.2406
WVFGRD96    7.0   275    85   -30   3.46 0.2522
WVFGRD96    8.0   260    80   -30   3.49 0.2604
WVFGRD96    9.0   255    70   -30   3.51 0.2711
WVFGRD96   10.0   225    75   -45   3.50 0.2811
WVFGRD96   11.0   225    75   -45   3.51 0.2943
WVFGRD96   12.0   225    70   -45   3.53 0.3066
WVFGRD96   13.0   225    70   -45   3.54 0.3177
WVFGRD96   14.0   225    70   -40   3.55 0.3289
WVFGRD96   15.0   225    70   -40   3.56 0.3395
WVFGRD96   16.0   225    70   -40   3.57 0.3490
WVFGRD96   17.0   225    70   -40   3.58 0.3587
WVFGRD96   18.0   225    70   -40   3.59 0.3679
WVFGRD96   19.0   225    70   -40   3.60 0.3766
WVFGRD96   20.0   225    70   -40   3.61 0.3848
WVFGRD96   21.0   225    70   -40   3.62 0.3914
WVFGRD96   22.0   225    70   -45   3.64 0.3987
WVFGRD96   23.0   225    70   -45   3.64 0.4057
WVFGRD96   24.0   225    70   -45   3.65 0.4120
WVFGRD96   25.0   225    70   -45   3.66 0.4180
WVFGRD96   26.0   225    70   -45   3.67 0.4234
WVFGRD96   27.0   225    70   -45   3.68 0.4281
WVFGRD96   28.0   225    70   -45   3.69 0.4320
WVFGRD96   29.0   225    70   -45   3.69 0.4355
WVFGRD96   30.0   225    70   -45   3.70 0.4384
WVFGRD96   31.0   225    70   -45   3.71 0.4405
WVFGRD96   32.0   225    70   -45   3.72 0.4418
WVFGRD96   33.0   225    70   -45   3.72 0.4427
WVFGRD96   34.0   220    70   -50   3.73 0.4441
WVFGRD96   35.0   220    70   -50   3.74 0.4455
WVFGRD96   36.0   220    70   -50   3.75 0.4471
WVFGRD96   37.0   220    70   -50   3.75 0.4489
WVFGRD96   38.0   220    70   -50   3.76 0.4502
WVFGRD96   39.0   220    65   -50   3.78 0.4517
WVFGRD96   40.0   220    70   -60   3.87 0.4504
WVFGRD96   41.0   220    70   -60   3.88 0.4545
WVFGRD96   42.0   215    65   -65   3.90 0.4595
WVFGRD96   43.0   220    65   -60   3.90 0.4651
WVFGRD96   44.0   215    60   -65   3.92 0.4710
WVFGRD96   45.0   215    60   -65   3.93 0.4776
WVFGRD96   46.0   215    60   -65   3.94 0.4840
WVFGRD96   47.0   215    60   -65   3.95 0.4896
WVFGRD96   48.0   215    60   -65   3.95 0.4945
WVFGRD96   49.0   210    60   -70   3.97 0.5007
WVFGRD96   50.0   210    60   -70   3.97 0.5068
WVFGRD96   51.0   210    60   -70   3.98 0.5125
WVFGRD96   52.0   210    60   -70   3.99 0.5173
WVFGRD96   53.0   210    60   -75   4.00 0.5219
WVFGRD96   54.0   210    60   -75   4.01 0.5260
WVFGRD96   55.0   210    60   -75   4.01 0.5290
WVFGRD96   56.0   210    60   -75   4.02 0.5315
WVFGRD96   57.0   210    60   -75   4.02 0.5334
WVFGRD96   58.0   210    60   -75   4.02 0.5346
WVFGRD96   59.0   210    60   -75   4.03 0.5350
WVFGRD96   60.0   210    60   -75   4.03 0.5351
WVFGRD96   61.0   210    60   -75   4.03 0.5345
WVFGRD96   62.0   210    60   -75   4.03 0.5330
WVFGRD96   63.0   210    60   -75   4.04 0.5312
WVFGRD96   64.0   210    60   -75   4.04 0.5288
WVFGRD96   65.0   210    60   -75   4.04 0.5255
WVFGRD96   66.0   210    60   -75   4.04 0.5222
WVFGRD96   67.0   210    60   -75   4.04 0.5185
WVFGRD96   68.0   210    60   -75   4.04 0.5136
WVFGRD96   69.0   210    60   -75   4.04 0.5095
WVFGRD96   70.0   215    65   -75   4.04 0.5045
WVFGRD96   71.0   215    65   -75   4.04 0.5002
WVFGRD96   72.0   215    65   -70   4.03 0.4961
WVFGRD96   73.0   215    65   -70   4.03 0.4916
WVFGRD96   74.0   215    65   -70   4.03 0.4867
WVFGRD96   75.0   210    65   -75   4.04 0.4821
WVFGRD96   76.0   210    65   -75   4.03 0.4780
WVFGRD96   77.0   210    65   -75   4.03 0.4740
WVFGRD96   78.0   210    65   -75   4.03 0.4695
WVFGRD96   79.0   215    70   -80   4.04 0.4655
WVFGRD96   80.0   215    70   -80   4.04 0.4621
WVFGRD96   81.0   215    70   -80   4.04 0.4586
WVFGRD96   82.0   215    70   -80   4.04 0.4550
WVFGRD96   83.0   215    70   -80   4.04 0.4511
WVFGRD96   84.0   215    70   -80   4.04 0.4474
WVFGRD96   85.0   215    70   -80   4.04 0.4432
WVFGRD96   86.0   215    70   -80   4.04 0.4394
WVFGRD96   87.0   215    70   -80   4.04 0.4350
WVFGRD96   88.0   215    70   -80   4.03 0.4311
WVFGRD96   89.0   215    70   -80   4.03 0.4268
WVFGRD96   90.0   215    70   -80   4.03 0.4227
WVFGRD96   91.0   215    70   -80   4.03 0.4184
WVFGRD96   92.0   220    70   -75   4.03 0.4146
WVFGRD96   93.0   220    70   -75   4.03 0.4106
WVFGRD96   94.0   210    65   -80   4.03 0.4076
WVFGRD96   95.0   210    65   -80   4.03 0.4044
WVFGRD96   96.0   210    65   -80   4.02 0.4018
WVFGRD96   97.0   210    65   -80   4.02 0.3987
WVFGRD96   98.0   210    65   -80   4.02 0.3959
WVFGRD96   99.0   210    65   -80   4.02 0.3929

The best solution is

WVFGRD96   60.0   210    60   -75   4.03 0.5351

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 180
rtr
taper w 0.1
hp c 0.02 n 3 
lp c 0.06 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 00:09:30 CST 2015