Location

2010/10/14 12:59:26 60.380 -140.621 5.0 4.00

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  2010/10/14 12:59:26:0  60.38 -140.62   5.0 4.0 
 
 Stations used:
   AK.BAL AK.BESE AK.BMR AK.BRLK AK.CTG AK.DCPH AK.EYAK AK.FID 
   AK.HDA AK.KLU AK.MCK AK.PIN AK.RAG AK.RC01 AK.RND AK.SCM 
   AK.SSN AK.SWD AK.WRH AT.SKAG CN.DAWY CN.DLBC CN.WHY US.EGAK 
 
 Filtering commands used:
   hp c 0.02 n 3
   lp c 0.06 n 3
 
 Best Fitting Double Couple
  Mo = 2.11e+22 dyne-cm
  Mw = 4.15 
  Z  = 13 km
  Plane   Strike  Dip  Rake
   NP1       87    74   -143
   NP2      345    55   -20
  Principal Axes:
   Axis    Value   Plunge  Azimuth
    T   2.11e+22     12     212
    N   0.00e+00     50     107
    P  -2.11e+22     37     311

 Moment Tensor: (dyne-cm)
    Component   Value
       Mxx     8.59e+21
       Mxy     1.58e+22
       Mxz    -1.04e+22
       Myy    -1.80e+21
       Myz     5.34e+21
       Mzz    -6.79e+21
                                                     
                                                     
                                                     
                                                     
                     ---###########                  
                 ----------############              
              ---------------#############           
             ------------------############          
           ---------------------#############        
          -------   -------------#############       
         -------- P --------------#############      
        ---------   ---------------#############     
        ----------------------------############     
       -----------------------------#############    
       ------------------------------###########-    
       ------------------------------########----    
       #####-------------------------#-----------    
        ##############################----------     
        ##############################----------     
         #############################---------      
          ###########################---------       
           ##########################--------        
             ####   #################------          
              ### T ################------           
                    ###############----              
                     #############-                  
                                                     
                                                     
                                                     
 Global CMT Convention Moment Tensor:
      R          T          P
 -6.79e+21  -1.04e+22  -5.34e+21 
 -1.04e+22   8.59e+21  -1.58e+22 
 -5.34e+21  -1.58e+22  -1.80e+21 


Details of the solution is found at

http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20101014125926/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 = 345
      DIP = 55
     RAKE = -20
       MW = 4.15
       HS = 13.0

The waveform inversion is preferred.

Moment Tensor Comparison

The following compares this source inversion to others
SLU
USGSMT
AEIC
 USGS/SLU Moment Tensor Solution
 ENS  2010/10/14 12:59:26:0  60.38 -140.62   5.0 4.0 
 
 Stations used:
   AK.BAL AK.BESE AK.BMR AK.BRLK AK.CTG AK.DCPH AK.EYAK AK.FID 
   AK.HDA AK.KLU AK.MCK AK.PIN AK.RAG AK.RC01 AK.RND AK.SCM 
   AK.SSN AK.SWD AK.WRH AT.SKAG CN.DAWY CN.DLBC CN.WHY US.EGAK 
 
 Filtering commands used:
   hp c 0.02 n 3
   lp c 0.06 n 3
 
 Best Fitting Double Couple
  Mo = 2.11e+22 dyne-cm
  Mw = 4.15 
  Z  = 13 km
  Plane   Strike  Dip  Rake
   NP1       87    74   -143
   NP2      345    55   -20
  Principal Axes:
   Axis    Value   Plunge  Azimuth
    T   2.11e+22     12     212
    N   0.00e+00     50     107
    P  -2.11e+22     37     311

 Moment Tensor: (dyne-cm)
    Component   Value
       Mxx     8.59e+21
       Mxy     1.58e+22
       Mxz    -1.04e+22
       Myy    -1.80e+21
       Myz     5.34e+21
       Mzz    -6.79e+21
                                                     
                                                     
                                                     
                                                     
                     ---###########                  
                 ----------############              
              ---------------#############           
             ------------------############          
           ---------------------#############        
          -------   -------------#############       
         -------- P --------------#############      
        ---------   ---------------#############     
        ----------------------------############     
       -----------------------------#############    
       ------------------------------###########-    
       ------------------------------########----    
       #####-------------------------#-----------    
        ##############################----------     
        ##############################----------     
         #############################---------      
          ###########################---------       
           ##########################--------        
             ####   #################------          
              ### T ################------           
                    ###############----              
                     #############-                  
                                                     
                                                     
                                                     
 Global CMT Convention Moment Tensor:
      R          T          P
 -6.79e+21  -1.04e+22  -5.34e+21 
 -1.04e+22   8.59e+21  -1.58e+22 
 -5.34e+21  -1.58e+22  -1.80e+21 


Details of the solution is found at

http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20101014125926/index.html
	
10/10/14 12:59:28.00
 SOUTHERN YUKON TERRITORY, CANADA
 Epicenter:  60.229 -140.700
 MW 4.3

 USGS/SLU REGIONAL MOMENT TENSOR
 Depth   8         No. of sta: 24
 Moment Tensor;   Scale 10**15 Nm
   Mrr=-1.69       Mtt= 0.62
   Mpp= 1.06       Mrt= 2.58
   Mrp=-2.39       Mtp=-1.18
  Principal axes:
   T  Val=  4.14  Plg=31  Azm= 47
   N       -0.33       4      314
   P       -3.82      59      218

 Best Double Couple:Mo=4.0*10**15
  NP1:Strike=150 Dip=14 Slip= -74
  NP2:       313     76       -94
                                      
               #######                
          #################           
        #####################         
      #########################       
    ##-----##############   #####     
   ##---------########### T ######    
   #------------#########   ######    
  ##--------------#################   
  ##----------------###############   
  ##------------------#############   
  ##--------------------###########   
  ###--------   ----------#########   
   ##-------- P -----------#######    
   ###-------   ------------######    
    ####----------------------###     
      ###----------------------       
        ####-----------------         
          #####------------           
               #######                

        

Moment tensor inversion summary for event 2010/10/14 12:59

Date: 2010/10/14
Time: 12:59 (UTC)
Region: Yakutat Bay Region of Alaska
Mw=4.3

Location:

Lat.  60.3802;  Lon.  -140.6207; Depth    5 km 
(Best-fitting depth from moment tensor inversion)

Solution quality: poor
Number of stations = 8

Best Double Couple:

         strike    dip    rake 
Plane 1:  338.6   58.7   -37.9
Plane 2:   90.6   58.3  -142.4

Moment Tensor Parameters:

Mo = 3.34318e+22 dyn-cm
Mxx =  1.74; Mxy =  2.21; Mxz = -0.95
Myy =  0.05; Myz =  1.41; Mzz = -1.79

Principal Axes:
     value   azimuth   plunge
T:    3.26    34.66    0.26
N:    0.08   124.90   42.38
P:   -3.34   304.37   47.62

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 0.06 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   320    45   -80   3.99 0.2290
WVFGRD96    1.0   100    70    20   3.85 0.2107
WVFGRD96    2.0   105    65    30   4.00 0.2732
WVFGRD96    3.0   100    70    20   4.00 0.3110
WVFGRD96    4.0   345    45   -35   4.10 0.3583
WVFGRD96    5.0   345    50   -35   4.10 0.4115
WVFGRD96    6.0   345    50   -35   4.11 0.4510
WVFGRD96    7.0   340    50   -30   4.09 0.4787
WVFGRD96    8.0   345    50   -35   4.17 0.5015
WVFGRD96    9.0   345    50   -35   4.17 0.5210
WVFGRD96   10.0   340    50   -30   4.16 0.5319
WVFGRD96   11.0   345    55   -35   4.17 0.5382
WVFGRD96   12.0   345    55   -20   4.15 0.5405
WVFGRD96   13.0   345    55   -20   4.15 0.5410
WVFGRD96   14.0   345    60   -20   4.16 0.5395
WVFGRD96   15.0   350    65   -30   4.17 0.5367
WVFGRD96   16.0   355    75   -30   4.18 0.5333
WVFGRD96   17.0   355    75   -30   4.18 0.5288
WVFGRD96   18.0   355    75   -30   4.19 0.5233
WVFGRD96   19.0   355    75   -30   4.19 0.5182
WVFGRD96   20.0    -5    75   -30   4.19 0.5121
WVFGRD96   21.0    -5    80   -35   4.21 0.5057
WVFGRD96   22.0    -5    75   -30   4.21 0.4988
WVFGRD96   23.0    -5    80   -35   4.22 0.4922
WVFGRD96   24.0    -5    80   -35   4.23 0.4841
WVFGRD96   25.0    -5    75   -30   4.23 0.4768
WVFGRD96   26.0    -5    80   -30   4.24 0.4691
WVFGRD96   27.0    -5    80   -30   4.25 0.4613
WVFGRD96   28.0    -5    80   -30   4.25 0.4532
WVFGRD96   29.0    -5    80   -30   4.26 0.4451

The best solution is

WVFGRD96   13.0   345    55   -20   4.15 0.5410

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 0.06 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=Fri Oct 15 10:38:30 CDT 2010

Last Changed 2010/10/14