Location

Location ANSS

2018/06/13 13:39:37 19.414 -155.281 0.3 5.3 Hawaii

Focal Mechanism

 USGS/SLU Moment Tensor Solution
 ENS  2018/06/13 13:39:37:0  19.41 -155.28   0.3 5.3 Hawaii
 
 Stations used:
   HV.DESD HV.ERZ1 HV.ERZ2 HV.ERZ3 HV.ERZ4 HV.HLPD HV.HOVE 
   HV.HSSD HV.HUAD HV.JOKA HV.MLOD HV.MOKD HV.NAGD HV.NPOC 
   HV.SPDD HV.STCD HV.TOUO HV.WILD IU.POHA PT.HPAH PT.MLOA 
 
 Filtering commands used:
   cut o DIST/3.3 -30 o DIST/3.3 +70
   rtr
   taper w 0.1
   hp c 0.02 n 3 
   lp c 0.05 n 3 
 
 Best Fitting Double Couple
  Mo = 6.24e+23 dyne-cm
  Mw = 5.13 
  Z  = 3 km
  Plane   Strike  Dip  Rake
   NP1      242    50   -86
   NP2       55    40   -95
  Principal Axes:
   Axis    Value   Plunge  Azimuth
    T   6.24e+23      5     329
    N   0.00e+00      3      59
    P  -6.24e+23     84     181

 Moment Tensor: (dyne-cm)
    Component   Value
       Mxx     4.43e+23
       Mxy    -2.76e+23
       Mxz     1.12e+23
       Myy     1.68e+23
       Myz    -2.78e+22
       Mzz    -6.12e+23
                                                     
                                                     
                                                     
                                                     
                     ##############                  
                  T ###################              
              ###   ######################           
             ##############################          
           ######################-------#####        
          ################-------------------#       
         #############-----------------------##      
        ############-------------------------###     
        #########----------------------------###     
       ########------------------------------####    
       #######------------------------------#####    
       ######-------------   --------------######    
       #####-------------- P -------------#######    
        ###---------------   ------------#######     
        ##-----------------------------#########     
         #---------------------------##########      
          -------------------------###########       
           ---------------------#############        
             ##------------################          
              ############################           
                 ######################              
                     ##############                  
                                                     
                                                     
                                                     
 Global CMT Convention Moment Tensor:
      R          T          P
 -6.12e+23   1.12e+23   2.78e+22 
  1.12e+23   4.43e+23   2.76e+23 
  2.78e+22   2.76e+23   1.68e+23 


Details of the solution is found at

http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20180613133937/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 = 55
      DIP = 40
     RAKE = -95
       MW = 5.13
       HS = 3.0

The NDK file is 20180613133937.ndk The waveform inversion is preferred.

Moment Tensor Comparison

The following compares this source inversion to others
SLU
 USGS/SLU Moment Tensor Solution
 ENS  2018/06/13 13:39:37:0  19.41 -155.28   0.3 5.3 Hawaii
 
 Stations used:
   HV.DESD HV.ERZ1 HV.ERZ2 HV.ERZ3 HV.ERZ4 HV.HLPD HV.HOVE 
   HV.HSSD HV.HUAD HV.JOKA HV.MLOD HV.MOKD HV.NAGD HV.NPOC 
   HV.SPDD HV.STCD HV.TOUO HV.WILD IU.POHA PT.HPAH PT.MLOA 
 
 Filtering commands used:
   cut o DIST/3.3 -30 o DIST/3.3 +70
   rtr
   taper w 0.1
   hp c 0.02 n 3 
   lp c 0.05 n 3 
 
 Best Fitting Double Couple
  Mo = 6.24e+23 dyne-cm
  Mw = 5.13 
  Z  = 3 km
  Plane   Strike  Dip  Rake
   NP1      242    50   -86
   NP2       55    40   -95
  Principal Axes:
   Axis    Value   Plunge  Azimuth
    T   6.24e+23      5     329
    N   0.00e+00      3      59
    P  -6.24e+23     84     181

 Moment Tensor: (dyne-cm)
    Component   Value
       Mxx     4.43e+23
       Mxy    -2.76e+23
       Mxz     1.12e+23
       Myy     1.68e+23
       Myz    -2.78e+22
       Mzz    -6.12e+23
                                                     
                                                     
                                                     
                                                     
                     ##############                  
                  T ###################              
              ###   ######################           
             ##############################          
           ######################-------#####        
          ################-------------------#       
         #############-----------------------##      
        ############-------------------------###     
        #########----------------------------###     
       ########------------------------------####    
       #######------------------------------#####    
       ######-------------   --------------######    
       #####-------------- P -------------#######    
        ###---------------   ------------#######     
        ##-----------------------------#########     
         #---------------------------##########      
          -------------------------###########       
           ---------------------#############        
             ##------------################          
              ############################           
                 ######################              
                     ##############                  
                                                     
                                                     
                                                     
 Global CMT Convention Moment Tensor:
      R          T          P
 -6.12e+23   1.12e+23   2.78e+22 
  1.12e+23   4.43e+23   2.76e+23 
  2.78e+22   2.76e+23   1.68e+23 


Details of the solution is found at

http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20180613133937/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 using wvfgrd96

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 o DIST/3.3 -30 o DIST/3.3 +70
rtr
taper w 0.1
hp c 0.02 n 3 
lp c 0.05 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    1.0   250    50   -80   5.00 0.4700
WVFGRD96    2.0   245    50   -85   5.09 0.5627
WVFGRD96    3.0    55    40   -95   5.13 0.5636
WVFGRD96    4.0   245    55   -75   5.16 0.5435
WVFGRD96    5.0   260    55   -60   5.16 0.5332
WVFGRD96    6.0   265    55   -55   5.16 0.5217
WVFGRD96    7.0   265    55   -55   5.18 0.4981
WVFGRD96    8.0   265    55   -55   5.22 0.4909
WVFGRD96    9.0   265    60   -50   5.22 0.4515
WVFGRD96   10.0   270    65   -40   5.19 0.4129
WVFGRD96   11.0   260    65    20   5.12 0.4028
WVFGRD96   12.0   260    70    20   5.13 0.3969
WVFGRD96   13.0   260    70    25   5.14 0.3894
WVFGRD96   14.0   260    75    25   5.15 0.3805
WVFGRD96   15.0   290    40    70   5.18 0.3707
WVFGRD96   16.0   290    40    70   5.18 0.3704
WVFGRD96   17.0   285    45    70   5.20 0.3702
WVFGRD96   18.0   285    45    70   5.20 0.3699
WVFGRD96   19.0   285    45    70   5.20 0.3682
WVFGRD96   20.0   285    45    70   5.20 0.3660
WVFGRD96   21.0   285    45    70   5.21 0.3611
WVFGRD96   22.0   285    45    70   5.21 0.3583
WVFGRD96   23.0   285    45    70   5.21 0.3552
WVFGRD96   24.0   290    45    70   5.22 0.3520
WVFGRD96   25.0   280    50    65   5.22 0.3488
WVFGRD96   26.0   280    50    65   5.23 0.3454
WVFGRD96   27.0   280    50    65   5.23 0.3417
WVFGRD96   28.0   285    45    65   5.23 0.3378
WVFGRD96   29.0   285    45    65   5.23 0.3340

The best solution is

WVFGRD96    3.0    55    40   -95   5.13 0.5636

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 o DIST/3.3 -30 o DIST/3.3 +70
rtr
taper w 0.1
hp c 0.02 n 3 
lp c 0.05 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.


Grid Search Full Moment Tensor Inversion using wvfmtgrd96

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 wvfmtgrd96 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 o DIST/3.3 -20 o DIST/3.3 +50
rtr
taper w 0.1
hp c 0.02 n 3 
lp c 0.05 n 3 
The results of this grid search over depth are as follow:

MT Program  H(km) Mxx(dyne-cm)   Myy        Mxy        Mxz        Myz        Mzz       Mw      Fit
WVFMTGRD96    1.0  0.420E+24  0.235E+24 -0.122E+24  0.669E+23  0.411E+23 -0.135E+24  4.9881  0.5301
WVFMTGRD96    2.0  0.477E+24  0.252E+24 -0.168E+24  0.161E+24  0.734E+23 -0.398E+24  5.0847  0.6010
WVFMTGRD96    3.0  0.588E+24  0.422E+24 -0.214E+24  0.209E+24  0.763E+23 -0.607E+23  5.1184  0.6308
WVFMTGRD96    4.0  0.685E+24  0.523E+24 -0.244E+24  0.211E+24  0.472E+23  0.116E+24  5.1617  0.6423
WVFMTGRD96    5.0  0.754E+24  0.587E+24 -0.277E+24  0.186E+24  0.696E+23  0.212E+24  5.1914  0.6439
WVFMTGRD96    6.0  0.818E+24  0.630E+24 -0.304E+24  0.182E+24  0.854E+23  0.352E+24  5.2206  0.6415
WVFMTGRD96    7.0  0.878E+24  0.729E+24 -0.331E+24  0.179E+24  0.956E+23  0.356E+24  5.2458  0.6368
WVFMTGRD96    8.0  0.105E+25  0.842E+24 -0.363E+24  0.238E+24  0.130E+24  0.492E+24  5.2974  0.6318
WVFMTGRD96    9.0  0.109E+25  0.920E+24 -0.408E+24  0.228E+24  0.144E+24  0.613E+24  5.3203  0.6187
WVFMTGRD96   10.0  0.125E+25  0.100E+25 -0.401E+24  0.172E+24  0.124E+24  0.815E+24  5.3538  0.6031
WVFMTGRD96   11.0  0.129E+25  0.112E+25 -0.455E+24  0.215E+24  0.956E+23  0.914E+24  5.3762  0.5882
WVFMTGRD96   12.0  0.136E+25  0.113E+25 -0.464E+24  0.191E+24  0.104E+24  0.105E+25  5.3912  0.5721
WVFMTGRD96   13.0  0.131E+25  0.117E+25 -0.500E+24  0.181E+24  0.580E+23  0.121E+25  5.4030  0.5561
WVFMTGRD96   14.0  0.140E+25  0.126E+25 -0.501E+24  0.182E+24  0.582E+23  0.130E+25  5.4210  0.5413
WVFMTGRD96   15.0  0.146E+25  0.131E+25 -0.524E+24  0.190E+24  0.608E+23  0.136E+25  5.4338  0.5263
WVFMTGRD96   16.0  0.151E+25  0.136E+25 -0.520E+24  0.141E+24  0.680E+23  0.145E+25  5.4441  0.5114
WVFMTGRD96   17.0  0.151E+25  0.132E+25 -0.561E+24  0.150E+24  0.388E+23  0.150E+25  5.4468  0.4974
WVFMTGRD96   18.0  0.159E+25  0.140E+25 -0.553E+24  0.147E+24  0.383E+23  0.159E+25  5.4616  0.4841
WVFMTGRD96   19.0  0.164E+25  0.145E+25 -0.570E+24  0.152E+24  0.394E+23  0.164E+25  5.4704  0.4713
WVFMTGRD96   20.0  0.169E+25  0.149E+25 -0.586E+24  0.156E+24  0.406E+23  0.169E+25  5.4787  0.4593
WVFMTGRD96   21.0  0.222E+25  0.187E+25 -0.523E+24  0.190E+24  0.667E+23  0.198E+25  5.5374  0.4489
WVFMTGRD96   22.0  0.212E+25  0.190E+25 -0.549E+24  0.146E+24  0.720E+23  0.200E+25  5.5347  0.4376
WVFMTGRD96   23.0  0.233E+25  0.197E+25 -0.550E+24  0.200E+24  0.773E+23  0.209E+25  5.5521  0.4274
WVFMTGRD96   24.0  0.239E+25  0.202E+25 -0.565E+24  0.206E+24  0.793E+23  0.215E+25  5.5597  0.4176
WVFMTGRD96   25.0  0.227E+25  0.183E+25 -0.607E+24  0.166E+24  0.529E+23  0.213E+25  5.5469  0.4087
WVFMTGRD96   26.0  0.232E+25  0.187E+25 -0.620E+24  0.170E+24  0.540E+23  0.218E+25  5.5530  0.4004
WVFMTGRD96   27.0  0.230E+25  0.186E+25 -0.618E+24  0.167E+24  0.655E+23  0.221E+25  5.5528  0.3927
WVFMTGRD96   28.0  0.234E+25  0.189E+25 -0.628E+24  0.170E+24  0.666E+23  0.225E+25  5.5578  0.3859
WVFMTGRD96   29.0  0.151E+25  0.125E+25 -0.737E+24  0.614E+23  0.491E+23  0.187E+25  5.4752  0.3800

The best solution is

WVFMTGRD96    5.0  0.754E+24  0.587E+24 -0.277E+24  0.186E+24  0.696E+23  0.212E+24  5.1914  0.6439

The complete moment tensor decomposition using the program mtinfo is given in the text file MTGRDinfo.txt. (Jost, M. L., and R. B. Herrmann (1989). A student's guide to and review of moment tensors, Seism. Res. Letters 60, 37-57. SRL_60_2_37-57.pdf.

The P-wave first motion mechanism corresponding 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 o DIST/3.3 -20 o DIST/3.3 +50
rtr
taper w 0.1
hp c 0.02 n 3 
lp c 0.05 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.

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 Wed Jun 13 17:04:14 CDT 2018