Location

Location ANSS

2016/12/28 08:22:12 38.392 -118.899 12.0 5.7 Nevada

Focal Mechanism

 USGS/SLU Moment Tensor Solution
 ENS  2016/12/28 08:22:12:0  38.39 -118.90  12.0 5.7 Nevada
 
 Stations used:
   BK.SAO CI.GSC CI.ISA LB.BMN LB.TPH NC.AFD NC.BBGB NC.KCPB 
   NC.MDPB NC.PMPB NN.BEK NN.CMK6 NN.COLR NN.DSP NN.EMB NN.GWY 
   NN.KVN NN.LCH NN.MPK NN.MZPB NN.OMMB NN.PIO NN.PLTX NN.PNT 
   NN.PRN NN.Q09A NN.REDF NN.S11A NN.VCN NN.WLDB NN.WTNK 
   NN.YER SN.HEL TA.R11A US.ELK US.TPNV 
 
 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 = 2.16e+24 dyne-cm
  Mw = 5.49 
  Z  = 13 km
  Plane   Strike  Dip  Rake
   NP1      210    75   -20
   NP2      305    71   -164
  Principal Axes:
   Axis    Value   Plunge  Azimuth
    T   2.16e+24      3     258
    N   0.00e+00     65     355
    P  -2.16e+24     25     167

 Moment Tensor: (dyne-cm)
    Component   Value
       Mxx    -1.61e+24
       Mxy     8.21e+23
       Mxz     7.76e+23
       Myy     1.98e+24
       Myz    -2.92e+23
       Mzz    -3.70e+23
                                                     
                                                     
                                                     
                                                     
                     --------------                  
                 ---------------------#              
              ---------------------#######           
             --------------------##########          
           ---------------------#############        
          ##########----------################       
         ###############-----##################      
        ###################-####################     
        ##################----##################     
       ##################--------################    
       #################-----------##############    
       ################--------------############    
          ############-----------------##########    
        T ###########-------------------########     
          ###########---------------------######     
         ###########-----------------------####      
          #########-------------------------##       
           ########--------------------------        
             #####------------   ----------          
              ####------------ P ---------           
                 #------------   ------              
                     --------------                  
                                                     
                                                     
                                                     
 Global CMT Convention Moment Tensor:
      R          T          P
 -3.70e+23   7.76e+23   2.92e+23 
  7.76e+23  -1.61e+24  -8.21e+23 
  2.92e+23  -8.21e+23   1.98e+24 


Details of the solution is found at

http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20161228082212/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 = 75
     RAKE = -20
       MW = 5.49
       HS = 13.0

The NDK file is 20161228082212.ndk The waveform inversion is preferred.

Moment Tensor Comparison

The following compares this source inversion to others
SLU
USGSMT
GCMT
 USGS/SLU Moment Tensor Solution
 ENS  2016/12/28 08:22:12:0  38.39 -118.90  12.0 5.7 Nevada
 
 Stations used:
   BK.SAO CI.GSC CI.ISA LB.BMN LB.TPH NC.AFD NC.BBGB NC.KCPB 
   NC.MDPB NC.PMPB NN.BEK NN.CMK6 NN.COLR NN.DSP NN.EMB NN.GWY 
   NN.KVN NN.LCH NN.MPK NN.MZPB NN.OMMB NN.PIO NN.PLTX NN.PNT 
   NN.PRN NN.Q09A NN.REDF NN.S11A NN.VCN NN.WLDB NN.WTNK 
   NN.YER SN.HEL TA.R11A US.ELK US.TPNV 
 
 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 = 2.16e+24 dyne-cm
  Mw = 5.49 
  Z  = 13 km
  Plane   Strike  Dip  Rake
   NP1      210    75   -20
   NP2      305    71   -164
  Principal Axes:
   Axis    Value   Plunge  Azimuth
    T   2.16e+24      3     258
    N   0.00e+00     65     355
    P  -2.16e+24     25     167

 Moment Tensor: (dyne-cm)
    Component   Value
       Mxx    -1.61e+24
       Mxy     8.21e+23
       Mxz     7.76e+23
       Myy     1.98e+24
       Myz    -2.92e+23
       Mzz    -3.70e+23
                                                     
                                                     
                                                     
                                                     
                     --------------                  
                 ---------------------#              
              ---------------------#######           
             --------------------##########          
           ---------------------#############        
          ##########----------################       
         ###############-----##################      
        ###################-####################     
        ##################----##################     
       ##################--------################    
       #################-----------##############    
       ################--------------############    
          ############-----------------##########    
        T ###########-------------------########     
          ###########---------------------######     
         ###########-----------------------####      
          #########-------------------------##       
           ########--------------------------        
             #####------------   ----------          
              ####------------ P ---------           
                 #------------   ------              
                     --------------                  
                                                     
                                                     
                                                     
 Global CMT Convention Moment Tensor:
      R          T          P
 -3.70e+23   7.76e+23   2.92e+23 
  7.76e+23  -1.61e+24  -8.21e+23 
  2.92e+23  -8.21e+23   1.98e+24 


Details of the solution is found at

http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20161228082212/index.html
	
Body-wave Moment Tensor (Mwb)
Moment	2.545e+17 N-m
Magnitude	5.5 Mwb
Depth	12.0 km
Percent DC	90 %
Half Duration	–
Catalog	US
Data Source	US3
Contributor	US3
Nodal Planes
Plane	Strike	Dip	Rake
NP1	210	81	3
NP2	120	87	171
Principal Axes
Axis	Value	Plunge	Azimuth
T	2.608e+17 N-m	9	75
N	-0.130e+17 N-m	80	280
P	-2.478e+17 N-m	4	165

        
December 28, 2016, CALIFORNIA-NEVADA BORDER REGION, MW=5.6

Goran Ekstrom

CENTROID-MOMENT-TENSOR  SOLUTION
GCMT EVENT:     C201612280822A
DATA: II IU CU G  IC MN LD GE DK
L.P.BODY WAVES: 55S,  72C, T= 40
MANTLE WAVES:   16S,  16C, T=125
SURFACE WAVES: 139S, 267C, T= 50
TIMESTAMP:      Q-20161228110948
CENTROID LOCATION:
ORIGIN TIME:      08:22:14.9 0.2
LAT:38.41N 0.01;LON:118.96W 0.01
DEP: 22.2  0.8;TRIANG HDUR:  1.5
MOMENT TENSOR: SCALE 10**24 D-CM
RR=-1.440 0.087; TT=-1.970 0.062
PP= 3.410 0.074; RT= 0.278 0.122
RP= 0.869 0.111; TP=-0.731 0.049
PRINCIPAL AXES:
1.(T) VAL=  3.642;PLG= 9;AZM=263
2.(N)      -1.363;    60;      9
3.(P)      -2.279;    28;    168
BEST DBLE.COUPLE:M0= 2.96*10**24
NP1: STRIKE=309;DIP=63;SLIP=-166
NP2: STRIKE=213;DIP=77;SLIP= -27

            -----------
        ------------------#
      ------------------#####
    #####-------------#########
   ############-----############
  ################-##############
  ###############---#############
 ###############-------###########
    ###########---------##########
  T ##########------------########
    #########--------------#######
  ##########----------------#####
  #########------------------####
   #######--------------------##
    ######--------   ---------#
      ###--------- P --------
        #---------   ------
            -----------
        

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    35    85    -5   5.16 0.3959
WVFGRD96    2.0    35    80   -10   5.26 0.4977
WVFGRD96    3.0   215    85   -10   5.29 0.5336
WVFGRD96    4.0   210    80   -30   5.35 0.5644
WVFGRD96    5.0   210    75   -30   5.38 0.5955
WVFGRD96    6.0   210    75   -25   5.39 0.6232
WVFGRD96    7.0   210    75   -25   5.41 0.6472
WVFGRD96    8.0   210    75   -30   5.45 0.6732
WVFGRD96    9.0   210    75   -25   5.45 0.6879
WVFGRD96   10.0   210    75   -25   5.47 0.6988
WVFGRD96   11.0   210    75   -25   5.48 0.7052
WVFGRD96   12.0   210    75   -20   5.48 0.7081
WVFGRD96   13.0   210    75   -20   5.49 0.7094
WVFGRD96   14.0   215    80   -20   5.49 0.7081
WVFGRD96   15.0   215    80   -20   5.50 0.7053
WVFGRD96   16.0   215    80   -20   5.51 0.7008
WVFGRD96   17.0   215    80   -20   5.51 0.6946
WVFGRD96   18.0   215    80   -15   5.52 0.6881
WVFGRD96   19.0   215    80   -15   5.53 0.6808
WVFGRD96   20.0   215    80   -15   5.53 0.6727
WVFGRD96   21.0   215    80   -15   5.54 0.6637
WVFGRD96   22.0   215    80   -15   5.54 0.6541
WVFGRD96   23.0   215    80   -15   5.55 0.6440
WVFGRD96   24.0   215    80   -15   5.55 0.6335
WVFGRD96   25.0   215    75   -15   5.56 0.6229
WVFGRD96   26.0   215    75   -15   5.57 0.6125
WVFGRD96   27.0   215    75   -10   5.57 0.6024
WVFGRD96   28.0   215    75   -10   5.58 0.5922
WVFGRD96   29.0   215    75   -10   5.58 0.5819

The best solution is

WVFGRD96   13.0   210    75   -20   5.49 0.7094

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.

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 Dec 28 15:53:09 CST 2016