Location

2014/01/02 12:04:50 39.057 -118.108 6.4 3.9 Nevada

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  2014/01/02 12:04:50:0  39.06 -118.11   6.4 3.9 Nevada
 
 Stations used:
   BK.CMB CI.CWC CI.GRA CI.MLAC CI.MPM CI.SHO CI.SLA CI.TIN 
   CI.TUQ IM.NV31 LB.DAC NN.BEK NN.OMMB NN.PNT NN.RUB NN.RYN 
   NN.SHP NN.VCN NN.WAK NN.YER TA.O03E TA.R11A US.DUG US.ELK 
   US.TPNV US.WVOR UU.PSUT 
 
 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 = 1.88e+21 dyne-cm
  Mw = 3.45 
  Z  = 10 km
  Plane   Strike  Dip  Rake
   NP1       80    80    45
   NP2      340    46   166
  Principal Axes:
   Axis    Value   Plunge  Azimuth
    T   1.88e+21     38     311
    N   0.00e+00     44      90
    P  -1.88e+21     22     203

 Moment Tensor: (dyne-cm)
    Component   Value
       Mxx    -8.90e+20
       Mxy    -1.15e+21
       Mxz     1.19e+21
       Myy     4.35e+20
       Myz    -4.45e+20
       Mzz     4.56e+20
                                                     
                                                     
                                                     
                                                     
                     #-------------                  
                 ##########------------              
              ################------------           
             ###################-----------          
           #######################-----------        
          #######   ###############-----------       
         ######## T ################-----------      
        #########   #################-----------     
        ##############################----------     
       ################################--------##    
       ################################---#######    
       #############################----#########    
       ####################-------------#########    
        --------------------------------########     
        --------------------------------########     
         -------------------------------#######      
          ------------------------------######       
           ----------------------------######        
             -------   ----------------####          
              ------ P ---------------####           
                 ---   --------------##              
                     --------------                  
                                                     
                                                     
                                                     
 Global CMT Convention Moment Tensor:
      R          T          P
  4.56e+20   1.19e+21   4.45e+20 
  1.19e+21  -8.90e+20   1.15e+21 
  4.45e+20   1.15e+21   4.35e+20 


Details of the solution is found at

http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20140102120450/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 = 80
      DIP = 80
     RAKE = 45
       MW = 3.45
       HS = 10.0

The NDK file is 20140102120450.ndk The waveform inversion is preferred.

Moment Tensor Comparison

The following compares this source inversion to others
SLU
UNR
 USGS/SLU Moment Tensor Solution
 ENS  2014/01/02 12:04:50:0  39.06 -118.11   6.4 3.9 Nevada
 
 Stations used:
   BK.CMB CI.CWC CI.GRA CI.MLAC CI.MPM CI.SHO CI.SLA CI.TIN 
   CI.TUQ IM.NV31 LB.DAC NN.BEK NN.OMMB NN.PNT NN.RUB NN.RYN 
   NN.SHP NN.VCN NN.WAK NN.YER TA.O03E TA.R11A US.DUG US.ELK 
   US.TPNV US.WVOR UU.PSUT 
 
 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 = 1.88e+21 dyne-cm
  Mw = 3.45 
  Z  = 10 km
  Plane   Strike  Dip  Rake
   NP1       80    80    45
   NP2      340    46   166
  Principal Axes:
   Axis    Value   Plunge  Azimuth
    T   1.88e+21     38     311
    N   0.00e+00     44      90
    P  -1.88e+21     22     203

 Moment Tensor: (dyne-cm)
    Component   Value
       Mxx    -8.90e+20
       Mxy    -1.15e+21
       Mxz     1.19e+21
       Myy     4.35e+20
       Myz    -4.45e+20
       Mzz     4.56e+20
                                                     
                                                     
                                                     
                                                     
                     #-------------                  
                 ##########------------              
              ################------------           
             ###################-----------          
           #######################-----------        
          #######   ###############-----------       
         ######## T ################-----------      
        #########   #################-----------     
        ##############################----------     
       ################################--------##    
       ################################---#######    
       #############################----#########    
       ####################-------------#########    
        --------------------------------########     
        --------------------------------########     
         -------------------------------#######      
          ------------------------------######       
           ----------------------------######        
             -------   ----------------####          
              ------ P ---------------####           
                 ---   --------------##              
                     --------------                  
                                                     
                                                     
                                                     
 Global CMT Convention Moment Tensor:
      R          T          P
  4.56e+20   1.19e+21   4.45e+20 
  1.19e+21  -8.90e+20   1.15e+21 
  4.45e+20   1.15e+21   4.35e+20 


Details of the solution is found at

http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20140102120450/index.html
	
REVIEWED BY NSL STAFF

Event ID:432876
Origin ID:1074894
Algorithm: Ichinose (2003) Long Period, Regional-Distance Waves
Seismic Moment Tensor Solution

2014/01/02 (002) 12:04:52.00 39.0570 -118.1082 1074894
	Depth =   8.0 (km)
	Mw    =  3.44
	Mo    =  1.78x10^21 (dyne x cm)

	Percent Double Couple =  99 %
	Percent CLVD          =   1 %
	no ISO calculated
	Epsilon=-0.00
	 Percent Variance Reduction =  58.44 %
	 Total Fit                  =  31.02 
	Major Double Couple
		            strike dip   rake
		Nodal Plane 1: 346  43 -173
		Nodal Plane 2: 251  85  -47

	DEVIATORIC MOMENT TENSOR

	Moment Tensor Elements: Spherical Coordinates
		Mrr= -0.23 Mtt= -0.55 Mff=  0.77
		Mrt=  1.25 Mrf=  0.33 Mtf=  1.02 EXP=21


	Moment Tensor Elements: Cartesian Coordinates
		-0.55 -1.02  1.25
		-1.02  0.77 -0.33
		 1.25 -0.33 -0.23

	Eigenvalues:
		T-axis eigenvalue=  1.79
		N-axis eigenvalue= -0.01
		P-axis eigenvalue= -1.78

	Eigenvalues and eigenvectors of the Major Double Couple:
		T-axis ev= 1.79 trend=308 plunge=27
		N-axis ev= 0.00 trend=66 plunge=43
		P-axis ev=-1.79 trend=197 plunge=35

	Maximum Azmuithal Gap=240 Distance to Nearest Station= 59.3 (km)

	Number of Stations (D=Displacement/V=Velocity) Used=9 (defining only)
		
	 RYN.NN.D NV31.IM.D YER.NN.D PNT.NN.D
	 WAK.NN.D PAH.NN.D VCN.NN.D RUB.NN.D
	 OMMB.NN.D


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


All Stations defining and nondefining: 
Station.Net 	Def 	Distance 	Azi    	Bazi  	lo-f 	hi-f vmodel
            	    	(km)     	(deg)  	(deg) 	(Hz) 	(Hz)    
RYN.NN (D) 	Y 	    59.3  	217  	 37  	0.020 	0.080 RYN.NN.wus.glib
NV31.IM (D) 	Y 	    69.8  	184  	  4  	0.020 	0.080 NV31.IM.wus.glib
YER.NN (D) 	Y 	    98.0  	266  	 85  	0.020 	0.080 YER.NN.wus.glib
PNT.NN (D) 	Y 	   128.7  	272  	 91  	0.020 	0.080 PNT.NN.wus.glib
WAK.NN (D) 	Y 	   130.9  	242  	 61  	0.020 	0.080 WAK.NN.wus.glib
PAH.NN (D) 	Y 	   131.8  	304  	123  	0.020 	0.080 PAH.NN.wus.glib
VCN.NN (D) 	Y 	   135.5  	282  	101  	0.020 	0.080 VCN.NN.wus.glib
RUB.NN (D) 	Y 	   176.2  	270  	 89  	0.020 	0.080 RUB.NN.wus.glib
OMMB.NN (D) 	Y 	   178.6  	206  	 26  	0.020 	0.080 OMMB.NN.wus.glib

 (V)-velocity (D)-Displacement

Author: www-data
Date: 2014/01/02 13:23:51

mtinv Version 2.1_DEVEL OCT2008

        

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   250    70    15   3.09 0.2530
WVFGRD96    1.0    65    90     5   3.12 0.2705
WVFGRD96    2.0    70    80    10   3.20 0.3360
WVFGRD96    3.0    70    85    20   3.25 0.3511
WVFGRD96    4.0   250    85   -45   3.33 0.3729
WVFGRD96    5.0   250    85   -45   3.35 0.3953
WVFGRD96    6.0   250    85   -40   3.36 0.4139
WVFGRD96    7.0    75    90    40   3.37 0.4270
WVFGRD96    8.0    75    85    45   3.43 0.4377
WVFGRD96    9.0    75    85    45   3.44 0.4444
WVFGRD96   10.0    80    80    45   3.45 0.4480
WVFGRD96   11.0    75    85    40   3.45 0.4472
WVFGRD96   12.0    80    80    40   3.45 0.4460
WVFGRD96   13.0    80    80    40   3.46 0.4407
WVFGRD96   14.0    75    85    35   3.47 0.4364
WVFGRD96   15.0    75    85    35   3.48 0.4310
WVFGRD96   16.0    75    85    35   3.48 0.4243
WVFGRD96   17.0   255    90   -35   3.48 0.4167
WVFGRD96   18.0   255    90   -35   3.49 0.4099
WVFGRD96   19.0   255    90   -35   3.49 0.4028
WVFGRD96   20.0   255    90   -30   3.50 0.3956
WVFGRD96   21.0   255    90   -35   3.51 0.3879
WVFGRD96   22.0   255    90   -35   3.51 0.3800
WVFGRD96   23.0   255    90   -30   3.52 0.3721
WVFGRD96   24.0   255    90   -30   3.52 0.3645
WVFGRD96   25.0   255    90   -30   3.52 0.3569
WVFGRD96   26.0   250    85   -30   3.54 0.3493
WVFGRD96   27.0   250    85   -30   3.55 0.3417
WVFGRD96   28.0   250    80   -30   3.55 0.3337
WVFGRD96   29.0   250    80   -30   3.55 0.3262

The best solution is

WVFGRD96   10.0    80    80    45   3.45 0.4480

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 00:09:28 CST 2015