Location

2013/02/13 09:53:35 38.032 -118.055 5.3 4.0 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  2013/02/13 09:53:35:0  38.03 -118.06   5.3 4.0 Nevada
 
 Stations used:
   BK.ORV BK.WDC CI.GSC CI.ISA CI.LDF CI.OSI II.PFO LB.DAC 
   NC.MDPB NN.KVN NN.OMMB NN.PAH NN.PNT NN.RUB NN.RYN NN.VCN 
   NN.WAK NN.YER TA.109C TA.R11A US.DUG US.ELK UU.BGU UU.MPU 
   UU.NLU UU.PSUT UU.SZCU UU.TCRU UW.IRON 
 
 Filtering commands used:
   hp c 0.02 n 3
   lp c 0.06 n 3
 
 Best Fitting Double Couple
  Mo = 8.04e+21 dyne-cm
  Mw = 3.87 
  Z  = 12 km
  Plane   Strike  Dip  Rake
   NP1      337    71   -159
   NP2      240    70   -20
  Principal Axes:
   Axis    Value   Plunge  Azimuth
    T   8.04e+21      1     108
    N   0.00e+00     62      17
    P  -8.04e+21     28     199

 Moment Tensor: (dyne-cm)
    Component   Value
       Mxx    -4.82e+21
       Mxy    -4.31e+21
       Mxz     3.11e+21
       Myy     6.59e+21
       Myz     1.18e+21
       Mzz    -1.77e+21
                                                     
                                                     
                                                     
                                                     
                     --------------                  
                 #####-----------------              
              ##########------------------           
             ############------------------          
           ################------------------        
          ##################-------------#####       
         ####################-----#############      
        #####################-##################     
        ##################-----#################     
       ################---------#################    
       #############-------------################    
       ###########----------------###############    
       #########------------------###############    
        ######---------------------###########       
        ####-----------------------########### T     
         ##-------------------------##########       
          --------------------------##########       
           -----------   -----------#########        
             --------- P -----------#######          
              --------   -----------######           
                 -------------------###              
                     --------------                  
                                                     
                                                     
                                                     
 Global CMT Convention Moment Tensor:
      R          T          P
 -1.77e+21   3.11e+21  -1.18e+21 
  3.11e+21  -4.82e+21   4.31e+21 
 -1.18e+21   4.31e+21   6.59e+21 


Details of the solution is found at

http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20130213095335/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 = 240
      DIP = 70
     RAKE = -20
       MW = 3.87
       HS = 12.0

The NDK file is 20130213095335.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  2013/02/13 09:53:35:0  38.03 -118.06   5.3 4.0 Nevada
 
 Stations used:
   BK.ORV BK.WDC CI.GSC CI.ISA CI.LDF CI.OSI II.PFO LB.DAC 
   NC.MDPB NN.KVN NN.OMMB NN.PAH NN.PNT NN.RUB NN.RYN NN.VCN 
   NN.WAK NN.YER TA.109C TA.R11A US.DUG US.ELK UU.BGU UU.MPU 
   UU.NLU UU.PSUT UU.SZCU UU.TCRU UW.IRON 
 
 Filtering commands used:
   hp c 0.02 n 3
   lp c 0.06 n 3
 
 Best Fitting Double Couple
  Mo = 8.04e+21 dyne-cm
  Mw = 3.87 
  Z  = 12 km
  Plane   Strike  Dip  Rake
   NP1      337    71   -159
   NP2      240    70   -20
  Principal Axes:
   Axis    Value   Plunge  Azimuth
    T   8.04e+21      1     108
    N   0.00e+00     62      17
    P  -8.04e+21     28     199

 Moment Tensor: (dyne-cm)
    Component   Value
       Mxx    -4.82e+21
       Mxy    -4.31e+21
       Mxz     3.11e+21
       Myy     6.59e+21
       Myz     1.18e+21
       Mzz    -1.77e+21
                                                     
                                                     
                                                     
                                                     
                     --------------                  
                 #####-----------------              
              ##########------------------           
             ############------------------          
           ################------------------        
          ##################-------------#####       
         ####################-----#############      
        #####################-##################     
        ##################-----#################     
       ################---------#################    
       #############-------------################    
       ###########----------------###############    
       #########------------------###############    
        ######---------------------###########       
        ####-----------------------########### T     
         ##-------------------------##########       
          --------------------------##########       
           -----------   -----------#########        
             --------- P -----------#######          
              --------   -----------######           
                 -------------------###              
                     --------------                  
                                                     
                                                     
                                                     
 Global CMT Convention Moment Tensor:
      R          T          P
 -1.77e+21   3.11e+21  -1.18e+21 
  3.11e+21  -4.82e+21   4.31e+21 
 -1.18e+21   4.31e+21   6.59e+21 


Details of the solution is found at

http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20130213095335/index.html
	
REVIEWED BY NSL STAFF

Event ID:402869
Origin ID:992305
Algorithm: Ichinose (2003) Long Period, Regional-Distance Waves
Seismic Moment Tensor Solution

2013/02/13 (044) 09:53:37.00 38.0317 -118.0549 992305
	Depth =   8.0 (km)
	Mw    =  3.85
	Mo    =  7.37x10^21 (dyne x cm)

	Percent Double Couple =  97 %
	Percent CLVD          =   3 %
	no ISO calculated
	Epsilon=-0.02
	 Percent Variance Reduction =  89.91 %
	 Total Fit                  =  20.05 
	Major Double Couple
		            strike dip   rake
		Nodal Plane 1: 338  71 -162
		Nodal Plane 2: 242  73  -20

	DEVIATORIC MOMENT TENSOR

	Moment Tensor Elements: Spherical Coordinates
		Mrr= -1.50 Mtt= -4.39 Mff=  5.89
		Mrt=  2.75 Mrf= -0.71 Mtf=  4.26 EXP=21


	Moment Tensor Elements: Cartesian Coordinates
		-4.39 -4.26  2.75
		-4.26  5.89  0.71
		 2.75  0.71 -1.50

	Eigenvalues:
		T-axis eigenvalue=  7.43
		N-axis eigenvalue= -0.13
		P-axis eigenvalue= -7.30

	Eigenvalues and eigenvectors of the Major Double Couple:
		T-axis ev= 7.43 trend=290 plunge=2
		N-axis ev= 0.00 trend=24 plunge=64
		P-axis ev=-7.43 trend=199 plunge=26

	Maximum Azmuithal Gap=154 Distance to Nearest Station= 77.9 (km)

	Number of Stations (D=Displacement/V=Velocity) Used=8 (defining only)
		
	 RYN.NN.D OMMB.NN.D KVN.NN.D GRA.CI.D
	 WAK.NN.D CWC.CI.D VCN.NN.D DAC.LB.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 	    77.9  	329  	148  	0.020 	0.080 RYN.NN.wus.glib
OMMB.NN (D) 	Y 	    95.3  	241  	 60  	0.020 	0.080 OMMB.NN.wus.glib
KVN.NN (D) 	Y 	   113.2  	358  	178  	0.020 	0.080 KVN.NN.wus.glib
GRA.CI (D) 	Y 	   129.6  	152  	332  	0.020 	0.080 GRA.CI.wus.glib
WAK.NN (D) 	Y 	   131.6  	294  	113  	0.020 	0.080 WAK.NN.wus.glib
CWC.CI (D) 	Y 	   176.9  	181  	  1  	0.020 	0.080 CWC.CI.wus.glib
VCN.NN (D) 	Y 	   197.5  	316  	135  	0.020 	0.080 VCN.NN.wus.glib
DAC.LB (D) 	Y 	   198.9  	168  	348  	0.020 	0.080 DAC.LB.wus.glib

 (V)-velocity (D)-Displacement

Author: www-data
Date: 2013/02/13 10:57:51

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:

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   230    65   -30   3.52 0.3599
WVFGRD96    1.0   235    70   -20   3.53 0.3842
WVFGRD96    2.0   235    70   -25   3.64 0.5074
WVFGRD96    3.0   235    60   -20   3.69 0.5488
WVFGRD96    4.0   235    60   -20   3.72 0.5842
WVFGRD96    5.0   235    65   -25   3.75 0.6155
WVFGRD96    6.0   235    65   -25   3.77 0.6438
WVFGRD96    7.0   240    70   -20   3.78 0.6674
WVFGRD96    8.0   235    60   -25   3.83 0.6860
WVFGRD96    9.0   235    60   -25   3.85 0.6974
WVFGRD96   10.0   235    65   -25   3.85 0.7036
WVFGRD96   11.0   240    70   -20   3.86 0.7068
WVFGRD96   12.0   240    70   -20   3.87 0.7075
WVFGRD96   13.0   240    70   -20   3.88 0.7052
WVFGRD96   14.0   240    70   -15   3.89 0.7020
WVFGRD96   15.0   240    70   -15   3.89 0.6966
WVFGRD96   16.0   240    70   -15   3.90 0.6900
WVFGRD96   17.0   240    70   -15   3.91 0.6823
WVFGRD96   18.0   240    75   -15   3.91 0.6736
WVFGRD96   19.0   240    75   -15   3.92 0.6645
WVFGRD96   20.0   240    75   -15   3.93 0.6549
WVFGRD96   21.0   240    75   -15   3.94 0.6451
WVFGRD96   22.0   240    75   -15   3.94 0.6347
WVFGRD96   23.0   240    75   -15   3.95 0.6237
WVFGRD96   24.0   240    75   -15   3.95 0.6124
WVFGRD96   25.0   240    75   -10   3.96 0.6009
WVFGRD96   26.0    65    75    15   3.97 0.5951
WVFGRD96   27.0    65    75    15   3.97 0.5846
WVFGRD96   28.0    65    75    15   3.98 0.5736
WVFGRD96   29.0    65    75    15   3.98 0.5622

The best solution is

WVFGRD96   12.0   240    70   -20   3.87 0.7075

The 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

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

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 00:20:29 CST 2015