Location

2013/08/29 11:20:18 39.081 -115.502 0.0 3.8 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  2013/08/29 11:20:18:0  39.08 -115.50   0.0 3.8 Nevada
 
 Stations used:
   NN.KVN NN.PAH NN.RUB NN.RYN NN.WAK TA.R11A UU.BGU UU.BRPU 
   UU.CCUT UU.KNB UU.MPU UU.PSUT UU.RDMU UU.SRU UU.TCRU 
   UW.IRON 
 
 Filtering commands used:
   cut a -30 a 180
   rtr
   taper w 0.1
   hp c 0.02 n 3 
   lp c 0.10 n 3 
   br c 0.12 0.25 n 4 p 2
 
 Best Fitting Double Couple
  Mo = 1.05e+21 dyne-cm
  Mw = 3.28 
  Z  = 10 km
  Plane   Strike  Dip  Rake
   NP1      345    70   -142
   NP2      240    55   -25
  Principal Axes:
   Axis    Value   Plunge  Azimuth
    T   1.05e+21      9     109
    N   0.00e+00     48       9
    P  -1.05e+21     41     208

 Moment Tensor: (dyne-cm)
    Component   Value
       Mxx    -3.61e+20
       Mxy    -5.69e+20
       Mxz     4.03e+20
       Myy     7.77e+20
       Myz     3.96e+20
       Mzz    -4.16e+20
                                                     
                                                     
                                                     
                                                     
                     ##------------                  
                 ########--------------              
              #############---------------           
             ###############---------------          
           ##################----------------        
          ###################-################       
         ################------################      
        ##############---------#################     
        ###########-------------################     
       ##########----------------################    
       ########------------------################    
       #######--------------------###############    
       ######---------------------###############    
        ####----------------------##########   #     
        ###-----------------------########## T #     
         #-----------   -----------#########         
          ----------- P -----------###########       
           ----------   -----------##########        
             ----------------------########          
              --------------------########           
                 -----------------#####              
                     -------------#                  
                                                     
                                                     
                                                     
 Global CMT Convention Moment Tensor:
      R          T          P
 -4.16e+20   4.03e+20  -3.96e+20 
  4.03e+20  -3.61e+20   5.69e+20 
 -3.96e+20   5.69e+20   7.77e+20 


Details of the solution is found at

http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20130829112018/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 = 55
     RAKE = -25
       MW = 3.28
       HS = 10.0

The NDK file is 20130829112018.ndk The waveform inversion is preferred.

Moment Tensor Comparison

The following compares this source inversion to others
SLU
USGSMT
 USGS/SLU Moment Tensor Solution
 ENS  2013/08/29 11:20:18:0  39.08 -115.50   0.0 3.8 Nevada
 
 Stations used:
   NN.KVN NN.PAH NN.RUB NN.RYN NN.WAK TA.R11A UU.BGU UU.BRPU 
   UU.CCUT UU.KNB UU.MPU UU.PSUT UU.RDMU UU.SRU UU.TCRU 
   UW.IRON 
 
 Filtering commands used:
   cut a -30 a 180
   rtr
   taper w 0.1
   hp c 0.02 n 3 
   lp c 0.10 n 3 
   br c 0.12 0.25 n 4 p 2
 
 Best Fitting Double Couple
  Mo = 1.05e+21 dyne-cm
  Mw = 3.28 
  Z  = 10 km
  Plane   Strike  Dip  Rake
   NP1      345    70   -142
   NP2      240    55   -25
  Principal Axes:
   Axis    Value   Plunge  Azimuth
    T   1.05e+21      9     109
    N   0.00e+00     48       9
    P  -1.05e+21     41     208

 Moment Tensor: (dyne-cm)
    Component   Value
       Mxx    -3.61e+20
       Mxy    -5.69e+20
       Mxz     4.03e+20
       Myy     7.77e+20
       Myz     3.96e+20
       Mzz    -4.16e+20
                                                     
                                                     
                                                     
                                                     
                     ##------------                  
                 ########--------------              
              #############---------------           
             ###############---------------          
           ##################----------------        
          ###################-################       
         ################------################      
        ##############---------#################     
        ###########-------------################     
       ##########----------------################    
       ########------------------################    
       #######--------------------###############    
       ######---------------------###############    
        ####----------------------##########   #     
        ###-----------------------########## T #     
         #-----------   -----------#########         
          ----------- P -----------###########       
           ----------   -----------##########        
             ----------------------########          
              --------------------########           
                 -----------------#####              
                     -------------#                  
                                                     
                                                     
                                                     
 Global CMT Convention Moment Tensor:
      R          T          P
 -4.16e+20   4.03e+20  -3.96e+20 
  4.03e+20  -3.61e+20   5.69e+20 
 -3.96e+20   5.69e+20   7.77e+20 


Details of the solution is found at

http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20130829112018/index.html
	
    NSL Moment Tensor Solution
    USGS/SLU Regional Moment Tensor Solution

Moment Tensor
NEIC Mwr
Contributed Solutions
Moment Tensor
Contributed Moment Tensors
 	Contributor	Code	Type	Magnitude	Depth	NP1	NP2
	us	nn00421825-neic-mwr	Mwr	3.3	11.0 km	355°, 61°, -137°	240°, 54°, -37°
us nn00421825-neic-mwr

Type
    Mwr
Moment
    1.22e+14 N-m
Magnitude
    3.3
Percent DC
    80%
Depth
    11.0 km
Author
    neic
Updated
    2013-08-29 16:03:22 UTC

Principal Axes
Axis	Value	Plunge	Azimuth
T	1.160	4°	116°
N	0.112	40°	23°
P	-1.272	50°	211°
Nodal Planes
Plane	Strike	Dip	Rake
NP1	355°	61°	-137°
NP2	240°	54°	-37°



        

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 0.10 n 3 
br c 0.12 0.25 n 4 p 2
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    60    85    -5   2.87 0.2007
WVFGRD96    1.0    60    90     0   2.92 0.2296
WVFGRD96    2.0    65    90    -5   3.04 0.3186
WVFGRD96    3.0    65    90   -10   3.10 0.3487
WVFGRD96    4.0    65    90   -20   3.14 0.3600
WVFGRD96    5.0   245    80    25   3.20 0.3779
WVFGRD96    6.0   250    70    30   3.22 0.3916
WVFGRD96    7.0   245    75    20   3.24 0.3980
WVFGRD96    8.0   250    70    30   3.27 0.4030
WVFGRD96    9.0   235    50   -35   3.29 0.4053
WVFGRD96   10.0   240    55   -25   3.28 0.4081
WVFGRD96   11.0   240    55   -25   3.29 0.4071
WVFGRD96   12.0   240    60   -25   3.30 0.4051
WVFGRD96   13.0   240    60   -25   3.30 0.4017
WVFGRD96   14.0   240    60   -20   3.31 0.3970
WVFGRD96   15.0   245    65   -20   3.31 0.3920
WVFGRD96   16.0   240    65   -25   3.33 0.3891
WVFGRD96   17.0   240    65   -25   3.34 0.3855
WVFGRD96   18.0   240    65   -25   3.35 0.3811
WVFGRD96   19.0   240    65   -25   3.36 0.3762
WVFGRD96   20.0   240    65   -30   3.36 0.3711
WVFGRD96   21.0   240    65   -30   3.37 0.3654
WVFGRD96   22.0   240    70   -30   3.39 0.3590
WVFGRD96   23.0   240    70   -35   3.39 0.3520
WVFGRD96   24.0   250    60    15   3.39 0.3459
WVFGRD96   25.0   250    60    15   3.40 0.3413
WVFGRD96   26.0   250    60    15   3.41 0.3369
WVFGRD96   27.0   260    55    35   3.41 0.3305
WVFGRD96   28.0   260    55    35   3.42 0.3266
WVFGRD96   29.0   260    55    35   3.43 0.3242

The best solution is

WVFGRD96   10.0   240    55   -25   3.28 0.4081

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 0.10 n 3 
br c 0.12 0.25 n 4 p 2
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 00:22:30 CST 2015