Location

2014/12/29 06:08:18 39.664 -111.972 3.9 3.7 Utah

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  2014/12/29 06:08:18:0  39.66 -111.97   3.9 3.7 Utah
 
 Stations used:
   AE.U15A AE.W13A AE.X18A CI.LDF IM.PD31 IW.FLWY IW.LOHW 
   IW.MFID IW.MOOW IW.REDW IW.RWWY IW.SMCO LB.TPH NN.LHV 
   NN.PRN NN.RYN NN.SHP RE.PV04 RE.PV12 RE.PV14 RE.PV16 
   RE.PV17 RE.PV19 RE.PV22 TA.K22A TA.N23A TA.O20A TA.Q24A 
   TA.R11A TA.S22A TA.W18A US.BW06 US.DUG US.ELK US.HLID 
   US.ISCO US.MVCO US.TPNV UU.BGU UU.BRPU UU.CCUT UU.HVU 
   UU.JLU UU.KNB UU.LCMT UU.MTPU UU.PKCU UU.PSUT UU.RDMU 
   UU.SPU UU.SRU UU.SZCU UU.TCRU UU.TCU UU.TMU UU.VRUT WY.YHH 
   WY.YMP WY.YMR WY.YNR WY.YPP 
 
 Filtering commands used:
   cut o DIST/3.3 -30 o DIST/3.3 +70
   rtr
   taper w 0.1
   hp c 0.03 n 3 
   lp c 0.07 n 3 
   br c 0.12 0.25 n 4 p 2
 
 Best Fitting Double Couple
  Mo = 6.31e+21 dyne-cm
  Mw = 3.80 
  Z  = 3 km
  Plane   Strike  Dip  Rake
   NP1      174    46   -80
   NP2      340    45   -100
  Principal Axes:
   Axis    Value   Plunge  Azimuth
    T   6.31e+21      0     257
    N   0.00e+00      7     347
    P  -6.31e+21     83     163

 Moment Tensor: (dyne-cm)
    Component   Value
       Mxx     2.29e+20
       Mxy     1.40e+21
       Mxz     7.28e+20
       Myy     5.98e+21
       Myz    -2.65e+20
       Mzz    -6.21e+21
                                                     
                                                     
                                                     
                                                     
                     #--###########                  
                 #####-----############              
              #######---------############           
             #######------------###########          
           ########---------------###########        
          ########-----------------###########       
         #########------------------###########      
        #########--------------------###########     
        #########---------------------##########     
       ##########----------------------##########    
       ##########----------------------##########    
       ##########----------   ----------#########    
          #######---------- P ----------#########    
        T ########---------   ----------########     
          ########----------------------########     
         ##########---------------------#######      
          ##########--------------------######       
           ##########------------------######        
             #########-----------------####          
              #########---------------####           
                 ########------------##              
                     #######-------                  
                                                     
                                                     
                                                     
 Global CMT Convention Moment Tensor:
      R          T          P
 -6.21e+21   7.28e+20   2.65e+20 
  7.28e+20   2.29e+20  -1.40e+21 
  2.65e+20  -1.40e+21   5.98e+21 


Details of the solution is found at

http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20141229060818/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 = 340
      DIP = 45
     RAKE = -100
       MW = 3.80
       HS = 3.0

The NDK file is 20141229060818.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  2014/12/29 06:08:18:0  39.66 -111.97   3.9 3.7 Utah
 
 Stations used:
   AE.U15A AE.W13A AE.X18A CI.LDF IM.PD31 IW.FLWY IW.LOHW 
   IW.MFID IW.MOOW IW.REDW IW.RWWY IW.SMCO LB.TPH NN.LHV 
   NN.PRN NN.RYN NN.SHP RE.PV04 RE.PV12 RE.PV14 RE.PV16 
   RE.PV17 RE.PV19 RE.PV22 TA.K22A TA.N23A TA.O20A TA.Q24A 
   TA.R11A TA.S22A TA.W18A US.BW06 US.DUG US.ELK US.HLID 
   US.ISCO US.MVCO US.TPNV UU.BGU UU.BRPU UU.CCUT UU.HVU 
   UU.JLU UU.KNB UU.LCMT UU.MTPU UU.PKCU UU.PSUT UU.RDMU 
   UU.SPU UU.SRU UU.SZCU UU.TCRU UU.TCU UU.TMU UU.VRUT WY.YHH 
   WY.YMP WY.YMR WY.YNR WY.YPP 
 
 Filtering commands used:
   cut o DIST/3.3 -30 o DIST/3.3 +70
   rtr
   taper w 0.1
   hp c 0.03 n 3 
   lp c 0.07 n 3 
   br c 0.12 0.25 n 4 p 2
 
 Best Fitting Double Couple
  Mo = 6.31e+21 dyne-cm
  Mw = 3.80 
  Z  = 3 km
  Plane   Strike  Dip  Rake
   NP1      174    46   -80
   NP2      340    45   -100
  Principal Axes:
   Axis    Value   Plunge  Azimuth
    T   6.31e+21      0     257
    N   0.00e+00      7     347
    P  -6.31e+21     83     163

 Moment Tensor: (dyne-cm)
    Component   Value
       Mxx     2.29e+20
       Mxy     1.40e+21
       Mxz     7.28e+20
       Myy     5.98e+21
       Myz    -2.65e+20
       Mzz    -6.21e+21
                                                     
                                                     
                                                     
                                                     
                     #--###########                  
                 #####-----############              
              #######---------############           
             #######------------###########          
           ########---------------###########        
          ########-----------------###########       
         #########------------------###########      
        #########--------------------###########     
        #########---------------------##########     
       ##########----------------------##########    
       ##########----------------------##########    
       ##########----------   ----------#########    
          #######---------- P ----------#########    
        T ########---------   ----------########     
          ########----------------------########     
         ##########---------------------#######      
          ##########--------------------######       
           ##########------------------######        
             #########-----------------####          
              #########---------------####           
                 ########------------##              
                     #######-------                  
                                                     
                                                     
                                                     
 Global CMT Convention Moment Tensor:
      R          T          P
 -6.21e+21   7.28e+20   2.65e+20 
  7.28e+20   2.29e+20  -1.40e+21 
  2.65e+20  -1.40e+21   5.98e+21 


Details of the solution is found at

http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20141229060818/index.html
	
Moment
7.11e+14 N-m
Magnitude
3.8
Percent DC
84%
Depth
3.0 km
Updated
2014-12-30 02:27:21 UTC
Author
us
Catalog
Contributor
us
Code
us_c000taht_mwr
Principal Axes

Axis	Value	Plunge	Azimuth
T	6.834	1	257
N	0.530	14	167
P	-7.364	76	350
Nodal Planes

Plane	Strike	Dip	Rake
NP1	153	47	-110
NP2	1	46	-70


        

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 o DIST/3.3 -30 o DIST/3.3 +70
rtr
taper w 0.1
hp c 0.03 n 3 
lp c 0.07 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    1.0   180    45   -70   3.65 0.5541
WVFGRD96    2.0   180    45   -70   3.75 0.6934
WVFGRD96    3.0   340    45  -100   3.80 0.6992
WVFGRD96    4.0   175    45   -80   3.83 0.6451
WVFGRD96    5.0   340    65   -95   3.87 0.6063
WVFGRD96    6.0    20    70   -50   3.77 0.5717
WVFGRD96    7.0    30    85   -40   3.75 0.5711
WVFGRD96    8.0   -10    65   -80   3.88 0.5764
WVFGRD96    9.0    25    80   -45   3.79 0.5716
WVFGRD96   10.0    25    80   -45   3.80 0.5712
WVFGRD96   11.0   220    70    35   3.81 0.5743
WVFGRD96   12.0   220    70    35   3.82 0.5798
WVFGRD96   13.0   220    70    35   3.82 0.5831
WVFGRD96   14.0   220    70    35   3.83 0.5847
WVFGRD96   15.0   220    70    35   3.84 0.5849
WVFGRD96   16.0   220    70    35   3.85 0.5839
WVFGRD96   17.0   220    70    35   3.85 0.5822
WVFGRD96   18.0   220    70    35   3.86 0.5796
WVFGRD96   19.0   220    70    35   3.87 0.5764
WVFGRD96   20.0    20    70   -35   3.88 0.5730
WVFGRD96   21.0    20    70   -40   3.89 0.5706
WVFGRD96   22.0    20    70   -40   3.90 0.5672
WVFGRD96   23.0    20    70   -40   3.90 0.5631
WVFGRD96   24.0    20    70   -40   3.91 0.5590
WVFGRD96   25.0    20    70   -40   3.92 0.5548
WVFGRD96   26.0    20    70   -40   3.93 0.5499
WVFGRD96   27.0    20    65   -40   3.94 0.5450
WVFGRD96   28.0    20    65   -40   3.95 0.5400
WVFGRD96   29.0    20    65   -40   3.95 0.5345

The best solution is

WVFGRD96    3.0   340    45  -100   3.80 0.6992

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 0.03 n 3 
lp c 0.07 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 00:20:02 CST 2015