Location

2016/02/13 17:07:06 36.472 -98.681 2.0 5.1 Oklahoma

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  2016/02/13 17:07:06:0  36.47  -98.68   2.0 5.1 Oklahoma
 
 Stations used:
   AG.HHAR GS.KAN01 GS.KAN05 GS.KAN06 GS.KAN08 GS.KAN10 
   GS.KAN11 GS.KAN12 GS.KAN13 GS.KAN14 GS.KAN16 GS.KAN17 
   GS.OK025 GS.OK029 GS.OK030 GS.OK031 GS.OK032 GS.OK033 
   GS.OK034 GS.OK035 N4.N33B N4.R32B N4.S39B N4.T35B N4.U38B 
   OK.BCOK OK.BLOK OK.CCOK OK.CHOK OK.CROK OK.FNO OK.GORE 
   OK.OKCFA OK.QUOK OK.RLOK OK.U32A OK.W35A OK.X34A OK.X37A 
   TA.ABTX TA.BGNE TA.KSCO TA.MSTX TA.T25A TA.TUL1 TA.U40A 
   TA.W39A US.AMTX US.CBKS US.KSU1 US.MIAR US.WMOK 
 
 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 
 
 Best Fitting Double Couple
  Mo = 3.98e+23 dyne-cm
  Mw = 5.00 
  Z  = 9 km
  Plane   Strike  Dip  Rake
   NP1       42    80   -170
   NP2      310    80   -10
  Principal Axes:
   Axis    Value   Plunge  Azimuth
    T   3.98e+23      0     176
    N   0.00e+00     76      85
    P  -3.98e+23     14     266

 Moment Tensor: (dyne-cm)
    Component   Value
       Mxx     3.94e+23
       Mxy    -5.54e+22
       Mxz     6.00e+21
       Myy    -3.70e+23
       Myz     9.39e+22
       Mzz    -2.36e+22
                                                     
                                                     
                                                     
                                                     
                     ##############                  
                 ######################              
              ############################           
             ############################--          
           ----#########################-----        
          --------#####################-------       
         ------------#################---------      
        ----------------############------------     
        ------------------#########-------------     
       ----------------------#####---------------    
       -   --------------------#-----------------    
       - P --------------------##----------------    
       -   ------------------######--------------    
        -------------------##########-----------     
        -----------------##############---------     
         --------------#################-------      
          -----------#####################----       
           --------########################--        
             ----##########################          
              ############################           
                 ###########   ########              
                     ####### T ####                  
                                                     
                                                     
                                                     
 Global CMT Convention Moment Tensor:
      R          T          P
 -2.36e+22   6.00e+21  -9.39e+22 
  6.00e+21   3.94e+23   5.54e+22 
 -9.39e+22   5.54e+22  -3.70e+23 


Details of the solution is found at

http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20160213170706/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 = 310
      DIP = 80
     RAKE = -10
       MW = 5.00
       HS = 9.0

The NDK file is 20160213170706.ndk The waveform inversion is preferred.

Moment Tensor Comparison

The following compares this source inversion to others
SLU
USGSMT
USGSW
 USGS/SLU Moment Tensor Solution
 ENS  2016/02/13 17:07:06:0  36.47  -98.68   2.0 5.1 Oklahoma
 
 Stations used:
   AG.HHAR GS.KAN01 GS.KAN05 GS.KAN06 GS.KAN08 GS.KAN10 
   GS.KAN11 GS.KAN12 GS.KAN13 GS.KAN14 GS.KAN16 GS.KAN17 
   GS.OK025 GS.OK029 GS.OK030 GS.OK031 GS.OK032 GS.OK033 
   GS.OK034 GS.OK035 N4.N33B N4.R32B N4.S39B N4.T35B N4.U38B 
   OK.BCOK OK.BLOK OK.CCOK OK.CHOK OK.CROK OK.FNO OK.GORE 
   OK.OKCFA OK.QUOK OK.RLOK OK.U32A OK.W35A OK.X34A OK.X37A 
   TA.ABTX TA.BGNE TA.KSCO TA.MSTX TA.T25A TA.TUL1 TA.U40A 
   TA.W39A US.AMTX US.CBKS US.KSU1 US.MIAR US.WMOK 
 
 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 
 
 Best Fitting Double Couple
  Mo = 3.98e+23 dyne-cm
  Mw = 5.00 
  Z  = 9 km
  Plane   Strike  Dip  Rake
   NP1       42    80   -170
   NP2      310    80   -10
  Principal Axes:
   Axis    Value   Plunge  Azimuth
    T   3.98e+23      0     176
    N   0.00e+00     76      85
    P  -3.98e+23     14     266

 Moment Tensor: (dyne-cm)
    Component   Value
       Mxx     3.94e+23
       Mxy    -5.54e+22
       Mxz     6.00e+21
       Myy    -3.70e+23
       Myz     9.39e+22
       Mzz    -2.36e+22
                                                     
                                                     
                                                     
                                                     
                     ##############                  
                 ######################              
              ############################           
             ############################--          
           ----#########################-----        
          --------#####################-------       
         ------------#################---------      
        ----------------############------------     
        ------------------#########-------------     
       ----------------------#####---------------    
       -   --------------------#-----------------    
       - P --------------------##----------------    
       -   ------------------######--------------    
        -------------------##########-----------     
        -----------------##############---------     
         --------------#################-------      
          -----------#####################----       
           --------########################--        
             ----##########################          
              ############################           
                 ###########   ########              
                     ####### T ####                  
                                                     
                                                     
                                                     
 Global CMT Convention Moment Tensor:
      R          T          P
 -2.36e+22   6.00e+21  -9.39e+22 
  6.00e+21   3.94e+23   5.54e+22 
 -9.39e+22   5.54e+22  -3.70e+23 


Details of the solution is found at

http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20160213170706/index.html
	
Regional Moment Tensor (Mwr)
Moment	4.988e+16 N-m
Magnitude	5.07
Depth	8.0 km
Percent DC	90%
Half Duration	–
Catalog	US (us20004zy8)
Data Source	US1
Contributor	US1
Nodal Planes
Plane	Strike	Dip	Rake
NP1	311	70	-19
NP2	47	72	-159
Principal Axes
Axis	Value	Plunge	Azimuth
T	5.112	1	179
N	-0.259	62	86
P	-4.853	27	269

        
W-phase Moment Tensor (Mww)
Moment	6.159e+16 N-m
Magnitude	5.13
Depth	11.5 km
Percent DC	99%
Half Duration	–
Catalog	US (us20004zy8)
Data Source	US1
Contributor	US1
Nodal Planes
Plane	Strike	Dip	Rake
NP1	46	66	-164
NP2	309	75	-25

        

Magnitudes

mLg Magnitude


(a) mLg computed using the IASPEI formula; (b) mLg residuals ; the values used for the trimmed mean are indicated.

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 
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   310    85    -5   4.65 0.4169
WVFGRD96    2.0   315    85     5   4.77 0.5625
WVFGRD96    3.0   315    80     5   4.83 0.6253
WVFGRD96    4.0   315    75     5   4.87 0.6662
WVFGRD96    5.0   310    75   -10   4.90 0.6953
WVFGRD96    6.0   310    80   -10   4.93 0.7167
WVFGRD96    7.0   310    80   -10   4.95 0.7327
WVFGRD96    8.0   310    75   -10   4.98 0.7436
WVFGRD96    9.0   310    80   -10   5.00 0.7442
WVFGRD96   10.0   310    80   -10   5.02 0.7417
WVFGRD96   11.0   310    80   -10   5.03 0.7368
WVFGRD96   12.0   310    80   -10   5.04 0.7295
WVFGRD96   13.0   310    80   -10   5.05 0.7197
WVFGRD96   14.0   310    80   -10   5.06 0.7084
WVFGRD96   15.0   310    80   -10   5.07 0.6962
WVFGRD96   16.0   310    80    -5   5.08 0.6831
WVFGRD96   17.0   310    80    -5   5.09 0.6695
WVFGRD96   18.0   135    85   -10   5.09 0.6578
WVFGRD96   19.0   135    85   -10   5.10 0.6461
WVFGRD96   20.0   135    85   -10   5.11 0.6339
WVFGRD96   21.0   130    80   -10   5.12 0.6219
WVFGRD96   22.0   130    80   -10   5.12 0.6089
WVFGRD96   23.0   130    80   -10   5.13 0.5964
WVFGRD96   24.0   130    80   -10   5.14 0.5833
WVFGRD96   25.0   130    80   -10   5.14 0.5708
WVFGRD96   26.0   130    80   -10   5.15 0.5582
WVFGRD96   27.0   130    80   -10   5.15 0.5463
WVFGRD96   28.0   130    80   -10   5.16 0.5346
WVFGRD96   29.0   130    80   -10   5.16 0.5232

The best solution is

WVFGRD96    9.0   310    80   -10   5.00 0.7442

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 
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.

Accelerometer data

This event was well recorded on many HN channels. The source inversion was performed using these and some nearby broadband channels to check on amplitudes and to see if the strong motion sensors could define the mechanism. The filter used was
cut o DIST/3.3 -30 o DIST/3.3 +70
rtr
taper w 0.1
hp c 0.05 n 3 
lp c 0.25 n 3 
and the waveforms were
ADOKGSHNR	BCOKOKHHZ	KAN01GS01HNT	KAN08GS01HNR	KAN12GS01HNZ	KAN16GS01HNT	OK914NQ01HNR	U32AOKBHZ
ADOKGSHNT	CCOKOKHHR	KAN01GS01HNZ	KAN08GS01HNT	KAN13GS01HNR	KAN16GS01HNZ	OK914NQ01HNT	VLBCNQ01HNR
ADOKGSHNZ	CCOKOKHHT	KAN02NQ02HNR	KAN08GS01HNZ	KAN13GS01HNT	KAN17GS01HNR	OK914NQ01HNZ	VLBCNQ01HNT
AZEPNQ01HNR	CCOKOKHHZ	KAN02NQ02HNT	KAN10GS01HNR	KAN13GS01HNZ	KAN17GS01HNT	OK915NQ01HNR	VLBCNQ01HNZ
AZEPNQ01HNT	CROKOKHHR	KAN02NQ02HNZ	KAN10GS01HNT	KAN14GS01HNR	KAN17GS01HNZ	OK915NQ01HNT	VMTWNQ01HNR
AZEPNQ01HNZ	CROKOKHHT	KAN05GS01HNR	KAN10GS01HNZ	KAN14GS01HNT	OK025GS00HHR	OK915NQ01HNZ	VMTWNQ01HNT
AZNHNQ01HNR	CROKOKHHZ	KAN05GS01HNT	KAN11GS01HNR	KAN14GS01HNZ	OK025GS00HHT	RESDNQ01HNR	VMTWNQ01HNZ
AZNHNQ01HNT	GOREOKHHR	KAN05GS01HNZ	KAN11GS01HNT	KAN15NQ01HNR	OK025GS00HHZ	RESDNQ01HNT
AZNHNQ01HNZ	GOREOKHHT	KAN06GS01HNR	KAN11GS01HNZ	KAN15NQ01HNT	OK029GS00HHR	RESDNQ01HNZ
BCOKOKHHR	GOREOKHHZ	KAN06GS01HNT	KAN12GS01HNR	KAN15NQ01HNZ	OK029GS00HHT	U32AOKBHR
BCOKOKHHT	KAN01GS01HNR	KAN06GS01HNZ	KAN12GS01HNT	KAN16GS01HNR	OK029GS00HHZ	U32AOKBHT
The location of these stations are shown on the following map:

The broadband channels (BH and HH) were included to provide some azimuthal control. The best solution was
WVFGRD96    7.0    45    85    15   4.86 0.438
which is similar to the broadband solution given above except that the pressure and tension axs are interchanged. The comparison of observed and predicted waveforms is given the enxt figure.

The first are good, except that KN02 requires a large tiem shift. At these shorter periods we get a smaller moment magnitude and a reversed mechanism. The reason for the reverse mechanism is that this mechanism is based on the fit to the dispersed surface waves along a path for which the velocity model is not calibrated. It does not take much of a change in the pahse velocity over 100 or so km at a period of seconds to introduce a phase change of 180 degrees. The mechanism and the goordness of fit with depth are shown in the next figure. To focus on the timeing at the NetQuake station KAN02, the transverse component is compared to neighboring stations in the 0.05 - 0.5 Hz band. The stations are aligned on the WUS model predicted S-arrival time, and the distances are
KAN11GS01HNT : DIST             106.4116
KAN12GS01HNT : DIST             109.9865
KAN01GS01HNT : DIST             111.7444
KAN06GS01HNT : DIST             113.1115
KAN13GS01HNT : DIST             123.0842
KAN02NQ02HNT : DIST             125.5088
KAN15NQ01HNT : DIST             134.9048

First motion data

The P-wave first motion data for focal mechanism studies are as follow:

Sta Az    Dist   First motion

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 Sat Feb 13 20:37:08 CST 2016