Location

2012/11/10 17:08:12 37.135 -82.978 1.1 4.20 Kentucky

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  2012/11/10 17:08:12:0  37.13  -82.98   1.1 4.2 Kentucky
 
 Stations used:
   IU.SSPA IU.WCI IU.WVT NM.BLO NM.PLAL NM.SIUC NM.UTMT 
   TA.149A TA.150A TA.151A TA.152A TA.153A TA.154A TA.155A 
   TA.156A TA.251A TA.252A TA.254A TA.255A TA.256A TA.257A 
   TA.KMSC TA.L46A TA.L47A TA.L48A TA.L49A TA.M46A TA.M47A 
   TA.M48A TA.M50A TA.M51A TA.M54A TA.N47A TA.N48A TA.N49A 
   TA.N50A TA.N51A TA.N54A TA.O45A TA.O47A TA.O48A TA.O49A 
   TA.O50A TA.O51A TA.O52A TA.P43A TA.P44A TA.P45A TA.P46A 
   TA.P47A TA.P48A TA.P49A TA.P51A TA.P52A TA.P53A TA.Q43A 
   TA.Q44A TA.Q46A TA.Q47A TA.Q48A TA.Q49A TA.Q50A TA.Q51A 
   TA.Q52A TA.R44A TA.R45A TA.R46A TA.R47A TA.R48A TA.R49A 
   TA.R50A TA.R52A TA.R58B TA.S45A TA.S46A TA.S47A TA.S48A 
   TA.S49A TA.S51A TA.S52A TA.SFIN TA.T46A TA.T47A TA.T48A 
   TA.T50A TA.T51A TA.U46A TA.U47A TA.U48A TA.U50A TA.U51A 
   TA.U52A TA.U53A TA.V46A TA.V47A TA.V48A TA.V50A TA.V51A 
   TA.V52A TA.V53A TA.W45A TA.W46A TA.W47A TA.W48A TA.W49A 
   TA.W50A TA.W51A TA.W52A TA.W53A TA.X46A TA.X48A TA.X49A 
   TA.X51A TA.X52A TA.X53A TA.Y48A TA.Y49A TA.Y50A TA.Y51A 
   TA.Y52A TA.Y53A TA.Y54A TA.Z48A TA.Z49A TA.Z50A TA.Z51A 
   TA.Z52A TA.Z53A TA.Z54A TA.Z55A US.AAM US.ACSO US.BLA 
   US.CBN US.GOGA US.LRAL US.MCWV US.NHSC US.TZTN 
 
 Filtering commands used:
   hp c 0.02 n 3
   lp c 0.10 n 3
 
 Best Fitting Double Couple
  Mo = 2.19e+22 dyne-cm
  Mw = 4.16 
  Z  = 14 km
  Plane   Strike  Dip  Rake
   NP1      110    85   -30
   NP2      203    60   -174
  Principal Axes:
   Axis    Value   Plunge  Azimuth
    T   2.19e+22     17     160
    N   0.00e+00     60     281
    P  -2.19e+22     24      62

 Moment Tensor: (dyne-cm)
    Component   Value
       Mxx     1.38e+22
       Mxy    -1.38e+22
       Mxz    -9.56e+21
       Myy    -1.19e+22
       Myz    -5.24e+21
       Mzz    -1.90e+21
                                                     
                                                     
                                                     
                                                     
                     ##############                  
                 ################------              
              ################------------           
             ###############---------------          
           ###############-------------------        
          ###############---------------------       
         ###############-----------------   ---      
        --#############------------------ P ----     
        -----#########-------------------   ----     
       ----------####----------------------------    
       -------------##---------------------------    
       -------------#######----------------------    
       ------------#############-----------------    
        -----------###################----------     
        ----------###########################---     
         ---------#############################      
          --------############################       
           -------###########################        
             -----##############   ########          
              -----############# T #######           
                 --#############   ####              
                     ##############                  
                                                     
                                                     
                                                     
 Global CMT Convention Moment Tensor:
      R          T          P
 -1.90e+21  -9.56e+21   5.24e+21 
 -9.56e+21   1.38e+22   1.38e+22 
  5.24e+21   1.38e+22  -1.19e+22 


Details of the solution is found at

http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20121110170812/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 = 110
      DIP = 85
     RAKE = -30
       MW = 4.16
       HS = 14.0

The NDK file is 20121110170812.ndk The waveform inversion is preferred.

Moment Tensor Comparison

The following compares this source inversion to others
SLU
USGSMT
SLUFM
 USGS/SLU Moment Tensor Solution
 ENS  2012/11/10 17:08:12:0  37.13  -82.98   1.1 4.2 Kentucky
 
 Stations used:
   IU.SSPA IU.WCI IU.WVT NM.BLO NM.PLAL NM.SIUC NM.UTMT 
   TA.149A TA.150A TA.151A TA.152A TA.153A TA.154A TA.155A 
   TA.156A TA.251A TA.252A TA.254A TA.255A TA.256A TA.257A 
   TA.KMSC TA.L46A TA.L47A TA.L48A TA.L49A TA.M46A TA.M47A 
   TA.M48A TA.M50A TA.M51A TA.M54A TA.N47A TA.N48A TA.N49A 
   TA.N50A TA.N51A TA.N54A TA.O45A TA.O47A TA.O48A TA.O49A 
   TA.O50A TA.O51A TA.O52A TA.P43A TA.P44A TA.P45A TA.P46A 
   TA.P47A TA.P48A TA.P49A TA.P51A TA.P52A TA.P53A TA.Q43A 
   TA.Q44A TA.Q46A TA.Q47A TA.Q48A TA.Q49A TA.Q50A TA.Q51A 
   TA.Q52A TA.R44A TA.R45A TA.R46A TA.R47A TA.R48A TA.R49A 
   TA.R50A TA.R52A TA.R58B TA.S45A TA.S46A TA.S47A TA.S48A 
   TA.S49A TA.S51A TA.S52A TA.SFIN TA.T46A TA.T47A TA.T48A 
   TA.T50A TA.T51A TA.U46A TA.U47A TA.U48A TA.U50A TA.U51A 
   TA.U52A TA.U53A TA.V46A TA.V47A TA.V48A TA.V50A TA.V51A 
   TA.V52A TA.V53A TA.W45A TA.W46A TA.W47A TA.W48A TA.W49A 
   TA.W50A TA.W51A TA.W52A TA.W53A TA.X46A TA.X48A TA.X49A 
   TA.X51A TA.X52A TA.X53A TA.Y48A TA.Y49A TA.Y50A TA.Y51A 
   TA.Y52A TA.Y53A TA.Y54A TA.Z48A TA.Z49A TA.Z50A TA.Z51A 
   TA.Z52A TA.Z53A TA.Z54A TA.Z55A US.AAM US.ACSO US.BLA 
   US.CBN US.GOGA US.LRAL US.MCWV US.NHSC US.TZTN 
 
 Filtering commands used:
   hp c 0.02 n 3
   lp c 0.10 n 3
 
 Best Fitting Double Couple
  Mo = 2.19e+22 dyne-cm
  Mw = 4.16 
  Z  = 14 km
  Plane   Strike  Dip  Rake
   NP1      110    85   -30
   NP2      203    60   -174
  Principal Axes:
   Axis    Value   Plunge  Azimuth
    T   2.19e+22     17     160
    N   0.00e+00     60     281
    P  -2.19e+22     24      62

 Moment Tensor: (dyne-cm)
    Component   Value
       Mxx     1.38e+22
       Mxy    -1.38e+22
       Mxz    -9.56e+21
       Myy    -1.19e+22
       Myz    -5.24e+21
       Mzz    -1.90e+21
                                                     
                                                     
                                                     
                                                     
                     ##############                  
                 ################------              
              ################------------           
             ###############---------------          
           ###############-------------------        
          ###############---------------------       
         ###############-----------------   ---      
        --#############------------------ P ----     
        -----#########-------------------   ----     
       ----------####----------------------------    
       -------------##---------------------------    
       -------------#######----------------------    
       ------------#############-----------------    
        -----------###################----------     
        ----------###########################---     
         ---------#############################      
          --------############################       
           -------###########################        
             -----##############   ########          
              -----############# T #######           
                 --#############   ####              
                     ##############                  
                                                     
                                                     
                                                     
 Global CMT Convention Moment Tensor:
      R          T          P
 -1.90e+21  -9.56e+21   5.24e+21 
 -9.56e+21   1.38e+22   1.38e+22 
  5.24e+21   1.38e+22  -1.19e+22 


Details of the solution is found at

http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20121110170812/index.html
	

USGS/SLU Regional Moment Solution
EASTERN KENTUCKY

12/11/10 17:08:13.01

Epicenter:  37.110  -82.969
MW 4.2

USGS/SLU REGIONAL MOMENT TENSOR
Depth  16         No. of sta:105
Moment Tensor;   Scale 10**15 Nm
  Mrr=-0.67       Mtt= 1.89
  Mpp=-1.22       Mrt=-0.85
  Mrp= 0.87       Mtp= 1.44
 Principal axes:
  T  Val=  2.53  Plg= 9  Azm=161
  N       -0.04      56      265
  P       -2.49      32       65

Best Double Couple:Mo=2.5*10**15
 NP1:Strike=109 Dip=75 Slip= -30
 NP2:       208     61      -162


        


First motions and takeoff angles from an elocate run.

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:

hp c 0.02 n 3
lp c 0.10 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   295    90     0   3.92 0.4666
WVFGRD96    1.0   295    90   -20   3.96 0.4858
WVFGRD96    2.0   290    80   -25   4.00 0.5067
WVFGRD96    3.0   295    80    30   4.03 0.5216
WVFGRD96    4.0   110    90   -35   4.03 0.5381
WVFGRD96    5.0   110    90   -35   4.04 0.5615
WVFGRD96    6.0   110    90   -30   4.05 0.5863
WVFGRD96    7.0   110    90   -30   4.06 0.6094
WVFGRD96    8.0   110    85   -30   4.08 0.6305
WVFGRD96    9.0   110    85   -30   4.09 0.6486
WVFGRD96   10.0   290    90    30   4.11 0.6619
WVFGRD96   11.0   110    85   -30   4.13 0.6764
WVFGRD96   12.0   110    85   -30   4.14 0.6853
WVFGRD96   13.0   110    85   -30   4.15 0.6909
WVFGRD96   14.0   110    85   -30   4.16 0.6933
WVFGRD96   15.0   110    85   -30   4.17 0.6928
WVFGRD96   16.0   110    85   -30   4.18 0.6896
WVFGRD96   17.0   110    85   -30   4.19 0.6841
WVFGRD96   18.0   110    85   -30   4.20 0.6768
WVFGRD96   19.0   110    85   -30   4.20 0.6678
WVFGRD96   20.0   290    90    30   4.22 0.6543
WVFGRD96   21.0   110    85   -35   4.23 0.6450
WVFGRD96   22.0   110    85   -35   4.23 0.6327
WVFGRD96   23.0   110    85   -35   4.24 0.6191
WVFGRD96   24.0   110    85   -35   4.24 0.6048
WVFGRD96   25.0   110    90   -35   4.25 0.5908
WVFGRD96   26.0   290    90    35   4.25 0.5769
WVFGRD96   27.0   110    90   -35   4.26 0.5630
WVFGRD96   28.0   110    90   -35   4.26 0.5493
WVFGRD96   29.0   110    90   -35   4.27 0.5364

The best solution is

WVFGRD96   14.0   110    85   -30   4.16 0.6933

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 0.10 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.

Surface-Wave Focal Mechanism

The following figure shows the stations used in the grid search for the best focal mechanism to fit the surface-wave spectral amplitudes of the Love and Rayleigh waves.
Location of broadband stations used to obtain focal mechanism from surface-wave spectral amplitudes

The surface-wave determined focal mechanism is shown here.


  NODAL PLANES 

  
  STK=     112.87
  DIP=      85.46
 RAKE=     -25.08
  
             OR
  
  STK=     204.99
  DIP=      65.00
 RAKE=    -174.99
 
 
DEPTH = 14.0 km
 
Mw = 4.28
Best Fit 0.8225 - P-T axis plot gives solutions with FIT greater than FIT90

First motion data

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

Sta Az    Dist   First motion

Surface-wave analysis

Surface wave analysis was performed using codes from Computer Programs in Seismology, specifically the multiple filter analysis program do_mft and the surface-wave radiation pattern search program srfgrd96.

Data preparation

Digital data were collected, instrument response removed and traces converted to Z, R an T components. Multiple filter analysis was applied to the Z and T traces to obtain the Rayleigh- and Love-wave spectral amplitudes, respectively. These were input to the search program which examined all depths between 1 and 25 km and all possible mechanisms.
Best mechanism fit as a function of depth. The preferred depth is given above. Lower hemisphere projection

Pressure-tension axis trends. Since the surface-wave spectra search does not distinguish between P and T axes and since there is a 180 ambiguity in strike, all possible P and T axes are plotted. First motion data and waveforms will be used to select the preferred mechanism. The purpose of this plot is to provide an idea of the possible range of solutions. The P and T-axes for all mechanisms with goodness of fit greater than 0.9 FITMAX (above) are plotted here.


Focal mechanism sensitivity at the preferred depth. The red color indicates a very good fit to the Love and Rayleigh wave radiation patterns. 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. Because of the symmetry of the spectral amplitude rediation patterns, only strikes from 0-180 degrees are sampled.

Love-wave radiation patterns

Rayleigh-wave radiation patterns

Broadband station distribution

The distribution of broadband stations with azimuth and distance is
Listing of broadband stations used

Waveform comparison for this mechanism

Since the analysis of the surface-wave radiation patterns uses only spectral amplitudes and because the surfave-wave radiation patterns have a 180 degree symmetry, each surface-wave solution consists of four possible focal mechanisms corresponding to the interchange of the P- and T-axes and a roation of the mechanism by 180 degrees. To select one mechanism, P-wave first motion can be used. This was not possible in this case because all the P-wave first motions were emergent ( a feature of the P-wave wave takeoff angle, the station location and the mechanism). The other way to select among the mechanisms is to compute forward synthetics and compare the observed and predicted waveforms.

The fits to the waveforms with the given mechanism are show below:

This figure shows the fit to the three components of motion (Z - vertical, R-radial and T - transverse). For each station and component, the observed traces is shown in red and the model predicted trace in blue. The traces represent filtered ground velocity in units of meters/sec (the peak value is printed adjacent to each trace; each pair of traces to plotted to the same scale to emphasize the difference in levels). Both synthetic and observed traces have been filtered using the SAC commands:

hp c 0.02 n 3
lp c 0.10 n 3

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.

Appendix A


Spectra fit plots to each station

Velocity Model

The CUS model used for the waveform synthetic seismograms and for the surface wave eigenfunctions and dispersion is as follows:

MODEL.01
CUS Model with Q from simple gamma values
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
  1.0000  5.0000  2.8900  2.5000 0.172E-02 0.387E-02 0.00  0.00  1.00  1.00 
  9.0000  6.1000  3.5200  2.7300 0.160E-02 0.363E-02 0.00  0.00  1.00  1.00 
 10.0000  6.4000  3.7000  2.8200 0.149E-02 0.336E-02 0.00  0.00  1.00  1.00 
 20.0000  6.7000  3.8700  2.9020 0.000E-04 0.000E-04 0.00  0.00  1.00  1.00 
  0.0000  8.1500  4.7000  3.3640 0.194E-02 0.431E-02 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 00:26:04 CST 2015