2010/01/15 15:27:02 35.569 -97.277 5.0 3.80 Oklahoma
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution ENS 2010/01/15 15:27:02:0 35.57 -97.28 5.0 3.8 Oklahoma Stations used: TA.133A TA.134A TA.135A TA.Q30A TA.Q31A TA.Q32A TA.Q33A TA.R30A TA.R31A TA.R32A TA.R33A TA.S30A TA.T30A TA.T31A TA.T32A TA.T33A TA.TUL1 TA.U29A TA.U30A TA.U31A TA.U32A TA.U33A TA.U34A TA.V30A TA.V33A TA.V34A TA.W32A TA.WHTX TA.X29A TA.X32A TA.X33A TA.X34A TA.Y33A TA.Y34A US.AMTX US.KSU1 Filtering commands used: 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 = 4.03e+21 dyne-cm Mw = 3.67 Z = 8 km Plane Strike Dip Rake NP1 135 85 30 NP2 42 60 174 Principal Axes: Axis Value Plunge Azimuth T 4.03e+21 24 3 N 0.00e+00 60 144 P -4.03e+21 17 265 Moment Tensor: (dyne-cm) Component Value Mxx 3.30e+21 Mxy -1.75e+20 Mxz 1.62e+21 Myy -3.65e+21 Myz 1.19e+21 Mzz 3.50e+20 ############## ########## ######### ############# T ############ -############# ############- ----###########################--- -------#########################---- ---------#######################------ ------------#####################------- --------------##################-------- ----------------################---------- -- -------------#############----------- -- P ---------------##########------------ -- -----------------#######------------- -----------------------###-------------- ------------------------#--------------- ---------------------#####------------ ------------------#########--------- --------------##############------ ---------####################- ############################ ###################### ############## Global CMT Convention Moment Tensor: R T P 3.50e+20 1.62e+21 -1.19e+21 1.62e+21 3.30e+21 1.75e+20 -1.19e+21 1.75e+20 -3.65e+21 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20100115152702/index.html |
STK = 135 DIP = 85 RAKE = 30 MW = 3.67 HS = 8.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution ENS 2010/01/15 15:27:02:0 35.57 -97.28 5.0 3.8 Oklahoma Stations used: TA.133A TA.134A TA.135A TA.Q30A TA.Q31A TA.Q32A TA.Q33A TA.R30A TA.R31A TA.R32A TA.R33A TA.S30A TA.T30A TA.T31A TA.T32A TA.T33A TA.TUL1 TA.U29A TA.U30A TA.U31A TA.U32A TA.U33A TA.U34A TA.V30A TA.V33A TA.V34A TA.W32A TA.WHTX TA.X29A TA.X32A TA.X33A TA.X34A TA.Y33A TA.Y34A US.AMTX US.KSU1 Filtering commands used: 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 = 4.03e+21 dyne-cm Mw = 3.67 Z = 8 km Plane Strike Dip Rake NP1 135 85 30 NP2 42 60 174 Principal Axes: Axis Value Plunge Azimuth T 4.03e+21 24 3 N 0.00e+00 60 144 P -4.03e+21 17 265 Moment Tensor: (dyne-cm) Component Value Mxx 3.30e+21 Mxy -1.75e+20 Mxz 1.62e+21 Myy -3.65e+21 Myz 1.19e+21 Mzz 3.50e+20 ############## ########## ######### ############# T ############ -############# ############- ----###########################--- -------#########################---- ---------#######################------ ------------#####################------- --------------##################-------- ----------------################---------- -- -------------#############----------- -- P ---------------##########------------ -- -----------------#######------------- -----------------------###-------------- ------------------------#--------------- ---------------------#####------------ ------------------#########--------- --------------##############------ ---------####################- ############################ ###################### ############## Global CMT Convention Moment Tensor: R T P 3.50e+20 1.62e+21 -1.19e+21 1.62e+21 3.30e+21 1.75e+20 -1.19e+21 1.75e+20 -3.65e+21 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20100115152702/index.html |
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.
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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 br c 0.12 0.25 n 4 p 2The results of this grid search from 0.5 to 19 km depth are as follow:
DEPTH STK DIP RAKE MW FIT WVFGRD96 0.5 310 75 -20 3.22 0.2374 WVFGRD96 1.0 130 90 5 3.26 0.2679 WVFGRD96 2.0 135 90 0 3.43 0.4474 WVFGRD96 3.0 135 85 -5 3.50 0.5114 WVFGRD96 4.0 135 80 -10 3.54 0.5414 WVFGRD96 5.0 135 75 -10 3.57 0.5542 WVFGRD96 6.0 135 85 30 3.62 0.5658 WVFGRD96 7.0 135 85 25 3.63 0.5732 WVFGRD96 8.0 135 85 30 3.67 0.5765 WVFGRD96 9.0 320 80 35 3.68 0.5743 WVFGRD96 10.0 320 80 30 3.69 0.5753 WVFGRD96 11.0 320 80 30 3.70 0.5739 WVFGRD96 12.0 320 80 25 3.71 0.5703 WVFGRD96 13.0 320 80 25 3.72 0.5657 WVFGRD96 14.0 320 85 25 3.73 0.5598 WVFGRD96 15.0 320 85 20 3.74 0.5532 WVFGRD96 16.0 320 85 20 3.75 0.5465 WVFGRD96 17.0 320 85 20 3.76 0.5390 WVFGRD96 18.0 320 85 20 3.77 0.5307 WVFGRD96 19.0 320 85 20 3.77 0.5215 WVFGRD96 20.0 320 85 15 3.78 0.5134 WVFGRD96 21.0 320 85 15 3.79 0.5046 WVFGRD96 22.0 140 75 15 3.80 0.4944 WVFGRD96 23.0 140 75 15 3.81 0.4853 WVFGRD96 24.0 320 85 15 3.81 0.4758 WVFGRD96 25.0 320 85 15 3.81 0.4661 WVFGRD96 26.0 320 85 15 3.82 0.4556 WVFGRD96 27.0 320 85 15 3.82 0.4454 WVFGRD96 28.0 320 85 10 3.83 0.4361 WVFGRD96 29.0 320 85 10 3.83 0.4270
The best solution is
WVFGRD96 8.0 135 85 30 3.67 0.5765
The mechanism correspond to the best fit is
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The best fit as a function of depth is given in the following figure:
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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 componnet is plotted to the same scale and peak amplitudes are indicated by the numbers to the left of each trace. The number in black at the rightr of each predicted traces 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 bandpass filter used in the processing and for the display was
hp c 0.02 n 3 lp c 0.10 n 3 br c 0.12 0.25 n 4 p 2
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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. |
Should the national backbone of the USGS Advanced National Seismic System (ANSS) be implemented with an interstation separation of 300 km, it is very likely that an earthquake such as this would have been recorded at distances on the order of 100-200 km. This means that the closest station would have information on source depth and mechanism that was lacking here.
Dr. Harley Benz, USGS, provided the USGS USNSN digital data. The digital data used in this study were provided by Natural Resources Canada through their AUTODRM site http://www.seismo.nrcan.gc.ca/nwfa/autodrm/autodrm_req_e.php, and IRIS using their BUD interface.
Thanks also to the many seismic network operators whose dedication make this effort possible: University of Alaska, University of Washington, Oregon State University, University of Utah, Montana Bureas of Mines, UC Berkely, Caltech, UC San Diego, Saint L ouis University, Universityof Memphis, Lamont Doehrty Earth Observatory, Boston College, the Iris stations and the Transportable Array of EarthScope.
The 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
Here we tabulate the reasons for not using certain digital data sets
The following stations did not have a valid response files:
DATE=Fri Jan 15 11:48:48 CST 2010