2010/02/13 05:30:55 35.5331 -97.2982 5.5 3.20 Oklahoma
Error Ellipse X= 0.3202 km Y= 0.3824 km Theta = 6.2905 deg RMS Error : 0.051 sec Travel_Time_Table: WUS Latitude : 35.5331 +- 0.0029 N 0.3210 km Longitude : -97.2982 +- 0.0042 E 0.3817 km Depth : 5.52 +- 0.42 km Epoch Time : 1266039055.968 +- 0.06 sec Event Time : 20100213053055.968 +- 0.06 sec Event (OCAL) : 2010 02 13 05 30 55 968 HYPO71 Quality : BA Gap : 84 deg
MAG DATE TIME(UT) LAT LON H State 3.2 2010/02/13 05:30:56 35.566 -97.215 5.0 OKLAHOMA
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution ENS 2010/02/13 05:30:55:9 35.53 -97.30 5.5 3.2 Oklahoma Stations used: GS.OK001 GS.OK002 GS.OK003 GS.OK004 GS.OK005 GS.OK006 Filtering commands used: hp c 0.50 n 2 lp c 1.00 n 2 br c 0.12 0.25 n 4 p 2 Best Fitting Double Couple Mo = 7.16e+20 dyne-cm Mw = 3.17 Z = 5 km Plane Strike Dip Rake NP1 57 80 -170 NP2 325 80 -10 Principal Axes: Axis Value Plunge Azimuth T 7.16e+20 0 191 N 0.00e+00 76 100 P -7.16e+20 14 281 Moment Tensor: (dyne-cm) Component Value Mxx 6.67e+20 Mxy 2.58e+20 Mxz -3.33e+19 Myy -6.24e+20 Myz 1.66e+20 Mzz -4.25e+19 ############## ###################### ----######################## -------####################### -----------####################### -------------#####################-- ----------------##################---- ------------------###############------- - ----------------###########--------- -- P -----------------#######------------- -- ------------------####--------------- ------------------------#----------------- ---------------------#####---------------- -----------------#########-------------- --------------#############------------- ----------#################----------- ----#######################--------- ###########################------- ##########################---- ##########################-- ###### ############# ## T ######### Global CMT Convention Moment Tensor: R T P -4.25e+19 -3.33e+19 -1.66e+20 -3.33e+19 6.67e+20 -2.58e+20 -1.66e+20 -2.58e+20 -6.24e+20 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20100213053055/index.html |
STK = 325 DIP = 80 RAKE = -10 MW = 3.17 HS = 5.0
A check on particle motion indicate that the trace with name HNZ was Z and HNE was E but the CMPINC and CMPAZ headers in the SAC file was not correctly set. The absolute time of GSOK002 was adjusted when the clock correction was determined. Green functions for the WUS model were recomputed with DT=0.05 sec. Finally to have a good S/N ratio the signal was filtered between 0.5 and 1.0 Hz, P-wave first arrivals hand picked, the time shift of the grid search severely restricted. The filtering was selected to have good S/N for the low frequency corner and still a simple waveform for the high frequency corner, Since high frequency fit is sensitive to the velocity model, or more precisely the ratio of distance to wavelength.
Finally the mechanism and depth are very similar to those of the 3 larger earthquakes in January in this source region.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution ENS 2010/02/13 05:30:55:9 35.53 -97.30 5.5 3.2 Oklahoma Stations used: GS.OK001 GS.OK002 GS.OK003 GS.OK004 GS.OK005 GS.OK006 Filtering commands used: hp c 0.50 n 2 lp c 1.00 n 2 br c 0.12 0.25 n 4 p 2 Best Fitting Double Couple Mo = 7.16e+20 dyne-cm Mw = 3.17 Z = 5 km Plane Strike Dip Rake NP1 57 80 -170 NP2 325 80 -10 Principal Axes: Axis Value Plunge Azimuth T 7.16e+20 0 191 N 0.00e+00 76 100 P -7.16e+20 14 281 Moment Tensor: (dyne-cm) Component Value Mxx 6.67e+20 Mxy 2.58e+20 Mxz -3.33e+19 Myy -6.24e+20 Myz 1.66e+20 Mzz -4.25e+19 ############## ###################### ----######################## -------####################### -----------####################### -------------#####################-- ----------------##################---- ------------------###############------- - ----------------###########--------- -- P -----------------#######------------- -- ------------------####--------------- ------------------------#----------------- ---------------------#####---------------- -----------------#########-------------- --------------#############------------- ----------#################----------- ----#######################--------- ###########################------- ##########################---- ##########################-- ###### ############# ## T ######### Global CMT Convention Moment Tensor: R T P -4.25e+19 -3.33e+19 -1.66e+20 -3.33e+19 6.67e+20 -2.58e+20 -1.66e+20 -2.58e+20 -6.24e+20 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20100213053055/index.html |
First motions plotted with waveform inversion nodal planes. Take-off angles are from WUS model and elocate run. |
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 0.50 n 2 lp c 1.00 n 2 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 0.5 150 90 0 2.42 0.2947 WVFGRD96 1.0 20 80 0 2.47 0.3078 WVFGRD96 2.0 290 55 -25 2.73 0.1387 WVFGRD96 3.0 325 80 -20 3.03 0.2812 WVFGRD96 4.0 325 80 -15 3.13 0.4226 WVFGRD96 5.0 325 80 -10 3.17 0.4562 WVFGRD96 6.0 325 75 -5 3.18 0.4549 WVFGRD96 7.0 325 65 0 3.19 0.4430 WVFGRD96 8.0 330 60 0 3.23 0.4255 WVFGRD96 9.0 330 65 0 3.29 0.4370 WVFGRD96 10.0 330 65 0 3.32 0.4253 WVFGRD96 11.0 330 65 0 3.34 0.4072 WVFGRD96 12.0 330 70 5 3.36 0.3641 WVFGRD96 13.0 335 70 5 3.36 0.3139 WVFGRD96 14.0 320 90 30 3.38 0.2995 WVFGRD96 15.0 340 55 15 3.23 0.1142 WVFGRD96 16.0 340 25 20 3.12 0.0631 WVFGRD96 17.0 345 25 25 3.12 0.0608 WVFGRD96 18.0 335 30 5 3.10 0.0457 WVFGRD96 19.0 110 75 0 3.22 0.0370
The best solution is
WVFGRD96 5.0 325 80 -10 3.17 0.4562
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 0.50 n 2 lp c 1.00 n 2 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 WUS 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:
Update time = Sat Feb 13 15:00:33 CST 2010 Here are the earthquakes appearing on this map, most recent at top ... MAG DATE LOCAL-TIME LAT LON DEPTH LOCATION y/m/d h:m:s deg deg km 3.2 2010/02/12 23:30:55 35.566N 97.215W 5.0 17 km (10 mi) SE of Arcadia, OK 2.5 2010/02/01 17:43:04 35.547N 97.236W 5.0 16 km (10 mi) SSE of Arcadia, OK 3.7 2010/01/24 01:14:51 35.517N 97.245W 5.0 12 km ( 7 mi) SSE of Arcadia, OK 3.8 2010/01/15 09:27:01 35.569N 97.277W 5.0 12 km ( 7 mi) SSE of Arcadia, OK 4.0 2010/01/15 09:18:25 35.574N 97.249W 5.0 10 km ( 6 mi) SE of Arcadia, OK 3.3 2010/01/14 04:05:34 35.539N 97.238W 5.0 8 km ( 5 mi) NNE of Arcadia, OK 2.8 2010/01/10 23:16:00 35.566N 97.287W 5.0 12 km ( 7 mi) SSE of Arcadia, OK 2.8 2010/01/01 12:45:51 35.634N 97.184W 5.0 13 km ( 8 mi) ESE of Arcadia, OK 3.0 2009/12/19 23:05:20 35.541N 97.298W 5.0 13 km ( 8 mi) E of Lake Aluma, OK 2.8 2009/12/17 20:25:39 35.542N 97.271W 5.0 15 km ( 9 mi) SSE of Arcadia, OK 2.2 2009/12/17 17:52:01 35.566N 97.287W 5.0 12 km ( 7 mi) SSE of Arcadia, OK 2.4 2009/12/15 09:39:15 35.576N 97.289W 5.0 11 km ( 7 mi) SSE of Arcadia, OK 3.4 2009/12/13 02:38:25 35.586N 97.277W 5.0 8 km ( 5 mi) SSE of Arcadia, OK 3.1 2009/12/12 05:34:05 35.556N 97.315W 5.0 9 km ( 6 mi) E of Lake Aluma, OK 2.8 2009/12/11 08:00:17 35.587N 97.324W 5.0 1 km ( 1 mi) NNE of Arcadia, OK 3.5 2009/12/07 11:44:25 35.559N 97.259W 5.0 13 km ( 8 mi) SSE of Arcadia, OK 3.0 2009/11/28 19:36:58 35.566N 97.274W 5.0 8 km ( 5 mi) SSE of Arcadia, OK 2.1 2009/11/25 10:51:39 35.529N 97.273W 5.0 14 km ( 9 mi) NE of Midwest City, OK 2.6 2009/11/22 23:47:12 35.493N 97.230W 5.0 16 km (10 mi) ENE of Midwest City, OK 2.5 2009/11/16 05:12:37 35.493N 97.230W 5.0 16 km (10 mi) ENE of Midwest City, OK 3.0 2009/11/14 05:13:01 35.524N 97.219W 5.0 18 km (11 mi) ENE of Midwest City, OK 2.7 2009/11/02 12:27:05 35.432N 96.550W 5.0 17 km (11 mi) WNW of Bearden, OK 3.0 2009/10/22 22:56:29 35.794N 97.017W 5.0 10 km ( 6 mi) ESE of Fallis, OK 2.3 2009/09/08 09:03:12 35.633N 97.205W 5.0 12 km ( 7 mi) ESE of Arcadia, OK 2.3 2009/08/27 23:15:50 35.566N 97.290W 5.0 12 km ( 7 mi) SSE of Arcadia, OK 2.4 2009/08/27 22:30:55 35.566N 97.290W 5.0 12 km ( 7 mi) SSE of Arcadia, OK 3.5 2009/08/27 21:09:06 35.565N 97.290W 5.0 12 km ( 7 mi) SSE of Arcadia, OK 2.7 2009/08/27 13:32:06 35.566N 97.290W 5.0 12 km ( 7 mi) SSE of Arcadia, OK 2.6 2009/08/27 12:13:52 35.566N 97.290W 5.0 12 km ( 7 mi) SSE of Arcadia, OK 2.5 2009/08/27 10:31:24 35.566N 97.290W 5.0 12 km ( 7 mi) SSE of Arcadia, OK 2.7 2009/08/27 10:17:52 35.566N 97.290W 5.0 12 km ( 7 mi) SSE of Arcadia, OK 2.5 2009/08/27 07:58:25 35.566N 97.290W 5.0 12 km ( 7 mi) SSE of Arcadia, OKDATE=Sun Feb 14 11:46:48 CST 2010