1999/07/03 01:43:54 47.076 -123.463 40.0 5.40 Washington
USGS Felt map for this earthquake
USGS Felt reports page for Pacific Northwest
SLU Moment Tensor Solution 1999/07/03 01:43:54 47.076 -123.463 40.0 5.40 Washington Best Fitting Double Couple Mo = 4.95e+24 dyne-cm Mw = 5.73 Z = 45 km Plane Strike Dip Rake NP1 165 50 -95 NP2 353 40 -84 Principal Axes: Axis Value Plunge Azimuth T 4.95e+24 5 259 N 0.00e+00 4 168 P -4.95e+24 84 40 Moment Tensor: (dyne-cm) Component Value Mxx 1.60e+23 Mxy 9.29e+23 Mxz -4.90e+23 Myy 4.70e+24 Myz -7.56e+23 Mzz -4.86e+24 #------####### ####----------######## ######--------------######## ######----------------######## #######-------------------######## ########--------------------######## ########---------------------######### #########----------------------######### #########------------ --------######## ##########------------ P --------######### ###########----------- --------######### ###########----------------------######### ########----------------------######### T #########---------------------######## ##########--------------------######## ###########--------------------####### ###########------------------####### ############---------------####### ###########-------------###### ############----------###### ###########------##### ############## Harvard Convention Moment Tensor: R T F -4.86e+24 -4.90e+23 7.56e+23 -4.90e+23 1.60e+23 -9.29e+23 7.56e+23 -9.29e+23 4.70e+24 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/19990703014354/index.html |
STK = 165 DIP = 50 RAKE = -95 MW = 5.73 HS = 45.0
The waveform inversion is preferred. The fits for the filter band 0.02 - 0.10 were very good for the detail match of the body waves at COR and other short distances.
The following compares this source inversion to others
SLU Moment Tensor Solution 1999/07/03 01:43:54 47.076 -123.463 40.0 5.40 Washington Best Fitting Double Couple Mo = 4.95e+24 dyne-cm Mw = 5.73 Z = 45 km Plane Strike Dip Rake NP1 165 50 -95 NP2 353 40 -84 Principal Axes: Axis Value Plunge Azimuth T 4.95e+24 5 259 N 0.00e+00 4 168 P -4.95e+24 84 40 Moment Tensor: (dyne-cm) Component Value Mxx 1.60e+23 Mxy 9.29e+23 Mxz -4.90e+23 Myy 4.70e+24 Myz -7.56e+23 Mzz -4.86e+24 #------####### ####----------######## ######--------------######## ######----------------######## #######-------------------######## ########--------------------######## ########---------------------######### #########----------------------######### #########------------ --------######## ##########------------ P --------######### ###########----------- --------######### ###########----------------------######### ########----------------------######### T #########---------------------######## ##########--------------------######## ###########--------------------####### ###########------------------####### ############---------------####### ###########-------------###### ############----------###### ###########------##### ############## Harvard Convention Moment Tensor: R T F -4.86e+24 -4.90e+23 7.56e+23 -4.90e+23 1.60e+23 -9.29e+23 7.56e+23 -9.29e+23 4.70e+24 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/19990703014354/index.html |
Global CMT Best Fitting Double Couple Mo = 5.62e+24 dyne-cm Mw = 5.80 Z = 45 km Plane Strike Dip Rake NP1 345 61 -108 NP2 199 34 -61 Principal Axes: Axis Value Plunge Azimuth T 5.62e+24 14 88 N 0.00e+00 16 354 P -5.62e+24 69 218 Moment Tensor: (dyne-cm) Component Value Mxx -4.55e+23 Mxy -2.02e+23 Mxz 1.54e+24 Myy 5.02e+24 Myz 2.48e+24 Mzz -4.56e+24 ###--------### ###################### #########-----############## ########---------############# ########------------############## ########--------------############## ########----------------############## ########------------------############## #######-------------------############## #######---------------------########## # #######---------------------########## T # #######----------------------######### # #######--------- ----------############# ######--------- P ----------############ ######--------- ----------############ #####----------------------########### #####---------------------########## ####---------------------######### ###--------------------####### ###------------------####### ##----------------#### -------------# Harvard Convention Moment Tensor: R T F -4.56e+24 1.54e+24 -2.48e+24 1.54e+24 -4.55e+23 2.02e+23 -2.48e+24 2.02e+23 5.02e+24 |
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 0.01 n 3 lp c 0.06 n 3The results of this grid search from 0.5 to 19 km depth are as follow:
DEPTH STK DIP RAKE MW FIT WVFGRD96 0.5 345 40 90 4.99 0.2413 WVFGRD96 1.0 170 45 90 5.05 0.2709 WVFGRD96 2.0 170 45 90 5.14 0.3333 WVFGRD96 3.0 185 45 100 5.23 0.3753 WVFGRD96 4.0 190 45 105 5.28 0.3555 WVFGRD96 5.0 330 55 40 5.27 0.3034 WVFGRD96 6.0 320 75 10 5.28 0.2721 WVFGRD96 7.0 320 80 0 5.30 0.2508 WVFGRD96 8.0 315 75 -10 5.30 0.2363 WVFGRD96 9.0 130 50 -10 5.28 0.2380 WVFGRD96 10.0 120 35 5 5.23 0.2528 WVFGRD96 11.0 120 35 5 5.24 0.2693 WVFGRD96 12.0 115 30 15 5.23 0.2863 WVFGRD96 13.0 110 30 15 5.24 0.3024 WVFGRD96 14.0 115 30 20 5.26 0.3173 WVFGRD96 15.0 115 30 20 5.27 0.3324 WVFGRD96 16.0 110 30 20 5.28 0.3457 WVFGRD96 17.0 60 50 40 5.43 0.3595 WVFGRD96 18.0 60 50 40 5.44 0.3749 WVFGRD96 19.0 60 50 40 5.45 0.3890 WVFGRD96 20.0 60 50 40 5.47 0.4026 WVFGRD96 21.0 60 50 40 5.49 0.4176 WVFGRD96 22.0 60 45 40 5.51 0.4301 WVFGRD96 23.0 60 45 40 5.52 0.4416 WVFGRD96 24.0 60 45 40 5.53 0.4529 WVFGRD96 25.0 60 45 40 5.54 0.4636 WVFGRD96 26.0 60 45 40 5.55 0.4735 WVFGRD96 27.0 10 50 -60 5.46 0.4931 WVFGRD96 28.0 10 50 -60 5.47 0.5126 WVFGRD96 29.0 15 50 -55 5.49 0.5307 WVFGRD96 30.0 15 50 -55 5.50 0.5477 WVFGRD96 31.0 15 50 -55 5.51 0.5623 WVFGRD96 32.0 10 45 -60 5.51 0.5757 WVFGRD96 33.0 10 45 -60 5.52 0.5877 WVFGRD96 34.0 10 45 -60 5.54 0.5974 WVFGRD96 35.0 370 45 -60 5.55 0.6048 WVFGRD96 36.0 370 45 -60 5.56 0.6115 WVFGRD96 37.0 355 40 -75 5.57 0.6186 WVFGRD96 38.0 355 40 -75 5.58 0.6261 WVFGRD96 39.0 350 40 -80 5.60 0.6339 WVFGRD96 40.0 160 50 -105 5.69 0.6181 WVFGRD96 41.0 160 50 -105 5.71 0.6302 WVFGRD96 42.0 345 45 -100 5.71 0.6379 WVFGRD96 43.0 345 45 -105 5.72 0.6434 WVFGRD96 44.0 165 50 -95 5.73 0.6469 WVFGRD96 45.0 165 50 -95 5.73 0.6483 WVFGRD96 46.0 355 40 -80 5.74 0.6475 WVFGRD96 47.0 165 50 -95 5.75 0.6464 WVFGRD96 48.0 350 40 -90 5.75 0.6434 WVFGRD96 49.0 165 50 -95 5.76 0.6397 WVFGRD96 50.0 350 40 -90 5.76 0.6342
The best solution is
WVFGRD96 45.0 165 50 -95 5.73 0.6483
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 0.01 n 3 lp c 0.06 n 3
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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:
DATE=Sat Dec 20 14:50:51 CST 2008