2004/07/12 16:45:00 44.3290 -124.4900 29.0 4.90 Oregon
USGS Felt map for this earthquake
USGS Felt reports page for Pacific Northwest
SLU Moment Tensor Solution 2004/07/12 16:45:00 44.3290 -124.4900 29.0 4.90 Oregon Best Fitting Double Couple Mo = 1.27e+23 dyne-cm Mw = 4.67 Z = 15 km Plane Strike Dip Rake NP1 186 71 97 NP2 345 20 70 Principal Axes: Axis Value Plunge Azimuth T 1.27e+23 63 107 N 0.00e+00 7 4 P -1.27e+23 26 271 Moment Tensor: (dyne-cm) Component Value Mxx 2.30e+21 Mxy -6.33e+21 Mxz -1.58e+22 Myy -7.92e+22 Myz 9.91e+22 Mzz 7.69e+22 -------------- -----------######----- -------------##########----- -------------#############---- ---------------##############----- ---------------#################---- ----------------##################---- ----------------####################---- ----------------####################---- ---- ----------#####################---- ---- P ---------######################---- ---- ---------########## #########---- ----------------########## T #########---- ---------------########## #########--- ---------------#####################---- --------------#####################--- -------------####################--- ------------###################--- -----------#################-- ----------###############--- -------#############-- ----########## Harvard Convention Moment Tensor: R T F 7.69e+22 -1.58e+22 -9.91e+22 -1.58e+22 2.30e+21 6.33e+21 -9.91e+22 6.33e+21 -7.92e+22 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20040712164500/index.html |
STK = 345 DIP = 20 RAKE = 70 MW = 4.67 HS = 15.0
The waveform inversion is preferred.
The following compares this source inversion to others
SLU Moment Tensor Solution 2004/07/12 16:45:00 44.3290 -124.4900 29.0 4.90 Oregon Best Fitting Double Couple Mo = 1.27e+23 dyne-cm Mw = 4.67 Z = 15 km Plane Strike Dip Rake NP1 186 71 97 NP2 345 20 70 Principal Axes: Axis Value Plunge Azimuth T 1.27e+23 63 107 N 0.00e+00 7 4 P -1.27e+23 26 271 Moment Tensor: (dyne-cm) Component Value Mxx 2.30e+21 Mxy -6.33e+21 Mxz -1.58e+22 Myy -7.92e+22 Myz 9.91e+22 Mzz 7.69e+22 -------------- -----------######----- -------------##########----- -------------#############---- ---------------##############----- ---------------#################---- ----------------##################---- ----------------####################---- ----------------####################---- ---- ----------#####################---- ---- P ---------######################---- ---- ---------########## #########---- ----------------########## T #########---- ---------------########## #########--- ---------------#####################---- --------------#####################--- -------------####################--- ------------###################--- -----------#################-- ----------###############--- -------#############-- ----########## Harvard Convention Moment Tensor: R T F 7.69e+22 -1.58e+22 -9.91e+22 -1.58e+22 2.30e+21 6.33e+21 -9.91e+22 6.33e+21 -7.92e+22 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20040712164500/index.html |
071204B NEAR COAST OF OREGON Date: 2004/ 7/12 Centroid Time: 16:45: 3.7 GMT Lat= 44.30 Lon=-124.71 Depth= 20.0 Half duration= 0.7 Centroid time minus hypocenter time: 3.0 Moment Tensor: Expo=23 1.960 0.051 -2.010 0.254 -1.650 -0.397 Mw = 4.9 mb = 4.9 Ms = 4.1 Scalar Moment = 2.62e+23 Fault plane: strike=23 dip=27 slip=112 Fault plane: strike=178 dip=65 slip=79 -----######### --------#############- ----------################-- -----------#################-- ------------###################--- -------------####################--- -------------#####################---- --------------######################---- -- ---------########### ########---- --- P ---------########### T ########----- --- ---------########### ########----- ---------------######################----- ---------------#####################------ --------------#####################----- --------------####################------ --------------##################------ -------------#################------ -------------##############------- -----------#############------ -----------#########-------- ---------#####-------- ######-------- |
ofor04194 0 07/12/2004 16:45:00.0 44.332 -124.520 4.9 29.1 7121645 2 191 58 100 353 34 74 8 0.0 2.15e23 4.8 3 -2 0.02 0.05 OT01 OT04 OT06 OT08 HUMO YBH (uw7121645) STK 191 DIP 59 RAKE 100 Mo=2.15E+23 dyne-cm Mw=4.8 H=8 --------#----- -----------#####------ -------------########------- ------------############------ -------------##############------- -------------################------- -------------##################------- --------------###################------- -------------####################------- - ----------#####################------- - P ---------######################------- - ---------########## #########------- -------------########## T #########------- ------------########## #########------ ------------######################------ -----------#####################------ ----------#####################----- ---------####################----- --------##################---- -------################----- -----#############---- --##########-- |
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 3The results of this grid search from 0.5 to 19 km depth are as follow:
DEPTH STK DIP RAKE MW FIT WVFGRD96 0.5 205 45 -85 4.20 0.2137 WVFGRD96 1.0 205 45 -85 4.25 0.2051 WVFGRD96 2.0 205 45 -85 4.38 0.2428 WVFGRD96 3.0 225 20 -60 4.41 0.1521 WVFGRD96 4.0 255 10 -30 4.41 0.2057 WVFGRD96 5.0 270 10 -15 4.42 0.2631 WVFGRD96 6.0 280 10 0 4.43 0.3137 WVFGRD96 7.0 295 10 15 4.44 0.3539 WVFGRD96 8.0 305 10 25 4.54 0.3837 WVFGRD96 9.0 325 15 45 4.56 0.4206 WVFGRD96 10.0 340 20 60 4.59 0.4543 WVFGRD96 11.0 345 20 65 4.61 0.4854 WVFGRD96 12.0 350 20 75 4.63 0.5079 WVFGRD96 13.0 350 25 70 4.65 0.5242 WVFGRD96 14.0 350 20 75 4.66 0.5322 WVFGRD96 15.0 345 20 70 4.67 0.5344 WVFGRD96 16.0 345 20 65 4.68 0.5328 WVFGRD96 17.0 345 20 65 4.69 0.5261 WVFGRD96 18.0 340 15 60 4.69 0.5162 WVFGRD96 19.0 340 15 60 4.71 0.5062 WVFGRD96 20.0 340 15 60 4.72 0.4943 WVFGRD96 21.0 335 15 55 4.74 0.4818 WVFGRD96 22.0 325 15 45 4.75 0.4670 WVFGRD96 23.0 335 10 55 4.75 0.4525 WVFGRD96 24.0 330 10 50 4.76 0.4371 WVFGRD96 25.0 330 10 50 4.77 0.4203 WVFGRD96 26.0 330 10 50 4.78 0.4021 WVFGRD96 27.0 330 10 50 4.79 0.3824 WVFGRD96 28.0 325 10 45 4.79 0.3608 WVFGRD96 29.0 325 10 45 4.80 0.3374
The best solution is
WVFGRD96 15.0 345 20 70 4.67 0.5344
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
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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=Thu Dec 18 13:00:00 CST 2008