USGS/SLU Moment Tensor Solution ENS 2019/01/10 13:48:59:0 45.42 -66.25 5.0 3.8 New Brunswick, Canada Stations used: CN.GGN CN.HKNB CN.MCNB CN.SRNB N4.F64A N4.G65A Filtering commands used: cut o DIST/3.3 -10 o DIST/3.3 +30 rtr taper w 0.1 hp c 0.10 n 3 lp c 0.50 n 3 Best Fitting Double Couple Mo = 1.64e+21 dyne-cm Mw = 3.41 Z = 2 km Plane Strike Dip Rake NP1 171 47 105 NP2 330 45 75 Principal Axes: Axis Value Plunge Azimuth T 1.64e+21 79 155 N 0.00e+00 11 341 P -1.64e+21 1 251 Moment Tensor: (dyne-cm) Component Value Mxx -1.36e+20 Mxy -5.36e+20 Mxz -2.60e+20 Myy -1.45e+21 Myz 1.50e+20 Mzz 1.58e+21 ##------------ -----#---------------- ------#######--------------- ------###########------------- --------##############------------ --------################------------ ---------##################----------- ---------####################----------- ---------#####################---------- ----------######################---------- ----------#######################--------- ----------########### #########--------- -----------########## T ##########-------- --------########## ##########------- P ---------######################------- ---------######################------ ----------#####################----- ----------####################---- ---------##################--- ----------################-- ---------############# --------###### Global CMT Convention Moment Tensor: R T P 1.58e+21 -2.60e+20 -1.50e+20 -2.60e+20 -1.36e+20 5.36e+20 -1.50e+20 5.36e+20 -1.45e+21 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20190110134859/index.html |
STK = 330 DIP = 45 RAKE = 75 MW = 3.41 HS = 2.0
The NDK file is 20190110134859.ndk This is really pushing the process for small events. The Mw is very compatible with the ML(H) ML(Z) and the mLg. The mechanism was tweaked to fit the regional patterns of stress. The manual location shows that the few first motions are compatible with the solution as is the soruce depth.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution ENS 2019/01/10 13:48:59:0 45.42 -66.25 5.0 3.8 New Brunswick, Canada Stations used: CN.GGN CN.HKNB CN.MCNB CN.SRNB N4.F64A N4.G65A Filtering commands used: cut o DIST/3.3 -10 o DIST/3.3 +30 rtr taper w 0.1 hp c 0.10 n 3 lp c 0.50 n 3 Best Fitting Double Couple Mo = 1.64e+21 dyne-cm Mw = 3.41 Z = 2 km Plane Strike Dip Rake NP1 171 47 105 NP2 330 45 75 Principal Axes: Axis Value Plunge Azimuth T 1.64e+21 79 155 N 0.00e+00 11 341 P -1.64e+21 1 251 Moment Tensor: (dyne-cm) Component Value Mxx -1.36e+20 Mxy -5.36e+20 Mxz -2.60e+20 Myy -1.45e+21 Myz 1.50e+20 Mzz 1.58e+21 ##------------ -----#---------------- ------#######--------------- ------###########------------- --------##############------------ --------################------------ ---------##################----------- ---------####################----------- ---------#####################---------- ----------######################---------- ----------#######################--------- ----------########### #########--------- -----------########## T ##########-------- --------########## ##########------- P ---------######################------- ---------######################------ ----------#####################----- ----------####################---- ---------##################--- ----------################-- ---------############# --------###### Global CMT Convention Moment Tensor: R T P 1.58e+21 -2.60e+20 -1.50e+20 -2.60e+20 -1.36e+20 5.36e+20 -1.50e+20 5.36e+20 -1.45e+21 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20190110134859/index.html |
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(a) mLg computed using the IASPEI formula; (b) mLg residuals ; the values used for the trimmed mean are indicated.
(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.
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:
cut o DIST/3.3 -10 o DIST/3.3 +30 rtr taper w 0.1 hp c 0.10 n 3 lp c 0.50 n 3The results of this grid search from 0.5 to 19 km depth are as follow:
DEPTH STK DIP RAKE MW FIT WVFGRD96 1.0 35 20 -30 3.33 0.3753 WVFGRD96 2.0 330 45 75 3.41 0.4097 WVFGRD96 3.0 330 45 60 3.40 0.3779 WVFGRD96 4.0 20 60 -55 3.43 0.3293 WVFGRD96 5.0 245 65 75 3.54 0.2930 WVFGRD96 6.0 245 65 75 3.58 0.2696 WVFGRD96 7.0 245 65 65 3.59 0.2470 WVFGRD96 8.0 255 75 80 3.68 0.2377 WVFGRD96 9.0 265 75 80 3.70 0.2385 WVFGRD96 10.0 50 30 20 3.67 0.2426 WVFGRD96 11.0 55 30 25 3.71 0.2538 WVFGRD96 12.0 50 25 15 3.74 0.2606 WVFGRD96 13.0 55 25 25 3.77 0.2701 WVFGRD96 14.0 50 25 15 3.78 0.2757 WVFGRD96 15.0 50 25 15 3.79 0.2807 WVFGRD96 16.0 185 25 -65 3.78 0.2889 WVFGRD96 17.0 200 25 -40 3.79 0.2991 WVFGRD96 18.0 205 25 -30 3.79 0.3040 WVFGRD96 19.0 205 25 -25 3.80 0.3080 WVFGRD96 20.0 210 25 -10 3.83 0.3159 WVFGRD96 21.0 210 25 -15 3.83 0.3202 WVFGRD96 22.0 210 25 -15 3.83 0.3152 WVFGRD96 23.0 190 35 -50 3.81 0.3123 WVFGRD96 24.0 190 35 -50 3.82 0.3227 WVFGRD96 25.0 190 35 -50 3.82 0.3269 WVFGRD96 26.0 20 90 75 3.91 0.3225 WVFGRD96 27.0 20 90 75 3.91 0.3334 WVFGRD96 28.0 195 85 -75 3.88 0.3282 WVFGRD96 29.0 35 25 -30 3.82 0.3313
The best solution is
WVFGRD96 2.0 330 45 75 3.41 0.4097
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 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
cut o DIST/3.3 -10 o DIST/3.3 +30 rtr taper w 0.1 hp c 0.10 n 3 lp c 0.50 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. |
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:
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.
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.
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
Here we tabulate the reasons for not using certain digital data sets
The following stations did not have a valid response files: