USGS/SLU Moment Tensor Solution ENS 2018/12/01 07:07:38:0 61.51 -149.94 43.5 5.1 Alaska Stations used: AK.BERG AK.BPAW AK.BRLK AK.CAST AK.CNP AK.CUT AK.DHY AK.DIV AK.EYAK AK.FID AK.GHO AK.GLI AK.HDA AK.HOM AK.KLU AK.KNK AK.KTH AK.PPLA AK.PWL AK.RC01 AK.SAW AK.SCM AK.SKN AK.SLK AK.SSN AK.SWD AK.TRF AK.VRDI AK.WRH AT.SVW2 AV.ILSW AV.STLK TA.L18K TA.M19K TA.M20K TA.M22K TA.M24K TA.N18K TA.N19K TA.O18K TA.O19K TA.O22K TA.P18K TA.P19K Filtering commands used: cut o DIST/3.3 -30 o DIST/3.3 +50 rtr taper w 0.1 hp c 0.03 n 3 lp c 0.10 n 3 Best Fitting Double Couple Mo = 2.29e+23 dyne-cm Mw = 4.84 Z = 50 km Plane Strike Dip Rake NP1 210 80 -55 NP2 314 36 -163 Principal Axes: Axis Value Plunge Azimuth T 2.29e+23 27 273 N 0.00e+00 34 23 P -2.29e+23 44 154 Moment Tensor: (dyne-cm) Component Value Mxx -9.60e+22 Mxy 3.69e+22 Mxz 1.08e+23 Myy 1.60e+23 Myz -1.41e+23 Mzz -6.42e+22 -------------- ---------------------# ---#########----------###### ##################---######### ######################-########### ######################-----######### #####################--------######### #####################-----------######## ####################-------------####### #### #############---------------####### #### T ############-----------------###### #### ###########-------------------##### #################--------------------##### ###############---------------------#### ##############-----------------------### ############----------- ---------### ##########------------ P ---------## ########------------- ---------# ######------------------------ ####------------------------ #--------------------- -------------- Global CMT Convention Moment Tensor: R T P -6.42e+22 1.08e+23 1.41e+23 1.08e+23 -9.60e+22 -3.69e+22 1.41e+23 -3.69e+22 1.60e+23 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20181201070738/index.html |
STK = 210 DIP = 80 RAKE = -55 MW = 4.84 HS = 50.0
The NDK file is 20181201070738.ndk The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution ENS 2018/12/01 07:07:28:0 61.40 -150.07 22.8 4.5 Alaska Stations used: AK.BERG AK.BPAW AK.BRLK AK.CAST AK.CNP AK.CUT AK.DHY AK.DIV AK.EYAK AK.FID AK.GHO AK.GLI AK.HDA AK.HOM AK.KLU AK.KNK AK.KTH AK.PPLA AK.PWL AK.RC01 AK.SAW AK.SCM AK.SKN AK.SLK AK.SSN AK.SWD AK.TRF AK.VRDI AK.WRH AT.SVW2 AV.ILSW AV.STLK TA.L18K TA.M19K TA.M20K TA.M22K TA.M24K TA.N18K TA.N19K TA.O18K TA.O19K TA.O22K TA.P18K TA.P19K Filtering commands used: cut o DIST/3.3 -30 o DIST/3.3 +50 rtr taper w 0.1 hp c 0.03 n 3 lp c 0.10 n 3 Best Fitting Double Couple Mo = 2.29e+23 dyne-cm Mw = 4.84 Z = 50 km Plane Strike Dip Rake NP1 210 80 -55 NP2 314 36 -163 Principal Axes: Axis Value Plunge Azimuth T 2.29e+23 27 273 N 0.00e+00 34 23 P -2.29e+23 44 154 Moment Tensor: (dyne-cm) Component Value Mxx -9.60e+22 Mxy 3.69e+22 Mxz 1.08e+23 Myy 1.60e+23 Myz -1.41e+23 Mzz -6.42e+22 -------------- ---------------------# ---#########----------###### ##################---######### ######################-########### ######################-----######### #####################--------######### #####################-----------######## ####################-------------####### #### #############---------------####### #### T ############-----------------###### #### ###########-------------------##### #################--------------------##### ###############---------------------#### ##############-----------------------### ############----------- ---------### ##########------------ P ---------## ########------------- ---------# ######------------------------ ####------------------------ #--------------------- -------------- Global CMT Convention Moment Tensor: R T P -6.42e+22 1.08e+23 1.41e+23 1.08e+23 -9.60e+22 -3.69e+22 1.41e+23 -3.69e+22 1.60e+23 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20181201070728/index.html USGS/SLU Moment Tensor Solution ENS 2018/12/01 07:07:38:0 61.51 -149.94 43.5 5.1 Alaska Stations used: AK.BERG AK.BPAW AK.BRLK AK.CAST AK.CNP AK.CUT AK.DHY AK.DIV AK.EYAK AK.FID AK.GHO AK.GLI AK.HDA AK.HOM AK.KLU AK.KNK AK.KTH AK.PPLA AK.PWL AK.RC01 AK.SAW AK.SCM AK.SKN AK.SLK AK.SSN AK.SWD AK.TRF AK.VRDI AK.WRH AT.SVW2 AV.ILSW AV.STLK TA.L18K TA.M19K TA.M20K TA.M22K TA.M24K TA.N18K TA.N19K TA.O18K TA.O19K TA.O22K TA.P18K TA.P19K Filtering commands used: cut o DIST/3.3 -30 o DIST/3.3 +50 rtr taper w 0.1 hp c 0.03 n 3 lp c 0.10 n 3 Best Fitting Double Couple Mo = 2.29e+23 dyne-cm Mw = 4.84 Z = 50 km Plane Strike Dip Rake NP1 210 80 -55 NP2 314 36 -163 Principal Axes: Axis Value Plunge Azimuth T 2.29e+23 27 273 N 0.00e+00 34 23 P -2.29e+23 44 154 Moment Tensor: (dyne-cm) Component Value Mxx -9.60e+22 Mxy 3.69e+22 Mxz 1.08e+23 Myy 1.60e+23 Myz -1.41e+23 Mzz -6.42e+22 -------------- ---------------------# ---#########----------###### ##################---######### ######################-########### ######################-----######### #####################--------######### #####################-----------######## ####################-------------####### #### #############---------------####### #### T ############-----------------###### #### ###########-------------------##### #################--------------------##### ###############---------------------#### ##############-----------------------### ############----------- ---------### ##########------------ P ---------## ########------------- ---------# ######------------------------ ####------------------------ #--------------------- -------------- Global CMT Convention Moment Tensor: R T P -6.42e+22 1.08e+23 1.41e+23 1.08e+23 -9.60e+22 -3.69e+22 1.41e+23 -3.69e+22 1.60e+23 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20181201070738/index.html |
(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.
|
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 -30 o DIST/3.3 +50 rtr taper w 0.1 hp c 0.03 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 1.0 320 75 25 3.88 0.1850 WVFGRD96 2.0 330 60 45 4.06 0.2355 WVFGRD96 3.0 305 50 0 4.09 0.2353 WVFGRD96 4.0 305 55 -15 4.12 0.2477 WVFGRD96 5.0 305 55 -15 4.15 0.2588 WVFGRD96 6.0 300 50 -10 4.17 0.2705 WVFGRD96 7.0 305 60 -25 4.20 0.2829 WVFGRD96 8.0 300 50 -15 4.25 0.2888 WVFGRD96 9.0 300 45 -5 4.26 0.2936 WVFGRD96 10.0 305 45 5 4.27 0.2979 WVFGRD96 11.0 305 45 5 4.29 0.3007 WVFGRD96 12.0 305 45 5 4.30 0.3022 WVFGRD96 13.0 305 45 10 4.32 0.3022 WVFGRD96 14.0 305 45 10 4.33 0.3013 WVFGRD96 15.0 305 45 10 4.34 0.2990 WVFGRD96 16.0 305 45 10 4.35 0.2952 WVFGRD96 17.0 305 45 10 4.36 0.2904 WVFGRD96 18.0 305 45 10 4.37 0.2843 WVFGRD96 19.0 305 45 10 4.38 0.2777 WVFGRD96 20.0 305 45 10 4.39 0.2706 WVFGRD96 21.0 245 50 30 4.42 0.2664 WVFGRD96 22.0 245 50 30 4.43 0.2679 WVFGRD96 23.0 245 50 30 4.44 0.2695 WVFGRD96 24.0 240 50 25 4.46 0.2715 WVFGRD96 25.0 215 50 -45 4.46 0.2747 WVFGRD96 26.0 220 55 -35 4.47 0.2783 WVFGRD96 27.0 35 90 40 4.48 0.2871 WVFGRD96 28.0 30 90 45 4.49 0.3011 WVFGRD96 29.0 210 85 -45 4.51 0.3195 WVFGRD96 30.0 30 90 45 4.52 0.3366 WVFGRD96 31.0 30 90 45 4.54 0.3532 WVFGRD96 32.0 30 90 50 4.55 0.3684 WVFGRD96 33.0 205 80 -55 4.56 0.3894 WVFGRD96 34.0 205 80 -55 4.57 0.4044 WVFGRD96 35.0 205 80 -55 4.58 0.4168 WVFGRD96 36.0 205 80 -55 4.59 0.4304 WVFGRD96 37.0 205 80 -55 4.60 0.4499 WVFGRD96 38.0 205 80 -55 4.61 0.4686 WVFGRD96 39.0 205 80 -50 4.62 0.4876 WVFGRD96 40.0 205 80 -65 4.74 0.5085 WVFGRD96 41.0 205 80 -60 4.75 0.5355 WVFGRD96 42.0 205 80 -60 4.77 0.5605 WVFGRD96 43.0 205 80 -60 4.78 0.5851 WVFGRD96 44.0 205 80 -60 4.79 0.6070 WVFGRD96 45.0 205 80 -55 4.80 0.6263 WVFGRD96 46.0 210 80 -55 4.81 0.6419 WVFGRD96 47.0 210 80 -55 4.82 0.6538 WVFGRD96 48.0 210 80 -55 4.82 0.6615 WVFGRD96 49.0 210 80 -55 4.83 0.6643 WVFGRD96 50.0 210 80 -55 4.84 0.6643 WVFGRD96 51.0 205 75 -55 4.84 0.6629 WVFGRD96 52.0 205 75 -55 4.84 0.6624 WVFGRD96 53.0 205 75 -60 4.85 0.6605 WVFGRD96 54.0 205 75 -60 4.85 0.6589 WVFGRD96 55.0 205 75 -60 4.86 0.6560 WVFGRD96 56.0 205 75 -60 4.86 0.6519 WVFGRD96 57.0 205 75 -60 4.86 0.6499 WVFGRD96 58.0 205 75 -60 4.87 0.6452 WVFGRD96 59.0 205 75 -60 4.87 0.6401
The best solution is
WVFGRD96 50.0 210 80 -55 4.84 0.6643
The mechanism correspond to the best fit is
|
The best fit as a function of depth is given in the following figure:
|
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 -30 o DIST/3.3 +50 rtr taper w 0.1 hp c 0.03 n 3 lp c 0.10 n 3
|
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 WUS.model 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: