2014/08/31 03:06:57 65.155 -148.983 15.5 5.1 Alaska
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution ENS 2014/08/31 03:06:57:0 65.15 -148.98 15.5 5.1 Alaska Stations used: AK.BAL AK.BARN AK.BPAW AK.BWN AK.CCB AK.COLD AK.CRQ AK.DOT AK.EYAK AK.FID AK.GHO AK.GLB AK.GLI AK.HDA AK.HIN AK.HMT IU.COLA US.EGAK Filtering commands used: cut o DIST/3.3 -40 o DIST/3.3 +60 rtr taper w 0.1 hp c 0.02 n 3 lp c 0.06 n 3 Best Fitting Double Couple Mo = 4.42e+23 dyne-cm Mw = 5.03 Z = 17 km Plane Strike Dip Rake NP1 299 76 -164 NP2 205 75 -15 Principal Axes: Axis Value Plunge Azimuth T 4.42e+23 0 72 N 0.00e+00 69 341 P -4.42e+23 21 162 Moment Tensor: (dyne-cm) Component Value Mxx -3.05e+23 Mxy 2.43e+23 Mxz 1.42e+23 Myy 3.63e+23 Myz -4.30e+22 Mzz -5.71e+22 -------------- ------------------#### -------------------######### -------------------########### --------------------############## -------------------################# #########----------################## ###############----################### T ##################-################### ##################------################## #################----------############### ################-------------############# ################----------------########## ##############-------------------####### #############----------------------##### ############------------------------## ##########-------------------------- #########------------------------- #######------------ -------- #####------------- P ------- ##------------- ---- -------------- Global CMT Convention Moment Tensor: R T P -5.71e+22 1.42e+23 4.30e+22 1.42e+23 -3.05e+23 -2.43e+23 4.30e+22 -2.43e+23 3.63e+23 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20140831030657/index.html |
STK = 205 DIP = 75 RAKE = -15 MW = 5.03 HS = 17.0
The NDK file is 20140831030657.ndk The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution ENS 2014/08/31 03:06:57:0 65.15 -148.98 15.5 5.1 Alaska Stations used: AK.BAL AK.BARN AK.BPAW AK.BWN AK.CCB AK.COLD AK.CRQ AK.DOT AK.EYAK AK.FID AK.GHO AK.GLB AK.GLI AK.HDA AK.HIN AK.HMT IU.COLA US.EGAK Filtering commands used: cut o DIST/3.3 -40 o DIST/3.3 +60 rtr taper w 0.1 hp c 0.02 n 3 lp c 0.06 n 3 Best Fitting Double Couple Mo = 4.42e+23 dyne-cm Mw = 5.03 Z = 17 km Plane Strike Dip Rake NP1 299 76 -164 NP2 205 75 -15 Principal Axes: Axis Value Plunge Azimuth T 4.42e+23 0 72 N 0.00e+00 69 341 P -4.42e+23 21 162 Moment Tensor: (dyne-cm) Component Value Mxx -3.05e+23 Mxy 2.43e+23 Mxz 1.42e+23 Myy 3.63e+23 Myz -4.30e+22 Mzz -5.71e+22 -------------- ------------------#### -------------------######### -------------------########### --------------------############## -------------------################# #########----------################## ###############----################### T ##################-################### ##################------################## #################----------############### ################-------------############# ################----------------########## ##############-------------------####### #############----------------------##### ############------------------------## ##########-------------------------- #########------------------------- #######------------ -------- #####------------- P ------- ##------------- ---- -------------- Global CMT Convention Moment Tensor: R T P -5.71e+22 1.42e+23 4.30e+22 1.42e+23 -3.05e+23 -2.43e+23 4.30e+22 -2.43e+23 3.63e+23 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20140831030657/index.html |
Regional Moment Tensor (Mwr) Moment 4.58e+16 N-m Magnitude 5.0 Percent DC 93% Depth 15.0 km Updated 2014-08-31 04:04:03 UTC Author us Catalog ak Contributor us Code us_c000s8cw_mwr Principal Axes Axis Value Plunge Azimuth T 4.657 3° 249° N -0.163 68° 347° P -4.494 22° 158° Nodal Planes Plane Strike Dip Rake NP1 202° 77° -18° NP2 296° 73° -166° |
(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 -40 o DIST/3.3 +60 rtr taper w 0.1 hp c 0.02 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 1.0 25 70 15 4.60 0.3528 WVFGRD96 2.0 25 75 15 4.71 0.4653 WVFGRD96 3.0 205 75 15 4.75 0.5013 WVFGRD96 4.0 200 75 -20 4.80 0.5249 WVFGRD96 5.0 200 75 -25 4.83 0.5651 WVFGRD96 6.0 200 75 -20 4.85 0.6048 WVFGRD96 7.0 205 80 -20 4.87 0.6421 WVFGRD96 8.0 200 75 -25 4.92 0.6772 WVFGRD96 9.0 200 70 -20 4.94 0.7053 WVFGRD96 10.0 200 70 -20 4.95 0.7285 WVFGRD96 11.0 200 75 -20 4.97 0.7471 WVFGRD96 12.0 200 75 -20 4.98 0.7620 WVFGRD96 13.0 200 75 -20 4.99 0.7727 WVFGRD96 14.0 200 75 -20 5.00 0.7802 WVFGRD96 15.0 200 75 -20 5.01 0.7851 WVFGRD96 16.0 200 75 -20 5.02 0.7876 WVFGRD96 17.0 205 75 -15 5.03 0.7890 WVFGRD96 18.0 205 75 -15 5.04 0.7887 WVFGRD96 19.0 205 75 -15 5.05 0.7869 WVFGRD96 20.0 205 75 -15 5.06 0.7843 WVFGRD96 21.0 205 75 -15 5.07 0.7802 WVFGRD96 22.0 205 75 -15 5.07 0.7750 WVFGRD96 23.0 205 75 -15 5.08 0.7686 WVFGRD96 24.0 205 75 -15 5.09 0.7615 WVFGRD96 25.0 205 75 -15 5.09 0.7546 WVFGRD96 26.0 205 75 -15 5.10 0.7467 WVFGRD96 27.0 205 75 -15 5.11 0.7380 WVFGRD96 28.0 205 75 -15 5.11 0.7288 WVFGRD96 29.0 205 75 -15 5.12 0.7194
The best solution is
WVFGRD96 17.0 205 75 -15 5.03 0.7890
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 -40 o DIST/3.3 +60 rtr taper w 0.1 hp c 0.02 n 3 lp c 0.06 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: