The ANSS event ID is hv71228166 and the event page is at https://earthquake.usgs.gov/earthquakes/eventpage/hv71228166/executive.
2019/11/11 16:35:52 19.864 -155.356 32.6 4.93 Hawaii
USGS/SLU Moment Tensor Solution
ENS 2019/11/11 16:35:52:0 19.86 -155.36 32.6 4.9 Hawaii
Stations used:
HV.BYL HV.DEVL HV.HAT HV.HLPD HV.HOVE HV.HUAD HV.MOKD
HV.STCD HV.UWE IU.POHA PT.HILB PT.HPAH
Filtering commands used:
cut o DIST/3.3 -30 o DIST/3.3 +40
rtr
taper w 0.1
hp c 0.03 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 9.02e+22 dyne-cm
Mw = 4.57
Z = 31 km
Plane Strike Dip Rake
NP1 285 70 80
NP2 132 22 116
Principal Axes:
Axis Value Plunge Azimuth
T 9.02e+22 64 179
N 0.00e+00 9 288
P -9.02e+22 24 23
Moment Tensor: (dyne-cm)
Component Value
Mxx -4.59e+22
Mxy -2.70e+22
Mxz -6.71e+22
Myy -1.12e+22
Myz -1.24e+22
Mzz 5.71e+22
--------------
----------------------
------------------- ------
-------------------- P -------
#--------------------- ---------
#-----------------------------------
#-------------------------------------
##--#########---------------------------
--####################------------------
---##########################-------------
---##############################---------
---#################################------
----##################################----
----############### #################-
-----############## T ##################
-----############# #################
-----###############################
------############################
------########################
--------##################--
-----------#######----
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Global CMT Convention Moment Tensor:
R T P
5.71e+22 -6.71e+22 1.24e+22
-6.71e+22 -4.59e+22 2.70e+22
1.24e+22 2.70e+22 -1.12e+22
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20191111163552/index.html
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STK = 285
DIP = 70
RAKE = 80
MW = 4.57
HS = 31.0
The NDK file is 20191111163552.ndk The waveform inversion is preferred.
Given the availability of digital waveforms for determination of the moment tensor, this section documents the added processing leading to mLg, if appropriate to the region, and ML by application of the respective IASPEI formulae. As a research study, the linear distance term of the IASPEI formula for ML is adjusted to remove a linear distance trend in residuals to give a regionally defined ML. The defined ML uses horizontal component recordings, but the same procedure is applied to the vertical components since there may be some interest in vertical component ground motions. Residual plots versus distance may indicate interesting features of ground motion scaling in some distance ranges. A residual plot of the regionalized magnitude is given as a function of distance and azimuth, since data sets may transcend different wave propagation provinces.
Left: ML computed using the IASPEI formula for Horizontal components. Center: 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.
Right: Residuals from new relation as a function of distance and azimuth.
Left: ML computed using the IASPEI formula for Vertical components (research). Center: 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.
Right: Residuals from new relation as a function of distance and azimuth.
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The focal mechanism was determined using broadband seismic waveforms. The location of the event (star) and the stations used for (red) 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's 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 +40 rtr taper w 0.1 hp c 0.03 n 3 lp c 0.10 n 3The results of this grid search are as follow:
DEPTH STK DIP RAKE MW FIT
WVFGRD96 1.0 35 90 -30 3.91 0.1440
WVFGRD96 2.0 175 35 -95 4.13 0.2024
WVFGRD96 3.0 170 45 65 4.14 0.1993
WVFGRD96 4.0 220 60 -20 4.13 0.2035
WVFGRD96 5.0 135 70 -35 4.13 0.2117
WVFGRD96 6.0 140 70 -35 4.15 0.2269
WVFGRD96 7.0 140 70 -30 4.18 0.2397
WVFGRD96 8.0 40 50 -25 4.27 0.2541
WVFGRD96 9.0 40 50 -30 4.29 0.2662
WVFGRD96 10.0 40 55 -25 4.32 0.2746
WVFGRD96 11.0 240 60 30 4.32 0.2823
WVFGRD96 12.0 240 60 30 4.34 0.2933
WVFGRD96 13.0 240 60 30 4.36 0.3024
WVFGRD96 14.0 240 60 30 4.37 0.3099
WVFGRD96 15.0 235 65 25 4.39 0.3167
WVFGRD96 16.0 235 65 25 4.40 0.3225
WVFGRD96 17.0 340 50 55 4.47 0.3283
WVFGRD96 18.0 340 50 50 4.48 0.3321
WVFGRD96 19.0 285 60 60 4.43 0.3400
WVFGRD96 20.0 285 65 60 4.44 0.3456
WVFGRD96 21.0 285 65 60 4.46 0.3516
WVFGRD96 22.0 285 65 65 4.47 0.3584
WVFGRD96 23.0 285 65 65 4.48 0.3634
WVFGRD96 24.0 285 65 70 4.49 0.3668
WVFGRD96 25.0 285 65 65 4.50 0.3693
WVFGRD96 26.0 285 65 70 4.51 0.3751
WVFGRD96 27.0 285 65 70 4.52 0.3804
WVFGRD96 28.0 285 65 75 4.54 0.3846
WVFGRD96 29.0 285 70 75 4.55 0.3885
WVFGRD96 30.0 285 70 80 4.56 0.3929
WVFGRD96 31.0 285 70 80 4.57 0.3953
WVFGRD96 32.0 285 70 80 4.58 0.3952
WVFGRD96 33.0 285 70 85 4.59 0.3922
WVFGRD96 34.0 285 70 85 4.59 0.3873
WVFGRD96 35.0 285 70 85 4.59 0.3805
WVFGRD96 36.0 285 75 85 4.59 0.3753
WVFGRD96 37.0 285 75 85 4.59 0.3693
WVFGRD96 38.0 285 75 85 4.59 0.3633
WVFGRD96 39.0 285 75 85 4.59 0.3579
WVFGRD96 40.0 280 80 85 4.72 0.3495
WVFGRD96 41.0 285 75 90 4.73 0.3473
WVFGRD96 42.0 280 75 85 4.72 0.3454
WVFGRD96 43.0 280 75 85 4.73 0.3424
WVFGRD96 44.0 280 75 85 4.73 0.3386
WVFGRD96 45.0 280 75 85 4.74 0.3349
WVFGRD96 46.0 280 80 85 4.74 0.3316
WVFGRD96 47.0 280 80 85 4.74 0.3277
WVFGRD96 48.0 280 80 85 4.75 0.3231
WVFGRD96 49.0 280 80 85 4.75 0.3197
WVFGRD96 50.0 280 80 85 4.75 0.3157
WVFGRD96 51.0 280 80 85 4.75 0.3112
WVFGRD96 52.0 35 55 -30 4.75 0.3107
WVFGRD96 53.0 35 55 -35 4.74 0.3105
WVFGRD96 54.0 30 50 -35 4.76 0.3090
WVFGRD96 55.0 35 55 -35 4.75 0.3084
WVFGRD96 56.0 35 55 -35 4.76 0.3073
WVFGRD96 57.0 30 50 -35 4.77 0.3069
WVFGRD96 58.0 45 60 -55 4.73 0.3074
WVFGRD96 59.0 45 60 -55 4.73 0.3070
The best solution is
WVFGRD96 31.0 285 70 80 4.57 0.3953
The mechanism corresponding 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, the velocity model used in the predictions may not be perfect and the epicentral parameters may be be off. 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 +40 rtr taper w 0.1 hp c 0.03 n 3 lp c 0.10 n 3
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| Figure 3. Waveform comparison for selected depth. Red: observed; Blue - predicted. The time shift with respect to the model prediction is indicated. The percent of fit is also indicated. The time scale is relative to the first trace sample. |
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| Focal mechanism sensitivity at the preferred depth. The red color indicates a very good fit to the waveforms. 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.
The WUS.model used for the waveform synthetic seismograms and for the surface wave eigenfunctions and dispersion is as follows (The format is in the model96 format of Computer Programs in Seismology).
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