The ANSS event ID is hv74837442 and the event page is at https://earthquake.usgs.gov/earthquakes/eventpage/hv74837442/executive.
2025/11/26 09:49:45 19.336 -155.075 5.8 4.6 Hawaii
USGS/SLU Moment Tensor Solution
ENS 2025/11/26 09:49:45.0 19.34 -155.07 5.8 4.6 Hawaii
Stations used:
HV.CPKD HV.DEVL HV.HLPD HV.HOVE HV.KKUD HV.MITD HV.MLOD
HV.MOKD HV.NAGD HV.PAUD HV.PPLD HV.TOUO HV.UWE IU.POHA
PT.HILB PT.KHLU PT.KHU PT.MLOA
Filtering commands used:
cut o DIST/3.3 -40 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 = 9.66e+22 dyne-cm
Mw = 4.59
Z = 10 km
Plane Strike Dip Rake
NP1 258 54 127
NP2 25 50 50
Principal Axes:
Axis Value Plunge Azimuth
T 9.66e+22 60 228
N 0.00e+00 29 53
P -9.66e+22 2 322
Moment Tensor: (dyne-cm)
Component Value
Mxx -4.95e+22
Mxy 5.85e+22
Mxz -3.07e+22
Myy -2.34e+22
Myz -2.85e+22
Mzz 7.29e+22
--------------
---------------------#
P ---------------------####
- ----------------------####
-----------------------------#####
------------------------------######
---------------################--#####
-----------#####################------##
--------########################--------
------##########################----------
----############################----------
---############################-----------
--############ ##############-----------
############# T #############-----------
############# ############------------
##########################------------
#######################-------------
#####################-------------
#################-------------
##############--------------
#######---------------
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Global CMT Convention Moment Tensor:
R T P
7.29e+22 -3.07e+22 2.85e+22
-3.07e+22 -4.95e+22 -5.85e+22
2.85e+22 -5.85e+22 -2.34e+22
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20251126094945/index.html
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STK = 25
DIP = 50
RAKE = 50
MW = 4.59
HS = 10.0
The NDK file is 20251126094945.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 -40 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 are as follow:
DEPTH STK DIP RAKE MW FIT
WVFGRD96 1.0 50 90 20 4.09 0.2069
WVFGRD96 2.0 160 70 -40 4.27 0.2841
WVFGRD96 3.0 165 70 -55 4.34 0.3401
WVFGRD96 4.0 165 65 -55 4.38 0.4039
WVFGRD96 5.0 215 35 60 4.45 0.4584
WVFGRD96 6.0 215 35 60 4.47 0.5077
WVFGRD96 7.0 25 45 50 4.50 0.5399
WVFGRD96 8.0 215 35 60 4.57 0.5509
WVFGRD96 9.0 30 45 55 4.59 0.5697
WVFGRD96 10.0 25 50 50 4.59 0.5710
WVFGRD96 11.0 25 50 50 4.61 0.5630
WVFGRD96 12.0 20 55 40 4.61 0.5478
WVFGRD96 13.0 20 55 40 4.62 0.5310
WVFGRD96 14.0 15 60 35 4.62 0.5106
WVFGRD96 15.0 15 60 35 4.63 0.4915
WVFGRD96 16.0 15 65 30 4.64 0.4725
WVFGRD96 17.0 15 65 30 4.65 0.4535
WVFGRD96 18.0 180 60 -20 4.60 0.4355
WVFGRD96 19.0 180 65 -25 4.60 0.4274
WVFGRD96 20.0 180 65 -25 4.61 0.4222
WVFGRD96 21.0 180 65 -25 4.62 0.4160
WVFGRD96 22.0 180 60 -30 4.63 0.4125
WVFGRD96 23.0 180 60 -30 4.63 0.4088
WVFGRD96 24.0 180 60 -30 4.64 0.4047
WVFGRD96 25.0 180 60 -30 4.64 0.4011
WVFGRD96 26.0 180 60 -30 4.65 0.3966
WVFGRD96 27.0 180 60 -35 4.65 0.3924
WVFGRD96 28.0 175 55 -35 4.66 0.3894
WVFGRD96 29.0 175 55 -35 4.66 0.3854
The best solution is
WVFGRD96 10.0 25 50 50 4.59 0.5710
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 -40 o DIST/3.3 +50 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 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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|
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The program wvfmtgrd96 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 -20 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 over depth are as follow:
MT Program H(km) Mxx(dyne-cm) Myy Mxy Mxz Myz Mzz Mw Fit WVFMTGRD96 1.0 0.284E+23 0.216E+23 0.988E+22 0.865E+21 -0.514E+22 0.146E+23 4.2458 0.2964 WVFMTGRD96 2.0 0.430E+23 0.322E+23 0.186E+23 0.150E+22 -0.103E+23 0.462E+23 4.4240 0.3579 WVFMTGRD96 3.0 0.455E+23 0.341E+23 0.233E+23 0.144E+22 -0.152E+23 0.636E+23 4.4816 0.4221 WVFMTGRD96 4.0 0.380E+23 0.308E+23 0.287E+23 -0.927E+22 -0.147E+23 0.714E+23 4.4959 0.4758 WVFMTGRD96 5.0 0.231E+23 0.229E+23 0.334E+23 -0.161E+23 -0.156E+23 0.719E+23 4.4916 0.5173 WVFMTGRD96 6.0 0.164E+23 0.162E+23 0.380E+23 -0.174E+23 -0.168E+23 0.712E+23 4.4945 0.5472 WVFMTGRD96 7.0 0.840E+22 0.154E+23 0.449E+23 -0.207E+23 -0.178E+23 0.685E+23 4.5069 0.5669 WVFMTGRD96 8.0 0.295E+22 0.747E+22 0.509E+23 -0.281E+23 -0.219E+23 0.981E+23 4.5798 0.5797 WVFMTGRD96 9.0 -0.208E+23 0.343E+22 0.545E+23 -0.286E+23 -0.266E+23 0.931E+23 4.5856 0.5844 WVFMTGRD96 10.0 -0.376E+23 -0.109E+23 0.595E+23 -0.298E+23 -0.273E+23 0.843E+23 4.5926 0.5815 WVFMTGRD96 11.0 -0.491E+23 -0.208E+23 0.630E+23 -0.316E+23 -0.289E+23 0.799E+23 4.6060 0.5718 WVFMTGRD96 12.0 -0.644E+23 -0.333E+23 0.685E+23 -0.311E+23 -0.276E+23 0.702E+23 4.6204 0.5569 WVFMTGRD96 13.0 -0.513E+23 -0.163E+23 0.768E+23 -0.371E+23 -0.367E+23 0.570E+23 4.6228 0.5385 WVFMTGRD96 14.0 -0.608E+23 -0.244E+23 0.799E+23 -0.386E+23 -0.382E+23 0.519E+23 4.6362 0.5191 WVFMTGRD96 15.0 -0.486E+23 -0.169E+23 0.838E+23 -0.348E+23 -0.415E+23 0.518E+23 4.6336 0.4985 WVFMTGRD96 16.0 -0.448E+23 -0.123E+22 0.897E+23 -0.397E+23 -0.457E+23 0.403E+23 4.6438 0.4789 WVFMTGRD96 17.0 -0.457E+22 0.290E+23 0.746E+23 0.427E+23 -0.353E+23 0.106E+23 4.5868 0.4594 WVFMTGRD96 18.0 -0.651E+22 0.283E+23 0.772E+23 0.428E+23 -0.354E+23 0.685E+22 4.5926 0.4490 WVFMTGRD96 19.0 -0.645E+22 0.440E+23 0.751E+23 0.459E+23 -0.367E+23 -0.646E+21 4.6012 0.4395 WVFMTGRD96 20.0 0.500E+22 0.384E+23 0.758E+23 0.569E+23 -0.307E+23 -0.536E+22 4.6097 0.4325 WVFMTGRD96 21.0 0.160E+23 0.551E+23 0.767E+23 0.573E+23 -0.326E+23 -0.956E+22 4.6256 0.4263 WVFMTGRD96 22.0 0.363E+21 0.403E+23 0.790E+23 0.572E+23 -0.320E+23 -0.274E+23 4.6230 0.4219 WVFMTGRD96 23.0 0.955E+22 0.503E+23 0.808E+23 0.585E+23 -0.327E+23 -0.188E+23 4.6324 0.4173 WVFMTGRD96 24.0 0.165E+23 0.631E+23 0.777E+23 0.585E+23 -0.368E+23 -0.233E+23 4.6404 0.4129 WVFMTGRD96 25.0 0.168E+23 0.643E+23 0.792E+23 0.597E+23 -0.375E+23 -0.237E+23 4.6459 0.4097 WVFMTGRD96 26.0 0.171E+23 0.654E+23 0.806E+23 0.607E+23 -0.381E+23 -0.241E+23 4.6507 0.4052 WVFMTGRD96 27.0 0.255E+23 0.742E+23 0.808E+23 0.631E+23 -0.400E+23 -0.149E+23 4.6616 0.4012 WVFMTGRD96 28.0 0.446E+23 0.786E+23 0.796E+23 0.679E+23 -0.358E+23 -0.208E+23 4.6728 0.3974 WVFMTGRD96 29.0 0.430E+23 0.944E+23 0.817E+23 0.587E+23 -0.351E+23 -0.328E+23 4.6791 0.3933
The best solution is
WVFMTGRD96 9.0 -0.208E+23 0.343E+22 0.545E+23 -0.286E+23 -0.266E+23 0.931E+23 4.5856 0.5844
The complete moment tensor decomposition using the program mtinfo is given in the text file MTGRDinfo.txt. (Jost, M. L., and R. B. Herrmann (1989). A student's guide to and review of moment tensors, Seism. Res. Letters 60, 37-57. SRL_60_2_37-57.pdf.
The P-wave first motion 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 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 -20 o DIST/3.3 +50 rtr taper w 0.1 hp c 0.03 n 3 lp c 0.10 n 3
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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