The ANSS event ID is aka2026jmrcur and the event page is at https://earthquake.usgs.gov/earthquakes/eventpage/aka2026jmrcur/executive.
2026/05/14 13:06:19 59.533 -152.581 93.5 4.0 Alaska
USGS/SLU Moment Tensor Solution
ENS 2026/05/14 13:06:19.0 59.53 -152.58 93.5 4.0 Alaska
Stations used:
AK.BRLK AK.CAPN AK.FIRE AK.N18K AK.O18K AK.O19K AK.Q19K
AK.RC01 AK.SLK AK.SSN AK.SWD II.KDAK
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 0.07 n 3
br c 0.12 0.25 n 4 p 2
Best Fitting Double Couple
Mo = 1.84e+22 dyne-cm
Mw = 4.11
Z = 106 km
Plane Strike Dip Rake
NP1 309 67 153
NP2 50 65 25
Principal Axes:
Axis Value Plunge Azimuth
T 1.84e+22 35 269
N 0.00e+00 55 92
P -1.84e+22 2 360
Moment Tensor: (dyne-cm)
Component Value
Mxx -1.84e+22
Mxy 3.09e+20
Mxz -7.01e+20
Myy 1.24e+22
Myz -8.62e+21
Mzz 5.96e+21
----- P ------
--------- ----------
----------------------------
------------------------------
#######--------------------------#
#############--------------------###
#################----------------#####
#####################-------------######
#######################----------#######
###########################-----##########
###### ####################--###########
###### T ####################-############
###### ##################-----##########
########################--------########
######################-----------#######
##################---------------#####
##############-------------------###
#########------------------------#
------------------------------
----------------------------
----------------------
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Global CMT Convention Moment Tensor:
R T P
5.96e+21 -7.01e+20 8.62e+21
-7.01e+20 -1.84e+22 -3.09e+20
8.62e+21 -3.09e+20 1.24e+22
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20260514130619/index.html
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STK = 50
DIP = 65
RAKE = 25
MW = 4.11
HS = 106.0
The NDK file is 20260514130619.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 0.07 n 3 br c 0.12 0.25 n 4 p 2The results of this grid search are as follow:
DEPTH STK DIP RAKE MW FIT
WVFGRD96 2.0 50 60 30 3.35 0.4075
WVFGRD96 4.0 60 60 50 3.45 0.4498
WVFGRD96 6.0 40 70 -5 3.38 0.4646
WVFGRD96 8.0 35 65 -30 3.46 0.4775
WVFGRD96 10.0 225 75 15 3.45 0.4868
WVFGRD96 12.0 225 75 15 3.48 0.4951
WVFGRD96 14.0 225 75 15 3.50 0.5002
WVFGRD96 16.0 225 75 15 3.53 0.5032
WVFGRD96 18.0 225 80 20 3.55 0.5043
WVFGRD96 20.0 225 80 20 3.57 0.5043
WVFGRD96 22.0 230 75 20 3.60 0.5031
WVFGRD96 24.0 230 75 20 3.62 0.5018
WVFGRD96 26.0 230 75 20 3.64 0.4997
WVFGRD96 28.0 225 75 15 3.65 0.4971
WVFGRD96 30.0 225 75 15 3.67 0.4937
WVFGRD96 32.0 225 75 15 3.69 0.4895
WVFGRD96 34.0 225 75 15 3.71 0.4846
WVFGRD96 36.0 225 80 15 3.72 0.4806
WVFGRD96 38.0 225 80 10 3.75 0.4797
WVFGRD96 40.0 230 70 20 3.80 0.4816
WVFGRD96 42.0 225 75 5 3.80 0.4828
WVFGRD96 44.0 225 75 0 3.82 0.4828
WVFGRD96 46.0 220 75 -15 3.85 0.4842
WVFGRD96 48.0 50 75 30 3.90 0.4869
WVFGRD96 50.0 50 75 35 3.93 0.4921
WVFGRD96 52.0 50 75 35 3.94 0.4991
WVFGRD96 54.0 50 75 35 3.96 0.5068
WVFGRD96 56.0 50 70 35 3.97 0.5151
WVFGRD96 58.0 50 70 35 3.99 0.5245
WVFGRD96 60.0 50 70 35 4.00 0.5378
WVFGRD96 62.0 50 70 35 4.01 0.5502
WVFGRD96 64.0 45 75 35 4.02 0.5624
WVFGRD96 66.0 45 75 35 4.03 0.5736
WVFGRD96 68.0 45 75 35 4.03 0.5835
WVFGRD96 70.0 45 75 35 4.04 0.5916
WVFGRD96 72.0 45 70 35 4.06 0.5997
WVFGRD96 74.0 45 70 35 4.06 0.6065
WVFGRD96 76.0 45 70 30 4.06 0.6132
WVFGRD96 78.0 45 70 30 4.06 0.6191
WVFGRD96 80.0 45 70 30 4.07 0.6240
WVFGRD96 82.0 50 65 35 4.09 0.6288
WVFGRD96 84.0 50 65 30 4.08 0.6340
WVFGRD96 86.0 50 65 30 4.09 0.6377
WVFGRD96 88.0 50 65 30 4.09 0.6415
WVFGRD96 90.0 50 65 30 4.09 0.6441
WVFGRD96 92.0 50 65 30 4.10 0.6468
WVFGRD96 94.0 50 65 30 4.10 0.6484
WVFGRD96 96.0 50 65 25 4.10 0.6500
WVFGRD96 98.0 50 65 25 4.10 0.6518
WVFGRD96 100.0 50 65 25 4.11 0.6526
WVFGRD96 102.0 50 65 25 4.11 0.6532
WVFGRD96 104.0 50 65 25 4.11 0.6536
WVFGRD96 106.0 50 65 25 4.11 0.6538
WVFGRD96 108.0 50 65 20 4.11 0.6534
WVFGRD96 110.0 50 65 20 4.12 0.6532
WVFGRD96 112.0 45 70 20 4.11 0.6529
WVFGRD96 114.0 45 70 20 4.11 0.6529
WVFGRD96 116.0 45 70 20 4.12 0.6527
WVFGRD96 118.0 45 70 20 4.12 0.6519
WVFGRD96 120.0 45 70 20 4.12 0.6514
WVFGRD96 122.0 45 70 15 4.12 0.6503
WVFGRD96 124.0 45 70 15 4.13 0.6492
WVFGRD96 126.0 45 70 15 4.13 0.6482
WVFGRD96 128.0 45 70 15 4.13 0.6471
The best solution is
WVFGRD96 106.0 50 65 25 4.11 0.6538
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 0.07 n 3 br c 0.12 0.25 n 4 p 2
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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