2016/09/11 13:10:07 41.98 21.50 5 5.2 FYR Macedonia
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2016/09/11 13:10:07:2 41.98 21.50 5.0 5.2 FYR Macedonia
Stations used:
AC.KBN AC.SRN AC.VLO CR.STON CR.ZAG GE.TIRR HT.ALN HT.GRG
HT.HORT HT.KNT HT.LIT HT.PAIG HT.SIGR HT.SOH HT.SRS HT.THE
HU.CSKK HU.KOVH HU.MORH HU.MPLH HU.TIH KO.GADA MN.BLY
MN.DIVS MN.PDG MN.TIR MN.VTS SJ.BBLS SJ.FRGS SL.DOBS
SL.GBRS SL.GCIS SL.GOLS SL.GROS SL.KOGS SL.VISS
Filtering commands used:
cut o DIST/3.3 -20 o DIST/3.3 +70
rtr
taper w 0.1
hp c 0.02 n 3
lp c 0.06 n 3
Best Fitting Double Couple
Mo = 3.13e+23 dyne-cm
Mw = 4.93
Z = 14 km
Plane Strike Dip Rake
NP1 125 75 -35
NP2 225 56 -162
Principal Axes:
Axis Value Plunge Azimuth
T 3.13e+23 12 179
N 0.00e+00 52 285
P -3.13e+23 35 80
Moment Tensor: (dyne-cm)
Component Value
Mxx 2.93e+23
Mxy -4.25e+22
Mxz -8.92e+22
Myy -2.03e+23
Myz -1.43e+23
Mzz -8.97e+22
##############
######################
############################
######################--------
###################---------------
--###############-------------------
----############----------------------
-------#######--------------------------
---------####------------------- -----
-----------#--------------------- P ------
-----------###------------------- ------
----------######--------------------------
---------#########------------------------
-------#############--------------------
------#################-----------------
-----####################-------------
---##########################-------
--################################
##############################
############# ############
########## T #########
###### #####
Global CMT Convention Moment Tensor:
R T P
-8.97e+22 -8.92e+22 1.43e+23
-8.92e+22 2.93e+23 4.25e+22
1.43e+23 4.25e+22 -2.03e+23
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.EU/20160911131007/index.html
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STK = 125
DIP = 75
RAKE = -35
MW = 4.93
HS = 14.0
The NDK file is 20160911131007.ndk The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2016/09/11 13:10:07:2 41.98 21.50 5.0 5.2 FYR Macedonia
Stations used:
AC.KBN AC.SRN AC.VLO CR.STON CR.ZAG GE.TIRR HT.ALN HT.GRG
HT.HORT HT.KNT HT.LIT HT.PAIG HT.SIGR HT.SOH HT.SRS HT.THE
HU.CSKK HU.KOVH HU.MORH HU.MPLH HU.TIH KO.GADA MN.BLY
MN.DIVS MN.PDG MN.TIR MN.VTS SJ.BBLS SJ.FRGS SL.DOBS
SL.GBRS SL.GCIS SL.GOLS SL.GROS SL.KOGS SL.VISS
Filtering commands used:
cut o DIST/3.3 -20 o DIST/3.3 +70
rtr
taper w 0.1
hp c 0.02 n 3
lp c 0.06 n 3
Best Fitting Double Couple
Mo = 3.13e+23 dyne-cm
Mw = 4.93
Z = 14 km
Plane Strike Dip Rake
NP1 125 75 -35
NP2 225 56 -162
Principal Axes:
Axis Value Plunge Azimuth
T 3.13e+23 12 179
N 0.00e+00 52 285
P -3.13e+23 35 80
Moment Tensor: (dyne-cm)
Component Value
Mxx 2.93e+23
Mxy -4.25e+22
Mxz -8.92e+22
Myy -2.03e+23
Myz -1.43e+23
Mzz -8.97e+22
##############
######################
############################
######################--------
###################---------------
--###############-------------------
----############----------------------
-------#######--------------------------
---------####------------------- -----
-----------#--------------------- P ------
-----------###------------------- ------
----------######--------------------------
---------#########------------------------
-------#############--------------------
------#################-----------------
-----####################-------------
---##########################-------
--################################
##############################
############# ############
########## T #########
###### #####
Global CMT Convention Moment Tensor:
R T P
-8.97e+22 -8.92e+22 1.43e+23
-8.92e+22 2.93e+23 4.25e+22
1.43e+23 4.25e+22 -2.03e+23
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.EU/20160911131007/index.html
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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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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 -20 o DIST/3.3 +70 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 1.0 125 90 0 4.55 0.3856
WVFGRD96 2.0 130 75 15 4.65 0.4714
WVFGRD96 3.0 130 65 10 4.69 0.4991
WVFGRD96 4.0 130 60 5 4.72 0.5217
WVFGRD96 5.0 125 60 -15 4.75 0.5464
WVFGRD96 6.0 125 60 -20 4.78 0.5752
WVFGRD96 7.0 125 65 -30 4.80 0.6053
WVFGRD96 8.0 120 65 -40 4.86 0.6289
WVFGRD96 9.0 120 65 -40 4.88 0.6579
WVFGRD96 10.0 120 65 -40 4.89 0.6803
WVFGRD96 11.0 120 65 -40 4.91 0.6955
WVFGRD96 12.0 120 65 -40 4.92 0.7042
WVFGRD96 13.0 125 70 -35 4.92 0.7097
WVFGRD96 14.0 125 75 -35 4.93 0.7113
WVFGRD96 15.0 125 75 -35 4.94 0.7106
WVFGRD96 16.0 125 75 -30 4.94 0.7067
WVFGRD96 17.0 125 75 -30 4.95 0.7007
WVFGRD96 18.0 125 75 -30 4.96 0.6920
WVFGRD96 19.0 125 80 -30 4.97 0.6830
WVFGRD96 20.0 125 80 -30 4.98 0.6726
WVFGRD96 21.0 125 80 -30 4.99 0.6612
WVFGRD96 22.0 125 80 -30 4.99 0.6489
WVFGRD96 23.0 130 85 -30 5.00 0.6368
WVFGRD96 24.0 130 85 -30 5.00 0.6248
WVFGRD96 25.0 130 85 -30 5.01 0.6116
WVFGRD96 26.0 130 85 -30 5.02 0.5983
WVFGRD96 27.0 130 85 -30 5.02 0.5846
WVFGRD96 28.0 310 85 25 5.03 0.5718
WVFGRD96 29.0 310 85 25 5.04 0.5593
The best solution is
WVFGRD96 14.0 125 75 -35 4.93 0.7113
The mechanism correspond 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 +70 rtr taper w 0.1 hp c 0.02 n 3 lp c 0.06 n 3
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| 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.
Should the national backbone of the USGS Advanced National Seismic System (ANSS) be implemented with an interstation separation of 300 km, it is very likely that an earthquake such as this would have been recorded at distances on the order of 100-200 km. This means that the closest station would have information on source depth and mechanism that was lacking here.
Dr. Harley Benz, USGS, provided the USGS USNSN digital data. The digital data used in this study were provided by Natural Resources Canada through their AUTODRM site http://www.seismo.nrcan.gc.ca/nwfa/autodrm/autodrm_req_e.php, and IRIS using their BUD interface.
Thanks also to the many seismic network operators whose dedication make this effort possible: University of Alaska, University of Washington, Oregon State University, University of Utah, Montana Bureas of Mines, UC Berkely, Caltech, UC San Diego, Saint L ouis University, Universityof Memphis, Lamont Doehrty Earth Observatory, Boston College, the Iris stations and the Transportable Array of EarthScope.
The WUS 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:
DATE=Sun Sep 11 10:03:48 CDT 2016