2017/01/27 17:07:58 40.77 19.91 10 4.7 Albania
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2017/01/27 17:07:58:0 40.77 19.91 10.0 4.7 Albania
Stations used:
AC.KBN AC.SRN AC.VLO BS.PLVB CR.ZAG GE.APE HA.LAKA HL.ATH
HL.DION HL.EVR HL.JAN HL.KEF3 HL.KEF4 HL.KEK HL.KYMI HL.KZN
HL.LKR HL.NEO HL.NVR HL.PENT HL.RDO HL.RLS HL.SMTH HL.THL
HL.VLS HL.VLY HP.ANX HP.LTHK HP.PVO HP.SERG HT.HORT HT.KNT
HT.LKD2 HT.THE HU.KOVH HU.MORH ME.KOME MN.DIVS MN.PDG
MN.TIR MN.VTS RO.BZS RO.COPA RO.DEV RO.GZR RO.HERR RO.HUMR
RO.MDVR RO.PUNG RO.SIRR RO.VLAD SJ.BBLS SJ.FRGS
Filtering commands used:
cut o DIST/3.3 -30 o DIST/3.3 +70
rtr
taper w 0.1
hp c 0.02 n 3
lp c 0.07 n 3
Best Fitting Double Couple
Mo = 1.32e+23 dyne-cm
Mw = 4.68
Z = 14 km
Plane Strike Dip Rake
NP1 110 75 65
NP2 351 29 148
Principal Axes:
Axis Value Plunge Azimuth
T 1.32e+23 53 350
N 0.00e+00 24 117
P -1.32e+23 26 219
Moment Tensor: (dyne-cm)
Component Value
Mxx -1.82e+22
Mxy -6.04e+22
Mxz 1.02e+23
Myy -4.16e+22
Myz 2.18e+22
Mzz 5.97e+22
########------
################------
#####################-------
########################------
############################------
############### ############------
################ T #############------
-################ ##############------
---###############################------
-------#############################------
----------##########################------
-------------#######################------
------------------##################------
----------------------#############-----
-----------------------------#####------
---------------------------------#####
------- ---------------------#####
------ P --------------------#####
---- -------------------####
------------------------####
-------------------###
------------##
Global CMT Convention Moment Tensor:
R T P
5.97e+22 1.02e+23 -2.18e+22
1.02e+23 -1.82e+22 6.04e+22
-2.18e+22 6.04e+22 -4.16e+22
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.EU/20170127170758/index.html
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STK = 110
DIP = 75
RAKE = 65
MW = 4.68
HS = 14.0
The NDK file is 20170127170758.ndk The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2017/01/27 17:07:58:0 40.77 19.91 10.0 4.7 Albania
Stations used:
AC.KBN AC.SRN AC.VLO BS.PLVB CR.ZAG GE.APE HA.LAKA HL.ATH
HL.DION HL.EVR HL.JAN HL.KEF3 HL.KEF4 HL.KEK HL.KYMI HL.KZN
HL.LKR HL.NEO HL.NVR HL.PENT HL.RDO HL.RLS HL.SMTH HL.THL
HL.VLS HL.VLY HP.ANX HP.LTHK HP.PVO HP.SERG HT.HORT HT.KNT
HT.LKD2 HT.THE HU.KOVH HU.MORH ME.KOME MN.DIVS MN.PDG
MN.TIR MN.VTS RO.BZS RO.COPA RO.DEV RO.GZR RO.HERR RO.HUMR
RO.MDVR RO.PUNG RO.SIRR RO.VLAD SJ.BBLS SJ.FRGS
Filtering commands used:
cut o DIST/3.3 -30 o DIST/3.3 +70
rtr
taper w 0.1
hp c 0.02 n 3
lp c 0.07 n 3
Best Fitting Double Couple
Mo = 1.32e+23 dyne-cm
Mw = 4.68
Z = 14 km
Plane Strike Dip Rake
NP1 110 75 65
NP2 351 29 148
Principal Axes:
Axis Value Plunge Azimuth
T 1.32e+23 53 350
N 0.00e+00 24 117
P -1.32e+23 26 219
Moment Tensor: (dyne-cm)
Component Value
Mxx -1.82e+22
Mxy -6.04e+22
Mxz 1.02e+23
Myy -4.16e+22
Myz 2.18e+22
Mzz 5.97e+22
########------
################------
#####################-------
########################------
############################------
############### ############------
################ T #############------
-################ ##############------
---###############################------
-------#############################------
----------##########################------
-------------#######################------
------------------##################------
----------------------#############-----
-----------------------------#####------
---------------------------------#####
------- ---------------------#####
------ P --------------------#####
---- -------------------####
------------------------####
-------------------###
------------##
Global CMT Convention Moment Tensor:
R T P
5.97e+22 1.02e+23 -2.18e+22
1.02e+23 -1.82e+22 6.04e+22
-2.18e+22 6.04e+22 -4.16e+22
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.EU/20170127170758/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 -30 o DIST/3.3 +70 rtr taper w 0.1 hp c 0.02 n 3 lp c 0.07 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 70 50 -85 4.36 0.3842
WVFGRD96 2.0 70 50 -85 4.47 0.4560
WVFGRD96 3.0 75 55 -80 4.53 0.4098
WVFGRD96 4.0 265 85 -65 4.54 0.4004
WVFGRD96 5.0 90 90 65 4.54 0.4601
WVFGRD96 6.0 85 90 65 4.55 0.5069
WVFGRD96 7.0 85 90 60 4.55 0.5416
WVFGRD96 8.0 85 90 65 4.62 0.5626
WVFGRD96 9.0 90 85 65 4.63 0.5883
WVFGRD96 10.0 90 85 65 4.63 0.6065
WVFGRD96 11.0 95 80 65 4.64 0.6181
WVFGRD96 12.0 95 80 65 4.65 0.6258
WVFGRD96 13.0 95 80 60 4.66 0.6291
WVFGRD96 14.0 110 75 65 4.68 0.6293
WVFGRD96 15.0 110 75 60 4.69 0.6265
WVFGRD96 16.0 110 75 60 4.70 0.6218
WVFGRD96 17.0 110 75 60 4.70 0.6151
WVFGRD96 18.0 110 75 60 4.71 0.6066
WVFGRD96 19.0 110 75 60 4.71 0.5966
WVFGRD96 20.0 170 30 5 4.69 0.5858
WVFGRD96 21.0 170 30 5 4.70 0.5787
WVFGRD96 22.0 170 30 5 4.71 0.5701
WVFGRD96 23.0 170 30 10 4.72 0.5607
WVFGRD96 24.0 170 30 10 4.72 0.5507
WVFGRD96 25.0 170 30 10 4.73 0.5399
WVFGRD96 26.0 175 30 15 4.73 0.5287
WVFGRD96 27.0 175 30 15 4.74 0.5168
WVFGRD96 28.0 175 30 15 4.74 0.5041
WVFGRD96 29.0 175 30 20 4.75 0.4912
The best solution is
WVFGRD96 14.0 110 75 65 4.68 0.6293
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 -30 o DIST/3.3 +70 rtr taper w 0.1 hp c 0.02 n 3 lp c 0.07 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=Wed Feb 1 08:19:15 CST 2017