2017/04/08 13:53:02 41.80 20.03 10 5.0 Albania
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2017/04/08 13:53:02:6 41.80 20.03 10.0 5.0 Albania
Stations used:
AC.KBN AC.SRN AC.VLO BS.BLKB HT.HORT HT.KNT HT.LKD2 HT.PAIG
HT.SOH HT.SRS HT.THE HU.KOVH MN.BLY MN.DIVS MN.PDG MN.TIR
MN.VTS RO.BAIL RO.BANR RO.BZS RO.COPA RO.DEV RO.GZR RO.HERR
RO.HUMR RO.LOT RO.MDVR RO.VLAD SJ.BBLS SJ.FRGS
Filtering commands used:
cut o DIST/3.3 -30 o DIST/3.3 +60
rtr
taper w 0.1
hp c 0.02 n 3
lp c 0.08 n 3
Best Fitting Double Couple
Mo = 1.46e+23 dyne-cm
Mw = 4.71
Z = 22 km
Plane Strike Dip Rake
NP1 177 54 -127
NP2 50 50 -50
Principal Axes:
Axis Value Plunge Azimuth
T 1.46e+23 2 293
N 0.00e+00 29 202
P -1.46e+23 60 27
Moment Tensor: (dyne-cm)
Component Value
Mxx -6.17e+21
Mxy -6.68e+22
Mxz -5.37e+22
Myy 1.16e+23
Myz -3.38e+22
Mzz -1.10e+23
#####---------
#######---------------
#########-------------------
#########---------------------
##########-----------------------#
#########------------------------##
T #########---------- -----------###
########----------- P -----------####
###########----------- ----------#####
############-----------------------#######
############-----------------------#######
############---------------------#########
############--------------------##########
###########-------------------##########
############----------------############
###########--------------#############
###########----------###############
###########------#################
-########-####################
----------##################
--------##############
------########
Global CMT Convention Moment Tensor:
R T P
-1.10e+23 -5.37e+22 3.38e+22
-5.37e+22 -6.17e+21 6.68e+22
3.38e+22 6.68e+22 1.16e+23
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.EU/20170408135302/index.html
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STK = 50
DIP = 50
RAKE = -50
MW = 4.71
HS = 22.0
The NDK file is 20170408135302.ndk The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2017/04/08 13:53:02:6 41.80 20.03 10.0 5.0 Albania
Stations used:
AC.KBN AC.SRN AC.VLO BS.BLKB HT.HORT HT.KNT HT.LKD2 HT.PAIG
HT.SOH HT.SRS HT.THE HU.KOVH MN.BLY MN.DIVS MN.PDG MN.TIR
MN.VTS RO.BAIL RO.BANR RO.BZS RO.COPA RO.DEV RO.GZR RO.HERR
RO.HUMR RO.LOT RO.MDVR RO.VLAD SJ.BBLS SJ.FRGS
Filtering commands used:
cut o DIST/3.3 -30 o DIST/3.3 +60
rtr
taper w 0.1
hp c 0.02 n 3
lp c 0.08 n 3
Best Fitting Double Couple
Mo = 1.46e+23 dyne-cm
Mw = 4.71
Z = 22 km
Plane Strike Dip Rake
NP1 177 54 -127
NP2 50 50 -50
Principal Axes:
Axis Value Plunge Azimuth
T 1.46e+23 2 293
N 0.00e+00 29 202
P -1.46e+23 60 27
Moment Tensor: (dyne-cm)
Component Value
Mxx -6.17e+21
Mxy -6.68e+22
Mxz -5.37e+22
Myy 1.16e+23
Myz -3.38e+22
Mzz -1.10e+23
#####---------
#######---------------
#########-------------------
#########---------------------
##########-----------------------#
#########------------------------##
T #########---------- -----------###
########----------- P -----------####
###########----------- ----------#####
############-----------------------#######
############-----------------------#######
############---------------------#########
############--------------------##########
###########-------------------##########
############----------------############
###########--------------#############
###########----------###############
###########------#################
-########-####################
----------##################
--------##############
------########
Global CMT Convention Moment Tensor:
R T P
-1.10e+23 -5.37e+22 3.38e+22
-5.37e+22 -6.17e+21 6.68e+22
3.38e+22 6.68e+22 1.16e+23
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.EU/20170408135302/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 +60 rtr taper w 0.1 hp c 0.02 n 3 lp c 0.08 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 80 45 85 4.19 0.2395
WVFGRD96 2.0 85 45 90 4.32 0.3169
WVFGRD96 3.0 30 50 90 4.41 0.2731
WVFGRD96 4.0 260 75 50 4.37 0.2933
WVFGRD96 5.0 250 85 45 4.38 0.3247
WVFGRD96 6.0 65 90 -45 4.40 0.3575
WVFGRD96 7.0 65 90 -40 4.42 0.3926
WVFGRD96 8.0 65 90 -45 4.48 0.4253
WVFGRD96 9.0 65 90 -45 4.50 0.4569
WVFGRD96 10.0 65 90 -40 4.51 0.4851
WVFGRD96 11.0 245 90 40 4.53 0.5093
WVFGRD96 12.0 60 75 -45 4.55 0.5354
WVFGRD96 13.0 50 55 -50 4.60 0.5652
WVFGRD96 14.0 50 55 -50 4.61 0.5966
WVFGRD96 15.0 50 50 -50 4.64 0.6236
WVFGRD96 16.0 50 50 -50 4.65 0.6461
WVFGRD96 17.0 50 50 -50 4.66 0.6638
WVFGRD96 18.0 50 50 -50 4.67 0.6776
WVFGRD96 19.0 50 50 -50 4.68 0.6875
WVFGRD96 20.0 50 50 -50 4.69 0.6938
WVFGRD96 21.0 50 50 -50 4.70 0.6973
WVFGRD96 22.0 50 50 -50 4.71 0.6977
WVFGRD96 23.0 50 50 -50 4.72 0.6952
WVFGRD96 24.0 50 50 -50 4.72 0.6905
WVFGRD96 25.0 50 50 -50 4.73 0.6839
WVFGRD96 26.0 50 55 -50 4.73 0.6760
WVFGRD96 27.0 50 55 -50 4.73 0.6672
WVFGRD96 28.0 50 55 -50 4.74 0.6570
WVFGRD96 29.0 50 55 -50 4.74 0.6454
The best solution is
WVFGRD96 22.0 50 50 -50 4.71 0.6977
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 +60 rtr taper w 0.1 hp c 0.02 n 3 lp c 0.08 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=Sat Apr 8 09:41:37 CDT 2017