USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/09/06 21:49:42:4 41.47 20.40 3.0 5.4 Albania
Best Fitting Double Couple
Mo = 1.01e+24 dyne-cm
Mw = 5.27
Z = 5 km
Plane Strike Dip Rake
NP1 190 55 -90
NP2 10 35 -90
Principal Axes:
Axis Value Plunge Azimuth
T 1.01e+24 10 280
N 0.00e+00 -0 190
P -1.01e+24 80 100
Moment Tensor: (dyne-cm)
Component Value
Mxx 2.87e+22
Mxy -1.63e+23
Mxz 6.01e+22
Myy 9.22e+23
Myz -3.41e+23
Mzz -9.51e+23
#########---##
##########--------####
############-----------#####
###########--------------#####
############----------------######
############------------------######
############--------------------######
#############--------------------#######
#########----------------------######
# T #########----------------------#######
# ########----------- ---------#######
############----------- P ---------#######
############----------- --------########
###########----------------------#######
###########---------------------########
##########--------------------########
#########--------------------#######
#########-----------------########
#######----------------#######
#######-------------########
#####----------#######
##-----#######
Global CMT Convention Moment Tensor:
R T P
-9.51e+23 6.01e+22 3.41e+23
6.01e+22 2.87e+22 1.63e+23
3.41e+23 1.63e+23 9.22e+23
Details of the solution is found at
http://www.eas.slu.edu/Earthquake_Center/MECH.NA/20090906214942/index.html
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STK = 10
DIP = 35
RAKE = -90
MW = 5.27
HS = 5.0
The waveform inversion is preferred. I initially used the WUS velocity model for observations less than 700 km, and then tried the nnCIA model with observations less than 500 km. The waveform fits for the nnCIA model were excellent. I question the gains of stations SOH and PLD. The low T amplitudes on at SRS and DIVS may be because of alignment or multipathing since these are nodal amplitudes on the T component. The odd observation is what is Mw? The EMSC summary of moment tensors gives values from 5.3 to 5.6. This is a huge variation in expected ground motion since this will map into about a factor of 2 in moment.
The EMSC summary of published moment tensors is emsccmtraw.txt
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/09/06 21:49:42:4 41.47 20.40 3.0 5.4 Albania
Best Fitting Double Couple
Mo = 1.01e+24 dyne-cm
Mw = 5.27
Z = 5 km
Plane Strike Dip Rake
NP1 190 55 -90
NP2 10 35 -90
Principal Axes:
Axis Value Plunge Azimuth
T 1.01e+24 10 280
N 0.00e+00 -0 190
P -1.01e+24 80 100
Moment Tensor: (dyne-cm)
Component Value
Mxx 2.87e+22
Mxy -1.63e+23
Mxz 6.01e+22
Myy 9.22e+23
Myz -3.41e+23
Mzz -9.51e+23
#########---##
##########--------####
############-----------#####
###########--------------#####
############----------------######
############------------------######
############--------------------######
#############--------------------#######
#########----------------------######
# T #########----------------------#######
# ########----------- ---------#######
############----------- P ---------#######
############----------- --------########
###########----------------------#######
###########---------------------########
##########--------------------########
#########--------------------#######
#########-----------------########
#######----------------#######
#######-------------########
#####----------#######
##-----#######
Global CMT Convention Moment Tensor:
R T P
-9.51e+23 6.01e+22 3.41e+23
6.01e+22 2.87e+22 1.63e+23
3.41e+23 1.63e+23 9.22e+23
Details of the solution is found at
http://www.eas.slu.edu/Earthquake_Center/MECH.NA/20090906214942/index.html
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09/09/06 21:49:42.60
ALBANIA
Epicenter: 41.438 20.384
MW 5.4
USGS MOMENT TENSOR SOLUTION
Depth 3 No. of sta: 51
Moment Tensor; Scale 10**17 Nm
Mrr=-1.32 Mtt=-0.03
Mpp= 1.34 Mrt= 0.63
Mrp= 1.04 Mtp= 0.10
Principal axes:
T Val= 1.75 Plg=20 Azm=280
N 0.09 12 15
P -1.85 65 136
Best Double Couple:Mo=1.8*10**17
NP1:Strike=202 Dip=67 Slip= -76
NP2: 349 27 -119
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###########--####
#############---#####
##############------#####
##############---------######
##############-----------######
#############-------------#####
## ########---------------#####
## T #######----------------#####
## #######----------------#####
###########------- -------#####
###########------- P -------#####
#########-------- -------####
#########-----------------#####
########-----------------####
######----------------###
####--------------###
##------------###
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09/09/06 21:49:42.60
ALBANIA
Epicenter: 41.438 20.384
MW 5.6
USGS CENTROID MOMENT TENSOR
09/09/06 21:49:48.59
Centroid: 41.758 20.362
Depth 10 No. of sta:120
Moment Tensor; Scale 10**17 Nm
Mrr=-1.64 Mtt=-0.37
Mpp= 2.01 Mrt= 2.15
Mrp= 0.55 Mtp= 0.12
Principal axes:
T Val= 2.22 Plg=16 Azm=287
N 1.05 31 27
P -3.27 53 173
Best Double Couple:Mo=2.7*10**17
NP1:Strike=340 Dip=39 Slip=-144
NP2: 222 69 -55
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#######----------
############---------
################----#####
###################-#########
#################-----#########
# ###########--------########
## T #########-----------########
## ########-------------#######
###########---------------#######
##########-----------------######
#########------------------######
#######-------- --------#####
######--------- P -------######
####---------- -------#####
##-------------------####
------------------###
---------------##
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September 6, 2009, ALBANIA, MW=5.5
Goran Ekstrom
Meredith Nettles
CENTROID-MOMENT-TENSOR SOLUTION
GCMT EVENT: C200909062149A
DATA: II IU CU IC G GE
L.P.BODY WAVES: 66S, 124C, T= 40
MANTLE WAVES: 35S, 35C, T=125
SURFACE WAVES: 84S, 170C, T= 50
TIMESTAMP: Q-20090907151330
CENTROID LOCATION:
ORIGIN TIME: 21:49:47.3 0.1
LAT:41.36N 0.01;LON: 20.34E 0.01
DEP: 12.0 FIX;TRIANG HDUR: 1.3
MOMENT TENSOR: SCALE 10**24 D-CM
RR=-1.850 0.026; TT=-0.062 0.027
PP= 1.910 0.023; RT=-0.562 0.071
RP=-0.306 0.060; TP= 0.427 0.023
PRINCIPAL AXES:
1.(T) VAL= 2.044;PLG= 6;AZM=103
2.(N) -0.025; 14; 195
3.(P) -2.020; 74; 350
BEST DBLE.COUPLE:M0= 2.03*10**24
NP1: STRIKE=177;DIP=41;SLIP=-112
NP2: STRIKE= 26;DIP=53;SLIP= -72
###--------
#####------------##
#####---------------###
######----------------#####
######------------------#####
#######------------------######
######------- ---------######
#######------- P --------########
#######------- --------########
#######-----------------######
#######----------------####### T
######---------------########
#######-------------###########
#######-----------###########
#######--------############
######-----############
###################
----#######
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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:
hp c 0.02 n 3 lp c 0.05 n 3The results of this grid search from 0.5 to 19 km depth are as follow:
DEPTH STK DIP RAKE MW FIT
WVFGRD96 0.5 45 30 -25 5.11 0.4872
WVFGRD96 1.0 40 40 -40 5.06 0.5207
WVFGRD96 2.0 30 35 -55 5.13 0.5918
WVFGRD96 3.0 185 55 -95 5.18 0.6726
WVFGRD96 4.0 10 40 -90 5.22 0.7321
WVFGRD96 5.0 10 35 -90 5.27 0.7710
WVFGRD96 6.0 5 35 -95 5.28 0.7564
WVFGRD96 7.0 0 40 -105 5.26 0.7007
WVFGRD96 8.0 215 60 -55 5.19 0.5988
WVFGRD96 9.0 40 60 -30 5.17 0.5701
WVFGRD96 10.0 40 60 -25 5.18 0.5694
WVFGRD96 11.0 45 65 -25 5.18 0.5718
WVFGRD96 12.0 45 65 -25 5.19 0.5763
WVFGRD96 13.0 45 70 -25 5.19 0.5818
WVFGRD96 14.0 45 70 -25 5.20 0.5888
WVFGRD96 15.0 45 70 -25 5.21 0.5919
WVFGRD96 16.0 45 70 -25 5.22 0.5957
WVFGRD96 17.0 45 70 -25 5.23 0.5982
WVFGRD96 18.0 45 70 -25 5.24 0.6005
WVFGRD96 19.0 45 75 -25 5.24 0.6017
WVFGRD96 20.0 45 75 -25 5.25 0.6035
WVFGRD96 21.0 45 75 -25 5.26 0.6039
WVFGRD96 22.0 45 75 -25 5.27 0.6044
WVFGRD96 23.0 45 75 -25 5.28 0.6039
WVFGRD96 24.0 240 75 25 5.28 0.6028
WVFGRD96 25.0 240 75 25 5.28 0.6023
WVFGRD96 26.0 240 75 25 5.29 0.6022
WVFGRD96 27.0 240 75 25 5.30 0.6019
WVFGRD96 28.0 240 75 20 5.32 0.6014
WVFGRD96 29.0 240 75 20 5.33 0.6031
The best solution is
WVFGRD96 5.0 10 35 -90 5.27 0.7710
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 componnet is plotted to the same scale and peak amplitudes are indicated by the numbers to the left of each trace. The number in black at the rightr of each predicted traces 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 bandpass filter used in the processing and for the display was
hp c 0.02 n 3 lp c 0.05 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. |
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 nnCIA used for the waveform synthetic seismograms and for the surface wave eigenfunctions and dispersion is as follows:
MODEL.01
C.It. A. Di Luzio et al Earth Plan Lettrs 280 (2009) 1-12 Fig 5. 7-8 MODEL/SURF3
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
1.5000 3.7497 2.1436 2.2753 0.500E-02 0.100E-01 0.00 0.00 1.00 1.00
3.0000 4.9399 2.8210 2.4858 0.500E-02 0.100E-01 0.00 0.00 1.00 1.00
3.0000 6.0129 3.4336 2.7058 0.500E-02 0.100E-01 0.00 0.00 1.00 1.00
7.0000 5.5516 3.1475 2.6093 0.167E-02 0.333E-02 0.00 0.00 1.00 1.00
15.0000 5.8805 3.3583 2.6770 0.167E-02 0.333E-02 0.00 0.00 1.00 1.00
6.0000 7.1059 4.0081 3.0002 0.167E-02 0.333E-02 0.00 0.00 1.00 1.00
8.0000 7.1000 3.9864 3.0120 0.167E-02 0.333E-02 0.00 0.00 1.00 1.00
0.0000 7.9000 4.4036 3.2760 0.167E-02 0.333E-02 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=Tue Sep 8 08:20:10 CDT 2009