2009/08/21 13:39:56 41.815 19.183 10.0 4.9 Adriatic Sea
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/08/21 13:39:56:0 41.81 19.18 10.0 4.9 Adriatic Sea
Stations used:
CZ.KHC CZ.OKC GE.MORC GE.PSZ GE.TIRR HU.PKSM HU.SOP HU.TRPA
MN.DIVS MN.IDI MN.PDG MN.TIR MN.VTS PL.OJC RO.BZS RO.DRGR
SK.CRVS SK.VYHS
Filtering commands used:
hp c 0.02 n 3
lp c 0.05 n 3
Best Fitting Double Couple
Mo = 3.35e+23 dyne-cm
Mw = 4.95
Z = 18 km
Plane Strike Dip Rake
NP1 151 61 96
NP2 320 30 80
Principal Axes:
Axis Value Plunge Azimuth
T 3.35e+23 74 76
N 0.00e+00 5 329
P -3.35e+23 15 237
Moment Tensor: (dyne-cm)
Component Value
Mxx -8.94e+22
Mxy -1.36e+23
Mxz 6.74e+22
Myy -1.96e+23
Myz 1.59e+23
Mzz 2.86e+23
--------------
#---------------------
---##############-----------
----#################---------
------####################--------
-------######################-------
--------#######################-------
----------#######################-------
----------########################------
------------########### ##########------
------------########### T ###########-----
-------------########## ###########-----
--------------#######################-----
--------------#######################---
---------------######################---
--- ---------####################---
-- P -----------##################--
- -------------###############--
-----------------#############
------------------#########-
-------------------###
--------------
Global CMT Convention Moment Tensor:
R T P
2.86e+23 6.74e+22 -1.59e+23
6.74e+22 -8.94e+22 1.36e+23
-1.59e+23 1.36e+23 -1.96e+23
Details of the solution is found at
http://www.eas.slu.edu/Earthquake_Center/MECH.NA/20090821133956/index.html
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STK = 320
DIP = 30
RAKE = 80
MW = 4.95
HS = 18.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/08/21 13:39:56:0 41.81 19.18 10.0 4.9 Adriatic Sea
Stations used:
CZ.KHC CZ.OKC GE.MORC GE.PSZ GE.TIRR HU.PKSM HU.SOP HU.TRPA
MN.DIVS MN.IDI MN.PDG MN.TIR MN.VTS PL.OJC RO.BZS RO.DRGR
SK.CRVS SK.VYHS
Filtering commands used:
hp c 0.02 n 3
lp c 0.05 n 3
Best Fitting Double Couple
Mo = 3.35e+23 dyne-cm
Mw = 4.95
Z = 18 km
Plane Strike Dip Rake
NP1 151 61 96
NP2 320 30 80
Principal Axes:
Axis Value Plunge Azimuth
T 3.35e+23 74 76
N 0.00e+00 5 329
P -3.35e+23 15 237
Moment Tensor: (dyne-cm)
Component Value
Mxx -8.94e+22
Mxy -1.36e+23
Mxz 6.74e+22
Myy -1.96e+23
Myz 1.59e+23
Mzz 2.86e+23
--------------
#---------------------
---##############-----------
----#################---------
------####################--------
-------######################-------
--------#######################-------
----------#######################-------
----------########################------
------------########### ##########------
------------########### T ###########-----
-------------########## ###########-----
--------------#######################-----
--------------#######################---
---------------######################---
--- ---------####################---
-- P -----------##################--
- -------------###############--
-----------------#############
------------------#########-
-------------------###
--------------
Global CMT Convention Moment Tensor:
R T P
2.86e+23 6.74e+22 -1.59e+23
6.74e+22 -8.94e+22 1.36e+23
-1.59e+23 1.36e+23 -1.96e+23
Details of the solution is found at
http://www.eas.slu.edu/Earthquake_Center/MECH.NA/20090821133956/index.html
|
Provided by ETHZ, AUTH, IGN, INGV-MEDNET, KOERI, NOA_IG, HARVARD, USGS, CPPT
From: pondrix@bo.ingv.it
FID: EFX26
DAT: 200908211556 GMT
C082109A 08/21/09 13:39:57.2 41.82 19.13 2.05.00.0ALBANIA
Nei BW: 2 2 40 SW:10 17 30 DT= 8.5 0.3 41.71 0.02 18.88 0.02 20.7 0.9
DUR 1.3 EX 23 2.93 0.38 -1.47 0.22 -1.46 0.22 1.18 0.38 -0.62 0.31 3.23 0.14
3.24 73 346 1.66 15 132 -4.90 9 224 4.07 331 38 114 122 56 72
CENTROID, MOMENT TENSOR SOLUTION
HARVARD EVENT-FILE NAME C082109A
DATA USED: GSN
L.P. BODY WAVES: 2S, 2C, T= 40
SURFACE WAVES: 10S, 17C, T= 30
CENTROID LOCATION:
ORIGIN TIME 13:40: 5.7 0.3
LAT 41.71N 0.02;LON 18.88E 0.02
DEP 20.7 0.9;HALF-DURATION 1.3
MOMENT TENSOR; SCALE 10**23 D-CM
MRR= 2.93 0.38; MTT=-1.47 0.22
MPP=-1.46 0.22; MRT= 1.18 0.38
MRP=-0.62 0.31; MTP= 3.23 0.14
PRINCIPAL AXES:
1.(T) VAL= 3.24;PLG=73;AZM=346
2.(N) 1.66; 15; 132
3.(P) -4.90; 9; 224
BEST DOUBLE COUPLE:M0=4.1*10**23
NP1:STRIKE=331;DIP=38;SLIP= 114
NP2:STRIKE=122;DIP=56;SLIP= 72
-----------
########-----------
##############---------
##################---------
-####################--------
--######################-------
---########## #########------
----########## T ##########------
------######## ##########------
-------#####################-----
---------###################-----
----------#################----
-------------##############----
-- -----------#########----
- P --------------------###
-------------------##
------------------#
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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 0.5 250 55 -85 4.47 0.2514
WVFGRD96 1.0 255 50 -80 4.49 0.2520
WVFGRD96 2.0 255 55 -80 4.60 0.3019
WVFGRD96 3.0 85 65 35 4.65 0.3038
WVFGRD96 4.0 280 85 -65 4.74 0.3454
WVFGRD96 5.0 280 85 -60 4.73 0.3959
WVFGRD96 6.0 105 90 55 4.74 0.4311
WVFGRD96 7.0 105 90 55 4.74 0.4605
WVFGRD96 8.0 105 90 60 4.80 0.4832
WVFGRD96 9.0 110 85 60 4.81 0.5019
WVFGRD96 10.0 115 75 60 4.82 0.5203
WVFGRD96 11.0 330 25 95 4.92 0.5553
WVFGRD96 12.0 330 30 95 4.93 0.5890
WVFGRD96 13.0 325 30 90 4.93 0.6144
WVFGRD96 14.0 325 30 90 4.94 0.6327
WVFGRD96 15.0 320 30 80 4.95 0.6447
WVFGRD96 16.0 320 30 80 4.95 0.6522
WVFGRD96 17.0 320 30 80 4.95 0.6559
WVFGRD96 18.0 320 30 80 4.95 0.6564
WVFGRD96 19.0 320 30 80 4.95 0.6544
WVFGRD96 20.0 320 30 80 4.96 0.6506
WVFGRD96 21.0 320 30 80 4.97 0.6486
WVFGRD96 22.0 320 30 80 4.97 0.6421
WVFGRD96 23.0 315 30 75 4.97 0.6348
WVFGRD96 24.0 315 30 75 4.97 0.6267
WVFGRD96 25.0 315 30 75 4.97 0.6157
WVFGRD96 26.0 315 30 75 4.97 0.6068
WVFGRD96 27.0 315 30 75 4.97 0.5977
WVFGRD96 28.0 315 30 75 4.98 0.5888
WVFGRD96 29.0 315 30 75 4.98 0.5798
The best solution is
WVFGRD96 18.0 320 30 80 4.95 0.6564
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 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=Fri Aug 21 11:33:20 MDT 2009