2009/04/07 17:47:37 42.275 13.464 15.0 5.30 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/04/07 17:47:37:0 42.28 13.46 15.0 5.3 Italy
Stations used:
IV.ARCI IV.BSSO IV.CAFR IV.CASP IV.CERT IV.CMPR IV.CRE
IV.CSNT IV.GIUL IV.GUAR IV.LNSS IV.MAON IV.MCEL IV.MIDA
IV.MNS IV.MODR IV.MSAG IV.MTCE IV.MTSN IV.MURB IV.NRCA
IV.PARC IV.PESA IV.RMP IV.SGRT IV.SIRI IV.TOLF IV.TRIV
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 2.24e+24 dyne-cm
Mw = 5.50
Z = 18 km
Plane Strike Dip Rake
NP1 340 75 -60
NP2 94 33 -152
Principal Axes:
Axis Value Plunge Azimuth
T 2.24e+24 24 47
N 0.00e+00 29 151
P -2.24e+24 51 284
Moment Tensor: (dyne-cm)
Component Value
Mxx 8.08e+23
Mxy 1.14e+24
Mxz 3.02e+23
Myy 1.61e+23
Myz 1.68e+24
Mzz -9.69e+23
##############
------################
----------##################
-------------#################
----------------########### ####
------------------########## T #####
--------------------######### ######
----------------------##################
--------- ----------##################
---------- P -----------##################
---------- ------------#################
#------------------------#################
##------------------------###############-
##-----------------------##############-
####----------------------############--
####---------------------##########---
######-------------------#######----
########----------------###-------
#############-----####--------
#####################-------
##################----
##############
Global CMT Convention Moment Tensor:
R T P
-9.69e+23 3.02e+23 -1.68e+24
3.02e+23 8.08e+23 -1.14e+24
-1.68e+24 -1.14e+24 1.61e+23
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090407174737/index.html
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STK = 340
DIP = 75
RAKE = -60
MW = 5.50
HS = 18.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/04/07 17:47:37:0 42.28 13.46 15.0 5.3 Italy
Stations used:
IV.ARCI IV.BSSO IV.CAFR IV.CASP IV.CERT IV.CMPR IV.CRE
IV.CSNT IV.GIUL IV.GUAR IV.LNSS IV.MAON IV.MCEL IV.MIDA
IV.MNS IV.MODR IV.MSAG IV.MTCE IV.MTSN IV.MURB IV.NRCA
IV.PARC IV.PESA IV.RMP IV.SGRT IV.SIRI IV.TOLF IV.TRIV
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 2.24e+24 dyne-cm
Mw = 5.50
Z = 18 km
Plane Strike Dip Rake
NP1 340 75 -60
NP2 94 33 -152
Principal Axes:
Axis Value Plunge Azimuth
T 2.24e+24 24 47
N 0.00e+00 29 151
P -2.24e+24 51 284
Moment Tensor: (dyne-cm)
Component Value
Mxx 8.08e+23
Mxy 1.14e+24
Mxz 3.02e+23
Myy 1.61e+23
Myz 1.68e+24
Mzz -9.69e+23
##############
------################
----------##################
-------------#################
----------------########### ####
------------------########## T #####
--------------------######### ######
----------------------##################
--------- ----------##################
---------- P -----------##################
---------- ------------#################
#------------------------#################
##------------------------###############-
##-----------------------##############-
####----------------------############--
####---------------------##########---
######-------------------#######----
########----------------###-------
#############-----####--------
#####################-------
##################----
##############
Global CMT Convention Moment Tensor:
R T P
-9.69e+23 3.02e+23 -1.68e+24
3.02e+23 8.08e+23 -1.14e+24
-1.68e+24 -1.14e+24 1.61e+23
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090407174737/index.html
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April 7, 2009, CENTRAL ITALY, MW=5.5
Liz Starin
CENTROID-MOMENT-TENSOR SOLUTION
GCMT EVENT: C200904071747A
DATA: II IU CU G GE
L.P.BODY WAVES: 65S, 111C, T= 40
MANTLE WAVES: 13S, 13C, T=125
SURFACE WAVES: 84S, 155C, T= 50
TIMESTAMP: Q-20090407170307
CENTROID LOCATION:
ORIGIN TIME: 17:47:42.3 0.1
LAT:42.26N 0.01;LON: 13.46E 0.01
DEP: 20.0 0.5;TRIANG HDUR: 1.4
MOMENT TENSOR: SCALE 10**24 D-CM
RR=-1.630 0.038; TT= 0.767 0.030
PP= 0.865 0.031; RT=-0.763 0.066
RP=-1.120 0.071; TP=-1.590 0.026
PRINCIPAL AXES:
1.(T) VAL= 2.428;PLG= 4;AZM= 48
2.(N) 0.181; 36; 141
3.(P) -2.607; 54; 312
BEST DBLE.COUPLE:M0= 2.52*10**24
NP1: STRIKE=106;DIP=51;SLIP=-138
NP2: STRIKE=347;DIP=59;SLIP= -47
---########
---------##########
-------------#########
----------------######## 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 0.10 n 3The results of this grid search from 0.5 to 19 km depth are as follow:
DEPTH STK DIP RAKE MW FIT
WVFGRD96 0.5 330 45 -90 4.95 0.2175
WVFGRD96 1.0 150 45 -90 4.96 0.1730
WVFGRD96 2.0 330 45 -90 5.13 0.2486
WVFGRD96 3.0 170 70 -50 5.09 0.1827
WVFGRD96 4.0 175 90 60 5.14 0.2170
WVFGRD96 5.0 170 90 60 5.17 0.2712
WVFGRD96 6.0 170 90 60 5.20 0.3210
WVFGRD96 7.0 350 90 -55 5.22 0.3644
WVFGRD96 8.0 170 90 60 5.30 0.3988
WVFGRD96 9.0 345 80 -60 5.33 0.4441
WVFGRD96 10.0 340 75 -60 5.36 0.4836
WVFGRD96 11.0 340 75 -60 5.38 0.5191
WVFGRD96 12.0 340 75 -60 5.40 0.5488
WVFGRD96 13.0 340 75 -60 5.42 0.5732
WVFGRD96 14.0 340 75 -60 5.44 0.5925
WVFGRD96 15.0 340 75 -60 5.46 0.6068
WVFGRD96 16.0 340 75 -60 5.47 0.6164
WVFGRD96 17.0 340 75 -60 5.49 0.6219
WVFGRD96 18.0 340 75 -60 5.50 0.6232
WVFGRD96 19.0 340 75 -60 5.52 0.6212
WVFGRD96 20.0 340 75 -60 5.53 0.6164
WVFGRD96 21.0 340 75 -60 5.54 0.6095
WVFGRD96 22.0 340 75 -60 5.55 0.5995
WVFGRD96 23.0 340 75 -60 5.56 0.5875
WVFGRD96 24.0 340 75 -60 5.57 0.5737
WVFGRD96 25.0 340 75 -65 5.57 0.5589
WVFGRD96 26.0 340 75 -65 5.58 0.5432
WVFGRD96 27.0 340 75 -65 5.59 0.5265
WVFGRD96 28.0 340 75 -65 5.59 0.5096
WVFGRD96 29.0 340 75 -65 5.60 0.4923
The best solution is
WVFGRD96 18.0 340 75 -60 5.50 0.6232
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. 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 0.10 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. |
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=Mon Aug 31 14:56:03 CDT 2009