2009/09/24 16:14:57 42.453 13.330 4.1 9.7 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/09/24 16:14:57:0 42.45 13.33 4.1 9.7 Italy
Stations used:
IV.AOI IV.ARVD IV.CAFI IV.CAFR IV.CERA IV.CESX IV.CING
IV.CRE IV.FAGN IV.FDMO IV.FIAM IV.FSSB IV.GIUL IV.GUMA
IV.INTR IV.LATE IV.LAV9 IV.LNSS IV.LPEL IV.MA9 IV.MAON
IV.MELA IV.MGAB IV.MIDA IV.MTCE IV.NRCA IV.OFFI IV.PARC
IV.PESA IV.PIEI IV.POFI IV.RDP IV.RMP IV.RNI2 IV.RSM
IV.SACS IV.SAMA IV.TERO IV.TOLF IV.TRIV IV.VVLD
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 5.69e+21 dyne-cm
Mw = 3.77
Z = 13 km
Plane Strike Dip Rake
NP1 344 47 -105
NP2 185 45 -75
Principal Axes:
Axis Value Plunge Azimuth
T 5.69e+21 1 84
N 0.00e+00 11 354
P -5.69e+21 79 180
Moment Tensor: (dyne-cm)
Component Value
Mxx -1.39e+20
Mxy 5.48e+20
Mxz 1.04e+21
Myy 5.63e+21
Myz 9.07e+19
Mzz -5.49e+21
###---########
########---###########
#########--------###########
########-----------###########
#########--------------###########
#########----------------###########
#########------------------###########
##########-------------------###########
#########---------------------#########
##########---------------------######### T
##########----------------------########
##########---------- ---------##########
##########---------- P ---------##########
#########---------- ---------#########
#########----------------------#########
#########---------------------########
########---------------------#######
########-------------------#######
#######------------------#####
#######----------------#####
#####--------------###
###----------#
Global CMT Convention Moment Tensor:
R T P
-5.49e+21 1.04e+21 -9.07e+19
1.04e+21 -1.39e+20 -5.48e+20
-9.07e+19 -5.48e+20 5.63e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090924161457/index.html
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STK = 185
DIP = 45
RAKE = -75
MW = 3.77
HS = 13.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/09/24 16:14:57:0 42.45 13.33 4.1 9.7 Italy
Stations used:
IV.AOI IV.ARVD IV.CAFI IV.CAFR IV.CERA IV.CESX IV.CING
IV.CRE IV.FAGN IV.FDMO IV.FIAM IV.FSSB IV.GIUL IV.GUMA
IV.INTR IV.LATE IV.LAV9 IV.LNSS IV.LPEL IV.MA9 IV.MAON
IV.MELA IV.MGAB IV.MIDA IV.MTCE IV.NRCA IV.OFFI IV.PARC
IV.PESA IV.PIEI IV.POFI IV.RDP IV.RMP IV.RNI2 IV.RSM
IV.SACS IV.SAMA IV.TERO IV.TOLF IV.TRIV IV.VVLD
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 5.69e+21 dyne-cm
Mw = 3.77
Z = 13 km
Plane Strike Dip Rake
NP1 344 47 -105
NP2 185 45 -75
Principal Axes:
Axis Value Plunge Azimuth
T 5.69e+21 1 84
N 0.00e+00 11 354
P -5.69e+21 79 180
Moment Tensor: (dyne-cm)
Component Value
Mxx -1.39e+20
Mxy 5.48e+20
Mxz 1.04e+21
Myy 5.63e+21
Myz 9.07e+19
Mzz -5.49e+21
###---########
########---###########
#########--------###########
########-----------###########
#########--------------###########
#########----------------###########
#########------------------###########
##########-------------------###########
#########---------------------#########
##########---------------------######### T
##########----------------------########
##########---------- ---------##########
##########---------- P ---------##########
#########---------- ---------#########
#########----------------------#########
#########---------------------########
########---------------------#######
########-------------------#######
#######------------------#####
#######----------------#####
#####--------------###
###----------#
Global CMT Convention Moment Tensor:
R T P
-5.49e+21 1.04e+21 -9.07e+19
1.04e+21 -1.39e+20 -5.48e+20
-9.07e+19 -5.48e+20 5.63e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090924161457/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:
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 1.0 260 45 90 3.46 0.3063
WVFGRD96 2.0 80 40 85 3.53 0.2915
WVFGRD96 3.0 15 90 45 3.52 0.2748
WVFGRD96 4.0 215 70 -40 3.52 0.3045
WVFGRD96 5.0 5 75 -75 3.66 0.3333
WVFGRD96 6.0 -5 65 -90 3.69 0.3833
WVFGRD96 7.0 170 30 -95 3.71 0.4345
WVFGRD96 8.0 190 45 -70 3.70 0.4904
WVFGRD96 9.0 190 45 -70 3.72 0.5260
WVFGRD96 10.0 185 45 -75 3.73 0.5519
WVFGRD96 11.0 185 45 -75 3.74 0.5699
WVFGRD96 12.0 185 45 -75 3.76 0.5810
WVFGRD96 13.0 185 45 -75 3.77 0.5857
WVFGRD96 14.0 185 40 -75 3.78 0.5847
WVFGRD96 15.0 185 40 -75 3.82 0.5842
WVFGRD96 16.0 190 40 -70 3.82 0.5757
WVFGRD96 17.0 195 40 -65 3.83 0.5638
WVFGRD96 18.0 195 40 -60 3.84 0.5500
WVFGRD96 19.0 200 40 -55 3.84 0.5340
WVFGRD96 20.0 200 40 -55 3.85 0.5158
WVFGRD96 21.0 195 35 -60 3.86 0.4964
WVFGRD96 22.0 195 35 -60 3.86 0.4749
WVFGRD96 23.0 200 40 -55 3.86 0.4511
WVFGRD96 24.0 200 40 -50 3.86 0.4275
WVFGRD96 25.0 205 45 -45 3.86 0.4037
WVFGRD96 26.0 210 50 -40 3.86 0.3814
WVFGRD96 27.0 210 60 -45 3.86 0.3616
WVFGRD96 28.0 190 70 -60 3.88 0.3492
WVFGRD96 29.0 190 70 -60 3.89 0.3420
The best solution is
WVFGRD96 13.0 185 45 -75 3.77 0.5857
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 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=Thu Sep 24 12:36:42 CDT 2009