2009/04/09 13:19:33 42.338 13.259 10.0 3.60 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/04/09 13:19:33:0 42.34 13.26 10.0 3.6 Italy
Stations used:
IV.AOI IV.ASSB IV.BSSO IV.CAFR IV.CERA IV.CERT IV.CESI
IV.CESX IV.CING IV.FAGN IV.FDMO IV.FIAM IV.GIUL IV.GUAR
IV.INTR IV.LNSS IV.LPEL IV.MGAB IV.MIDA IV.MNS IV.MODR
IV.MTCE IV.MURB IV.NRCA IV.OFFI IV.POFI IV.RDP IV.RNI2
IV.SACS IV.SGG IV.TERO IV.TRIV IV.TRTR IV.VVLD MN.AQU
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 6.10e+21 dyne-cm
Mw = 3.79
Z = 9 km
Plane Strike Dip Rake
NP1 330 50 -65
NP2 114 46 -117
Principal Axes:
Axis Value Plunge Azimuth
T 6.10e+21 2 43
N 0.00e+00 19 133
P -6.10e+21 71 307
Moment Tensor: (dyne-cm)
Component Value
Mxx 3.07e+21
Mxy 3.34e+21
Mxz -9.54e+20
Myy 2.37e+21
Myz 1.66e+21
Mzz -5.44e+21
##############
----##################
------------############## T
----------------###########
--------------------##############
-----------------------#############
-------------------------#############
#---------------------------############
##------------- -----------###########
###------------- P ------------###########
####------------ -------------##########
#####---------------------------##########
#######--------------------------#########
#######-------------------------########
##########----------------------########
###########---------------------######
##############-----------------###--
###################---------#-----
###########################---
#########################---
######################
##############
Global CMT Convention Moment Tensor:
R T P
-5.44e+21 -9.54e+20 -1.66e+21
-9.54e+20 3.07e+21 -3.34e+21
-1.66e+21 -3.34e+21 2.37e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090409131933/index.html
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STK = 330
DIP = 50
RAKE = -65
MW = 3.79
HS = 9.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/04/09 13:19:33:0 42.34 13.26 10.0 3.6 Italy
Stations used:
IV.AOI IV.ASSB IV.BSSO IV.CAFR IV.CERA IV.CERT IV.CESI
IV.CESX IV.CING IV.FAGN IV.FDMO IV.FIAM IV.GIUL IV.GUAR
IV.INTR IV.LNSS IV.LPEL IV.MGAB IV.MIDA IV.MNS IV.MODR
IV.MTCE IV.MURB IV.NRCA IV.OFFI IV.POFI IV.RDP IV.RNI2
IV.SACS IV.SGG IV.TERO IV.TRIV IV.TRTR IV.VVLD MN.AQU
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 6.10e+21 dyne-cm
Mw = 3.79
Z = 9 km
Plane Strike Dip Rake
NP1 330 50 -65
NP2 114 46 -117
Principal Axes:
Axis Value Plunge Azimuth
T 6.10e+21 2 43
N 0.00e+00 19 133
P -6.10e+21 71 307
Moment Tensor: (dyne-cm)
Component Value
Mxx 3.07e+21
Mxy 3.34e+21
Mxz -9.54e+20
Myy 2.37e+21
Myz 1.66e+21
Mzz -5.44e+21
##############
----##################
------------############## T
----------------###########
--------------------##############
-----------------------#############
-------------------------#############
#---------------------------############
##------------- -----------###########
###------------- P ------------###########
####------------ -------------##########
#####---------------------------##########
#######--------------------------#########
#######-------------------------########
##########----------------------########
###########---------------------######
##############-----------------###--
###################---------#-----
###########################---
#########################---
######################
##############
Global CMT Convention Moment Tensor:
R T P
-5.44e+21 -9.54e+20 -1.66e+21
-9.54e+20 3.07e+21 -3.34e+21
-1.66e+21 -3.34e+21 2.37e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090409131933/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 0.5 310 50 -90 3.52 0.2705
WVFGRD96 1.0 125 45 -95 3.55 0.2519
WVFGRD96 2.0 345 45 -30 3.58 0.2464
WVFGRD96 3.0 350 35 -20 3.62 0.2746
WVFGRD96 4.0 345 40 -30 3.64 0.3102
WVFGRD96 5.0 340 35 -40 3.74 0.3414
WVFGRD96 6.0 330 40 -60 3.79 0.3968
WVFGRD96 7.0 325 45 -70 3.81 0.4464
WVFGRD96 8.0 325 45 -70 3.79 0.4681
WVFGRD96 9.0 330 50 -65 3.79 0.4720
WVFGRD96 10.0 335 50 -60 3.79 0.4670
WVFGRD96 11.0 335 50 -60 3.80 0.4565
WVFGRD96 12.0 335 50 -60 3.80 0.4425
WVFGRD96 13.0 340 50 -50 3.81 0.4286
WVFGRD96 14.0 345 50 -45 3.81 0.4137
WVFGRD96 15.0 345 50 -45 3.85 0.4086
WVFGRD96 16.0 345 50 -45 3.85 0.3957
WVFGRD96 17.0 345 55 -45 3.86 0.3821
WVFGRD96 18.0 345 60 -45 3.87 0.3693
WVFGRD96 19.0 345 60 -45 3.87 0.3581
WVFGRD96 20.0 345 60 -45 3.88 0.3473
WVFGRD96 21.0 345 55 -45 3.89 0.3377
WVFGRD96 22.0 345 55 -40 3.89 0.3299
WVFGRD96 23.0 345 55 -45 3.90 0.3231
WVFGRD96 24.0 345 55 -45 3.91 0.3162
WVFGRD96 25.0 350 60 -40 3.91 0.3085
WVFGRD96 26.0 350 60 -40 3.92 0.3011
WVFGRD96 27.0 345 55 -35 3.93 0.2937
WVFGRD96 28.0 345 55 -40 3.93 0.2857
WVFGRD96 29.0 345 55 -40 3.94 0.2756
The best solution is
WVFGRD96 9.0 330 50 -65 3.79 0.4720
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=Mon Apr 20 10:42:20 CDT 2009