2009/07/03 11:03:07 42.409 13.387 8.8 4.10 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/07/03 11:03:07:0 42.41 13.39 8.8 4.1 Italy
Stations used:
IV.ASSB IV.BSSO IV.CAFI IV.CERA IV.CERT IV.CESI IV.CESX
IV.CING IV.FIAM IV.FSSB IV.GUAR IV.GUMA IV.INTR IV.LNSS
IV.LPEL IV.MGAB IV.MIDA IV.MNS IV.MODR IV.MTCE IV.OFFI
IV.PIEI IV.RDP IV.RMP IV.RNI2 IV.VAGA IV.VVLD MN.AQU
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 4.17e+21 dyne-cm
Mw = 3.68
Z = 2 km
Plane Strike Dip Rake
NP1 310 55 -70
NP2 98 40 -116
Principal Axes:
Axis Value Plunge Azimuth
T 4.17e+21 8 26
N 0.00e+00 16 118
P -4.17e+21 72 271
Moment Tensor: (dyne-cm)
Component Value
Mxx 3.31e+21
Mxy 1.61e+21
Mxz 5.01e+20
Myy 3.71e+20
Myz 1.49e+21
Mzz -3.68e+21
##############
################## T #
##################### ####
##############################
--------------####################
-------------------#################
-----------------------###############
--------------------------##############
----------------------------############
--------------- -------------###########
#-------------- P --------------##########
##------------- ---------------#########
###-------------------------------########
###-------------------------------#####-
#####------------------------------###--
#######-------------------------------
#########---------------------####--
#############-----------#########-
##############################
############################
######################
##############
Global CMT Convention Moment Tensor:
R T P
-3.68e+21 5.01e+20 -1.49e+21
5.01e+20 3.31e+21 -1.61e+21
-1.49e+21 -1.61e+21 3.71e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090703110307/index.html
|
STK = 310
DIP = 55
RAKE = -70
MW = 3.68
HS = 2.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/07/03 11:03:07:0 42.41 13.39 8.8 4.1 Italy
Stations used:
IV.ASSB IV.BSSO IV.CAFI IV.CERA IV.CERT IV.CESI IV.CESX
IV.CING IV.FIAM IV.FSSB IV.GUAR IV.GUMA IV.INTR IV.LNSS
IV.LPEL IV.MGAB IV.MIDA IV.MNS IV.MODR IV.MTCE IV.OFFI
IV.PIEI IV.RDP IV.RMP IV.RNI2 IV.VAGA IV.VVLD MN.AQU
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 4.17e+21 dyne-cm
Mw = 3.68
Z = 2 km
Plane Strike Dip Rake
NP1 310 55 -70
NP2 98 40 -116
Principal Axes:
Axis Value Plunge Azimuth
T 4.17e+21 8 26
N 0.00e+00 16 118
P -4.17e+21 72 271
Moment Tensor: (dyne-cm)
Component Value
Mxx 3.31e+21
Mxy 1.61e+21
Mxz 5.01e+20
Myy 3.71e+20
Myz 1.49e+21
Mzz -3.68e+21
##############
################## T #
##################### ####
##############################
--------------####################
-------------------#################
-----------------------###############
--------------------------##############
----------------------------############
--------------- -------------###########
#-------------- P --------------##########
##------------- ---------------#########
###-------------------------------########
###-------------------------------#####-
#####------------------------------###--
#######-------------------------------
#########---------------------####--
#############-----------#########-
##############################
############################
######################
##############
Global CMT Convention Moment Tensor:
R T P
-3.68e+21 5.01e+20 -1.49e+21
5.01e+20 3.31e+21 -1.61e+21
-1.49e+21 -1.61e+21 3.71e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090703110307/index.html
|
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.
|
|
|
|
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 0.5 320 75 -65 3.62 0.3609
WVFGRD96 1.0 315 60 -60 3.59 0.3953
WVFGRD96 2.0 310 55 -70 3.68 0.4425
WVFGRD96 3.0 305 50 -70 3.70 0.4290
WVFGRD96 4.0 325 60 -40 3.65 0.3702
WVFGRD96 5.0 320 60 -50 3.72 0.3563
WVFGRD96 6.0 340 65 35 3.70 0.3391
WVFGRD96 7.0 340 70 40 3.72 0.3341
WVFGRD96 8.0 340 70 30 3.71 0.3319
WVFGRD96 9.0 335 75 30 3.71 0.3239
WVFGRD96 10.0 335 75 30 3.72 0.3156
WVFGRD96 11.0 145 85 -45 3.73 0.3079
WVFGRD96 12.0 145 85 -45 3.74 0.3031
WVFGRD96 13.0 145 80 -45 3.75 0.2987
WVFGRD96 14.0 145 80 -45 3.76 0.2934
WVFGRD96 15.0 145 80 -50 3.80 0.2896
WVFGRD96 16.0 145 80 -50 3.81 0.2846
WVFGRD96 17.0 140 75 -50 3.81 0.2801
WVFGRD96 18.0 140 75 -50 3.82 0.2765
WVFGRD96 19.0 140 75 -50 3.83 0.2727
WVFGRD96 20.0 140 75 -50 3.84 0.2687
WVFGRD96 21.0 140 75 -50 3.85 0.2651
WVFGRD96 22.0 140 70 -50 3.86 0.2634
WVFGRD96 23.0 140 70 -50 3.86 0.2621
WVFGRD96 24.0 140 70 -50 3.87 0.2604
WVFGRD96 25.0 320 75 -50 3.89 0.2632
WVFGRD96 26.0 320 75 -50 3.90 0.2632
WVFGRD96 27.0 320 75 -50 3.91 0.2621
WVFGRD96 28.0 320 75 -50 3.92 0.2610
WVFGRD96 29.0 320 75 -50 3.93 0.2588
The best solution is
WVFGRD96 2.0 310 55 -70 3.68 0.4425
The mechanism correspond to the best fit is
|
|
|
The best fit as a function of depth is given in the following figure:
|
|
|
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
|
|
|
|
| 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=Fri Jul 3 07:11:15 CDT 2009