2009/04/08 04:27:41 42.305 13.467 10.7 3.70 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/04/08 04:27:41:0 42.31 13.47 10.7 3.7 Italy
Stations used:
IV.ASSB IV.CAFR IV.CERA IV.CERT IV.FDMO IV.FIAM IV.FRES
IV.GIUL IV.INTR IV.LATE IV.LNSS IV.MODR IV.MTCE IV.OFFI
IV.POFI IV.RDP IV.RMP IV.RNI2 IV.SACS IV.TERO IV.TOLF
IV.TRTR IV.VAGA IV.VVLD
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 9.55e+21 dyne-cm
Mw = 3.92
Z = 7 km
Plane Strike Dip Rake
NP1 137 73 -108
NP2 5 25 -45
Principal Axes:
Axis Value Plunge Azimuth
T 9.55e+21 25 241
N 0.00e+00 17 143
P -9.55e+21 58 22
Moment Tensor: (dyne-cm)
Component Value
Mxx -4.56e+20
Mxy 2.36e+21
Mxz -5.72e+21
Myy 5.63e+21
Myz -4.86e+21
Mzz -5.17e+21
------------##
-------------------###
------------------------####
#-------------------------####
####--------------------------####
######-------------- ---------####
#######-------------- P ---------#####
##########------------ ----------#####
###########------------------------#####
#############------------------------#####
##############-----------------------#####
################---------------------#####
##################-------------------#####
##################-----------------#####
##### ############---------------#####
#### T ##############------------#####
### #################--------#####
########################-----#####
#########################-####
#######################-----
#################-----
##########----
Global CMT Convention Moment Tensor:
R T P
-5.17e+21 -5.72e+21 4.86e+21
-5.72e+21 -4.56e+20 -2.36e+21
4.86e+21 -2.36e+21 5.63e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090408042741/index.html
|
STK = 5
DIP = 25
RAKE = -45
MW = 3.92
HS = 7.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/04/08 04:27:41:0 42.31 13.47 10.7 3.7 Italy
Stations used:
IV.ASSB IV.CAFR IV.CERA IV.CERT IV.FDMO IV.FIAM IV.FRES
IV.GIUL IV.INTR IV.LATE IV.LNSS IV.MODR IV.MTCE IV.OFFI
IV.POFI IV.RDP IV.RMP IV.RNI2 IV.SACS IV.TERO IV.TOLF
IV.TRTR IV.VAGA IV.VVLD
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 9.55e+21 dyne-cm
Mw = 3.92
Z = 7 km
Plane Strike Dip Rake
NP1 137 73 -108
NP2 5 25 -45
Principal Axes:
Axis Value Plunge Azimuth
T 9.55e+21 25 241
N 0.00e+00 17 143
P -9.55e+21 58 22
Moment Tensor: (dyne-cm)
Component Value
Mxx -4.56e+20
Mxy 2.36e+21
Mxz -5.72e+21
Myy 5.63e+21
Myz -4.86e+21
Mzz -5.17e+21
------------##
-------------------###
------------------------####
#-------------------------####
####--------------------------####
######-------------- ---------####
#######-------------- P ---------#####
##########------------ ----------#####
###########------------------------#####
#############------------------------#####
##############-----------------------#####
################---------------------#####
##################-------------------#####
##################-----------------#####
##### ############---------------#####
#### T ##############------------#####
### #################--------#####
########################-----#####
#########################-####
#######################-----
#################-----
##########----
Global CMT Convention Moment Tensor:
R T P
-5.17e+21 -5.72e+21 4.86e+21
-5.72e+21 -4.56e+20 -2.36e+21
4.86e+21 -2.36e+21 5.63e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090408042741/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 0.5 330 25 85 3.75 0.2890
WVFGRD96 1.0 340 30 105 3.74 0.2636
WVFGRD96 2.0 125 90 -75 3.84 0.2765
WVFGRD96 3.0 305 90 70 3.81 0.3245
WVFGRD96 4.0 15 20 -30 3.80 0.3476
WVFGRD96 5.0 5 20 -40 3.91 0.3668
WVFGRD96 6.0 5 25 -45 3.91 0.3828
WVFGRD96 7.0 5 25 -45 3.92 0.3859
WVFGRD96 8.0 10 30 -40 3.88 0.3762
WVFGRD96 9.0 10 30 -35 3.88 0.3656
WVFGRD96 10.0 10 30 -35 3.88 0.3534
WVFGRD96 11.0 10 30 -35 3.89 0.3398
WVFGRD96 12.0 15 35 -30 3.90 0.3251
WVFGRD96 13.0 15 35 -25 3.90 0.3103
WVFGRD96 14.0 25 35 -15 3.90 0.2961
WVFGRD96 15.0 20 30 -20 3.94 0.2834
WVFGRD96 16.0 25 30 -10 3.95 0.2679
WVFGRD96 17.0 30 30 -5 3.95 0.2535
WVFGRD96 18.0 305 80 65 3.94 0.2424
WVFGRD96 19.0 310 70 65 3.96 0.2341
WVFGRD96 20.0 310 70 65 3.97 0.2295
WVFGRD96 21.0 310 70 65 3.98 0.2260
WVFGRD96 22.0 315 65 65 3.99 0.2232
WVFGRD96 23.0 315 65 65 4.00 0.2214
WVFGRD96 24.0 310 65 60 4.01 0.2207
WVFGRD96 25.0 315 60 65 4.02 0.2202
WVFGRD96 26.0 315 60 65 4.03 0.2209
WVFGRD96 27.0 145 45 80 4.05 0.2270
WVFGRD96 28.0 145 45 80 4.07 0.2296
WVFGRD96 29.0 150 40 85 4.09 0.2295
The best solution is
WVFGRD96 7.0 5 25 -45 3.92 0.3859
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=Mon Apr 20 10:38:59 CDT 2009