2009/04/06 04:08:45 42.376 13.356 10.0 3.0 ITALY
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/04/06 04:08:45:0 42.38 13.36 10.0 3.0 ITALY
Stations used:
IV.CERT IV.CESI IV.FDMO IV.LPEL IV.MTCE IV.OFFI
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 1.24e+21 dyne-cm
Mw = 3.33
Z = 7 km
Plane Strike Dip Rake
NP1 138 68 -125
NP2 20 40 -35
Principal Axes:
Axis Value Plunge Azimuth
T 1.24e+21 16 253
N 0.00e+00 32 152
P -1.24e+21 53 6
Moment Tensor: (dyne-cm)
Component Value
Mxx -3.39e+20
Mxy 2.76e+20
Mxz -6.91e+20
Myy 1.04e+21
Myz -3.84e+20
Mzz -7.03e+20
--------------
--------------------##
------------------------####
#-------------------------####
####-------------------------#####
#####------------ -----------#####
#######----------- P -----------######
#########---------- -----------#######
##########-----------------------#######
############----------------------########
#############---------------------########
###############-------------------########
### ##########-----------------#########
## T ############---------------########
## ##############------------#########
####################---------#########
#####################------#########
#######################-##########
####################----######
#################-----------
###########-----------
#-------------
Global CMT Convention Moment Tensor:
R T P
-7.03e+20 -6.91e+20 3.84e+20
-6.91e+20 -3.39e+20 -2.76e+20
3.84e+20 -2.76e+20 1.04e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090406040845/index.html
|
STK = 20
DIP = 40
RAKE = -35
MW = 3.33
HS = 7.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/04/06 04:08:45:0 42.38 13.36 10.0 3.0 ITALY
Stations used:
IV.CERT IV.CESI IV.FDMO IV.LPEL IV.MTCE IV.OFFI
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 1.24e+21 dyne-cm
Mw = 3.33
Z = 7 km
Plane Strike Dip Rake
NP1 138 68 -125
NP2 20 40 -35
Principal Axes:
Axis Value Plunge Azimuth
T 1.24e+21 16 253
N 0.00e+00 32 152
P -1.24e+21 53 6
Moment Tensor: (dyne-cm)
Component Value
Mxx -3.39e+20
Mxy 2.76e+20
Mxz -6.91e+20
Myy 1.04e+21
Myz -3.84e+20
Mzz -7.03e+20
--------------
--------------------##
------------------------####
#-------------------------####
####-------------------------#####
#####------------ -----------#####
#######----------- P -----------######
#########---------- -----------#######
##########-----------------------#######
############----------------------########
#############---------------------########
###############-------------------########
### ##########-----------------#########
## T ############---------------########
## ##############------------#########
####################---------#########
#####################------#########
#######################-##########
####################----######
#################-----------
###########-----------
#-------------
Global CMT Convention Moment Tensor:
R T P
-7.03e+20 -6.91e+20 3.84e+20
-6.91e+20 -3.39e+20 -2.76e+20
3.84e+20 -2.76e+20 1.04e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090406040845/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 0.5 245 45 15 3.15 0.2883
WVFGRD96 1.0 245 55 25 3.15 0.2957
WVFGRD96 2.0 250 50 35 3.25 0.3355
WVFGRD96 3.0 40 40 -10 3.23 0.3385
WVFGRD96 4.0 25 60 20 3.26 0.3614
WVFGRD96 5.0 20 35 -40 3.33 0.3893
WVFGRD96 6.0 15 35 -45 3.34 0.4049
WVFGRD96 7.0 20 40 -35 3.33 0.4067
WVFGRD96 8.0 25 45 -25 3.29 0.3934
WVFGRD96 9.0 30 50 -20 3.31 0.3892
WVFGRD96 10.0 25 50 -20 3.32 0.3837
WVFGRD96 11.0 25 50 -20 3.33 0.3768
WVFGRD96 12.0 30 50 -15 3.34 0.3692
WVFGRD96 13.0 30 50 -15 3.35 0.3620
WVFGRD96 14.0 30 50 -15 3.36 0.3525
WVFGRD96 15.0 30 45 -15 3.39 0.3456
WVFGRD96 16.0 30 50 -15 3.41 0.3357
WVFGRD96 17.0 30 50 -15 3.42 0.3272
WVFGRD96 18.0 30 50 -15 3.43 0.3169
WVFGRD96 19.0 240 60 5 3.50 0.3219
WVFGRD96 20.0 240 65 0 3.53 0.3278
WVFGRD96 21.0 240 65 0 3.55 0.3306
WVFGRD96 22.0 240 65 0 3.56 0.3314
WVFGRD96 23.0 240 70 -5 3.58 0.3306
WVFGRD96 24.0 245 70 -5 3.61 0.3316
WVFGRD96 25.0 245 75 -5 3.63 0.3354
WVFGRD96 26.0 245 75 -5 3.64 0.3386
WVFGRD96 27.0 245 80 -10 3.66 0.3387
WVFGRD96 28.0 245 80 -10 3.68 0.3377
WVFGRD96 29.0 245 80 -10 3.70 0.3333
The best solution is
WVFGRD96 7.0 20 40 -35 3.33 0.4067
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 componnet 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 Jan 22 02:16:04 UTC 2001