2009/04/08 11:35:57 42.355 13.328 10.6 3.50 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/04/08 11:35:57:0 42.35 13.33 10.6 3.5 Italy
Stations used:
IV.AOI IV.ARVD IV.ASSB IV.CERA IV.CERT IV.CESI IV.FDMO
IV.FIAM IV.INTR IV.MGAB IV.MIDA IV.MNS IV.MURB IV.NRCA
IV.OFFI IV.SACS IV.TERO IV.TRTR IV.VAGA
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 1.33e+21 dyne-cm
Mw = 3.35
Z = 7 km
Plane Strike Dip Rake
NP1 114 78 -144
NP2 15 55 -15
Principal Axes:
Axis Value Plunge Azimuth
T 1.33e+21 15 240
N 0.00e+00 52 130
P -1.33e+21 34 340
Moment Tensor: (dyne-cm)
Component Value
Mxx -5.06e+20
Mxy 8.33e+20
Mxz -7.44e+20
Myy 8.30e+20
Myz -7.72e+19
Mzz -3.24e+20
-------------#
------------------####
-------- -----------######
--------- P ------------######
----------- ------------########
---------------------------#########
-----------------------------#########
###---------------------------##########
#####-------------------------##########
#########---------------------############
############------------------############
################--------------############
####################---------#############
#######################-----############
### #####################-############
## T ####################------------#
# ###################-------------
#####################-------------
##################------------
###############-------------
##########------------
###-----------
Global CMT Convention Moment Tensor:
R T P
-3.24e+20 -7.44e+20 7.72e+19
-7.44e+20 -5.06e+20 -8.33e+20
7.72e+19 -8.33e+20 8.30e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090408113557/index.html
|
STK = 15
DIP = 55
RAKE = -15
MW = 3.35
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 11:35:57:0 42.35 13.33 10.6 3.5 Italy
Stations used:
IV.AOI IV.ARVD IV.ASSB IV.CERA IV.CERT IV.CESI IV.FDMO
IV.FIAM IV.INTR IV.MGAB IV.MIDA IV.MNS IV.MURB IV.NRCA
IV.OFFI IV.SACS IV.TERO IV.TRTR IV.VAGA
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 1.33e+21 dyne-cm
Mw = 3.35
Z = 7 km
Plane Strike Dip Rake
NP1 114 78 -144
NP2 15 55 -15
Principal Axes:
Axis Value Plunge Azimuth
T 1.33e+21 15 240
N 0.00e+00 52 130
P -1.33e+21 34 340
Moment Tensor: (dyne-cm)
Component Value
Mxx -5.06e+20
Mxy 8.33e+20
Mxz -7.44e+20
Myy 8.30e+20
Myz -7.72e+19
Mzz -3.24e+20
-------------#
------------------####
-------- -----------######
--------- P ------------######
----------- ------------########
---------------------------#########
-----------------------------#########
###---------------------------##########
#####-------------------------##########
#########---------------------############
############------------------############
################--------------############
####################---------#############
#######################-----############
### #####################-############
## T ####################------------#
# ###################-------------
#####################-------------
##################------------
###############-------------
##########------------
###-----------
Global CMT Convention Moment Tensor:
R T P
-3.24e+20 -7.44e+20 7.72e+19
-7.44e+20 -5.06e+20 -8.33e+20
7.72e+19 -8.33e+20 8.30e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090408113557/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 10 70 -25 3.07 0.3185
WVFGRD96 1.0 10 70 -20 3.09 0.3248
WVFGRD96 2.0 15 45 -15 3.21 0.3741
WVFGRD96 3.0 10 45 -25 3.24 0.4224
WVFGRD96 4.0 15 55 -20 3.25 0.4480
WVFGRD96 5.0 10 45 -30 3.34 0.4883
WVFGRD96 6.0 10 50 -25 3.34 0.5033
WVFGRD96 7.0 15 55 -15 3.35 0.5077
WVFGRD96 8.0 15 60 -10 3.34 0.5006
WVFGRD96 9.0 15 60 -10 3.35 0.4925
WVFGRD96 10.0 15 65 -10 3.36 0.4820
WVFGRD96 11.0 15 65 -10 3.37 0.4683
WVFGRD96 12.0 15 65 -10 3.38 0.4520
WVFGRD96 13.0 15 70 -10 3.39 0.4360
WVFGRD96 14.0 15 70 -10 3.40 0.4212
WVFGRD96 15.0 35 50 10 3.42 0.4088
WVFGRD96 16.0 35 50 10 3.43 0.4008
WVFGRD96 17.0 35 50 10 3.44 0.3920
WVFGRD96 18.0 35 50 10 3.44 0.3826
WVFGRD96 19.0 35 50 10 3.45 0.3728
WVFGRD96 20.0 10 70 -20 3.46 0.3633
WVFGRD96 21.0 10 70 -20 3.47 0.3579
WVFGRD96 22.0 10 70 -15 3.48 0.3543
WVFGRD96 23.0 10 70 -15 3.49 0.3521
WVFGRD96 24.0 10 75 -15 3.51 0.3515
WVFGRD96 25.0 10 70 -15 3.51 0.3506
WVFGRD96 26.0 10 70 -15 3.53 0.3489
WVFGRD96 27.0 10 70 -15 3.54 0.3472
WVFGRD96 28.0 10 75 -15 3.55 0.3446
WVFGRD96 29.0 10 75 -10 3.57 0.3436
The best solution is
WVFGRD96 7.0 15 55 -15 3.35 0.5077
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 14:31:18 CDT 2009