2009/04/14 20:17:27 42.530 13.288 10.4 4.10 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/04/14 20:17:27:0 42.53 13.29 10.4 4.1 Italy
Stations used:
IV.ARCI IV.ARVD IV.CAFI IV.CAFR IV.CERT IV.CESX IV.FAGN
IV.FDMO IV.FIAM IV.GUAR IV.LPEL IV.MNS IV.MODR IV.MTCE
IV.NRCA IV.OFFI IV.PIEI IV.RDP IV.RMP IV.TERO IV.TRTR
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 6.76e+21 dyne-cm
Mw = 3.82
Z = 9 km
Plane Strike Dip Rake
NP1 308 51 -124
NP2 175 50 -55
Principal Axes:
Axis Value Plunge Azimuth
T 6.76e+21 1 61
N 0.00e+00 26 331
P -6.76e+21 64 152
Moment Tensor: (dyne-cm)
Component Value
Mxx 5.57e+20
Mxy 3.40e+21
Mxz 2.40e+21
Myy 4.90e+21
Myz -1.18e+21
Mzz -5.45e+21
----##########
------################
--------####################
--------######################
#########------##################
#########-----------############## T
##########--------------###########
##########------------------############
##########-------------------###########
###########---------------------##########
###########----------------------#########
###########------------------------#######
###########-------------------------######
###########----------- ----------#####
###########----------- P -----------####
###########---------- -----------###
##########-------------------------#
##########------------------------
#########---------------------
##########------------------
########--------------
#######-------
Global CMT Convention Moment Tensor:
R T P
-5.45e+21 2.40e+21 1.18e+21
2.40e+21 5.57e+20 -3.40e+21
1.18e+21 -3.40e+21 4.90e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090414201727/index.html
|
STK = 175
DIP = 50
RAKE = -55
MW = 3.82
HS = 9.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/04/14 20:17:27:0 42.53 13.29 10.4 4.1 Italy
Stations used:
IV.ARCI IV.ARVD IV.CAFI IV.CAFR IV.CERT IV.CESX IV.FAGN
IV.FDMO IV.FIAM IV.GUAR IV.LPEL IV.MNS IV.MODR IV.MTCE
IV.NRCA IV.OFFI IV.PIEI IV.RDP IV.RMP IV.TERO IV.TRTR
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 6.76e+21 dyne-cm
Mw = 3.82
Z = 9 km
Plane Strike Dip Rake
NP1 308 51 -124
NP2 175 50 -55
Principal Axes:
Axis Value Plunge Azimuth
T 6.76e+21 1 61
N 0.00e+00 26 331
P -6.76e+21 64 152
Moment Tensor: (dyne-cm)
Component Value
Mxx 5.57e+20
Mxy 3.40e+21
Mxz 2.40e+21
Myy 4.90e+21
Myz -1.18e+21
Mzz -5.45e+21
----##########
------################
--------####################
--------######################
#########------##################
#########-----------############## T
##########--------------###########
##########------------------############
##########-------------------###########
###########---------------------##########
###########----------------------#########
###########------------------------#######
###########-------------------------######
###########----------- ----------#####
###########----------- P -----------####
###########---------- -----------###
##########-------------------------#
##########------------------------
#########---------------------
##########------------------
########--------------
#######-------
Global CMT Convention Moment Tensor:
R T P
-5.45e+21 2.40e+21 1.18e+21
2.40e+21 5.57e+20 -3.40e+21
1.18e+21 -3.40e+21 4.90e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090414201727/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 0.5 145 45 -95 3.42 0.2977
WVFGRD96 1.0 170 50 -55 3.40 0.2337
WVFGRD96 2.0 170 50 -60 3.57 0.3151
WVFGRD96 3.0 15 35 -20 3.62 0.3555
WVFGRD96 4.0 15 35 -25 3.65 0.4151
WVFGRD96 5.0 0 40 -45 3.68 0.4546
WVFGRD96 6.0 175 45 -55 3.71 0.4819
WVFGRD96 7.0 180 50 -50 3.73 0.5003
WVFGRD96 8.0 165 45 -70 3.82 0.5293
WVFGRD96 9.0 175 50 -55 3.82 0.5304
WVFGRD96 10.0 180 50 -45 3.82 0.5215
WVFGRD96 11.0 180 55 -45 3.84 0.5110
WVFGRD96 12.0 180 55 -45 3.84 0.4979
WVFGRD96 13.0 185 60 -35 3.85 0.4831
WVFGRD96 14.0 180 60 -40 3.87 0.4696
WVFGRD96 15.0 185 65 -30 3.88 0.4566
WVFGRD96 16.0 185 70 -30 3.89 0.4452
WVFGRD96 17.0 185 70 -30 3.90 0.4349
WVFGRD96 18.0 185 70 -30 3.91 0.4247
WVFGRD96 19.0 185 70 -30 3.92 0.4141
WVFGRD96 20.0 185 70 -30 3.92 0.4027
WVFGRD96 21.0 185 75 -30 3.94 0.3931
WVFGRD96 22.0 185 75 -30 3.94 0.3835
WVFGRD96 23.0 25 60 20 3.93 0.3733
WVFGRD96 24.0 25 60 20 3.93 0.3651
WVFGRD96 25.0 25 60 15 3.93 0.3561
WVFGRD96 26.0 25 55 10 3.94 0.3494
WVFGRD96 27.0 25 55 5 3.94 0.3450
WVFGRD96 28.0 25 50 0 3.95 0.3407
WVFGRD96 29.0 25 50 0 3.96 0.3360
The best solution is
WVFGRD96 9.0 175 50 -55 3.82 0.5304
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 WUS used for the waveform synthetic seismograms and for the surface wave eigenfunctions and dispersion is as follows:
MODEL.01
Model after 8 iterations
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
1.9000 3.4065 2.0089 2.2150 0.302E-02 0.679E-02 0.00 0.00 1.00 1.00
6.1000 5.5445 3.2953 2.6089 0.349E-02 0.784E-02 0.00 0.00 1.00 1.00
13.0000 6.2708 3.7396 2.7812 0.212E-02 0.476E-02 0.00 0.00 1.00 1.00
19.0000 6.4075 3.7680 2.8223 0.111E-02 0.249E-02 0.00 0.00 1.00 1.00
0.0000 7.9000 4.6200 3.2760 0.164E-10 0.370E-10 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=Wed Apr 15 16:32:13 CDT 2009