2006/04/17 02:44:05 39.57N 17.14E 10 4.3 Italy
USGS Felt map for this earthquake
USGS Felt reports page for Intermountain Western US
SLU Moment Tensor Solution
2006/04/17 02:44:05 39.57N 17.14E 10 4.3 Italy
Best Fitting Double Couple
Mo = 1.72e+23 dyne-cm
Mw = 4.79
Z = 30 km
Plane Strike Dip Rake
NP1 34 76 154
NP2 130 65 15
Principal Axes:
Axis Value Plunge Azimuth
T 1.72e+23 28 350
N 0.00e+00 61 188
P -1.72e+23 8 84
Moment Tensor: (dyne-cm)
Component Value
Mxx 1.28e+23
Mxy -4.29e+22
Mxz 6.70e+22
Myy -1.62e+23
Myz -3.54e+22
Mzz 3.41e+22
##############
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########## T ############---
########### ############----
-##########################-------
---########################---------
-----#######################----------
------######################------------
-------####################-----------
----------#################------------ P
-----------###############-------------
-------------############-----------------
---------------########-------------------
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--------######################
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Harvard Convention
Moment Tensor:
R T F
3.41e+22 6.70e+22 3.54e+22
6.70e+22 1.28e+23 4.29e+22
3.54e+22 4.29e+22 -1.62e+23
Details of the solution is found at
http://www.eas.slu.edu/Earthquake_Center/NEW/20060417024405/index.html
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The focal mechanism was determined using broadband seismic waveforms. The location of the event and the station distribution are given in Figure 1.
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STK = 130
DIP = 65
RAKE = 15
MW = 4.79
HS = 30
The solution given here is from waveform inversion of regional vaeforms from the INGV digital seismic stations.
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 3 lp c 0.04 3The results of this grid search from 0.5 to 19 km depth are as follow:
DEPTH STK DIP RAKE MW FIT
WVFGRD96 0.5 120 35 10 4.46 0.0556
WVFGRD96 1.0 120 55 15 4.39 0.0600
WVFGRD96 2.0 120 50 15 4.48 0.0738
WVFGRD96 3.0 110 55 -5 4.49 0.0806
WVFGRD96 4.0 110 55 -5 4.52 0.0875
WVFGRD96 5.0 110 60 -10 4.54 0.0948
WVFGRD96 6.0 110 55 -10 4.57 0.1007
WVFGRD96 7.0 110 55 -15 4.59 0.1079
WVFGRD96 8.0 110 55 -15 4.62 0.1132
WVFGRD96 9.0 110 55 -15 4.63 0.1181
WVFGRD96 10.0 110 55 -20 4.64 0.1220
WVFGRD96 11.0 110 55 -20 4.65 0.1256
WVFGRD96 12.0 110 55 -20 4.66 0.1283
WVFGRD96 13.0 110 55 -20 4.67 0.1312
WVFGRD96 14.0 115 60 -15 4.66 0.1342
WVFGRD96 15.0 115 60 -10 4.67 0.1365
WVFGRD96 16.0 115 60 -10 4.68 0.1392
WVFGRD96 17.0 115 60 -10 4.69 0.1408
WVFGRD96 18.0 115 65 -10 4.69 0.1428
WVFGRD96 19.0 120 65 -10 4.69 0.1454
WVFGRD96 20.0 120 65 -10 4.70 0.1477
WVFGRD96 21.0 120 65 -10 4.73 0.1493
WVFGRD96 22.0 120 65 -10 4.73 0.1500
WVFGRD96 23.0 120 65 -10 4.74 0.1512
WVFGRD96 24.0 120 65 -10 4.75 0.1521
WVFGRD96 25.0 120 65 -10 4.75 0.1521
WVFGRD96 26.0 120 65 -5 4.76 0.1527
WVFGRD96 27.0 120 65 -5 4.77 0.1531
WVFGRD96 28.0 130 65 15 4.77 0.1531
WVFGRD96 29.0 130 65 15 4.78 0.1538
WVFGRD96 30.0 130 65 15 4.79 0.1542
The best solution is
WVFGRD96 30.0 130 65 15 4.79 0.1542
The mechanism correspond to the best fit is
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The best fit as a function of depth is given in the following figure:
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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 3 lp c 0.04 3
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| 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 P-wave first motion data for focal mechanism studies are as follow:
Sta Az(deg) Dist(km) First motion TIP 217 54 iP_C CUC 293 123 eP_+ NOCI 357 136 iP_C AMUR 343 155 iP_C CEL 217 181 eP_+ MRLC 314 193 iP_C VULT 320 201 iP_C MCRV 309 215 iP_C SNAL 313 223 eP_X CAFE 316 229 iP_C MOCO 321 261 eP_X PSB1 314 270 iP_C SACR 315 290 iP_C TIR 49 304 eP_X BSSO 316 308 iP_C VAGA 311 320 eP_+ TRIV 319 328 iP_C MIDA 314 336 iP_C FRES 323 339 iP_C RNI2 314 346 iP_C INTR 316 385 iP_C CLTB 238 407 eP_X CERT 308 439 iP_C AQU 316 441 iP_C TERO 320 451 iP_C FIAM 313 452 iP_C WDD 210 471 eP_X
The follwoing stations were not used because of excessive low frequency noise in the deconvolved waveforms: AMUR, GIUL, RNI2, SNAL, TRIV