2006/04/16 21:15:02 43.96N 11.80E 27 4.1 Italy
USGS Felt map for this earthquake
USGS Felt reports page for Intermountain Western US
SLU Moment Tensor Solution
2006/04/16 21:15:02 43.96N 11.80E 27 4.1 Italy
Best Fitting Double Couple
Mo = 3.39e+22 dyne-cm
Mw = 4.32
Z = 9 km
Plane Strike Dip Rake
NP1 95 70 60
NP2 334 36 144
Principal Axes:
Axis Value Plunge Azimuth
T 3.39e+22 55 327
N 0.00e+00 28 106
P -3.39e+22 19 207
Moment Tensor: (dyne-cm)
Component Value
Mxx -1.60e+22
Mxy -1.73e+22
Mxz 2.29e+22
Myy -2.91e+21
Myz -3.81e+21
Mzz 1.89e+22
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########### #############---------
############ T ###############--------
############# ################--------
#################################-------
##################################--------
-##################################-------
----###############################-------
---------##########################-----##
----------------#################--#####
----------------------------------######
---------------------------------#####
--------------------------------####
------------------------------####
------ ------------------###
----- P -----------------###
-- ----------------#
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Harvard Convention
Moment Tensor:
R T F
1.89e+22 2.29e+22 3.81e+21
2.29e+22 -1.60e+22 1.73e+22
3.81e+21 1.73e+22 -2.91e+21
Details of the solution is found at
http://www.eas.slu.edu/Earthquake_Center/NEW/20050822120208/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 = 95
DIP = 70
RAKE = 60
MW = 4.32
HS = 9
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 0.05 3The results of this grid search from 0.5 to 19 km depth are as follow:
DEPTH STK DIP RAKE MW FIT
WVFGRD96 0.5 260 45 -80 3.86 0.2590
WVFGRD96 1.0 255 45 -85 3.90 0.2676
WVFGRD96 2.0 295 45 90 4.07 0.3116
WVFGRD96 3.0 255 80 15 3.98 0.3234
WVFGRD96 4.0 255 85 20 4.01 0.3315
WVFGRD96 5.0 80 80 40 4.08 0.3397
WVFGRD96 6.0 85 75 50 4.12 0.3630
WVFGRD96 7.0 85 75 50 4.14 0.3873
WVFGRD96 8.0 85 75 55 4.18 0.4120
WVFGRD96 9.0 90 75 60 4.20 0.4370
WVFGRD96 10.0 90 75 55 4.20 0.4594
WVFGRD96 11.0 95 70 60 4.22 0.4806
WVFGRD96 12.0 95 70 60 4.23 0.4986
WVFGRD96 13.0 95 70 60 4.23 0.5136
WVFGRD96 14.0 95 70 60 4.24 0.5256
WVFGRD96 15.0 95 70 60 4.24 0.5353
WVFGRD96 16.0 95 70 55 4.24 0.5429
WVFGRD96 17.0 95 70 55 4.24 0.5492
WVFGRD96 18.0 95 70 55 4.24 0.5536
WVFGRD96 19.0 95 70 55 4.24 0.5559
WVFGRD96 20.0 95 70 55 4.24 0.5567
WVFGRD96 21.0 95 70 60 4.31 0.5738
WVFGRD96 22.0 95 70 60 4.31 0.5747
WVFGRD96 23.0 95 70 60 4.32 0.5747
WVFGRD96 24.0 95 70 55 4.32 0.5732
WVFGRD96 25.0 95 70 55 4.32 0.5719
WVFGRD96 26.0 95 70 55 4.33 0.5697
WVFGRD96 27.0 95 70 55 4.33 0.5658
WVFGRD96 28.0 285 75 -55 4.34 0.5674
WVFGRD96 29.0 285 75 -55 4.35 0.5696
WVFGRD96 30.0 285 70 -55 4.35 0.5701
The best solution is
WVFGRD96 23.0 95 70 60 4.32 0.5747
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 0.05 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 FNVD 293 59 eP_- PZZT 285 78 eP_- BDI 277 97 eP_X MURB 143 97 eP_- VLC 282 115 eP_X SACS 176 124 eP_- ARCI 192 126 iP_D CING 120 130 eP_+ MAON 198 179 eP_- BOB 296 208 eP_+ TOLF 176 211 eP_- FIAM 150 216 eP_X AQU 143 221 eP_X TRI 38 249 eP_X MABI 337 254 eP_X MDI 321 260 eP_+ INTR 141 276 eP_X RNI2 142 316 eP_X FRES 132 322 eP_X MIDA 141 327 eP_X MONC 293 332 eP_X TRIV 136 332 eP_X TUE 326 339 iP_C VAGA 144 346 eP_X BSSO 139 353 eP_X DOI 281 369 eP_X SACR 139 371 eP_X PSB1 140 392 eP_X MOCO 135 398 eP_X BNI 288 425 eP_X CAFE 138 431 eP_X MCRV 141 449 eP_X VULT 135 458 eP_X MRLC 138 468 eP_X
The following stations were not used because of excessive low frequency noise in the deconvolved waveforms: