Page 17 - Visini_de Nardis_Lavecchia_2010

Int J Earth Sci (Geol Rundsch) (2010) 99 (Suppl 1):S243–S264 S259

Table 4 Components of the strain rate and velocity tensors for the ABT, SBT and STC seismotectonic provinces (grey areas in Fig. 5)
-8
-8
-8
-8
-8
-8
Source _ e(11) (e /year) _ e(12) (e /year) _ e(13) (e /year) _ e(22) (e /year) _ e(23) (e /year) _ e(33) (e /year)
Components of the strain tensors
ABT-P 0.01 ± 0.00 -0.01 ± 0.01 -0.05 ± 0.02 -0.20 ± 0.07 -0.06 ± 0.02 0.19 ± 0.07
ABT-W 0.02 ± 0.01 -0.03 ± 0.01 -0.11 ± 0.04 -0.40 ± 0.20 -0.11 ± 0.04 0.38 ± 0.14
SBT-P -0.07 ± 0.03 0.00 ± 0.00 -0.01 ± 0.01 0.01 ± 0.01 0.01 ± 0.01 0.07 ± 0.03
SBT-W -0.15 ± 0.06 0.01 ± 0.01 -0.03 ± 0.01 0.05 ± 0.02 0.03 ± 0.01 0.14 ± 0.06
STC -0.09 ± 0.06 0.12 ± 0.08 -0.07 ± 0.05 -0.03 ± 0.02 -0.05 ± 0.04 0.11 ± 0.08
Source U(11) (mm/year) U(12) (mm/year) U(13) (mm/year) U(22) (mm/year) U(23) (mm/year) U(33) (mm/year)
Components of the velocity tensors
ABT-P 0.03 ± 0.01 -0.02 ± 0.01 -0.03 ± 0.01 -0.12 ± 0.05 -0.03 ± 0.01 0.05 ± 0.02
ABT-W 0.06 ± 0.02 -0.03 ± 0.01 -0.03 ± 0.01 -0.24 ± 0.09 -0.03 ± 0.01 0.05 ± 0.02
SBT-P -0.04 ± 0.02 -0.00 ± 0.00 -0.00 ± 0.00 0.01 ± 0.01 0.01 ± 0.01 0.02 ± 0.01
SBT-W -0.09 ± 0.04 -0.01 ± 0.00 -0.01 ± 0.01 0.01 ± 0.01 0.01 ± 0.01 0.02 ± 0.01
STC -0.04 ± 0.03 0.12 ± 0.08 -0.03 ± 0.02 -0.07 ± 0.05 -0.02 ± 0.01 0.02 ± 0.01

Positive and negative values indicate compression and tension, respectively
ABT-P Adriatic Basal Thrust-parallelepiped volume, ABT-W Adriatic Basal Thrust-wedge-shaped volume, SBT-P Sicilian Basal Thrust-paral-
lelepiped volume, SBT-W Sicilian Basal Thrust-wedge-shaped volume, STC Southern Tyrrhenian Compressional-parallelepiped volume

seismotectonic province. The obtained results bring with polygons that spans peninsular Italy and Sicily, nor adopted
them the uncertainty and the errors associated with the seismotectonic boundaries only derived from the spatial
input data and especially with: distribution and the kinematics of the seismicity, but we
have adopted province boundaries which represent the
1. catalogue completeness and quality,
surface projection of 3D homogeneous kinematic seismo-
2. focal mechanism dataset,
genic volumes defined on the basis of integrated analysis of
3. attitude, size and shape of the seismogenic volume.
geological, geophysical and seismological constraints
Uncertainties in the catalogue completeness, as well as (Lavecchia et al. 2007a, b).
in the reliability of the magnitude estimation, are directly Any significant variation in the assumption of the sur-
involved in the magnitude–frequency distributions. For this face geometry, average thickness and attitude of the
reason, in the estimation of the Gutenberg–Richter seismogenic volume may strongly influence the final
computational result. We have not considered any variation
parameters, we have considered only earthquakes with M w
C4.5 which occurred within the time interval of catalogue in the geometry of the surface boundaries, as this would
completeness for classes of magnitude (Table 3). This has also have implied a variation of the earthquakes associated
restricted our time of observation to the last 400 years for with the province. The influence of the average seismo-
earthquakes with M w C5.5. A quantitative analysis of the genic thickness may be interesting to consider. Let us
range of fluctuation of the parameters of the G–R slope and suppose we would not have assumed for the ABT and the
of the values of magnitude has been performed with a SBT provinces a wedge-shaped volume deepening from the
Monte Carlo method. With such a method, all the possible surface to 25 km depth, with a consequent average thick-
random errors of the model parameters are considered by ness of 12.5 km, but we had considered a parallelepiped
means of a generator of Gaussian noise type. On the basis with an overall homogeneous thickness of 25 km, the final
of this error analysis, we consider it reasonable to assume a results in terms of maximum velocity rate would have a
conservative 30% uncertainty in the estimates of the decrease of 50%. It is interesting to observe also that the
summed moment tensor. Other limits in the obtained average strike assumed for the seismotectonic province
results may be found in the calculation of the moment plays an important role. Variations of about 20° imply

tensor F ij ; which is linked to the assumption for each variation of about 50% in the maximum velocity rate.
province of an average focal mechanism. In spite of the uncertainties of the input data, the
The last, but not least, uncertainty derives from the obtained results show that in all three analysed seismo-
adopted shape, size and attitude of the provinces’ seismo- tectonic provinces, the deformation is of the reverse-type,
genic volume. In order to reduce this problem as much as with prevailing sub-horizontal contractional component
possible, we have neither used a subdivision in large (k 1 ), a very subordinate sub-horizontal extensional

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