GNGTS 2014 - Atti del 33° Convegno Nazionale

can be reasonably assumed as equal to the sliding velocity of the two sides of a fault during an earthquake, V = 1 m/s – 10 m/s. Considering that the Coriolis force is F Cor =2ρωV Nw/m 3 , in the case of 1.0-10.0 cm/y its value is (Ricard, 2007) F Cor = 3.0 · 10 –5 · 6.34 · 10 –10 � 2.0 · 10 –13 – 2.0 · 10 –14 Nw/m 3 . But I can compute that in the case of impulsive velocities of V = 1 m/s –10 m/s F Cor = 3.0 · 10 –5 · 1.0 � 3.0 · 10 –5 Nw/m 3 , which is 9 order of magnitude greater than in the case of the convective slow laminar flow. Then, it cannot be excluded the possibility of a deflection of the vertical sudden flows. A comparison with the centrifugal force F Cen is also useful: F Cen = ω 2 · L � 10–10 · 10 5 = 10–5 Nw/m 3 , a value in the same order of magnitude of the Coriolis force. The centrifugal force is little but is able to deform the Earth’s shape to an oblate ellipsoid, and this is additionally in favor of the possibility for the Coriolis force to deform the path of the impulsive rising of mantle material. Obviously we cannot expect that the surfaceward motion ever occurs with an impulsive mechanism, but – in the impossibility to know the percent of the path performed in slow or impulsive way – a not negligible contribution of impulsive risings must be assumed. Evidence and conclusion. It is possible to show that changing the assumptions implicit in the adopted geodynamics theory, or in other words, by adopting a different theory of global geodynamics, the role of the fictitious inertial forces can become substantial. In a different framework in which sudden extrusions of mantle materials occur, Coriolis effect value can rise of several magnitude orders, becoming the main cause of the east-west asymmetry of the Wadati-Benioff zones, which might be ascribed entirely to internal causes of the planet (its rotation) and not to external causes (influence of other celestial bodies). Evidence that the subductive dynamics on the Wadati-Benioff zone (WBZ) is invalid are coming from coseismic phenomena of the recent great and shallow earthquakes [Sumatran quake: Han et al. (2006) and Scalera (2007b); and Honshu quake: Han et al. (2011), among others]. The great Sumatra earthquake has caused a sudden displacement of the instantaneous rotation pole of the Earth (Bianco, 2005). Scalera (2007b, 2012) has evidenced that the rotation axis moved following the meridian of the epicenter, going nearly 3milliarcsec (≈ 10.0 cm) farther from the epicenter. Rational mechanics rules (Schiaparelli, 1891) make clear that additional mass has been emplaced in the earthquake zone (Scalera, 2007b), following a mechanism of extrusion. The data of the GRACE satellites (Han et al. , 2006) show variations of surface gravity of -15 μGal east of the Sunda trench, and a symmetrical anomaly of +15 μGal west of the trench. These anomalies does not fit a fault dislocation without a substantial lateral and vertical expansion of the oceanic crust. Their suggestion of local expansion supports the class of models proposed in this paper. The great earthquake of Honshu Tohoku (March 11, 2011; Mw=9.1) has produced similar effects. Instead of a coseismic displacement of the instantaneous rotation pole of 14 cm toward 135°E as forecasted by Gross (see Buis comment, 2012) using the Dahlen (1971) dislocation model, a tendency of a little displacement toward an opposite direction (away from the Honshu hypocentral region) can be deduced (Scalera, 2012). Also in this case an extrusion of material is favored and the gravimetric data have confirmed (Han et al. , 2011; Zhou et al. , 2012). Similar GRACE results and interpretations have been published for the Maule quake (27 February 2010; Mw=8.8) (Heki and Matsuo, 2010). Already since many years, geodetic GPS networks have given precise indications of what actually takes place on the active margins. The data collected to date for the active margins of Sumatra, Japan, South America and so on, reveal a coseismic deformation of distensional nature (Chlieh et al. , 2007; Lee et al. , 2008; among others). The conclusion is that at least two estreme magnitude events have provided astrogeodetic evidence not in agreement with plate tectonics, but more in accord with an expanding and GNGTS 2014 S essione 1.2 179