arXiv subjects

A. Piersanti

Publications and source records attributed to A. Piersanti.

5 recordsLinked to original sources

arXiv2015

Long term continuous radon monitoring in a seismically active area

We present the results of a long term, continuous radon monitoring experiment started in April 2010 in a seismically active area, affected during the 2010-2013 data acquisition time window by an intense micro seismic activity and by several small seismic events. We employed both correlation and cross-correlation analyses in order to investigate possible relationship existing between the collected radon data, seismic events and meteorological parameters. Our results do not support the feasibility of a robust one-to-one association between the small magnitude earthquakes characterizing the local seismic activity and single radon measurement anomalies, but evidence significant correlation patterns between the spatio-temporal variations of seismic moment release and soil radon emanations, the latter being anyway dominantly modulated by meteorological parameters variations.

physics.geo-ph↗

arXiv2007

Core-mantle boundary deformations and J2 variations resulting from the 2004 Sumatra earthquake

The deformation at the core-mantle boundary produced by the 2004 Sumatra earthquake is investigated by means of a semi-analytic theoretical model of global coseismic and postseismic deformation, predicting a millimetric coseismic perturbation over a large portion of the core-mantle boundary. Spectral features of such deformations are analysed and discussed. The time-dependent postseismic evolution of the elliptical part of the gravity field (J2) is also computed for different asthenosphere viscosity models. Our results show that, for asthenospheric viscosities smaller than 10^18 Pa s, the postseismic J2 variation in the next years is expected to leave a detectable signal in geodetic observations.

physics.geo-ph↗

arXiv2005

Impact of global seismicity on sea level change assessment

We analyze the effect of seismic activity on sealevel variations, by computing the time-dependent vertical crustal movement and geoid change due to coseismic deformations and postseismic relaxation effects. Seismic activity can affect both the absolute sealevel, by changing the Earth gravity field and hence the geoid height, and the relative sealevel, i.e. the radial distance between seafloor and geoid level. By using comprehensive seismic catalogues we assess the net effect of seismicity on tidal relative sealevel measurements as well as on the global oceanic surfaces, and we obtain an estimate of absolute sealevel variations of seismic origin. Our results confirm that, on a global scale, most of the signal is associated with few giant thrust events, and that RSL estimates obtained using tide-gauge data can be sensibly affected by the seismic driven sealevel signal. The recent measures of sealevel obtained by satellite altimetry show a wide regional variation of sealevel trends over the oceanic surfaces, with the largest deviations from the mean trend occurring in tectonically active regions. While our estimates of average absolute sealevel variations turn out to be orders of magnitude smaller than the satellite measured variations, we can still argue that mass redistribution associated with aseismic tectonic processes may contribute to the observed regional variability of sealevel variations.

physics.geo-ph↗

arXiv2005

Transient deformations in the Suez-Sinai area from GPS observations

We analyze data from four GPS campaigns carried out between 1997 and 2002 on a network of 11 sites in the Suez-Sinai, the area of collision between the African and the Arabian plates. This is the key area to understand how and in which way Sinai behaves like a sub-plate of the African plate and the role played between seismic and geodetic (long term) deformation release. Our analysis shows that, on average, the Suez-Sinai area motion (in terms of ITRF00 velocities) matches African plate motion (NNR-NUVEL-1A model). However, the baseline length variations show transient deformations in Sinai and across the Gulf of Suez, reaching up a maximum value of about 1.5 cm in five years. Since current geodynamical models do not predict significant tectonic deformation in this area, we worked under the hypothesis that a contribute may be due to post-seismic relaxation. Under this hypothesis, we compared the baselines length variations with the post-seismic relaxation field associated with five major local earthquakes occurred in the area, testing two different viscoelastic models. Our results show that the transient deformations are better modelled for viscosity values of 1018 Pa s in the lower crust and 1020 Pa s in the asthenosphere. However, since the modelled post-seismic effect results modest and a certain amount of the detected deformation is not accounted for, we think that an improved modelling should take into account the lateral heterogeneities of crust and upper mantle structures.

physics.geo-ph↗

arXiv2005

Global permanent deformations triggered by the Sumatra earthquake

The giant Sumatra-Andaman earthquake of December 26 2004 caused permanent deformations effects in a region of previously never observed extension. The GPS data from the world wide network of permanent IGS sites show significant coseismic displacements in an area exceeding 107 km^2. The effects of the permanent residual deformation field could be detected as far as Australia, the Phillipines and Japanese archipelagos, and, on the West, as far as the indian continent. The synthetic simulations of the coseismic displacement field obtained by means of a spherical model support the hypothesis that a considerable amount of energy has been released aseismically.

physics.geo-ph↗