GNGTS 2017 - 36° Convegno Nazionale

GNGTS 2017 S essione 1.1 97 labelled “long-term pre-seismic phase”) may be distinguished from that which occurred in the following, 2008/09/01 to 2009/02/01 time span (hereinafter labelled “short-term pre-seismic phase”; Fig. 1). In long-term pre-seismic phase we observe that vertical ground deformation in the region that includes L’Aquila and encompasses the Middle Aterno valley Quaternary basin and the elevations to the SW of it, was characterised by an uplift trend (Figs. 2 and 3), while the horizontal displacement was oriented towards the east. Conversely, in the short-term pre- seismic period, i.e. starting from about five months prior to the main shock, we observe that vertical ground deformation was characterised by subsidence, while the horizontal component was oriented towards the west (Figs. 1, 2 and 3). Discussion and concluding remarks. The investigation of an about 20 years-long time window has allowed the recognition of pre-seismic displacement in the L’Aquila 2009 earthquake epicentral area starting from about three years before the main shock. Crucial to the detection of pre-seismic ground deformation has been the combination of SAR ascending and descending orbits datasets. The displacement that has been identified during the long-term pre-seismic phase is consistent with the findings by Moro et al. (2017) for the Pizzoli area (Fig. 2). However, a much wider area to the south, which includes both the Middle Aterno basin and the ridges to the SW, is characterised by a different behaviour. The multi-temporal analysis of PS-InSAR data from both ascending and descending orbits that we have performed for this wider area has allowed the identification of a complex displacement sequence, which initiated with uplift (in the long-term pre-seismic phase) and was followed by subsidence. Our analysis points out that the change from one displacement trend to the other occurred around five months before the main shock (Figs. 2 and 3). References Amoruso A. and Crescentini L.; 2010: Limits on earthquake nucleation and other pre-seismic phenomena from continuous strain in the near field of the 2009 L’Aquila earthquake . Geophys. Res. Lett., 37 (10). Atzori S., Hunstad I., Chini M., Salvi S., Tolomei C., Bignami C., Stramondo S., Trasatti E., Antonioli A. and Boschi E.; 2009: Finite fault inversion of DInSAR coseismic displacement of the 2009 L’Aquila earthquake (central Italy) . Geophys. Res. Lett., 36 , L15305. Atzori S., Chiarabba C., Devoti R., Bonano M. and Lanari R.; 2013: Anomalous far-field geodetic signature related to the 2009 L’Aquila (central Italy) earthquake . Terra Nova, 25 , 343–351. 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