GNGTS 2019 - Atti del 38° Convegno Nazionale

222 GNGTS 2019 S essione 1.4 GPS time series, if the stations are located on fractured carbonates (e.g., Silveri et al. , 2019, D’Agostino et al. , 2018, Devoti et al. , 2018, Serpelloni et al. , 2018). We will show a few case studies, based on the analysis of GNSS time series, observed in the Alps and in theApennines that demonstrate repeating extension-contraction deformation pattern occurring in different areas, associated with important aquifers at different time scales: episodic rainfall and multi-year rainfall variations. In particular we show two kinds of hydrologic driven deformations. First a loading response, due to seasonal oscillations at regional scale in the Italian peninsula, by comparing the GPS velocity variations during one annual cycle with the variations of equivalent water height retrieved by GRACE observations (Fig. 1). Second, a fractured carbonates response occurring in two different ways: short term transients caused by rainfall, like the effects observed on the Cansiglio Plateau (SE-Alps) during rainwater recharge and discharge; or long term oscillations caused by groundwater storage variations, as those detected in the Aterno Valley (Central Apennines). These deformations seem induced by the interaction of shallow rainfall drainage (short-term) and deep groundwater level variations (long-term) with fractured carbonates especially in karst environments. These deformations are clearly correlated with slow climatic changes and therefore represent a first order noise source in the GNSS time series and for studies that aim to isolate slow drifting tectonic processes. References D’Agostino N., Silverii F., Amoroso O., Convertito V., Fiorillo F., Ventafridda G. and Zollo A.; 2018: Crustal deformation and seismicity modulated by groundwater recharge of karst aquifers. Geophys. Res. Lett., 45, 12253–12262. Darwin G.H.,1882; On variation of the vertical due to elasticity of the Earth’s surface. Philosophical Magazine and Journal of Science, London, Edinburgh, and Dublin. Devoti R., D’Agostino N., Serpelloni E., Pietrantonio G., Riguzzi F., Avallone A., Cavaliere A., Cheloni D., Cecere G., D’Ambrosio C., Falco L., Selvaggi G., Métois M., Esposito A., Sepe V., Galvani A. and Anzidei M.; 2017: The mediterranean crustal motion map compiled at INGV. Ann. Geophys., 60, 2, S0215. doi:10.4401/ag-7059 Devoti R., Riguzzi F., Cinti F.R. and Ventura G.; 2018: Long-term strain oscillations related to the hydrological interaction between aquifers in intra-mountain basins: A case study from Apennines chain (Italy). Earth Planet. Sci. Lett., 501, 1-12. doi:10.1016/j.epsl.2018.08.014. Ikehara M.E. and Phillips S.P.; 1994: Determination of land subsidence related to ground-water-level declines using Global Positioning System and leveling surveys in Antelope Valley, Los Angeles and Kern Counties, California, 1992: U.S. Geological Survey Water-Resources Investigations Report, 94-4184, 101 p. Serpelloni E., Pintori F., Gualandi A., Scoccimarro E., Cavaliere A., Anderlini L., Belardinelli M.E. and Todesco M.; 2018: Hydrologically induced karst deformation: Insights from GPS measurements in the Adria-Eurasia plate boundary zone. J. Geophys. Res. Solid Earth, 123, 4413-4430. Silverii F., D’Agostino N., Borsa A.A., Calcaterra S., Gambino P., Giuliani R. and Mattone M.; 2019: Transient crustal deformation from karst aquifers hydrology in the Apennines (Italy). Earth Planet. Sci. Lett., 506, 23-37, doi:10.1016/j.epsl.2018.10.019.  Schuh H. and Moehlmann L.; 1989: Ocean loading station displacements observed by VLBI. Geophys. Res. Lett., 16, 10, 1105-1108. Terzaghi K. (1943). Theoretical soil mechanics. John Wiley & Sons, Inc. van Dam T., Wahr J., Milly P.C.D., Shmakin A.B., Blewitt G., Lavallée D. and Larson K.M.; 2001: Crustal displacements due to continental water loading. Geophys. Res. Lett., 28, 651–654. doi:10.1029/2000GL012120. Zerbini S., Matonti F., Raicich F., Richter B. and van Dam T.; 2004: Observing and assessing non tidal ocean loading using ocean, continuous GPS and gravity data in the Adriatic area, Geophys. Res. Lett., 31, L23609, doi:10.1029/2004GL021185.