A Measurement Node for the continuous gravity and tilt observations in an activegeodynamic area of southern Italy: the Calabrian Arc system

A Measurement Node for the continuous gravity and tilt observations in an active

geodynamic area of southern Italy: the Calabrian Arc system

Anna Albano¹, Vincenzo Carbone¹, Francesco Lamonaca²

¹Dipartimento di Fisica, Università della Calabria, Arcavacata di Rende (CS), Italy

²Dipartimento di Ingegneria Informatica, Modellistica, Elettronica e Sistemistica,
Università della Calabria, Arcavacata di Rende (CS), Italy

 

Calabria (southern Italy) is a site of considerable seismic activity related to the ongoing evolution of the Calabrian Arc system, where a complex lithospheric structure is present. For over a century the Calabrian region has been going through a period of relative seismic quietness, yet its seismic hazard is at the highest levels in the Mediterranean basin due to several catastrophic earthquakes present in the historical records. In order to strengthen the geophysical monitoring of this region, a gravity and tilt recording station was set up in the premises of the University of Calabria. The measurement node is composed by the gravimeter G-1089 from LaCoste & Romberg; the tilt-meter Model 714 from Applied Geomechanics; a 6 and ½ digits multimeter Agilent 34970A data acquisition and switching unit used to converts the analog signals of the gravimeter and tilt-meter in the corresponding digital ones; a computer used to store, elaborate and present the signals. The delay among the input channels of the multimeter is evaluated and the optimal configuration is achieved in order to make such a delay negligible for the time correlation of the input signals. The measurement node is positioned on the ground of the cube 41C. Finally, the information about the temperature and the atmospheric pressure is obtained by the nearby environmental station positioned on the roog of cube 41B. The recorded signals should allow to estimate a tidal anomaly, possibly correlated with the difference between some local feature of the lithosphere or geodynamic activity and the corresponding characteristics of the model used to calculate the reference gravity tide. A reliable model of the gravity tide is necessary for accurate processing of discrete absolute and relative gravimetric measurements and to detect in the gravity signals possible components correlated to major seismic activity. The Ocean Tide Load (OTL) effect was accounted for in the determination of the tidal field spectral parameters. The most widespread DDW99/ NH Earth’s model, adopted here as reference, fits the obtained results well enough.