Etn@ref: a geodetic reference frame for Mt. Etna GPS networks

Massimo Rossi Massimo Rossi,Flavio Cannavò Flavio Cannavò,Valentina Bruno Valentina Bruno,Mimmo Palano Mimmo Palano,Mario Mattia Mario Mattia,Mario Pulvirenti Mario Pulvirenti,Giuseppe Siligato Giuseppe Siligato,Daniele Pellegrino Daniele Pellegrino,Marco Aloisi Marco Aloisi

doi:10.4401/ag-4879

Abstract

In volcanology, geodetic data are one of the most important instruments for the scientific community interested in modeling physical processes related to magma movements in the shallow crust. Since the end of the 1980s, GPS surveys and continuous GPS stations have greatly improved the possibility of measuring such movements with high time and space resolution. However, physical modeling requires that any external influence on the data that is not directly related to the investigated quantity must be filtered. One major tricky factor in determining a deformation field using GPS displacement vectors and velocities is the correct choice of a stable reference frame. In this study, we defined a local reference frame using more than a decade of GPS measurements, to refer the Mt. Etna ground deformation pattern to a rigid block. In particular, we used a weighted least-squares inversion to estimate the Euler pole for the rigid block by minimizing the adjustments to two horizontal components of GPS velocity at 13 «fiducial» sites located within a 350-km radius of Mt. Etna. The inversion inferred a Euler pole located at 38.450˚N and C107.702˚E, and a rotation rate of 0.263 deg/Myr.

Highlights

Routine use of GPS for monitoring ground deformation started at Mt
Global and regional solutions for GPS networks are typically analyzed in a global reference frame which is defined at a particular time by choosing: (i) an origin representing the point where three axes intersect; (ii) a scale representing the unit of measurement; and (iii) directions for three orthogonal Cartesian axes
The software package was developed to work readily with GAMIT/GLOBK velocity field files and velocity «apriori» files. This allows to calculate the expected velocity value for any point located on the Earth for a given Euler pole, or to infer the Euler pole parameters by inverting the observed velocity at a set of sites located on a rigid block

Summary

Introduction

Routine use of GPS for monitoring ground deformation started at Mt. Etna in 1988, when a network of 18 benchmarks was surveyed by both GPS and EDM (Electronic Distance Measurement) techniques [Briole et al 1992]. The ITRF is maintained by the International Earth Rotation Service, which monitors the Earth orientation parameters through a global network of observing stations This is carried out using space geodesy techniques, such as: very long baseline interferometry, lunar laser ranging, satellite laser ranging, Doppler orbitography and radio positioning integrated by satellite, and GPS observations (see Altamimi et al [2007] for an overview). One observer using different frames over time cannot compute valid velocity estimates Scalar quantities, such as baseline length, have a minimal dependence on the reference frame and are affected by the choice of unit, and not by the origin or orientation of the frame [Heflin et al 2002]. This rotation model essentially constrains the block to move rigidly on the Earth surface (no radial motion)

Euler pole estimation

Discussion and conclusions