Using GPS to Assess Earthquake Potential in Friuli (NE Italy) Abstract

abstract

  • On 6 May 1976, a magnitude 6.4 earthquake struck the Friuli region of northeastern Italy near the towns of Gemona and Venzone. Although it was not as large as some previous earthquakes in Italy, its severe ground motion (up to 0.36 g) affected an area with numerous historical towns, resulting in 989 fatalities and 45,000 people left homeless. At least four other destructive earthquakes with epicentral intensity greater than or equal to IX on the Mercalli-Cancani-Sieberg scale have occurred in the Friuli region in the last 5 centuries (1511, 1700, 1794, and 1928).
    Seismicity in the Friuli-Venezia Giulia region (NE Italy) demarcates the boundary between a proposed Adria microplate and the Eurasian plate. The observed thrust and strike-slip earthquake focal mechanisms suggest that seismotectonic characteristics of the region are not homogeneous, and that the contemporary seismic deformation pattern is likely to be complex. We have initiated geodetic studies to better characterize and monitor deformation along the NE edge of the Adria microplate. The major objectives of the Friuli Deformation project are:
    1. To measure crustal movements throughout NE Italy to better assess earthquake potential.
    2. To identify active blind thrust faults and test models of tectonics in the Friuli and Adriatic region.
    3. To measure local variations in strain rate that might reveal the mechanical properties of earthquake faults.
    4. In the event of an earthquake, to measure permanent crustal deformation to improve estimates of the extent and magnitude of slip on the fault, strong ground motions, and possible changes in stress on nearby major faults.
    Between the summer of 2002 and the winter of 2003, we installed the initial 7 continuous GPS stations of the Friuli Deformation Network (FReDNet) to provide regional crustal deformation data and support for survey-mode GPS operations. We are currently planning local geodetic networks for survey-mode GPS measurements to provide a detailed picture of the local deformation in areas of particular interest (i.e., location of seismic gaps). Beginning this summer, these networks will surveyed once every two years over the next five years. Finally, we plan to use the geodetic data to improve our understanding of the kinematics, tectonics, and earthquake cycle in Friuli. We are currently using continuous GPS measurements and block modeling to investigate the active present-day deformation of the Adria microplate, whose kinematics is not well constrained and remain controversial.

authors

publication date

  • 2004

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