Ultra low frequency geomagnetic field measurements during earthquake activity in Italy (September-October 1997)

Abstract

Different methods with different results have been proposed in the scientific literature to identify the possible occurrence of weak seismo-magnetic ULF emissions. In September-October, 1997 Central Italy was struck by repeated seismic activity (M L < 5.8). A simple amplitude analysis of the geomagnetic field variations (horizontal components, in the frequency range 4-100 mHz) at a geomagnetic facility located 65-85 km from epicenters of major earthquakes does not reveal in this case any clear evidence for possible ULF emissions.