A Straightforward Experimental Fact Demonstrating the Physical Interconnection of a SES Activity with Seismicity

Abstract

Around 2 months before the volcanic-seismic swarm activity in 2000 in the Izu Island region, JapanJapan, Uyeda Seiya Uyedaand coworkers found experimentally that Izu Island region a Seismic Electric Signals (SES) activitySeismic Electric Signals activity started on 26 April 2000. Applying naturalNatural time time analysis, we show that the fluctuations $$\beta $$ of the orderOrder parameter of seismicity parameter of Variability minimumseismicity exhibited a clearly detectable minimum approximately at the time of the initiation of the pronounced SES activitySeismic Electric Signals activity detected by UyedaSeiya Uyeda and coworkers. These two phenomena are also linked in space as shown by analyzing in naturalNatural time analysis of seismicity time the earthquakes reported during this period in the JapanJapan Meteorological Agency seismic Seismic catalog Japan Meteorological Agency catalog. This is the first time that, well before the occurrence of major earthquakes, anomalous changes were found to appear approximately simultaneously in two independent datasets of different geophysical observables (Geoelectrical measurements geoelectrical measurements, seismicity). This simultaneous appearance, which also occurred two months before the M9Earthquake, EQ Tohoku Tohoku earthquake (cf. in this case, instead of directly measuring a strong SES activity, Seismic Electric Signals activityanomalous geomagnetic field variations—mainly in the z component—have been recorded), is shown to be far beyond chance.