title: Spatiotemporal variations of seismicity before major earthquakes in the Japanese area and their relation with the epicentral locations.
abstract: Using the Japan Meteorological Agency earthquake catalog, we investigate the seismicity variations before major earthquakes in the Japanese region. We apply natural time, the new time frame, for calculating the fluctuations, termed β, of a certain parameter of seismicity, termed κ1. In an earlier study, we found that β calculated for the entire Japanese region showed a minimum a few months before the shallow major earthquakes (magnitude larger than 7.6) that occurred in the region during the period from 1 January 1984 to 11 March 2011. In this study, by dividing the Japanese region into small areas, we carry out the β calculation on them. It was found that some small areas show β minimum almost simultaneously with the large area and such small areas clustered within a few hundred kilometers from the actual epicenter of the related main shocks. These results suggest that the present approach may help estimation of the epicentral location of forthcoming major earthquakes.
authors.affiliation: Solid State Section and Solid Earth Physics Institute, Physics Department, University of Athens, Zografou 157 84, Athens, Greece;
authors.forename: Nicholas V
authors.initials: NV
authors.lastname: Sarlis
authors.affiliation: Solid State Section and Solid Earth Physics Institute, Physics Department, University of Athens, Zografou 157 84, Athens, Greece;
authors.forename: Efthimios S
authors.initials: ES
authors.lastname: Skordas
authors.affiliation: Solid State Section and Solid Earth Physics Institute, Physics Department, University of Athens, Zografou 157 84, Athens, Greece;
authors.forename: Panayiotis A
authors.initials: PA
authors.lastname: Varotsos
authors.affiliation: Earthquake Prediction Research Center, Institute of Oceanic Research and Development, Tokai University, Shizuoka 424-0902, Japan;
authors.forename: Toshiyasu
authors.initials: T
authors.lastname: Nagao
authors.affiliation: Department of Physics, Tokyo Gakugei University, Koganei-shi 184-8501, Japan; and.
authors.forename: Masashi
authors.initials: M
authors.lastname: Kamogawa
authors.affiliation: Section II, Division 4, Japan Academy, Tokyo, 110-0007, Japan suyeda@st.rim.or.jp.
authors.forename: Seiya
authors.initials: S
authors.lastname: Uyeda
keywords: criticality; natural time analysis; seismic electric signals