HR: 13:55h
AN: T43E-02    [Abstracts]
TI: Analysis of Seismicity and Electrical Activity in the Natural Time-Domain for the Volcanic - Seismic Swarm Activity in 2000 in the Izu Island Region, Japan
AU: * Uyeda, S
EM: suyeda@st.rim.or.jp
AF: Earthquake Prediction Center, Tokai University, 3-20-1 Orido, Shimizu-ku, Shizuoka, 424-8610 Japan
AU: Tanaka, H
T43E-02 AF: Earthquake Prediction Center, Tokai University, 3-20-1 Orido, Shimizu-ku, Shizuoka, 424-8610 Japan
AU: Varotsos, P A
T43E-02 AF: Solid State Section, Physics Department, University of Athens, Panepistimiopolis, Zografos, Athens, 157 84 Greece
AU: Sarlis, N V
T43E-02 AF: Solid State Section, Physics Department, University of Athens, Panepistimiopolis, Zografos, Athens, 157 84 Greece
AU: Skordas, E S
T43E-02 AF: Solid Earth Physics Institute, Physics Department, University of Athens, Panepistimiopolis, Zografos, Athens, 157 84 Greece
AU: Nagao, T
T43E-02 AF: Earthquake Prediction Center, Tokai University, 3-20-1 Orido, Shimizu-ku, Shizuoka, 424-8610 Japan
AU: Kamogawa, M
T43E-02 AF: Department of Physics, Tokyo Gakugei University, 4-1-1 Nukui-kitamachi, Koganei-shi, Tokyo, 184-8501 Japan
AB: Seismicity and geoelectric potential changes, associated with the volcanic - seismic swarm activity in 2000 in the Izu Island Region, Japan, have been analysed in the framework of the recently introduced natural time. In a time series comprised of N events, the natural time χ _k serves as the index for the occurrence of the k th event. In natural time analysis, the evolution of the pair of two quantities (χ _k, Q_k) is considered, where Q_k denotes the quantity proportional to the energy Q of the k th event. It has earlier been shown theoretically that, in the very small natural frequency range, the power spectrum of the time series of the normalized Q_k exhibits a characteristic behaviour when the system approaches the critical point. The above mentioned swarm activity in the Izu Island region, lasting for about two months with some 7,000 shocks with magnitude M≥q 3 and five M≥q 6 shocks, was preceded by a pronounced electrical activity with innumerable signals that started a few months prior to the swarm onset. It has been shown first that the seismicity subsequent to the electrical activity approached to the critical point a few days before the occurrence of the first M≥q 6 shock, and second that the electrical signals also have the properties characteristic to a critical stage. These features were similar to those found in Greece earlier. The present results show that, both in Greece and Japan, the electrical activity and the subsequent seismicity have properties of critical state, e.g., infinitely long range correlation in time. With shuffled data, these properties can not be obtained.
DE: 4425 Critical phenomena
DE: 7209 Earthquake dynamics (1242)
SC: Tectonophysics [T]
MN: Fall Meeting 2005