Abstract
Abstract. There have been many reports on ULF electromagnetic phenomena associated with the 2000 Izu Islands earthquake swarm. In this study, seismo-magnetic anomalies are presented by examining energy variations of signatures at the periods around 100 s. Geomagnetic data observed at three stations in Izu Peninsula from 1 January 2000 to 30 April 2001 have been analyzed and wavelet transform has been performed. In order to indentify anomalous changes from ionosphere disturbances, Kakioka station has been chosen as a reference station, and the similar data analysis has been performed. The results suggest that the unusual energy enhancement of the Z component, which only appears in Izu Peninsula from late June until early November 2000, might possibly be one of electromagnetic phenomena associated with the 2000 Izu Islands earthquake swarm.
Highlights
Earthquakes are one of the most destructive of all natural hazards, and it has long been a dream of scientists to achieve effective prediction
For the Z component, it was found that the energy at all three stations on the Izu peninsula begins to increase from June 2000 onwards, and this remarkable enhancement lasts until November
The ULF geomagnetic data observed on the Izu Peninsula have been investigated by the wavelet analysis method to detect any possible anomalous changes related to the 2000 Izu Islands earthquake swarm
Summary
Earthquakes are one of the most destructive of all natural hazards, and it has long been a dream of scientists to achieve effective prediction. The detection of electromagnetic perturbations prior to fault ruptures or volcanic eruptions has often been proposed as a simple and effective method for monitoring crustal activities. Electromagnetic phenomena have been considered promising candidates for short-term earthquake prediction. A lot of evidence of seismo-electromagnetic precursory signatures in a wide frequency range from DC to VHF has been reported (e.g., Johnston, 1997; Hayakawa et al, 2008). Abundant indoor/outdoor experiments and numerical simulations (Molchanov and Hayakawa, 1995; Huang and Ikeya, 1998; Huang, 2002, 2005; Huang and Lin, 2010) have confirmed the existence of this seismo-electromagnetic phenomenon. Passive ground-based observation of ULF (ultra low frequency) geomagnetic signatures is considered to be the most promising method for seismomagnetic phenomena study. In order to verify electromagnetic phenomena preceding large earthquakes, a sensitive geomagnetic network has been installed in Japan (Hattori et al, 2004a) and plenty of data associated with moderate-large earthquakes have been accumulated
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