Multi-point measurement system and data processing for earthquakes monitoring

Lithospheric ultra low frequency (ULF) magnetic activity is recently considered as very promising candidate for application to short-time earthquake (EQ) forecasting. However the intensity of the ULF lithospheric magnetic field is very weak and often masked by much stronger ionospheric and magnetospheric signals. The study of pre-EQ magnetic activity before the occurrence of strong EQ is a very hard problem which consists of the identification and localization of weak signal sources in EQ-hazardous areas of the Earth's crust. A new approach is developed to find a source of pre-EQ ULF electromagnetic activity of lithospheric origin. For separation and localization of such sources a new polarization ellipse technique has been used to process data acquired from 3-component magnetometers. The polarization ellipse is formed by the magnetic field components at the measurement station. Calculations based on polarization ellipse parameters from two distant points allow discrimination of seismo-EM signals from natural background ULF signals. The results of experimental verification of this method in Kanto region (Japan), known as one of the most seismoactive, are given which partially confirm its efficiency and give hope, with its further improvement, to the progress in the EQ precursors reliable detection in other regions of the Globe, particularly, in Iceland known by the active seismic activity.