The European Network for studying the radio precursors of earthquakes:udPrincipal Component Analysis of LF radio signals collected during Julyud2009 - April 2011

摘要

Since 2009 a network of VLF (20-60 kHz) and LF (150-300 kHz) radio receivers was put into operation in Europeudin order to study the disturbances produced by the earthquakes on the propagation of these signals. In 2011 theudnetwork for LF signals was formed by six receivers located two in Italy and one in Greece, Portugal, Romania,udand Turkey. The LF radio data collected during about two years have been analysed. Each radio signal has beenudsplit in day-time and night-time data; then, the earthquakes with Mud ud5.0, occurred in the same period, located in aud300 km radius around each receiver/transmitter and within the 5th Fresnel zone related to each transmitter-receiverudpath, have been selected. In this study we adopt the Principal Component Analysis (PCA) to study the radio signaludanomalies possibly related to earthquake activity. A detailed comparison with similar studies that use wavelet analysis is done and advantages or drawback of the two methods are pointed out.