Pre-earthquake ionospheric anomalies registered by continuous GPS TEC measurements

TLDR

The study examines pre‑earthquake ionospheric anomalies using GPS‑derived total electron content. The authors use a 15‑day running median and inter‑quartile range of TEC as a reference to detect abnormal signals for 20 magnitude‑≥6.0 earthquakes in Taiwan from 1999 to 2002. Pre‑earthquake ionospheric anomalies were detected 18:00–22:00 LT within five days before 16 of 20 magnitude‑≥6.0 earthquakes, yielding an 80% success rate and indicating GPS TEC’s usefulness. Keywords: ionosphere, ionospheric disturbances, ionosphere‑atmosphere.

Abstract

Abstract. In this paper we examine pre-earthquake ionospheric anomalies by the total electron content (TEC) derived from a ground-based receiver of the Global Positioning System (GPS). A 15-day running median of the TEC and the associated inter-quartile range (IQR) are utilized as a reference for identifying abnormal signals during all of the 20M≥6.0 earthquakes in the Taiwan area from September 1999 to December 2002. Results show that the pre-earthquake ionospheric anomalies appear during 18:00–22:00LT (LT=UT+8h) within 5 days prior to 16 of the 20M≥6.0 earthquakes. This success rate of 80% (=16/20%) suggests that the GPS TEC is useful to register pre-earthquake ionospheric anomalies appearing before large earthquakes. Key words. Ionosphere (ionospheric disturbances; ionosphere-atmosphere interactions)