. 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)

/pdf/pre-earthquake-ionospheric-anomalies-registered-by-yvax7civgs.pdf

Pre-earthquake ionospheric anomalies registered by continuous GPS TEC measurements

Main phenomenological features of ionospheric precursors of strong earthquakes

This paper accumulates the recent advances in scientific understanding of the problem of seismo-ionospheric coupling. Present research focuses on three main areas: the physical mechanism, main phenomenological features of ionospheric variations associated with earthquakes, and their statistical properties permitting use of them in practical applications. In this paper, the developed physical model bridges the traditional precursors of earthquakes and ionospheric ones, demonstrating that the latter belong to the same family. In this regard the earthquake preparation zone is key generating the scaling law and the relationship between geochemical precursors, anomalous electric field involved in ionospheric variations initiated, and the ionospheric irregularities themselves. Revealed ionospheric precursor phenomena and their statistical parameters are used to develop a pattern recognition technique and other statistical processing techniques that can be used in short-term earthquake prediction. Finally a possible system of ground based measurements and satellite monitoring is proposed for regional and global monitoring and possible short-term prediction of destructive earthquakes.

/pdf/ionospheric-precursors-of-earthquakes-recent-advances-in-2uevj9xq5e.pdf

Ionospheric Precursors of Earthquakes; Recent Advances in Theory and Practical Applications

The physical mechanism by which the regions with increased or decreased total electron content, registered by measuring delays of GPS satellite signals before strong earthquakes, originate in the ionosphere has been proposed. Vertical plasma transfer in the ionospheric F2 region under the action of the zonal electric field is the main disturbance formation factor. This field should be eastward, generating the upward compo� nent of plasma electromagnetic drift, in the cases of increased total electron content at midlatitudes and deepened minimum of the F2 layer equatorial anomaly. Upward plasma drift increases electron density due to a decrease in the O + ion loss rate at midlatitudes and decreases this density above the equator due to an enhancement of the fountain effect (plasma discharge into the equatorial anomaly crests). The pattern of the spatial distribution of the seismogenic electric field potential has been proposed. The eastward electric field can exist in the epicentral region only if positive and negative electric charges are located at the western and eastern boundaries of this region, respectively. The effectiveness of the proposed mechanism was studied by modeling the ionospheric response to the action of the electric field generated by such a charge configuration. The results of the numerical computations indicated that the total electron content before strong earthquakes at middle and low latitudes is in good agreement with the observations.

Physical mechanism and mathematical modeling of earthquake ionospheric precursors registered in total electron content

http://www.stat.ncu.edu.tw/teacher/YIChen/Precursors%20paper/P46.pdf

A statistical study of ionospheric earthquake precursors monitored by using equatorial ionization anomaly of GPS TEC in Taiwan during 2001-2007

Three large earthquakes struck central Taiwan near the towns of Rei-Li on 17 July 1998, Chi-Chi on 20 (21 for local time) September 1999 and Chia-Yi on 22 October 1999, respectively These earthquakes severely damaged structures heavily changed landforms and disturbed geophysical environments In this paper, a procedure is introduced to derive the ionospheric total electron content (TEC) from data recorded by a network of the Global Positioning System (GPS) in Taiwan Based on the network data, the latitude-time-TEC (LTT) plots prior to the three earthquakes are constructed The plots show that during 1-4 days prior to the three earthquake onsets, the TEC values decrease and the anomaly crests move toward the equator

A study on the TEC perturbations prior to the Rei-Li, Chi-Chi and Chia-Yi earthquakes

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A study on the TEC perturbations prior to the Rei-Li, Chi-Chi and Chia-Yi earthquakes