Xinyan Ouyang

Ionospheric perturbations of electron density before the Wenchuan Earthquake

Based on electron density data recorded by the Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions (DEMETER) satellite of France, the phenomena of disturbed electron density in the ionosphere before the Wenchuan Earthquake of magnitude 8.0 on 12 May 2008, were analysed. The results showed that the anomalies concentrated 3 days prior to the earthquake, especially the variation on 9 May, when the electron density reduced above the northeast epicentral area, and the peak values moved to the equator. Compared with the variations in the geomagnetic indexes and other parameters related to solar activity, the geomagnetic condition and solar activity were all quiet from 7 to 12 May, so the variation on 9 May might be related to this strong earthquake. In addition, the geomagnetic field observed at the surface was analysed, and the Z component data at stations near the epicentral area showed apparent aberrations of daily variation compared with those at stations in eastern China. All these phenomena illustrate that obvious perturbations in the ionosphere and at the surface might be related to the preparation process of the Wenchuan Earthquake.

Automatic collecting technique of low frequency electromagnetic signals and its application in earthquake study

Two methods to automatically collect disturbed ultra low frequency electromagnetic signals before strong earthquakes were developed in this paper, in which one is only related to the spectrum intensity of electric field, and another is additionally combined with fractal dimension feature in electromagnetic emissions. Both techniques were applied for satellite data processing, case study and precursor distinction around Chile earthquakes, especially those occurring in 2010. Their advantages and disadvantages were compared and discussed based on actual application results. Further research on data mining needs to be carried out to improve the old and to develop the new ones based on the property of electromagnetic waves and multi parameters.

Study on the electronic density perturbation detected by DEMETER satellite before Wenchuan earthquake

We used slope analysis and sliding Median method to study the electron density data observed by Langmuir probe of DEMETER satellite since April 25, 2008 to May 11, 2008, and obvious perturbation phenomena of electron density(Ne) in ionosphere were found before Wenchuan earthquake on May 12, 2008. Considering the geomagnetic disturbances, there were some abnormal information in different degrees on May 3, 4, 7, 9, 10, 11 respectively. Furthermore, on May 3 and May 4, along with the change of electron density, electron temperature was also elevated at the latitude of 10∼30°N. Also on May 7, not only electron density increased, but also ion density did above the epicentral area.