Study On The Characteristics Of Schumann Resonance Anomalies Before Earthquakes In Yunnan

China is a country with numerous earthquakes, which had brought great disasterto people‘s lives and significant loss to the country‘s economic development.However, due to the complexity of earthquake preparation mechanism, earthquakemonitoring and prediction is still a world-wide scientific problem, being in theexploration stage at present. In recent years, a large number of observation dataindicate that electromagnetic radiation phenomena with different frequency rangeoccurred around the epicenter before and after the earthquakes. The seismicelectromagnetic precursors draw more and more attention from scientists worldwideas one of the most efficient short-term earthquake monitoring method.Based on the actual need of China Seismo-electromagnetic test Satellite programto build space-ground stereoscopy observation system, the Schumann resonanceobserving experiment was carried out in China for the first time since August2010. Inthis thesis, the anomalous intensity and polarization in Schumann resonance werestudied by using0~30Hz ELF geomagnetic observations at four stations ofYongsheng, Tonghai, Qiaojia and Mangshi in Yunnan province, which will providethe technical support to research on the space-ground comparative analysis andseismo-ionosphere coupling mechanism in future.We introduced the earthquake electromagnetic observation research status ofground passive kind, ground active kind and satellite observation, especially on theapplication of ground-based Schumann resonance observation related to seismicactivities. A comparative analysis was made on some earthquake electromagneticradiation mechanism, such as piezomagnetic effect, piezoelectric effect andelectrokinetic effect. Based on the basic equations in electromagnetic wavepropagation, the formulas of potential, eigenvector and center frequency of Schumannresonance in ideal cavity was deduced. We elaborated the principle of Schumannresonance in ground-ionosphere cavity, spatial distribution and action time of three main excitation sources, and presented the location，system structure and instrumentparameters of Yunnan Schumann resonance earthquake precursor monitor stations.The background variation characteristics were analyzed by using the Schumannresonance geomagnetic field observing data, in which the seasonal variation isobviously, being stronger in summer during April to September, which is consistentwith the enhanced lightning activity in the world during this season. As while, thedaily variation period was also found, showing two valleys in the centre frequency atsunrise and sunset time, which demonstrates that the centre frequency of Schumannresonance varies correspondingly with the intensive variation of ionosphericparameters such as altitude of ionosphere, electron density, conductivity change atthese two time points.More than one year data at four stations were collected. And then, employingseveral methods as the power spectral density analysis, polarization ratio analysis, daymean analysis and pulse signal statistics, we study13seismic cases larger than M4.0during August2010to June2011in Yunnan area, in which pre-earthquake Schumannresonance anomalies were observed before5earthquakes. In the thesis, three caseswith obvious Schumann resonance anomalies were stated in detail, which areYingjiang M5.8, Honghezhou M4.2and Lincang M4.2. The results show thatanomalous spectral density was exhibited a few days before, and characterized bysignificantly enhanced in high order resonant frequency, reaching the maximum at theearthquake occurrence day, and then disappeared after the earthquake. This featurecoincides with other person‘s research. The anomalies in polarization ratio appeared afew days to a week before the earthquakes, where the polarization ratio in1stor2ndSchumann resonance was larger than1and continued a few hours.Finally, we summarized the characteristics of anomalous Schumann resonancerelated to earthquakes in Yunnan province. Abnormal phenomena occurred about afew days to a week before the earthquakes, and disappeared gradually two or threedays after. Two parameters of spectral density and polarization ratio are sensitive, showing significant anomalies. The anomalous spectral density broke the law thatamplitude decreases with increasing resonant frequency, while at some high orderresonant frequencies the intensity increased tens dB than others. The anomalouspolarization ratio at some low order resonant frequencies increased with amplitudelarger than1and duration in a few hours, which is reversed to the law that the ratioenhances with increasing frequency.The observing data in Schumann resonance in Yunnan province china and othercountries all give stable power spectral density and clear centre of frequencies, andthe studies showed certain relevant between anomalous Schumann resonance andseismic activities, which demonstrates the Schumann resonance observation is afeasible method for seismic precursor monitoring and provides a new tool forelectromagnetic monitoring. At present the international research on the relationshipbetween Schumann resonance and earthquakes have not made substantial progress,and our research work on this aspect is just starting, so the coupling mechanism andtheoretical calculation on electromagnetic emissions to Schumann resonance needfurther investigation.