摘要
The authors studied the changes of the electric field before the Wenchuan earthquake 2008 using both space-based and ground-based observational data and the method of marginal spectrum. The result reveals that the marginal spectrum of the electric field in the ionosphere had a remarkable increase from the 27th April, 2008 to the time when the Wenchuan earthquake happened. For the evolution of marginal spectrum of the electric field from the ground-based data, the marginal spectrum of Songshan station of Sino-French cooperation began to enhance. Such a phenomenon appeared at Chengdu, Longnan and Tianshui stations. It seems that the enhancement of marginal spectra of both the ground and space electric fields happened at a roughly same time.