Giant disturbance in the ionospheric F2 region prior to the <i>M</i>8.0 Wenchuan earthquake on 12 May 2008

Abstract

On 12 May 2008 at 14:28 LT great earthquake (M=8.0) occurred at Wenchuan (31.00° N, 103.40° E), China. The hourly values of foF2 are analyzed over ten ionospheric observatories: Haikou (20.00° N, 110.33° E), Kunming (25.00° N, 102.70° E), Guangzhou (20.00° N, 113.70° E), Chongqing (29.50° N, 106.40° E), Lhasa (29.63° N, 91.17° E), Lanzhou (36.07° N, 103.87° E), Beijing (40.00° N, 116.30° E), Urumqi (43.75° N, 87.63° E), Chuangchun (43.83° N, 125.30° E) and Manzhouli (49.60° N, 117.45° E). With a new factor, effective sunspot number Reff, the results show that there were giant positive disturbances of foF2 around the epicentral zone on 9 May, 3 days prior to the earthquake. Our results indicate that the observed positive ionospheric disturbances were most possibly associated with the imminent earthquake and the new analytic method has good prospects in practice.