Do earthquake precursors really exist

Pulinets [2007] discusses “ionospheric precursors” of earthquakes observed at Chung-Li (Taiwan). If such precursors really exist and, as suggested, are caused by localized electric fields of seismic origin, those fields would be mirrored at Chung-Li's magnetically conjugate point near 8°S, 121°E,and would cause similar localized effects there. Are these conjugate effects seen in the satellite data? Too many papers say, in effect,“An earthquake has happened! Can we see a bump in the ionosphere a few days beforehand? Yes, we can! It's a precursor!” No surprise there. The F2 layer at 300 kilometers (the relevant ionospheric layer) frequently shows bumps. The few days of Chung-Li ionospheric data preceding the quakes of 16 September and 21 October 1999, shown by Kamogawa [2006] and Pulinets [2007], respectively, look like typical F2 layer variations at times of geomagnetic activity, which was indeed prevalent during these periods. Significant dayto-day variations occurred, too, as far away as Australia, the United States, and the United Kingdom. So all solar-geophysical conditions must be taken into account before attributing F2 layer variations to forthcoming earthquakes.