Although earthquake is one of major natural disasters, the immediate near-term prediction of earthquake largely remains elusive despite intense investigation, enormous effort and resources worldwide [1-5]. In order to better understand earthquakes and find correlations that are seemingly totally unrelated events, an open-minded and broad search is necessary.

After the 8.0 magnitude earthquake on May 12th, 2008 along the fault of Wenchuan-Beichuan counties in Sichuan Province, which has been showed in Figure 1, another 6.1 magnitude earthquake occurred on August 30th, 2008 in the boundary of Renhe area of Panzhihua and Huili county of Liangshan Yi Autonomous Prefecture that also located in the same seismic area, Sichuan Province.

These events stimulated us to search for a wide range of natural phenomena that may aid us to better understand the onset of earthquakes.

The major seismic area was located in the central segment of “Helan-ChuanDian Tectonic Belt”, which also called “China’s North-South Tectonic Belt” and “The Longmen mountain fault zone”.

We ask if there is a correlation between the intense and dense lightning and seismic activities. Previous studies have reported that the ionosphere activities at 0.1 - 10 km height and electrically active clouds were produced in an atmosphere sometimes in the eve of earthquake [6-8]. A possible influence of electromagnetic fields of seismic origin in the ionosphere-magnetosphere transition region has also been reported [9-11]. Our studies focus on lightning. It has been observed that there is frequent lightning in the period during the earthquakes. In the past observations before the Wenchuan earthquake, the highest period of lightning in that area is usually between May and August.

Prior 2005, there were sparse lightning monitoring systems in Sichuan, thus there were little available data. But these systems were significantly improved in 2005, making it possible for data collection and analyses. Based on our lightning monitoring data for 2005-2012, some interesting correlations were found between the lightning density distribution of Sichuan province and the seismic belt. In order to understand the correlations between lightning and earthquake, we carried out systematic analyses of available data. Figure 2 shows the lightning density distribution of Sichuan. Although there are only 8-year available data, it may nevertheless shed some light on the seemingly unrelated events.

We recorded some very unusual lightning event from ~15:00, September 23rd to ~12:00, September 24th, which was an intense and dense lightning period, accompanied heavy precipitation. And it had the highest density and intensity in all the available lightning monitoring data in

Sichuan. In the past, September usually does not have the high incidence period of lightning in Sichuan’s weather history. It seems that the weather pattern has been disturbed by the seismic activities.

Our lightning forecasting system predicted that lightning would occur at ~20:00, September 22nd. We predicted that the highest probability during following 12 hours was 80% in Sichuan including in greater Chengdu area. The forecasting placed a special warning ~20:00 on September 23rd. We also predicted that the highest probability in next 12 hours in the earthquake area was up to 90%. The intense and lightning indeed not only came as predicted but also was the first record that the highest dense lightning occurred at the end of flood season.

Figure 3 shows that the lightning distribution and the “Longmen mountain fault zone” and the Panxi seismic area are nearly overlapped. This seems unlikely a coincidence alone. It seems plausible there existed some correlation between the September 22nd heavy lightning and the May 12th earthquake. Whether the seismic activities influenced the lightning still need to be further analyzed and demonstrated.