. 2010, 28(13): 52-57.
By using NDVI data, the continuous change of vegetation prior to the Ms 8.0 Wenchuan earthquake is investigated in this paper. Firstly, according to a comparison year by year, it was found that, to the east of Longmenshan Fault, in Sichuan Basin, the vegetation was degraded by 0～20% from 2005 to 2006. The phenomenon was caused by drought in 2006. Spatially, the movements of Sichuan Basin plate played an important role on the Wenchuan earthquake. Therefore, according to the relationship between drought and earthquake, the degradation could be regarded as one of precursory anomalies prior to the Wenchuan Earthquake. Secondly, the vegetation in early May in Longmenshan Fault was degraded significantly from 2007 to 2008. Moreover, the same phenomenon did not happen in other adjacent faults, like Xianshuihe Fault. As is well known, prior to earthquakes, there may be changes of electric and magnetic fields, gas emissions, groundwater levels, temperature, surface deformations, and so on. These changes are all related with the vegetation degradation to some extent, and they could be seen as a short-term anomaly prior to the 2008 Wenchuan Earthquake. Furthermore, the two anomalies developed spatio-temporally from distant regions to near regions with respect to the epicenter. Additionally, some evidences were found to re-confirm the effects of vegetation anomaly. For example, the anomaly of Earth resistivity was observed 2 years before the earthquake. However, there are some limitations for detection of vegetation anomaly prior to earthquake due to other influencing factors, such as growth periodicity and topography. Further research is needed.
