Survey of a relationship between precipitation and major earthquakes along the Peru-Chilean trench (2000–2015)

In this study, the possible relationship between anomalous precipitation and five very large earthquakes along the Peruvian- Chilean trench (2001/06/23 M8.4, 2007/08/15 M8.0, 2010/02/27 M8.8, 2014/04/01 M8.2, and 2015/09/16 M8.3) is surveyed. A precipitation archive and earthquake database has been compiled for 2000–2015 for this part of South America. According to the mean daily precipitation data given by the National Centers for Environmental Prediction (NCEP), an anomalous increase in precipitation occurred within two months before these earthquakes over their respective epicentral areas. The mean 60-day total precipitation before these five earthquakes is 98.8 mm, while the mean 60-day total post-event precipitation is 51.5 mm. Other atmospheric parameters show a similar trend. Detailed results using different time intervals and spatial resolutions support the precipitation enhancement before the major earthquakes in different spatial and temporal scales. Therefore, a positive meaningful relation seems to exist between earthquakes and precipitation before the main shocks ( R = 0.711). On this basis, atmospheric anomalies and precipitation enhancement are indicated, which include the appearance of cyclones that cause increased precipitation. This precursory phenomenon appears to be consistent with the Freund theory that specifically includes air ionization at the ground-to-air interface as a result of stress-activation of positive holes in the hypocentral rock volume, the spreading of these electronic charge carriers through the rock column, their arrival at the Earth’s surface, and air ionization.