Abstract
On April 20th, 2013, a strong earthquake (Ms 7.0, depth of 13 km) occurred in LuShan County, Southwestern Sichuan province, China, followed by a series of aftershocks (Ms = 3.0∼5.4). Infrasonic waves associated with the earthquake were detected and recorded by a digital infrasound recording system in our lab located in Chengdu city. Fourier analysis was used to determine the amplitude and frequency characteristics of each infrasonic recording. A certain frequency distribution range was clearly identified in the spectrograms of all analyzed shocks. Furthermore, a logarithm regression relation is also found between aftershock magnitude and peak value of corresponding infrasound events in amplitude spectra based on analysis results of more than 30 observed events. This study presents a data set and an empirical relationship. This relationship requires additional testing with observations from other earthquake aftershock sequences. These results improve our understanding of local infrasound produced by the coupling of earth surface motion to the atmosphere.