Study of aerosol anomaly associated with large earthquakes (M > 6)

Abstract

We present the variation of unusual atmospheric phenomena, aerosols, to understand the preseismic irregularities for two major earthquakes in Japan. We consider aerosol optical depth and Angstrom exponent data retrieved from the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument onboard the Terra satellite to establish possible connections between earthquakes and the gen eration of aerosols. Variation of the aerosol parameters shows significant changes before the April 15, 2016, Kumamoto earthquake (M ¼ 7:0; h ¼ 10 km) and the November 21, 2016, Fukushima earthquake (M ¼ 6:9 and h ¼ 9 km), where M indicates the Richter mag nitude and h indicates the focal depth. To identify the source of the aerosol particles, we use the Hybrid Single-Particle Lagrangian Inte grated Trajectory model (HYSPLIT-4). This model uses both Lagrangian and Eulerian approaches to compute trajectories and establish a source-receptor relationship. We compute backward trajectories to check whether the aerosol generated near the epicenter is due to the preseismic processes or is transported from other areas. From our results, we conclude the fine-mode aerosols are generated in the vicin ity of the epicenter, 3–7 days before the earthquakes.