Aerosol anomalies associated with occurrence of recent strong earthquakes (> M 8.0)

  • AOD spatial anomalies occurred around eight recent strong earthquake epicenters
  • AOD temporal anomalies (>3.0) appeared before all eight strong earthquakes
  • AOD values increased, decreased, increasing again before returning to normal levels
Abstract

To promote understanding of lithospheric–atmospheric interactions during seismic activity, this study investigated the spatial and temporal variations of aerosol optical depth (AOD) associated with eight recent strong earthquakes (EQs; Mw >8.0), with focal depths of less than 30 km. All EQs occurred after 2009 and therefore have AQUA satellite moderate-resolution imaging spectroradiometer data for the EQ-affected areas. The purpose of this study was to extract aerosol anomalies before and after large EQsalong the coastline.Spatially, AOD anomalies occurred around the EQ epicenters at a monthly scale. Their duration prior to the EQ was typically longer than after the EQ, which may be related to the variation in ground stress. Generally, AOD spatial variations increased, then decreased, again increasing before at last returning to normal levels over an 8-d time frame around each event. Temporally, at an annual scale, high anomalous AOD values (>3.0) appeared before all eight strong EQs, with high frequencies of anomalous AOD values occurring both prior to and after EQs. Compared with control values, AOD values within affected areas showed an abnormal uplift and downtrend before each EQ event. The AOD values over the control pixels were significantly lower than those over the selected AOD anomaly pixels during the same periods.To eliminate the potential bias from satellites, the result of AERONET daily average AOD data at 500 nm showed that a sudden increase of AOD appeared before and after EQs. AOD anomalies occurred before, during, and after each of the eight strong EQs in offshore regions, partially because of the release ofsurface latent heat and related atmospheric reactions that increased aerosol concentrations, excluding the effects of the wind filed near the earth. The mechanisms behind these AOD anomalies still need to be identified.

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