Pre-seismic ionospheric anomalies and spatio-temporal analyses of MODIS Land surface temperature and aerosols associated with Sep, 24 2013 Pakistan Earthquake

摘要

This study aims to investigate the behaviors of the potential earthquake precursors such as Total Electron Content (TEC), daytime/nighttime Land Surface Temperature (LST) and aerosols before and after the 2013 Mw 7.7 Awaran (Pakistan) earthquake. TEC values were obtained from Global Positioning System (GPS) measurements, and LST and aerosol values were retrieved from Moderate Resolution Imaging Spectroradiometer (MODIS) instrument aboard the Terra and Aqua satellites, respectively. In order to detect the anomalies, moving median method was used in TEC analyses and +2 sigma (95% confidence level) interval was utilized in LST and Aerosol Optical Depth (AOD) analyses as anomaly indicator. TEC anomalies were identified 3 days (21.09.2013) and 5 days (19.09.2013) before the earthquake. In daytime/nighttime LST analyses, three regions of interest for spatial analyses were determined including epicenter, 10 km impact area around the epicenter and Modified Mercalli Intensity (MMI) 7.5 contour which was presented in the United States Geological Survey (USGS)'s shake map. Different anomalous days of LST were observed from these three regions of interest. In AOD analysis, only MMI 7.5 contour was considered due to its low spatial resolution (10 x 10km pixel size). The anomaly in AOD values was observed on 29.09.2013, 5 days after the earthquake. However, the abnormal behavior of AOD on 21.09.2013 was consistent with GPS-TEC anomaly. Furthermore, considering daytime/nighttime LST values on epicenter and 10 km impact area, we observed a systematic increase culminated near the earthquake event and a decrease after the earthquake. On the contrary, a systematic decrease and then increase of the AOD values were identified. The obtained results showed that TEC, LST and AOD were important potential precursors for Earthquake prediction; however, further developments on methods, data types and statistical analyses are still required.