Statistical analyses on the ionospheric total electron content related to M ≥ 6.0 earthquakes in China during 1998 - 2015

  • Author(s): Cheng-Yan Liu, Jann-Yenq Liu, Yuh-Ing Chen, Fei Qin, Wei-Sheng Chen, Ya-Qin Xia, and Zhi-Qiang Bai
  • DOI: 10.3319/TAO.2018.03.11.01
  • Keywords: Pre-earthquake ionospheric anomaly, Total electron content, z test, ROC curve, Logistic regression
  • The z test finds the characteristic of identifying PEIAs
  • ROC is employed to confirm that the PEIAs are reliable and useful SIPs
  • The PEIAstrength is proportional to the forthcoming earthquake magnitude

To verify the pre-earthquake ionospheric anomaly (PEIA), statistical analyses are implemented on the relationship between the total electron content (TEC) of global ionosphere map (GIM) and 62 M≥6.0 earthquakes in China during 1998-2015. A median-based method together with z test is employed to determine the criteria and/or characteristics of TEC anomalies related to earthquakes. It is found that the GIM TEC significantly decreases at 18:00-22:00 UT (universal time, post-midnight to pre-dawn) 4-5 days before 37 6.0≤M<6.5 earthquakes, at 01:00-04:00 UT (morning) 3-6 days before 18 6.5≤M<7.0 earthquakes, and 04:00-10:00 UT (pre-noon to afternoon) 3-5 days; but increases 08:00-12:00 UT (late afternoon to early evening), 18-20 daysbefore 7 M≥7.0 earthquakes. The receiver operating characteristic (ROC) curve is used to compare the TEC anomaly-based method with some competitive alternatives for predicting the earthquakes under study. We found, based on possible TEC anomalies,that the observed PEIAs are significantly earthquake-related. Moreover, the results ofregressionanalyses show that the PEIA strength is associated with the magnitude of earthquakes.

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