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. , 18 -20 days before 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 of regression analyses show that the PEIA strength is associated with the magnitude of earthquakes.

This paper presents a near real-time evaluation of earthquake hazard after the shallow M L 6.2 Hualien shock of depth 10.6 km occurred 2350 LT, 6 February 2018 at epicenter (24.10°N, 121.73°E). Since a large aftershock intends to bring up a new aftershock sequence, we develop a time-magnitude hazard function for the double aftershock sequences. Note that the double-sequence aftershock hazard model can be regarded as a generalization of the Reasenberg-Jones (RJ) model and hence is denoted by DSRJ. For a near real-time evaluation of the aftershock hazard in the golden window particularly for emergent rescue work, the DSRJ or RJ model is estimated based on early aftershock sequence and then the occurrence rate and number of the forthcoming aftershocks in 3 days after the Hualien main shock are forecasted. Results of a data analysis show that the DSRJ model is better than the RJ model on near real-time assessment of short-term aftershock hazard. This provides an evidence that the aftershocks occurred in a short time after the Hualien main shock may not be a single aftershock sequence.