Characteristics and Causal Mechanisms in Earthquake Precursors of the Ionospheric Plasma(2/3)

The project goal is to study the characteristics and find causal mechanisms of SIPs (seismo-ionospheric precursors) of the ionospheric plasma in various regions of the globe. The total electron content (TEC) of the global ionosphere maps (GIMs) constructed by worldwide ground-based GNSS (global gravitation satellite system) receivers and FORMOSAT-7 satellite observations are used to three dimensionally examine SIPs. The GIM TEC with the spatial resolution of 2.5-deg in latitude and 5.0-deg in longitude routinely published every 1-hour is ideal to observe temporal and spatial SIPs associated with global large earthquakes since. To monitor temporal SIPs in a certain region, the characteristics of the polarity (increase or decrease， positive or negative), appearance local time, duration period, lead day, etc. prior to previous large earthquakes should be statistically examined first. Later, when anomalies in the monitoring region meet the characteristics, it can consider that possible temporal SIPs have been detected. In addition to Taiwan, Indonesia, China, and Japan, this project will examine the temporal SIP characteristics associated with global large earthquakes by means of z-test statistical analyses in various regions since 2000. The receiver operating characteristic (ROC) curve is further applied to evaluate the efficiency of these temporal SIPs. To confirm the detected temporal SIPs, the global distribution of any anomalies meeting the characteristics criteria should be examined. When the anomalies consistently or frequently appear specifically around the monitoring region, it can consider that spatial SIPs have been detected, which most likely will be followed by possible large earthquakes. Once the area of the spatial SIPs being located, simultaneous observations of the electron/ion density/temperature and ion velocities over the area probed by satellites can be employed to find the causal mechanisms of the SIPs. Results of the temporal/spatial SIP analyses and the causal mechanism study shall shed some light on the earthquake/forecast.