Real-Time Detection of Ionospheric Disturbances Induced by Earthquake with Detection Window Considering Ionospheric Activity

The free electrons in the ionosphere affects the transmission of GNSS signals and its effect can be observed as an ionospheric delay. To improve positioning accuracy, ionospheric delay needs to be estimated and eliminated from the measurement. The accurately estimated ionospheric delay can also be used to monitor the activity of the Earthquake. The waves generated by the Earthquake propagates through the atmosphere and it can cause disturbance in the ionosphere. This disturbance can be observed in the ionospheric delay estimated by using GNSS measurements. This study focuses on the automatic detection of the ionospheric disturbance associated with Earthquake. The Earthquake induced perturbation is persisted for a while and it is the major discriminative feature against the nominal ionospheric delay and the other anomalies such as cycle slips. Using these intrinsic characteristics from the Earthquake, we propose detection criteria of the Earthquake induced ionospheric disturbance. We also propose computation method of false alarm rate with regards to the proposed detection criteria. GPS data collected at 3 IGS stations in Japan and 44 permanent stations in South Korea are used to analyze the ionospheric disturbance due to the Earthquake and to validate the performance of the detection criteria for 2011 Tohoku Earthquake event. Using the proposed detection criteria, detection was successful at 38 stations while it was the case for only 14 stations without the proposed criteria.