A study of ionospheric anomaly detection before the August 14, 2021 Mw7.2 earthquake in Haiti based on sliding interquartile range method

This study focuses on the possible ionospheric anomalies before the Mw7.2 earthquake in Haiti on August 14, 2021. Based on the dual-frequency observation data of Global Navigation Satellite System (GNSS) stations and Global Ionosphere Maps (GIM) data products, the sliding interquartile range method was applied to detect and analyze the changes of ionospheric Total Electron Content (TEC) anomalies before the earthquake. The results show that the TEC anomalies over five GNSS stations show the common existence of anomalous times, which are July 28, August 1, August 2, August 7, and August 13, 2021, respectively. Combining space weather parameters and GIM, it is tentatively concluded that the TEC anomaly that appeared on August 1 (i.e., the 13th day before the earthquake) was not disturbed by geomagnetic storms and solar activity, and may be related to the breeding earthquake. An ionospheric anomaly close to 6 TECU was present near the epicenter 13 days before the earthquake, which is strongly associated with the peak variation of the equatorial anomaly. This suggests that an anomalously increased vertical electric field may have been generated before the earthquake, which in turn enhanced the “fountain effect” and created a strong northern hump.