Ionospheric total electron content (TEC) variations estimated from dual-frequency receivers of global positioning systems (GPS) can be used as a tool to detect possible seismo-ionospheric anomalies before strong earthquakes. In this study, possible seismo-ionospheric anomalies before the 2018 Papua New Guinea earthquake (6.0684°S, 142.7678°E, February 25, 2018, 00:44:43 UTC, Mw = 7.5) was investigated by using GPS-TEC variations from four International GNSS Service (IGS) stations (KAT1, TOW2, SOLO and ALIC) near the epicenter and four IGS station (USUD, SHAO, WIND and ZAMB) outside of the EPZ. The earthquake (EQ) is a local phenomenon and space weather conditions (SWCs) are a global phenomenon so that we selected four IGS stations away from the earthquake epicenter, which is at the same latitude and the same longitude with the earthquake to figure out a clear SWCs' effects on the GPS-TEC anomalies. In order to see these effects on ionospheric TEC variations, 10 different SWC indices were used. An analysis of occurrence time and duration of the following conclusions was made: both positive and negative anomalies are ensuing, and earthquake-related ionospheric anomalies revealed that they occurred 1 to 7 days before the associated earthquake. At the end of the study, the potential causes of these results were examined. Analysis results revealed that anomalies occurred, and the possible ionospheric GPS-TEC anomalies may be the earthquake precursors obtained 4 to 9 days before the Papua New Guinea earthquake. The increase in scientific research to analyze the seismo-ionospheric anomalies that occur before earthquakes will become an important warning tool to alert people to the devastating environmental effects of earthquakes.
Keywords: Earthquake; GNSS; GPS-TEC; Ionosphere; Papua New Guinea; Space weather conditions.