Lithosphere ionosphere coupling associated with three earthquakes in Pakistan from GPS and GIM TEC

摘要

Total Electron Content (TEC) derived from satellite-based measurements has been widely used for the detection of ionospheric perturbations associated with earthquakes. In this paper, we analyze Pre-Earthquake Ionospheric Anomalies (PEIAs) with TEC data from Global Positioning System (GPS) stations in two Pakistani regions, Islamabad (33.74 degrees N, 73.16 degrees E) and Multan (30.26 degrees N, 71.50 degrees E). These stations operate within seismogenic zones of three earthquakes in Pakistan and Tajikistan. We implement a statistical technique on daily TEC for the detection of PEIA. The results show that PEIAs appear in the form of enhancement during 08:00-12:00 UT (LT = UT+5 h) within 5-10 days before the mainshock. Global Ionospheric Maps (GIMs) over the epicentre are examined on abnormal TEC days. Dense electron enhancements occur during 08:00-12:00 UT, i.e. before three M-w 5.0 earthquakes. Diurnal mean TEC deviates on the suspected days. It supports the anomalous signatures observed in the temporal and spatial distributions during the particular days. The geomagnetic and solar indices show no activity. These results endorse the existence of Lithosphere Atmosphere Ionospheric Coupling (LAIC) mechanism within the earthquake preparation period associated with the Pakistan and Tajikistan earthquakes.