Seismo ionospheric anomalies in Turkey associated with M_w ≥ 6.0 earthquakes detected by GPS stations and GIM TEC

摘要

Earthquake (EQ) anomalies in the form of enhancement and depletion in ionospheric Total Electron Content (TEC) from Global Positioning System (GPS) may considerably alarm about short and long term precursors of the impending main shock. In this paper, TEC anomalies are investigated from permanent GPS ground-stations in Turkey associated to M_w ≥ 6.0 EQs occurred in 2011-2012. Temporal and spatial analyses of TEC at 2 h sampling have shown significant evidences about EQ induced ionospheric anomalies during 10-14 h of UT (Universal Time) within 5 days before M_w. 6.0 Greece, and M_w 7.1, Turkish EQ. Spatial analyses have manifested arrival of TEC anomalies at UT = 10 h to epicenter of both EQs, which linger above epicenter during UT = 12-14 h and left seismogenic zone after UT = 14 h before every EQ during K_p ＜ 3 and Dst = 0 nT. Meanwhile, a geomagnetic storm (Dst ＜ -100 nT) induce perturbation two days after the M_w 7.1 Turkish EQ, showing no relation with epicenter during spatial analysis. It also shows that TEC can be useful to distinguish geomagnetic storm variations to successfully detect EQ precursors. These anomalies during quiet storm (K_p ＜ 3; Dst = 0 nT) conditions may be effective to link the lithosphere and ionosphere in severe seismic zones to detect EQ precursors before future EQs. Interpretation of TEC anomalies and it enhancements over EQ epicenters during UT = 12-14 h for both EQs have shown that EQs anomalies only occurred in particular time. Whereas, geomagnetic storm effect occurred during whole abnormal day over the Earth.