Identification of anomalies of ultra low frequency (ULF) emission and total electron content (TEC) as earthquake precursor in Moluccas sea region

Abstract

Stress accumulation in lithosphere may produce fractures and it can cause alteration in electric field influencing magnetic field around earthquake preparation zone especially at low frequency range (ULF). Through the fractures also may release charged particles toward atmosphere and disturbing the electron content (TEC) in ionosphere. This research aims to identify the anomalies that appear before earthquake occurred by using geomagnetic data from MAGDAS (Magnetic Data Acquisition System) station in Manado. The geomagnetic data is analyzed by using polarization of Z/H component method and Single Station Transfer Function (SSTF) method. Meanwhile, total electron content data is obtained from Global Ionospheric Maps (GIM) network and analyzed by using correlation technique. This research detects the emergence of anomalies in geomagnetic field and total electron content from 7 earthquakes occurred in Moluccas sea region with magnitude ≥ 5 Mw from June 2016 to February 2017. ULF anomaly emerges between 1 day until 26 days before earthquake event and TEC anomaly emerges from 1 day to 19 days before earthquake event. The anomaly emergences are validated by Disturbance Storm Index (DST Index) to confirm that those detected anomalies are not caused by magnetic storm.