Abstract
The geomagnetic field at the earth’s surface changes over time, including in Indonesia. An accurate regional geomagnetic model is needed. Indonesia conducted just 49 repeat station measurements (out of 68) in epoch 2020.0 due to the COVID-19 pandemic. The regional geomagnetic field was modeled using the collocated cokriging (CC) method, which is proven to be accurate. The results show high accuracy with 1.18 minutes root mean square error (RMSE) for the declination component (D), 11.1 minutes for the inclination component (I), and 36.6 nT for the total intensity component (F). This RMSE indicates a similar result to epoch 2015.0. It is apparent that the problem of fewer data for epoch 2020.0 has been solved using the CC method. The crustal geomagnetic fields are also modeled by combining repeat station data and an enhanced magnetic model (EMM). The crustal field model illustrates that 94% of repeat stations exist in the low values, contributing to global geomagnetic modeling in the future. The low crustal field values have also correlated with great earthquake epicenters (magnitude ≥6). The earthquakes occurred in the crustal field values under 120 nT from 2010 to 2020.
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