Engineering a

one-second variometer for seismomagnetic





Climatology and Geophysical Agency Indonesia

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observations are made to record the variations of the geomagnetic all

components in a continuous manner. Tectonic activity causing

earthquakes resulted in changes in the geomagnetic field. Variometer

system engineering has been done with a sampling rate of 1 second at

Pelabuhan Ratu and Kupang station, then analysed recording on anomaly

during earthquake. The variometer recorded an anomalous change of

geomagnetic during an earthquake with magnitude 6.6 SR on October 19,

2016 at a depth of 614 Km with an epicentre location in the Java Sea

northeast direction which is 276 Km from Pelabuhanratu geophysical

station, the earthquake caused magnetic disturbance during 4 minutes

with a maximum amplitude of 40 nT (nanoTesla), and visible phase P and

S waves with a time difference of 1 minute. And the earthquake in

Flores on December 5, 2016 which magnitude 6.3 SR. Variometer at

Kupang geophysical station experience magnetic disturbance for 5

minutes with maximum amplitude of 20 nT, phase seismic waves P and S

visible on magnetic variation with difference time 50 seconds.

Anomalies are seen several hours before an earthquake showing the

variation pattern of X and Y components forming the same pattern, it

can be suspected as earthquake precursors.