Development of low-frequency electromagnetic disturbance monitor for seismic observation

Abstract

Electromagnetic disturbance is an effective means of observing earthquake precursors. As one kind of key device for capturing electromagnetic disturbances, induction magnetometers are widely used with the characteristics of high sensitivity, large dynamic range and wide frequency band. However, various instruments have different frequency bands, inconsistent observation frequency bands，and different usage fields. There are few instruments that meet the needs of observing low-frequency electromagnetic disturbances for seismic stations. In this paper, an observation system for earthquake low-frequency electromagnetic disturbance monitor is composed of integrating the self-developed inductive magnetic sensors and data acquisition system. Firstly, the system composition of the electromagnetic disturbance monitor was explained. The working principle of the sensor, the test methods and results of sensitivity, consistency and noise were then introduced. Combined with the installation and observation of the electromagnetic disturbance monitor at seismic stations, the observation data were finally analyzed and studied. The results show that the performance of the electromagnetic disturbance monitor is in compliance with related technical requirements. The sensitivity of the magnetic sensor is better than 50 mV/nT (0.01～10 Hz). The correlation coefficient are all greater than 0.95. The noise can reach 0.15 pT/√Hz@1 Hz in the test. Various electromagnetic disturbance events can be clearly captured in the daily observations, which verifies the feasibility of the developed electromagnetic disturbance monitor for station observation.

Keywords

• electromagnetic disturbance
• magnetic sensor
• test method
• observation test