Earth Tremors Observation by a Diamagnetic Levitation Based Inertial Sensor

This paper introduces a prototype of a diamagnetic levitation based inertial sensor which includes the diamagnetic levitation system and the optical displacement transducer. The proof mass is a floating magnet which is lifted by a fixed magnet above and sandwiched by two pyrolytic graphite sheets for stable levitation. A high precision optical displacement transducer has been developed with a noise floor of 1 nm/√Hz@1 Hz at atmosphere and room temperature. The fundamental frequency of the levitation system was measured as 0.65 Hz, giving an acceleration noise floor of 20 ng/√Hz@0.5 Hz. Benefitting on the excellent sensitivity and low-frequency responses, earth tremors at 0.2~0.3 Hz and 2~3 Hz have been observed using this inertial sensor.