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Mechanical monolithic horizontal sensor for low frequency seismic noise measurement
Fausto Acernese1, Gerardo Giordano, Rocco Romano
1Dipartimento di Scienze Farmaceutiche, Universita degli Studi di Salerno, Via Ponte Don Melillo Fisciano SA, Italy.
The Review of Scientific Instruments
|August 7, 2008
Summary
A new monolithic horizontal sensor for geophysical applications achieves a 70 mHz resonance frequency. This compact, sensitive instrument functions as a seismometer or accelerometer, demonstrating improved mechanics and optical readout.
Area of Science:
- Geophysics
- Mechanical Engineering
- Optical Sensing
Background:
- Geophysical applications require highly sensitive and robust sensors for detecting subtle ground motions.
- Traditional seismometers and accelerometers face limitations in compactness, sensitivity at low frequencies, and immunity to environmental noise.
Purpose of the Study:
- To describe a novel mechanical monolithic horizontal sensor for geophysical applications.
- To present improvements in the mechanical design and optical readout system of a tunable folded pendulum sensor.
- To validate the sensor's performance as both a seismometer and an accelerometer.
Main Methods:
- Precision machining and electric discharge machining for monolithic construction.
- Development of elliptical hinges and mechanical tuning for resonance frequency adjustment.
- Implementation of laser interferometric techniques and laser optical lever for readout.
- Theoretical modeling and experimental validation of sensor sensitivity.
Main Results:
- A compact, monolithic tunable folded pendulum sensor was developed.
- The sensor demonstrated high sensitivity in the low-frequency seismic noise band with good environmental noise immunity.
- Experimental measurements showed excellent agreement with theoretical sensitivity curves.
- A natural resonance frequency of 70 mHz with a Q factor of 140 was achieved in air.
Conclusions:
- The developed sensor is a compact and highly sensitive instrument for geophysical applications.
- The advancements in mechanical tuning and optical readout confirm the feasibility of millihertz resonance frequency sensors.
- The monolithic folded pendulum design offers a promising platform for next-generation seismometers and accelerometers.
