Comparing tiltmeters for crustal deformation measurement--a preliminary report

Area of Science:

• Geophysics
• Tectonics
• Instrument Science

Background:

• High-precision tiltmeters are crucial for measuring tectonic deformation.
• Instrument comparison is essential for validating measurement techniques.

Purpose of the Study:

• Compare the performance of four different tiltmeters over 1.2 years.
• Assess instrument suitability for measuring tectonic deformation.
• Identify effective measurement techniques and potential improvements.

Main Methods:

• Operated two Michelson-Gale fluid tiltmeters, one center-pressure tiltmeter, and one borehole tiltmeter.
• Collected 1.2 years of high-precision tilt data at Pinon Flat Observatory.
• Analyzed data for coherence and correlation with environmental factors (e.g., air temperature) at nontidal frequencies.

Main Results:

• Michelson-Gale instruments showed limited coherence at 2-4 day periods.
• Center-pressure tiltmeter correlated with air temperature over several days to weeks.
• The most stable instrument recorded a secular tilt rate of 0.28 μrad/a, potentially indicating real tectonic motion.

Conclusions:

• Instrument comparison identified varying levels of success in measurement techniques.
• Low-noise data likely requires complex and expensive instruments.
• Existing tilt sensors require further improvement for continuous tectonic motion measurement.