Technologies 2014, 2(3), 115-128; doi:10.3390/technologies2030115
Crustal Strain Observation Using a Two-Color Interferometer with Accurate Correction of Refractive Index of Air
1
National Institute of Advanced Industrial Science and Technology, 1-1-1, Umezono, Tsukuba, Ibaraki 305-8563, Japan
2
Earthquake Research Institute, University of Tokyo, 1-1-1, Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan
*
Author to whom correspondence should be addressed.
Received: 30 April 2014 / Revised: 23 June 2014 / Accepted: 24 June 2014 / Published: 4 July 2014
(This article belongs to the Special Issue Precision Measurements and Metrology Using Lasers)
Abstract
A highly accurate two-color interferometer with automatic correction of the refractive index of air was developed for crustal strain observation. The two-color interferometer, which can measure a geometrical distance of approximately 70 m, with a relative resolution of 2 × 10−9, clearly detected a change in strain due to earth tides in spite of optical measurement in air. Moreover, a large strain quake due to an earthquake could be observed without disturbing the measurement. We demonstrated the advantages of the two-color interferometer in air for geodetic observation. View Full-TextKeywords:
two-color interferometer; heterodyne interferometer; refractive index of air; distance measurement; strain observation
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Telada, S.; Araya, A.; Takamori, A. Crustal Strain Observation Using a Two-Color Interferometer with Accurate Correction of Refractive Index of Air. Technologies 2014, 2, 115-128.
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