Low‐Frequency Tilt Seismology with a Precision Ground‐Rotation Sensor
We describe measurements of the rotational component of teleseismic surface waves using an inertial high‐precision ground‐rotation sensor installed at the Laser Interferometer Gravitational‐Wave Observatory (LIGO) Hanford Observatory (LHO). The sensor has a noise floor of 0.4 nrad/√Hz at 50 mHz and a translational coupling of less than 1 μrad/m enabling translation‐free measurement of small rotations. We present observations of the rotational motion from Rayleigh waves of six teleseismic events from varied locations and with magnitudes ranging from M 6.7 to 7.9. These events were used to estimate phase dispersion curves that show agreement with a similar analysis done with an array of three STS‐2 seismometers also located at LHO.
© 2017 Seismological Society of America. Published Online 15 November 2017. This work was carried out at the Laser Interferometer Gravitational‐Wave Observatory (LIGO) Hanford Observatory (LHO) by members of LIGO laboratory and the LIGO Scientific Collaboration including University of Washington, Seattle, and Harvard University. LIGO was constructed by the California Institute of Technology and Massachusetts Institute of Technology with funding from the National Science Foundation (NSF) and operates under Cooperative Agreement PHY‐0757058. Advanced LIGO was built under Award PHY‐0823459. This document has been assigned LIGO Laboratory document number LIGO‐P1700149. Participation from the University of Washington, Seattle, was supported by funding from the NSF under Awards PHY‐1306613 and PHY‐1607385. The authors would like to thank the LHO staff for their assistance with the installation and maintenance of the sensors. The authors are also grateful for the useful comments and suggestions by Jan Harms and for the many thought‐provoking discussions with our colleagues in the Eöt‐Wash Group. Additionally, the authors thank the Center for Experimental Nuclear Physics and Astrophysics (CENPA) for use of its facilities and Brian Lantz for the useful MATLAB scripts. The data and analysis used in this article can be found at https://dcc.ligo.org/LIGO-P1700149/public (last accessed August 2017).
Published - srl-2017148.1.pdf