Normal modes; investigating signal and noise phenomena across instrument types and deployment

Author(s): Hellweg, Margaret; Araki, E.; Rademacher, H.; Taira, T.; Uhrhammer, Robert A.; McGowan, M.
Author Affiliation(s): Primary:
University of California Berkeley, Seismological Laboratory, Berkeley, CA, United States
Other:
JAMSTEC, Japan
Guralp Systems, United Kingdom
Volume Title: AGU 2013 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2013; American Geophysical Union 2013 fall meeting, San Francisco, CA, Dec. 9-13, 2013. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: Whether a seismic signal in a certain frequency band can be detected in a recording depends primarily on four factors: the amplitude of the signal at the site, the conditions at the site which affect the ambient noise in that band, the sensitivity and self-noise of the sensor in the band, as well as the sensitivity and self-noise in the digitizer in the band. For the very long period band, between 1.0 and 5.5 mHz, the normal modes provide an excellent signal for exploring the effects of the latter three contributions, since after a large or great earthquake, their amplitudes are similar all over the earth. In the past, observatory equipment in an observatory setting were required to observe them. We observed normal modes in the 1.0-5.5 mHz band with good signal-to-noise ratio in the aftermath of the Mw 8.3 Sea of Okhotsk deep earthquake on 24 May 2013 at many stations of the Berkeley Digital Seismograph Network and at other stations in other networks. They are equipped with a variety of sensors, including those with a flat passband extending to frequencies lower than the normal modes, and digitizers. They are also deployed in a variety of geologic settings, including cabled ocean bottom stations, MOBB in California, from the Japanese cabled "Dense Ocean-Network for Earthquake and Tsunamis (DONET)" and the IODP seafloor borehole in the south of Japan. The sites have varying physical infrastructure and site preparation. We explore the factors contributing to the observation of the normal modes at a suite of amplitudes of excitation (based on several earthquakes of different magnitudes) to give different signal-to-noise ratios, and at the many different stations.
Year of Publication: 2013
Research Program: IODP Integrated Ocean Drilling Program
Key Words: 07 Marine Geology and Oceanography; Asia; Far East; Integrated Ocean Drilling Program; Japan; North Pacific; Northwest Pacific; Okhotsk Sea; Okhotsk earthquake 2013; Pacific Ocean; Seismicity; Signal-to-noise ratio; West Pacific
Record ID: 2015078164
Copyright Information: GeoRef, Copyright 2017 American Geosciences Institute. Reference includes data supplied by, and/or abstract, Copyright, American Geophysical Union, Washington, DC, United States

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