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Amplitude and Q of ₀S₀ from the Sumatra Earthquake as Recorded on Superconducting Gravimeters and Seismometers

The first 20% of the full text of this article appears below.

	INTRODUCTION

 
It has been known for some time that superconducting gravimeters (SGs) can provide excellent recordings of the seismic normal modes. Studies by Banka and Crossley (1999) and van Camp (1999) established the low noise level of SGs in the seismic normal mode band, especially at periods longer than 100 s. In an extensive study of all the currently operating SGs (about 18), Rosat et al. (2003) showed that the best SGs have lower noise than the New Low Noise Model (Peterson 1993) at periods longer than 1,000 s. Also, several studies have compared the performance of SGs and broadband seismometers at long periods and shown that the correction of meteorological influence on the SGs can be more effective than on seismometers (Freybourger et al. 1997; Hinderer et al. 2002). Zürn and Widmer-Schnidrig (2006) demonstrated the need to correct seismometers for pressure effects at long periods. In the frequency domain the sensitivity of SGs reaches 1 nanogal (10^–11ms^–2) or less, especially at periods longer than 100 s. Widmer-Schnidrig (2003) summarized the advantages of using SGs for long-period seismology, noting that in addition to sensitivity the SGs are calibrated to DC with an amplitude accuracy of better than 0.1%. Here we combine and compare, for the first time, seismic data from the Incorporated Research Institutions for Seismology (IRIS) Data Management System and data from SGs contributing to the Global Geodynamics Project (GGP) (Crossley et al. 1999).

The 26 December 2004 Sumatra earthquake is the largest event to be recorded both by the Global Seismographic Network (GSN) and SGs, with a magnitude larger than 9.0. It therefore provides a very good opportunity to test the calibration levels of our instruments (Davis et al. . . . [Full Text of this Article]

Earth and Atmospheric Sciences
Saint Louis University
Saint Louis, Missouri 63108 USA
yxu3@eas.slu.edu
(Y. X.)