Prompt gravity signal induced by the 2011 Tohoku-Oki earthquake

Creators: Montagner, Jean-Paul; Juhel, Kévin; Barsuglia, Matteo; Ampuero, Jean Paul; Chassande-Mottin, Eric; Harms, Jan; Whiting, Bernard; Bernard, Pascal; Clévédé, Eric; Lognonné, Philippe

Abstract

Transient gravity changes are expected to occur at all distances during an earthquake rupture, even before the arrival of seismic waves. Here we report on the search of such a prompt gravity signal in data recorded by a superconducting gravimeter and broadband seismometers during the 2011 Mw 9.0 Tohoku-Oki earthquake. During the earthquake rupture, a signal exceeding the background noise is observed with a statistical significance higher than 99% and an amplitude of a fraction of μGal, consistent in sign and order of magnitude with theoretical predictions from a first-order model. While prompt gravity signal detection with state-of-the-art gravimeters and seismometers is challenged by background seismic noise, its robust detection with gravity gradiometers under development could open new directions in earthquake seismology, and overcome fundamental limitations of current earthquake early-warning systems imposed by the propagation speed of seismic waves.

Additional Information

© 2016 The Author(s). This work is licensed under a Creative Commons Attribution 4.0 International License. The images or other third party material in this article are included in the article's Creative Commons license, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons license, users will need to obtain permission from the license holder to reproduce the material. Received: 25 January 2016; Accepted: 26 September 2016; Published online: 22 November 2016. We are grateful to Yoshiaki Tamura (GGP Datacenter, Japan) for providing gravimetric data, Severine Rosat (EOST, Strasbourg, France) for technical discussions, NIED for providing F-net seismic data and Shengji Wei (Earth Observatory of Singapore) for providing an updated moment rate function. This work was supported by the NSF Grants PHY 0855313, PHY 1314529 and PHY 1205512 to UF. J.-P.M. acknowledges the financial support of Institut Universitaire de France. B.W. acknowledges sabbatical support from the Université Paris Diderot and CNRS through the APC, where part of this work was carried out. J.P.A. acknowledges support by a grant from the Gordon and Betty Moore Foundation to Caltech. K.J. is supported by a PhD fellowship of programme IDEX-USPC 'Double Culture'. We acknowledge the financial support from the UnivEarthS Labex programme at Sorbonne Paris Cité (ANR-10-LABX-0023 and ANR-11-IDEX-0005-02) and from the Agence Nationale de la Recherche through the grant ANR-14-CE03-0014-01. Author Contributions: J.-P.M. and M.B. conceived the data analysis study. J.-P.M. conducted the preliminary data analysis. M.B. and K.J. conducted the blind data analysis. J.P.A. and J.H. developed the comparison to theory. E.C. and P.L. contributed to preliminary stages of the comparison to theory. All authors (except E.C. and P.L.) contributed to the analysis and interpretation of results and participated in writing the manuscript. Data availability: The data from the superconducting gravimeter of Kamioka Observatory are publicly accessible from the Global Geodynamics Project web site (http://www.eas.slu.edu/GGP/tohoku2011.html) or upon request to Yoshiaki Tamura. The F-net seismic data are available on the web site: http://www.fnet.bosai.go.jp/waveform/?LANG=en. All codes were written for this study and a copy of the data are available on GitHub at the following URL: https://github.com/kjuhel/prompt-gravity. The authors declare no competing financial interests.

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