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Prompt gravity signal induced by the 2011 Tohoku-Oki earthquake

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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.

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The 2011 Tohoku-Oki earthquake and gravity changes recorded by the Kamioka superconducting gravimeter.(a) Seismic moment (dashed line) and moment rate (solid line) time-functions of the Tohoku-Oki earthquake12. (b) Locations of the epicentre (red star), the Kamioka Observatory (red circle) and its five nearest F-net seismic stations (blue circles). (c) Three days of gravimetric recording at Kamioka Observatory, starting on 9 March 2011.
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f1: The 2011 Tohoku-Oki earthquake and gravity changes recorded by the Kamioka superconducting gravimeter.(a) Seismic moment (dashed line) and moment rate (solid line) time-functions of the Tohoku-Oki earthquake12. (b) Locations of the epicentre (red star), the Kamioka Observatory (red circle) and its five nearest F-net seismic stations (blue circles). (c) Three days of gravimetric recording at Kamioka Observatory, starting on 9 March 2011.

Mentions: The 11 March 2011 Tohoku-Oki earthquake occurred off the Pacific coast of northern Honshu, Japan910. The rupture onset time is teq=05:46:21 UTC and the epicentre coordinates are 38.19° N, 142.68° E (ref. 11). The moment rate function12 has an overall duration of more than 2 min and reaches its maximum over about 1 min (Fig. 1a). Based on the theory developed by Harms, J. et al.8 (see also the ‘Discussion' section), we expect a prompt gravity signal amplitude of a fraction of μGal at ∼65 s after the rupture onset, just before the arrival of the seismic P-waves at the instruments.


Prompt gravity signal induced by the 2011 Tohoku-Oki earthquake
The 2011 Tohoku-Oki earthquake and gravity changes recorded by the Kamioka superconducting gravimeter.(a) Seismic moment (dashed line) and moment rate (solid line) time-functions of the Tohoku-Oki earthquake12. (b) Locations of the epicentre (red star), the Kamioka Observatory (red circle) and its five nearest F-net seismic stations (blue circles). (c) Three days of gravimetric recording at Kamioka Observatory, starting on 9 March 2011.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5121411&req=5

f1: The 2011 Tohoku-Oki earthquake and gravity changes recorded by the Kamioka superconducting gravimeter.(a) Seismic moment (dashed line) and moment rate (solid line) time-functions of the Tohoku-Oki earthquake12. (b) Locations of the epicentre (red star), the Kamioka Observatory (red circle) and its five nearest F-net seismic stations (blue circles). (c) Three days of gravimetric recording at Kamioka Observatory, starting on 9 March 2011.
Mentions: The 11 March 2011 Tohoku-Oki earthquake occurred off the Pacific coast of northern Honshu, Japan910. The rupture onset time is teq=05:46:21 UTC and the epicentre coordinates are 38.19° N, 142.68° E (ref. 11). The moment rate function12 has an overall duration of more than 2 min and reaches its maximum over about 1 min (Fig. 1a). Based on the theory developed by Harms, J. et al.8 (see also the ‘Discussion' section), we expect a prompt gravity signal amplitude of a fraction of μGal at ∼65 s after the rupture onset, just before the arrival of the seismic P-waves at the instruments.

View Article: PubMed Central - PubMed

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.

No MeSH data available.


Related in: MedlinePlus