NHESS Natural Hazards and Earth System Sciences NHESS Nat. Hazards Earth Syst. Sci. 1684-9981 Copernicus Publications Göttingen, Germany 10.5194/nhess-13-2189-2013 Review Article: On the relation between the seismic activity and the Hurst exponent of the geomagnetic field at the time of the 2000 Izu swarm Masci F. https://orcid.org/0000-0003-2314-3023 1 Thomas J. N. 2 3 4 Istituto Nazionale di Geofisica e Vulcanologia, L'Aquila, Italy Northwest Research Associates, Redmond, Washington, USA Department of Electrical and Computer Engineering, Digipen Institute of Technology, Redmond, Washington, USA Department of Earth and Space Sciences, University of Washington, Seattle, Washington, USA 06 09 2013 13 9 2189 2194 Copyright: © 2013 F. Masci 2013 This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/3.0/ This article is available from https://nhess.copernicus.org/articles/13/2189/2013/nhess-13-2189-2013.html The full text article is available as a PDF file from https://nhess.copernicus.org/articles/13/2189/2013/nhess-13-2189-2013.pdf

Many papers document the observation of earthquake-related precursory signatures in geomagnetic field data. However, the significance of these findings is ambiguous because the authors did not adequately take into account that these signals could have been generated by other sources, and the seismogenic origin of these signals have not been validated by comparison with independent datasets. Thus, they are not reliable examples of magnetic disturbances induced by the seismic activity. Hayakawa et al. (2004) claim that at the time of the 2000 Izu swarm the Hurst exponent of the Ultra-Low-Frequency (ULF: 0.001–10 Hz) band of the geomagnetic field varied in accord with the energy released by the seismicity. The present paper demonstrates that the behaviour of the Hurst exponent was insufficiently investigated and also misinterpreted by the authors. We clearly show that during the Izu swarm the changes of the Hurst exponent were strongly related to the level of global geomagnetic activity and not to the increase of the local seismic activity.

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