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Rapid estimation of earthquake magnitude from the arrival time of the peak high-frequency amplitude

Shunta Noda·Shunroku Yamamoto·William L. Ellsworth
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Abstract

We propose a simple approach to measure earthquake magnitude M using the time difference ( T op ) between the body‐wave onset and the arrival time of the peak high‐frequency amplitude in an accelerogram. Measured in this manner, we find that M w is proportional to 2log T op for earthquakes 5&le; M w &le;7, which is the theoretical proportionality if T op is proportional to source dimension and stress drop is scale invariant. Using high‐frequency (>2&thinsp;&thinsp;Hz) data, the root mean square (rms) residual between M w and M T op ( M estimated from T op ) is approximately 0.5 magnitude units. The rms residuals of the high‐frequency data in passbands between 2 and 16 Hz are uniformly smaller than those obtained from the lower‐frequency data. T op depends weakly on epicentral distance, and this dependence can be ignored for distances <200&thinsp;&thinsp;km. Retrospective application of this algorithm to the 2011 Tohoku earthquake produces a final magnitude estimate of M 9.0 at 120 s after the origin time. We conclude that T op of high‐frequency (>2&thinsp;&thinsp;Hz) accelerograms has value in the context of earthquake early warning for extremely large events.

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Shunta Noda, Shunroku Yamamoto, William L. Ellsworth. 2016-01-26. Rapid estimation of earthquake magnitude from the arrival time of the peak high-frequency amplitude. https://doi.org/10.1785/0120150108

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