
A comparison of tauc and taupmax for magnitude estimation in earthquake early warning
JangTian Shieh
YihMin Wu
National Taiwan University
Richard M. Allen
University of California, Berkeley
Geophys. Res. Lett., 35, L20301, doi:10.1029/2008GL035611, 2008.
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ShiehWuAllenGRL2008.pdf
Abstract
We determined the tauc and taupmax parameters from the KNET strong motion records of 16 earthquakes in Japan with moment magnitude (Mw) ranging from 6.0 to 8.3. A 0.075 Hz highpass Butterworth filter was applied for determination of tauc based on our previous studies. It was found that different pole selections of the Butterworth filter lead to different uncertainty in magnitude determination. Our results show that using two poles in the filters results in the best magnitude estimates i.e. minimized the standard deviation in magnitude determination in comparison to Mw using tauc . The taupmax parameters (Allen and Kanamori, 2003) were also determined with the same dataset using the Wurman et al. (2007) procedure. It was found that taupmax values obtained from this dataset, and using the Wurman procedure, had a larger uncertainty. However, when a 0.075 Hz highpass Butterworth filter with five poles was added, the uncertainty in taupmaxderived magnitude estimates decreased minimizing the standard deviation in magnitude determination using taupmax . This difference in the behavior of tauc and taupmax can be used to further reduce the uncertainty in rapid magnitude determination for earthquake early warning. When the magnitude estimations from tauc and taupmax of each event are averaged to provide a new magnitude estimate, the standard deviation in magnitude estimates is reduced further to 0.27 magnitude units.
© Richard M Allen
