Fig. 5.From: Initial 30 seconds of the 2011 off the Pacific coast of Tohoku Earthquake (Mw 9.0)—amplitude and τ c for magnitude estimation for Earthquake Early Warning—Frequency spectra of the vertical acceleration recorded at MYGH12 for the Mw 9.0 event (left), and Mw 7.3 event (center), and the ratio of the two spectra (right) derived from time windows corresponding to tN = 10 s (light gray), 20 s (dark gray) and 30 s (black). Waveforms are shown at the top.Back to article page