Table 3

Waveform‐ and Spectrum‐Based Features

NumberNameFormula
1DurationT=tets
2*MaxAmpA=max[|s(t)|]·1000
3*DurOverAmpT/A
4RappMaxMeanmax[e(t)]/mean[e(t)]
5RappMaxMedianmax[e(t)]/median[e(t)]
6*RappMaxStdmax[e(t)]/std[e(t)]
7AsDec(tmaxts)/(tetmax)
8KurtoSigKurt[s(t)]
9KurtoEnvKurt[e(t)]
10SkewSigSkew[s(t)]
11SkewEnvSkew[e(t)]
12CorPeakNumberNumber of peaks in a(τ)
13int_ratioEmbedded Image
14–18ES1 to ES5ESi=log10ei(t)dt
19–23KurtoF1 to KurtoF5Kurt[si(t)]
24MeanFFTmean[|S(ν)|]
25MaxFFTmax[|S(ν)|]
26FMaxFFTνmax
27MedianFFTmedian[|S(ν)|]
28VarFFTvar[|S(ν)|]
29FCentroidcentroid[|S(ν)|]
30Fquart1centroid[|S(ν)|1]
31Fquart3centroid[|S(ν)|3]
32NPeakFFTNumber of peaks in |S(ν)|>0.75|S(ν)|max
33MeanPeaksFFTmean[|S(ν)|at peaks]
34–37E1FFT to E4FFTEiFFT=∫|S(ν)|i
38gamma1Embedded Image
39gamma2Embedded Image
40gammasEmbedded Image

Description of terms: s(t) the windowed raw seismogram, e(t) its envelope, a(τ) its auto‐correlation function, si(t) the windowed seismograms filtered in the 0.1–1 Hz (i=1), 1–3 Hz (i=2), 3–10 Hz (i=3), 10–20 Hz (i=4), and 20–50 Hz (i=5) frequency bands, ei(t) their corresponding envelopes, ts and te the start and end times of the window, tmax the time of the peak amplitude, Kurt(X)=μ4(X)/σ4(X) the kurtosis of distribution X in which μ4(X) indicates the fourth moment of X and σ its standard deviation, Skew(X)=μ3(X)/σ3(X) the Skewness of distribution X in which μ3 indicates the third moment of X, S(ν) the fast Fourier transform of s(t), νmax the frequency at which |S(ν)| is maximum, and |S(ν)|i the ith quartile of |S(ν)|.

  • * Features not also used by Hibert et al. (unpublished manuscript, 2017; see Data and Resources).