Local magnitude (ML) to report for every event
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1. Remove the instrument response (stations.xml) to ground displacement and simulate a
   Wood-Anderson torsion seismometer: poles -6.283 +/- 4.7124j rad/s, two zeros at 0,
   static magnification 2080.
2. On each horizontal channel (..E/..N) within 150 km hypocentral distance, measure the
   peak absolute Wood-Anderson amplitude A (mm) between 1 s before the P arrival and 10 s
   after the S arrival. If the next earthquake's P wave reaches that station earlier, end
   the window 0.5 s before that P arrival (and skip the channel if the window then ends
   less than 0.5 s after the S arrival).
3. Channel magnitude: ML_ch = log10(A) + 1.110*log10(r/100) + 0.00189*(r - 100) + 3.0
   (Hutton & Boore, 1987), with r the hypocentral distance in km,
   plus the channel correction listed in ml_corrections.csv.
4. Event ML = median of the corrected channel magnitudes.
