Included in the supplemental material is a table of magnitude estimates for Quake-Catcher Network (QCN)-detected events at NT = 0.02, 1, 2, and 3 s after the trigger, compared to the reported GeoNet magnitude. There are also two plots to help clarify the simple linear fitting technique used to calculate the Chung et al. revised magnitude scaling relationship.
Table S1. Estimated QuakeCatcher Network values and GeoNet-reported magnitudes. All events are listed by event ID (Unix timestamp) with estimated QCN values calculated at NT = 0.02, 1, 2, and 3 s. GeoNet-reported magnitudes during the period of interest are predominantly measures of local magnitude (ML), although Geonet implemented a combined summary magnitude (M) at the beginning of 2012. New summary magnitudes are reported for only 25 of the 185 earthquakes listed in the supplementary event table, hence the scaling relationship can be assumed to be based on ML (but is not fully evaluated for other magnitude types).
Figure S1. The normalized, unitless, three-component vector sum acceleration values (PNT) from Figure 2 of the main article are plotted versus magnitude bin and grouped by distance and NT (number of seconds after the trigger). For clarification, the arrows in the 5–7.5 km bin here correspond to those in the 5–7.5 km bin in Figure 2. Slopes and intercepts were calculated for each distance and time bin and are shown in Figure S2.
Figure S2. The slope and intercept values from Figure S1 are plotted versus distance. The slopes are overall very consistent for different NT values. (a) and (b) The best linear fits to the data are calculated (see examples of best-fit lines for NT= 3 s in red) and used to create the lower two plots (c and d). The best fitting lines are calculated and used to create the Chung et al. revised magnitude scaling relationship (see main article for details).
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