This electronic supplement consists of three tables containing supporting data. Table S1 lists the parameters of 31 calibration earthquakes as obtained from the Advanced National Seismic System (ANSS) Comprehensive Catalog (ComCat) (see Data and Resources). Table S2 lists both ComCat earthquake parameters and the ElarmS-2 v.2 algorithm output for all real-time detections with a ComCat event match. Table S3 contains a summary of ElarmS-2 performance for calibration events before and after adjusting configuration.
A subset of the parameters that can be retrieved from the E2 logfiles is compiled in Table S2 for each detection. Some ElarmS-2 detections (in particular single-station ones) may be matched to the wrong ComCat event. Many detections are due to very small events, and many detections did not result in an alert. This is the full set of events from which Figures 8b and 10a,b of the main article can be reproduced by filtering out detections without alerts and very small magnitude events. Split events can be identified by comparing the ComCat Event ID to the E2 Event ID; all ComCat Events that have more than one E2 Event ID were split into distinct ElarmS-2 solutions, although they may not all have resulted in an alert (in Fig. 8b of the main article, only those split events that resulted in more than one alert are shown. If only a single alert was sent, the split events are included in Fig. 10a of the main article). If an alert was sent for an earthquake, there may be several alert sequence numbers for that event: ElarmS-2 will send updates when new channels have been associated with the event (all triggers are assumed to be P picks), which channels were added can be determined by comparing the trigger sequence number to the alert sequence number. The table also contains enough information to compare alert times to origin times and P-wave arrival times (trigger times). However, because we are improving our seismic network rapidly for earthquake early warning (EEW) purposes, these delay times are already no longer representative for its current configuration. Therefore, we did not want to draw too much attention to them in this article.
Note: The E2 magnitudes reported in Table S2 cannot be directly compared with Figure 7 of the main article because, during our real-time testing period, several different magnitude relations were used. For Figure 7 of the main article, we calculated magnitude from log10(Pd) measurements using equation (1) of the main article and the correct epicentral distance. When ElarmS-2 location is very poor, the magnitude estimate will also be poor, because the wrong epicentral distance will be used.
Table S1 [Plain Text Comma-separated Values; 3 KB]. Parameters of 31 calibration earthquakes as obtained from ANSS ComCat. Column headings are self-explanatory (origin time in yyyy-mm-dd hh:mm:ss.sss format).
Table S2 [Plain Text Comma-separated Values; 1.2 MB]. Parameters of real-time ElarmS-2 detections with a ComCat event match.
Explanation of Table Columns
Alert sent?: Boolean, “True” if ElarmS solution sent an alert
ComCatID: event ID from the ANSS Comprehensive Catalog
Origin Time: origin time from ComCat in yyyy-mm-dd hh:mm:ss.ssssss format
longitude (E): longitude from ComCat in °E
latitude (N): latitude from ComCat in °N
depth (km): depth from ComCat
catalog magnitude: preferred magnitude from ComCat
E2id: ElarmS event ID
Alert sequence number: ElarmS iteration-solution for which an alert was sent (remains 0 if no alert was sent)
E2 longitude (E): ElarmS-2 longitude in °E
E2 latitude (N): ElarmS-2 latitude in °N
E2 magnitude: magnitude as reported by ElarmS (see Note)
Origin Time Error (s): E2 origin time − ComCat origin time
Mislocation (km): |E2 location − ComCat location|
Magnitude Error: E2 magnitude − ComCat magnitude
Alert-time: time first alert was sent (yyyy-mm-dd hh:mm:ss.ssssss format_
Alert-time (seconds since ComCat origin time): alert time − origin time
Alert-time (seconds since this trigger): alert time − trigger time
trig-seq: alert sequence number for which this trigger was included
trig-sta: station code
trig-chan: channel code (broadband, HHZ, BHZ; strong motion, HNZ, ENZ)
trig-lat: latitude of station
trig-lon: longitude of station
trigger time: time of trigger at station in yyyy-mm-dd hh:mm:ss.ssssss format (assumed to be P wave)
Table S3 [Plain Text Comma-separated Values; 7 KB]. Comparison of ElarmS-2 performance for calibration events before and after adjusting configuration. Origin time error, mislocation, and magnitude error are defined as the difference between the initial ElarmS-2 solution and the catalog value. For example, a magnitude error of −1.7 means that the initial ElarmS-2 estimate of the magnitude was 1.7 magnitude units smaller than the catalog magnitude. Catalog origin time is given in mm/dd/yyyy hh:mm format.
Earthquake parameters were obtained from the Advanced National Seismic System (ANSS) Comprehensive Catalog (ComCat), available from http://earthquake.usgs.gov/fdsnws/event/1/ (last accessed May 2016).
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