­—xkcd, years before Brainstorm existed

How Brainstorm works

Brainstorm gets earthquake information from mainly two types of sources: posts on Twitter, and official reports by various geophysical agencies. Some specific Twitter accounts are monitored by Brainstorm for messages in a standard format, and these are generally in turn provided by geophysical agencies, while other tweets are simply received from accounts of people tweeting about an earthquake they felt.

This is how the Twitter analysis works in detail:

• Twitter has a streaming API that the bot queries to receive all tweets containing one among a list of keywords (at most 400 can be specified); any tweet containing any of those keywords is delivered in real time.
• Brainstorm opens the stream with a list of the word "earthquake" translated into all many major world languages, so any tweet containing the equivalent word to "earthquake" will be received; it also listens for specific Twitter accounts expected to send messages in a known format.
• It discards most of those tweets, and only keeps the ones that contain geolocation information in some shape or form: some of them are directly geolocated by Twitter (e.g. ones sent from mobile devices), for others the location is determined from the user's profile, and for some a name of a city can be found in the tweet itself. Brainstorm tries all these options in order of preference, and if none works, then it forgets about that specific tweet.
• If the tweet can be geolocated, it makes sure the "earthquake"-like word it contains actually matches the language the tweet is written in (Twitter tells you which language the tweet is in, so that's easy), so that false positives from the word for "earthquake" in one language meaning something very common in another language are avoided
• Then, Brainstorm assigns a "score" to the tweet based on several factors: for instance, if the tweet is short, its score is higher, and it's also higher if it is in capitals or contains exclamation marks, while if it contains a URL or a magnitude, that likely means it refers to an earthquake that happened in the past, so the score is lowered. Other heuristics are used.
• If the tweet is from a monitored account, then instead of assigning scores heuristically, an exact time, location and magnitude are read from the tweet text itself and considered more authoritative.
• Eventually, Brainstorm creates a preliminary "report" of a potential earthquake based on the tweet, if conditions are satisfied.
• If multiple tweets with overlapping locations in their "reports" add up to a certain score, then that is considered an "event", with epicenter in the central location of the recorded tweets, and a very inaccurately guessed magnitude and felt radius based on the presence or absence of further keywords ("strong", "weak", "terrible", etc).
• Events above a certain magnitude, or located in certain areas, or meeting other criteria, are sent to different internet locations (various IRC channels, Twitter, Matrix and Reddit). Brainstorm decices whether to send a simple "Preliminary" report, or an "earthquake warning", by estimating when the earthquake actually took place based on the first tweet seemingly referring to it, and on whether the guessed magnitude would make it plausible for some people who will be affected by the earthquake to have yet to be reached by its S-waves.
• For users that Brainstorm knows the location of (based on manual input, or their Twitter profile), a private message is also sent on IRC, Matrix and Twitter if they are deemed to have felt or be about to feel the tremors.

It is simpler to process data from official sources, as the main concern is just to disseminate the same event once even if multiple sources report it multiple times, unless its estimated parameters have considerably changed:

• Several geophysical institutes are monitored, using RSS feeds, or FDSN / QuakeML feeds, or (only in one case, at the time being) GeoJSON websockets, which, unlike the former two options, permits realtime monitoring (similar to the Twitter streaming API, but less centralized) instead of only periodic queries.
• When a new event is recorded from a source, it is immediately assigned to a report that has a score of 1, meaning it will be disseminated immediately, unlike tweets which have much lower scores until enough of them have been received to assume a valid event has occurred.
• These sources normally provide explicit information about time and place coordinates, depth, and magnitude, so these are used directly, and a report is considered part of a previous event, and not disseminated again, unless some of these parameters deviate considerably.
• Some sources also provide a level of alert (green, yellow, amber or red) based on the estimated impact on populations, and these are reported as new information when they change.

Brainstorm also adds some information of its own, which mainly consists of data elaborated from OpenStreetMap:

• coordinates-to-toponym resolution, including a database of Flinn-Engdahl regions
• amount of people likely affected, based on the estimated felt radius
• any nuclear reactors in the felt radius of the earthquakes
• webcams reported as providing real-time imagery in the earthquake area
• whether the earthquake occurred on the land or in the sea, and whether the magnitude and depth are likely to generate a tsunami, which is disseminated as a separate warning