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Library API

dist/rumbleback.js (built from src/index.ts) exports the part of the page that has no DOM. It is plain ESM and runs in Node 22 or newer and in browsers. Types are in the TypeScript sources in src/core.

Travel times

import { TravelTimes } from './rumbleback.js';

const tt = new TravelTimes(40);        // source depth in km, 0 to 700
tt.time('P', 1.1);                      // seconds from origin to the first P arrival 1.1 degrees away
tt.time('S', 1.1);
tt.distanceAt('S', 20);                 // degrees the S front has reached after 20 s, or null while it is underground
tt.surfaceDelay;                        // { P, S }: seconds until each wave reaches the surface above the source

The values are the iasp91 first arrivals from ObsPy TauP. See ACCURACY.md for the error against TauP.

A pin and an alert

import { TravelTimes, timingAt, blindRadiusKm, distanceDeg } from './rumbleback.js';

const epicenter = [23.8356, 121.5976];
const tt = new TravelTimes(40);
const pin = distanceDeg(epicenter, [24.15, 120.67]);
timingAt(tt, pin, 10);   // { distanceKm, pSec, sSec, gapSec, warningSec, blind }
blindRadiusKm(tt, 10);   // km around the epicenter where S arrives before an alert 10 s after the origin

Geometry

distanceDeg, distanceKm, bearingDeg, destination, ring and wrapLon work on [lat, lon] pairs in degrees on a sphere of radius 6371.0088 km. ring(center, degrees, steps) returns [lon, lat] points of a circle of constant arc distance with longitudes unwrapped across the antimeridian.

Loading USGS data

import { loadQuake, pickResiduals, summarize } from './rumbleback.js';

const quake = await loadQuake('us7000m9g4');                  // summary, picks, ShakeMap, instruments, felt reports
summarize(pickResiduals(quake, 95).P);                          // { n, median, medianAbs, p90Abs }

loadQuake(id, onProgress?, fetch?, signal?) fetches the summary first and each layer on its own. A layer that is missing or fails leaves that part of the result empty. The parsers are exported on their own as parseSummary, parseProducts, parsePhaseData, parseGrid, parseStations and gridMmiAt, and searchQuakes and recentQuakes query the catalog (recentQuakes(fetch, signal, now, minMag) takes the minimum magnitude, 5 unless given, and returns at most RECENT_LIMIT quakes from the last RECENT_DAYS). eventIdFrom(text) finds the USGS event id in an id, an event page address or a catalog query, and returns null for anything else. A response that is not a success throws an HttpError with its status. encodeQuake and decodeQuake convert a loaded event to and from the compact JSON the featured shelf uses.

Seismogram

loadSeismogram(quake, picks) fetches the vertical seismogram of a nearby usable station, broadband channels first, from the EarthScope dataselect service as GeoCSV and condenses it. parseGeoCsv and condense are exported separately. The result is a Seismogram: the station, its distance, and a min and max per time bin scaled to -1000 to 1000.

Intensity helpers

mmiColor(mmi, alpha?), mmiRoman(mmi) and shaking(mmi) follow the USGS ShakeMap scale.