dsh-quake-alert

LIMITATIONS

Known limitations

- The plugin runs with the DSH page: closing the page stops it, and browsers may throttle background tabs, delaying notifications. - Cancellation / clearance notices only fire for events that were previously alerted; a cancellation for an event you never saw stays in the history and does not interrupt you. - Tsunami forecasts (552) carry no mergeable event id, so successive releases of the same tsunami (added areas, upgraded grade) each notify. - With several DSH pages open, each page keeps **two** WebSocket connections of its own (P2PQuake and EMSC). Alerts are de-duplicated via BroadcastChannel, but the number of connections grows with the number of tabs — and P2PQuake enforces a concurrency limit, so opening a great many tabs deserves a thought. - Several DSH pages **share the same per-source cursors**: a telegram or earthquake already handled by one page is not replayed in another (cross-tab de-duplication only ever lets one page announce it). The trade-off is that a page opened or reloaded later does not add those already-consumed entries to its own "Recent alerts" list. - Hypocenter-only reports (551 "hypocenter information" / "distant earthquake") carry no intensity data and cannot be evaluated against thresholds; they are recorded in "Recent alerts" with an explanatory note. - System notification permission must be granted once via "Test system notification"; the alert tone requires one user interaction before the browser allows it (autoplay policy). - **Coverage**: Japanese earthquakes / EEW / tsunamis come from P2PQuake over a WebSocket, and weather alerts from the JMA's Atom feed (polled by the Host half about once a minute). Outside Japan, coverage comes from EMSC (live push), USGS (global catalog, polled by the Host every 2 minutes) and NOAA (tsunami CAP, polled every 5 minutes). Regional weather sources (the US NWS, Europe's MeteoAlarm, and so on) are planned for a later version. - **Global sources are coarser than Japanese ones**: they carry only an epicenter and a magnitude, with nothing down to the municipality; tsunamis are expressed as NOAA sea areas (such as `SCOTIA SEA`) rather than Japan's 津波予報区; and landslides / floods outside Japan have no ingestion channel yet. - **The same earthquake may be reported by both global sources**: if EMSC's and USGS's origin times fall on opposite sides of a minute boundary, the merge fails. The trade-off is deliberate — better to alert twice than to miss one. - **The EMSC connection does not use the "no data" check**: an M4+ event arrives roughly every 30 minutes worldwide, so silence says nothing about connection health. Real disconnects are still detected and reconnected. - Weather alerts are deliberately threshold-free: the cut-off is fixed at level 4, so there is no slider to tune — the switch is simply on or off. - The sandbox replays mostly small, low-intensity earthquakes, so long periods without a match under the default "intensity 4 or higher" threshold are expected.