Tune Your Earthquake Alerts: Radius, Magnitude, and Community Levels Explained

Every earthquake app eventually collects the same two complaints: "it never tells me anything" and "it won't stop buzzing." Same app, different needs — an alert that's precious to one person is noise to the other. The only honest fix is control, and this post is the owner's manual for the controls.

Here's the one fact that makes GeoShake's notification settings make sense: every alert we send comes from one of three distinct streams — official agency catalogs, community felt reports, and our own seismometer network — and each setting governs a specific stream. There is no master volume knob, and that's deliberate. Once you know which lever moves which stream, nearly every "why did I get this?" puzzle solves itself.

By the end you'll know why a 1,000 km radius doesn't flood your phone, why an alert can occasionally arrive below your minimum magnitude on purpose, why the highest community tier refuses to be muted — and you'll leave with three ready-made setups to copy.

The one-minute mental model

Three streams, thirty seconds. Official catalog alerts are earthquakes published by official agencies — USGS globally, AFAD for Türkiye — reviewed, authoritative, and minutes behind the shaking. Community alerts form when several people in the same area independently report feeling an earthquake within a short time window. GeoShake network events are detections by our own hardware seismometer network, pushed within seconds of multi-station confirmation. The full tour, including why one data source deliberately never notifies anyone, is in part one of this series.

Now the master key. Each setting on the notifications screen governs a specific stream, ignores the others, and the ignoring is as intentional as the governing:

That table is the whole post in miniature. The rest walks it row by row — including the honest edge cases most apps would rather not write down.

Alert Radius: two conditions, not one

Alert Radius looks like the simplest control in the app: a slider from 10 to 1,000 km, drawing a circle around your set location. The intuitive reading — "alert me about earthquakes inside this circle" — is close but only half the rule, and the missing half is what makes a generous radius safe to use.

Geographically targeted alerts — both official catalog events and GeoShake network events, which share the same delivery mechanism — are matched to you in two parts. Part one is your circle: the radius you chose, around the location you set. Part two belongs to the earthquake: from its magnitude and depth we estimate its felt area — the region where its shaking is actually noticeable. A modest quake projects shaking a few dozen kilometers; only strong earthquakes push their felt area out to hundreds (we cap the estimate at 500 km). You receive the alert when the quake's felt area overlaps your circle — and both conditions must hold. Your circle has to reach toward the quake, and the quake's shaking has to reach toward you.

Which is why setting 1,000 km does not mean signing up for spam. A small quake far beyond your circle never reaches you, however generous your slider is: your circle stops where you drew it, and a small quake's felt area is only tens of kilometers wide — for small events, the quake has to happen more or less inside your circle to alert you at all. The overlap cuts the other way too, and this direction you want: a genuinely large earthquake can meet your circle from beyond it, its felt area bridging the gap. A big radius doesn't buy noise; it buys reach for events that deserve it.

Two things this slider deliberately does not govern. First, community alerts: those are delivered based on your proximity to the actual shaking cluster, independent of your slider — if people right around you are reporting shaking, you're relevant, whatever the slider says. Second, Global Notifications: enabling that toggle adds a worldwide stream that intentionally ignores radius — worldwide is its entire purpose. It's filtered by magnitude instead, which brings us to the next lever.

Minimum Magnitude: what it filters and what it doesn't

The tempting mental model is absolute: "no alerts below M3.0, ever." The truthful version depends on which stream the alert came from — and the differences are deliberate, so here they are, spelled out.

In the worldwide stream, your threshold is law. With Global Notifications on, catalog events — and network events that carry a preliminary magnitude, the ~M with its own story — are filtered strictly by your Minimum Magnitude. And network detections that failed our quality gates, the ones carrying no magnitude at all, never enter the worldwide stream in the first place. That's by design: the worldwide stream is organized around magnitude, and an event without one has nothing to be filtered by — so it stays regional.

In the local stream — inside your Alert Radius — the honest answer has two layers. The first is a floor: catalog events below M2.0 are never pushed at all. That floor sits on the network side, before any phone is involved — the smallest catalog entries can't buzz anyone. The second layer is your own threshold, and here's the part we'd rather tell you than have you discover: the app applies it whenever it's open. In the background, the local stream errs on the side of delivery.

The reasoning is worth stating plainly, because it's a trade we made on purpose. A quake inside your radius is one you may physically feel seconds after the notification arrives. Suppressing that alert at the exact moment the app can't consult your preferences is the wrong direction to fail in. So the local stream fails loud rather than silent — and if that occasionally means a small nearby quake slips through below your threshold, we'll take that trade every time. (If you've read the countdown post, you know what those seconds can be worth.)

Network events behave the same way — with one addition. When an event carries no ~M, there's nothing to compare against your threshold, so it isn't magnitude-filtered at all. It carries pure measurements instead: how many stations detected it, and an intensity class derived from actual measured ground acceleration (PGA).

And community alerts? They ignore this setting entirely — they measure what people felt, not what instruments assigned. They answer to exactly one control, and it gets its own section.

Community Alert Level: II+, V+, VI+

This setting governs the community reports stream only — it has no effect on catalog or network alerts. It's the most misunderstood control in the app, because people expect a master severity dial. It isn't one. It's the volume knob for a single stream: alerts generated when multiple people's "I felt an earthquake" reports cluster together.

Each community alert carries the cluster's average reported intensity, and your level selects the minimum severity you'll receive:

• All reports (II+) — every confirmed cluster, including mild shaking that most people barely notice.
• Urgent and above (V+) — clearly-felt shaking and stronger.
• Critical only (VI+) — strong shaking only.

The Roman numerals are intensity levels — how strong the shaking felt where people stood, not the earthquake's magnitude. And one standing reassurance: a single report never becomes an alert — reports only alert others after clustering in space and time and passing anti-noise scoring. One tap can't page a city, a rule part one unpacks in full.

Now the asymmetry, printed right on the settings screen: "Critical alerts (VI+) cannot be disabled." Whatever level you choose, critical community alerts are always delivered, on the mute-piercing channel. That deserves an explanation, because it's the only place in the app where your preference loses. You picked your level on a calm day, months ago, possibly annoyed by that morning's notification. A critical alert describes strong shaking, confirmed by multiple people, happening near you right now. A warning that can be silenced by yesterday's annoyance isn't a warning — it's a suggestion. For that one tier, we decided it must stay a warning.

Three setups that work

There's no correct configuration — there's the one that matches how much you want to hear from the planet. Three honest starting points:

Quiet is for the notification-averse: you'll hear about earthquakes big enough to matter in your region, community events people clearly felt — and little else. The tradeoff is curiosity: the small tremor two towns over won't reach you. The floors still hold — a quake right next to you errs toward delivery, and critical alerts always arrive. Quiet, not deaf.

Balanced is the app's defaults with one nudge — magnitude raised from 2.0 to 3.0. Most people should start here: wide awareness of your region without the smallest catalog entries. The tradeoff is the occasional alert for a moderate quake you never feel.

Everything is for the enthusiast, the researcher, the sensor host who wants the planet's pulse in their pocket. With Global Notifications on and the threshold at 2.0, your notification tray becomes a seismology feed — that is the tradeoff, and it's the point. Worth knowing: the same Minimum Magnitude filters the worldwide stream too, so raising that one value calms both streams at once.

The safety floor

Everything above is a per-stream lever, and you're meant to pull them hard — that's what they're for. But notice what sits beneath every combination: critical community alerts always get through, even past mute. A nearby quake in the background errs toward delivery rather than silence. However you tune it, you can make GeoShake quiet — you cannot accidentally configure it into silence about strong shaking near you. That floor isn't a setting, and it's the one thing we'd never hand over.

This post closes the series. Part one mapped the three streams behind every alert; part two followed the countdown and its five-second honesty gate; part three told the story of the ~M tilde. This one handed you the levers. If you're newer to the physics underneath it all, our earthquake early warning guide is the natural next read.

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