Seismograph: Vibration Log

Turn your iPhone into a vibration recorder: live 3-axis waveform, automatic capture of shaking events, and a log you can replay and export.

HOW IT MEASURES
Shaking is read from the accelerometer and reported as peak ground acceleration, then mapped to the Modified Mercalli Intensity scale (MMI I-XII) using the USGS ShakeMap relationship. MMI is the primary scale because it is the one a phone can honestly produce — it describes how strongly a place shook. A magnitude-style number is shown alongside as a rough estimate; it is not a Richter measurement, which needs a calibrated instrument and the distance to the epicentre.

AUTOMATIC CAPTURE
Leave the app open and the phone resting on a solid surface. When shaking persists past the trigger threshold the app records the waveform, timestamps it, and files it in the event log with its peak acceleration and MMI level. Brief knocks and picking the phone up no longer create events.

Monitoring runs while the app is open — including while you read other tabs — and holds the screen awake while the alarm is armed. iOS does not let an app like this listen in the background, so it cannot watch while the phone is locked or while you use other apps. It is a monitoring station you set down, not a background alarm.

WHAT YOU GET
• Live 3-axis waveform with three sensitivity presets
• Event log with waveform replay
• Peak acceleration and MMI for every event
• On-screen alarm with vibration for stronger events, while monitoring
• CSV export per event, or the whole log
• Recent earthquakes feed for context

PLACEMENT MATTERS
Rest the phone on a table or floor. An accelerometer cannot tell ground motion from the motion of a hand carrying it — that is why real seismometers are anchored to the ground.

WHO USES IT
Anyone curious how much a passing train, washing machine or construction site actually shakes a building · people in seismic areas who want a record of what they felt · physics and earth-science teaching

Available in 25 languages.