A headline saying an earthquake was known about in advance might describe a long-term hazard assessment, an aftershock forecast or a message sent after a rupture began. Mixing these tasks creates the expectation of a precise timetable of future shocks. Here is what the scientific approaches can tell us and how that information can help.
A precise prediction and a probability answer different questions
Predicting a particular earthquake requires specifying its time, location and magnitude in advance. No reliable scientific method currently delivers that result. Saying a seismic region will experience a strong earthquake sometime does not solve the problem: without sufficiently defined conditions, there is no fair way to test whether the statement succeeded.
A probability estimate describes the chance of an event of a stated size within a defined area and period. An illustrative 20 percent chance over ten years does not mean an earthquake will occur in two years, nor does it guarantee quiet conditions in the other years. Such estimates support planning and risk reduction rather than assigning dates for a holiday or evacuation.
What an aftershock forecast can tell you
For selected significant earthquakes, USGS publishes forecasts of subsequent event counts and the probabilities of exceeding stated magnitudes within defined intervals. Models use the behaviour of earlier sequences and, as observations accumulate, the current sequence. A forecast therefore has an issue date, a period it covers and updates, rather than one permanently valid number.
Aftershock rates generally decrease over time, but individual events remain uncertain and can cause harm. If a larger earthquake follows, the earlier mainshock may be called a foreshock. A label on a map cannot identify it as such beforehand. The probability of further activity is not a timetable of safe hours for entering a damaged building.
Early warning begins after the earthquake starts
A dedicated earthquake early warning system detects an event that is already happening and rapidly estimates its location, size and expected shaking. Information can reach a more distant location before strong seismic waves do. That difference creates the potential time advantage: the system is not observing a future rupture before it occurs.
Near the source, an alert may arrive with the strong shaking, after it, or too late to be useful. Available time depends on station locations, processing, delivery and distance. No service can promise every user the same number of seconds. The word alert in a product name does not establish that it connects to an earthquake early warning system in your region.
What this app does
The app presents available USGS records from the past 24 hours and helps explain them. It does not predict the next earthquake, and the current version does not deliver background push warnings to phones. Refreshing a catalogue while an app is open and receiving a specialised warning before strong waves arrive are different technical processes with different requirements.
Its learning material includes 20 lessons and six types of models in 12 languages. Favourites, manually selected regions and the cache stay local; there are no accounts or advertisements. These features support learning and browsing. A saved card, a radius setting or an open map does not subscribe you to official emergency warnings or replace that subscription.
Check claims and prepare actions you can use
For a dramatic prediction claim, find the original publication from before the event, its stated location, time and magnitude, and the author's unsuccessful claims too. A screenshot edited after shaking does not demonstrate success. One match among numerous broad statements cannot establish a reliable method; testable results must include misses as well as apparent hits.
Useful preparation includes securing objects that could fall, agreeing how to contact family and practising protection during shaking. Indoors, get low, shelter under a sturdy table and hold on. At the coast after strong or long shaking, move to high ground or inland along local routes as soon as you can move safely. Do not wait for an app message.
- Precise prediction: when, where and how large will a particular future event be?
- Forecast: what is the probability within the stated area and period?
- Early warning: it has started; can information arrive before strong shaking here?
FAQ
Does a sequence of small earthquakes mean a large one is coming soon?
A sequence alone does not support that conclusion. Small events often do not lead to a larger earthquake. An event can be called a foreshock after a larger one occurs. Follow official information and maintain your usual preparedness.
Does receiving no warning mean there is no danger?
No. Coverage, communications and delivery time have limits. Protect yourself immediately if shaking starts. At the coast, respond to natural tsunami warning signs using local guidance without waiting for a message.
Sources
- USGS — Can You Predict Earthquakes?
- USGS — Early Warning, Forecasts, Probabilities and Prediction
- USGS — Aftershock Forecast Overview
- USGS — Earthquake Early Warning: Overview
- USGS — Earthquake Early Warning: Fine-Tuning for Best Alerts
- USGS — What Can I Do to Be Prepared for an Earthquake?
- USGS — What Should I Do During an Earthquake?
- NOAA/NWS — During a Tsunami
This is educational information. For emergency decisions, follow local authorities and official warnings.
