What Is an Earthquake?
The mechanics of how rock stores and releases strain, what seismic waves actually do, and why identical magnitudes can produce wildly different damage.
Read the guide →Earthquake Guides
17 reference guides covering how earthquakes happen, how magnitude and depth are measured, what generates a tsunami, how aftershock sequences behave, and what actually works for preparedness. Written to sit alongside the live catalogue, so the science and the data explain each other.
Basics
The Earthquake Magnitude Scale Explained
Why a magnitude 7 is not "slightly worse" than a magnitude 6 but roughly 32 times more energetic, and why the Richter scale is no longer used for large events.
Read the guide →Earthquake Depth Explained
Depth is the most underrated number in an earthquake report. It often decides whether a given magnitude is harmless or catastrophic.
Read the guide →How Earthquakes Are Measured
From the physics of a seismometer to how a global network pins down an epicentre within minutes.
Read the guide →Depth
Shallow Earthquakes Explained
About three quarters of all earthquakes are shallow, and almost every destructive earthquake in history has been one.
Read the guide →Intermediate-Depth Earthquakes Explained
Events between 70 and 300 km deep trace subducting plates, and behave very differently at the surface from shallow ruptures.
Read the guide →Deep-Focus Earthquakes Explained
They should be physically impossible, they reach magnitude 8, and they break almost nothing. Deep-focus earthquakes are the strangest category in seismology.
Read the guide →Science
Plate Tectonics and Fault Types
Earthquakes are not scattered randomly. Their distribution traces plate boundaries almost exactly, and the boundary type determines the maximum size possible.
Read the guide →Aftershocks and Foreshocks Explained
Aftershock sequences follow remarkably predictable statistical rules, even though no individual aftershock can be predicted.
Read the guide →Earthquakes and Tsunamis
Only a specific combination of magnitude, depth and fault motion produces a tsunami — and the natural warning signs matter more than the official ones if you are close.
Read the guide →The Pacific Ring of Fire
A 40,000 km chain of subduction zones and transform faults rimming the Pacific, responsible for nearly every magnitude 9 in recorded history.
Read the guide →Can Earthquakes Be Predicted?
No method has ever reliably predicted a specific earthquake in advance. Probabilistic forecasting and early warning, however, both work and both save lives.
Read the guide →Soil Liquefaction Explained
One of the most destructive secondary earthquake hazards, and one of the most predictable — liquefaction susceptibility can be mapped before any earthquake occurs.
Read the guide →Safety
Earthquake Safety: What To Do During an Earthquake
Official guidance, why two widely repeated pieces of advice are actively dangerous, and what to do in each situation you might be in.
Read the guide →Earthquake Preparedness: Kit and Home Checklist
Preparedness is the one earthquake response that reliably works, because it does not require knowing when.
Read the guide →Earthquake Early Warning Systems
Not prediction — a race between electrons and seismic waves that an earthquake already underway can lose.
Read the guide →Reference
The Largest Earthquakes in Recorded History
The largest magnitudes ever measured, what they had in common, and why magnitude ranking and death-toll ranking are almost entirely different lists.
Read the guide →Where to start
If you are new to the subject, read what an earthquake is first, then the magnitude scale and why depth matters. Those three cover almost everything needed to read an earthquake report properly.
If you live somewhere seismically active, the two that matter most are what to do during an earthquake and how to prepare in advance — including two pieces of widely repeated advice that are actively dangerous.