A ShakeMap estimates how strongly the ground shook across a region after an earthquake. Learn what the colours, legend and parameters mean, and what a ShakeMap cannot tell you.

Earthquake magnitude vs intensity explained: one number for the size at the source, many intensity values for the shaking felt in each place.

What is an earthquake epicenter? Learn how it differs from the hypocenter, how seismologists locate it, and why shaking is not always worst there.

How deep can earthquakes occur? Most are shallow, but some start about 700 km down in sinking plates. Learn the depth classes and why depth matters.

Is a 4.0 earthquake strong? Learn how a magnitude 4 feels, how far it is felt, how often it happens and why it rarely causes damage.

What real-time earthquake notifications really mean, how fast data arrives, why magnitudes change, and how to set thresholds that avoid alert fatigue.