Focus (hypocenter)The rock first breaks here, on the fault. Scientists call it the hypocenter; focus is the older name.
EpicenterThe epicenter is on the ground directly above the focus. It is the place a map shows for an earthquake.
FaultA break along which blocks of rock on either side have moved. The surface they slip on is also called the fault plane.
Fault scarpA fault scarp looks like a step in the land. It is made by slip on the fault.
FootwallThe footwall lies under the fault. In this earthquake it stayed higher.
Hanging wallThe hanging wall lies over the fault. Here it has dropped, which makes this a normal fault.
Seismic wavesWhen the fault slips, the stored energy moves outward in all directions. It moves as seismic waves, like ripples on a pond.
SeismographIts base is fixed in the ground. A heavy weight hangs free. The record it writes is a seismogram, shown in the second view.
On the record 3
P wavesThe fastest seismic waves, so they reach a seismograph first. P stands for primary.
S wavesS waves are slower than P waves, so they arrive second. S stands for secondary. The gap between the two tells how far away the earthquake was.
Surface wavesThey travel along the ground, more slowly than P and S waves. They usually shake the hardest.
How this list was compiled: Every term checked on 2026-09-30 against the U.S. Geological Survey: the Earthquake Hazards Program glossary (hypocenter or focus, epicenter, fault, fault plane, fault scarp, seismic waves, body and surface waves), https://www.usgs.gov/glossary/earthquake-hazards-program; The Science of Earthquakes (fault, hypocenter, epicenter, seismic waves, P and S waves, seismograph and seismogram), https://www.usgs.gov/programs/earthquake-hazards/science-earthquakes; Seismographs: Keeping Track of Earthquakes, https://www.usgs.gov/programs/earthquake-hazards/seismographs-keeping-track-earthquakes; and the USGS block diagram of a normal fault (hanging wall and footwall), https://www.usgs.gov/media/images/normal-fault. Second reference: Wikipedia, Epicenter, Hypocenter, Fault (geology), Fault scarp, Seismic wave and Seismometer, text only. Licence: own work
The drawing: Drawn for this site on 2026-09-30 from plain geometry; nothing traced. The record is a drawing, not a real seismogram. Licence: own work
How it works
An earthquake diagram without labels, to print and fill in by hand. Eleven parts wait for a name: eight on the block of ground cut open along a fault, three on the record of the shaking under it.
Read the full guide
Word bank for the eleven parts
In alphabetical order: epicenter, fault, fault scarp, focus, footwall, hanging wall, P waves, S waves, seismic waves, seismograph, surface waves. Accept hypocenter for focus and seismometer for seismograph: the US Geological Survey uses both pairs.
Two drawings, two tasks
The block takes eight names and can be handed out alone: fold the sheet between the drawings. The record takes the three kinds of wave, which are told apart only by their order and size from left to right, so it works as a second, harder task. Footwall and hanging wall have no line: write each name on its block.
Fault and fault plane are one answer here: both words name the surface the blocks slip on.
Questions and answers
What type of fault is on the earthquake diagram?
A normal fault. The break is inclined, and the rock above it, the hanging wall, has moved down. Had the rock above the fault moved up, it would be a reverse fault.
How do scientists find the epicenter of an earthquake?
From the gap between the P waves and the S waves on a seismogram, which tells how far away the earthquake was. A circle of that distance is drawn round each of three seismographs, and the circles cross at the epicenter.
What are foreshocks and aftershocks?
Smaller earthquakes in the same place as the largest one, the mainshock. Foreshocks come before it; aftershocks follow and can continue for weeks, months or years. They are events, not parts, so the sheet has no line for them.
What is the difference between magnitude and intensity?
Magnitude is the size of the earthquake, read from seismograms, and each earthquake has one. Intensity is how strong the shaking is, and it varies depending on where you are.