The instrument that records vibrations in the Earth's crust is a seismograph. It detects ground motion caused by earthquakes and other seismic sources, then produces a record called a seismogram.
A seismograph typically uses a sensor and a relatively stationary mass. When the ground moves, the instrument's frame shifts around the mass, allowing the motion to be measured. Modern instruments record the data digitally, while older versions traced movement on paper.
The terms seismometer and seismograph are often used interchangeably, although a seismometer technically refers to the sensing instrument, while a seismograph includes the recording system. Scientists study the resulting wave patterns to locate earthquakes, estimate their strength, and understand Earth's interior.