seismographs [1]

Instruments that record seismic wave amplitude at a given point on the Earth’s surface.

vertical seismograph

Instrument that measures vertical ground movement.

vertical ground movement

bedrock

Extremely hard rock mass joined with the subsoil.

stand

Horizontal support that is secured to the ground.

pillar

Very solid vertical support.

mass

Independent of ground movement, it remains stationary during an earthquake, thus serving as a reference for measuring the amplitude of tremors.

spring

It keeps the mass from moving.

pen

Writing instrument that converts ground movement into a line.

rotating drum

Secured to the ground, it rotates under the pen, recording ground movements on paper.

seismogram

Graphic representation produced by a seismograph; the stronger the tremors, the greater the oscillations on the paper.