How Does a Seismometer Work?

A seismograph is a device for measuring the movement of the earth, and consists of a ground-motion detection sensor, called a seismometer, coupled with a recording system. This fact sheet provides an overview of the basic components of a seismometer and physical science principles behind its operation.

How are Earthquakes Located?

We can locate earthquakes using a simple fact: an earthquake creates different seismic waves (P waves, S waves, etc.) The different waves each travel at different speeds and therefore arrive at a seismic station at different times. P waves travel the fastest, so they arrive first. S waves, which travel at about half the speed of P waves, arrive later. A seismic station close to the earthquake records P waves and S waves in quick succession. With increasing distance from the earthquake the time difference between the arrival of the P waves and the arrival of the S waves increases.

Case Study
China, Southern Qinghai
Magnitude 7.3
A magnitude 7.3 earthquake jolted China’s sparsely populated Qinghai province in the northwest. There were no immediate reports of casualties or damage from the remote area.

SEP Seismometer System
Our Seismometer in collaboration with DIAS (Dublin Institute for Advanced Studies) is part of a global seismic network. The core work is to apply geophysical data analysis, computation and methodological developments to gain new insights into Earth processes at a range of temporal and spatial scales.

The SEP Seismometer System uses the same basic principle underlying all seismometers, which is that of inertia–seismic waves from an earthquake make the ground move relative to the recording device. In the case of the SEP seismometer, there is a large mass on the end of a boom: this stays where it is as the ground moves beneath the seismometer, and this relative movement is recorded.