improvised seismograph

Earthquakes generate seismic waves which can be detected with a sensitive instrument called a seismograph. Advances in seismograph technology have increased our understanding of both earthquakes and the Earth itself.

Seismic waves are the vibrations from earthquakes that travel through the Earth and they are recorded. Seismographs record a zigzag trace that shows the varying amplitude of ground oscillations beneath the instrument. Sensitive seismographs, which greatly magnify these ground motions, can detect strong earthquakes from sources anywhere in the world. The time, location and magnitude of an earthquake can be determined from the data recorded by seismograph stations. The sensor part of a seismograph is referred to as the seismometer, the graph capability was added as a later invention.

The goal of a seismograph is to accurately record the motion of the ground during a quake. If you live in a city, you may have noticed that buildings sometimes shake when a big truck or a subway train rolls by. Good seismographs are therefore isolated and connected to bedrock to prevent this sort of "data pollution." The main problem that must be solved in creating a seismograph is that when the ground shakes, so does the instrument. Therefore, most seismographs involve a large mass of some sort. You could make a very simple seismograph by hanging a large weight from a rope over a table. By attaching a pen to the weight and taping a piece of paper to the table so that the pen can draw on the paper, you could record tremors in the Earth's crust (earthquakes). If you used a roll of paper and a motor that slowly pulled the paper across the table, you would be able to record tremors over time. However, it would take a pretty large tremor for you to see anything. In a real seismograph, levers or electronics are used to magnify the signal so that very small tremors are detectable. A big mechanical seismograph may have a weight attached that weighs 1,000 pounds (450 kg) or more, and it drives a set of levers that significantly magnify the pen's motion.

Improvisation makes use of materials available at hand. In making an improvised seismograph, a heavy block of wood was used as a base in which a weight made of steel is attached to a rod using a commercial spring. The weight holds the pen which touches the rolled machine paper. However, movements must be intentionally executed because the paper is attached to a winding motor which needs to be switched on for the paper to unroll.

This improvised seismograph was made not to store any data of an earthquake. It intends only to demonstrate the features and functions of a real one.