 |
 |
 |
 |
|
|
A seismometer detects the seismic waves that shake the ground, and a seismograph records the shaking as a zigzagging line called a seismogram. The technology is nothing new, but it has come a long way:
 |
 Seismograph drums were used from the late nineteenth century until the 1990s. When the earth moves, a weighted pen leaves a zigzagging line (seismogram) on a rotating, paper-covered drum (seismograph). The height of the zigzag reflects how much shaking took place—a visual record of an earthquake's magnitude.
|
|
Broadband digital seismometers are how scientists gather earthquake data today. Electronics record the data on ground movement and transmit it to computers all over the world. Solar panels power the devices so they can be used in the field for years to come. |
The Richter Scale
In 1935, Dr. Charles Richter developed a numeric magnitude scale to measure the amount of energy an earthquake released. The 1906 San Francisco earthquake is estimated today at magnitude 7.8. Small earthquakes of less than magnitude 1 happen every day; the largest quake ever recorded (off the coast of Chile on May 22, 1960) had a magnitude of 9.6.
Though people still refer to the “Richter scale,” more advanced scales are now in use. But no matter what the scale, geologists determine an earthquake’s magnitude by looking at the size of the seismogram it made. The larger the seismogram, the greater the shaking; the greater the shaking, the greater the magnitude.
Continue to Locating Earthquakes. >>
|
|
|
 |
|
 |
|
