Seismology Instruction with the AS 1

   Computer Display

     The computer display showing the real time data does not need to be close to the 

seismometer.  The AS 1 is shipped with a 7 m (22 ft) paired shielded coaxial cable.  This cable 

length can be increased, allowing freedom of placement.  We have purchased a 21.5 m (70 ft) 

cable from a local electronics store and used it without loss of signal.  If a replacement cable 

is used, a connector end will need to be soldered to the replacement cable (also available from 

most electronics stores).  Ideally, place the computer display in a prominent location either a 

classroom or public area where data can be monitored.

Seismology Overview 

     Earthquakes are caused by the sudden movement of blocks of the Earth's crust.  Such 

movement involves the fracture of brittle rocks and the movement of rock along the fractures.  

A fracture in a rock along which movement occurs is called a fault.  

     When an earthquake occurs, it releases energy in the form of waves that radiate from the 

earthquake source in all directions. The different types of energy waves shake the ground in 

different ways and also travel through the earth at different velocities.

   The fastest waves, and therefore the fi rst to arrive 

at a given location, are P waves (Primary waves) or 

compressional waves.  Like sound waves, they move 

by alternately compressing and expanding material 

in the direction of motion.

   The next signifi cant waves to arrive are the S 

 waves 

(Secondary waves).  They travel through 

the earth moving material up and down and side 

to side  perpendicular to the direction on motion.

   The last to arrive are Surface waves, which 

travel slower than P and S waves and move the 

ground like a rolling ocean wave (Rayleigh) or side 

to side like a S wave (Love).

AmaSeis Version 1.0 Level 2005.05.19

1.2