Seismology Instruction with the AS 1

Selecting a Gain

     The Gain setting adjusts the amplifi cation of the signal and an appropriate value for 

this setting varies with the location of the seismometer.  The goal is to minimize noise while 

highlighting any earthquakes that the AS 1 records.  Often the best strategy is to watch 

carefully for the fi rst earthquake, if the event is barely or not visible adjust the gain to a higher 

value.  If the event seems to take over the screen, adjust the gain to a lower value.  Since this 

setting only affects how data is displayed on the screen and  does not effect the data values 

that are stored on disk, try multiple values to compare the earthquake signal with background 

noise.  Selecting an appropriate gain maximizes the instructional value of the instrument.  A 

few examples are listed below to help select a starting value.

THAZ   Gain 35

This instrument is located in a science storeroom in the back of a classroom at Tempe 

High School in Phoenix, Arizona.  It is on the ground fl oor of a one story building.  

This school is in downtown Tempe and the classroom is about 60 meters from a 

 four lane 

street.

WGCO   Gain 50

This instrument is located on top of a small wooden cabinet which is situated in the 

back of the entry level conference room of the USGS National Earthquake Information 

Center in Golden, Colorado.  This is a concrete slab building with three fl oors above 

and one below the entry level.

PCAZ   Gain 25

This instrument is located on the fl oor next to the wall in a classroom of Phoenix 

Country Day School in Paradise Valley, Arizona. The teacher had a small piece of 

carpet removed so that the AS 1 sits on concrete.  The classroom is on ground fl oor of a 

one story building.  There is a small surface street 25 meters north of the instrument.  

The seismometer registers anyone who walks within three meters of it.

Automatic Time Synchronization

     If the AmaSeis computer is connected to the Internet, it is highly recommended that a time 

synchronization program be run to reset the PC clock every hour.  There are free programs 

available that will go out over the Internet to periodically synchronize a computer's clock to 

accurate UTC time.  

http://www.boulder.nist.gov/timefreq/service/its.htm                                                            

http://www.arachnoid.com/abouttime/

AmaSeis Version 1.0 Level 2005.05.19

3.6