Abstract of paper presented to the 65th Annual Meeting of the Pennsylvania Academy of Sciences, April 7 - 9, 1989, at Mount Airy Lodge, PA.

Joseph J. Gerencher, Jr., "An Active Homemade Seismograph System in the Earth Science Classroom"

    A homemade dual seismograph system has recently been installed within and beneath the classroom/laboratory that is used for teaching the Earth Sciences at Moravian College.  The seismometers, constructed out of common materials at a cost of approximately $80 each, are monitored continuously by an Apple IIe computer, and a display within the classroom shows the output traces from both units in real time.   One seismometer is mounted E-W on a table in the laboratory and the other is mounted N-S on the basement floor one level below the room.  The system displays and records from both seismometers, but triggers only on signals from the basement unit.   Students who use the classroom are surprised that earthquakes from throughout the world are routinely recorded and that, although the unit in the classroom responds sensitively to their weight, it does not respond to their jumping up and down.  Since the system was made operational in mid-January, 1988, one earthquake was received during an Astronomy class and two others were received while Meteorology laboratories were being held in the room.  On these occasions, class was halted and all efforts to directly sense the motions of the room were unsuccessful.