RECORDING SEISMIC WAVES

ANCIENT (2ND CENTURY) CHINESE SEISMOSCOPE - BALLS COME FROM DRAGON'S MOUTH WHEN WAVE ARRIVES


MODERN SEISMOMETERS - SPRING-MASS SYSTEM HAS A "LAG" WHICH ALLOWS RECORDING GROUND MOTION AS FUNCTION OF TIME WITH INSTRUMENT ON GROUND

3 COMPONENTS (NORTH-SOUTH, EAST-WEST, UP-DOWN) PRECISE TIMING (GPS SATELLITES), DIGITAL AMPLIFICATION OF SMALL GROUND MOTION,DIGITAL RECORDING, DATA AVAILABLE ON WWW