Every year about 120 strong earthquakes with magnitudes
of 6 to 6.9 on the Richter scale shake different areas
of the United States. But the highest level of damage is
from about 18 major earthquakes that happen every year
with magnitudes of 7 to 7.9 on the Richter scale.
continuously record and locate the center of all
earthquakes and are trying to find a pattern that may
help them to forecast earthquakes days in advance.
measuring devices and equipments are used for this