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Are Earthquakes Really on the Increase?
We continue to be asked by many people throughout the world if
earthquakes are on the increase. Although it may seem that we are having more
earthquakes, earthquakes of magnitude 7.0 or greater have remained fairly constant.
A partial explanation may lie in the fact that in the last twenty years,
we have definitely had an increase in the number of earthquakes we have
been able to locate each year. This is because of the tremendous increase in
the number of seismograph stations in the world and the many improvements
in global communications. In 1931, there were about 350 stations
operating in the world; today, there are more that 8,000 stations
and the data now comes in rapidly from these stations by electronic mail, internet and
satellite. This increase in the number of stations and the more timely
receipt of data has allowed us and other seismological centers
to locate earthquakes more rapidly and to locate
many small earthquakes which were undetected in earlier years.
The NEIC now locates about 20,000 earthquakes each year or
approximately 50 per day. Also, because of the improvements in
communications and the increased interest in the environment and natural disasters,
the public now learns about more earthquakes.
According to long-term records (since about 1900), we expect about 18
major earthquakes (7.0 - 7.9) and one great earthquake (8.0 or above)
in any given year. However, let's take a look at what has happened in the
past 31 years, from 1969 through 2001.
The following is a
list of major and great earthquakes during this period:
Number of Earthquakes Per Year
| Year |
Major
Earthquakes |
Great
Earthquakes |
| 1969 | 15 | 1 |
| 1970 | 20 | 0 |
| 1971 | 19 | 1 |
| 1972 | 15 | 0 |
| 1973 | 13 | 0 |
| 1974 | 14 | 0 |
| 1975 | 14 | 1 |
| 1976 | 15 | 2 |
| 1977 | 11 | 2 |
| 1978 | 16 | 1 |
| 1979 | 13 | 0 |
| 1980 | 13 | 1 |
| 1981 | 13 | 0 |
| 1982 | 10 | 1 |
| 1983 | 14 | 0 |
| 1984 | 08 | 0 |
| 1985 | 13 | 1 |
| 1986 | 05 | 1 |
| 1987 | 11 | 0 |
| 1988 | 08 | 0 |
| 1989 | 06 | 1 |
| 1990 | 12 | 0 |
| 1991 | 11 | 0 |
| 1992 | 13 | 0 |
| 1993 | 12 | 0 |
| 1994 | 11 | 2 |
| 1995 | 18 | 2 |
| 1996 | 14 | 1 |
| 1997 | 16 | 0 |
| 1998 | 11 | 1 |
| 1999 | 18 | 0 |
| 2000 | 14 | 1 |
| 2001 | 15 | 1 |
See also: Earthquake Facts and Statistics
See also: Magnitude / Intensity Information and Links
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