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 throughout this century (1) and, according to our records, have actually seemed to decrease in recent years.(2)
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 (3) and the many improvements in global communications.
In 1931, there were about 350 stations operating in the world; today, there are more than 8.000 stations [source 1] (or 4.000 stations [source 2]) (4) 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 17 [source 1] (or 18 [source 2)] (5) 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 32 years, from 1969 through 2001, so far. Our records show that 1992, and 1995-1997 were the only years that we
have reached or exceeded the long-term average number of major earthquakes since 1971. In 1970 and in 1971 we had 20 and 19 major earthquakes, respectively, but in other
years the total was in many cases well below the 18 per year which we may expect based on the long-term average.(6)
Earthquake Facts and Statistics
Earthquake Facts and Statistics Graphs
While most of the people knows USGS, ANSS (Advanced National Seismic System), which first 80 ANSS strong motion instruments were installed in San Francisco (40), Salt Lake City (20) and Seattle (20) in 2000, is widely unknown from general public; however this organization also produce lots of datas, maps and lists compiled in catalogs for seismologists and earthquake engineers, for teachers and the general public as well. (LINK)
Earthquakes of 7.0 magnitude or greater have remained constant throughout this century and the graph (C) above shows USGS data between 1980 and 2011.. Earthquakes have increased 7% according to this graph.. Now here is data between 1900 to 2011. (graphs D and E)
Between 1900 and 2011 earthquakes increased almost 60%, now that’s a impressive number! Some people claim this is high because the lack of earthquake measurement tools.. The USGS and ANSS graphs are exactly the opposite of each other..Earthquakes and natural disasters have been increasing over time and it’s not getting any better but lets hope for the best! Here is the link for more graphs and data about earthquakes!