The destruction caused by the recent earthquake in Japan has grabbed our attention this weekend. And, the subsequent tsunami and nuclear problems are tragedies that are almost incomprehensible. One question that has come up a couple of times on the television news program I was watching included: “Are earthquakes happening more frequently?”
Best source of information for a question like that is the United States Geological Survey (USGS). And the USGS answer to the question follows:
“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 than 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 USGS National Earthquake Information Center (NEIC) now locates about 20,000 earthquakes each year or approximately 50 per day. Also, because of the improvements in communications (e.g. Twitter, YouTube, Facebook) 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), the USGS expects about 17 major earthquakes (7.0 – 7.9) and one great earthquake (8.0 or above) in any given year. So far in 2011, the NEIC Information Center indicates that we have experienced one great earthquake and six major earthquakes