Dr. Michael Blanpied: A lot of people wonder if the rate of earthquakes is increasing, but it does not appear to be. We have good statistics on the numbers of earthquakes going back years, decades and centuries.
Dr. Michael Blanpied: There are really three main reasons why we're seeing more news about deadly earthquakes. First is that the quality of reporting is much higher. Second is that we're able to record them better due to global digital seismic networks that report data in real time. Third is that more and more people live in quake-prone areas, so earthquakes are more likely to strike vulnerable populations than was the case decades ago.
New York, N..Y.: I recall reading years ago that the odds of an earthquake on the East Coast are far less than on the West Coast, but that an earthquake on the East Coast would be more devastating. Is this correct and would you please explain what this means?
Dr. Michael Blanpied: That is true. Our plate boundary runs up the west coast, but there are significant earthquake hazards in at least 39 of our states, affecting at least 75 million Americans. The problem with quakes in the central or eastern US is two-fold: Seismic waves travel farther in the colder, older crust under that part of the country, so the damage can be more widespread. And there are more older buildings that may be vulnerable to being shaken. It is wise to examine earthquake hazards everywhere in the US, and to make prudent decisions about when it makes sense to replace or shore up vulnerable buildings.
Hunters Woods Elementary, Reston, Va: 1. Is seismic activity on the rise? 2. Will there be a great quake in the USA anytime soon? 3. How would seismic activity be on the rise if tectonic plates are basically floating on the magma?
Dr. Michael Blanpied: Seismic activity, in general, isn't going up or down. We get a lot of big quakes every year, and occasionally those hit near population and cause damage--it's mostly a matter of chance.
There could be a big quake in the US any time, we can't tell in advance! It could be a minute from now, or next week, or next year, or later. We do know they're coming, just not when.
Are Earthquakes Really on the Increase?
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 major earthquakes (7.0 - 7.9) and one great earthquake (8.0 or above) in any given year.
Largest Earthquakes in the World Since 1900*
*The recent Japan earthquake is not included (yet), which would make it the fifth largest quake since 1900.