Why are we having so many earthquakes? Has naturally occurring earthquake activity been increasing? Does this mean a big one is going to hit? OR We haven't had any earthquakes in a long time; does this mean that the pressure is building up for a big one?
A temporary increase or decrease in seismicity is part of the normal fluctuation of earthquake rates. Neither an increase or decrease worldwide is a positive indication that a large earthquake is imminent.
The ComCat earthquake catalog contains an increasing number of earthquakes in recent years not because there are more earthquakes, but because there are more seismic instruments and they are able to record more earthquakes.
The National Earthquake Information Center now locates about 20,000 earthquakes each year, or approximately 55 per day. As a result of the improvements in communications and the increased interest in natural disasters, the public now learns about earthquakes more quickly than ever before.
According to long-term records (since about 1900), we expect about 16 major earthquakes in any given year, which includes 15 earthquakes in the magnitude 7 range and one earthquake magnitude 8.0 or greater. In the past 38 years, from 1973 through 2011, our records show that we have exceeded the long-term average number of major earthquakes only 8 times, in 1976, 1990, 1995, 1999, 2007, 2009, 2010, and 2011.
The year with the largest total was 2010, with 24 earthquakes greater than or equal to magnitude 7.0. In other years the total was well below the 16 per year expected based on the long-term average: 1989 only saw 6, while 1988 saw only 7 major earthquakes.
New Audiences, New Products for the National Seismic Hazard Maps
According to the U.S. Geological Survey (USGS), 2004 was the deadliest year for earthquakes since the Renaissance Age, making it the second most fatal in recorded history, with more than 275,950 deaths reported from the magnitude 9.0 earthquake and subsequent tsunami that hit the Indian Ocean on Dec. 26.
The year 2001 was a typical year based on historical seismic activity, producing 65 significant earthquakes worldwide and causing 21,436 fatalities according to the U.S. Geological Survey (USGS).
BOSTON -- A new ground shaking hazard map of the Western Hemisphere will show regions of potential earthquake damage, providing a useful global seismic hazard tool for government, industry and the general public.
USGS map displaying intensity of potential ground shaking from natural and human-induced earthquakes. There is a small chance (one percent) that ground shaking intensity will occur at this level or higher. There is a greater chance (99 percent) that ground shaking will be lower than what is displayed in these maps.
USGS map showing (1) the locations of major populations and (2) the intensity of potential earthquake ground shaking that has a 2% chance of occurring in 50 years.
A timeline of earthquakes in the New Madrid Seismic Zone (top) differs significantly from a typical aftershock sequence (bottom). A new study shows that earthquakes occurring today in the region are not aftershocks of the 1811-1812 earthquakes. Rather, they are evidence that stress is continuing to accumulate. Data source: CEUS-SSC catalog.
A year after the August 23, 2011 Virginia earthquake, USGS geologist Dr. Mike Blanpied discusses whether a similar event could occur again in the region in the near future, and in an earthquake, what you can do to stay stay safe.
A map of ShakeOut scenario shaking in southern California.