Unexpected earthquakes within continental plates pose challenges

Mar 19, 2012

Earthquakes that occur on "passive" continental margins, such as the August 2011 magnitude 5.8 Mineral, Virginia, earthquake, surprise people because they expect earthquakes to occur only on plate boundaries. But, in fact, large and damaging intraplate earthquakes occur fairly regularly on passive margins around the world. For instance, in North America the approximately magnitude 7 Charleston earthquake shook South Carolina in 1886, causing severe damage and about 60 deaths, and the 1929 magnitude 7.2 earthquake on the Grand Banks of Newfoundland, Canada, caused a tsunami, a large landslide, and 28 fatalities.

Although they are fairly common, these earthquakes are not well studied, and their specific geologic settings and causes are unclear. Wolin et al. review what is known about these earthquakes and describe some of the challenges. They note that these quakes, which occur both onshore and offshore, are thought to be caused by reactivation of ancient faults created by previous continental collision and breakup. Stresses causing passive margin earthquakes could be due to plate- wide forces, , local stresses, or other factors, but no comprehensive model explains all of these earthquakes. of passive margin earthquakes can occur for hundreds of years.

One challenge is that because large intraplate events occur infrequently and small events are not well recorded, it has been difficult for scientists to collect enough data on passive margin quakes to form a complete understanding. However, GPS is making it possible to track tiny crustal deformations as small as one millimeter per year (0.038 inches per year), so scientists can identify areas where strain is building. The authors conclude that it is important to continue research on these quakes, integrating seismic, geodetic, and geological techniques, to learn more about the mechanisms causing passive margin earthquakes and to improve hazard assessment.

Explore further: NASA balloons begin flying in Antarctica for 2014 campaign

More information: Mineral, Virginia, earthquake illustrates seismicity of a passive-aggressive margin, Geophysical Research Letters, doi:10.1029/2011GL050310 , 2012

add to favorites email to friend print save as pdf

Related Stories

Understanding mysterious continental intraplate earthquakes

Oct 12, 2007

A new volume published by the Geological Society of America sheds light on mysterious earthquakes in the interiors of continents. These earthquakes, like those that occur in the central U.S., are what the book's editors describe ...

Geological evidence for past earthquakes in Tokyo region

Jan 31, 2012

In 1923, a magnitude 7.9 earthquake devastated the Tokyo area, resulting in more than 100,000 deaths. About 200 years earlier, in 1703, a magnitude 8.2 earthquake struck the same region, causing more than 10,000 deaths.

Quakes warn of seismic danger closer to home

Apr 08, 2005

More earthquakes along the fault that caused the Boxing Day and Easter Monday earthquakes are “inevitable” and may cause shocks and tsunamis close to north-western Australia. Dr Wouter Schellart, who is working on mod ...

Eastern earthquake unusual but not remarkable

Aug 25, 2011

(PhysOrg.com) -- The earthquake that shook University Park and the entire northeast yesterday afternoon (Aug. 23) was unusual in its strength but not an unusual event, according to a Penn State geophysicists.

Ill. earthquake a wake-up call

Apr 20, 2008

A U.S. seismologist said the earthquake that jolted the Midwest Friday is a reminder of the risks seismic events pose outside familiar quake areas.

Recommended for you

Scientists make strides in tsunami warning since 2004

10 hours ago

The 2004 tsunami led to greater global cooperation and improved techniques for detecting waves that could reach faraway shores, even though scientists still cannot predict when an earthquake will strike.

Trade winds ventilate the tropical oceans

11 hours ago

Long-term observations indicate that the oxygen minimum zones in the tropical oceans have expanded in recent decades. The reason is still unknown. Now scientists at the GEOMAR Helmholtz Centre for Ocean Research ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.