FAQs
Have questions? The answer is probably here!
Why should people in the eastern United States be concerned about earthquakes?
1) Severe earthquakes have occurred in the eastern U.S.: In November of 1755, an earthquake with an estimated magnitude of 6.0 and a maximum intensity of VIII occurred about 50 miles northeast of Boston, Massachusetts. Boston was heavily damaged. Other strong earthquakes recorded in the continental US were centered in southeastern Missouri near the border with Arkansas, Kentucky and Tennessee. In...
What are the Great ShakeOut earthquake drills?
The Great ShakeOut earthquake drills are based on scenario earthquakes that could effect the area if they were to actually take place. Great ShakeOut Earthquake Drills are an annual opportunity for people in homes, schools, and organizations to practice what to do during earthquakes, and to improve preparedness. These events are made possible through a collaboration between several agencies...
Why are there so many earthquakes at Yellowstone?
Almost all earthquakes at Yellowstone are brittle-failure events caused when rocks break due to crustal stresses. Though we've been looking at Yellowstone for years, no one has yet identified "long-period (LP) events" commonly attributed to magma movement. If LP events are observed, that will NOT mean Yellowstone is getting ready to erupt. LP earthquakes commonly occur at other volcanoes in the...
When will the next large earthquake occur in Yellowstone?
Earthquakes cannot be predicted yet, but modern surveillance for earthquakes in Yellowstone conducted with seismographs (instruments that measure earthquake locations and magnitudes) and GPS - Global Positioning Systems (instruments that measure slow ground movements) help scientists understand the state of stress in the Earth's crust. Those stresses could trigger earthquakes as well as magma...
Are there earthquakes associated with Mount Hood?
Felt earthquakes on Mount Hood (Oregon) occur every two years on average. Seismic monitoring , in effect since 1977, indicates a generalized concentration of earthquakes just south of the summit area and 2-7 kilometers below sea level. A seismic swarm in July 1980, during which nearly 60 earthquakes (mostly 5-6 kilometers deep with a maximum bodywave magnitude of 2.8) were recorded in a 5-day...
Can earthquakes trigger volcanic eruptions?
Sometimes, yes. A few large regional earthquakes (greater than magnitude 6) are considered to be related to a subsequent eruption or to some type of unrest at a nearby volcano. However, volcanoes can only be triggered into eruption by nearby tectonic earthquakes if they are already poised to erupt . This requires two conditions to be met: Enough "eruptible" magma within the volcanic system...
Do earthquakes large enough to collapse buildings and roads accompany volcanic eruptions?
Not usually. Earthquakes associated with eruptions rarely exceed magnitude 5, and these moderate earthquakes are not big enough to destroy buildings and roads. The largest earthquakes at Mount St. Helens in 1980 were magnitude 5, large enough to sway trees and damage buildings, but not destroy them. During the huge eruption of Mount Pinatubo in the Philippines in 1991, dozens of light to moderate...
Can nuclear explosions cause earthquakes?
A nuclear explosion can cause an earthquake and even an aftershock sequence. However, earthquakes induced by explosions have been much smaller than the explosion, and the aftershock sequence produces fewer and smaller aftershocks than a similar size earthquake. Not all explosions have caused earthquakes. The range of a possible earthquake triggered by an explosion is limited to a few tens of...
How can you tell the difference between an explosion and an earthquake on a seismogram?
Explosions and earthquakes both release a large amount of energy very quickly, and both can be recorded by seismic instruments. However, because the forces involved in each are very different, the waveforms that each creates look different. Nuclear tests are very near the surface of the earth; all of the energy is released from a small volume surrounding the device. Earthquakes are typically...
Can we use explosives to cause small earthquakes in order to prevent having large ones?
No. Even huge amounts of explosive almost never cause even small earthquakes, and it would take hundreds and thousands of small earthquakes to equal a large one, even if it could be done. In addition, we wouldn't have any control over the size of the earthquake being created if it worked, since small and large earthquakes all start out in exactly the same way. It's just not physically possible.
What is the Comprehensive Test Ban Treaty (CTBT), and what is the role of seismology in monitoring it?
On September 10, 1996, the United Nations General Assembly voted 158-3 to approve a treaty prohibiting all nuclear tests. The Comprehensive Test Ban Treaty has been signed by 130 nations - including the United States. President Clinton signed the agreement on September 24, 1996. Seismology is one of several fields which plays a role in monitoring the Comprehensive Test Ban Treaty. Underground...