Natural Hazards
How do volcanoes erupt?
Can you predict earthquakes?
What is the difference between a tsunami and a tidal wave?
What is a landslide and what causes one?
The USGS monitors and conducts research on a wide range of natural hazards to help decision-makers prepare for and respond to hazard events that threaten life and property.
How does an earthquake affect groundwater levels and water quality in wells?
Groundwater levels in wells can oscillate up and down when seismic waves pass. The water level might remain higher or lower for a period of time after the seismic waves end, but sometimes a long-term offset of groundwater levels follows an earthquake. The largest recorded earthquake-induced offset in a well is a one meter rise. Water quality can also be affected by earthquakes, typically in...
Why do earthquakes in other countries seem to cause more damage and casualties than earthquakes in the U.S.?
There is more damage and more deaths from earthquakes in other parts of the world primarily because of buildings which are poorly designed and constructed for earthquake regions, and population density.
What are those booms I sometimes hear before or during an earthquake?
"Booms" have been reported for a long time, and they tend to occur more in the Northeastern US and along the East Coast. Of course, most "booms" that people hear or experience are actually some type of cultural noise, such as some type of explosion, a large vehicle going by, or sometimes a sonic boom, but there have been many reports of "booms" that cannot be explained by man-made sources. No one...
At what magnitude does damage begin to occur in an earthquake?
It isn't that simple. There is not one magnitude above which damage will occur. It depends on other variables, such as the distance from the earthquake, what type of soil you are on, building construction, etc. That being said, damage does not usually occur until the earthquake magnitude reaches somewhere above 4 or 5. Learn more: Glossary of earthquake terms Earthquake Magnitude, Energy Release...
What does an earthquake feel like?
The way an earthquake feels depends on where you are, where the earthquake is, and how big the earthquake is: A large earthquake nearby will feel like a sudden large jolt followed quickly by more strong shaking that may last a few seconds or up to a couple of minutes if it's a rare great event. The shaking will feel violent and it will be difficult to stand up. The contents of your house will be a...
How are engineers working to make roads and buildings safer?
Earthquake engineers are working to make roads and buildings safer in the event of major earthquakes. This includes both improving the design of new buildings and bridges as well as strengthening older units to incorporate the latest advances in seismic and structural engineering. The Federal Emergency Management Agency plays a central role in funding research and development for the purpose of...
How do I get earthquake hazard maps for locations outside of the U.S.?
The USGS has seismic hazard maps for the US, Alaska, Hawaii, Puerto Rico & U.S. Virgin Islands, Guam & Marianas and Samoa & Pacific Islands . In addition, we have created some other Foreign Hazard Maps for Afghanistan, Haiti, South America, Southeast Asia and the State of Gujarat, India . For more information about hazard maps for other locations outside of the U.S. visit the GEM (Global...
What is the USGS doing to mitigate and respond to earthquake hazards?
The U.S. Geological Survey performs the following functions related to earthquake hazard mitigation: Receives, analyzes, maintains, and distributes data on earthquake activity worldwide. Satellites link our National Earthquake Information Center in Golden, Colorado to a network of seismograph stations. These stations, located throughout the world, are maintained by the U.S. Geological Survey...
Can the National Seismic Hazard Maps be used as an earthquake forecast tool for the near future?
Not really. The USGS Seismic Hazard Maps website and the Unified Hazard Tool (for building custom maps) are designed to display the probability of different events that might occur in a several-year to several-decade period. The model bases all probability estimates on the average rate of earthquakes over long periods of time. As you shorten the time window, you should expect greater and greater...
What is the difference between earthquake early warning, earthquake forecasts, earthquake probabilities, and earthquake prediction?
The USGS uses these four terms to refer to four different things . Early warning is a notification that is issued after an earthquake starts. Probabilities and forecasts are comparable to climate probabilities and weather forecasts, while predictions are more like statements of when, where, and how large, which is not yet possible for earthquakes. Here are more detailed descriptions of each...
What is the probability that an earthquake is a foreshock to a larger earthquake?
Worldwide the probability that an earthquake will be followed within 3 days by a large earthquake nearby is somewhere just over 6%. In California, that probability is about 6%. This means that there is about a 94% chance that any earthquake will NOT be a foreshock. In California, about half of the biggest earthquakes were preceded by foreshocks; the other half were not. At this time, we cannot...
What is the probability that an earthquake will occur in the Los Angeles Area? In the San Francisco Bay area?
Los Angeles area: Within the next 30 years the probability is: 60% that an earthquake measuring magnitude 6.7 46% that an earthquake measuring magnitude 7 31% that an earthquake measuring magnitude 7.5 will occur in the Los Angeles region. San Francisco Bay area: Within the next 30 years the probability is: 72% that an earthquake measuring magnitude 6.7 51% that an earthquake measuring magnitude 7...