Earthquake Hazards

FAQ

How does the USGS tell the difference between an earthquake and a sonic boom?

Steps to identification of a sonic boom: The USGS sees either nothing on our seismic records or a fairly short high-frequency signal that doesn't look like an earthquake. On rare occasions, we see the event on multiple stations, and the time difference between stations matches the speed of sound in air, which is slower than the speed of seismic...

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.

How can an earthquake affect groundwater or changes in wells?

Groundwater levels in wells may oscillate up and down while seismic waves pass, and in some cases, the water level may remain higher or lower for a period of time after the seismic wavetrain has ended.

Where can I find photographs of earthquake damage?

Two sources for photographs that show earthquake damage are: Earthquake Hazards Program - Earthquake Photo Collections U.S. Geological Survey Photographic Library (see 'earthquakes' in the categories left column)

What is liquefaction?

Liquefaction takes place when loosely packed, water-logged sediments at or near the ground surface lose their strength in response to strong ground shaking. Liquefaction occurring beneath buildings and other structures can cause major damage during earthquakes. For example, the 1964 Niigata earthquake caused widespread liquefaction in Niigata,...

Can you feel an earthquake if you're in a cave? Is it safer to be in a cave during an earthquake?

There is nothing different about a cave that would make it immune to the shaking from an earthquake. Just as there are safer and less safer places to be on the surface of the earth during an earthquake, there are also various characteristics inside caves that make some cave locations safer or less safe than others. First of all, whether or not you...

What are earthquake lights?

Phenomena such as sheet lightning, balls of light, streamers, and steady glows, reported in association with earthquakes are called earthquake lights (EQL). Geophysicists differ on the extent to which they think that individual reports of unusual lighting near the time and epicenter of an earthquake actually represent EQL: some doubt that any of...

Do all wastewater disposal wells induce earthquakes?

No. Of more than 150,000 Class II injection wells in the United States, roughly 40,000 are waste fluid disposal wells for oil and gas operations. Only a small fraction of these disposal wells have induced earthquakes that are large enough to be of concern to the public. Learn more: USGS Induced Earthquakes EPA's Underground Injection Control (UIC...

Is it possible to anticipate whether a planned wastewater disposal activity will trigger earthquakes that are large enough to be of concern?

Currently, there are no methods available to do this. Three conditions must be met for injection to induce an earthquake: Presence of a fault Stresses acting on the fault favorable to slip A pathway for the pressure increase from injection to interact with the fault. Evidence from some case histories suggests that the magnitude of the largest...

How does the injection of wastewater at depth cause earthquakes?

Earth's crust is pervasively fractured at depth by faults. These faults can sustain high stresses without slipping because natural "tectonic" stress and the weight of the overlying rock pushes the opposing fault blocks together, increasing the frictional resistance to fault slip. The injected wastewater counteracts the frictional forces on faults...

How large are the earthquakes induced by fluid injection?

The largest earthquake induced by fluid injection that has been documented in the scientific literature was the September 23, 2016 earthquake in central Oklahoma. It had a magnitude of 5.8. Four magnitude 5+ earthquakes have occurred in Oklahoma, three of which occurred in 2016. In 2011 a magnitude 5.3 earthquake was induced by fluid injection in...

Are earthquakes induced by fluid-injection activities always located close to the point of injection?

No. Given enough time, the pressure increase created by injection can migrate substantial horizontal and vertical distances from the injection location. Induced earthquakes commonly occur several kilometers below the injection point. Learn more: USGS Induced Earthquakes

Is there any possibility that a wastewater injection activity could interact with a nearby fault to trigger a major earthquake that causes extensive damage over a broad region?

So far, there is no conclusive example linking injection operations to triggering of major earthquakes. However, we cannot eliminate this possibility. Learn more: USGS Induced Earthquakes

Does the production of natural gas from shales cause earthquakes? If so, how are the earthquakes related to these operations?

To produce natural gas from shale formations, it is necessary to increase the interconnectedness of the pore space (permeability) of the shale so that the gas can flow through the rock mass and be extracted through production wells. This is usually done by hydraulic fracturing ("fracking"). Fracking causes extremely small earthquakes, but they are...

What work is the USGS doing to better understand the occurrence of injection-induced earthquakes?

USGS supports both internal and external (university-based) research on the causes of induced earthquakes. This research focuses on injection-induced earthquakes, including from wastewater disposal, enhanced geothermal technologies, and at carbon dioxide sequestration sites. USGS and its university partners have also deployed seismometers at sites...

Oklahoma now has more earthquakes on a regular basis than California. Are they due to fracking?

In a few cases, yes, but in most cases no. Only a few of the over 2000 magnitude 3 and larger earthquakes since 2009 that have occurred in Oklahoma have been connected to hydraulic fracturing. The majority of earthquakes in Oklahoma are caused by the industrial practice​ known as "wastewater disposal". Wastewater disposal is a ​separate ​process...

Where can I find a list of yearly estimated deaths from earthquakes around the world?

Our Earthquake Statistics website has annual totals for worldwide earthquakes and U.S. earthquakes from 1990 to the near-present. Estimated deaths from those earthquakes are listed at the bottom of the charts. The website also has M3+ earthquake counts by state beginning in 2010.

Which states have the smallest number of earthquakes? Is there any place in the world that doesn't have earthquakes?

Florida and North Dakota are the states with the fewest earthquakes. Antarctica has the least earthquakes of any continent, but small earthquakes can occur anywhere in the World. Our Earthquake Statistics website has M3+ earthquake counts for each state beginning in 2010. Learn more: Earthquake Information by Region (scroll down for information by...

Where do earthquakes occur?

Earthquakes can strike any location at any time, but history shows they occur in the same general patterns year after year, principally in three large zones of the earth: The world's greatest earthquake belt, the circum-Pacific seismic belt , is found along the rim of the Pacific Ocean, where about 81 percent of our planet's largest earthquakes...

Where can I find a list of the largest earthquakes in the United States? In the World?

The USGS Earthquake Lists, Maps, and Statistics website has statistics about earthquakes in the United States and the world, including a list of the world's 20 largest recorded earthquakes.