Earthquake Hazards

FAQ

Can you predict earthquakes?

No. Neither the USGS nor any other scientists have ever predicted a major earthquake. We do not know how, and we do not expect to know how any time in the foreseeable future. USGS scientists can only calculate the probability that a significant earthquake will occur in a specific area within a certain number of years. An earthquake prediction must...

Can animals predict earthquakes?

The earliest reference we have to unusual animal behavior prior to a significant earthquake is from Greece in 373 BC. Rats, weasels, snakes, and centipedes reportedly left their homes and headed for safety several days before a destructive earthquake. Anecdotal evidence abounds of animals, fish, birds, reptiles, and insects exhibiting strange...

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...

Can "MegaQuakes" really happen? Like a magnitude 10 or larger?

No, earthquakes of magnitude 10 or larger cannot happen. The magnitude of an earthquake is related to the length of the fault on which it occurs. That is, the longer the fault, the larger the earthquake. A fault is a break in the rocks that make up the Earth's crust, along which rocks on either side have moved past each other. No fault long enough...

Can some people sense that an earthquake is about to happen (earthquake sensitives)?

There is no scientific explanation for the symptoms some people claim to have preceding an earthquake, and more often than not there is no earthquake following the symptoms.

Can the ground open up during an earthquake?

Shallow crevasses can form during earthquake-induced landslides , lateral spreads , or from other types of ground failures , but faults do not open up during an earthquake. An earthquake occurs when two blocks of the earth’s crust slide past one another after having been stuck together in one place for a long time, because of friction on the fault...

Will California eventually fall into the ocean?

No, California is not going to fall into the ocean. California is firmly planted on the top of the earth’s crust in a location where it spans two tectonic plates. The San Andreas Fault System, which crosses California from the Salton Sea in the south to Cape Mendocino in the north, is the boundary between the Pacific Plate (that includes the...

Is there earthquake weather?

In the 4th Century B.C., Aristotle proposed that earthquakes were caused by winds trapped in subterranean caves. Small tremors were thought to have been caused by air pushing on the cavern roofs, and large ones by the air breaking the surface. This theory lead to a belief in earthquake weather, that because a large amount of air was trapped...

Do solar flares or magnetic storms (space weather) cause earthquakes?

Solar flares and magnetic storms belong to a set of phenomena known collectively as "space weather". Technological systems and the activities of modern civilization can be affected by changing space-weather conditions. However, it has never been demonstrated that there is a causal relationship between space weather and earthquakes. Indeed, over...

What is an earthquake and what causes them to happen?

An earthquake is caused by a sudden slip on a fault . The tectonic plates are always slowly moving, but they get stuck at their edges due to friction. When the stress on the edge overcomes the friction, there is an earthquake that releases energy in waves that travel through the earth's crust and cause the shaking that we feel. In California there...

Can we cause earthquakes? Is there any way to prevent earthquakes?

Earthquakes induced by human activity have been documented at many locations in the United States and in many other countries around the world. Earthquakes can be induced by a wide range of causes including impoundment of reservoirs, surface and underground mining, withdrawal of fluids and gas from the subsurface, and injection of fluids into...

Foreshocks, aftershocks - what's the difference?

"Foreshock" and "aftershock" are relative terms. Foreshocks are earthquakes that precede larger earthquakes in the same location. An earthquake cannot be identified as a foreshock until after a larger earthquake in the same area occurs. Aftershocks are smaller earthquakes that occur in the same general area during the days to years following a...

Can the position of the moon or the planets affect seismicity? Are there more earthquakes in the morning/in the evening/at a certain time of the month?

Earthquakes are equally as likely to occur in the morning or the evening. Many studies in the past have shown no significant correlations between the rate of earthquake occurrence and the semi-diurnal tides when using large earthquake catalogs. Several recent studies, however, have found a correlation between earth tides (caused by the position of...

What is surface faulting or surface rupture in an earthquake?

Surface rupture occurs when movement on a fault deep within the earth breaks through to the surface. NOT ALL earthquakes result in surface rupture.

At what depth do earthquakes occur? What is the significance of the depth?

Earthquakes occur in the crust or upper mantle , which ranges from the earth's surface to about 800 kilometers deep (about 500 miles). The strength of shaking from an earthquake diminishes with increasing distance from the earthquake's source, so the strength of shaking at the surface from an earthquake that occurs at 500km deep is considerably...

Why are there so many earthquakes in the Geysers area in Northern California?

The Geysers Geothermal Field is located in a tectonically active region of Northern California. The major seismic hazards in the region are from large earthquakes occurring along regional faults that are located miles away from the geothermal field, such as the San Andreas and Healdsburg-Rodgers Creek faults. However, activities associated with...

Do earthquakes occur in Antarctica?

Earthquakes do occur in Antarctica, but not very often. There have been some big earthquakes--including one magnitude 8 --in the Balleny Islands. The boundary between the Scotia Plate and the Antarctic Plate just grazes the north tip of the Antarctic Peninsula (look "northwest" from the Pole toward South America). There is also a hint of a line of...

Where can I find earthquake educational materials?

The USGS has earthquake education resources on several websites: Earthquakes for Kids Topics for Earthquake Education USGS Resources for Teachers Other good starting points include: State Geological Surveys for states in earthquake-prone regions The Great ShakeOut Earthquake Drills website IRIS (Incorporated Research Institutions for Seismology),...

Where can I find current earthquake lists and maps for the world or for a specific area?

The Earthquake Hazards Program Latest Earthquakes Map displays earthquakes in near-realtime and up to the past 30 days of earthquakes. The interface includes three panels: a list of earthquakes, a map, and a settings/options panel. You can pan and zoom the map to view specific areas. Click on an event on the list or map for additional information...

Did I feel an earthquake? Can I report feeling an earthquake?

Report an earthquake experience or related observation through the Did You Feel It? citizen science webpage. The best way to do this is to click on the earthquake that you think you felt on one of the lists on the Earthquakes webpage, and then select the "Tell Us!" link. If you don't see the earthquake you think you felt, use the green "Report an...