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Natural Hazards

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.

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What is UTC, and why do you report earthquakes in UTC?

UTC stands for Coordinated Universal Time, and for this purpose is the same as GMT (Greenwich Mean Time).Since the USGS and other seismic network agencies record earthquakes around the globe in all the various time zones, using a single standard time reference is best for record-keeping and exchange of data. The individual event pages with details about each earthquake use UTC for the reference...

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What is UTC, and why do you report earthquakes in UTC?

UTC stands for Coordinated Universal Time, and for this purpose is the same as GMT (Greenwich Mean Time).Since the USGS and other seismic network agencies record earthquakes around the globe in all the various time zones, using a single standard time reference is best for record-keeping and exchange of data. The individual event pages with details about each earthquake use UTC for the reference...

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Which volcanic eruptions were the deadliest?

Deadliest Volcanic Eruptions Since 1500 A.D.EruptionYearCasualtiesMajor CauseNevado del Ruiz, Colombia198525,0001,3Mudflows3Mont Pelée, Martinique190230,0001 (29,025)2Pyroclastic flows2Krakatau, Indonesia188336,0001 (36,417)2Tsunami2Tambora, Indonesia181592,0001,2Starvation2Unzendake, Japan179215,0001 (14,030)2Volcano collapse, Tsunami2Lakagigar (Laki), Iceland17839,0001 (9,350)2Starvation2Kelut...

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Which volcanic eruptions were the deadliest?

Deadliest Volcanic Eruptions Since 1500 A.D.EruptionYearCasualtiesMajor CauseNevado del Ruiz, Colombia198525,0001,3Mudflows3Mont Pelée, Martinique190230,0001 (29,025)2Pyroclastic flows2Krakatau, Indonesia188336,0001 (36,417)2Tsunami2Tambora, Indonesia181592,0001,2Starvation2Unzendake, Japan179215,0001 (14,030)2Volcano collapse, Tsunami2Lakagigar (Laki), Iceland17839,0001 (9,350)2Starvation2Kelut...

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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...

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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...

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When will the next large earthquake occur in Yellowstone?

Earthquakes cannot be predicted yet, but modern surveillance conducted with seismographs (instruments that measure earthquake locations and magnitudes) and Global Positioning System (GPS) 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 movement.Yellowstone lies within a...

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When will the next large earthquake occur in Yellowstone?

Earthquakes cannot be predicted yet, but modern surveillance conducted with seismographs (instruments that measure earthquake locations and magnitudes) and Global Positioning System (GPS) 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 movement.Yellowstone lies within a...

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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) recorded in a 5-day period...

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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) recorded in a 5-day period...

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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 the reports constitute solid evidence for EQL...

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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 the reports constitute solid evidence for EQL...

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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 safe 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 feel an earthquake in a cave depends chiefly upon...

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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 safe 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 feel an earthquake in a cave depends chiefly upon...

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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, Japan which destroyed many buildings. Also, during the...

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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, Japan which destroyed many buildings. Also, during the...

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Where can I find photographs of earthquake damage?

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

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Where can I find photographs of earthquake damage?

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

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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.Learn more:Groundwater Effects from EarthquakesGroundwater Response to Earthquakes

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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.Learn more:Groundwater Effects from EarthquakesGroundwater Response to Earthquakes

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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.

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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.

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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...

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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...

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