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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 a landslide hazard map?

Several kinds of maps are used to depict danger from landslides. These maps might be as simple as a map that uses the locations of old landslides to indicate potential instability, or as complex as a map incorporating probabilities based on variables such as rainfall, slope angle, soil type, and levels of earthquake shaking. The following types of maps are used to describe and depict landslide...

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What is a landslide hazard map?

Several kinds of maps are used to depict danger from landslides. These maps might be as simple as a map that uses the locations of old landslides to indicate potential instability, or as complex as a map incorporating probabilities based on variables such as rainfall, slope angle, soil type, and levels of earthquake shaking. The following types of maps are used to describe and depict landslide...

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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 waves in rock. Felt reports come from a wide area...

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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 waves in rock. Felt reports come from a wide area...

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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. Eruption Year Casualties Major Cause Nevado del Ruiz, Colombia 1985 25,000 1,3 Mudflows 3 Mont Pelée, Martinique 1902 30,000 1 (29,025) 2 Pyroclastic flows 2 Krakatau, Indonesia 1883 36,000 1 (36,417) 2 Tsunami 2 Tambora, Indonesia 1815 92,000 1,2 Starvation 2 Unzendake, Japan 1792 15,000 1 (14,030) 2 Volcano collapse, Tsunami 2 Lakagigar (Laki)...

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Which volcanic eruptions were the deadliest?

Deadliest Volcanic Eruptions Since 1500 A.D. Eruption Year Casualties Major Cause Nevado del Ruiz, Colombia 1985 25,000 1,3 Mudflows 3 Mont Pelée, Martinique 1902 30,000 1 (29,025) 2 Pyroclastic flows 2 Krakatau, Indonesia 1883 36,000 1 (36,417) 2 Tsunami 2 Tambora, Indonesia 1815 92,000 1,2 Starvation 2 Unzendake, Japan 1792 15,000 1 (14,030) 2 Volcano collapse, Tsunami 2 Lakagigar (Laki)...

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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 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...

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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...

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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) were recorded in a 5-day...

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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) were recorded in a 5-day...

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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 Collections U.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 Collections U.S. Geological Survey Photographic Library (see 'earthquakes' in the categories left column)

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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...

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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...

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