Monitoring and Predicting Earthquakes and Volcanoes

What causes earthquakes?

They occur randomly below the Earth's surface due to a build-up of pressure between two converging plates, friction, or a sudden shift during plate movement at a passive plate boundary.

Why are earthquakes difficult to predict?

They occur randomly below the Earth's surface, and each plate movement can change the characteristics of a fault line, making previous patterns unreliable.

How can animal behaviour supposedly indicate an approaching earthquake?

Some people believe animals may react to primary (P) waves before humans can detect them. Examples include rats fleeing towns, animals coming out of hibernation early, and farm animals refusing to enter shelters.

Why is animal behaviour not considered a scientifically proven earthquake prediction method?

It is believed animals are more likely reacting to primary (P) waves that are undetectable by humans rather than actually predicting the earthquake.

How can animal behaviour still be useful before an earthquake?

It may give humans a precious few seconds of warning before an earthquake hits.

How can historical records be used to predict earthquakes?

They can provide a rough idea of when an earthquake might occur, helping create a long-term forecast and identify patterns in the frequency of earthquake activity in an area.

Why are historical records an unreliable method of earthquake prediction?

Each plate movement changes the characteristics of the fault line, making many previous earthquake timelines irrelevant.

What is the most reliable method of predicting earthquakes?

Measuring rock stress along fault lines using instruments to monitor pressure build-up.

How do seismologists predict earthquakes using rock stress?

They monitor pressure build-up at fault lines. As pressure increases, the likelihood of an earthquake also increases.

What do strainmeters measure?

They measure pressure levels at fault lines and can help predict when pressure may become too great and cause an earthquake.

How can satellites and GPS help predict earthquakes?

They monitor ground deformation, which may indicate an approaching earthquake.

What do seismographs detect?

They detect vibrations in the Earth's crust, including foreshocks that occur before an earthquake.

What are foreshocks?

Earthquakes or vibrations that occur prior to a larger earthquake.

What do tiltmeters detect?

They detect changes in the slope of the land. Bulging or changes in slope can indicate increasing pressure underground.

What instruments are used to monitor volcanic activity?

Seismometers, satellite/GPS, tiltmeters and EDMs are used to monitor volcanic activity and signs of an approaching eruption.

Why do earthquakes often occur before a volcanic eruption?

Magma and volcanic gases force their way upward through cracks and vents in the Earth's crust, causing rock to vibrate and triggering earthquakes.

What is the most obvious sign of an approaching volcanic eruption?

Ground deformation.

How do tiltmeters help predict volcanic eruptions?

They detect changes in the slope of a volcano. A change in slope indicates increased pressure inside the volcano.

What are EDMs and how are they used to monitor volcanoes?

EDMs (Electronic Distance Measurement) use a laser and receiver to track changes in the size of a volcano and monitor ground deformation.

What does an increase in the slope of a volcanic mountain indicate?

It indicates an increase in pressure inside the volcano.

How were tiltmeters, EDMs and GPS used in monitoring Mount St. Helens?

They were used to monitor ground deformation and changes in the volcano before and during the 1980 eruption of Mount St. Helens in Washington.

What is the role of seismometers in monitoring volcanoes?

They detect earthquakes and vibrations caused by magma and volcanic gases forcing their way through the Earth's crust.

What is the 'Big One' mentioned in earthquake prediction?

It refers to a predicted major earthquake along the west coast of the United States, particularly the California coast.

EWS

Japan uses an early warningn system to detect primary waves and broadcast life-saving alerts.

How EWS work

Seismographs detect fast moving non destructive primary waves before the destructive secondary waves. This sends an automatic alert to mobile phones and media. This provides a few seconds or a few minutes warning depending how far from the epicentre you are.

Earthquake that used prediction to save lives

Haicheng, China 1975 7.3. Saved estimated 150,000 lives. Exception though as a year later 240,000 died in the Tangshan earthquake, also in China. There was no warning. Hard to predict earthquakes with short term methods. So we rely on risk mitigation by long-term forecasting.