Earthquake Forecasting and Prediction

Parkfield, CA

Parkfield, California Parkfield is located on the San Andreas Fault, and has been the site of many earthquake studies for several decades. Why Parkfield? – Let’s look at a brief history of M6.0 Parkfield earthquakes

Parkfield, California What do you notice about the timing of Parkfield earthquakes? In the 1980s, Earth scientists realized that Parkfield earthquakes tended to occur approximately every 20 years The last M6.0 earthquake had occurred about 20 years previously, so seismologists predicted the next M6.0 earthquake would occur at Parkfield sometime in the late 1980s or early 1990s

Parkfield, California What happened? Lots of seismometers and other scientific instruments were placed at Parkfield to ‘catch’ the next earthquake… but it didn’t happen until 2004!

Earthquakes currently cannot be reliably predicted. So what can we do?

We can forecast earthquakes Similar to a weather forecast, seismologists can ‘forecast’ where earthquakes are likely to occur over a given time period and how large these earthquakes might be.

This map shows which areas of California are likely to have a magnitude 6.7 or larger earthquake in the next 30 years. Areas colored in blue are not likely to have large earthquakes. Areas colored in red and orange are much more likely to have large earthquakes.

This forecast gives a probability of > 99% of a M6.7 earthquake occurring somewhere in California in the next years – so if California does not have an earthquake this size, then seismologists will be pretty surprised!

After a large earthquake, many aftershocks occur. Seismologists can predict the areas most likely to experience aftershocks.

California is likely to have a large earthquake sometime in the next few decades. Discussion Topic: How can we prepare for this in advance?

Earthquake Early Warning

Travel time from San Diego to Los Angeles 25 seconds P-waves 25 seconds 41 seconds S-waves 41 seconds 50 seconds Surface waves 50 seconds If an earthquake occurred in San Diego, the seismic waves would not arrive in Los Angeles immediately. How long do you think the waves take to travel to Los Angeles?

With earthquake early warning, people can be notified that an earthquake occurred before the strong shaking reaches their location

This early warning would give people time to find a safe place during the earthquake, or to have computers automatically shut down elevators, subways, and other electrical systems.