Can We Predict Earthquakes?
The recent, devastating earthquake in China has sparked discussion about whether earthquakes can be predicted. USGS scientist Mike Blanpied sets the record straight on what science is capable of.
Hello and welcome to the USGS CoreCast. I'm Jessica Robertson. Today I would like to welcome and introduce you to our guest, USGS Scientist, Michael Blampied. He is going to talk to us about earthquake prediction. Thank you for joining us today, Mike.
Nice to be here.
First I would like to know, can the USGS or any other agency predict earthquakes?
Jessica, there's currently no organization or government or scientist capable of successfully predicting the time and occurrence of earthquake. However scientists are very good at saying things more general about earthquake hazards and earthquake risks. For example we can look at faults and patterns of earthquakes over many years and we can do a pretty good job of saying where on the landscape we're likely to have earthquakes on which faults, how big those earthquakes are likely to be and about how heavy the shaking is likely to be from those earthquakes.
Using that information, um, we can improve building codes, we can do ah, land use planning, we can avoid buildings next to faults that are hazardous and so forth. So we can forecast in the long term where the earthquake hazard is likely to be."
I know that after large earthquakes, it is likely that aftershocks may occur. Can you predict the size and timing of these aftershocks?
Following any large earthquake, there will be a number of aftershocks. After a very large earthquake there may be many aftershocks and they may go on for months or even years. However, they decrease in frequency and generally decrease in size over time. Scientists can say about how often and how many aftershocks will occur but not exactly when or where.
The other thing scientists do following a large earthquake is to calculate the amount of stress that was moved onto nearby faults in the area increasing their risk of large earthquakes.
Has the USGS done experiments to predict earthquakes?
Yes. USGS has done and has sponsored much research over several decades on earthquake prediction, both specific prediction experiments and also more general research to understand the predictability of earthquakes. For example is there something that happened in the earth ahead of an earthquake that would allow it to be detected at the surface?
The USGS and the state of California engaged in a really careful experiment on earthquake prediction. In Central California, there's a stretch of the San Andreas fault that runs through a small town called Parkfield in Central California and back in the 80s it was noticed that there had been a pattern of earthquakes of about a magnitude 6, several of these earthquakes over time spaced out about every 20 to 25 years, the last one occurring in 1966. On the basis of that pattern, the USGS and the state predicted that there would be another one coming probably in the mid 80s. And that led to a very intensive experiment to try to capture all the information possible about that earthquake with a variety of instruments and also to predict it if possible. It turned out that the earthquake did not come in the 80s and it did not come in the 90s. It actually waited until 2004.
We did capture wonderful information about the earthquake using a variety of sensors, however, there was nothing that we could tell that was predictable about the earthquake. The earth gave no indication with a foreshock or an electric signal or a water signal or anything else that an earthquake was about to begun. It just demonstrates to us what we've already learned over several years and several decades that earthquake prediction, if it's possible at all is really hard.
So can you give us an example of what we can forecast about a particular fault?
Well the Hayward fault in the eastside of the San Francisco Bay is a great example. The Hayward fault has a very long history of earthquakes and geologists have dug into the fault zone and looked at the rocks to determine that earthquakes in the Hayward fault happen about every 140 years with some variation. It's been 140 years since the 1868 earthquake that did a great deal of damage in the San Francisco Bay and therefore the Hayward fault is one could say about due for an earthquake.
Now there is a lot of variability in how periodic those earthquakes are so we can't say whether the next earthquake will happen tomorrow or 10 years or even 20 years from now. But we do know that that earthquake is very likely, we think it's likely to be about a magnitude of 6.8 earthquake and therefore very dangerous. And we can take steps now to safeguard the Bay area against that earthquake that we're pretty darn sure is coming."
Now I've heard that animal behavior can predict earthquakes. Is that true?
There has been a fair amount of research on this topic in various places and as far as I understand there's been no demonstration that earthquakes are specially predictable by animals, however, research does continue on this topic. One thing that is clear is that some animals are very sensitive to various live vibrations on the ground.
And so oftentimes an animal will detect the early arrival of the faint waves that come out first from an earthquake and become aware that the ground is shaking before the humans around them become aware of the more heavier shaking that follows. And so an earthquake may cause animals to react a few seconds or even a minute before the humans nearby.
So can the USGS or any other agency do the same thing and detect these early waves?
Yes in fact there's quite a bit of work in that area and your listeners may be aware of P wave detectors or simple devices that one can for example hook up to your gas line in your house. That device basically feels for gentle shaking and if it detects that gentle shaking, it will shut off the gas before the arrival of the heavier shaking to follow. The other way that we can do this early warning is to place seismometers in the vicinity of where there's going to be an epicenter of an earthquake in high hazard areas. When the earthquake occurs the seismic network very quickly measures the earthquake and computers can determine that an earthquake has begun and that information can be radioed ahead to areas that have not yet received a strong shaking.
We call this system earthquake early warning, and there are operational systems in Mexico and in Japan and the USGS and partner organizations in California are doing research to understand what benefits an earthquake early warning system might have in California."
What exactly is the USGS's role in earthquake science and prediction?
The USGS actually has a unique role in earthquake prediction research. USGS is a federal agency that has the responsibility for issuing warnings for geologic disasters such as earthquakes, landslides and volcanoes. This includes the federal responsibility for issuing earthquake predictions.
Is there anything else you want to share with us today?
I simply want to make the point that well we don't have a method for predicting earthquakes as discussed. There is grounds for optimism. There is increased amounts of data, new theories and powerful computer programs and scientists are using those to explore ways that earthquakes might be predicted in the future. We can certainly hope that someday we'll be in a world where an earthquake can be anticipated and predicted before it occurs.
Well thank you for joining us today Mike.
It was nice talking with you.
And thank you to all our listeners who joined us for this episode of CoreCast. If you would like real time and historic information about earthquakes worldwide or to learn more about earthquake science, visit earthquake.usgs.gov. If you feel an earthquake, please report your experience on the didyoufeelit site located on the USGS earthquake Web site.
As always CoreCast is a product of the US Geological Survey Department of the Interior.
"throu" by calpomatt
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