|JPL Podcast: Space-Age Quake Research
|Apr. 14, 2006
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Narrator: Earthquake research: from ground to space.
I'm Jane Platt and you're listening to a podcast from JPL -- NASA's Jet Propulsion Laboratory in Pasadena, Calif.
April 18, 1906 - a massive, deadly earthquake left the city of San Francisco in shambles.
100 years later, earthquake research has changed dramatically.
Various agencies are studying quakes, including NASA and JPL, which are bringing space technology into the mix.
We can't actually travel back in time to study the 1906 earthquake directly, but scientists are doing the next best thing - re-creating the earthquake inside a computer.
Glasscoe: So we're using computer models to model the 1906 earthquake and the deformation that occurred as a result of this earthquake.
Narrator: Maggi Glasscoe, a JPL geophysicist. She and her colleagues use math and physics to figure out how the Earth buckled and shifted during the 1906 quake. They try to re-create that scenario in the computer.
Glasscoe: We have a good idea of how the physics of the Earth work and we have the observations, so we try to fit our model as best we can to the observations.
Narrator: This helps them understand the forces behind earthquakes, the quake cycle, and where and how strain is building up that might lead to future quakes.
Glasscoe: This modeling project is specifically looking at the deformation associated with the 1906 earthquake, but we are also applying these computer models to look at different areas, including the Los Angeles basin.
Narrator: The hope is that this experimental research into different regions will help scientists find some patterns. Maggi Glasscoe has worked closely at JPL with Dr. Andrea Donnellan, a foremost authority on earthquake research. We caught up with her out in Northridge, California, site of the 1994 big earthquake, and it's also the site of a Global Positioning Satellite receiver that's used for JPL earthquake studies.
Donnellan: This is a GPS receiver, so it tracks the GPS satellites up in the sky. The signal goes down to that box there and then it's radioed back to JPL and the U.S. Geological Survey and Caltech. From that we understand how this site is moving relative to other sites. So we know that in the Northridge earthquake, this area actually moved upward from the earthquake, as did these mountains over here, which grew about 15 inches in the earthquake. We can study it, it actually, when the earthquake fault broke, it broke, but then it kept slipping for two more years after the earthquake. And we can measure it with this type of technique, because we're not just measuring the shaking part of an earthquake.
Narrator: And this information, along with radar satellite data, can help scientists track earthquake faults.
Donnellan: What this information tells us is where the faults are active, how active they are and where future earthquakes may occur. They also tell us how the Earth's crust responds to earthquakes. And we know now that earthquakes like this Northridge earthquake that occur transfer stress to other faults and those faults could start moving as a result.
Narrator: So 100 years after the devastation in San Francisco, how far have we come? A long way, according to Donnellan.
Donnellan: They didn't even really know the San Andreas fault existed, let alone all the neighboring faults in that earthquake. Since then we've been able to step back, use seismology to understand earthquakes better, map the faults better, and then we've added these space technologies, which really I think are going to revolutionize our understanding of earthquakes because we'll see all these movements we never saw before. Before we could measure the shaking from earthquakes. Now we'll be able to measure the strain in between the earthquakes as well, and all the quiet things that occur.
Narrator: You're probably sitting there wondering, with all this new technology, will they actually be able to predict earthquakes?
Donnellan: We don't know how to predict earthquakes in the sense that we don't know how to say it's going to happen tomorrow but what we are doing is refining the hazard maps. So the outlook used to be 30 years, we'd say this entire region could have an earthquake that's going to do damage in the next 30 years. Now we're refining those down to 10 years and five years. And when you get those refined hazard estimates, that are also refined in space, so we know exactly where the damage may be, then you can really target your retrofitting for those areas. And again, if you're prepared for the earthquakes, you're not going to experience so much damage from them. This information helps us know where we need to retrofit buildings, where we need to prepare, where the next earthquakes may be and how big they are. We just don't know if it's going to be tomorrow or in five years from now, but that's a much better estimate than 50 years from now.
Narrator: For more information on some of JPL's quake research, go to http://quakesim.jpl.nasa.gov . Thanks for joining us for this podcast from NASA's Jet Propulsion Laboratory.
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