 The earthquake that rocked Southern California last January caught many by surprise. But Dr. Andrea Donilon, a geophysicist from NASA's Jet Propulsion Laboratory in Pasadena, actually saw it coming. We knew that there was a likelihood of an earthquake here on a fault similar to the one that we saw and we had estimated the potential of there being about a magnitude 6.4 earthquake. So we weren't surprised this earthquake occurred. Dr. Donilon and her colleagues tracked changes in the Earth's crust throughout the LA area. They do it with antennas like this, receiving signals from a series of satellites called the Global Positioning System or GPS. It's a navigational system but we use it to very precisely measure motion of the ground and from that the ground is continually being squeezed and pushed and we can assess earthquake hazard from that. Her research prior to the January quake indicated a buildup of stress along a fault running through the Northridge, California area, exactly where disaster ultimately struck. One of her goals now is to assess the impact of this Northridge quake on future events. Studies indicate that the stress increased along the Ventura Basin which is being squeezed close. So we want to monitor that region very carefully, try and understand if the earthquake hazard has increased there. Although they can't predict precisely where and when an earthquake will occur, Dr. Donilon and her colleagues' identification of potential hotspots should help focus efforts to shore up buildings and homes so that when the next one strikes, more will survive. The seismologists can measure an earthquake and see what happened after the fact, but for the first time with GPS and other techniques like it, we can actually measure how the earth is moving and try and assess earthquake hazard before the earthquake happens. Oat Mountain we found that went up 15 inches and that means it went up and stayed up 15 inches so the mountain actually grew and is taller now. The ultimate goal is to help quantify the earthquake hazard in the LA area and we would like to help prioritize things like building code retrofits. Right now, there's just a blanket. If you find a building that needs fixed, you fix it. There's no priority on one area being more hazardous than another. We don't do prediction, we do forecasting. So we're looking on 10 or 20 or 50 year probabilities of earthquake occurrence and I do want to point out that we do this work in conjunction with the geologists and the seismologists that this is one more component to the puzzle, but we don't do prediction on a daily basis. And they used to shine lights across mountains and measure angles between mountain peaks. That was a very imprecise technique, however. This is much more precise. What we're looking for now is the post-seismic relaxation, we call it, to understand how this fault has affected neighboring faults. We're doing that by putting in a network of continuous GPS receivers. So when there's an earthquake like we had in Northridge, we don't have to drive a truck up here and deploy the receiver. We instantly have data as soon as the earthquake occurs. We like to see these techniques used in Northern California and they are to some extent. We'd also like to see them in the Pacific Northwest and all over the world. Japan is setting up a network of 300 stations, for example. Line Frostfall, obviously, it has a tip right about roughly the case of the coast of the proxy, but it extends well back where anywhere you want to put it, it sends back at least to you, back where this thing is locked or not. And that's the main concern that I have. We can certainly put Seismic here. We see these rotations. We also see then the displacements are a lot higher on this side, much smaller here. We have a lot higher strength across the basin here. So the polar rotation is somewhere up in here? It's actually here. Oh, really tight. It's really tight. Okay. Extremely tight. What I'd really like to know is, A, is this ramp locked, in which case we shouldn't see any strain accumulating across it, which it sounds like... We'll also see what's happening post-seismically from here because the largest post-seismic motion should be about a fault dimension away from the fault. So that's perfect. Okay. One way that I use Andrea's data is to try to understand whether these faults are slipping very slowly but inexorably at depth and relieving strain that way or whether they're locked in accumulating strain over hundreds and thousands of years and eventually that snaps loose as an earthquake. There are several faults within the Metropolitan Los Angeles region that were particularly concerned about, five or six in particular, that potentially could produce very large earthquakes and by very large, I mean well in excess of magnitude seven, much, much larger than the recent Northridge earthquake. We're learning a lot from every new earthquake and all of these data eventually do come out in new building codes, new building specifications that hopefully will prevent huge economic losses and losses of human life.