State Releases New Fault Line Maps, Shaking Up San Diego City Zoning

Speaker 1: 00:00 Imagine gas and water service being shut down for months, along with the Coronado bridge buildings collapsing and mission-based sinking 12 inches. That's what scientists think would happen along the Rose Canyon fault line should an earthquake occur. Now the California geological survey is looking at ways to make San Diego more resilient to a catastrophe by imposing building restrictions. Gary Robbins, cover science and technology for the San Diego union Tribune. He is joining us with details. Gary, welcome. Hi. So further regulations are being put in place because data has revealed that the Rose Canyon fault is much more active than scientists initially thought. Do we have a sense of how many San Diego ans live within this active zone? Speaker 2: 00:44 There'll be more than a million and a half. So the city of San Diego has a main and a half people and the fall, it goes right through the heart of the city. So at least a main and a half people. Speaker 1: 00:53 Wow. Which areas of San Diego will be mostly affected by this fault zone? Speaker 2: 00:58 Well, it depends on how it breaks, but think of the fault has coming ashore and the Jolla Cove and going on the East side of Mount Solidad, then it comes down into old town cuts right down through the heart of the city, goes out into the Bay and then jumps across to Coronado and then goes off shore. So that's really through the heart of San Diego. Speaker 1: 01:17 Are these tighter building restrictions in the area expected to take effect, Speaker 2: 01:21 Looks like it's going to happen this summer. So the California geological survey has inactive. What are called, um, Alquist Priolo zones. In other words, they, um, they designated certain area of our town or city and say, if you want to build here, that's fine, but you probably have to do a geological study to find out whether the spot you want to build on is the site of an actor fault. And if it is then probably what you would have to do is do a so-called setback. You would have to move your project or short distance away. What they're trying to do here is to prevent a situation where the earthquake ruptures, the surface, right below a building causing catastrophic damage and loss of life. We've seen this happen in California on many occasions, including during the 1971, um, uh, San Fernando Valley earthquake, which occurred 50 years ago this month, Speaker 1: 02:12 What kind of impact will this have on future construction projects located within this cautionary zone? Speaker 2: 02:18 Well, it could be significant, but I don't want to leave people with the idea that it's going to shut everything down because it's not. And, um, like for example, if you just live in a neighborhood and you want to put in a swimming pool or a retaining wall, you're not going to have a problem with that. This is aimed at, uh, newly proposed projects, particularly residential buildings, commercial buildings, public buildings, um, that's who will be affected in these zones. Um, so for example, if they were going to be building an apartment complex on the, on market street, this would absolutely fall into it. Um, you know, given where it is on the map. Um, so it's, it'll have it'll affect a lot of types of buildings and there are 7,000 parcels in the city. Um, that'll be affected by this, but it won't, it's not meant to shut construction down. It's meant to do it in a more thoughtful way to prevent catastrophe. Speaker 1: 03:09 How has the scientific understanding of this fault changed in recent years? Speaker 2: 03:14 It has changed profoundly. There was a time when, uh, it was thought that the Rose Canyon fault was not active. Um, and then it was learned through scientific research that, well, it probably produces something really significant once every 1000 to 1500 years. And then just in the last few years they decided, you know, that's not right. We think it happens every 700 to 800 years. So we've gone from nothing happens here to something, to something even sooner. And they're doing more studies all of the time. So their understanding of the fault is really become sharper. And with each iteration, you know, they become more concerned about the fall. Speaker 1: 03:54 And as you mentioned, scientists say that significant seismic activity along this fault occurs in an interval of hundreds of years with the last major event occurring in the 17 hundreds. Despite that scientists still say we should remain cautious. Speaker 2: 04:09 You know, I really think that that we're seeing that play out now. Um, in the story I refer to it, this really large scenario that was run by the E R I about a year ago. So these are top engineers and, um, they said, what would happen in San Diego? If there was a 6.9 earthquake on the Rose Canyon fault and they found that it would be horrifying, it could damage 100,000 houses. It could displace 36,000 homes. It would shut down the court natto bridge. Um, they would cause parts of mission Bay to sink of four, to all the things that we, that you talked about at the top. So the impact on the city would cost billions of dollars in economic activity. It would likely kill significant members of people. There was one study earlier that talked about the possibility of between 1,002 thousand people dying in San Diego or being seriously injured in an event like this. Speaker 2: 04:59 So while they don't happen, often they do happen. And the other thing to keep in mind is we just don't know with any specificity when they're going to happen. It's said that the San Andreas is overdue, and that seems to be the case based on his, on his history, but it skipped past its most likely period of eruption in the last few years. So they just don't really know. The other thing that I would ask people to consider is this many of us remember the Northridge earthquake, that was a deadly earthquake. It was really, really bad. And it occurred on a fault that was not known to exist. So we have to be concerned about falls that do exist, but also realize that we live in a place where there are faults that may be very close to us that we don't yet know about. Speaker 2: 05:41 Now, the only way to really deal with that. And I talked to a reader about this this morning is this don't panic. Um, have an earthquake kit in your car and in your home and have a good communication system between members of your family and are members of work, know where hospitals are and know what to do. So when we shake the drop cover and hold on, you know, that's something very easy. So rather than just being anxious all the time about an earthquake, do the practical things that will help you survive because the reality is that even a very, even in a very large earthquake, most people by a super large margin will survive. Speaker 1: 06:18 Preparation is key. I've been speaking with Gary Robbins who covers science and technology for the San Diego union Tribune. Gary, thank you so much for joining us. Speaker 2: 06:28 You're welcome.