MAUREEN CAVANAUGH: This is KPBS Midday Edition, I am Maureen Cavanaugh. San Diego's earthquake hazard estimate has increased. That is not exactly what most of us are eager to hear. But they say that knowledge is power. The US geological survey is out with an abundance of new knowledge about earthquakes here and across the country. In the new national seismic hazard maps, we see that areas of high hazard in California extend offer a wider area than previously thought, and newly discovered offshore faults have raised the risk here in San Diego. I would like to welcome my guests. Doctor Morgan Page is a USGS Research Geophysicist joining us by phone from Pasadena. Thank you for joining us. Pat Abbott is Professor Emeritus from San Diego State University's Geology Department. Welcome back. Morgan, what new information led to the increased earthquake hazard for the San Diego area? MORGAN PAGE: The main change for San Diego is that we have entered characterization of some of the faults offshore. These are faults that we knew existed before, but we did not have good information on how fast they were moving over the long-term. Now we have included GPS information to the model which allows us to fill in some of the gaps in the fault data. We have better characterization of how often these faults have large earthquakes that affect San Diego. MAUREEN CAVANAUGH: Why were the earthquake maps updated in the first place? Is it because there is now new technology to show in better detail across the country where there are faults hazards? MORGAN PAGE: We typically update the national maps every six years. We keep them updated at the same interval as building codes. It is a good idea to update them often, because so much new scientific information is discovered in the intervening time. We want to make our maps on the best available science, and keep them up-to-date. There is a lot of exciting new science particularly in California that has gone into making a better California model. MAUREEN CAVANAUGH: What kind of technology ñ and maybe even computer modeling ñ is going into these maps? MORGAN PAGE: Well, we have a lot of new sources of data. We have more geologic data that we are using. Past earthquakes that they found by digging up trenches along major faults determined prehistoric earthquakes that we now know about four people lived in California. We also have new data coming in from the GPS system that we are making better use of to fill in the gaps between where we have geologic information. We have more information, and more earthquakes have happened in the last few years that our networks have picked up that are giving us information on the finer scale, a feeling it information between the faults where smaller in earthquakes can happen. We also have better models, that are able to capture a wider range of possible earthquakes that could happen by linking smaller faults into larger ruptures, which is something that we have seen happen in rural earthquakes. MAUREEN CAVANAUGH: Pat, how does the discovery, or greater knowledge about the offshore faults off the coast of San Diego, how did those risks compared to the risks we already know exist here in San Diego county, like from the Rose Canyon fault line? PAT ABBOTT: They are very comparable in the sense that we have always looked out there. You see the islands, Coronado Island, San Clemente Island, why are those islands there? They are the top of ridges lifted up by active faults, particularly where there is a compressive bend within the faults. We have always known they are out there, but we have not had the data like Morgan was just describing. Geologists go out and take trenches along the fault. You take measurements, and do radiocarbon dating to get a prehistoric catalog. You can't do that easily a short. More GPS data put into their models give us an idea how to talk about slip rates, how much movement is occurring over those faults over time, and that makes the computer model more powerful. MAUREEN CAVANAUGH: Are we also able to get from this data an idea of how much energy these faults might contain, how big the earthquakes maybe? PAT ABBOTT: Heretofore we have been primarily relying on studies that have been individual. For example, some section of the San Andreas Fault maybe carefully trenched and examined. After months or years of work, we get results from that. This time they are are trying to get above and beyond individual studies, those that are noteworthy or get a lot of attention, we're trying to get back down to the basic data to say that we are expecting a 30% chance of a magnitude 7 earthquake on this section of the fault in the next thirty years. We want to say what are the slip rates? What they have done here, they have gone and segmented all of these faults into rectangles, and try to put basic information like slip rates and reduce it to specifics like this. It is using a lot more seismic data, information for more earthquakes and try to get more of a huge data matrix throughout the state, and led a supercomputer use all of the data, and give us probabilistic analysis. MAUREEN CAVANAUGH: Because of these offshore faults, does that increase the risk of a tsunami here? PAT ABBOTT: Yes and no. First off, in terms of the big offshore islands, those are the tops of ridges and those ridges make an underwater barrier that sap most of the energy out of the big tsunamis, like those that come from Japan, Alaska, or Chile. Of course we have specific data from those big earthquakes that have happened. The real eye-opener for us here occurred in 1998 in Papua, New Guinea, when an offshore fault near an island kind of like what we have had a magnitude 7 earthquake, which was not that impressive all by itself. However, that earthquake shook loose an underwater sand slide which ended up pushing a 15 foot his tsunami across the barrier island there, and killed over 2000 people. When I saw that, I think oh my goodness, the real threat from tsunami is offshore with the very faults that we're now getting more understanding about. That is a confluence of two events. One is a big earthquake, which has a long time between it. Second, we have to have a submarine landslide oriented towards the coast, to make the danger. It is a very high consequence event, with low probability. MAUREEN CAVANAUGH: The overall increase in risk that the USGS is giving to San Diego consideration of all of the new data is about 20%. Do you agree with that? PAT ABBOTT: Certainly. Like I said, when you read this, it's an all-star list of geophysicists, seismologists, geologists, a huge collective effort. Adding a supercomputer here to go through more than 1400 logic trees for ways of analyzing all of it, it is just a quantum leap up in terms of data utilization and examination. It's just that, you have tremendous respect for it, it has raised the platform and of course more studies will go on top of that platform to get more specific for specific sites. MAUREEN CAVANAUGH: Morgan, looking at the entire map that you and your colleagues have put together, there have been increased assessment of earthquake hazards in many areas across the country, for instance in the eastern US in areas like Virginia and South Carolina. What other areas have seen increases? MORGAN PAGE: The biggest increase in the last few years is due to induced earthquakes. These are earthquakes that are caused by deep injection of wastewater from oil and natural gas activity. The hazards due to these induced earthquakes, which is quite significant in places like Oklahoma for example, is not yet included in the national seismic hazard maps. That is because these are the long-term fifty-year maps. When it comes to induced earthquakes, the activity can die down if the wastewater injection wells are shut off, or it could move to areas of activity can begin at new wells. The future of earthquake hazards is really dependent on what the future industry activity is. MAUREEN CAVANAUGH: I want to talk a lot more about those induced earthquakes, but just looking at the map as it is, you know our recent history of the United States, there have been places in the United States that have had seismic activity that came as a surprise. I will reference again that area in eastern Virginia near Washington DC, a couple of years ago they had an earthquake there, and that really woke them up. Did they not know that there was hazard before? MORGAN PAGE: No, and the hazard map created before the Virginia earthquake did show a little bubble of seismicity in the central Virginia seismic zone. It was known that area had increased hazard relative to other surrounding areas. I would say it's a complete surprise that a moderate sized earthquake what happened there. MAUREEN CAVANAUGH: The induced earthquakes at that you are talking about that are not part of the new map, are we talking about hydraulic fracturing, or fracking here? MORGAN PAGE: It is important to distinguish that fracking directly does not seem to cause large earthquakes. But activities like fracking to generate a lot of wastewater, and due to the chemicals in wastewater injected deep into the ground, it is the injection of wastewater that seems to cause earthquakes. That is an important distinction, because wastewater injection is not always in the same location that the fracking is occurring. They can sometimes put this wastewater kilometers away, even farther, and that is where the earthquakes occur, where the wastewater ends up injected. MAUREEN CAVANAUGH: I think you have found, even though it is not on the map, in places like Oklahoma were seismic activity used to be minimal, it's now registering small quakes with the frequency of California, is that right? MORGAN PAGE: Even higher than California. So far, in 2014, Oklahoma has had more magnitude three and larger earthquakes than the state of California, which has not only historically has been quite active, but is a much larger state. So it is really quite striking in Oklahoma alone, the activity has gone up by a factor of 100 from what it was five years ago. MAUREEN CAVANAUGH: These are induced earthquakes? MORGAN PAGE: Yes. MAUREEN CAVANAUGH: Pat, fracking, although the activity itself does not necessarily lead to more seismic activity, it is the way that the wastewater as a part of this process is injected back into the earth. It is being conducted in central California. Considering we already have a high earthquake risk, is that a good idea? PAT ABBOTT: This situation requires a lot of balance. What is all of the new drilling technology, the horizontal drilling that allows a lot more fracking, and the resulting wastewater disposal and other large volume wells, just to stay at a positive note this has been marvelous for the US economy in terms of the balance of payment for energy self-sufficiency, tens of thousands of jobs. You read things like North Dakota with more millionaires per capita than any state in the US, totally dependent on that. I don't want to say that's the whole story, but I want to balance the ledger here. It has been proven that fracking, pumping water underground under pressure triggers earthquakes. It has been known since the mid-60s, the USGS took over and abandoned oilfield in northwest Colorado and played with it, pumping water here and there, and they could pretty much trigger earthquakes it well. This is not new, pumping water underground, is just proven. If you are doing it in an area where there are no faults, that means that you have to rupture earth where there is not already a fault. That means the earthquakes cannot be too big. They can be very numerous. The real hazard is if we pump water into an old fault, maybe what we don't even know about from prerecorded history, and reactivate a fault with a long movement for quite a number of seconds and create high magnitude earthquake, that would obviously be a concern. MAUREEN CAVANAUGH: Which might happen in an area that was already prone to earthquakes. I'm talking Central California. PAT ABBOTT: It's a big oil problem for us. There are a lot of prospective areas there, where there is evidence amounts of hydrocarbon energy that could be extracted. I think the main point would be to avoid major faults, including ones that are inactive now. MAUREEN CAVANAUGH: Morgan, does any of the new data that you have compiled to come up with a new seismic that for the United States, does any of it help determine when the next week will take place? MORGAN PAGE: These are very long-term maps, giving probabilities of earthquakes over the next fifty years time period, about the time scale that the building may be up. They are long-term maps for planning building. Unfortunately, we cannot protect earthquakes to say when an earthquake will happen in terms of a week or a day that scale, but we can give probability over a long period of time. MAUREEN CAVANAUGH: Predicting earthquakes is what people are hoping for, and I'm wondering, is science any closer to that at all? MORGAN PAGE: We are becoming better at forecasting probabilities, because I have the same tone as prediction, where it implies that we are going to tell people exactly when the earthquake will happen. MAUREEN CAVANAUGH: Or look into a crystal ball. MORGAN PAGE: Yeah, small and big earthquakes seem to start a very similarly. There is nothing in the data that we have found so far that indicates something is different before a big earthquake or a small one. To really protect earthquakes in a meaningful way, you just have to pick one, because there are so many earthquakes that are so small everyday that we don't feel them. If we predict all of those it would not be useful unless we could tell people which ones would be big. MAUREEN CAVANAUGH: The big bright spot for people on this map is that the highest hazard for quakes still move east into the desert, away from San Diego's most populated areas. That is the San Andreas Fault. Is that still the biggest earthquake threat to Southern California? PAT ABBOTT: For Southern California in total, definitely, it passes right through the city limits of San Bernardino. For us, we're cushioned for a certain extent by distance. A lot of the high-frequency waves will have lost energy, but we will still have a long seismic waves to give us a big nasty shake. That would be the highest magnitude close to us. But if we go back to the Rose Canyon fault running right through the heart of the city, that could pop out something in a magnitude 6, on any day. Because of its closeness, and getting the full range of the high-frequency waves, I don't know specifically, but one of the things we will find out after the earthquakes, we always get nasty surprises. Without necessarily talking about destruction or ruin on the Japanese scale, but there are always at least some stomach turning failures that occur in urban areas. MAUREEN CAVANAUGH: Okay, well we did our best. We talked about this to the best of our ability, no predictions, but a lot of new information. Thank you both very much.
San Diego's earthquake hazard estimate has increased — and that's not exactly what most of us are eager to hear. But they say knowledge is power and the U.S. Geological Survey is out with an abundance of new knowledge about earthquake risks here and across the country.
The new U.S. National Seismic Hazard Maps show that areas of high hazard in California extend across a wider area than previously thought. And newly discovered offshore faults have raised the risk here in Southern California.
Nationwide, new data included in the USGS mapping finds Oklahoma's seismicity has increased to the point where the state has almost as many small earthquakes as California and have been linked to hydraulic fracturing.
