Play Live Radio
Next Up:
Available On Air Stations
KPBS Midday Edition

Report: Chance Of Mega-Quake Hitting California Increases

Stone falls off the face of a Napa Valley building in the wake of an earthquake, taken Aug. 25, 2014
James Gunn
Stone falls off the face of a Napa Valley building in the wake of an earthquake, taken Aug. 25, 2014

Report: Chance Of Mega-Quake Hitting California Increases
Report: Chance Of Mega-Quake Hitting California Increases GUEST:Pat Abbott, professor emeritus of geology, San Diego State University

Our top story a Midday Edition, new calculations show a bigger -- a risk of bigger earthquakes in California than previously thought. The United States geological survey now says there is a 7% chance of a quake measuring eight point all were greater in California in the next 30 years. The survey relies on a new understanding of how quakes can jump from one fault line to another and how California seems to have an interconnected fault system. Joining me to discuss the new study is packed at the, professor emeritus with San Diego State University jollity part -- Department. Welcome back to the show. It's good to be here. This latest survey was calculated on 300 outlines in the state. The last one back in 2007 only used 200 faultlines in California. How are we -- how researchers able to identify more false now? We do those in two main ways. Geologically we can recognize the fractures, the lines on the ground and map the offset rock and every time we had a little earthquake we complied with the ark three dimensionally. You can to find some planes custom fault planes for the service. Some of which don't even break the surface. For example can't even the big old Northridge earthquake had that was about the doesn't even reached the ground service. We now know where more those are. How do you. -- How do you actually find them? What equipment are the using? Basically it is the same kind of things you are using to looking at, We have far more information and by having far more information we are better able to talk to a probabilities are risks. This information about quakes being able to jump faultlines, is a new? It is not new. It is an increased understanding. There was a significant one of those in 1957 in Mongolia that really opened people's eyes. That is a long time ago but even our own Easter earthquake from almost 5 years ago, that was a very interesting one because that one jumped from one fault another fault to another fault. When you look at a map like when you look at it on television or in the newspaper or something it is like a simple line along the ground surface it is actually going down 10 or 12 miles deep and is commonly not just one ruptured surface. Is commonly multiple once. We knew from the Landers earthquake in 1992, we saw earthquakes, fault movements jump from one to another over 3 miles. Now we recognize for the bigger earthquakes they could jump as much as 7 miles. What I mean is that the movement along one fault, Lisa think you got to be in the default and the energy we just disperse and rocks around there. We now see it could jump as much as 7 miles over and trigger movement on another fault. The bottom line, the longer a fault moves both distance wise and timewise the bigger the earthquake because they are putting out energy at all times. If we now recognize more that one fault can trigger movement on another that means even bigger earthquakes are more possible. I see. Proof of quakes jumping faultlines, as you say, is sort of -- has been around for 50 or 60 years or so. They also point to the Japanese earthquake in 2011. A massive 9.0 earthquake caused a tsunami and flooding at the Fukushima nuclear plant. Is a knockout because we know this information and it can create more powerful earthquakes, is there now a chance for 9.0 in California? Well, we have three of the 50 states that have experienced 9.0 magnitude earthquake Alaska in 1964, second is whatever measure. Offshore from Oregon and Washington in the year 1700. That break actually comes down to just the northern most part of California. Not off the shore from San Francisco with a heavy populated areas. Technically I usually just say three states but it is the northernmost Europe California as well. Sokol we used to talk about the difference between slip fault lines and subduction quakes. And if you could briefly explained that it would be great but my larger question is are we with these connected poultry evaluating the potential size of a soap fault quake? Let's do it this way, the San Andreas Fault basically you draw that line along the map for this moment let's not going to a small scale -- small-scale complexity, is more or less a two dimensional feature so when one side flights pass the other that simple seismic waves. It is largely just a slide past movement. When you take subduction now you're taking a hunk of let's say the floor and rocks tens of miles of deep in your pulling a huge mass of rock cub volume of rock, down into the interior of the earth which just takes immensely much more energy. In other words, there is Oregon, Washington and Alaska with magnitude night earthquakes like Japan had in 2011, we're not going to have that in California. Are slide past faults simply cannot generate or give off that much energy. The old calculations, if I remember correctly, said that about seven points eight was about the biggest earthquake we could. In California. Give or take a little. Now we are hearing 8.0 or greater. Is that a very big change? Absolutely. Absolutely. That is one of the funny things about what, we use the Richter scale and Richter himself later said if I had any idea it was going to be so popular I would have put more thought into it and made a significant scale. What catches us as you say seven points eight or 7.9 or a .0, so? That is almost the same number. Is in a? No. That is doubling the energy. Let's put it this way, a magnitude 8 earthquake would be the same amount of energy is about 35 magnitude sevens. When you go up each 10th of a point of that scale it is huge differences in energy release. It is hidden. Is masked by the fact that you are just decimal point changes in the numbers. So, are we, therefore, prepared? Are building codes and so forth? Are earthquake prepared and systems? Is a significant -- sufficient for a .0 earthquake? There are so many different styles of buildings and bridges and so forth I'm not saying we're not going to the more stomached turning collapses but I really am proud of Californians in the sense of when we do have a major earthquake, 1933 Longford earthquake, schools class, ugly they weren't in session but then we changed the building codes. You don't build unreinforced masonry buildings anymore. I could come up through time. Every time we have a major earthquake in the year thereafter and only in the year thereafter you see changes to the building code, legislature pass laws. We have been quite aggressive and I think forward thinking and doing that. An example, the World Series earthquake back in 1989 in the Bay area, that is almost a carbon copy of the one it happened in Haiti in 2010 and 80, one fourth of 1 million people killed in the Bay area. -- In the Bay area, 60 people killed. Why? Holding codes. Enforcement of the building to those standards. We get better all the time which is not to say we don't have the risk of significant problems. With this new USGS survey, assessment of at risk assessment for earthquakes in California, can you see all the codes been changed? Were tied up a little bit? That is certainly possible. I think for the most part it really gets focused after a big event when you actually see something goes. Bike is a copy -- that is a collective we, talk about hundreds if not thousands of people when I say we can't we are looking at the 7.8 magnitude earthquake probability on the southern San Andreas. Why would things like that possibly jump from 7.8 jump from 7.82 8.0? That is the interconnectedness we talk about. The fact that one fault is not necessarily act singly and if it triggers another one you get to moving at the same time or one immediately right after the other. You are putting out more energy over a longer time and hence higher magnitude earthquake. Would you say people in certain areas may think about getting more earthquake insurance or something like that? Based on this? I wish -- I don't want people worrying were losing sleep or any this kind of stuff but I think it is only prudent to think about your house, your office, the places you are and look at it and think about what could happen during an earthquake. What is the problem? It is not the earthquake. Is a buildings, the possessions inside your house. For example, the Northridge earthquake a 10% of the deaths were from object flying inside people's houses. In other words, look at them, I like the bedroom, for example, -- if you say you spend eight hours a night there you have a big heavy mere hanging over the bed? Move it. Do have a chest of drawers it could topple over on the bed? Move it. Ceiling fan hanging over your bed? Move it. Kind of thing. It's not a worry thing, is just say what might fall or be thrown at me and move them were really securely fasten them down. I am speaking with Pat Abbott, he is professor emeritus with San Diego State University's geology department. Once again, pads, southern San Andreas Fault is named in this survey as the place most likely to host a large earthquake in the next 30 we have been hearing that for quite some time. I guess it gets closer and closer each time you hear it. Of course, your member geologists have their own timescale. You say we haven't talking about it for a long time I say heck know, we've only mentioned it once or twice. It's coming sometime in the next 200 years, it is going to happen. What is a? What you look at to make predictions like that? Can you actually take a measurement of the kind of tension the fault is under? There has been a lot of work on stress measurements and things of this sort to try to say -- UK -- when you say conceptually, you say what gives the energy to false to move in California? Is the opening of the Gulf of California. The Baja California peninsula, San Diego, Los Angeles, we are torn off from North America moving independently. You can calculate the stress but great difficulty of going from theory to measuring them in the field. It turns out to not be a simple. The bottom line is that comes up to be history more than anything. Take the San Andreas Fault cava northern one third moved in the 1906 San Francisco earthquake. 1906. The central moved in the 1857 earthquake. The southern segment moved prehistoric time but I'm digging trench coat measuring offsets and doing radiocarbon dates it looks like a last moved about 1690. Same fault. Forget the signs. Forget the computers. If the middle with 1906 -- which one to expect to move next? That does not move it will. The northern segment and central segment could move again before the southern one but if you're going to do probability analysis you would say the southern one onto the next. And keeping with it, the director of the Southern California earthquake Center is quoted as saying we're fortunate that seismic activity has been relatively low over the past century. Does that jive with the kind of data that you have about the frequency of earthquakes in California? Of course, Oliver analysis are hampered by the shortness of the record. When does California giggling? Really 1849 with the gold rush and all that so it's not a real long time or real long catalog. In the 1800s large earthquakes occurred much more frequently. They are defining it as six-point seven and above work let's take that size number. There was more of them, more frequent. I am going to generalize to the point of detailed inaccuracy here but I'm going to say in a tent -- 1800s of me one of those six-point seven type things on the order of once per decade, an overall frequency. 1906 San Francisco at 7.8 was so big that the way we viewed it was that removes so much stress from the rocks we haven't had as many earthquakes in the 20th century as they did in the 19th. That is an interpretation. That is not a proven fact kind of thing. In other words, that is where Tom Jordan, that is what he would be talking about when he is saying we really haven't had the experience as some of our people before us here in the state. As we were learning about the interconnectivity of faults in California are we also learning about the interconnectivity of faults across the globe? Good question. On the scale of like a San Andreas cava connectivity is more that we can see more three-dimensional he now for the connections. When you start talking about the globe now we are back to the plate tectonics scale. That is the thing from the 1800s, the old example, the old ring of fire a round the Pacific. Magnitude 9 earthquakes involved -- and volcanoes have the same cause cava subduction coupling down a potion play between the continents. In that sense there is a tremendous interconnectivity if you want to say going around the subduction zone, a plate is conducting time that is where we sort of forecast them. We talk about seismic gaps which is a fancy way of saying the plate hasn't subducted here for quite some time. I am wondering though, let's just leave it to California and its environs, if the developing understanding of what interconnectivity means when it comes to all lines, do you see that, potentially, being a way to give some advanced morning or that horrible word we always use top project, an earthquake? I will be blunt. Earthquake prediction short-term, no. No chance. Zero. Zip. Don't even have a good theory or a good hypothesis to test on that. We can tell you anything else, what, where, why. Were cast overlong length of time that we have no -- no weather forecaster type ability -- of ability at all. And none for -- none forthcoming. It may be that there is -- they are unpredictable. Maybe they're just random events. We don't even know that. That is the state of knowledge on that topic. Zero. Quick last question. A petition -- a potential a .0 or greater is a very big earthquake we are talking about. Does this change the game for California and earthquake safety? Do think? The fact that we see a greater risk, more frequency of having the large ones let me give you the worst case scenario. This is based on 1957 Mongolia. This would be -- I'm going to take Mongolia and put it in Los Angeles, San Andreas alt moves in a big event going on to the East and that connects with and causes a Northridge earthquake at the same time. That is the kind of things, that is why we say the really big ones have a greater possibility than we thought and at the same time just the large ones like the six-point seven we look at as one every six-point three years rather than for .8° a thing. That is kind of scary. Scary but, building codes here are good. If you furnish grown houses right and don't have a eucalyptus tree hanging over your house or things like that then you should be fine. Take down your mirrors in your bedroom. Please do. [ LAUGHTER ] I have been speaking with Pat Abbott, professor emeritus with San Diego State University geological department. Thank you so much. Thank you.

Scientists are virtually certain that California will be rocked by a strong earthquake in the next 30 years. Now they say the risk of a mega-quake is more likely than previously thought.

The chance of a magnitude-8 quake striking the state in the next three decades jumped to 7 percent from 4.7 percent, mainly because scientists took into account the possibility that several faults can shake at once, releasing seismic energy that results in greater destruction.

While the risk of a mega-quake is higher than past estimates, it's more likely — greater than 99 percent chance — that California will be rattled by a magnitude-6.7 jolt similar in size to the 1994 Northridge disaster. The chance of a Northridge-size quake was slightly higher in Northern California than Southern California — 95 percent versus 93 percent, according to a report released Tuesday by the U.S. Geological Survey.

"California is earthquake country, and residents should live every day like it could be the day of a big one," USGS geophysicist and lead author Ned Field said.

The latest seismic calculations largely mirror previous findings issued by the USGS in 2008. Back then, scientists also determined that California faced an almost certain risk of experiencing a Northridge-size quake.

The new report included newly discovered fault zones and the possibility that a quake can jump from fault to fault. Because of this knowledge, the odds of a catastrophic quake — magnitude 8 or larger — in the next 30 years increased.

There is a 93 percent chance of a magnitude 7 or larger occurring over the same period and a 48 percent chance of a magnitude 7.5 — similar to previous estimates.

Thousands of quakes every year hit California, sandwiched between two of Earth's major tectonic plates, the Pacific and North American plates. Most are too small to be felt.

Of the more than 300 faults that crisscross the state, the southern segment of the San Andreas Fault — which runs from central California to the Salton Sea near the U.S.-Mexico border — remains the greatest threat because it hasn't ruptured in more than three centuries.

The report found there is a 19 percent chance in the next 30 years that a Northridge-size quake will unzip the southern section compared to a 6.4 percent chance for the northern section, partly because it last broke in 1906.

The southern San Andreas is "ready to have an earthquake because it's really locked and loaded," Field said.

The report is a forecast, but it is not a prediction. Experts still cannot predict exactly where or when a quake will hit anywhere in the world.

In recent years, the USGS and several universities have been testing an early warning system designed to detect the first waves of a jolt and send out an alert before the slower-moving damaging waves. Proponents have said a few seconds of notice can allow trains to slow down, utilities to shut off gas lines and people to duck for cover. The public alert system — still in pilot phrase — needs more funding before it can be rolled out statewide.

Report: Chance Of Mega-Quake Hitting California Increases

What questions do you have about the Statewide General Election coming up on Nov. 8? Submit your questions here, and we'll try to answer them in our reporting.