# PubTalk 9/2018 - Hayward Earthquake

Video Transcript

## Detailed Description

Title: The 150th Anniversary of the Damaging 1868 Hayward Earthquake: Why It Matters and How We Can Prepare for Its Repeat

• The Hayward Fault in the heart of the Bay Area is one of the most urbanized faults in the US.
• Studies of the fault reveal that it has produced 12 large earthquakes in the past 2000 years spaced 100-220 years apart.
• There is nearly a 3 out of 4 chance of a damaging M6.7 earthquake in the SF Bay Area in the next 30 years.
• Updated building codes, building and home retrofits, planning, and training are necessary to mitigate earthquake effects.

## Details

Date Taken:

Length: 01:28:30

Location Taken: Menlo Park, CA, US

## Transcript

[Silence]

This video is a one-hour presentation of the USGS Evening Public Lecture Series titled, The 150th Anniversary of the Damaging 1868 Hayward Earthquake. The presentation is being hosted in the USGS Menlo Park facility. The host welcomes the audience and introduces the speaker, Tom Brocher, who is a USGS research geophysicist. As Tom is giving his presentation, he is continually pointing to and referring to slides presented on the screen. The slides are a mixture of charts, graphs, and photos. At the end of the presentation, there is a question-and-answer session with members of the audience.

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[Music]

[Applause]

- [audio very quiet] Thank you, Leslie. And thank you, everyone, for coming out tonight. Before we get started, I’d like to ask you, [audio at normal level] who was here for the 1989 Loma Prieta earthquake? Okay. Yeah. Pretty impressive. Who is a homeowner in the Bay Area? Okay. Who is a Cal grad? [laughter] Any Cal grads? Okay. Well, then, this talk has something for everyone. [laughter] That’s good. I don’t have to revise my talk. Geologists often say that the present is the key to the past. That we look at processes going on today, and they help us understand what happened a long time ago in Earth’s history. But in my talk today, we’re going to turn that around. And we’re going to look at previous earthquakes in the Bay Area as a guide to what we might expect from future earthquakes. So our focus today is going to be on the Hayward Fault and the 1868 Hayward earthquake whose anniversary we are commemorating, as Leslie said, next month. After we talk about that earthquake, then I’d like to tell you a little bit about the earthquake forecast in the Bay Area for the next 30 years or so. And then we’re going to do a quick review of things that you can do to help make yourself safer during an earthquake and to allow you to recover more quickly from an earthquake. So that’s the game plan. But, before I get started, I want to dedicate this talk – my talk tonight to a very dear colleague who just passed away a week ago, Jack Boatwright. And he was – he’s been very instrumental in learning about – telling us about hazards in the Bay Area – earthquake hazards – and in promoting earthquake resiliency throughout the Bay Area. So he’s – he was a great guy, and we’re going to miss him a lot. And before – the next thing I want to do before we really get started is, earthquakes are scary, okay? I get that. I study earthquakes, but I’m still scared of earthquakes. But I can show you a lot of facts and figures, but the bottom line is that most of us are going to be fine after the earthquake. And we’re not even going to be hurt by the earthquake. And I show you this picture just to give you a – oh, let me – let me fix the mouse here if I can. Should have done this before. Sorry about this. So here’s a picture of a dairy farm in Marin after the 1906 earthquake. So you can see the San Andreas Fault goes right this fence. Rips this fence apart and drags it about 10 feet to the north. Now, that’s what geology students look at, and they move on to the next slide. But what I want you to look at are all these buildings. So this is a magnitude 7.8 earthquake, and a stone’s throw away from the San Andreas Fault with this big offset of the fence. Those buildings look fine, don’t they? You could live in that building. You could live in those buildings. So that’s why we know that most of us don’t even get hurt during earthquakes. So all my remarks tonight are not designed to scare you. They’re designed to help educate you and give you some pointers – some very practical and easy things that you can do to make yourself safer during earthquakes. So that’s what I hope you’ll take away from this. So let’s start with a history of earthquakes in the Bay Area. This is a timeline. It starts with the Gold Rush in 1850. Goes all the way to the present. And these circles are earthquakes. So this is the 1989 Loma Prieta earthquake, magnitude 6.8, 6.9. This is the 1906 earthquake, magnitude 7.8 – 10 times bigger. And this is the 1868 Hayward earthquake. About 10 times smaller than the 1906 earthquake. One thing I want you to notice is, look at all these earthquakes that happened between the start of the Gold Rush and the 1906 earthquake. In the Bay Area, you knew that this was earthquake country. Because you were feeling a big earthquake every few years. Okay? Look what happened afterwards. Almost no earthquakes. And the prevailing wisdom is that the 1906 earthquake was such a big earthquake that it removed the stress out of the system. And stress is what – is the fuel for earthquakes. So if there’s no stress, there’s no earthquakes. So after 1906, we’ve had very few. The biggest was the Loma Prieta earthquake, and then we’ve had this magnitude 6 in Napa about four years ago. Why is there such a big hazard in the Bay Area for earthquakes? Well, it’s simply because we live so darn close to earthquake faults. And the red lines here are the earthquake faults. Let’s see. To orient you, we’re down here in Menlo Park. Here’s San Francisco up here, Oakland. Here’s the bay. This red line is the San Andreas Fault. And this red line is the Hayward Fault. So you can see that, between those two faults, almost all of us live pretty close to a major earthquake fault. Now let’s – what I’ve also shown in this figure is these yellow outlines. This is where people lived back in 1906. Okay, so you can see people lived on the east side of San Francisco. They lived in Oakland. And they lived in San Jose, which is off the map. And the peninsula, for the most part, was just a series of train stations with very small towns between them. So there were almost nobody living on the peninsula back then. But now this gray – this blue area shows you where we live now. So we have 10 times as many people as we did back in 1906. And look, we live right on the fault now. Whereas, back in 1906, really nobody lived on the earthquake faults. And now we do have people that are living right on top of the faults. So to drive that message home, this is a map that shows the population density by ZIP codes in the Bay Area. And I’ve just drawn the Hayward Fault. This big dashed line here is the Hayward Fault. And you see the big populations of Oakland and San Leandro, Hayward, Berkeley, they’re right on top of the Hayward Fault. And so now we have a population of over 2-1/2 – maybe closer to 3, or maybe even more, people that live in harm’s way very close to the San Andreas – the Hayward Fault, sorry. Let’s look back – let’s start talking about the 1868 earthquake. And the map you’re looking at is a map of the intensities of shaking that were experienced in 1868. And you can see the hot spots here were in San Leandro, Hayward, and Fremont along the Hayward Fault. But throughout the Bay Area, you can kind of see this yellow, yellow-green, color, which is down to – sorry, I’m having trouble with the mouse here. It corresponds to what they call light to very light shaking. Well, this is shaking that produces damage. It’s called “light,” but it’s still damaging. So the whole Bay Area would have experienced damage. The black line here is the part of the Hayward Fault that we think actually ruptured – cracked and produced the earthquake. So, at the time, it was called the Great San Francisco Earthquake. Because it was the biggest earthquake that had ever happened in the Bay Area. And it retained that title for 38 years until 1906. And it had a magnitude of about 6.8, so about the same size as the Loma Prieta earthquake. But whereas the Loma Prieta earthquake happened down here, this is smack-dab in the middle of the Bay Area. So very different. It produced 30 deaths. Five in San Francisco. So it is one of the – still one of the most deadly earthquakes in California history. As I said, it produced heavy damage in San Leandro, Hayward, and Fremont, which had a total population of 2,000. Okay, the population of those cities now is over 500,000. So the population has grown more than 200 times in that area of the bay. The total Bay Area population in 1868 was about a quarter million people. So it’s about 8 times – it’s about 30 times larger now. So we have many more people that live near the Hayward Fault. Let’s take a photographic tour of the damaged – strongly damaged areas. And these are photos from the 1860s. At that time, there was – nobody had their own amateur camera. There were no Polaroids or anything. If you wanted a photograph, you had to hire a professional. So we only have about 50 or 60 photographs of the 1868 Hayward earthquake. So you’re going to see a large fraction [chuckles] of those photographs tonight. But the top shows you a picture – a widescreen photo of what San Leandro looked like in the 1860s. Again, it had a population of about 500 people. But it was – the county courthouse – here you can see the county courthouse building. Here’s a little bit expanded view of the courthouse building before and after the earthquake. And you can read the description of what the shaking was like in San Leandro, and this was published in basically the version of the SF Chronicle of the day – the San Francisco Morning Call was the big newspaper in the Bay Area. And they said things like, buildings were terribly shaken, adobes were thrown to the ground. This is unreinforced masonry that – we know that’s not very good construction for earthquakes. Brick structures, unreinforced masonry buildings were damaged. Even wood-frame buildings were damaged. And this courthouse was shaken down. Also in San Leandro, we have this photograph of the Estudillo House, which is a unreinforced masonry building. And the damage is fairly typical for this kind of building. And that’s why they’ve all been largely retrofitted in the past 20 years or so. But what I love about this photograph is that these 12 people in this photograph, and they all look like they’re going to church. [laughter] And that’s because – I guess it’s because everyone – you paid for this photograph to be taken, so you got dressed up, and you made sure that you looked nice. [laughter] So how’d you like to be all dressed up and sitting next to some broken-up building like that? But anyway, that’s the kind of damage that was seen in San Leandro. Here’s a picture of Hayward. Back then, it was called Haywards. And here’s their hotel up here. And, again, about a population of about 500 people. Practically not a house was left on its foundation. Many buildings were much damaged. And we’ll see an example of a flour mill in Hayward that was very damaged. And this flour mill was where the Hayward BART station is now. [laughter] And you see this – it’s hard to see in this photograph, but there’s some very heavy equipment up in this second story. So the building was top-heavy. So it got shaken to the side, and it just kept going. Fell over. This is the mission in Fremont. It’s called Mission San Jose, which is kind of confusing. But it’s in Fremont. And it’s there today still. This is a picture of before the 1860s. And you can see the – you can see the shadow of the photographer here. We don’t have a photo after the earthquake, but we have a drawing. And you can see this, again, is adobe or unreinforced masonry. So it was very heavily damaged as well as other buildings near the mission. This is what San Francisco – downtown San Francisco looked like in the 1860s. It was mainly two- or three- or four-story buildings, mainly unreinforced masonry. Some wood-frame buildings. You can see the wharf and the ships docked at the wharf in the background here. That was the coastline at the time. That is not the coastline today. The coastline is farther out to the bay. So this next – this is a Google map that shows you downtown San Francisco, the Financial District. Here is Market Street. And the Ferry Building would be – sorry. The Ferry Building would be just off here. Here’s the – here’s the Embarcadero. This is the Embarcadero Center. Trans Am Building. And what this red is, this is all landfill. Okay, this is the area of landfill. So this used to be bay muds, marsh – you know, muddy marsh tide-flat-type deposits. Or it was a little deeper, and they filled it in to make more land. That was the – that’s what you did back in the 1850s and 1860s. And all these pushpins are places where the buildings were damaged. And you can see there’s a very high percentage of these that are located in this region of landfill. Again, this is the Financial District of San Francisco. Let’s look at one of these buildings. This right in the center of the screen here. So this is a photograph of the buildings at that location. And there are two buildings – two stories. And they’ve kind of tilted towards each other, and the top parts of each building have kind of smashed into each other. So you can see, as a result of that smashing together, there’s been a big crack formed in this building. So what happened is that these buildings were heavy enough that they settled into the landfill. And they didn’t settle perfectly level. They tilted downward. And to drive that point home even a little bit more, this is a map that we made of what San Francisco back in 1868 would have looked like. And you can see nothing out on the west – Sunset. Nothing out there. You can see a lot of streets in the Financial District. And this would have been Chinatown. This is Chinatown and North Beach. That part was settled. And then a little bit south of Market down here. But nothing else. And there’s really nothing in the peninsula. These diamonds show you the places where we have either damage reports or reports about how strongly the earthquake was felt. And these colors reflect the shaking – the level of shaking. So this – but I want you to look at the coastline. Because it looks different than today. And look, there’s no Treasure Island. There’s no islands off here. What does it look like now? Well, that’s what it looks like now. Now we have a Treasure Island. We have big islands off here in Alameda. Look at all this. I’ll go back so you can get another look at that. You see how much of the east side of San Francisco has been filled in? That’s all landfill, and it has a stronger color here because it probably would have shaken harder during the 1868 earthquake had it been there. So that’s one concern for us. But there is some good news from the 1868 earthquake. And that is, because of the earthquake, the designers and builders realized that this is not Kansas. We have an earthquake issue in the Bay Area. And you have to design your building with earthquakes in mind. And so who’s the Cal grad? Do you remember South Hall? Okay. Built in 1873, five years after the earthquake. So it’s one of the first buildings at UC-Berkeley. And these red lines show you the locations where iron bars or iron ties were built into the building with the view of making the building stronger and more resilient to earthquakes. So this is one – perhaps one of the first buildings built in the Bay Area that was designed and built with earthquakes in mind. But there were buildings throughout San Francisco where the same thing, or maybe even better things, were done. And we think they played a role in the 1906 earthquake in that, when you look at photographs from the 1906 earthquake, after the earthquake, but before the fire, a lot of the buildings looked pretty good. They did pretty well in the earthquake. And we think this may be part of the reason. And there’s a great book called Bracing For Disaster that you can read about the impact of this earthquake and building practice in the Bay Area. Well, one thing we’ve learned fairly recently in that – four years ago, we had that magnitude 6 earthquake up in Napa. It did kill one person and did a lot of damage, especially to the winery industry up there. But we had – I think the earthquake was around 3:00 in the morning. And we had geologists in the field by that morning looking to see what they could find. And what they found was this one road where the earthquake crack had actually come up all the way to the surface and slightly shifted this road to the north, this way. So that’s the day of the earthquake. And then they went back for some reason – don’t know why. They went back to the next day. And look, that crack is bigger. Well, what’s going on? There hasn’t been another earthquake. So what’s gone on is that the magnitude 6 earthquake did not cause the ground to move far enough everywhere. And so it started a process of very slowly moving to catch up with other parts of the fault where the motion was bigger. And that motion persisted for weeks. So now, let’s not – so this is a road with this strip painted on it. Let’s think now, this is a pipe that’s in the ground. Okay? So the first day, well, it’s offset that much. Well, maybe that pipe’s okay. But, as this crack grows bigger and bigger, maybe that pipe doesn’t do so well. So we could be saying that, on the Hayward Fault the next earthquake, where we could be having the case where the first day, many of the pipes are okay. Not too bad. Still work. But in the days and weeks and maybe even the months to follow, they become more and more stretched to the point where they fail. So we could see a cascading impact of more and more and more pipe failures over time. And the reason we think this is a – may be the case for the Hayward Fault is that we have steady ongoing what geologists call creep. Steady motion along the Hayward Fault that moves at about the rate of 1 inch every five years. So here’s a – here’s a stone wall that crosses the Hayward Fault in this location. And it was built, I’m guessing, about 50 or 60 years ago. And I’m sure it was built very straight. But over 50 or 60 years, the motion of the Hayward Fault has dragged this whole part of the wall northward. So we see – on a continuing basis, we see pipe failures along the Hayward Fault associated with this steady creep. So, when we see this kind of behavior, we think to ourselves, well, maybe we’ll see a lot of [coughs] – pardon me – we’ll see a lot of creep after the earthquake. Where does the Hayward Fault run? [laughter] Okay. All you Cal grads. [laughter] It runs end zone to end zone through the football stadium. And I can tell – afterwards, I’ll tell you what section you can sit in [laughter] for an especially exciting ride [laughter] during the game. But we have maps that show the location of the fault very accurately. And this is a map that’s actually made using Lidar data. It’s laser that we mount in an airplane or a helicopter. We shoot it down, and we can image the – whatever bounces – trees and things that bounce – buildings that bounce back those laser – back to the plane. And using computer algorithms, we can take away the trees. So we’ve done that, and you can see this – so this is the bare ground. And you can see – and it helps us find faults much more readily. In fact, it does a really nice job of showing you – this stream here has come downhill, met the Hayward Fault, and then the Hayward Fault has dragged it northward. And this kind of offset geologists use over time to measure what the rate of motion is along the Hayward Fault. So let’s talk – that’s sort of a good segue into the forecast for earthquakes in the next 30 years. This is – the USGS updates the forecast for earthquakes in the U.S. every four or five years to make sure that the maps include the most recent and best-available science. So the map on the left is you – of all the earthquakes that had been recorded in the Bay Area for about the past 40 years. And you see, here’s the Loma Prieta earthquake down here – the ’89 earthquake. Here’s the Napa earthquake. Let’s see. Up here. Lot smaller. And all these little dots, some of them are as small as magnitude 2 to 3. So these, we probably wouldn’t even feel. And every day, we have earthquakes in the Bay Area that we just don’t even feel. So somebody says, well, we had an earthquake today. Well, yeah. [laughter] Yeah. Of course we did. Happens every day. You know, so what? But, over time, we get a nice image of where the faults are. You can see this is the Hayward Fault. This is the Calaveras Fault. This is the San Andreas Fault. And some of the other faults in the Bay Area. And so here’s another view of the same area where we’ve drawn on the faults. And these numbers are the likelihood, or the probabilities, of a damaging earthquake produced by that fault in the next 30 years. So San Andreas Fault, where we’re close to here, about 22%. Calaveras Fault, about 26%. The Hayward, 33%. And some of these other faults, 16%, so on. Overall, when we look at all the faults in the Bay Area, and I’ll zoom in here sort of in the Menlo Park area – we’re down here – it’s about a 72% chance, or a 3 out of 4 chance of a damaging earthquake in the Bay Area in the next 30 years. Now, if I went to Vegas, and they gave me 3 out of 4 chances of winning, I would walk home a billionaire, right? I would make money hand over fist. So this is a pretty high likelihood. These yellow lines are smaller faults that we do not think are capable of producing a magnitude 6.7 earthquake. But they probably could produce a magnitude 6 earthquake like we saw in Napa. Or maybe even a 6-1/2. And those would be damaging in their own right. But these colored lines – you know, the San Andreas Fault, the Hayward Fault, Calaveras Fault, the Greenville Fault, those are the biggest actors. Well, why are we so concerned about the Hayward Fault? Well, this is another timeline, but this one goes back – it doesn’t go back just to the Gold Rush, which would be back here. It goes all the way back to the birth of Christ. So it’s about 2,000 years. And each of these bars is an earthquake. So there’s – we have a geologic record of 12 earthquakes. And this says Earthquake 11 because this one says Earthquake 9.5. It’s very confusing. But, you see, how we get these dates is that we dig a trench across the earthquake fault, and we look for soils that have been disturbed by faults coming through the surface. And we look for the next soil on top of that that’s not deformed – that’s not disturbed by that fault. So then we get a date using radiocarbon methods on that soil that has the fault in it. That’s the oldest the earthquake could be. And we date the soil on top of it. That’s the youngest the earthquake would be. And then we get a bounding range. And some of these earthquakes, you can see this range is pretty broad – a couple hundred years, maybe. Other cases, it’s pretty narrow. We know the age of that earthquake within probably 30 or 40 years. So the earthquakes do not happen like clockwork. It’s not periodic. But if we draw lines through these data points, if we look at all these earthquakes going back almost 1,900 years, we get an average of about 160 years between earthquakes, plus or minus about 60 years. Okay? If we look at the past nine earthquakes that go back over 1,000 years, we get about 150 years between earthquakes, with, again, about 60 years – plus or minus 60 years. And if we just look at these last five earthquakes or so, then we get a earthquake every – about every 140 years, with, again, about a 60-year plus or minus. So let’s look at this part of the earthquake record a little more closely with all – without all this detail. So here’s a timeline that goes back to 1134 up to the present. And here – so here are all these earthquakes. And I’m just showing you the best estimate of the date for that, remembering that there’s uncertainty in that, okay? But those are the best estimates of the day. And then – sorry. These are the recurrence intervals between – or, the intervals between these two earthquakes. So 183 years, 158 years, 153 years, 97 years, and 142 years. So now we’re 150 years. So that’s why we think the Hayward Fault is capable of producing an earthquake now. Or anytime in the next 60 years. This is kind of a Euro-centric set of events starting with the Magna Carta and the Black Plague and Columbus reaching North America and the New World. The founding of the missions. And the 1906 earthquake. So in recognition of the fact that it’s been 150 years since the last big Hayward Fault earthquake, the USGS conducted a study of what the impacts of another Hayward Fault impact might – earthquake might be. Not necessarily a carbon copy of the 1868 earthquake, but a plausible earthquake. And there were four key findings. One is that there's likely to be long-term impact on the delivery of drinking water in the – in the Bay Area, especially in the East Bay along the Hayward Fault. Many, many fires could be started by the earthquake. There may be significant housing needs for lots and lots of people. And if the earthquake happens during the business day, there could be quite a few people who are either trapped in the building or trapped in elevators trying to get to work or leaving work. Let’s talk about a few of these. Let’s start with drinking water because that’s one that I’m very concerned about. So the – and there are copies of a fact sheet about the HayWired scenario, as we call it. So there are many more detailed numbers, so I don’t want to overload you with a bunch of numbers. But in San Francisco and Santa Clara Counties, they’re probably the best position, and they might only take a month or so to fully restore their service. San Mateo County, it could take up to three months to fully restore the service. And in Alameda and Contra Costa Counties along the Hayward Fault, it might take several months. Now, there are a lot of assumptions that go into these estimates, and there’s a lot of uncertainties. I think one of the key assumptions is that the crews available to do the work to repair all the pipe breaks are only those crews that we have in the Bay Area. And I think after a major earthquake in the Bay Area, there will be crews coming in from around the country to help speed up that process. So I don’t take these numbers too seriously, but they are an indication that you might want to have some water stored away, just in case. Here’s a map that shows where the fires might be started after the earthquake. And, again, here’s where the fault is. Here’s where the rupture will be. We expect most – and don’t look at the numbers of dollars of loss. Just think of this in terms of the numbers of fires that are started. So we expect the most along the Hayward Fault, which is not a huge surprise. But look, down in San Jose, there will be some fires started. In Menlo, in Palo Alto, there will be fires. There will be fires in the peninsula. Now, again, the numbers of fires, there are a lot of assumptions that go into these estimates. A lot of uncertainties. But I just want to plant in your mind that fires is not just an issue in the East Bay. It could be an issue on the peninsula as well. And another point of the HayWired scenario is that – and we know from the Loma Prieta earthquake – is that there were lots and lots of aftershocks, right? And they went on for months. So – and some of these will be very large. They will be magnitude 5, maybe even a magnitude 6. So we have to be prepared for aftershocks. So let’s start talking about what we can do to make ourselves safer from earthquakes. So Leslie mentioned drop, cover, and hold. And that’s kind of a mantra we teach as earthquake people. But I want to explain why we – why we have that mantra, okay? Why do we tell you to drop, cover, and hold? Well, there are two ways people get hurt in California from earthquakes. The first way is that they lose their balance. The earthquake is so big, they lose their balance, and they fall. And they break their wrist, or they break their forearm, or they break their hip when they fall. Okay? So that’s why we want you to drop to the ground. So you don’t get pushed to the ground. And so you don’t get injured being pushed to the ground. You drop to the ground in a very controlled, safe way. Okay? The second way people get hurt in earthquakes is that things start falling from the ceiling, from the walls, from the bookshelves. They’ll be coming at you from every direction. So we want you to get some cover to protect your head and your torso, at least, from things that are falling so that you don’t get injured. And the last thing we ask you to do is, if you’re under a table or a bed or something that – desk that can move, well, what happened in the 1906 earthquake was that the strong shaking – it’s really fascinating to read the accounts of the people that survived the earthquake because they talk about the shaking lasted for 45 seconds. And the things – furniture just moved around the room, round and round and round for 45 seconds. So if you’re not holding onto your desk, you’re not underneath it very long. [laughter] Okay? So you’ve got to be holding on to whatever is protecting you to make sure it’s still protecting you. The other thing we know for sure is that building retrofits work. And there was an unplanned experiment down in Santa Cruz where a couple bought two identical houses as an investment. One house – well, the houses were identical. Same design, construction – identical houses. And I think they were side by side. So they had retrofit one house, and they were just about to start on the next house, and the ’89 Loma Prieta earthquake hit. So the house that was retrofit sustained very little damage. $2,000, the damage, at the very most. The other house that had not been retrofit basically got torn apart by the earthquake. And the damage took a few hundred thousand dollars’ worth of investment to repair. So this was an unplanned experiment, but it demonstrates for sure that earthquake retrofits work. And I’ll talk a little bit – a little bit later in my talk, I’ll talk about how you can retrofit your house. But the type of home retrofits I’m talking about, they cost about$10,000 per house. So not a very large investment when we think about a million- or a million-and-a-half-dollar house. Okay? The other thing that we’re developing – and we continue to develop and push up as appropriate is this concept of earthquake early warning. And sometimes facetiously, I call this “earthquake last warning.” Because the earthquake has started. So you’re not going to have time to go retrofit your house. [laughter] You’re not going to have time to go to the grocery store. You don’t have any – you have about 10 or 15 seconds. And the way it works is that there’s – the earthquake fault – say the San Andreas Fault – the earthquake starts. And the earthquake produces two types of waves – a fast wave, which isn’t very damaging, and a slower wave, which is. So we can detect the earthquake on this first fast wave if we have a bunch of sensors. I think of these as trip wires. So if we have a bunch of sensors out on the ground, we can very quickly locate that earthquake and estimate its magnitude. And then we can broadcast that information electronically ahead of the earthquake and give people who haven’t yet felt the earthquake some warning. So that’s how it works. As I said, we need sensors. These are two maps – one of Japan, one of California. Same scale. You see all the sensors in Japan, where they have a functioning earthquake early warning system, and it has worked in the past. This is what we have in California. So we’re pretty good in L.A., and we’re pretty good in the Bay Area. But most of the state, we’re not very good. So we’re only about half – a half to two-thirds built out. So this is something we’re actively doing. It’s dependent on our level of funding. We can only do as much as we get funding for. So that’s part of the puzzle. But here’s a figure that gives you some idea of what timing – what kind of a warning we’ll get. So this is a magnitude 4.4 earthquake in Berkeley. Was felt pretty strongly up there. And that earthquake up there would have given us about 10 seconds of warning in Menlo Park/Palo Alto. And if you lived in Burlingame or South San Francisco, where I live, I would have had about 5 seconds of warning. And if I lived in Berkeley, I would have gotten no warning. Zero. Because there’s not enough time between the fast wave and the slow wave for us to process the information and give you a warning. Just won’t happen. But if we move this set of circles around – you can kind of see, if we have a fault – earthquake over here, we can get about the same amount of warning. So roughly, we’ll get 10, 15, maybe 20 seconds of warning, depending on where the earthquake is in the Bay Area. Now, if it’s very far away, way up north somewhere, then we could get a lot more warning. But, for a Bay Area earthquake, you should think, well, I’ll get 10 or 15 seconds’ worth of warning. And that doesn’t sound like very much time. But remember our drop, cover, and hold on. That takes some time to do. So this warning would give you time to find a really good spot that’s going to give you some cover and get on the floor so that you don’t get hurt during the earthquake. Another use – and let me back up. Another use is in schools. Kids can get underneath their school desks and be protected that way. BART is already using this system to slow down its trains. And with 10 seconds of warning, they can slow down a train about 30 miles an hour. So hopefully that will reduce injuries and maybe even reduce the chance that a train might go off the tracks and derail. So hopefully that will reduce the amount of injuries that people receive on BART. So to continue this theme of, okay, what are some very practical and not very expensive things that I can do, starting tonight, to make myself safer? We have lots of – lots of information on these guide books, which are in English or Spanish and English or in Chinese, Korean, and Vietnamese. They’re all available on this earthquakecountry.org website. But have you thought about how you’re going to charge your cell phone when there’s no electrical power for a few days? How are you going to do that?

- [inaudible]

- Use your car. Are you going to use a solar panel? Portable solar panel? You should think about that. Because there won’t be – there may not be power for a few days. Because the first thing that happens in an earthquake is that PG&E shuts off the electric power because they do not wish to start fires caused by leaking gas. So we know for sure that there will not be power until PG&E can inspect those areas and make sure there’s not gas leaks. You should have a kit. You can buy these. And if you do that, make sure that you have plenty of water in it. And that you have your prescription medication. Because nobody else is going to have your prescription medicines. If you have pets, and you have to evacuate, hopefully you don’t have to evacuate your house, and so you can just stay there. But if you do, sometimes shelters do not take pets. So it would be good to think about, well, what neighbor could take care of my pets, or what friend, or whatever. In a strong earthquake, the glass may break. So if you’re in bed, which is not a bad place to be during an earthquake, by the way – if you’re in bed, stay in bed. You might want to put a pillow over your head. But when the shaking stops, and you want to get out of bed, you might be stepping on broken glass. And you’ll cut your feet that way. So you want to have a pair of shoes and maybe a flashlight that is, what, tied to the bed. So when the bed is going like that around your room, it is still there when you need it before you have to step out on the ground. Okay, now who’s got a big, heavy mirror or picture right over their bed or their sofa or your office desk? Not a good idea. The first thing that’s going to happen is that’s going to come down on your head, and you’re going to be injured before you know it. So we don’t want to do that. Or you want to go out and buy these special picture hooks that will prevent the pictures from coming off. So, again, there’s going to be no power. So if I was going to refill my car to go home – I’m on empty – well, guess what, you’re not getting any gas. Because with no power, there’s no way to pump gas. So I always keep my car at least half-filled with gas so that I have some gas in my car in case the earthquake comes. Doesn’t cost me anything. I might visit the gas station a little more frequently, but just – it’s just a matter of lifestyle. Your hot water heater is an important – may be an important source of water to you following the earthquake. You want to make sure it’s well-strapped and does not fall over. The other reason you want to make sure it doesn’t fall over is that, if it does fall over, it might break the gas pipe. Now you have a source of gas. Probably have something hot. You might start a fire. So you want to prevent fires by not – making sure that your hot water heater is really well-strapped. The advice before the Loma Prieta earthquake was to turn off your gas after an earthquake. Everyone did that. The issue is that PG&E wants to be the one to turn it back on. Okay? They had a few things to worry about after the 1989 Loma Prieta earthquake. Some people didn’t get their gas restored for three weeks. That’s a long time without a hot shower. So now the advice is, if you smell gas, okay, something’s leaking. If you hear the gas leaking, you know, behind the wall, okay, you’ve got a gas leak. Turn off your gas. But if you don’t think you have a problem with your gas, leave it on. It’s a great – it’ll be a great resource to you after the earthquake. Have a plan for how you’re going to connect with your family that does not include calling them on the cell phone. Okay? We had a magnitude 5.4 in Alum Rock about 10 years ago. You could not get – you could not dial out on your cell phone 10 years ago with a magnitude 5.4 So you can imagine, with a 6.8, forget it. Not going to happen. You can try texting, but you should also have a plan – well, if I can’t reach you, I’m going to meet you at this Safeway or this hardware store or at the school across the street – just a physical place where you can meet that is your default place to go to. Now, here’s how you strengthen your house. If you have an older house – by older, I mean before the – say 1985, it probably wasn’t built to the current building code. So if you have a crawlspace underneath your house, and you can see these vertical 2-by-4s, what you want to have done is, you want somebody to come in and make sure the house is properly bolted to the foundation. Because houses can shift off of foundations in earthquakes. So that’s one very important step. The other step is you just nail a bunch of plywood to all these 2-by-4s that you see in your crawlspace. And you nail all around the edges here, and you nail down the vertical 2-by-4s. And that makes that part of the wall very stiff. So it doesn’t want to tilt over and fall over. And that will – that will – that’s what that couple down in Santa Cruz had done to their house, and they sustained very little damage to their house. Again, this is – this is about a $10,000 project, or you can even do it yourself if you’re so inclined. The other thing you can do that costs nothing, you can take a course in how to put out fires from your fire department. It’s part of what they call Citizen Emergency Response Training. It’s about a 20-hour course, and you learn other things, like how to do emergency first aid, triage, how to search buildings – all that kind of very useful information in an earthquake. And so if we all knew how to put out small fires, our fire issue will be much, much less. As Leslie mentioned in her introduction, October 18th, a Thursday, is going to be the next big ShakeOut drill. It’s at 10:18 in the morning. And I think there’s probably 10 million people signed up to do the drill in California. It’s a good chance for you to think about, okay, if I’m in my house, where would I – where would I go, you know, to protect myself during an earthquake? If I’m at the office, where would I go? It’s good – if you have an emergency kit, you know, when’s the last time you looked at it? Maybe it’s time to go into it and – oh, maybe – this food is 10 years old. Maybe I want to update my food. So it’s a good – it’s a good opportunity to do things like that. And the last thing is that, on the actual anniversary, which is October 21st, there’s going to be kind of an earthquake fair in Central Park in Fremont. And these red lines are the Hayward Fault. Runs right – so the fault runs right through the park. In fact, the old Fremont City Hall was right there over the fault. And you can go to that building and see the cracks through the foundation and see how they have shifted over time. And that’s an earthquake exhibit now. So they’re having a festival on October 21st, and you can learn more about the Hayward Fault, and there will be providers that will tell you about things that you can buy or do to help make yourself safer. So I think I’ll try to summarize what I’ve been talking about. So we live in earthquake country. A damaging earthquake is coming. But we can prepare for it, so let’s go ahead and do that for the benefit of our families. Thank you very much. [Applause] - I know that many of you may have questions, and the usual routine is, we have a couple of microphones set up, one in each aisle. I ask you, please stand up and walk to the microphone if you have a question – and see, somebody already knows the routine. Because a lot of people watch our lectures. We record them digitally, and we live-stream them, so hi to internet-land. And we want everybody to be able to, not only hear the question as you ask it, but to have it recorded for the future as well. So why don’t we go ahead with the first question, and if you are not able to get up and go to one of the microphones, just flag me down, and I’ll bring you one. Go ahead. - All right. Thank you, Tom. Is this … - Nope. - Thank you, Tom. So a couple questions that are related to help ourselves in our homes. - Yeah. - What is the current thinking on water? How much water – how many gallons per person per day, and how many days? - Okay, so it’s one gallon of water per person per day. And I’d suggest at least seven days’ worth of water per person. So one – you know, if you have a house and a backyard, you can – I think you can buy at Costco, you know, those 50-gallon drums. And I would just buy one of those and fill it up and leave it in my backyard. - Okay, thank you. And the other one is, when you threw up the map of the fires and the Bay Area … - Yeah. - … what sort of fires are you thinking of? Are these, like, gas leaks and – ignited that start the fires? And how could we mitigate that? - I’m actually not exactly sure of the source of the ignitions. I would think they’re primarily gas-fed, but they could be – you know, people might have candles that are lit, and they fall over and start a fire. But, you know, just making sure that your hot water heater is well-strapped is one major way. Most of our other appliances, like our stoves, they’re not so inclined to fall over and tip over. But hot water heaters tend to be tall and skinny. So they are very likely to tip over if they’re not well-strapped. - Okay, thank you. - Oh, let me – one more answer is that you can install gas shut-off valves at your house that, when they detect motion, they automatically turn off the gas. - Yeah, actually I have one of those in my house already. So I think if that were to go off in an earthquake, I might be inclined to let PG&E turn that one on. - Yes. [laughter] Good idea. - Yeah. Related to the hot water heater. I added an automatic gas shut-off valve in my house back in spring 2011, by the way. But the hot water heater – got a 40-gallon tank out in the garage, [inaudible] strapped. Could I use that for a source of drinking water over a number of days? - Yeah, I’ve heard various things, like it’s okay, it’s not okay. I think if I were dying of thirst, I would drink it. - Yeah. Okay. - I definitely could use it for, you know, flushing toilets and washing dishes. - Yeah. - That sort of thing. - Okay. [Silence] - And actually, one related – another tip is, if you do have an earthquake, before that power goes out and the pumps go off that stop pumping water, fill up your tub with water. - Yeah. Yeah. And if you have a good seal on your bathtub, that’ll work fine. [laughter] I’m not sure I do. - I can add a little to that question about drinking from your water heater. A lot of it depends on the age and condition of your water heater. And my husband and I just replaced ours about a week or two ago. If it’s really old, it’ll have a lot of rust and sediment and awful brown stuff inside of it, and it will not look very appealing. But it starts out very clean and drinkable. I mean, it is drinking water that comes into the top of your tank and then just gets heated up. So, again, it really depends on the age and condition of your water heater. If it’s on its last leg, and it’s full of rusty sediment … [laughs] - If you happen to be on a freeway, what’s the rule? - Okay, so in earthquakes, people who are driving in cars, they think they’ve got a flat tire. You know, the car starts moving erratically. They go, oh, I’ve got a flat. They pull over. And they look around, and then they start noticing things are waving. Oh, it’s an earthquake. So if you – if you – if you figure out that it’s an earthquake and not a flat tire, or in any case, you pull over very slowly and controlled off to the side of the road and stop, preferably not under an overpass. [laughter] Or a high-tension electrical system or something. And you just wait on the side of the road. That’s the advice. - Yeah. I just have a real quick statement. I drain my hot water heater every 90 days. - Every nine days? - Every 90. Every 90. - Every 90 days. Okay. - [inaudible background comments] - That’s another tip. - Any other questions? Come on. You guys are quiet. So – oop, here’s someone who has a question. Here. I’ll bring it to you. - I’ve been attending these wonderful lectures at least since 1980, maybe earlier, I forget. There was a great lecture like this approximately a week before the Loma Prieta. [laughter] - Okay. - Leslie could figure that out. - I want to figure out when that was. - So did you do anything to help yourself? - Yes. And very interesting. And then, the reason I mention that is your map here and your display shows that there were quite a number of small earthquakes prior to the Loma Prieta. And I know, I was here, and yes, we had them pretty regularly. And then, bango, we had the Loma Prieta. So relative to the Hayward, is there a similar confluence of early small shakes on the Hayward? - [inaudible] - Yeah. Is there a similar confluence of small quakes on the Hayward prior to a big event? Will there be, maybe? - You remember that – one of the first figures I showed, the timeline that ran from the Gold Rush? - Yes. - To present day. And there were a lot of earthquakes between 1850 and 1906. Well, that’s – we just have that one example. So we don’t know if, before the next big earthquake, we’re going to see a lot of earthquakes or not. We just don’t know. - There was before the Loma Prieta. - Well, there were a few. There were – there were a couple down in Morgan Hill area. Yeah. But they weren’t anything like they were before the 1906 earthquake. - Hi. I work at El Camino Hospital, and as you know, the hospitals have been rebuilt through the state. Can you give us an update on that and what the law is and how we’re doing on meeting those goals? Well, from a seismologist viewpoint, the update and the upgrade, the retrofitting and replacement of hospitals in the Bay Area has been a tremendous success story. Right after the 1994 Northridge earthquake, the state passed a requirement that, by 2013, that hospitals be life-safe. That they don’t collapse. They don’t kill people. And by 2030, they have to not only be life-safe, they have to be fully operational after an earthquake – immediately after the earthquake. So to date, that has resulted in 31 hospitals being torn down and replaced with brand-new hospitals at a cost of about$16 billion. And El Camino Hospital is one of those hospitals. And other – so there are 50 other hospitals in the Bay Area that have been retrofit to make sure that they don’t collapse during earthquakes. And some are being retrofit so that they are capable of being used as a hospital right after the earthquake. So it’s been – if you – if you drive around the Bay Area and you look carefully, you’ll notice there are a lot of new hospitals in the Bay Area. And that’s the reason why. So I think, in terms of hospitals, we’re in much better shape than we were back in 1995.

- Next question is here.

- Yeah. I have water purification tablets to extend beyond your seven days. It’s hard to store – for a family of four, you’re looking at 28 gallons of water.

- Yeah, you are.

- And that’s a lot of water to have.

- Yeah.

- Secondly, where do you think we’ll get firefighting water from?

- That’s a good question. That’s what happened in 1906. I didn’t show it here, but there’s a great photograph taken right during the fire of 1906, and you can see there was liquefaction of the ground. You can see water spewing out of the ground of – the water pipe is broken. Water is rushing out of the ground. You can see a line of power – power poles that have tilted over. So not only the water pipes broke, but the gas pipes broke too, right?

- Yeah.

- So then you – electric lines fell down, sparked off the gas. And in the photograph, you can see the smoke rising from the background, and you see refugees coming towards you. And, you know, that will happen again if we’re not able to fight these small fires ourselves. If – and if we lose water. Now, after 1906, the good news is that the City of San Francisco installed fairly large cisterns – underground cisterns of water throughout the city. The bad news, that they were put in in 1906. [laughter]

- Oh, geez.

- So they’re a hundred years old now.

- Yeah.

- So they’re currently being retrofit and strengthened so that they’ll survive the next earthquake. And I don’t know if that’s a strategy that other communities are using.

- Oh, actually, I have a comment, you know, about pre-shocks. Very vividly remember we had one nine weeks before the Loma Prieta. It was about quarter after 1:00 in the morning, August 10. I just hit the sack, and it just –

[inaudible] the city, about 5.1 on the Richter scale about nine weeks before August 10 was that when – it’s a foreshock. We knew that in retrospect it was a foreshock.

- Okay. Yeah, no, there were – there were a couple of earthquakes before the Loma Prieta earthquake, and I remember them very vividly because I was the only one standing in the doorway. [laughter] Being kind of a newcomer to California. All the Californians, uh, pffh. [laughter] That’s just a small earthquake. Well, then the Loma Prieta earthquake happened, and there were a lot of other people standing in the doorway. So I remember that very clearly.

- So why don’t we stand in doorways anymore?

- Well, we don’t stand in doorways anymore because modern construction, there’s really no difference in the structural integrity of the buildings. We used to do that for unreinforced masonry-type buildings. But now you’re much better off getting underneath something so you don’t get hit.

- Tom, I have a couple questions on these handheld telephones we all depend on.

- Yeah.

- Is the danger that the cell towers are going to fall? Are they not being built to earthquake standards that they can sustain, you know, some level of shaking?

- Yeah.

- How fast do – can they restore the network? I mean, you’re not a telephone guy, obviously. But, I mean, I assume that they are all aware of how dependent we are

[chuckles] on these things.

- Yeah. Well …

- And so how long – how long do we expect they’re going to be not available, and how widespread would that disruption to the network be?

- I don’t really have a good answer to that, but I don’t think there is a standard for the installation of cell phone towers for seismic safety. So, you know, I don’t think there is a standard, so they’re being done every which way. And so some may fail, and a lot of them do have back-up generators, but I don’t think they have very much fuel. So I don’t know if they’re going to last one day or two days before they run out of fuel.

- And …

- Is that part of the ShakeOut drill, do you know? Sorry. Is that part of the ShakeOut drill to have these towers go down and sort of force us to deal with that? I assume not. That would cause so much disruption.

- Well, the ShakeOut is kind of an umbrella. And you can do your own exercise – whatever you want to test underneath that umbrella. They don’t tell you what to do.

- Except for drop, cover, and hold on.

- Yeah.

- And the other thing about cell phones is we can make it better with our own behavior. A lot of times the cell towers are still standing and still functioning, but the system is so overloaded because everybody goes, oh my god, did you – you know, OMG, did you feel that earthquake? So stay off of your cell phone unless it’s a true emergency. Also, if you’ve got a lot of family in the Bay Area, don’t be calling each other. Ahead of time, establish maybe, you know, Aunt Mary, who lives outside of the Bay Area, and she’ll be a – kind of a central hub. Everybody call into her and say, I’m okay. And she can communicate that to others. There’s a lot of ways, by our own behavior, that we can help the cell network not get overloaded and fall apart. Sorry, go ahead. Next question.

- I had the opportunity on the evening after Loma Prieta to go down into Gilroy and the back way into Watsonville and look around. And one of the things that struck me about it was, the problem isn’t water heaters falling over. It’s the refrigerator or the washing machine and the big appliances that go dancing around the room. And, I mean, I saw kitchens that were really broken up by flying refrigerators. So somehow or another, this has not gotten into any of the literature, but doing tie-downs – you got to tie down your refrigerator.

- Yeah.

- Otherwise, it’s going to go bouncing off the walls.

- Yeah. That’s a good idea.

- I was at a disaster council meeting in San Francisco several years ago when PG&E was making a presentation on the loss of electricity and that. And the telecom companies all said, you mean, we’re not priority to get re-established? Because their batteries lasted six to eight hours.

- Yeah.

- And the second thing, on the San Francisco auxiliary water supply system, it’s confined largely to the northeast part of the city. So a swath of the Outer Richmond, Sunset, all the way over to the bay shore does not have that system.

- That’s true. Back in 1906, there was – there wasn’t much built out there. But I think this retrofit program that they have, they might be building cisterns out there. I don’t know for sure.

- Yeah, Tom, are we allowed to tell stories on a colleague? [laughter]

- Yeah. I guess if you keep it clean.

- Sure, okay. [laughter] He’s not here to defend himself. The date before – the night before the Napa earthquake, Dave Schwartz’s wife was having a birthday party in Napa. And, in the course of dinner, the question was put to Dave, who was the authority on Bay Area earthquake probabilities and other things, what are the chances of an earthquake? [laughter] And he went into his usual mantra of, you know, three chances in four over the next – in the next 30 years. And it’s not much worse – you know, da da da, blah blah. Well, about five hours later, they had this earthquake. And he gets a phone call from one of these guests that says, I just want you to know I’ve got zero confidence in you. [laughter]

- Well, they didn’t ask the question, what’s the likelihood in the next five hours? [laughter] You’ve got to right that – you’ve got to stroke the right question.

- Hi. This is something I haven’t really seen addressed, but if you have the opportunity to get outside and away from everything, is that safer than just staying in place and covering and holding on?

- No. It’s not. First of all, when these really big earthquakes hit, you’re not going to be able to walk or run. And if you do, you’re likely to fall over and get hurt trying to do that. And if you do make it outside the door, you’re just in time for the big, heavy thing falling off your building to land on you, which is exactly what happened in that Alameda County Courthouse. There was a fatality from somebody trying to run out of the courthouse, and wham, they got hit by falling debris. So you stay in your place, and you do your best job of drop, cover, and hold. Okay? Because buildings in California, for the most part, will keep us alive.

- May I address that last question?

- Sure.

- I’m a registered civil engineer for the State of California. Working for the State of California, so if there is an earthquake, and you’re in a city, and it’s a big one, go inside the nearest building you can. Because every high-rise there is, all the windows are going to be popping.

- Yeah.

- And if ever saw the original Omen … [laughter] … there’s a little thing of a plate glass window coming down and sort of doing something to a priest. That will be going on all over the cities.

- Yeah.

- Now, I’ve worked with the City of San Francisco Fire Department. They estimate that, after another major earthquake of 6.8 level, there will be 10 feet of glass in downtown San Francisco on the streets. And they have a lot of concerns on how to get through that with their engines and trucks. So run inside a building. Most buildings nowadays are designed to – Millennium Tower notwithstanding [laughter] – most earthquakes – or, buildings nowadays are designed to withstand the greatest credible earthquake we have, which is an 8.7.

- Yeah.

- So …

- Yeah. That’s not the first time I’ve heard that, and so if you’re downtown in the Financial District, yeah, you feel an earthquake, you go inside a building.

- Yeah, I think in the …

- And try to get some cover inside the building.

- I think in the Loma Prieta that – well, was it eight or nine fatalities up in the city, where people who were hit by some of the façade or skin coming down – they had left the building. And there was one incident that took out about eight or nine people.

- I think one piece of advice is not to – one piece of advice is, don’t memorize what you’re supposed to do. If you’re inside, go there, if you’re outside, go here, or if you’re – whatever. Don’t do that. Instead, think. Pause for two seconds and think. What can hurt me? Most injuries are caused by things falling on you, whether it’s plate glass out of a building, a brick unreinforced masonry façade to a building, a chandelier inside. So what can fall on you? As Tom said, if you’re in bed, stay in bed. If you can get under a table to protect that chandelier from falling on you, do that. If you’re out in the streets, run into a building. If you’re already out in a big playing field, like playing soccer or baseball, as long as you’re not under one of those big light things, just stay out there. So the idea is not to just memorize every single situation that’s possible. But think. What could fall on me and hurt me? So that’s …

- One of the other things I noticed in Loma Prieta was the warning of shaking was preceded by a few seconds by the amount of dust and dirt coming out of the ceiling tiles. So, before you got floor motion, that P wave was enough to get all the junk in the ceiling to begin to fall. And then, five or six seconds later, you began feeling ground motion. But, if your ceiling starts dumping dust all over you, it actually is a little bit ahead of the ground motion.

- Yeah. So your point was that you actually experienced the first wave that was not real damaging.

- Right. Right. But it …

- Before the stronger damaging wave came in.

- Right, but the P wave isn’t …

- And so you got your own earthquake early warning that way.

- Yeah. The P wave is enough to get the …

- Which will be faster than the one we deliver to you. [laughter]

- … the rain of dust out of the – out of the ceiling tiles and such.

- I just want to say I’m really feeling deprived because I missed out on the Loma Prieta earthquake completely because we were driving home through a forest fire because this is California. [laughter] But when we got home, we didn’t know there had been a major earthquake because a stuffed animal got knocked off an upper shelf. Period. That was it. Because I live in the foothills east of Milpitas, a block away from the Hayward Fault. So the question is [laughter], when the Hayward Fault goes, are the people who felt the Loma Prieta quake so strongly going to experience a similar sense of calm? [laughs] Because it’s not going to affect them very much?

- Yeah. It’s the situation kind of reversed. Yeah. But, as I said, people on the peninsula will definitely feel the earthquake, and there will be some amount of damage. Not going to be as strong as along the Hayward Fault.

- Are there any good studies – scientific studies on animal behavior as a precursor to earthquakes as a warning to us?

- Well, let me ask you a question. So your cat did something strange before the earthquake yesterday. Well, how many times does your cat do something strange [laughter] and there is no earthquake? So we have these anecdotal reports, but there’s really been no scientific study that’s been able to show that animals have any predictive capability.

- Okay.

- I mean, the – you know, they’re laying on the ground, and probably more sensitive to ground motions. So they might feel the first arrival – the first wave before we do. But that’s about it.

- How much – let me see. How much of the shock wave will go underneath the bay toward San Francisco to Redwood City? If there’s a large quake?

- Well, yeah, the waves will travel through the ground, and they don’t even see the bay. It just doesn’t – the earthquakes will start – the earthquake will start 4 or 5 miles deep. So it’ll travel up and underneath the bay, and it won’t even know there’s a bay. So the bay – and the bay is only – you know, it’s, like, 8 feet deep. It’s like a lake. So it’s not going to have any impact on the earthquake wave.

- All right. One more question, and we’ll call it an end.

- Yeah. Actually, not a question. I think I heard a while back, not too long ago, that there’s some theory that a earthquake on one fault can trigger a quake on another fault. Is that true?

- Yes, it is true.

- Okay. Yeah.

- But – so we have seen earthquakes trigger other earthquakes around the world. In 1868, we didn’t see that triggering the San Andreas Fault across the bay. In 1906, we didn’t see that triggering the Hayward Fault. And, in fact, in the Loma Prieta earthquake, we saw that it actually reduced the stress on the Hayward Fault.

- Oh.

- And we saw fewer earthquakes after the Loma Prieta earthquake on the Hayward Fault than we did before the earthquake. And we saw – this rate of steady, constant creep, that actually decreased on the Hayward Fault after the Loma Prieta earthquake. So it works both ways. It can add more stress to a fault and produce earthquakes, or it can take away stress and reduce the earthquake hazard on the other fault.

- What’s the possibility of us getting hit by a 9-point quake in the Bay Area?

- Pretty close to zero.

- That’s a …

- I won’t say zero. About every 100,000 years, maybe.

- It’s kind of beyond the realm, this century.

- Yes.

- Okay.

- Well, I mean, we could have one tomorrow. [laughter] I mean, one over 100,000 years.

- Maybe we spoke too soon if that happens. [laughter]

- It’s not zero. I didn’t say zero. I said close to zero. [laughter]

- Thank you.

- Good.

- All right. Thank you very much, Tom.

[Applause]

Thank you for all of your questions.

[Applause]

Don’t remember – or, don’t forget to ShakeOut on October 18th, and please come back next month on the 25th to learn about debris flows. All different ways you can get killed around here, but … [laughter] We’re prepared.

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