Tag: megaquake

Home Earthquake Vulnerabilities: Hillside Home Recommendations

Home and building owners, as well as renters, in hillside neighborhoods need accurate information about their earthquake risk so they can make informed decisions.

Hillside homes can have high, even catastrophic, earthquake risk. The previous two posts discussed common geological and structural problems with hillside homes.

But if you live in or own a hillside home, what should you do? Move away? Just live with the risk, and hope “The Really Big One” doesn’t happen in your lifetime? Get the house seismically upgraded? Get more information?

Yes, those are the four options that come to my mind:

1. Move Away?

I’ll address this first, because many reading this are concerned about earthquake risk. Of those of you who own and/or live in a hillside home, I’m guessing a high percentage of you didn’t know how dangerous this type of home can be in an earthquake. It’s likely no one told you anything about earthquakes when you bought or moved into the house, in fact, it may not have even entered your mind at the time. But here you are, and now you are thinking of moving, perhaps.

Moving away makes sense if:

  • You are confident the house is dangerous, and
  • You’re confident that it would be too expensive for your budget to fix, and/or
  • You aren’t too attached to the home, or maybe you don’t even like it.

Moving out of a hillside home that you perceive to be dangerous makes more sense, in my opinion, than staying and living with the risk. But you may want to consider my last point (#4 below) before moving.

2. Keep the house and live with the risk?

I certainly don’t recommend this. But there are some situations that are less risky than others.

If you own multiple homes and are rarely occupying the house, risk (at least life-safety risk) is obviously lessened simply due to the fact that you aren’t around much. If you don’t have kids and travel often, that’s a similar situation.

If you have a family, especially with a spouse or kids staying home during the day, you genuinely could be putting their lives at risk by not addressing potential seismic vulnerabilities in the place where most of their time is spent.

If your house is looming over your neighbor’s house down the hill, they could be at risk also due to your home’s earthquake vulnerabilities. You may both have earthquake insurance policies (unlikely), but that can’t make up for loss of life. Just something else to think about before you decide to do nothing.

Interestingly, there may be an economic argument against doing nothing also. Suppose your hillside home is worth a million dollars. Let’s say the chance of a severe earthquake affecting this house in the next 50 years is 20 percent (this is in the ballpark of what seismologists have estimated). Suppose the odds of collapse of the home during the earthquake are 50 percent (arbitrary number), with severe damage likely even if it does not collapse. A retrofit costing in the tens of thousands of dollars, or even $100,000, isn’t necessarily unreasonable in this circumstance, for those with the available capital and desire to keep the home.

There are situations where a retrofit could be more costly, but this would be difficult to know without more information (which is why I like Option #4 below).

It’s also possible that the house has low risk of seismic damage. In that case, it may be reasonable to live with the risk. But how would you know this? You probably need a specific assessment to be sure.

A collapsed California house after the Northridge Earthquake. This will likely happen to some hillside homes in Oregon and Washington when we get our “Big One”. Please take a look at this picture and ponder if you are okay living with this risk before choosing to do so.

3. Have your home seismically upgraded?

Of course, I recommend a seismic upgrade for many hillside homes. I’m concerned about the risk of a Cascadia Megaquake, and what it will do to hillside neighborhoods. This is why I’m writing this and specializing in this type of work.

But the choice to upgrade the home has to work economically. Hillside home seismic upgrades can be expensive, and not only does the money need to be there to pay for the upgrade, but the benefit should be worth the cost to the homeowner. I recommend spending the time necessary up front so you have a good ballpark figure of the cost.

Don’t Mess Around With Cascadia

I strongly believe in conservatism with seismic upgrades. Our Cascadia Subduction Zone could produce a magnitude 9.0+ earthquake that could last 3 to 5 minutes. This earthquake will last much longer than earthquakes that have caused the collapse of hillside homes in California in recent decades. Homes that have poor seismic force resisting systems (such as stilts with wood bracing) could degrade with each cycle of ground shaking, and there could be hundreds of cycles in this type of earthquake.

My point is this: if you are going to do an upgrade, do something that will actually work. Don’t just pay someone a few hundred bucks to take a quick look at your house and give you a few cheap recommendations. Count the cost ahead of time and be willing to pay for the thorough upgrade that you really want, that will really do what it needs to do when the ground shakes longer than an average pop song.

Hillside home seismic upgrades are complex, and involve much more than just “attaching the home to the foundation”.

You will need a structural engineer who specializes in hillside building seismic upgrades. I’m trying to be that guy because there’s a need there, but if you find someone else who qualifies, that’s great! More engineers need to be doing this, in fact, we really need an “army” of specialty engineers and contractors retrofitting homes and buildings ahead of the earthquake who are passionate about this kind of life-saving work.

You will, in many cases, need a geotechnical engineer also. Geological risks can’t be ignored and can sometimes drive the cost of seismic rehabilitation through the roof. If landslide risk is high, mitigation may be expensive or even virtually impossible. Make sure you figure this out with a geotechnical investigation, and make sure their recommendations are followed in the seismic upgrade. Or, if landslide risk is apparently low, at least have a structural engineer consider slope stability in the seismic upgrade including a conservative design with a new foundation if needed.

A stepped foundation collector I designed for a hillside home built in 2001. The intent of this design is to prevent the stepped shear wall failure (described in the previous blog post) by directing seismic loads into the high part of the foundation. I communicated to the homeowner that this type of failure was unlikely for her house, but I couldn’t rule it out. She wanted to strengthen the house. I believe it was a reasonable decision that gave her house a “belt and suspenders”- i.e. some redundancy, to help her and her family sleep better at night.

Hillside Retrofit Economics

Some hillside homes are almost beyond hope of an adequate seismic retrofit due to high landslide risk or a combination of structural problems. It is possible that effective strengthening measures could cost in the hundreds of thousands of dollars if the owner wants to really mitigate their slope stability or significant structural weaknesses. There is little benefit to retrofitting a home structurally if the ground it sits on is unstable.

The earthquake risk of hillside homes varies significantly from house to house and from site to site, and the cost of a necessary seismic retrofit can vary from $0 (no retrofit necessary) to extremely expensive. The decision to upgrade, move away, or live with the risk is a personal decision based on life-safety concerns, risk tolerance, and personal economics.

Due to the variability of cost and the many factors affecting the seismic risk of hillside homes, there is a need for good, up-front information for hillside homeowners.

4. Get More Information.

I hope the information in these blog posts about hillside homes is helpful for making decisions. Since the information is not house-specific, however, many need to go a step further.

Consulting a structural and/or geotechnical engineer is appropriate, and I am happy to do this. My preferred approach is to use a developed seismic risk assessment methodology. I currently use FEMA P-50, P-58, and ASCE 41, depending on the situation. You can learn more about these assessments here.

I believe seismic risk assessments have great value, and are a good first step in the decision process. If you hire me for an assessment, you will get a structural engineer’s opinion (a qualitative assessment) as well as an analytical (quantitative) assessment. This first-pass information can be done quickly at a relatively low cost, to help develop the “big picture” of what a potential retrofit would look like and what the potential benefits are.

“FEMA P-50” is a good seismic methodology that applies to most hillside homes. It will grade the house (with a letter grade from A to D-) based on how well it will perform in our largest expected earthquake. When I assess a home this way, I develop retrofit concepts and then grade the house pre-retrofit and post-retrofit. Sometimes I will provide a “lean” retrofit option, in addition to a more thorough retrofit option, if that makes sense for the particular structure.

Even if your hillside home was engineered relatively recently, it doesn’t hurt to have it double-checked. Engineers make mistakes sometimes, and hillside home retrofits can be difficult to design correctly.

If you’ve read all three of my blog posts on hillside homes, you can hopefully tell that I’m trying to sound the alarm regarding earthquake risk with these types of homes. However, not all hillside homes are in danger.

My main point is that there are many variables to seismic risk with these unique structures. To make an informed decision about what to do, hillside homeowners need accurate information that takes all these variables into account. This information may lead you in many different directions depending on your specific house and personal situation.

For more information about seismic risk assessments and retrofitting, please see the Cascadia Risk Solutions website.

Rogue One, structural engineering, and earthquakes

Most structural engineers have experienced a glazed-over look in someone else’s eyes when describing what they do for a living, followed by a response like, “so, you’re an architect?”

There remains ignorance in the public about what structural engineering (and engineering in general) is for.  Other engineering disciplines may be even more confusing; I doubt most people could define the term, “geotechnical”.  Personally, I’m still not 100 percent sure what an industrial engineer does.

I think the fault of this ignorance lies primarily with engineers.  We have an incredibly cool profession and if people understood better what we do, we would probably make more money, quite frankly. Especially if we were passionate about taking our skills and orienting them toward serving the community, region, and world to make it a better place (which is the reason all professions should exist).

Structural engineering seems to be making more inroads into the public sphere in recent years.  It’s always amusing when Hollywood addresses your career. This happened in the latest Star Wars movie, Rogue One (slight spoiler alert if you haven’t seen it).  The movie specified a large building, which reminded me of a dark version of a Dubai hotel, as a site dedicated to structural engineering (among other things) for the Empire.  And there was also the scene of a group of engineers (in lab coats?) being assassinated for apparent faulty design of the Death Star.  Considering the fact that this Death Star weakness led to the downfall of the Empire in subsequent episodes, this was understandable using Imperial logic, I suppose.

The Structural Engineers Association of Oregon has this clear statement defining the profession of structural engineering (good job, whoever wrote it):

Structural Engineering is the practice of analyzing and designing buildings, bridges and other structures to resist forces induced by gravity, wind, and earthquakes and to safely transfer these forces to the ground.

See here for more: http://www.seao.org/resources/aboutstructengr/

Regarding engineering in general, there are a number of good definitions online, but here is my very simple one:

Engineers apply science and mathematics to the real world to solve real world problems.

Engineers and the engineering profession should act as a bridge between the theoretical realm of science/ mathematics and real life.

Consider the large problem of an impending Cascadia megaquake. The science indicating that these earthquakes have happened and that the subduction zone is locked and building up energy has been settled for about 20 years.

Emergency management at the state and federal level has been aware of the threat for a long time also.  The Oregon Resilience Plan, which was a state funded plan addressing the effects of a Cascadia megaquake and its consequences, was published in 2013.

Journalists helped disperse the information about this topic into the homes and hearts of Pacific Northwest residents (thank you Sandi Doughton and Kathryn Schulz, to name two).  For the last couple of years, there has been more mainstream awareness of this issue than ever.  And my experience has been that people are still baffled by the topic and wondering what to do about it.

Here is my exhortation to engineers, particularly those involved in the disciplines of infrastructure (civil, structural, and geotechnical at the forefront). The Cascadia earthquake threat is large enough to involve all of our individual efforts for years. Please consider what part you can play in increasing your personal, community, and regional resilience. We all know more than the average person about earthquakes and what they do to the ground and to structures. Don’t hide in your cubicle or office. Do what you can with your career to help and you will be saving lives when the earthquake happens.

In Portland, engineers know that there are about 1800 URM (brick) buildings which may partially or completely collapse in a large earthquake.  We know many older homes have weak cripple walls, dangerous unreinforced chimneys, and “soft story” weaknesses which will result in damage, injury, and in some cases, loss of life. We know there will likely be long term loss of power and drinking water. We know industrial areas are set to contaminate our rivers with millions of gallons of liquid fuel. Wow, that’s just the tip of the iceberg. Let’s get to work.

Engineers are a key to helping bridge our gap between what we now know (the science) and resilience. But not just engineers… every one of us can help and I would argue that we have a duty to make steps toward preparedness.

Science =>  =>  =>  => => (our gap)  =>  =>  =>  =>  => Resilience

Journalists

Engineers

Emergency Planners/ Responders

City and State Leaders

Heavy Industry

Everyone

You and me

Cascadia residents pay attention: the Ring of Fire is alive and active

A couple of large earthquakes struck the Ring of Fire in the last 2 weeks: a magnitude 7.8 in New Zealand on November 14th and a 6.9 (according to USGS) on November 21st off the coast of Japan.

I’m fascinated by earthquakes, particularly since I’ve made a decision to focus my career on earthquake resilience.  But even if you’re not as into them as I am, the awesome power of earthquakes was undeniable last week in New Zealand.  And the Japan earthquake is another reminder of the need for preparedness in the Pacific Northwest.

Landslides, open fissures, stranded cows, and the seafloor lifting up out of the ocean are the images that struck me the most.

This drone video of a ground fault rupture in New Zealand looks like Lord of the Rings style special effects. I can easily imagine an army of orcs falling into the ground as it opened up:

And here’s a good article from CNN about the seafloor being raised.  The coast has been permanently changed in a dramatic way (unless an earthquake reverses it):

http://www.cnn.com/2016/11/18/asia/nz-earthquake-pics/

Regarding Monday’s Japan earthquake, the Japan Weather Agency is calling it an aftershock from the 2011 magnitude 9.0 megaquake.  It caused a small tsunami and seems to have shaken people up a bit (bad pun intended) but caused little damage.

It’s been estimated that we have a 37% chance of experiencing an 8.0 or higher Cascadia Subduction Zone earthquake in the next 50 years.  This is a helpful statistic and I intend to bring it up often.  The main application for us in the Northwest is that we have a high risk of this event occurring if we intend to live in this region for long.  It makes sense to prepare for it, but once you start thinking of the implications, it quickly becomes overwhelming from the individual level up to the state agencies.  The bottom line is that an adjustment in lifestyle is needed for all of us living in this region.  More to come on this topic…

How will a Cascadia megaquake compare with these recent earthquakes?  The magnitude will be greater; between an 8.0 and 9.0 and possibly even higher.  Ground fault rupture as shown in the video above won’t likely be an issue, at least not a primary one, as the fault is off the coast between the continental and oceanic plates.  Vertical displacement will likely occur, as the coast is expected to drop on the order of 6 feet relative to sea level.  This, along with the accompanying tsunami, has drastic implications for the low lying coastal areas. Strong ground shaking over a huge region will damage older infrastructure like brick buildings and 100 year old homes not attached well to their foundations.  Landslides are to be expected throughout the region.  Soil will liquify in saturated sandy soils such as near rivers.  This has terrible implications for industrial areas like northwest Portland and just south of downtown Seattle near the Duwamish Waterway.

My personal mission is to help inspire as many individuals and families as possible to be resilient when this event occurs.  If you’ve started preparing or making lifestyle changes, I’m interested in hearing from you as I’m sure I’m not the first person to do so.  I also want to hear from those of you who want to do something but are not sure what to do.  What are the questions you have and what concerns you the most?

Making ourselves and our region more resilient is a marathon, not a sprint.  So, take a breath and put some thought into this topic.  Don’t lose sleep over it, take action instead!