Wednesday, April 11, 2018
FEMA has published additional Recovery Advisories related to the rebuilding efforts in Puerto Rico that are applicable to many other communities and regions. The hurricane/flood-proofing ideas are extremely useful tools for designers, contractors and other involved in constructing or reconstructing housing in damage-prone areas. The latest information can be found here.
Thursday, March 22, 2018
As part of a late winter storm system (named “Toby”) that moved through the Southeast earlier this week, at least 13 tornadoes touched down in Alabama. Buildings like the one in the photo in one community, Jacksonville AL, were seriously damaged and the repair estimates are in the tens, perhaps hundreds of millions of dollars. In fact, at Jacksonville State University, where the devastation was severe, administrators have opted to close the campus for a number of weeks to clean up and rebuild.
|Damage left in the wake of an EF-3 tornado in Jacksonville, AL, March 2018|
But a tweet sent out by the National Weather Service in Birmingham, AL, happily reported that there were miraculously no fatalities. The tweet continued with, “Sweeter words have never been spoken after a significant severe/tornado event. Thank You, Central AL, for staying weather aware & heeding warnings on Monday!”
Therein lies the real lesson for all of us, at least for this particular type of natural hazard: Heeding the warnings and taking shelter saves lives. Obviously, safety is never guaranteed, but if those in harm’s way listen and get out of the way, their chances for survival are far greater.
Friday, February 2, 2018
An article in PhysicsWorld.com cites the work of Sébastien Guenneau (and others) of the Fresnel Institute in Marseille, France and says that “buildings in the future could be isolated from earthquakes by being placed behind rows of trees.” Apparently, according to the article:
|(Photo from linked article)|
“…certain seismic waves, known as Love waves, could be diverted away from the Earth’s surface as they pass through a forest containing trees of a certain height. The forest acts like a metamaterial – an artificial structure usually used to steer electromagnetic radiation around objects.
“Best known for their use as invisibility cloaks, metamaterials are made from large arrays of tiny resonators that manipulate light and other electromagnetic waves in unnatural ways. In recent years, however, the mathematics underlying metamaterials have also been applied to other kinds of radiation, including seismic waves. The idea here is to use arrays of suitably-sized objects either below or above ground – holes or posts of some kind – to divert seismic waves around vulnerable buildings.”
Guenneau says that, in practical application, trees would have to be roughly 10-15 meters tall to resonate with horizontal Love waves. Protecting a building from the vertical “Rayleigh” waves, however, would require trees some 5 times this tall (that would take decades to mature) making it less practical. That said, scientists say that by using trees to prevent horizontal shaking and conventional techniques to “guard against vertical motion, forests could halve the work of civil engineers.”
Much more research is needed to better understand the behavior of these waves and the potential real world applications. The science, however, is fascinating. And the potential benefits are worth continued investigation.
The bottom line is that mature trees are good. And worth protecting for a variety of reasons.
This occurred in September, but I just received notice of it via an e-mail blast from FEMA. The National Earthquake Hazards Reduction Program (NEHRP) issued a new set of Recommended Simplified Provisions for Seismic Design Category (SDC) B Buildings. For a look at Category B, see Map here.
Not all portions of the country are affected, but the new document should be a helpful reference for all in A and B zones looking to improve resilience in the face of such events. (I happen to live in a Category B area.) And of course those in Categories C through E will have much more rigorous requirements. Here’s the link to the new document.
The introduction to the report includes this statement:
"For Seismic Design Category (SDC) B, which designates a low seismic hazard region, structural engineers still need to complete a full seismic design process to meet the building code requirements. Seismic design is necessary because earthquakes are a hazard with long return periods and large uncertainties, and the sudden occurrence of earthquakes in SDC B regions, such as the 2011 Mineral, Virginia earthquake, can cause significant damage or collapse if buildings are not properly designed for seismic resistance. The recommended simplified seismic design provisions described in this FEMA NEHRP document aim to assist structural designers in meeting building code requirements for ordinary SDC B buildings without wading through the full, complex seismic design process in ASCE/SEI 7.”
Tuesday, January 30, 2018
Earlier this month, the State of Hawaii issued a warning to its citizens that a missile attack was imminent, telling them to seek shelter immediately. Twenty seconds after sirens sounded and cell phone tweeted the warning, it was determined to be a false alarm, but the corrective notice didn’t make it out to most until 38 minutes later. Panic ensued and now the State (and the Federal Government) are working to determine how something like this could happen and prevent such a false alarm in the future. (See New York Times article on the issue here, also the source of the photo.)
Public warnings are a critical part of protecting people from the potential impacts of any disaster, whether natural or man-made. And Hawaii is no stranger to disasters. Or attacks. And so it’s important that the warning system be effective, timely and most of all, accurate. Unfortunately, the timely and effective warning last week fell short in the accuracy department. That’s being changed, they say.
The launch of a missile begins a period of preparation wherein the public can seek shelter. While it may only be a few minutes long, time does provide some options for those in danger. A more common event in Hawaii (and indeed many coastal regions of the world) is a tsunami warning. Again, an earthquake triggers a warning period and allows the public to prepare. Fortunately, not all warnings result in a tsunami inundating the coast; but people will respond. When it comes to something like a tsunami (or a missile launch, apparently) no amount of “crying wolf” will dampen public response. And that’s good.
But what about natural events that don’t have a warning period associated with it. Take, for example, the frequent earthquakes that plague many parts of the world. Will we ever be able to accurately predict them and warn the populations that might be affected by them? Does an earthquake (or series of quakes in a short period of time) mean “the big one” is coming?
“It’s true, too, that earthquakes in one place can trigger more far away, over thousands of miles. It may even be true that the worldwide coincidence of major quakes is more than coincidence, that there are global patterns that bring disaster into sync. But the bigger truth is that scientists still don’t know enough about the fundamental physics of earthquakes to predict with precision and certainty when a seismic event will happen. Earthquakes aren’t entirely random, but for the purpose of day-to-day threat assessment, they may as well be.” (Source here.)
Plans for public safety and for mitigating the impact of diasters of all types must include the realization that early warning may not be possible for some events, and that simply warning and sheltering vulnerable populations isn’t enough. Governments, schools, businesses and homeowners must do all possible to locate and build cities and settlements in such a way that they are safe places to be, even when a disaster is immediately impacting them.
When there is no warning, moving to a safer place is not an option. But making all places safer (or choosing not to build them in the first place) is an option we can choose.
Monday, December 4, 2017
An excellent article this weekend in the New York Times offers dramatic photo evidence of Hurricane Harvey’s impact on an upscale Houston neighborhood, along with the story of a resident family that were the victims of a common (and apparently legal) practice by developers who truck in soil to raise building lots just above the designated flood area and, thereby, eliminate their obligation to notify buyers of the potential for flood damage.
These “wet” and “dry” photos (from the article) of the block are telling. The occupant, a Mrs. Martinez, recalls in the article that “the home builder had assured her that ‘flooding was not even a possibility…’ They would never have bought here otherwise. Flood insurance, of course, was neither required nor needed.”
Mrs. Martinez recounts that, with Harvey’s “rains outside lashing and the water inside rising, the family and their terrified pet, a one-eyed goldendoodle named Coco, took refuge on the second floor. Later that day, rescue boats came and ferried them to safety.”
The lessons in the article are quite worth a read.
Wednesday, November 29, 2017
A recent article by the Washington (State) Geological Survey demonstrates the uses of Lidar (light detection and ranging) technology to map geological hazards. The article explains the process and illustrates its use with fascinating case studies involving hazards common to the Pacific Northwest: Landslides and Volcanoes. The article goes on to describe applications of the technology in locating fault lines, predicting tsunami inundation zones, and tracking the courses of rivers over time to predict flooding impact. The process can also yield incredible images of sub-surface geology.
The online, interactive article is well worth your time to read.
Clearly the benefits for applying the technology to hazard identification and mitigation are immeasurable. Hopefully, it will also become a useful tool in educating and convincing policy makers and the general public to address the hazards in a real way. Being able to target action and resources to more specific geographical locations will be a significant benefit to endangered communities.
|Lidar image of the glaciers on Mt. Rainier. (From the Article)|
The online, interactive article is well worth your time to read.
Tuesday, November 14, 2017
Last Sunday, there was a 7.3 earthquake reported in Iran, near the Iraqi border. Just 8 hours later, Costa Rica experienced a 6.5 quake. These were on the heels of 5 major earthquakes (>6.0) reported over the last week, plus dozens of moderate quakes (>4.0) that hit hotspots like the Pacific Rim. News reports called the Iranian quake the deadliest of the year, adding that “at least 452 people were killed and thousands injured… and was felt as far away as Turkey and Pakistan.”
Scientists are divided about an increase in the frequency of earthquakes and statistics show ebbs and spikes are cyclical over time. Other natural events—particularly weather events—do seem to be increasing, if not in frequency, at least in strength.
Interestingly, there those scientists who think the two may be related, at least on some level. They’ve identified statistical (indirect) relationships between the two. Others have demonstrated that a phenomenon known as “slow earthquakes” can be triggered by major atmospheric disturbances like hurricanes and typhoons. (Wikipedia defines a slow earthquake as “a discontinuous, earthquake-like event that releases energy over a period of hours to months, rather than the seconds to minutes characteristic of a typical earthquake.") That sounds like an interesting topic for another time.
The message here is that, whether they are increasing or we’re simply experiencing an anecdotal spike in natural disasters, they will continue to come. Nobody is predicting a reduction in the future. Thus building resilience into our cities and adapting our communities to survive these events should remain a top priority.