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StreetLight Data analyzed 100 communities and compiled a list of areas in the country with limited evacuation routes. The data is free and can aid neighborhoods in planning for evacuation or developing infrastructure.
Evacuation planning is one of the most difficult tasks in emergency management, and on evacuation routes, bottlenecks in recent disasters have resulted in loss of life.
That was the impetus for StreetLight Data to conduct a national (plus Canada) analysis of small towns and their evacuation risks in situations like floods, fire, dam breaks, hurricanes, tornadoes and other emergencies.
The results are available for free to government agencies looking to develop disaster evacuation plans or develop improved infrastructure.
The analysis looked at 30,000 towns in the United States with populations under 40,000 and with the results of the analysis, StreetLight Data compiled a list of the most "evacuation-challenged communities."
The states with the most evacuation-challenged communities are:
1. Florida (20 communities)
2. California (14)
3. Arizona (8)
4. Texas (6)
5. Washington (6)
"We were developing some cool visualizations about traffic flow, and our CTO saw there was one area where traffic flowed from just one area and thought, 'That would be tough if everyone had to leave at the same time,'" said StreetLight Data CEO Laura Schewel. "That was the genesis for the study."
"So we developed some tools to show these 'car sheds' of driving," she said. "We decided to analyze small towns because those are the ones where you get the most horror stories and they have the most bottlenecks and the least amount of resources to deal with it."
Schewel's team developed an index that looked at a few factors to assess evacuation constraint risk. The first factor is how many total routes out of town there are. Another is, on a typical day, what percentage of people take a certain route, even if there are multiple routes. The last factor was total population.
Even though there may be more than one route out of town, many people would choose a certain route out of ease of use or habit. That's an important factor to know for an emergency manager who is thinking about ordering evacuation. It might prompt an earlier evacuation or calls to use a different route.
Or there may be four routes out of town but three are terrible roads, so 80 percent of the population will seek to travel on that own road. "What we hope is that this data escalates a conversation with authorities to talk about evacuation planning in a more pointed way," Schewel said.
Schewel said the company can also do more rigorous studies for more in-depth transportation planning purposes as well. For example, "How does this part of town differ from another part of town or how is it different in winter and summer?"
The company uses proprietary data processing engine that collects millions of location points from smartphones and GPS navigation devices in autos, and transforms them into contextualized, aggregated travel patterns. It then develops a "main exit load" percentage from the percentage of the population's daily trips that take a main exit.
"We also process Internet of Things data from sensors from things like weigh stations for trucks," Schewel said. "And we turn it into an accurate and aggregated description of what's happening on any road, neighborhood bike lane, offramp, or block in the United States or Canada."
Here are the top 20 U.S. communities with the most constrained evacuation routes:
1. Camano, Wash.
2. Hilton Head Island, S.C.
3. Mercer Island, Wash.
4. Hutchinson Island, Fla.
5. Sanibel, Fla.
6. Fort Myers Beach, Fla.
7. Carpendale, W. Va.
8. Pahrump, Nev.
9. Nahant, Mass.
10. Skidaway Island, Ga.
11. North Bay Village, Fla.
12. South Beach, Fla.
13. Coto de Caza, Calif.
14. Golden Beach, Md.
15. Six Shooter Canyon, Ariz.
16. Immokalee, Fla.
17. Hoyt Lakes, Minn.
18. Bell Canyon, Calif.
19. Long Beach, N.Y.
20. Siesta Key, Fla.
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By Shinji Toda, Ph.D., IRIDeS, Tohoku University, and Ross Stein, Ph.D., Temblor, Inc.
The Magnitude 7.1 earthquake abruptly halted aftershocks on the M 6.4 cross fault. It also produced a far-flung aftershock sequence that touched the San Andreas, but refused to cross the Garlock Fault.
Citation: Shinji Toda, and Ross Stein (2019), Ridgecrest earthquake shut down cross-fault aftershocks, Temblor, http://doi.org/10.32858/temblor.043
Shutdown
A remarkable illustration of how stress controls seismicity was handed to us by the Ridgecrest earthquake sequence. Two perpendicular faults ruptured in the M 6.4 earthquake on July 4 (left panel below), both lighting up in aftershocks. But when the M 7.1 struck 34 hours later, seismicity along the cross fault abruptly stopped (middle panel below). Why?
Maps of seismicity and calculated Coulomb stress change for the Ridgecrest sequence. (The calculation is for 'optimally-oriented' strike-slip faults with friction of 0.4 at 10 km depth.)
The answer seems to be that the M 7.1 rupture cast a 'stress shadow' over the cross fault, inhibiting failure by several bars, and so shutting aftershocks off. In our calculation of the stress imparted by the M 7.1 (right panel above), the cross fault is 'shadowed,' (blue zones) while the stress increased to the northwest (red zones), to southeast extending across the Garlock Fault. The isolated side lobes also experienced aftershocks to the M 7.1 event. The seismicity shutdown along the cross fault is dramatic when viewed as a time series for M≥1 shocks (below), with the seismicity rate dropping by a factor of 10.
In this time series of seismicity for M≥1 earthquakes, each shock is a green 'lollipop,' and the cumulative number of shocks is shown by the blue line. Following the M 7.1, aftershocks on the cross fault didn't get smaller, they just occurred less frequently. A few bars are not a lot of stress. In the photo below, Ross puts a half a bar of Coulomb stress across the base of his palms by pushing as hard as he can.
Ross Stein demoing Coulomb stress. (Photo by Dr. Bob Sabol, United Airlines passenger) Stress Shadow
Seismic shaking can promote seismicity but not inhibit it, so the shutdown illustrates that small decreases in Coulomb stress can inhibit earthquakes, a phenomenon first discovered in the 1987 Superstition Hills earthquake by Ken Hudnut, Leonardo Seeber and Javier Pacheco (Hudnut et al., 1989), which also shut down seismicity on a cross fault. It was seen again in the 1992 M 7.3 Landers shock (Toda et al., 2012), which shadowed part of the aftershock zone of the M 6.1 Joshua Tree quake that had struck 66 days before. The Joshua Tree shutdown began several days after the Landers shock, but at Ridgecrest, it was immediate. Stress shadows were named by Ruth Harris and Robert Simpson of the USGS, which they argued explained the paucity of large shocks in the century or so after the great 1857 in southern California, and after the great 1906 quake in northern California (Harris and Simpson, 1996). Stress shadows were also hypothesized to explain the shutdown of the southern Hayward Fault after the 1989 Loma Prieta shock (Stein, 1999).
Remote Shocks
If one steps back from the cross fault, one sees what appear to be aftershocks as much as 150 km (90 mi) from the M 7.1 epicenter in three of the four stress trigger (red and yellow) lobes in the panel at left below, and these appear to correspond to the stress trigger lobes. But are these aftershocks, or just shocks that would have occurred in those remote locations anyway?
Calculated Coulomb stress change (along optimally-oriented strike slip faults at 10 km depth with friction of 0.4) is shown at left. Seismicity rate change after the M 7.1 quake is shown at right, in which warm colors indicate rate increases (aftershocks), and turquoise colors indicate rate decreases. Rate decreases are difficult to detect in the weeks after the mainshock. We can answer that question by plotting the change in the seismicity rate, comparing the first 11 days after the M 7.1 to the preceding year (above right). Here, the warm colors are places where the seismicity rate increased after the M 7.1, light blue areas are where it decreased. Now, all four stress trigger lobes appear to correspond to seismicity rate increases (e.g., aftershocks), and they extend all the way to the San Andreas Fault at Tejon Pass and Cajon Pass.
San Andreas in play?
What do the subtle, or perhaps apparent, seismicity increases at the two big bends on the San Andreas Fault mean for future great quakes? We do not know. We can say only that the effects, while promoting failure, are very small, about the same as the twice-daily tidal stresses.
The Garlock Wall
But if the shutdown and remote shocks can be explained by stress transfer, another feature of the aftershocks is mysterious. If you glance again at the Coulomb stress lobes, you can see that the stress trigger zone extends well to the south of the Garlock Fault, but the M 7.1 aftershocks do not. That is even clearer in the map below: The Garlock is a wall.
Neither the preceding decade of quakes (in blue) nor the Ridgecrest aftershocks (in red) cross the Garlock Fault, but aftershocks extend outward in most other directions. Why would a fault be a barrier to aftershocks? We can think of two explanations, but we can't prove either. The first is that Coulomb stress changes amplify the background seismicity rate (this follows from the theory of rate/state friction developed by Jim Dieterich at the USGS; Dieterich, 1994). If the background rate is high (those are where there are many blue shocks above), then the seismicity will be very responsive to the stress changes. That seems to be what happened at the Coso Volcanic Field, which was active before the M 7.1, was stressed by the M 7.1, and produced abundant aftershocks. But if its near-zero, as it appears to be south of the Garlock, the stress changes have almost no effect.
Even if that explanation were correct, that would not explain why the northern Mojave Desert, south of the Garlock Fault, was so quiet in the first place? Perhaps because it is composed of different rocks than the material to the north. The Garlock has slipped a total of ~100 km (60 mi), juxtaposing different chunks of crust. To the north lies mostly granitic rocks, and to the south lies mostly volcanic rocks (see the map below). Somehow, rock type might modulate seismicity.
Geologic map of the Ridgecrest area (Jennings et al., 1962), labeled by type of bedrock. The yellow veneer of sediments blanket some of the bedrock. Aftershocks of the Ridgecrest sequence are red; the preceding decade of quakes are blue.
So, what did we learn?
The Ridgecrest sequence demonstrates how Coulomb stress controls seismicity. Ridgecrest has also produced an exceptionally distributed aftershock sequence that just kisses the San Andreas, but refuses to cross the Garlock Fault.
Ridgecrest fault rupture, with a main rupture and distributed faulting over 20 m (70 ft). Photo by USGS. To see a series of fault rupture images, see Stewart et al. (2019).
References
James Dieterich (1994), A constitutive law for rate of earthquake production and its application to earthquake clustering, J. Geophys. Res., 99, 2601-2618, doi.org/10.1029/93JB02581.
Ruth A. Harris and Robert W. Simpson (1996), In the shadow of 1857—the effect of the great Ft. Tejon earthquake on subsequent earthquakes in southern California. Geophys. Res. Lett. 23, 229–232, doi.org/10.1029/96GL00015
Kenneth W. Hudnut, Leonardo Seeber, and Javier Pacheco (1989), Cross‐fault triggering in the November 1987 Superstition Hills Earthquake Sequence, southern California, Geophys. Res. Letts., 16, 199-202, doi.org/10.1029/GL016i002p00199.
Charles W. Jennings, John L. Burnett, and Bernie W. Troxel (1962), Geologic Map of California, Trona Sheet, Scale 1:250,000, California Geological Survey, Sacramento.
Ross S. Stein (1999), The role of stress transfer in earthquake occurrence, Nature, 402, 605–609, doi.org/10.1038/45144.
Jonathan P. Stewart, Editor (2019), Preliminary Report on Engineering and Geological Effects of the July 2019 Ridgecrest Earthquake Sequence, Report GEER-064, issued July 19, 2019, 69 p., http://geerassociation.org/administrator/components/com_geer_reports/geerfiles/GEER_Ridgecrest_report_ver1.pdf
Shinji Toda, Ross S. Stein, Gregory C. Beroza and David Marsan (2012), Aftershocks halted by static stress shadows, Nature Geoscience, 5, 410–413, doi.org/10.1038/ngeo1465
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Date | Time | News and Notes |
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| 08/28/2019 | 1810 | Federal
Cow, Vegetation Fire, Tulare County, Update
Kelty, Vegetation Fire, Mono County, Update
Broder, Vegetation Fire, Tulare County, Update
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On February 14 (2011) the sun erupted with the largest solar flare seen in four years—big enough to interfere with radio communications and GPS signals for airplanes on long-distance flights.
As solar storms go, the Valentine's Day flare was actually modest. But the burst of activity is only the start of the upcoming solar maximum, due to peak in the next couple of years.
"The sun has an activity cycle, much like hurricane season," Tom Bogdan, director of the Space Weather Prediction Center in Boulder, Colorado, said earlier this month at a meeting of the American Association for the Advancement of Science in Washington, D.C.
"It's been hibernating for four or five years, not doing much of anything." Now the sun is waking up, and even though the upcoming solar maximum may see a record low in the overall amount of activity, the individual events could be very powerful.
In fact, the biggest solar storm on record happened in 1859, during a solar maximum about the same size as the one we're entering, according to NASA.
That storm has been dubbed the Carrington Event, after British astronomer Richard Carrington, who witnessed the megaflare and was the first to realize the link between activity on the sun and geomagnetic disturbances on Earth.
During the Carrington Event, northern lights were reported as far south as Cuba and Honolulu, while southern lights were seen as far north as Santiago, Chile. (See pictures of auroras generated by the Valentine's Day solar flare.)
The flares were so powerful that "people in the northeastern U.S. could read newspaper print just from the light of the aurora," Daniel Baker, of the University of Colorado's Laboratory for Atmospheric and Space Physics, said at a geophysics meeting last December.
In addition, the geomagnetic disturbances were strong enough that U.S. telegraph operators reported sparks leaping from their equipment—some bad enough to set fires, said Ed Cliver, a space physicist at the U.S. Air Force Research Laboratory in Bedford, Massachusetts.
In 1859, such reports were mostly curiosities. But if something similar happened today, the world's high-tech infrastructure could grind to a halt.
"What's at stake," the Space Weather Prediction Center's Bogdan said, "are the advanced technologies that underlie virtually every aspect of our lives."
Solar Flare Would Rupture Earth's "Cyber Cocoon"
To begin with, the University of Colorado's Baker said, electrical disturbances as strong as those that took down telegraph machines—"the Internet of the era"—would be far more disruptive. (See "The Sun—Living With a Stormy Star" in National Geographic magazine.)
Solar storms aimed at Earth come in three stages, not all of which occur in any given storm.
First, high-energy sunlight, mostly x-rays and ultraviolet light, ionizes Earth's upper atmosphere, interfering with radio communications. Next comes a radiation storm, potentially dangerous to unprotected astronauts.
Finally comes a coronal mass ejection, or CME, a slower moving cloud of charged particles that can take several days to reach Earth's atmosphere. When a CME hits, the solar particles can interact with Earth's magnetic field to produce powerful electromagnetic fluctuations. (Related: "Magnetic-Shield Cracks Found; Big Solar Storms Expected.")
"We live in a cyber cocoon enveloping the Earth," Baker said. "Imagine what the consequences might be."
Of particular concern are disruptions to global positioning systems (GPS), which have become ubiquitous in cell phones, airplanes, and automobiles, Baker said. A $13 billion business in 2003, the GPS industry is predicted to grow to nearly $1 trillion by 2017.
In addition, Baker said, satellite communications—also essential to many daily activities—would be at risk from solar storms.
"Every time you purchase a gallon of gas with your credit card, that's a satellite transaction," he said.
But the big fear is what might happen to the electrical grid, since power surges caused by solar particles could blow out giant transformers. Such transformers can take a long time to replace, especially if hundreds are destroyed at once, said Baker, who is a co-author of a National Research Council report on solar-storm risks.
The U.S. Air Force Research Laboratory's Cliver agrees: "They don't have a lot of these on the shelf," he said.
The eastern half of the U.S. is particularly vulnerable, because the power infrastructure is highly interconnected, so failures could easily cascade like chains of dominoes.
"Imagine large cities without power for a week, a month, or a year," Baker said. "The losses could be $1 to $2 trillion, and the effects could be felt for years."
Even if the latest solar maximum doesn't bring a Carrington-level event, smaller storms have been known to affect power and communications.
The "Halloween storms" of 2003, for instance, interfered with satellite communications, produced a brief power outage in Sweden, and lighted up the skies with ghostly auroras as far south as Florida and Texas.
Buffing Up Space-Weather Predictions
One solution is to rebuild the aging power grid to be less vulnerable to solar disruptions.
Another is better forecasting. Scientists using the new Solar Dynamics Observatory spacecraft are hoping to get a better understanding of how the sun behaves as it moves deeper into its next maximum and begins generating bigger storms. (See some of SDO's first sun pictures.)
These studies may help scientists predict when and where solar flares might appear and whether a given storm is pointed at Earth.
"Improved predictions will provide more accurate forecasts, so [officials] can take mitigating actions," said Rodney Viereck, a physicist at the Space Weather Prediction Center.
Even now, the center's Bogdan said, the most damaging emissions from big storms travel slowly enough to be detected by sun-watching satellites well before the particles strike Earth. "That gives us [about] 20 hours to determine what actions we need to take," Viereck said.
In a pinch, power companies could protect valuable transformers by taking them offline before the storm strikes. That would produce local blackouts, but they wouldn't last for long.
"The good news is that these storms tend to pass after a couple of hours," Bogdan added.
Meanwhile, scientists are scrambling to learn everything they can about the sun in an effort to produce even longer-range forecasts.
According to Vierick, space-weather predictions have some catching up to do: "We're back where weather forecasters were 50 years ago."
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1986 Aeroméxico 498 Crash Anniversary
When:
Saturday, 31 August 2019
Where:
Cerritos - Los Angeles County
Organizer: Kim Patrick Noyes
Description:
The 1986 Cerritos midair collision was a plane crash that occurred in southern California over the Los Angeles suburb of Cerritos on Sunday, August 31, 1986. Aeroméxico Flight 498, a McDonnell Douglas DC-9, was clipped in the tail section by N4891F, a Piper PA-28-181 Archer owned by the Kramer family, while descending into Los Angeles International Airport, killing all 67 on both aircraft and an additional fifteen on the ground. Eight on the ground also sustained minor injuries from the midday crash.
Blame was allocated equally between the Federal Aviation Administration and the pilot of the Piper. No fault was found with the DC-9 or the actions of its crew.
On Sunday, August 31, 1986 at about 11:46 am PDT, Flight 498 began its descent into Los Angeles with 58 passengers and six crew members on board. At 11:52 am, the Piper's engine collided with the left horizontal stabilizer of the DC-9, shearing off the top of the Piper's cockpit and decapitating Kramer and both of his passengers. The heavily damaged Piper fell onto an empty playground at Cerritos Elementary School.
The DC-9, with all of its horizontal stabilizer and most of its vertical stabilizer torn off, inverted and immediately entered a dive. It slammed into a residential neighborhood at Holmes Avenue and Reva Circle in Cerritos, crashing into the backyard of a house at 13426 Ashworth Place, exploding on impact. The explosion scattered the DC-9's wreckage across Holmes Avenue and onto Carmenita Road, destroying four other houses and damaging seven more. All 64 passengers and crew on board the DC-9 were killed, and fifteen people on the ground; a fire added to the damage.
Source: https://en.wikipedia.org/wiki/1986_Cerritos_mid-air_collision
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This is video shot August 29 from the Single Engine Air Tanker (SEAT) piloted by Jim Watson on the R-1 Ranch Fire 13 miles northeast of Susanville, California. He was working out of the Air Tanker Base at Chester, California. You may notice that the aircraft is following another SEAT that makes a drop ahead of him.
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