A question occasionally posed to those in the aviation industry is “how are aircraft affected by earthquakes?” The automatic response given to this question is often something along the lines of “airplanes fly above them.” And so, the question lives on – unanswered – in the mind of the curious inquirer.
Everyone is aware of the effects earthquakes can have on buildings, roads, and ground vehicles. Unfortunately, we have seen these effects illustrated in the recent devastation in Japan.
It may seem unlikely at first that an aircraft that spends so much time so far removed from the surface of the earth could be majorly affected by a specifically ground-based natural disaster. Yet, with more aircraft taking off and landing at all times than ever before, let alone all the aircraft and crews sitting on the ground at any one time, it’s not entirely unreasonable or trivial to wonder: Are they affected?
Consider that in the U.S. alone, air traffic controllers handle an average of over 120 take-offs and landings every second. The recent earthquake in Japan lasted for over 360 seconds. If a six minute earthquake were to hit the U.S., that adds up to about 44,000 planes and helicopters landing and taking off from runways while the ground is still shaking – so, the question of how earthquakes can affect aircraft and the ground facilities they rely upon is at least worth considering.
Soon after the March 10 earthquake and tsunami that affected Japan, newspapers reported that some international airlines were diverting their Tokyo flights to areas further from the quake’s epicenter. This was partially for fear of aftershocks possibly endangering aircraft and crews. We’ll talk more about the effects on aircraft on the ground in a minute – first, what about aircraft that are landing right when the quake starts?
An earthquake of intense magnitude could theoretically confuse some aircraft systems like the ILS (instrument landing system). This wouldn’t be too much of a problem, unless coupled with other problems (weather, low visibility) that would make a visual or different instrument approach hazardous. Air traffic control should be able to notify approaching pilots of an earthquake that lasts more than a few seconds, providing enough warning to initiate a missed approach procedure in most cases.
But what if the earthquake is severe enough that ATC is evacuated? It does happen.
Doug Leja, an American Airlines pilot, was about to land at Narita Airport outside Tokyo two weeks ago when he received a message from the air traffic controllers that the control tower had been evacuated and the airport was closed. Meanwhile, he was still flying a 777.
He was also low on fuel.
He and around 25 other planes on their way to Narita tried to divert to the nearest open airport, Haneda, but it was full. He tried Yokota, but it was also fuel. Luckily, he had enough fuel to make it to an open runway in Sapporo where he landed safely.
Modern airports are built to withstand all but the most severe earthquakes. Some terminal buildings are marvels of modern engineering, sitting atop special supports that allow them to move gently as the ground thrashes in multiple directions. This, coupled with the amount of flat, open ground, makes some areas of an airport a relatively safe place to wait out an earthquake. Still, airports are not completely immune to taking critical damage from a quake. Hangars and support structures are more susceptible to taking damage, and it is possible for these damages to occur in a matter of seconds.
In 1964, a 9.0 magnitude earthquake in Anchorage, Alaska (pictured below) caused a 60-foot, 7-story control tower made of reinforced concrete to collapse, killing the 1 air traffic controller inside.
A lower-magnitude 2002 earthquake in Alaska caused major damage to Northway Airport (ORT), the principal port of entry for light aircraft enterting Alaska from the rest of the U.S. and Canada. The single 5,100 foot runway was completely destroyed – criss-crossed with extensive cracks.
After the 6.9 magnitude Loma Prieta earthquake of 1989, San Francisco International Airport (SFO) had to divert all inbound traffic and halt operations until the next day. The control tower sustained broken windows and some un-anchored, non-essential equipment breaking, but was still otherwise operational. However, some airport support structures were moved from their original positions due to an effect called liquefaction.
Liquefaction occurs when wet soils and sands underground temporarily behave like liquid during the violent shaking of an earthquake – and it can be very dangerous to runways built above these kind of beds.
November 2002 earthquake destroyed Alaskan runway (Source/Picture from AOPA Online)
Liquefaction in the Loma Prieta quake caused more immediate damage at Oakland International Airport, despite OAK being even further from the epicenter than SFO. Nearly a third of the 10,000 foot main runway became riddled with numerous deep cracks up to a foot wide – the ground directly next to the runway suffered from similar cracks up to 3 feet wide. The adjacent taxiway was damaged by the same process.
In addition, both the runway and taxiway were damaged by “sand volcanoes” that appeared on the runway and taxiway, several of which spread as wide as 40 feet. These short mound-like formations sometimes bubble out of the ground when water is forced upward by building pressure; bringing soil, rocks, and even underground debris with it (sand volcanoes from the 1989 Loma Prieta quake famously brought up debris from the 1906 San Francisco earthquake).
For an aircraft landing after or during an earthquake, a runway damaged from liquefaction could present a real hazard. If ATC detects the earthquake and radios the pilot in time, the plane could divert to another airport as a precaution – in most cases.
But, for an aircraft that doesn’t have enough fuel to get to the nearest unaffected airfield, a pilot could have to maneuver a dangerous and unpredictable landing strip.
Fortunately, aside from this kind of exceptional damage, an air ambulance crew landing as an earthquake occurs has little to fear in terms of a dangerous landing. As you might already expect, a plane’s landing gear is specially designed to handle the shocks from rough touchdowns and hard landings. Some pilots say they’ve landed on runways right in the middle of earthquakes up to 5.9 magnitude and were completely unaware anything had happened until they were informed by airport personnel afterward.
Indeed, ground tremors and lower-magnitude earthquakes could go completely undetected by the people on board many commuter jets due to the shock-absorption of most modern undercarriages. However, in a higher-magnitude quake, care should be taken to make sure the patient is comfortable (and well-secured) during the landing and does not panic.
Another concern for air medical crews following an earthquake is to check and make sure nothing in the aircraft has been affected during the shaking. This includes equipment, medications, detachable objects (like seats) and all other things that may have shifted or been damaged by collision during the earthquake.
In very strong earthquakes, mechanical inspections of the aircraft may be necessary, as the G-forces experienced may exceed the safe limits for an aircraft sitting on the ground. Runways, taxiways, tarmacs, and hangars should be structurally inspected to ensure safe operation.
The point of this Air Ambulance Weekly article is not to raise worry about a relatively rare hazard, but to explore an interesting area of earthquake/aviation safety that has not been extensively addressed. We combined and condensed information from the results of past earthquakes and made some simple recommendations, but urge you to do your own research, and add your own input (correct us) if you wish.
- 2005 FAA/ATC statistics (FAA Air Traffic Organization 2005 Annual Performance Report)
- AOPA Online: Quake destroys Alaska airport