New West Technology

From Colorado Seismologists, A Better Earthquake Alert?

By Brendon Bosworth, 3-24-11

	Buildings damaged by the February earthquake that hit Christchurch, New Zealand. A team of U.S. Geological Survey seismologists in Golden, Colorado, created a system to give more useful warnings to emergency responders after severe earthquakes like the ones that struck Japan and New Zealand earlier this year. Flickr photo by martinluff.

When an earthquake hits anywhere in the world, the seismologists at the National Earthquake Information Center in Golden, Colorado, are quick to know about it.

Operating 24/7, the Center, a core part of the U.S. Geological Survey’s Earthquake Hazards Program, is plugged into real-time feeds from a network of thousands of earthquake-monitoring instruments around the globe.

For many years, the Center has played an important role in sending out information about the magnitude and exact location of earthquakes within minutes of them happening. Some 230,000 people around the world currently receive earthquake notifications via text message or email, said Geological Survey seismologist David Wald in a telephone interview.

While Richter scale magnitude measurements quantify the size of an earthquake, they don’t indicate the extent and intensity of ground shaking or give an idea of how people and buildings nearby will be affected, said Wald.

That’s why Wald and his team created the Prompt Assessment of Global Earthquakes for Response, or PAGER, system, which went live in November 2010.

For global earthquakes of magnitude 5.5 and above the system creates one-page alert reports, released within 30 minutes of a quake, that provide estimates of the number of people and names of cities exposed to ground shaking and the likely range of fatalities and economic losses that will result.

The reports are sent to emergency responders; aid agencies, such as the Red Cross; the media; and government officials and organizations. Financial institutions like the World Bank and groups that respond with financial backing for countries affected by disasters also receive the reports, Wald – who is the principle investigator for the PAGER project – explained.

The reports provide an alert level, which can range from green (zero to minimal risk) to red (losses predicted to be over 1,000 deaths or $1 billion dollars). Separate alerts for estimated fatalities and economic losses are provided, with the higher guiding the overall alert level.

One of the key benefits of the PAGER system, according to Wald, is that it hones in on earthquakes that happen close to populated areas and are likely to cause damage and loss of life.

There are about 150 earthquakes of magnitude 6.0 around the globe each year, but only a handful of them are truly devastating, he explained.

“Not only are we alerting people to the most significant earthquakes, we’re filtering out the noise – the earthquakes that nobody really needs to hear about because they didn’t have an impact, or were out to sea or had very low population exposure,” he said.

“What we’re doing here is saying yes, this is important – it’s a yellow and orange or red alert – so depending on your role for responding to earthquakes you’ll know exactly whether to go into action or not.”

A limitation of the PAGER system is that it only predicts deaths and economic losses based on damage to buildings from shaking. It does not incorporate the secondary impacts of earthquakes, such as landslides, fires, and tsunamis.

The PAGER report for the behemoth magnitude 9.0 earthquake that rocked Japan on March 11 issued a red alert for economic losses and an orange alert for shaking-related fatalities. The report estimated a likely death toll of between 100 and 1,000 people and financial losses of between $1 billion and $10 billion.

The losses in Japan turned out to be more devastating than the alert suggested, though the resulting tsunami, not the massive earthquake, caused much of the destruction. As of March 23, the official death toll exceeds 9,400, and over 14,700 people are listed as missing, according to the New York Times. The Japanese government estimates the total cost of the disaster to be as high as $309 billion over the following three years.

In future, the USGS seismologists hope to be able to address landslides and fires in the PAGER alerts, as well as potentially tsunamis, said Wald.

However, building predictions for tsunami-related losses into the system would be particularly challenging, since tsunamis travel across the ocean which can result in tsunami-related destruction occurring up to half a day after the initial earthquake, he explained.

How it Works

The PAGER system is automated, with computer-generated reports typically released within 20 minutes of a quake, Wald said.

In the case of earthquakes that generate orange and red alerts, seismologists review the alert levels before they are finalized and sent out. This doesn’t take much longer than half an hour to an hour after a major disaster, Wald said.

As new information comes in the reports are reviewed and updated, he added.

At its base, the system builds upon technology called Shakemap, which Wald and his colleagues developed 10 years ago. As the name suggests, a shakemap indicates the intensity of ground shaking produced by an earthquake.

“Year in and year out we have 20,000 to 30,000 fatalities from shaking alone, around the globe from earthquakes, so it’s an extremely important problem to be working on,” said Wald.

The shaking intensity is combined with population information from Landscan, an Oak Ridge National Laboratory database of global population distribution, to estimate how many people will be affected, Wald explained.

The system melds this data with information about the spread and quality of buildings in vulnerable areas, with an estimation of how many people are in each building, and the financial costs of predicted building damage, Wald said.

Information regarding the types of buildings in the region and how many people will be in each building at a particular time of day is the toughest to source, Wald said.

If the seismologists can’t access current building data, they make use of historical data, looking as far back as 40 years to see how many buildings collapsed and what fatalities arose from earthquakes at the same level of shaking intensity, Wald explained.

For regions without reliable historical data, the seismologists look at comparable countries where deadly earthquakes have occurred and make approximations. They group countries together based on similar climate and building construction practices, along with socioeconomic indicators, Wald said.

“It turns out that’s a little easier than it sounds, because the best structures in the world in, say, New Zealand, Japan and California are really good – they have a very low collapse rates,” he said. “And the worst structures in the world, say in Iran and Pakistan and China, are extremely vulnerable. So, everything in the world is somewhere in between those two end-members and those ranges are extremely wide.”

“Construction practices are extremely important and having earthquake-resistant buildings really makes a huge difference,” he said.

Accuracy and Estimates

The PAGER report for the magnitude 6.3 earthquake that hit New Zealand on February 21 this year estimated a 79 percent likelihood for fatalities between 1 and 10, and a 19 percent likelihood of fatalities between 10 and 100. But in total, New Zealand police estimate that 182 people died, the New Zealand Herald reports.

Wald said there is a degree of uncertainty built into the PAGER process, since measurements of shaking distribution, population numbers, and how likely buildings are to collapse are not exact. The system addresses these uncertainties by providing a range of estimated losses and the reports are updated as new information becomes available, he said.

“There’s always a trade-off between doing things quickly and getting accurate results. And if we wait for accurate results it wouldn’t be particularly useful,” said Wald.

Wald emphasized that the first few reports are the most important because they mobilize responders before “ground truth” information, such as media reports and feedback from responders, becomes available.

“As we go forward we want to reduce these uncertainties. We want to continue to speed up the system, but we’re really fundamentally limited by what we know at the time and what we know about the inventory of the population around the globe,” he said.

Brendon Bosworth is based in Boulder, Colorado.

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