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Feature - Sixty seconds to save a city

Feature - Sixty seconds to save a city


Circles indicate warning times for the earthquake that hit Taiwan on 4 March 2010, using a new approach to detection that gives up to 40 seconds more early warning. Taipei is the northernmost city indicated on the map, on the 50 second circle. Image courtesy Nai-Chi Hsiao, Central Weather Bureau, Taiwan.

At the International Symposium on Grid Computing (ISGC 2010) in Taipei last week, a special two-day EUAsiaGrid Disaster Mitigation Workshop devoted a day to the latest technological progress in monitoring and simulating earthquakes and tsunamis. In a situation where every second counts, grid computing could one day help authorities assess the potential impact of an earthquake quickly enough to avoid the worst consequences.

The day before ISGC 2010 began, Taiwan was hit by a magnitude 6.4 earthquake in the south part of the island, making headlines worldwide.

But earthquakes are a daily reality for Taiwan's inhabitants, and indeed for populations all along the enormous "Ring of Fire," a portion of which cuts right through Southeast Asia. Technically known to geologists as the circum-Pacific seismic belt, the ring has 452 volcanoes, and is where over 80% of all earthquakes occur.

Although there were no fatalities in the March 4 earthquake, considerable damage was done. And as Nai-Chi Hsiao of Taiwan's Central Weather Bureau explained in a talk about Taiwan's early warning system, it takes just sixty seconds for an earthquake to travel from the south to the heavily populated north of the island, leaving little time for authorities to make decisions about such things as shutting down nuclear reactors, stopping high-speed trains, and otherwise taking steps to avoid the worst.

To provide an early warning, about 100 earthquake sensor stations dot the island. But accumulating data from all of them and then assessing the information takes time. So, a more nimble method was introduced a few years ago, based on gathering data in so-called "virtual sub-nets" - groups of sensors spanning regions of 50km or so. If these sensors confirm a major quake, they can sound the alarm right away, without having to verify what the rest of the entire network has detected.

For quakes which originate in the south and east of the island - the most active areas - this deceptively simple strategy triples the warning time for metropolitan Taipei, from 20 seconds to nearly 60 seconds.

3-D perspective view of earthquake depth for major earthquakes in and around Taiwan. Courtesy Wen-Tzong Liang, Institute of Earth Sciences Academia Sinica.

Where does grid technology fit in?

Taiwan is rocked by quakes - both large and small - all the time.

So it's simply not viable to shut down power plants and stop trains every time a tremor is detected. What is needed is a quick prediction of the impact that a particular quake may have on key infrastructures across the island.

But the amount of shaking that an earthquake can produce a hundred or so kilometers from its point of origin can vary strongly, depending upon, for example, the depth at which it occurs.

There is certainly no time to do a full simulation once the first hint of an earthquake is detected. However, according to Li Zhao of the Institute of Earth Sciences at Academia Sinica, it is possible to pull out a pre-processed simulation from a database and make a quick decision based on what it predicts. This requires processing and storing the results of simulations for a huge number of possible quake epicenters, a task well-suited to grids.

Furthermore, if sensor data and grid resources could be shared across the region, other countries, hundreds or thousands of kilometers from a quake's epicenter, could also benefit.

After all, natural disasters do not respect national boundaries.

-Francois Grey, for EUAsia Grid

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