Earthquake early warning technology, still ahead?

The death of tens of thousands of people after the devastating earthquake in Sichuan (China) once again raged about the need for optimal technology to warn such disasters early. In addition to Japan, Mexico and Taiwan implementing seismic early warning systems, most of the remaining countries and territories in the world, including the United States, are still in the research or testing phase. .

Very soon, only 20 seconds

The most advanced earthquake early warning system of Japan is only alerted for 20 seconds.(Photo: Japan Meteorological Agency)

The United States is about to install a system of 400 seismic wave gauges and 125 satellite navigation devices (GPS) to collect earthquake data across the country, from which seismic risk predictions in each region with frames specific time, from decades or even centuries.(Photo: EarthScope)

Earthquake alarm systems are currently only a few seconds ahead, but that time is enough for people to walk on the road in time. The world's most advanced earthquake early warning system was deployed in Japan last October, issuing an alarm through mass media, including television and the Internet before the earthquake struck. about 20 seconds.

Unlike the old system that only warned and slowed down the speed of high-speed trains, the new warning system allowed people to take defensive measures themselves, such as running off elevators, bridges and roads, trains and hiding places. Under the table or away from the walls.

However, when the warning order is issued, the danger is close. Seismic waves move at an average speed of 6 km / sec, spreading to a radius of hundreds of kilometers in just 1 minute. Such a short period of time is not enough to evacuate people from buildings.

Therefore, if China is equipped with a series of state-of-the-art alert systems like Japan - even on a larger scale - the fate of tens of thousands of people is trapped in schools, offices and factories. . high-rise in Sichuan is no different. In order to preserve their lives, a warning system for evacuation orders must be issued many minutes or hours before seismic occurrence.

Currently, the US Geological Survey is cooperating with the University of California to develop an early warning system similar to that of Japan. The project will be completed next year but the initial test will give positive results. Using data from the seismic tracking system existing in California state, the ElarmS system when tested with a 5-magnitude earthquake model can determine seismicity about 15 seconds before it hits. The exact level of alert depends on the distance from the point of placement of the ElarmS with the epicenter.

To improve alert efficiency (more accurate and sooner), existing systems need to be equipped with more sensors to spread across a large geographic area . As the number of sensors increases, the determination of epicenter as well as the magnitude of the earthquake is more accurate, and the warning message is given as early.

Some experts suggest taking advantage of sensors in laptops and turning them into primary seismic wave identification devices (or P waves, which occur at initial earthquakes, have low damage). Although the sensors in the laptop are not very sensitive, according to Haroo Kanamori, the world's leading seismic expert, mobilizing large numbers at the same time can improve seismic monitoring.

The future can be predicted many days, even months

To minimize the level of earthquake damage, Japanese scientists will study this new warning system this year, predicting a few days or months of seismic risk. The new system allows to explore changes within the deep underground layer, as well as in a large area, from which a short-term earthquake warning can be issued.

Researchers plan to install 400 seismic gauges on the seabed, while testing cracks in the rock layers in the ground. Using a calculator to calculate collected data, the system will indicate whether earthquakes occur concurrently, as well as the time period that can give a warning about changes in stratigraphic conditions. as well as the possibility of earthquakes occurring simultaneously. The system will periodically update earthquake information similar to updating weather forecast information.

It is expected that the system will be completed in 15-20 years with the cost in the first 5 years estimated at 5 billion yen (nearly 50 million USD).

QUOC CHAU
(According to MIT TechReview, PopMec, Yomiuri Shimbun, Can Tho Online)