A Taiwanese scientist has developed an earthquake alarm that could give people a crucial 15-second warning in case of a tremor, one of his team said Wednesday.

The gadget, about one-third of the size of a laptop, can be linked to computers and also be used to halt lifts in buildings when quakes strike.

The system relies on seismic waves, which move vertically as well as horizontally. The device detects and analyses these vertical waves, which travel faster and are less violent than horizontal waves.

"The device has been put to a series of tests," said an assistant to Wu Yih-min, a professor at National Taiwan University's Department of Geosciences.

The few seconds extra would give people precious time to seek shelter in the case of potentially fatal quakes, according to Wu's team.

Wu expects the device to retail for around 300 US dollars once the prototype has completed a series of tests in the coming two years.

Taiwan, which lies near the junction of two tectonic plates, is regularly shaken by earthquakes. A 7.6-magnitude quake killed about 2,400 people in September 1999.