Wireless Sensors Monitor Volcanic Activities

By Roland Piquepaille

Several months ago, I wrote here about how wireless sensors were used to monitor glacier behavior. Now, for the first time, a wireless array of sensors has been deployed to monitor the eruptions of an active volcano in central Ecuador, the Tungurahua. An international team of computer scientists and seismologists installed a small wireless network of five nodes to record 54 hours of continuous infrasound data transmitted over a 9 km wireless link back to a base station at the volcano observatory. As the results are very encouraging, and because these wireless sensors are very cheap, this installation will soon be duplicated to detect eruptions of other active volcanoes. The team expects to deploy larger infrasonic arrays consisting of up to 50 nodes in the next six months either on Tungurahua or elsewhere in the world. Read more...

Here is the introduction of this news release from Harvard University.

Computer scientists at Harvard University have teamed up with seismologists at the University of New Hampshire and University of North Carolina to fit an Ecuadorian peak with a wireless array to monitor volcanic activity. The sensors should help researchers, officials, and local residents understand and plan for eruptions of Tungarahua, one of Ecuador's most active volcanoes in recent years.

The researchers installed the wireless network on Tungarahua and captured 54 hours of data during a recent trip to the 5,016-meter mountain. The wireless system could eventually replace the wired sensors now used on Tungarahua and many other volcanoes.

Here is how the system works.

Matthew D. Welsh, assistant professor of computer science in the Division of Engineering and Applied Sciences at Harvard, and his colleagues fitted Tungarahua with a network of five tiny, low-power wireless sensor nodes equipped with a special microphone to monitor infrasonic (low-frequency acoustic) signals emitted during eruptions. Each runs on two AA batteries, is sealed in a waterproof container the size of a soap dish, and transmits data automatically to an observation post more than 5 miles away down the mountain.

Wireless sensor networks represent a new kind of computing platform. They consist of small, low-power, wireless devices merging sensors with a small amount of computing power and storage. Sensor networks have been explored for applications such as habitat monitoring, medical care, and seismic analysis of structures; this effort is believed to be the first such application of wireless sensor networks to volcanic monitoring.

	Here is the architecture of the system of wireless sensors monitoring Tungurahua (Credit: Matt Welsh group at Harvard University).
	And here is a picture of the infrasonic microphone mote (Credit: Matt Welsh group at Harvard University).

The two images above come from a report named "Monitoring Volcanic Activity with a Wireless Sensor Network" (PDF format, 30 pages, 3.22 MB).

This other report, "Monitoring Tungurahua," contains many more details and pictures. For example, it gives more information about the wireless sensors, or "motes."

A typical sensor "mote" is powered by 2 AA batteries and includes an 8-bit microcontroller, 4 KB of memory, a low-power radio with a range of approximately 100 meters and a bitrate of about 38 Kbit/sec. The low cost, size, and energy requirements of sensor networks makes them very attractive for volcanic monitoring.

Five Mica2 sensor network devices performing three different tasks composed our volcano monitoring network: three data-collection motes fitted with custom-built infrasonic sensors, one receiver mote forwarding data over a long-range serial point-to-point link, and one time synchronization mote interfaced to a GPS unit providing a common time base for the data collection elements.

And what are the future plans? Here is Welsh's answer.

Over the next six months we plan to design a much larger infrasonic array, on the order of 20 to 50 nodes, for deployment on Tungurahua or elsewhere. The volcanologists who partnered with us on this initial deployment are very excited about the capabilities such a large, spatially-separated array would provide. Using more nodes increases the aperture of the microphone 'antenna', facilitating much more advanced analysis of collected data.

Sources: Harvard University news release, via EurekAlert!, September 23, 2004; and various other websites