Scientists install new sensors to monitor Mauna Loa activity

By Christie Wilson
Neighbor Island Editor

Two electronic tiltmeters have been installed on Mauna Loa's southwest rift zone to help scientists track the movement of magma beneath the surface of the world's largest volcano.

Mauna Loa, which last erupted in 1984, began reawakening in May 2002, with a gradual swelling that has continued for more than a year. Although the inflation suggests the volcano could be headed for another eruption, the type of earthquake activity that preceded past eruptions remains low, said Peter Cervelli, a research geophysicist with the Hawaiian Volcano Observatory.

The tiltmeters were installed last week.

The volcano's recent stirrings have sped up a long-term plan to improve monitoring, Cervelli said.

"Mauna Loa hasn't gotten the attention it deserves over the years," he said. "Kilauea has been erupting for 20 years and it's been distracting."

For example, 12 tiltmeters are in place at Kilauea, double the number for Mauna Loa, which rises 13,680 feet above sea level and covers half the island of Hawai'i. "It should be the opposite because Kilauea is a far less threatening volcano," Cervelli said.

The six tiltmeters on the mountain include the two newly installed ones in the southwest rift zone, one at the summit, one at the National Oceanic and Atmospheric Administration weather observatory, one at Hokukano Ranch in Kona, and another along the Mauna Loa Strip Road.

The observatory plans to install additional instruments next year to monitor the northeast rift zone. Lava from an eruption there could threaten Hilo.

Working on Mauna Loa presents a host of logistical challenges, Cervelli said, including the fact there are few roads. "It's wilderness out here. It's remote, it's high and you don't have electricity," he said. "You have to bring your own generator."

The two new electronic tiltmeters were installed at elevations of 8,500 feet and 12,500 feet by Maurice Sako and Kevan Kamibayashi, physical science technicians at the Hawaiian Volcano Observatory. The two spent three cold days and nights on the mountain drilling into solid rock to make holes 4 inches wide and 10 feet to 13 feet deep.

The specialized drill they used cuts a circular ring around a central core that must then be extracted. A generator was used to run the drill, and a powerful vacuum that sucked up the material left in the hole after the core was removed.

By the end of the job, more than 3,500 pounds of gear and water, which was required to lubricate and cool the drill, were ferried to and from the tiltmeter sites by helicopter.

The high elevation limited the aircraft payload to 300 pounds, Cervelli said, and many helicopter shuttles were required. "At $700 an hour, it adds up. We spent more on the helicopter flights than on one of the tilt instruments," Cervelli said.

The $5,000 devices can detect ground tilt imperceptible to humans that is caused by the intrusion or pressurization of magma. The tiltmeters are extremely sensitive instruments capable of discerning tilts of about 0.1 microradians (1 microradian equals 0.00006 degrees). Cervelli said potentially alarming volcanic tilts can be as small as half a microradian.

The measurements can tell scientists in what the direction the magma is traveling, how close it is to the surface and possibly help predict where a fissure may occur.

Also monitoring Mauna Loa are six GPS receivers and a dozen seismometers. All three types of instruments radio data to the Hawaiian Volcano Observatory so scientists can watch the volcano in real time.

"Tiltmeters are especially good at detecting fast, rapidly evolving magma movements. GPS receivers, on the other hand, excel at tracking slow, long-term processes that occur on the scale of years," according to the Volcano Watch report issued yesterday by the observatory. "Both of these instruments can detect magma movement that is not breaking rock and that, therefore, is not causing earthquakes. But magma almost always has to break rock to reach the surface and erupt. This is when the earthquake-detecting seismometers become especially useful."

For daily volcano updates and nearly real-time earthquake information, visit the observatory Web site at hvo.wr.usgs.gov.

Reach Christie Wilson at cwilson@honoluluadvertiser.com or (808) 244-4880.