Quakes might propel lava

A UH scientist believes temblors could set off volcanic eruptions, as Indonesian events hint

A University of Hawaii-Manoa geologist and a colleague in Italy say earthquakes might trigger volcanic activity, a discovery they hope could eventually help save lives.

Andrew Harris of UH and Maurizio Ripepe of the University of Firenze observed the connection while studying the Indonesian volcanoes Merapi and Semeru. They also were gathering data on Earth's hot spots with a global satellite monitoring instrument developed at the UH Institute of Geophysics and Planetology.

"Merapi began to erupt in April and May last year, causing tens of thousands of people to be evacuated," Harris said.

He was in Italy collaborating with Ripepe when Merapi began erupting, and Italian Civil Protection officials asked the scientists if they could provide data on how much lava was being erupted to the surface, he said.

"We do that a lot because we do a lot of studies on Kilauea, using the satellite to monitor the amount of lava rising to the surface," he explained.

The geologists did thermal mapping, using satellite imagery to monitor the temperature and speed of lava flowing from the Indonesian volcanoes.

After 16 days of observing the volcanoes, a 6.4-magnitude earthquake struck the island of Java, about 31 miles from Merapi and 165 miles from Semeru.

Three days later, lava began increasing at both volcanoes, Harris said, explaining it takes time for lava to reach the surface after the magma chamber is squeezed. "They were absolutely synchronous and at the end of nine days went back to the eruption rate before the earthquake."

Merapi and Semeru were too far apart to influence each other, indicating the earthquake on Java triggered the increased volume of lava, Harris said.

He offered two possible explanations:

"As the earthquake sends seismic waves through the magma chamber, you see it shaking the chamber like a Coke can, with a lot of bubbles, forcing the lava up the pipe to the surface."

Or, the earthquake could increase pressure on the chamber "like a hand tightening around a toothpaste tube," he said.

"We favor the Coke can, like the earthquake we had back here (Oct. 15). Imagine all that shaking in a can of Coke. If you don't take the lid off, you manage to get the bubbles more excited, and the Coke erupts explosively."

When lava began increasing at both Merapi and Semeru three days after the May 29 earthquake, Harris said, "We began to think, What's the only thing these two volcanoes have in common? That is the earthquake."

Intrigued by their discovery, which was reported in the January issue of Geophysical Research Letters, the geologists have launched a wider study.

They want to see how many volcanoes responded to quakes and what characteristics an earthquake needs to trigger a response, he said.

They did not see a response to the Oct. 15 earthquakes at Kilauea's Puu Oo vent, but they are seeing responses at other volcanoes, he said.

With more understanding of the relationship, Harris said, it might be possible to predict an increase in volcanic activity and potentially save lives with a warning.