BY PETER SUR | STEPHENS MEDIA HILO — A swarm of small earthquakes began in an area 3 miles west of Kilauea’s summit on Wednesday. The earthquakes are shallow, about a mile or two below sea level, and have been
BY PETER SUR | STEPHENS MEDIA
HILO — A swarm of small earthquakes began in an area 3 miles west of Kilauea’s summit on Wednesday. The earthquakes are shallow, about a mile or two below sea level, and have been occurring at a maximum rate of six per hour. The largest one, a magnitude 3.2, was strong enough to be felt.
A seismic swarm can be seen as a precursor to a lava outbreak, but in this case scientists say other factors are at play.
Geologist Janet Babb of the U.S. Geological Survey’s Hawaiian Volcano Observatory said the earthquakes are located in the well-known Kaoiki Fault Zone, where similar earthquake swarms occurred in 1990, 1993, 1997 and 2006, all without an eruption. Some of these swarms were stronger than the current one, she said.
“It’s a site of episodic seismicity. Especially since the 1983 Kaoiki earthquake, we’ve seen swarms in that area,” Babb said.
The magnitude 6.6 earthquake that struck the morning of Nov. 16, 1983, caused $7 million in damage from Hilo to Ka’u. Geologists believe the Kaoiki fault system is related to the ancient subsidence of Mauna Loa’s southeast flank.
There are other reasons why an eruption should not be expected here.
The area where Wednesday’s earthquake swarm began is outside of Kilauea’s rift zones, and no vents are known to exist in the area between the two volcanoes.
Magma on the move emits a distinct seismic signature, known as harmonic tremor, that would be picked up by HVO’s sensitive network of seismometers, and again, this is not the case.
Ground deformation — a sudden inflation in Kilauea’s slopes in response to magma moving into the area, as well as a deflation of the summit area — would be another signal that an outbreak is near.
In any case, Kilauea is still erupting lava elsewhere on the volcano, although the output is expected to decline in the next day or two. Magma rises from deep within the earth to a lava lake within Halemaumau crater, where it re-enters the East Rift Zone and emerges at Puu Oo. At the lava-covered end of Highway 130, guides at the county-operated Kalapana lava viewing area report a spectacular nighttime view as the flows move through the destroyed Royal Gardens subdivision.
“Oh boy, it’s been quite a good show,” said David Taylor, who described “six different fingers” of lava moving down Pulama Pali at night.
“It’s become a great show for the tourists. We’ve had a lot of people come down,” Taylor said.
The lava viewing area is open to the public from 2 p.m. to 10 p.m. daily; the last car is allowed in at 8 p.m.
Taylor said the flows are moving slowly and have not yet begun advancing across the coastal plain, several miles away from the location of the viewing area.
psur@hawaiitribune-herald.com
