# Volcano Watch — HVO shares its research with the international scientific community

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Last week, six staff members of the U.S. Geological Survey's Hawaiian Volcano Observatory (HVO) braved holiday travel and chilly rain to participate in the Fall Meeting of the American Geophysical Union in San Francisco.

This is a helicorder seismogram displaying vertical ground velocities at the summit of Hualālai volcano south of the earthquake epicenters. Each line represents 10 minutes and time increases from left to right. Each line continues on the line below. The seismogram starts at 2 am and ends at 2 pm HST on October 15, 2006.

The top 26 lines show typical ground vibrations before the earthquake. The M6.7 earthquake immediately goes off scale. The M6.0 earthquake arrives on the line below. Each of the signals that resemble Christmas trees turned horizontal are aftershocks.

(Public domain.)

Nearly 14,000 scientists from all over the world attended the meeting to present their recent findings and learn of advances in their fields of study. Hundreds of sessions ran concurrently, on topics ranging from arctic warming to the composition of Mars to weather prediction. Research in Hawaii was well-represented with presentations by HVO staff and associates on volcanic and earthquake processes.

The October 15th Kiholo Bay and Mahukona earthquakes were the topic of a "late-breaking" afternoon session. HVO's seismologist Paul Okubo described the earthquakes and their effects. Preliminary results of research were presented about the causes of the earthquakes, and about what the earthquakes revealed about the properties of the Earth beneath the islands.

The Pacific Tsunami Warning Center summarized its response to the earthquakes. Using data primarily from HVO's seismic network, they were able to issue a warning within 2 minutes of the first earthquake. They started to feel the shaking (on Oahu) just as the warning went out! They expected the tsunami hazard to be small, based on the depth of the earthquake, and indeed, the total amplitude of the resulting tsunami was only 8 cm (about 3 inches). They continue to strive for even quicker warning times.

We showed results that indicate fairly small, permanent displacements of the ground surface-on the order of a few cm (about an inch)-in the vicinity of the earthquakes and slightly smaller as far away as the summits of Mauna Kea and Mauna Loa. These data should help constrain the source mechanism of the earthquakes.

In another session, HVO scientist Asta Miklius demonstrated that the swelling of Kīlauea Volcano over the last three years was due to an increase in magma supply. The inflation was very rapid during the last year, when the ground at the summit rose over 20 cm (about 8 inches). We calculated that at least double the usual amount of magma was coming up into the system, but not all of it was able to get to the eruptive vent at Puu Oo. The excess magma pressurized the summit and both rift zones of the volcano. At the beginning of October, however, the inflation suddenly stopped, suggesting that the volume of magma supplied to the shallow volcano plumbing system has returned back to "normal" levels.

Don Swanson shared results of a detailed study of deposits from an explosive eruption from Kīlauea's caldera in the late 1500s or early 1600s. He inferred that the eruption column was at least 10-15 km (6-9 miles) high, showing the potential hazard of such explosive eruptions to aircraft and nearby residents.

Other HVO presentations focused on a variety of interesting phenomena that we are able to observe with recent advances in technology. Michael Poland illustrated how satellite-borne radar data could be used to map active lava flows in addition to providing excellent spatial resolution of ground motion. Recent radar data more fully define the extent of deforming zones on Kīlauea and Mauna Loa than was possible with measurements of specific points on the ground. Tim Orr showed a sampling of what we've observed and learned on the active flow field and lava delta with inexpensive time-lapse camera systems that he builds himself.

Numerous other talks and posters used data from the current eruption of Kīlauea to investigate fundamental eruption processes. We were glad to see that Hawaii data continues to be useful to the international volcano science community. At the same time, we were inspired by work on other volcanoes and appreciated the opportunity to share ideas, learn new study methods, and explore possibilities for future work with fellow scientists.

We hope our efforts to communicate and collaborate in our research will help us better understand-and thus better mitigate-the hazards associated with living on active volcanoes.

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### Volcano Activity Update

Eruptive activity at Puu Oo continues. On clear nights, glow is visible from several vents within the crater. Lava is fed through the PKK lava tube from its source on the southwest flank of Puu Oo to the ocean. About 1 kilometer south of Puu Oo, the Campout flow branches off from the PKK tube. The PKK and Campout tubes feed two widely separated ocean entries, at East Laeapuki and East Kailiili, respectively. Both entries are located inside Hawaii Volcanoes National Park.

In the past week, intermittent breakouts from the Campout tube have occurred on the slope of Pulama pali and on the coastal plain. Active lava from the south side of the Campout flow spilled into the ocean for a short time this week between the East Laeapuki and East Kailiili entries.

Access to the sea cliff near the ocean entries is closed, due to significant hazards. The surrounding area, however, is open. If you visit the eruption site, check with the rangers for current updates, and remember to carry lots of water when venturing out onto the flow field.

Three earthquakes beneath HawaiI Island were reported felt within the past week. A magnitude-2.9 earthquake at 10:12 a.m. H.s.t. on Wednesday, December 20 was located 23 km (14 miles) north of Kailua at a depth of 4.5 km (2.8 miles). A magnitude-2.2 earthquake at 7:14 a.m. on Tuesday, December 19 occurred 10 km (6 miles) east-northeast of Kawaihae at a depth of 7 km (4.3 miles). The largest event reported felt was a magnitude-3.0 earthquake 8 km (5 miles) south-southwest of the summit of Mauna Loa at a depth of 4 km (2.5 miles).

Mauna Loa is not erupting. During the past week, earthquake activity remained low beneath the volcano's summit (one earthquakes located). Extension of distances between locations spanning the summit, indicating inflation, continues at slow rates.