Rabaul Update: October 5, 1994
Summary of telephone conversation between CVO staff and the USGS/VDAP team at the
Rabaul Volcano Observatory (RVO) at 1500 hr PDT on Wednesday, October 5, 1994.
- Eruptive activity at Tavurvur is continuing at about the same level as yesterday. The
RSAM indicates that the level of eruption-related seismic activity is also roughly constant.
- The current level of seismic activity is comparable to pre-eruption background (a few
events/day large enough to be located).
- The rate of subsidence is slowing, based on tilt-leveling results and watertube tiltmeter
results. The watertube tiltmeter is located at RVO. Subsidence during the eruption is the
first change ever measured by the instrument.
- An RVO team has been re-measuring a leveling line from RVO to Matupit Island. As
of 2 days ago, there had been about 3 cm of subsidence at the caldera rim, about 6 cm
of subsidence near the base of the caldera wall, and about 9 cm of subsidence at the
wharf. The crew hopes to reach the airport today.
- Yesterday, the team installed 2 more seismometers - one near Vulcan and the other on the
west side of the caldera between Vulcan and RVO.
- The team plans to install another seismometer today.
- On the first day of the eruption, there were 3 active vents (not 5 as reported elsewhere).
Two vents were active at Vulcan, and one at Tavurvur.
- Most of the precursory earthquakes have not been located yet. The largest (M=5) was
located "under the harbor."