January 17, 1997

A weekly feature provided by scientists at the Hawaiian Volcano Observatory.

New Seismology Projects for 1997

1997 is off to a promising start at the Hawaiian Volcano Observatory (HVO). Already in the works for the New Year are two projects aimed at improving our views into the volcano and into the island with new seismic monitoring tools.

First, we are preparing for the return, next month, of 30 visiting seismologists from Japan, Italy, Alaska, and from the U S Geological Survey's Western regional office in Menlo Park, California. We will continue our cooperative study of volcanic processes beneath Kilauea's summit caldera under the auspices of the Japan-US Science and Technology (JUST) agreement.

Some readers will recall that, last January, scientists from the same group of universities and agencies joined HVO staff in the first JUST seismic project. In that project, we deployed a large number of portable seismic recorders at Kilauea's summit to record the different earthquake signals generated by the volcano. Results from last year's study include a better understanding of how the seismic signals propagate through Kilauea's summit region. We also recorded the earthquake swarm on February 1, 1996, that caused considerable concern about a possible eruption in the summit crater.

This year the JUST study will again focus on Kilauea's summit region. We will deploy approximately 100 portable seismic recorders and sensors in semicircular, diamond, and linear arrays or antennas. The array configurations will allow us to tune our recordings and determine directional propagation characteristics of the seismic signals. Seismic waves travel at different speeds in different directions. To last year's types of sensors, we are also adding a number of ÏbroadbandÓ seismometers to record a more complete spectrum of seismic signals. The JUST project will be in operation at HVO in early February for a period of about 10 days.

In addition to the JUST study, HVO is working with a university and Federal consortium on the installation of a new, permanent seismographic station in the Humu'ula Saddle region. This new station will feature both a broadband, digital seismograph and a strong-motion accelerometer. The broadband sensor will be installed at the bottom of a 100 meter-deep well. This will increase the sensitivity of the station by avoiding the noise generated at the Earth's surface. The accelerometer can record large local earthquakes, up to magnitude 8, without going off scale. The data from these sensors will be transmitted to HVO and be incorporated into our existing data streams. The site will also be linked to O'ahu and to the mainland.

The new borehole station is sponsored by the Incorporated Research Institutions for Seismology (IRIS) consortium. IRIS has about 100 member institutions whose goal is to improve our understanding of the Earth with a number of different projects. Because of our unusual location in the middle of the Pacific Ocean, the IRIS working group for global, digital seismographic networks has been interested in stations in Hawaii for quite some time. HVO will benefit from the greater quality and cleaner signals from the broadband system.

Through HVO partnerships and cooperative studies like IRIS and JUST we are able to upgrade our operational capabilities and conduct research that will allow us to improve our understanding of how volcanoes work.

Eruption Update

The eruption of Kilauea Volcano continues. Lava continues to flow into the ocean via a single main feeder tube to the coastal bench. There were substantial rockfalls within Pu'u O'o vent. No new breakouts were seen on the flowfield. There were no felt earthquakes on the Island last week.