Volcano Watch — Living Intelligently with geological hazards

As April draws to a close, so ends Tsunami Awareness Month in the State of Hawai`i. Tsunami Awareness Month featured programs and events coordinated among a number of government and private-sector organizations in order to increase awareness and understanding of the hazards posed by tsunamis. April was chosen, of course, because April 1, 1998, was the fifty-second anniversary of the tsunami generated by an earthquake in the Aleutian Islands that devastated Hilo and other parts of the State. We owe the Pacific Tsunami Museum and its director, Susan Tissot, a great deal of thanks for their efforts in bringing these programs together.

For similar reasons, April could also be regarded as "Earthquake Awareness Month" in Hawai`i. April 26, 1998, marked the twenty-fifth anniversary of the M6.3 earthquake that occurred deep beneath Honomu and caused an estimated $5 million in losses and damage in the Hilo and Hamakua Districts of the Big Island. In addition to its immediate impact, however, this earthquake also triggered national awareness of earthquake hazards in Hawai`i and motivated the installation of then-modern strong motion accelerographs by the U. S. Geological Survey's Office for Earthquake Research to record the shaking produced by large local earthquakes.

While it has been quite a long time since the most recent damaging earthquake or tsunami impacted Hawai`i, it is certain that we will experience others in the future. Professor Bruce Bolt, a world expert on earthquakes at the University of California at Berkeley, lectures that, the longer it has been since the last big earthquake, the sooner it will be before the next one.

We are not able to, nor perhaps would we want to, prevent earthquakes in Hawai`i because they are an inevitable part of the active volcanic processes that created and continue to shape our island. It is important, however, that we study these processes and learn how to live intelligently with the geologic and other natural hazards that we face, and to rationally assess and mitigate against the risks that they pose to us and our man-made environment.

Information on building earthquake-resistant structures is available from a number of different sources. U.S. Geological Survey staff from the Hawaiian Volcano Observatory have been involved with efforts to implement building codes that incorporate a realistic study of earthquake occurrence in Hawai`i, and we have described simple measures in earlier "Volcano Watch" articles.

Personal earthquake safety has been the topic of other "Volcano Watch" columns, as well as public discussions sponsored by many organizations, such as the UHH Center for the Study of Active Volcanoes. It would be very helpful to become familiar with the "Emergency Procedures" - or FRONT Yellow page - section of the telephone book, and additional information on earthquake and other emergency preparedness is available from Hawai`i County Civil Defense.

Because seismic waves travel more rapidly than water waves, a tsunami generated by an earthquake, either locally or teleseismically (by a distant earthquake like the April 1, 1946, tsunami), would be preceded by the seismic signals. If you are in shoreline or beach areas and feel an earthquake strong enough to make standing difficult, immediately go to higher ground or inland. Tsunamis generated by local earthquakes will travel around the island in a matter of minutes. This will not allow sufficient time for a warning to be issued effectively.

For tsunamis generated by a distant earthquake, pay attention to the issued warnings. Tsunami EVACUATION zones are shown in the telephone book. If you are in one of the evacuation zones when a warning is issued, leave those areas. Do not think for an instant about trying to out-run the incoming tsunami after you check out Hilo Bayfront.

A great deal of information is available about earthquakes, volcanoes, and tsunamis. Let's use Tsunami Awareness Month as a reminder of the need to learn more about our special environment and how to deal with its hazards.

Volcano Activity Update

Eruptive activity within Pu`u `O`o subsided during the past week, and lava was last seen on the crater floor on Saturday, April 25. Although there is no glow visible in the sky at night, lava continues to flow in the tube system from the vent to the coast. The lava enters the ocean at two locations - Waha`ula and Kamokuna. The public is again reminded that these two areas are extremely dangerous, and the National Park Service has restricted access to them because of frequent explosions accompanying collapses of the growing lava delta.

There were no earthquakes reported felt since last week.