Volcano Watch — Common sense in earthquake country

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The "Volcano Watch" column from January 22, which provided information about earthquake damage from the Kobe earthquake in Japan and then described some ways to reduce damage from future earthquakes here in Hawaii, has generated quite a lively discussion in the "Letters to the Editor" section of the Hawaii Tribune Herald.

The "Volcano Watch" column from January 22, which provided information about earthquake damage from the Kobe earthquake in Japan and then described some ways to reduce damage from future earthquakes here in Hawaii, has generated quite a lively discussion in the "Letters to the Editor" section of the Hawaii Tribune Herald.

Today's column addresses many of the issues brought up in those letters. This, and the January 22 "Volcano Watch" column were written by David Clague, Scientist-in-Charge at the U.S. Geological Survey's Hawaiian Volcano Observatory and a member of the Hawaii State Earthquake Advisory Board.

Three recent letters by RY W. Keuning (2/2/95), Roger Evans (2/23/95), and Aaron Anderson (2/28/95) in the Hawaii Tribune-Herald disputed recommendations made in that January 22 "Volcano Watch" column for earthquake safety. A recent letter by Gary Chock, a registered structural engineer and the Chairman of the Hawaii State Earthquake Advisory Board, presented the majority opinion of the structural engineering community in his response to the letter by Mr. Keuning.

The statement in the January 22 "Volcano Watch" that Mr. Keuning and Mr. Evans disputed was that "wood-frame buildings perform well during earthquakes, unless they are not tied down to a solid foundation." I then noted that "many homes in Hawaii are constructed with post-and-pier foundations. When earthquakes occur, such homes tend to walk off the piers causing severe structural damage." Such damage to homes on post-and-pier foundations has been documented by the staff of the Hawaiian Volcano Observatory following Hawaiian earthquakes in 1973, 1975, 1983, and 1989. Mr. Anderson noted that it was other deficiencies, such as insufficient cross-bracing and use of inappropriate nails, that led to the collapse of a house in Kaimu. Such deficiencies probably would not have led to the collapse of the house if it had stayed on its foundation. These are exactly the kinds of construction practices that are addressed by the Uniform Building Code! We expect that more of this type of damage will inevitably occur from the next large earthquake here.

As Mr. Chock pointed out in his letter, the wisdom of the structural engineering community, derived from cumulative observations over nearly 70 years from evaluating the integrity of different types of structures during numerous damaging earthquakes around the world, is reflected in the Uniform Building Code (UBC), as established by the International Conference of Building Officials (ICBO). The Uniform Building Code is not a set of regulations developed by government, although it is local or state government that adopts and enforces the UBC. Adoption and enforcement of appropriate building codes are done to provide for public safety and to reduce the costs of natural disasters to society. You can think of the small added costs of building according to the UBC as an insurance policy that you pay when you build your house that protects your family and your investment from future greater losses.

The current UBC, as adopted by the County of Hawaii last year for an area with high earthquake and wind hazards, clearly supports the statements I made in the January 22 column. Mr. Evans indicates in his letter that Mr. Keuning is a structural engineer by profession. If this is the case, Mr. Keuning's viewpoint is far from the consensus in the structural engineering community.

Evans also notes that living in Hawaii is different from living in any other state. This is no excuse to expose our populace to unnecessary risks from earthquakes or windstorms. Houses here are subject to the same forces as they are anywhere else--the lateral and vertical forces of the earthquake or windstorm and the vertical force of gravity. Neither force is different in Hawaii than it is anywhere else, and neither is the resulting damage.

Anderson's letter indicates a misunderstanding about terminology used by the Federal Emercency Management Agency (FEMA). They have correctly recommended low-density housing in lava flow hazard zones 1 and 2. Anderson interpreted low-density to mean light-weight houses, whereas what FEMA means is to have few houses per square mile. It is worth noting that homes on this island, even those in lava flow hazard zones 1 and 2, are more likely to be damaged during a large earthquake than to be overrun by lava. Many of the suggestions for earthquake preparedness that I made in the "Volcano Watch" column originate in FEMA literature.

I am unsure of what Anderson means by "renewable" or "sustainable" housing or building policies. I gather that he means housing that has to be renewed, or rebuilt, frequently after damage from natural events. Adherence to the UBC during construction will reduce or eliminate damage during future natural disasters, thereby vastly reducing the need for rebuilding, such as Anderson describes was the case in Kaimu following the 1989 earthquake.

Evans' remarked that the "scientists should stick to reading the seismographs and try to figure out when the next big one (large earthquake) will hit." Seismologists can, and do, evaluate past and present seismic activity to determine the likelihood of future damaging earthquakes in a region. This evaluation is what determines the earthquake hazard zonation for a region. The Island of Hawaii is presently rated as zone 3, the next-to-highest zone, although a recent evaluation of the history of earthquake activity here indicates that Hawaii falls well within the criteria for the highest zone, and should be rezoned.

The determination of the earthquake hazard or the appropriate earthquake zonation does nothing to reduce the damage from future earthquakes unless that information is acted upon by the public and by public officials. Practical information on steps that can be taken to mitigate the known hazards are a critical part of the information the scientific community should provide. The UBC contains information from the seismological and structural engineering communities to reduce the risk of damage from future earthquakes and windstorms.

The letter by Mr. Titus Bontea, strongly criticized Mr. Chock and called for keeping government out of our lives when it comes to building practices. He specifically cited collapsed public works (highways) that occurred during both the Northridge and the Kobe earthquakes as examples of how the building code does not improve structures.

The truth of the situation is that in Northridge and in Kobe, damage to highways and buildings was heavily concentrated in structures built before modern earthquake-resistent building codes were adopted. In other words, had all the structures been built to modern codes, the damage would have been far less. It is interesting to note that the Northridge and Kobe earthquakes each occurred in densely populated areas, and each had a magnitude of 6.7. Yet the damage in Northridge was $30 billion and 57 dead compared to more than$100 billion and 5,100 dead in Kobe. The main difference was the much greater proportion of buildings in Kobe that had been constructed before adoption of modern building codes in the early 1980s.

Mr. Bontea also incorrectly assumed that Mr. Chock was a government official. The Hawaii State Earthquake Advisory Board is composed mainly of geoscientists and structural engineers who volunteer their time to serve in an advisory capacity to the Hawaii State Office of Civil Defense. The board meets four times each year to address earthquake preparedness in the State of Hawaii. Among the accomplishments of the four-year-old Board are studies of ground motion intensity and liquefaction on Oahu; development of a complete earthquake catalog for the State of Hawaii; installion of additional strong motion instrumentation on Hawaii, Maui, Oahu, and Lāna‘i; addition of additional stations to the seismic network monitoring Mauna Loa Volcano; management of a pilot vulnerability study of essential fire stations and hospital facilities in Hawaii County; organization and training of volunteer post-disaster damage assessment and building safety engineers; and organization of several seminars and workshops for government officials, the public, and professional architectural and structural engineering communities.

I have used, and will continue to use, the "Volcano Watch" column as a vehicle to convey important information about seismic and other geologic hazards, and ways to mitigate those hazards. Individuals rarely assume these risks by themselves, as society (all of us) pays, in whole or in part, for disaster relief and rebuilding when natural disasters strike. Natural disasters may be natural, but they are disasters only because we were not prepared.