There could be trouble in paradise.
Based on the most detailed and comprehensive study of earthquake hazards ever made for the island of Hawaii, scientists now suspect the seismic danger is greater than expected, perhaps even greater than in Los Angeles.
The shaking, when it occurs, should arise on the flanks of major volcanoes. And the strength of ground motion there could surpass the shaking Californians experience near the San Andreas fault. Seismologist Fred Klein and his colleagues said the shaking on Hawaii's biggest island could be as much as 175% of the strength of gravity. "The largest earthquake we know of there, in 1868, was of magnitude 7.9," Klein said, with shaking "strong enough to throw rocks into the air."
It also touched off eruptions from two major volcanoes and a landslide that killed several people and a lot of livestock.
Klein, at the U.S. Geological Survey in Menlo Park, Calif., led a research team that reported results recently in the Bulletin of the Seismological Society of America. They estimated that in a 50-year period there is a 2% chance of an earthquake with shaking exceeding 175% of the pull of gravity, and a 10% chance of exceeding 120% of gravity. Such shaking would originate in the volcanoes themselves, a result of underground rock movements driven by volcanic forces.
In a heavily populated area, such shaking could be disastrous, similar to the violence that hit Northridge in 1992. But because the greatest danger lies close to the volcanoes, where few people live, Klein and his colleagues believe loss of life would be minimal. The closest large city, Hilo, is about 40 miles away.
Seismologist Ivan Wong, at the URS Corp. in Oakland, said Klein's report is valuable and a surprise. "What's important is that when we think of Hawaii, we think of the volcanic hazards, because they are so spectacular. But we know that the volcanic hazards are by and large predictable; we know where the lava flows are," Wong said.
But "this new Hawaii study is the first comprehensive assessment of the earthquake hazards on the Big Island, and from the perspective of knowledgeable scientists, we were surprised by how high the hazard is," Wong said. "The key point is that the hazard is as high as--or higher than--more notorious places such as Los Angeles and San Francisco."
An early result of the study, Wong added, is that government agencies are revising the building codes on the island to meet the hazard. New buildings will soon have to meet the highest standard for earthquake resistance.
Klein noted, however, that "the risk to life and property is much less than in Los Angeles, because development and population are very sparse in the high-hazard area, much of which is in Hawaii Volcanoes National Park."
In any case, the seismologists suggested that strong earthquakes must be given closer attention. Earthquakes are a well-recognized part of Hawaii's known hazards--including volcanic eruptions and seismic sea waves--as reason for concern.
Klein said the study of seismicity originally began because the U.S. Department of Energy was hoping to tap geothermal energy beneath the Big Island. The plan was to use the vast store of underground heat to run a power plant. Since then, however, the plans to generate electricity have been dropped.