4 isle quake devices could give false data


POSTED: Friday, February 20, 2009

Scientists have upgraded Hawaii's seismic monitors after the 2004 Indian Ocean tsunami prompted the U.S. government to improve the nation's tsunami warning systems.

But some of the upgrades are merely temporary and have not been made to the highest standards. Slow-moving bureaucracy has delayed improvements in some cases.

Charles McCreery, the Pacific Tsunami Warning Center's director, initially thought the upgrades, which started in 2005, would take two or 21/2 years.

He says the center is now “;more than halfway done”; with improvements, but additional work remains.

The center has installed nine broadband stations around the islands from Kauai to the Big Island. But four of them are in seismically noisy areas, like near the shore where the rumbling of surf can vibrate the ground.

Others are near heavily developed areas where the sound of cars and other human population noise can disrupt readings.

The work includes moving some seismometers to better locations and getting landowner permission to install monitors on some properties.

“;We initially thought it wouldn't take us this long. We were probably a little naive,”; McCreery said. Even so, he said the center has made progress. “;Our capabilities today are hugely better than they were just a few years ago.”;

Most of the major tsunamis to reach Hawaii have been triggered by earthquakes across the ocean, like the April 1946 tsunami that flooded Hilo and killed 159 people. That wave was generated by a magnitude-7.1 earthquake in the Aleutian Islands.

In the past two centuries, Hawaii has been hit by only two major tsunamis generated by earthquakes located in the islands. They occurred in 1868 and 1975.

The 1975 temblor, magnitude 7.2, was centered off the coast of the Big Island. It set off a wave that crashed into 32 campers at Halape on the southern coast of Hawaii Volcanoes National Park. Two campers were killed and 19 injured.

After the Indian Ocean tsunami, which killed 230,000 people, Congress appropriated millions of dollars to upgrade the nation's tsunami warning networks.

Included in the funds was $922,000 to upgrade seismic monitors in Hawaii so the scientists at the Pacific Tsunami Warning Center could better predict what local earthquakes would generate deadly waves.

The most critical planned improvement was the installation of broadband seismometers, which can read a large range of earthquake vibrations.

Earthquakes release energy in a range of frequencies, so the more frequencies scientists are able to measure, the better they will be able to locate earthquakes and estimate their magnitudes.

Until 2005 the center had short-period monitors, which read only limited earthquake frequencies. It had one high-quality broadband station at its Ewa Beach headquarters and some lower-quality broadband stations on the Big Island.