Scientists no help when it comes to faults

Wednesday, Aug. 18, 1999 | 11:33 a.m.

Although scientists can predict where an earthquake might strike, they cannot tell those living near a fault when the Earth will unleash its stress.

Major faults such as Turkey's North Anatolian and California's San Andreas build up tension between moving plates, until the stress becomes overwhelming and produces a large quake such as Turkey's 7.8 magnitude temblor on Tuesday.

A 5.0 magnitude quake rumbled in Bolinas, Calif., later Tuesday, and some wondered if the temblors would continue in a chain reaction around the world.

Actually, California's smaller quake is a coincidence, scientists say. It is the same as a gambler rolling the dice twice and turning up sevens both times, an unpredictable event, a random chance.

Geologists have blanketed the Earth with a network of seismic monitors to detect quakes such as the one that has killed more than 3,500 people on Turkey's North Anatolian fault, which scientists predicted would produce a major temblor within 30 years.

While the science of forecasting earthquakes is improving, it is still inexact, experts say.

Advances in monitoring the movement of the earth's crust by the California Institute of Technology and other institutions using satellites has refined the way scientists check the Earth's stress level, Cal Tech geologist Tom Heaton said.

Cal Tech geologist Brian Warnecki has blanketed a proposed high-level nuclear waste repository site 90 miles northwest of Las Vegas at Yucca Mountain using the satellite network.

The Cal Tech team unexpectantly recorded Yucca Mountain's crust creep from 1990 until 1997 and is doing a more extensive study of what the movement means. The government is studying the mountain as a potential tomb for 77,000 tons of deadly radioactive waste.

By watching crustal creep and stress increasing along major fault lines scientists hone their skills at predicting when the major quakes might occur.

Researchers also comb ancient and modern records for the frequency of earthquakes and have found they occur where continents collide. Turkey, Iran and Iraq are riding a moving plate heading for Europe. California is riding the Pacific plate, heading for Alaska.