A U.S. Geological Survey team looked for clues about how the earth moved in the Turkish quake

September 2, 1999
Web posted at: 10:32 p.m. EDT (0232 GMT)

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By Correspondent Rusty Dornin

SAN FRANCISCO (CNN) -- An Earthquake Hazard Team from the U.S. Geological Survey just returned this week from quake ravaged Turkey. Scientists from both countries are collaborating because of similarities between a fault in Turkey and California's San Andreas fault.

The scientists used a wide variety of techniques, from seismology and geodesy to visual observations.

As they walked along ruptures and fissures, the team looked for clues to just how the earth moved in the Turkish quake, which killed at least 14,000 people around the city of Izmit. Such clues point to striking similarities between Turkey's North Anatolian fault and one in the San Francisco Bay area. The surface of the land is similar, as is the frequency of earthquakes.

'We could consider them to be sisters'

"The North Anatolian fault is moving at about the same rate as the San Andreas -- its morphology is very similar -- so that we could consider them to be sisters," said Tom Holzer of the Geological Survey.

The biggest similarity is the density of population along the faults. If the Turkish earthquake had occurred in the Bay Area, it would have ruptured a 70 mile swath from Gilroy, California, to San Francisco, affecting millions.

New construction along a fault is not allowed in the United States, but plenty of buildings already stand on fault lines. There's not much that can be done to reinforce such buildings, and scientists say that's where the worst damage will occur if a huge quake hits the Bay Area.

One of the first objectives of the team was to look at structural damage and try to determine why buildings did or did not survive the quake.

Turkish building codes are similar to those in the U.S. -- including earthquake requirements. But Turkish-born Geological Survey scientist Mehmet Celebi said codes don't always equal conduct.

"Because contractors are not licensed, I think there is shoddy construction," Celebi said.

Earthquakes have occurred like dominoes along Turkey's North Anatolian fault since 1939. A scientist from the Geological Survey in 1996 anticipated the probable location of last month's quake. And he says he has a good idea where in Turkey the next quake will hit.

"This earthquake increases the possibilities of earthquakes arriving closer to Istanbul, but the amounts are not something we have a very good feel for," said Ross Stein of the Geological Survey.

While scientists can't predict exactly how big the next quake will be, or when, they are finding better ideas of the places that are likely to be hardest hit and why.

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