ST. GEORGE — Residents of Utah's Dixie could be in for a seismic shock one day, according to the Utah Geologic Survey's recent analysis of the Washington Fault.

Bill Lund, UGS senior scientist and southern Utah regional geologist, said the Washington Fault runs straight through Washington city, a mere five miles from neighboring St. George.

"If what we suspect is true, that the Washington Fault is more persistently active in recent geologic time than we thought, then the hazard rating level in the area could go up," said Lund. "That would be reflected in building codes. The bottom line is that St. George is already designing for a certain earthquake hazard and this may require them to consider other seismic criteria."

Residents of Washington County shouldn't be worried by this latest report, said Lund, but they should recognize they live in an earthquake hazard zone. The nearby Hurricane Fault is another potential source of large earthquakes, he noted.

"Ground shaking is by far the greater hazard, but we also don't want people to put buildings on places where ruptures occur," Lund said.

The Washington Fault was added to the agency's list of high-priority faults to study because of its proximity to major developments in the county. Washington County has often been noted as one of the fastest-growing areas of the state and nation.

Over the past decade, the population of St. George boomed from a count of nearly 30,000 residents to almost 90,000 people. During that same time frame, the Quail Creek Water Plant was doubled in size, regional water lines were constructed and millions have been spent on public transportation projects.

If the UGS can show the Washington Fault was a more active fault in the recent geologic past, it could eventually be added to the National Earthquake Hazard Maps, Lund said.

"Our goal is not to scare people, but rather to make sure the earthquake hazard is adequately characterized and that people are aware of the potential hazard," he added.

The agency hopes to find another location for an additional research trench, which could help scientists develop a timeline of when the fault produced its most recent earthquakes.

"We're going to look at the fault from the air and walk every inch of it," said Lund. "We want to know the hazards. We have a lot at risk."

---

E-mail: nperkins@desnews.com