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Stories a Trench Can Tell
Determining St. George Earthquake Threat April 15, 2009
Geologists are digging trenches, south of St. George, Utah, that will hopefully help them figure out the potential threat of large earthquakes in the area. Geologists from the Utah Geological Survey (UGS) and the Arizona Geological Survey (AZGS) are digging into the Washington fault about three miles south of the Utah-Arizona border in Arizona. "The fault is three miles east of St. George and runs through the nearby city of Washington," said Bill Lund, UGS senior geologist. "There is evidence of surface rupturing earthquakes. Our goal is to figure out how often the fault has moved and how large the earthquakes have been. That will help us understand the potential for future earthquake activity." The Washington fault is approximately 43 miles long, extending from northern Arizona to just north of Washington, Utah. It is referred to as the ‘little sister’ of the larger nearby Hurricane fault. The displacements of the two faults run opposite each other. Lund hopes the trench will also help geologists understand what causes the opposite displacements. Three trenches have been excavated in Arizona because the Utah portion of the fault is on Bureau of Land Management preserve. "We have exposed the Washington fault in two of our three trenches - looks like we will get some good new information on a fault that runs right through the city of Washington," said Lund. The trenches are expected to be open through May, though most of the study and observation will be complete within two weeks. |
