Abstract

Epicenter patterns, focal depths, and focal mechanisms for earthquakes occurring between 1973 and 1981 in the Teton-Jackson Hole-southern Yellowstone region are presented in this study. Available earthquake information recorded prior to 1980 was combined with the results obtained from two microearthquake surveys operated in 1980 and 1981. Earthquakes used in this joint analysis met rigid standards for location accuracy, and hence the resulting data set provides the most complete, accurate and up-to-date information on seismicity in this region.

The majority of earthquakes in the region do not appear to be associated with mapped traces of Quaternary faults. The Teton fault appears to be active at the small earthquake level along some of its segments, although several segments, including the north-central segment which exhibits the greatest prehistoric displacement, appear to be quiescent. Seismicity in the Gros Ventre Range may be related to reactivation of older basement structures. Fault plane solutions in the region show predominately normal faulting with extension in an east-west to northwest-southeast direction.

Geologic seismic moment rates of 1.1 × 1024 dyne-cm/yr for the Teton region and 4.0 × 1023 dyne-cm/yr for the Teton fault were estimated using available geologic information on mapped faults. From the limited available data, a return period of 130 to 155 yr for a magnitude 6.5 to 7.5 earthquake is predicted for the Teton region, while the Teton fault has a predicted return period of 800 to 1800 yr for a magnitude 7.5 earthquake. A regional strain rate of 6.9 × 10−9/yr is also obtained.

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