Structural properties of the American Fork, Provo, and part of the Spanish Fork subsegments, Wasatch normal fault zone, Utah (OFR-186)

By: R. L. Bruhn, J. J. Lee, and W. A. Yonkee

This report discusses the structure of the southern Wasatch fault zone between the Traverse Mountains and Springville, Utah. This includes the central and northern part of the Provo rupture segment. Subsequent work resulted in subdivision of this segment into three subsegments, the American Fork, Provo, and Spanish Fork subsegments as encountered form north to south. These three subsegments may not rupture independently to generate separate large earthquakes at distinct time intervals, at least at the temporal resolution available in paleoseismic information. However, the three subsegments have distinct geometry in map view. All three subsegments have ruptured in Holocene time, probably generating earthquakes of Richter magnitude 7 or greater. Rupturing may or may not have occurred on all three subsegments at the same time, but apparently ruptures within the three subsegments did not breach the boundaries at the ends of the Salt Lake and Nephi segments, at least during the last several major surface faulting events.

The report is divided into three sections. Procedures used in the field and office are described in the first section. The orientation of the Wasatch fault zone, the geometrical properties of segment and subsegment boundaries and fault slip-directions are discussed secondly. The population of faults exposed in the footwall of the Wasatch fault zone and their implications for seismicity and structure are then described.

Other Information:
Published: 1990
Pages: 43 p.
Location: Utah County
Media Type: Paper Publication