Integrated three-dimensional interpretation of major concealed faults beneath Mapleton, Utah County, Utah using gravity data, supported with magnetic data

摘要

Gravity and magnetic surveys were conducted to locate major concealed faults beneath Mapleton, Utah County, Utah, a developing city along the Wasatch Front, 80 km south of Salt Lake City, Utah. Although the magnetic data are not as useful for this study due to cultural magnetic noise and logistical limitations in acquiring dense data sets, these data do play a backup role in supporting the gravity data by helping to constrain the interpreted models of the major concealed faults. Data were collected at 196 stations and were processed using conventional techniques. Regional trends were calculated using trend analysis, and residual data were modeled using self-consistent iterative modeling. Ambiguities in the subsurface models were reduced by (1) incorporating data from previous geophysical surveys, surface mapping, trench studies, aerial photos, well data, and earthquake data; (2) integrating the gravity and magnetic data; and (3) correlating the modeled cross sections along numerous selected profiles.The modeled profiles and integrated three-dimensional interpretation indicate that there are four major fault blocks beneath the Mapleton area. These fault blocks are bounded by a series of west-dipping synthetic, listric faults. Depths to the fault blocks range from <100 m in east Mapleton to 1800 m in west Mapleton. These faults are potential earthquake threats, especially for possible surface rupture.