TECTONIC ACTIVITY ON BRAFFITS CREEK (IRON CO., UT), REVISITED

In 1977 R. Ernest Anderson (USGS) and Gary E. Christenson (UGS) installed an interlocking geodetic network consisting of eight stations across Braffits Creek, two miles south of Summit, Iron County, Utah, for the purpose of monitoring the apparently large strains indicated by landforms in the area. A high precision survey was conducted at that time and then repeated in 1981 and 1990. Results from the 1981 survey indicated that there had been both stretching and compression in the network; however, the results from the 1990 survey indicated only compression. In an effort to verify the results, I undertook a resurvey of the network. During summer and fall of 2004 six of the eight original monuments were relocated; an extensive and intensive search for the other two monuments was fruitless they had been destroyed during a chaining operation by Utah Department of Wildlife Resources. Using standard GPS techniques with one hour occupation at each station and post processing, five of the six monuments were resurveyed; early snow made it impossible to reach the sixth one. The 2004 results indicate active crustal shortening in all directions throughout the study area.