| 3D slip vector orientations recorded by displaced landforms are difficult to constrain, and uncertainties associated with these measurements become increasingly challenging to assess as primary features degrade over time. We approach this problem from a remote sensing perspective by using terrestrial laser scanning (TLS) methods, which recently have been used to address an increasing number of questions in geology, geomorphology and tectonics. To measure 3D slip vectors recorded by landforms displaced along the 1954 Dixie Valley fault rupture in central Nevada, we developed an integrated TLS data collection and point-based analysis workflow that incorporates more accurate assessments of aleatoric and epistemic uncertainties using experimental surveys and Monte Carlo simulations. Our scanning workflow and equipment requirements are optimized for single operator surveying, and our data analysis process is largely completed using new point-based computing tools in an immersive 3D virtual reality environment. We measure slip vectors at two sites oriented ∼280°+/-3°, 29°+/-8° E and ∼283°+/-13°, 26°+/-4° E, respectively. We find that errors introduced by different survey methods are less than 2.5 cm, and are eclipsed by the 10-60 cm epistemic errors introduced by interpretations of site geometry. Our measurements are consistent with others of net extension direction during the 1954 earthquake, and support evidence that the Dixie Valley fault dips shallowly (∼30°) near its surface trace. However, though the higher resolution datasets we obtained with TLS were useful in visualization and in more accurately assessing uncertainties, denser constraints alone were not sufficient to reduce epistemic uncertainties and significantly improve the precision of our slip-vector measurements. |
