Detailed mapping of normal fault array geometry using dm-scale high resolution topographic imagery from the Volcanic Tablelands, Bishop, California

Tyler R. Scott, Ramon Arrowsmith, Chelsea P. Scott, & Daniel Lao Davila

Published August 15, 2018, SCEC Contribution #8830, 2018 SCEC Annual Meeting Poster #170

The Volcanic Tablelands in northern Owens Valley California offer an unusual exposure of well-preserved and discontinuous meter to kilometer long normal faults formed by regional E-W extension. The region is one of the best natural laboratories to study normal fault growth evolution. Our goals are to capture fault zone structure and geomorphology at very fine scales to identify geometric patterns and eventually forecast normal fault evolution in the Volcanic Tablelands and apply the results to normal faults from other geographic regions. Understanding growth of normal faults will help predict and develop reliable models for rupture dynamics and potentially mitigate seismic hazard.
Our research team acquired 13,912 aerial photographs using 2 unmanned aerial vehicles covering ~20 km2. We mapped normal fault traces, relay ramps, and fracture patterns from the 10 cm resolution Structure from Motion digital elevation models and orthoimagery derived from the aerial photographs. We began our multi-resolution detailed geomorphologic and structural mapping at a 1:5000 scale and progressively moved to finer scales. We assumed that more evolved faults are narrower and have a straighter trace than less evolved faults. We focused on two N-S trending, normal fault strands at 37.449N, 118.441W.

The northern most fault (FZ1) is ~1.5 km long, has a maximum height of 20 m, and dips to the west. The southern strand (FZ2) is 1.5 km long, has a maximum height of 30 m, and dips to the east. The two faults are deflected away from each other at their intersection. This results in a topographic low broken by inward facing scarps on each side. FZ1 shows few additional splays, breaks, and changes in fault trend confined to within 50 m of the fault. FZ2 is similar to FZ1 along the fault tips, but in the central 1.3 km portion is dominated by rhythmic and partially segmented with ridges and troughs.

We interpret that this fault geometry represents a preserved relay ramp formed by growing en echelon faults and relay ramp breach processes. Because FZ2 is geometrically more complex than FZ1, we infer that FZ1 is structurally more evolved.

Key Words
fault evolution, Bishop, Structure from Motion

Citation
Scott, T. R., Arrowsmith, R., Scott, C. P., & Lao Davila, D. (2018, 08). Detailed mapping of normal fault array geometry using dm-scale high resolution topographic imagery from the Volcanic Tablelands, Bishop, California. Poster Presentation at 2018 SCEC Annual Meeting.

Related Projects & Working Groups
Fault and Rupture Mechanics (FARM)