Applications of airborne and terrestrial laser scanning to paleoseismology
byDavid E. Haddad, Sinan O. Akçiz, J Ramón Arrowsmith, Dallas D. Rhodes, John S. Oldow, Olaf Zielke, et al.
Geosphere. August 2012, Vol. 8, Issue 4, Pages 771–786.
Paleoseismic investigations aim to document past earthquake characteristics such as rupture location, frequency, distribution of slip, and ground shaking intensity—critical parameters for improved understanding of earthquake processes and refined earthquake forecasts. These investigations increasingly rely on high-resolution (<1 m) digital elevation models (DEMs) to measure earthquake-related ground deformation and perform process-oriented analyses. Three case studies demonstrate airborne and terrestrial laser scanning (ALS and TLS) for paleoseismic research. Case 1 illustrates rapid production of accurate, high-resolution, and georeferenced three-dimensional (3D) orthophotographs of stratigraphic and fault relationships in trench exposures. TLS scans reduced the preparation time of the trench and provided 3D visualization and reconstruction of strata, contacts, and permanent digital archival of the trench. Case 2 illustrates quantification of fault scarp degradation rates using repeat topographic surveys. The topographic surveys of the scarps formed in the 1992 Landers (California) earthquake documented the centimeter-scale erosional landforms developed by repeated winter storm-driven erosion, particularly in narrow channels crossing the surface rupture. Vertical and headward incision rates of channels were as much as ∼6.25 cm/yr and ∼62.5 cm/yr, respectively. Case 3 illustrates characterization of the 3D shape and geomorphic setting of precariously balanced rocks (PBRs) that serve as negative indicators for strong ground motions. Landscape morphometry computed from ALS-derived DEMs showed that PBRs are preserved on hillslope angles between 10° and 40° and contributing areas (per unit contour length) between 5 and 30 m2/m. This situation refines interpretations of PBR exhumation rates and thus their effectiveness as paleoseismometers. Given that earthquakes disrupt Earth's surface at centimeter to meter scales and that depositional and erosional responses typically operate on similar scales, ALS and TLS provide the absolute measurement capability sufficient to characterize these changes in challenging geometric arrangements, and thus demonstrate their value as effective analytical tools in paleoseismology.