Field imaging spectroscopy: A new methodology to assist the description, interpretation, and archiving of paleoseismological information from faulted exposures

Daniel Ragona, Jean B. Minster, & Thomas K. Rockwell

Published October 2006, SCEC Contribution #1005

We present a new methodology to acquire, interpret, and store stratigraphic and structural information from paleoseismic exposures. For this study we employed portable hyperspectral cameras to acquire field-based visible near-infrared (VNIR) and short-wave infrared (SWIR) high spatial/spectral resolution images. We first analyzed 400 small sediments cores using a hand-held, single-pixel spectrometer (VNIR-SWIR) to determine the feasibility of the method and to assess its potential problems. We then acquired high-spatial resolution (submillimeter) spectral data of a large sample (60 × 60 cm) and four cores (7.5 × 60 cm) of faulted sediments from a paleoseismic excavation using portable push broom AISA hyperspectral scanner. These data, which contain 244 (VNIR) and 245 (SWIR) narrow contiguous spectral bands between 400 and 1000 and 960 to 2403 nm, respectively, were processed to obtain the reflectance spectra at each pixel. In this study we are focusing on the analysis of the short-wave infrared data sets (SWIR). The SWIR data were transformed into relative reflectance and geometrically corrected and processed with well-known imaging processing algorithms. Selected spectra were then used to create false color composite images that best display the faulted stratigraphy. We compared the hyperspectral images to those recorded by a digital camera as well as directly to the field sample and show that the reflectance properties of the materials in the SWIR region cannot only enhance the visualization of the sedimentary layers and other features that are not obvious to the human eye but can also make visible many detailed features that were not visible in the digital photography. This new data collection and interpretation methodology, herein termed field imaging spectroscopy, makes available, for the first time, a tool to quantitatively analyze paleoseismic and stratigraphic information. In addition, hyperspectral data sets in the visible short-wave infrared spectral range provide a better alternative for data storage. The reflectance spectra at each pixel of the images provide unbiased compositional information that can be processed in a variety of ways to assist with the interpretation of stratigraphy and structure at a site.

Key Words
United States, methods, imagery, paleoseismicity, Quaternary, site exploration, geophysical methods, satellite methods, excavations, Hog Lake, cores, infrared spectra, Cenozoic, California, lithofacies, infrared methods, Southern California, sampling, spectra, reflectance, remote sensing, field studies

Citation
Ragona, D., Minster, J. B., & Rockwell, T. K. (2006). Field imaging spectroscopy: A new methodology to assist the description, interpretation, and archiving of paleoseismological information from faulted exposures. Journal of Geophysical Research, 111(B10309). doi: 10.1029/2006JB004267.