Identifying Pulverized Rocks At The Macro Scale Using Thermal Remote Sensing, A Test Case From The Mojave Section Of The San-Andreas Fault
Abstract
The identification of pulverized rocks along fault zones has been done so far by time-consuming geological mapping at a collection of sites. We suggest that thermal remote sensing is a more comprehensive and effective method that can be used to detect pulverized rocks. To examine this possibility we use scenes obtained by the MODIS/ASTER (MASTER) airborne simulator over the Mojave section of the SAF, focusing on the TIR (thermal infrared) part of the spectrum. Locations of pulverized rock were previously mapped in this area by Dor et al (2006). There are two possible approaches to identify pulverized rocks in TIR imagery. First, light can be scattered by a material by either surface or volume interactions. Surface scattering should dominate in a whole sample, while volume scattering has a greater effect in a ground-up sample, modifying the shape of the spectrum. Silicate minerals exhibit this behavior very clearly in the TIR spectrum. We therefore focus on pulverized granites and compare their spectra with that of their non-pulverized neighbors. Second, mechanical properties of rocks change as they get damaged, becoming more permeable and therefore conducting fluids and heat more efficiently. This also should produce differences between the thermal signatures of pulverized and non- pulverized rocks. In multispectral TIR images the radiance data are strongly correlated between channels, even after removing atmospheric effects, as the temperature information dominates over the emissivity spectra. It is therefore necessary to separate the temperature and the emissivity in order to study the effects of pulverization on the emissivity spectra. One limitation of using the TIR imagery is vegetation that may mask the underlying rocks, making the method feasible mostly in arid and semi-arid regions. Also, the spatial resolution of the MASTER images over SAF is 8m on average. This resolution, although relatively high compared with other TIR sensors, is still not sufficient to identify small outcrops of pulverized rocks. We currently use the SAF as a test case, and plan to expand our scope and examine faults that have not been previously mapped for pulverized rocks.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2006
- Bibcode:
- 2006AGUFM.T21C0437W
- Keywords:
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- 7250 Transform faults;
- 8118 Dynamics and mechanics of faulting (8004)