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InSAR coherence time series - soil moisture as a proxy for alluvial fan age?

Rowena B. Lohman, Chelsea P. Scott, & Teresa E. Jordan

Published August 3, 2017, SCEC Contribution #7398, 2017 SCEC Annual Meeting Poster #107

When scientists can determine the ages of surfaces within a tectonically active area, they can turn observations of offsets and deformation into rates, repeat times and evaluations of hazard. Here, we explore the use of InSAR coherence time series, using data from the Sentinel-1 constellation, in characterizing alluvial fan surfaces within the Mojave Desert of Southern California. This is an extension of our previous work on examining the impact of three unusual rain events in the normally hyperarid Atacama Desert in Chile.

The coherence between two SAR images at a particular pixel depends on a range of factors, including surface roughness, change to the scattering properties of the area in between the two image acquisitions, as well as on the soil moisture profile beneath the surface. Because the latter can vary over time, InSAR coherence can sometimes, counterintuitively, be higher for a pair of images that are three years apart than for a pair that are only 12 days apart. We demonstrate how we solve for the effects of surface roughness, change, and relative variations in soil moisture for the events in Chile, with an illustration of how the timescales and magnitudes of the response vary dramatically between alluvial fans. We also show our initial results for the Mojave Desert, which is much less arid, but where there are more independent data constraining the characteristics of individual alluvial fans for comparison.

Key Words

Lohman, R. B., Scott, C. P., & Jordan, T. E. (2017, 08). InSAR coherence time series - soil moisture as a proxy for alluvial fan age?. Poster Presentation at 2017 SCEC Annual Meeting.

Related Projects & Working Groups
Tectonic Geodesy