Spatio–Temporal Analysis of Deformation at San Emidio Geothermal Field, Nevada, USA Between 1992 and 2010

Elena C Reinisch,Ian Warren,Kurt L Feigl,John Akerley,Michael Cardiff

doi:10.3390/rs11161935

Abstract

Although subsidence has been observed at the San Emidio geothermal field in Nevada using interferometric synthetic aperture radar since the early 1990s, the spatial extent and temporal evolution of the subsidence have not heretofore been quantified. Furthermore, the weather conditions and geographic location of San Emidio negatively affect interferometric image quality, causing low correlation amongst pairs. To address this, we introduce a new method for selecting pairs in areas of low correlation and small deformation signal using a minimum spanning tree method with a measure of image quality as the weighting criterion. We validate our pair selection approach by comparing our data products to SqueeSAR TM data products from a previous study at San Emidio. We also develop a deformation model which characterizes the spatial extent of subsidence at San Emidio in terms of volume change of the reservoir. After applying this deformation model to our data set of interferometric pairs, we examine the temporal relationship of the observed deformation with production and injection operations associated with geothermal power production.

Highlights

To determine the quality of our data selection, we compared the deformation measured from our minimum spanning tree (MST) data sets to those from Eneva et al [12] derived by TRE ALTAMIRA using the SqueeSAR procedure [26]
We compared the fields derived from each of the three SqueeSAR stacks to the corresponding gradients of pairs selected by MST
We have developed a new method to select a good set of interferometric pairs in areas of poor interferometric image correlation using a minimum spanning tree algorithm with a seasonally- and spatially-weighted measure of quality as the weighting criterion

Summary

Introduction

Since the late 1980s, interferometric synthetic aperture radar (InSAR) has proved itself to be a powerful geodetic technique capable of measuring surface deformation from a variety of sources. The two-dimensional structure of radar data along with the pair-wise nature of interferometry allow InSAR to capture both the spatial and temporal extent of deformation with uncertainty on the order of millimeters to centimeters. The availability of radar systems with diverse wavelengths and cadences increases the applicability of InSAR to a wide variety of geophysical studies, including monitoring geothermal processes. Differential InSAR (DInSAR) has been widely used to monitor surface deformation at many geothermal sites in the Western U.S Several studies have used observed subsidence to develop subsurface reservoir models (e.g., [3,4,5]). Data sets of multiple InSAR pairs have been used to determine temporal variations in subsidence at geothermal fields (e.g., [6,7])

Methods

Results

Discussion

Conclusion