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At SCG we believe it is key to study the whole range of Earth deformation, from the near instantaneous (i.e., earthquakes) using seismic data, to the longer-term (i.e., slow fault slip, hydrological processes) using geodetic data. We therefore work with geodetic instruments and data, including creepmeters, InSAR, borehole strainmeters, and cGPS, to perform geodetic characterization. Wherever possible we combine geodetic and seismic observations to research tectonic and hydrological processes.
Creepmeter installations
Creepmeter installations
We have experience installing creepmeter instruments across strike-slip faults, including the San Andreas fault in California. These sensitive (micrometer scale resolution) near-surface instruments measure shallow movement/displacement along the fault, or any extension across the two ends of the instrument.
Interferometric Synthetic Aperture Radar (InSAR) Processing
Interferometric Synthetic Aperture Radar (InSAR) Processing
We process InSAR images to evaluate shallow deformation from tectonic processes like earthquakes and slow fault slip, as well as land subsidence, changes in aquifer storage, and changes in geothermal reservoirs. To the left, we have an example of a phase wrapped (top) and georeferenced phase unwrapped (bottom) interferogram from the 2017 M 7.3 Ezgeleh, Iran blind thurst earthquake with almost 6 meters of displacement.
Borehole strainmeters
Borehole strainmeters
Borehole strainmeters are very sensitive instruments that can measure strains on the order of nanoradians. These instruments can be very useful to detect small geodetic deformations not observed by other means; however, these instruments also have high noise levels. We process and analyze borehole strainmeter data to detect fault displacement and hydrological signals, and model these processes in conjunction with other data (e.g., earthquakes, cGPS, creepmeters, InSAR). To the right is an example of strainmeter data used to model slow, aseismic slip on the San Jacinto fault in southern, California (Shaddox et al., 2021).
Top right: Strain data from four borehole straimeters, plotted with seismicity data.
Bottom right: Results of the model inversion of the strain changes using an Okada dislocation; fault geometry constrained by repeating earthquakes.
Continuous Global Positioning System (cGPS)
Continuous Global Positioning System (cGPS)
We have serviced cGPS stations in remote locations like Alaska and analyze cGPS data to detect larger (>M5 earthquakes and slow slip events) and long-term tectonic and hydrologic processes.
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