InSAR-derived Vertical Land Motion over southern California: A Scalable Approach leveraging the growing, open-source ARIA-S1-GUNW archive

Simran S. Sangha, Marin Govorcin, Gareth J. Funning, & David Bekaert

Submitted September 10, 2023, SCEC Contribution #13287, 2023 SCEC Annual Meeting Poster #065

We use state-of-the-art open-source methods to produce standard InSAR science products freely distributed through a NASA Data Active Archive Center at the Alaska Space Facility. Specifically, we generate the Advanced Rapid Image Analysis (ARIA) project’s formulated Sentinel-1 Geocoded Unwrapped Phase product (ARIA-S1-GUNW), an official NASA standard 90 meter InSAR product that enables the measurement of precise land surface displacements. Using this archive, we focus on generating higher-level InSAR products, i.e. decomposed vertical displacements that may help in better separating faulting and tectonic from hydrologic and anthropogenic signals. For this, relative line-of-sight (LOS) InSAR displacements need to be re-referenced and projected to a geodetic reference frame. This is commonly done by referencing InSAR with GNSS observations, and decomposing LOS displacement vectors into North-South, East-West, and Up-Down directions with defined assumptions. However, it could be challenging to perform these tasks at large scales due to multiple tracks of relative InSAR observations with different imaging geometries and noise levels, as well as various non-linear and long-wavelength ground motion signals.

Here we present a scalable approach to derive quasi-vertical land motion from relative LOS InSAR observations over large scales, with a focus on SAR observations and ground motion settings over southern California. The approach consists of two steps: 1. re-referencing InSAR displacement rates with a GNSS model projected in LOS, and 2. LOS decomposition with support of external ground motion data to solve the undetermined equations. Re-referencing is performed by estimating a surface between low-pass filtered InSAR displacement rates and a coarse GNSS velocity model (50 x 50 km), thereby constraining the short-wavelength and long-wavelength displacement signals with InSAR and GNSS, respectively. After re-referencing, we apply pixel-wise LOS decomposition of InSAR observations with additional external data (e.g. GNSS) providing horizontal ground motion. Measurement and model uncertainties are propagated to the final result, as associated product quality metrics. With a motivation towards estimating the deformation field at high resolution in 3D, this effort aligns with a SCEC5 research goal of refining the CGM.

Key Words
tectonics, insar, open-access

Sangha, S. S., Govorcin, M., Funning, G. J., & Bekaert, D. (2023, 09). InSAR-derived Vertical Land Motion over southern California: A Scalable Approach leveraging the growing, open-source ARIA-S1-GUNW archive. Poster Presentation at 2023 SCEC Annual Meeting.

Related Projects & Working Groups
Tectonic Geodesy