Intra-Frame Deformation Model for the Western U.S. versus the epoch-date subnetwork approach

Aubrey Bennett, Yehuda Bock, Lavoisiane Ferreira, Peng Fang, Zhen Liu, Angelyn W. Moore, Joe T. Roberts, Roland Hohensinn, & David T. Sandwell

Submitted September 7, 2025, SCEC Contribution #14873, 2025 SCEC Annual Meeting Poster #TBD

We report on a dynamic intra-frame deformation model (IFDM) for the Western U.S. that separates the interseismic and transient motions (e.g., coseismic, postseismic, slow slip, subsidence) into three-dimensional weekly cumulative displacement grids. With this approach, a user can determine the change in position within the region between any two epochs of time with respect to ‘stable’ North America. This is in contrast to the current epoch-date approach where there is a periodic update of the GNSS network after a set amount of deformation. Here, we compare the implications of both approaches in the state of California by utilizing daily GNSS-derived displacement time series starting in 1999 in ITRF2020 and updated weekly. For the traditional ‘subnetwork’ approach we present a K-Means clustering analysis that differentiates between deformation regimes such as the locked and creeping section of the San Andreas fault. We also analyze the effect of horizontal transients on the ‘subnetworks’ utilizing the IFDM displacement and strain rate grid; examples include the several large strike-slip earthquakes in the region: the 1999 Mw 7.1 Hector Mine, 2010 Mw 7.2 El Mayor-Cucapah, Mw 6.4 & Mw 7.1 2019 Ridgecrest sequence, and the 2024 Mw 7.0 Cape Mendocino. In addition, we present the effects of vertical transients including time-variant subsidence most apparent in hydrological cycles in the Central Valley but also visible in other locations, and uplift due to postseismic deformation. Both the horizontal and vertical transients create variability in the timing of necessary updates of the GNSS network in the traditional ‘subnetwork’ approach. Lastly, we describe two interactive web-based applications, SCIP and MGViz, for reference frame analysis and visualization.

Citation
Bennett, A., Bock, Y., Ferreira, L., Fang, P., Liu, Z., Moore, A. W., Roberts, J. T., Hohensinn, R., & Sandwell, D. T. (2025, 09). Intra-Frame Deformation Model for the Western U.S. versus the epoch-date subnetwork approach. Poster Presentation at 2025 SCEC Annual Meeting.

Related Projects & Working Groups
Tectonic Geodesy