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Capturing California’s Crustal Motion with Geodesy

Researchers: Emilie Klein, Yehuda Bock, Xiaohua Xu, David T. Sandwell, Dorian Golriz, Peng Fang and Lina Su, Scripps Institution of Oceanography, University of California, San Diego.

Written by Linda Rowan
16 September 2019


California’s crustal motions due to plate tectonics, earthquakes, volcanoes, water, humans and other factors occur across many time and space scales. Utilizing geodetic observations over decades, a geodynamic model of these motions explores the cause and effect of past movements, creates a current dynamic model and incorporates the influence of new motions as they occur. The model can help to better understand Earth processes and human influence, assess hazards, improve risk resiliency and provide a reference model for surveying, navigation, land use and economic development.


California is on the move. A major plate boundary between the North American and Pacific plates as defined by the San Andreas Fault System runs through most of the state. In northern California, the subducting Juan de Fuca plate causes earthquakes and volcanic growth. Beginning in the 1990s, GPS observations of these motions have recorded 19 significant earthquakes as well as their post-event response. Coastal geology, mountain ranges and hydrological changes can be distinguished from tectonic changes via decades of geodetic observations. As a populated state with large cities, agriculture, energy, mining and major infrastructure, the ground moves due to human activity too, primarily related to water use.

Here the authors combine two decades of GPS data (1999-2018) from nearly a thousand continuously-operating stations in California and Nevada with synthetic aperture radar (SAR) satellite data to determine the many movements of California. The GPS data are tied to a global reference frame, the International Terrestrial Reference Frame of 2014 (ITRF2014).


A dynamic model of California’s movements is developed and will be useful for taking into account future changes and providing improved understanding of Earth processes. The earthquakes during the period of the study caused significant horizontal and vertical motions, especially after the 1999 Mw 7.1 Hector Mine and the 2010 Mw 7.2 El Mayor-Cucapah earthquakes. Human-related subsidence was quantified in the Central and Sacramento Valleys where groundwater use is significant and should be tracked for sustainability. The greater spatial resolution provided by the combination of GPS and InSAR measurements allows us to enhance our understanding of crustal motion and their associated risks. Furthermore, surveying, navigation, infrastructure and economic development are dependent on precise positional awareness in a well-defined reference frame.

Related Links


Klein et al., Transient deformation in California from two decades of GPS displacements: Implications for a three-dimensional kinematic reference frame, J. Geophys. Res., 2019, doi: 10.1029/2018JB017201.


GPS, InSAR, kinematic model, crustal motion

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Last modified: 2020-01-28  22:16:23  America/Denver