The USArray component of the NSF-funded EarthScope project ended its observational period in September 2021 and all remaining close-out tasks concluded in March 2022. Hundreds of seismic stations were transferred to other operators and continue to collect scientific observations. This website is now in an archival state and will no longer be updated. To learn more about this project and the science it continues to enable, please view publications here: and citations of the Transportable Array network DOI 10.7914/SN/TA.

To further advance geophysics support for the geophysics community, UNAVCO and IRIS are merging. The merged organization will be called EarthScope Consortium. As our science becomes more convergent, there is benefit to examining how we can support research and education as a single organization to conduct and advance cutting-edge geophysics. See our Joining Forces website for more information. The site will soon host the new EarthScope Consortium website.

A Continental-scale Seismic Observatory

0522 SNEP

Sierra Nevada EarthScope Project (SNEP)

Principal Investigators and Institutions:

Station Map

T. Owens, University of South Carolina

Craig Jones, University of Colorado

Hirsh Gilbert, Purdue

George Zandt, University of Arizona

Funding Source:

NSF EarthScope

Field Dates: 

5/2005 – 9/2007

Equipment Used:

44 broadband stations 

Data Status:

Archive Complete

Network Code:


244,540 MB BB data  


This is an investigation of the deep structure of the Sierra Nevada mountain range in Eastern California. The scientific goals of this experiment include identifying the existence of high density crust and mantle material that may have recently foundered, or delaminated, from the overlying crustal material. This will constrain major hypotheses regarding the evolution of the continental lithosphere. If material has foundered, the constraints that we develop about the deep earth structure, through analysis of seismic waves and wave speeds, will be important information in the development of models to explain the physical and chemical consequences of this process.

The REPORT OF THE ADVISORY COMMITTEE FOR GPRA PERFORMANCE ASSESSMENT FY 2007 highlighted SNEP as the significant earth science highlight in the NSF's goal of improving research infrastructure: "Imaging of a Foundering Lithosphere (0454524; 0454535; 0454554) Drs. Hersh Gilbert of Purdue University, Craig Jones of University of Colorado, Tom Owens of University of South Carolina, and George Zandt of University of Arizona analyzed NSF's EarthScope seismic data to identify a region where the mantle lithosphere is currently being stripped from beneath the Sierra Nevada batholith. As our understanding of processes related to the removal of mantle lithosphere improves, the important role played by lithospheric removal in continental deformation becomes increasingly apparent. Along the central portion of the western foothills of the Sierra, small earthquakes occur deep within the crust. These events may result from stresses associated with the lithospheric removal process. Resolution of EarthScope data has allowed a significant advance in understanding of the tectonics of mountain building and plate interactions. "

Publications/ Abstracts

*  Gilbert, H., C. Jones, T. J. Owens, G. Zandt, Imaging Sierra Nevada lithospheric sinking, EOS, 88 (21), pp. 225 & 229, 22 May, 2007.

    * Jones, C. H., H. Gilbert, G. Zandt, T. Owens, The Sierra Nevada EarthScope Project: A first report from the broadband FlexArray, IRIS Newsletter, 2006 volume, issue 3, pp. 12-14. (small or large pdf version of full newsletter from IRIS)

*  Frassetto, A., H. Gilbert, G. Zandt, T. J. Owens, and C. Jones, Seismic character of the crust and upper mantle beneath the Sierra Nevada, Eos Trans. AGU, 89(53), Fall Meet. Suppl., Abstract S32B-05, 11:20 am

    * H. Reeg., C. H. Jones, H. Gilbert, T. J. Owens, and G. Zandt, Tomographic observations connecting convective downwellings with lithospheric source regions, Sierra Nevada, California, Eos Trans. AGU, 89(53), Fall Meet. Suppl., Abstract S32B-06.11:35 am

    * T. J. Owens, I. D. Bastow, N. Badger, G. Zandt, C. Jones, and H. Gilbert, Shear wave anisotropy beneath the Sierra Nevada: Implications for lithospheric foundering and mantle flow, Eos Trans. AGU, 89(53), Fall Meet. Suppl., Abstract S33B-1956 , PM poster

    * Ryan, J. C., A. Frassetto, O. Hurd, G. Zandt, H. Gilbert, T. Owens, and C. Jones, Focal Mechanisms for Deep Crustal Earthquakes in the Central Foothills and Near Yosemite National Park in the Sierra Nevada, California, Eos Trans. AGU, 89(53), Fall Meet. Suppl., Abstract S33B-1957, PM poster

    * Levandowski, W., H. Reeg, C. H. Jones, G. Zandt, T. J. Owens, and H. Gilbert, Constraints on lithology of downwelling lithosphere from the Sierra Nevada, California, Eos Trans. AGU, 89(53), Fall Meet. Suppl., Abstract U51B-0044, AM poster

    * Gilbert, H., Y. Yang, D. W. Forsyth, C. H. Jones, T. J. Owens, and G. Zandt, Bounds of foundering in the southern Sierra Nevada, Eos Trans. AGU, 89(53), Fall Meet. Suppl., Abstract U54A-04, 4:45 pm