USArray

USArray
Name	USArray
Caption	Seismic station deployment pattern
Project	EarthScope
Institution	National Science Foundation; managed by Incorporated Research Institutions for Seismology
Country	United States
Start	2007
Status	Ongoing

USArray USArray is a continental-scale seismic observatory program that deployed dense arrays of seismometers across the United States to image lithospheric and mantle structure and monitor seismicity. The project operated as a portable, transportable, and flexible network to support investigations by researchers affiliated with institutions such as Caltech, University of California, Berkeley, Massachusetts Institute of Technology, and Stanford University. Funded and coordinated through initiatives by the National Science Foundation and administered by consortia including Incorporated Research Institutions for Seismology and the University of Washington, USArray produced datasets widely used by scientists at the Scripps Institution of Oceanography, Lamont–Doherty Earth Observatory, and other centers.

Overview

USArray formed one major component of the broader EarthScope program alongside projects like the Plate Boundary Observatory and UNAVCO-related campaigns. It comprised a mobile Transportable Array of temporary broadband seismometers, a flexible Flexible Array for focused experiments, and a Backbone Array of permanent stations coordinated with networks such as Advanced National Seismic System partners. Deployments sampled tectonic provinces including the Pacific Northwest, San Andreas Fault, Rocky Mountains, and the Appalachian Mountains, enabling cross-disciplinary studies involving teams from University of Alaska Fairbanks, University of Arizona, Oregon State University, and University of Colorado Boulder.

History and development

Planning for the initiative began with community workshops held by the National Science Foundation and scientific advisory groups such as the IRIS Consortium and panels convened at venues like Seismological Society of America meetings. The Transportable Array roll-out began in 2007 with an eastward migration strategy informed by prior experiments at the USGS and pilot studies conducted by researchers at Brown University and University of Michigan. Key milestones included integration with the Global Seismographic Network infrastructure, collaborations with state seismic networks such as California Integrated Seismic Network, and extension to Alaska and Hawaii through partnerships with Alaska Earthquake Center and Hawaii Institute of Geophysics and Planetology researchers. The project timeline featured phases of station relocation, upgrades supported by awards from the National Science Foundation, and data archiving commitments with institutions like IRIS.

Instrumentation and network design

The Transportable Array used broadband seismometers, data loggers, and three-component sensors supplied and maintained by vendors and hosted at sites coordinated with landowners and agencies including National Park Service and Bureau of Land Management. Station spacing typically followed a ~70 km grid to achieve resolution across scales comparable to studies at the USArray reference model scale, while Flexible Array deployments exploited dense nodal experiments and temporary arrays inspired by methods from Stanford University and Caltech investigators. The Backbone Array integrated permanent stations equipped with real-time telemetry, GPS timing from systems managed by National Geodetic Survey, and telemetry links to regional operations centers such as USGS National Earthquake Information Center. Instrument calibration, site characterization, and noise analyses drew on expertise at University of Southern California and University of California, Santa Cruz.

Scientific objectives and key findings

Primary objectives included imaging crustal and mantle structure beneath provinces like the Cascadia Subduction Zone, assessing lithospheric deformation across the Basin and Range Province, and resolving seismic anisotropy beneath cratonic regions such as the Canadian Shield margin. Major findings published by investigators at Princeton University, Yale University, and University of Texas at Austin revealed detailed images of mantle upwellings, remnants of ancient subduction, and sedimentary basin architecture beneath metropolitan centers including Los Angeles and Houston. USArray data improved catalogs of seismicity for events in the New Madrid Seismic Zone and refined earthquake source models used by Federal Emergency Management Agency and regional planners. Studies leveraging USArray contributed to advances in ambient noise tomography, receiver function analyses, and body-wave tomography with implications for hazard assessment in areas like Alaska and the Pacific Northwest.

Data management and accessibility

Data stewardship followed community standards with continuous waveform and metadata archived at the IRIS Data Management Center and accessible to researchers at institutions such as University of Oregon and University of Illinois Urbana-Champaign. Data products included event catalogs, station metadata, and derived seismic tomography models distributed under open-data policies promoted by the National Science Foundation. Tools and software packages from groups like SeisComP developers, the ObsPy community, and analysis pipelines maintained by IRIS enabled reproducible workflows for scientists affiliated with Columbia University and international partners including University of Tokyo researchers. Educational subsets and curated collections were prepared for classroom use with contributions from American Geophysical Union workshops.

Collaborations and educational outreach

USArray engaged a wide network of collaborators from academic centers including University of Minnesota, University of New Mexico, Pennsylvania State University, and federal labs such as Los Alamos National Laboratory. Outreach programs involved partnerships with museums like the Smithsonian Institution and K–12 initiatives coordinated by Carnegie Institution for Science-affiliated educators, as well as graduate training through programs at University of Washington and summer schools organized by IRIS and the Seismological Society of America. These efforts produced curricula, citizen-science projects, and public lectures that connected seismic research to stakeholders in states including Montana, Texas, California, and New York.

Category:Seismology