New Initiative Digs Deep, Reaches High

Comprehensive Look at Earth

After several years of planning, a massive new Earth science research initiative is ready to dig deep and take flight to expand the body of knowledge on the Earth's processes.

It's called EarthScope, an ambitious new earthscience initiative designed to dramatically advance understanding of the North American continent by comprehensively exploring its three-dimensional structure, its evolution and its active dynamic processes.

By integrating scientific information derived from geology, seismology, geodesy and remote sensing, EarthScope hopes to yield a comprehensive, time-dependent picture of the continent beyond that which any single discipline can achieve.

Land- and space-based technologies will make it possible for the first time to resolve Earth structure and measure deformation in real-time continental scales, according to Stanford University's Mark Zoback, a member of the EarthScope Facilities Executive Committee.

The four EarthScope components are:

  • The United States Seismic Array.
  • The San Andreas Fault Observatory.
  • The Plate Boundary Observatory.
  • Interferometric Synthetic Aperture Radar (InSAR).

"Each of these components has a separate history, but in 2000 the National Science Foundation hit on the idea to combine the different elements into EarthScope," Zoback said.

The program was developed by the scientific community and the National Science Foundation, in partnership with other science and mission-oriented agencies, including the U.S. Geological Survey and NASA, with links to existing regional networks and state-based agencies.

As with any scientific research, funding was a major hurdle before EarthScope could become a reality, said Zoback.

"The big hurdle was congressional funding, and the earth science community worked hard to push through the initiative," he added. "We can't celebrate yet until we get approval from NSF, but we think it looks good.

"We are on the cusp of changing earth science forever."

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After several years of planning, a massive new Earth science research initiative is ready to dig deep and take flight to expand the body of knowledge on the Earth's processes.

It's called EarthScope, an ambitious new earthscience initiative designed to dramatically advance understanding of the North American continent by comprehensively exploring its three-dimensional structure, its evolution and its active dynamic processes.

By integrating scientific information derived from geology, seismology, geodesy and remote sensing, EarthScope hopes to yield a comprehensive, time-dependent picture of the continent beyond that which any single discipline can achieve.

Land- and space-based technologies will make it possible for the first time to resolve Earth structure and measure deformation in real-time continental scales, according to Stanford University's Mark Zoback, a member of the EarthScope Facilities Executive Committee.

The four EarthScope components are:

  • The United States Seismic Array.
  • The San Andreas Fault Observatory.
  • The Plate Boundary Observatory.
  • Interferometric Synthetic Aperture Radar (InSAR).

"Each of these components has a separate history, but in 2000 the National Science Foundation hit on the idea to combine the different elements into EarthScope," Zoback said.

The program was developed by the scientific community and the National Science Foundation, in partnership with other science and mission-oriented agencies, including the U.S. Geological Survey and NASA, with links to existing regional networks and state-based agencies.

As with any scientific research, funding was a major hurdle before EarthScope could become a reality, said Zoback.

"The big hurdle was congressional funding, and the earth science community worked hard to push through the initiative," he added. "We can't celebrate yet until we get approval from NSF, but we think it looks good.

"We are on the cusp of changing earth science forever."

Critical Areas

The EarthScope program will address scientific targets in a number of critical areas of active research, including:

  • Fault properties and the earthquake process.
  • Fluids and magmas in the crust and upper mantle.
  • Crustal strain transfer.
  • Convergent margin processes.
  • Large-scale continental deformation.
  • Continental structure and evolution.
  • Deep Earth structure.

EarthScope resources will be accessible to the entire scientific and educational communities, Zoback said. Data acquired from the new observational facilities will be transmitted in near real-time to central processing centers where it will be available at no cost to the research community, government agencies, educators and the public and private sectors.

End users also will have online access to software that will aid in data integration, manipulation and visualization.

Numerous factors made EarthScope a reality, Zoback said, including;

  • Development of high-precision instruments capable of being placed in remote locations for extended periods of time.
  • Availability of radio and satellite telemetry that allows remote instruments to communicate directly and constantly with operational support bases.
  • An expanded capability for drilling, sampling and taking measurements in active fault zones, and the ability to instrument these holes to extract key information on the physical conditions within earthquake nucleation zones.
  • Widespread computer networks that bring real-time data to the desktop and are capable of connecting scientists and educators across the country into a united research and educational enterprise.
  • Analytical improvements in geochronology that provide both higher precision and application to a wider age range of events.
  • Expanding data archival systems capable of storing and manipulating huge data streams arriving from large instrument arrays.
  • A mature national infrastructure of Earth science organizations and consortia that have developed extensive experience in managing facilities similar to those in EarthScope.

A Better Understanding

The EarthScope facilities will use these new techniques, approaches and data technologies to provide a framework for broad, integrated studies across the Earth sciences. The USArray, SAFOD and PBO observational systems will offer direct observations of the spatial distribution and evolution of plate boundary deformation, the space time pattern of earthquake occurrence, the initiation and rupture sequences of earthquakes and the dynamics of magma rise, intrusion and eruption.

These facilities also will advance the understanding of earthquake and volcano hazards, as well as a number of important problems in continental geodynamics and tectonics. The problems include:

  • Determining the mechanisms of continental formation and breakup.
  • The relationship between crustal tectonic provinces and upper mantle structure.
  • Rheological stratification and lateral heterogeneity in the lithosphere.
  • Role of fluids in the crust.
  • Intraplate stress distribution and its relationship to modern structures and seismicity.
  • Development of dynamic topography.
  • Feedbacks between surface and tectonic processes.

"This is an exciting time for the Earth sciences," Zoback said. "This project promises to provide a wealth of knowledge that can advance our science dramatically."

Organization

Regarding implementation, operation and maintenance of EarthScope's facilities, Zoback said USArray, PBO and SAFOD facilities will be under the direction of three community-based organizations:

  • The IRIS Consortium.
  • UNAVACO Inc.
  • Stanford/USGS.

An EarthScope facilities office, however — including a facilities executive committee and facilities project director — will serve as the primary operational point of contact with NSF and the user community for the entire project, noted Zoback, who is a member of the EarthScope Facilities Executive Committee. The office will coordinate the component facilities and interact with NSF to ensure that EarthScope remains in compliance with NSF policies and procedures, and is on-track and on budget.

The office also will work closely with a second committee, the EarthScope Science and Education Committee, which will comprise representatives from the Earth science community at large. This committee will foster science integration, education and outreach to ensure that the EarthScope facilities remain responsive to the evolving needs of the research community, he said.

In addition, Zoback said, NSF will appoint an EarthScope program manager as well as a new assistant director to oversee all of NSF's large-scale facilities (which will include EarthScope).

"Exactly how the EarthScope committees will interface with NSF's two-line manager approach to EarthScope will have to be defined," he said, "but those things will work themselves out as we move forward with the project."

EarthScope's Four Components

Each of EarthScope's four components will provide important new information to the overall earth science community.

  • The USArray will dramatically improve the resolution of seismic images of the continental lithosphere and deeper mantle. Scientists will integrate these images with a multitude of geologic data to address significant unresolved issues of continental structure, evolution and dynamics.

The USArray comprises a transportable telemetered array of 400 broadband seismometers designed to provide real time data from a regular grid, with dense and uniform station spacing of 70 kilometers and an aperture of 1,400 kilometers.

The transportable array will roll across the country with one- to two-year deployments at each site; multiple deployments will cover the entire continental United States over a period of eight to 10 years. When completed, this will provide coverage for 3-D imaging from over 2,000 seismograph stations.

While the initial focus of USArray is coverage within the United States, extensions of the array into neighboring countries and onto the continental margins in collaboration with scientists from Canada, Mexico and the ocean science community would be natural additions to the initiative, according to the EarthScope proposal.

An important second element of USArray is a pool of more than 2,400 portable instruments that are a mix of broadband, short period and high-frequency sensors that can be deployed using flexible source-receiver geometries. These instruments will use both natural and explosive sources, and will allow for high-density, shorter-term observations within the footprint of the larger transportable array.

The USArray also will include 40 permanent stations in an augmentation of the National Seismic Network operated by the USGS. Relatively dense, high-quality observations from a continental network of about 130 stations, with uniform spacing of 300 to 350 kilometers, is important for:

  • Tomographic imaging of deep earth structure.
  • Providing a platform for continuous long-term observations.
  • Establishing fixed reference points for calibration of the transportable array.
  • SAFOD is a project designed to directly monitor a creeping and seismically active fault zone at depth to sample fault zone materials and to measure a wide variety of fault-zone properties.

A four-kilometer deep hole will be drilled through the San Andreas fault zone close to the hypocenter of the 1966 M-6 Parkfield earthquake, where the San Andreas fault slips through a combination of small to moderate magnitude earthquakes and aseismic creep.

SAFOD will provide new insights into the composition and physical properties of fault zone materials at depth and the dynamics that govern fault behavior. It also will provide direct knowledge of the stress conditions under which earthquakes initiate and propagate.

In addition to retrieval of fault zone rock and fluids for laboratory analyses, intensive downhole geophysical measurements and long-term monitoring are planned within and adjacent to the active fault zone.

Observatory-mode monitoring activities will include near-field, wide-dynamic-range seismological observations of earthquake nucleation and rupture and continuous monitoring of pore pressure, temperature and strain during the earthquake cycle.

  • The Plate Boundary Observatory is a geodetic observatory designed to study the three-dimensional strain field resulting from plate boundary deformation. This requires that plate boundary deformation be adequately characterized over the maximum ranges of spatial and temporal scales common to active continental tectonic processes.

The geodetic instrumentation must provide:

  • Sufficient coverage of the plate boundary zones so as to capture the secular tectonic component.
  • Appropriate station density for detecting localized phenomena.
  • The necessary bandwidth — hours to decades — to detect plausible transient phenomena ranging from fast and slow earthquakes to interseismic strain buildup and post-seismic viscoelastic relaxation.

A continuously recording, telemetered strain observatory will be installed along the Pacific/North American plate boundary, building upon and greatly expanding the capabilities of specialized geodetic networks already in place.

PBO will consist of four elements:

  1. A network of GPS receivers to provide a long-wavelength, long-period synoptic view of the entire plate boundary. The network will extend from Alaska to Mexico and from the West Coast to the eastern edge of the North American Cordillera.

    Receiver spacing will be about 200 kilometers and the data will be integrated with InSAR, when and where it is available, to define the regional component of the strain field.

  2. Focused dense deployments of GPS receivers in tectonically active areas, such as along the San Andreas Fault systems and around young magmatic systems. These areas require the greatest temporal resolution, so integrated networks of borehole strainmeters and GPS receivers will be deployed around these features.

    On the order of 1,000 observing sites will be needed to cover the most active tectonic regions.

  3. A pool of 100 portable GPS receivers for temporary deployment for dense coverage of areas not sufficiently covered by continuous GPS.

    These systems will provide observations in unmonitored regions and provide a rapid response capability to detect strain transients following earthquakes and volcanic eruptions.

  4. Establishing a national center for the storage and retrieval of digital imagery and geochronological facilities to support geologic and paleoseismic studies in PBO.
  • Although not included in the request for MREFC support, the Interferometic Synthetic Aperture Radar (InSAR) satellite mission would provide spatially continuous strain measurements over wide geographic areas. Plans are under way to develop a dedicated InSAR mission as an integral part of the EarthScope Observatory.

InSAR would allow scientists to:

  • Map surface displacements before, during and after earthquakes or volcanic eruptions.
  • Image the time evolution of geologic systems, provide insights into the mechanics of fault loading and earthquake rupture.
  • Map strain accumulation across broad tectonic zones, potentially highlighting zones of strain concentration.
  • Provide insight into the sources, migration and dynamics of magma movement through a volcanic system that may lead to an eruption.
  • Improve understanding of the rheology of the crust and upper mantle.
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