• Solid Earth and Natural Hazards Research and Applications NRA
• Crustal Dynamics Project (CDP)
• Dynamics of the Solid Earth (DOSE) Investigation

Solid Earth and Natural Hazards Research and Applications NRA

The Solid Earth and Natural Hazards Research and Applications NASA Research Announcement (NRA) presented an opportunity for researchers to participate in the NASA research and development themes of Solid Earth and Natural Hazards Research and Applications. The research themes aim to develop and use NASA space geodetic and remote sensing technology to improve our understanding of the physical dynamics of the solid earth (including the interaction with atmosphere, ocean and fluid core) and to improve and demonstrate the capability of this technology in the assessment and mitigation of natural hazards.

From: Solid Earth and Natural Hazards Research and Applications NRA, August 1996

Crustal Dynamics Project (CDP)

The scientific objectives of the Crustal Dynamics Project (CDP) developed by the science community and NASA in the late 1970's were to improve our knowledge and understanding of:

• Regional deformation and strain accumulation related to earthquakes at the plate boundary in the western United States
• Contemporary relative plate tectonic motions of the North American, Pacific, South American, Eurasian, Australian, Nazca, and Caribbean plates
• Internal deformation of lithospheric plates away from plate boundaries, with particular emphasis on North America
• Polar motion and variations in Earth rotation and their possible correlation with earthquakes and other geophysical phenomena
• Crustal motion and deformation occuring in other regions of high earthquake activity.

These objectives required the development of global geodetic systems that could measure distances with high accuracy. As a consequence, a major goal of NASA and solid Earth science in the 1970s was the development of satellite laser ranging (SLR) and very long baseline interferometry (VLBI) techniques to accuracy levels that would enable the scientific problems to be addressed. By the late 1970s, confidence in the viability of these measurement techniques justified initiation of an international, global program. This led to the formation of the NASA Crustal Dynamics Project (CDP) in 1979.

During the 1980s, the CDP and its international partners have made measurements of crustal motion between numerous sites around the world. One of the primary results of this work was to show that the current day motion of the major plates is close to the million year average motion vectors developed from geology. In addition, our knowledge of the distribution of crustal deformation occurring at both transform and subduction plate boundaries was significantly increased; and a new international effort was spawned to monitor the rotational dynamics of the Earth with unprecedented accuracy.

Through improvements in the tracking of satellites, our models of the Earth's gravity field and the ocean tides were dramatically improved.

From: Contributions of Space Geodesy to Geodynamics: Crustal Dynamics, Introduction, D.E. Smith and M. Baltuck

Dynamics of the Solid Earth (DOSE) Investigation

NASA's Solid Earth Sciences Branch has identified broad scientific research objectives which require:

• the improvement of our understanding of the interactions of the solid Earth with the oceans, ground water and atmosphere on time scales of hours to millions of years
• the local changes in sea level resulting from changes in the Earth's climatic, hydrologic, and tectonic systems
• the response of the lithosphere to local regional strain and loading and unloading phenomena such as post-seismic and glacial rebound; the evolving landscape as a record of tectonics, volcanism, and climate change during the last two million years
• the motions and deformations of the lithosphere within the plates and across plate boundaries; the evolution of continents and the structure of the lithosphere
• the dynamics of the mantle including the driving mechanisms of plate motion ; the dynamics of the core and the origin of the magnetic field
• the origins and variability of the Earth's gravity field, and
• the rotational dynamics and reference frames of the planet.

A major emphasis in Dynamics of the Solid Earth (DOSE) for the 1990s will be NASA's contribution to the implementation and operation of an international global geophysical network for integrated, comprehensive measurements of many geophysical parameters. This fiducial network incorporates VLBI, SLR, and GPS systems which are operated on a permanent, continuous basis, and which will provide reference geodetic data to which regional studies occupying many sites on a short-term, temporary basis can anchor. Two or more different systems will be co-located at many sites to provide strong reference frame ties, strengthen fiducial control, and allow intercomparison of the techniques. The two components of the system can be briefly characterized:

• Fiducial Laboratories for an International Natural Science Network (FLINN) -- a global permanent network of space geodetic stations with approximately 1000 km spacing which integrate GPS, VLBI, SLR, and LLR technology to monitor plate motion and deformation, to monitor Earth rotation, and to define and maintain a terrestrial reference frame.
• Densely Spaced Geodetic Systems (DSGS) -- temporary or permanent regional and local monitoring networks deployed across tectonically active regions to measure and analyze motion and deformation over a broad range of spatial and temporal scales.

A total of 54 investigations were selected in response to the DOSE NRA.

From: DOSE NRA, December 1990