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Earth Surface and Interior

The Earth Surface and Interior Focus Area promotes the development and application of remote sensing to address the questions:

  • How is the Earth's surface being transformed by naturally occurring tectonic and climatic processes?
  • What are the motions of the Earth's interior, and how do they directly impact our environment?
  • How can our knowledge of earth surface change be used to predict and mitigate natural hazards?

The overarching goal of the focus area is to assess, mitigate and forecast natural hazards that affect society, including such phenomena as earthquakes, landslides, coastal and interior erosion, floods and volcanic eruptions. The path to prediction includes comprehensively recording and understanding the variability of surface changes controlled by two types of forces: external such as climate; and the internal forces that are in turn driven by the dynamics of the Earth's interior. In order to produce a predictive capability, these observations of the Earth's transformation, must be modeled, interpreted, and understood. The advent of spaceborne sensing is vital to forecasting in the solid Earth sciences, providing a truly comprehensive perspective for monitoring the entire solid Earth system. NASA's principal partners in this focus area are the U.S. Geological Survey, the National Geospatial-Intelligence Agency (formerly NIMA), and the National Science Foundation.

Remote sensing empowers scientists to measure and understand subtle changes that reflect the response of the Earth to both the internal forces that lead to volcanic eruptions, earthquakes, landslides, and sea-level change as well as the climatic forces that sculpt the Earth's surface. A key observational strategy is to move towards geodetic and thermal imaging of the precise metrology of Earth's surface and its changes through lidar, radar constellations, and optical arrays. Such imaging coupled with geopotential field measurements will play a primary role in understanding the dynamics of the Earth's surface and interior.

The development of a stable terrestrial reference frame to better than a millimeter per year, the realization of topography and topographic change to sub-meter precision, and an understanding of changes in the Earth's angular momentum and gravity field are critical to accomplishing focus area goals. These data products provide accurate measures of changes in the Earth, including sea-level change, polar mass balance, and land subsidence. Optical and geodetic imaging using radar and lidar define the land surface to sub-meter precision to search for precursory events and to understand the Earth's surface response to both the fluid envelope and interior forces.

Earth Surface and Interior Roadmap
Chart: This Roadmap summarizes the elements of focus area research directed at the critical challenges of understanding the dynamics of Earth's surface and interior as a basis for predicting the occurrence of natural hazards. [+ larger image]

The rate of sea-level change is estimated to be 1-2 mm/yr measured within the terrestrial reference frame. A critical component of these estimates is the response of the solid Earth, including subsidence and erosion in coastal zones and warping of the crust beneath the deepening oceans and thinning ice sheets. Gravity and magnetism are observables not only for the inner dynamics of the Earth but also for understanding the ionosphere, which responds to changes in the Earth's surface such as seismic waves and tsunamis, and can be used as a proxies for surface motions, leading to space-based seismic imaging.

Near-term predictions of volcanic eruptions are moderately successful for certain limited and well-studied volcanic areas. These near-term predictions can be improved through better remote sensing, in particular optical and geodetic imaging coupled with enhanced computational modeling. Substantial challenges remain in modeling debris flow and long-term eruption prediction, which have a significant impact on development in volcanic regions and the global impact of mega-eruptions. Earthquake forecasting requires accurate modeling of fault interactions, which at its heart means understanding the state of stress in the crust and the strength of the lithosphere. Space geodesy is now beginning to give us a glimpse of precursory events, and the integration of geodetic and seismic models is leading to better estimates of crustal strength and dynamics in seismic zones. Visible, infrared and electromagnetic measurements are being studied for evidence of precursory phenomena and a better understanding of the physics of the earthquake cycle.

Modeling, calibration, and validation are essential components in the development of accurate forecasting capabilities. The Solid Earth and Interior Focus Area views natural laboratories as a critical component for the validation and verification of remote sensing algorithms. NASA joins with NSF and USGS in support of the EarthScope initiative to apply modern observational, analytical, and telecommunications technologies to investigate the structure and evolution of the North American continent and the physical processes controlling earthquakes and volcanic eruptions. Other natural laboratories, such as the Asian Pacific Arc and Tien Shan-Caucasus studies of convergent plate boundaries for volcanic and earthquake hazards, are under development in conjunction with international partners. The International Solid Earth Research Virtual Observatory (iSERVO) will link advanced computational resources with distributed databases developed in part from natural laboratories and NASA's remote sensing systems. The objective of iSERVO is accurate forecasting of natural hazards through the implementation of an integrated strategy of observation and computational modeling.