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Earth Surface & Interior

We propose to develop methods to observe surface deformation from slow earthquakes, magmatic intrusions and associated transient processes, and to relate them to the potential for significant natural hazards. Our approach will be to use multiwavelength interferometric synthetic aperture radar, or InSAR, observations, along with GPS and other geodetic data as available, to constrain models of subsurface movements. Our primary focus will be on imaging transient processes, including those that are seismically "silent," and inverting the observed deformations to characterize the causative subsurface structures. Specifically, we will observe, characterize, and model deformation on the island of Hawaii. We choose Hawaii because it is geophysically extremely active and is subject to hazards from earthquakes, eruptions, and local tsunami. Our first effort will be to establish the spatial distribution of long-term, quasi-steady state deformation. Then, we will identify spatially-local episodic events including dike intrusions, magma chamber inflation and deflation events, and silent earthquakes. The latter cause surface deformation similar to earthquakes, but in Hawaii occur over time scales of days. Improved characterization of the structures causing the slow slip events will help clarify their relationship to damaging earthquakes or possible catastrophic flank collapse and tsunami generation. We will use InSAR data from the ALOS, Envisat, and possibly TerraSAR-X satellites, which operate at L-, C-, and X-band wavelengths, respectively. The most robust interferograms derive from the L-band data, but the ALOS satellite samples the ground relatively infrequently - usually only 1-2 interferograms per year are possible. Envisat can produce 10's of interferograms of an area per year, and TerraSAR-X yet more, but decorrelation limits the coverage to unvegetated lava surfaces. Here we will extend spatial coverage using new algorithms we have recently developed based on persistent scattering (PS) analysis. The broad coverage L-band interferograms provide support for PS phase unwrapping, resulting in fairly complete deformation maps at fine temporal sampling, enabling us to characterize rapidly developing processes. Specific products and goals include models of long-term deformation, including slip on various faults and dilation within volcanic magma bodies, from the summit of Mauna Loa and Kilauea as well as along the rift zones. Episodic events such as intrusions will be plainly visible as deviations from the long-term patterns and we will analyze these for dike geometry and changes in magma pressure. While silent earthquakes are presently best detected by GPS, we hope to improve spatial resolution and knowledge of the vertical deformation field with PS-InSAR methods. These deformation maps should better constrain the depth of the slowly slipping faults and the spatial distribution of slow slip. Only by understanding the geometry and properties of the active structures can we evaluate the potential for catastrophic flank collapse, which could lead to devastating tsunami.

Project PI: Howard Zebker/Stanford University

Mitchell Bldg 305, Stanford, CA 94305. (650) 723-2300

Phone: (650)723-8067

Fax: (650)725-7344

Email: zebker@stanford.edu

http://ee.stanford.edu/~zebker/

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Started: Aug 09, 2010

Last Activity: Dec 10, 2010

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