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The shuttle imaging radar C/X synthetic aperture radar (SIR-C/X-SAR) radar on board the space shuttle Endeavor imaged Kilauea Volcano, Hawaii, in April and October 1994 for the purpose of measuring active surface deformation by the methods of repeat-pass differential radar interferometry. Observations at 24 cm (L band) and 5.6 cm (C band) wavelengths were reduced to interferograms showing apparent surface deformation over the 6-month interval and over a succession of 1-day intervals in October. A statistically significant local phase signature in the 6-month interferogram is coincident with the Pu'u O'o lava vent. Interpreted as deformation, the signal implies centimeterscale deflation in an area several kilometers wide surrounding the vent. Peak deflation is roughly 14 cm if the deformation is purely vertical, centered southward of the Pu'u O'o caldera. Delays in the radar signal phase induced by atmospheric refractivity anomalies introduce spurious apparent deformation signatures, at the level of 12 cm peak-to-peak in the radar line-of-sight direction. Though the phase observations are suggestive of the wide-area deformation measured by Global Positioning System (GPS) methods, the atmospheric effects are large enough to limit the interpretation of the result. It is difficult to characterize centimeter-scale deformations spatially distributed over tens of kilometers using differential interferometry without supporting simultaneous, spatially distributed measurements of refractivity along the radar line of sight. Studies of the interferometric correlation of images acquired at different times show that L band is far superior to C band in the vegetated areas, even when the observations are separated by only I day. These results imply longer wavelength instruments are more appropriate for studying surfaces by repeat-pass observations. forms have demonstrated the high level of precision and automation possible for topographic mapping applications afforded by interferometry [Zebker and Goldstein, 1986; Zebker et al., 1992]. Spaceborne radars on the ERS 1 and JERS 1 satellites have been used for surface deformation studies, including coseismic deformation [Massonnet et al., 1993; Zebker et al., 1994b], volcanic deflation [Massonnet et al., 1995], and glacier motion [Goldstein et al., 1993] with millimeter-scale precision.Interferometry requires that the spatial orbital separation, or "baseline," between the two observations be small. This small baseline was achieved using two very different geometries. Six-month temporal separation radar interferometry, which we emphasize in this report, was implemented by repeating some April orbit tracks during the October mission.Interferometric data were also acquired with a 1-day repeat period during the second mission under similar orbital constraints. Six-month interferometry has the potential for surface deformation measurements, while 1-day interferometry can be used for certain topographic mapping, coherence, and glacier motion studies.Preflight uncertainty in orbit knowledg...

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The 8th October 2005 Kashmir Earthquake Mw 7.6 involved primarily thrust motion on a NE‐dipping fault. Sub‐pixel correlation of ENVISAT SAR images gives the location of the 80 km‐long fault trace (within 300–800 m) and a 3D surface displacement field with a sub‐metric accuracy covering the whole epicentral area. The slip distribution inverted using elastic dislocation models indicates that slip occurs mainly in the upper 10 km, between the cities of Muzaffarabad and Balakot. The rupture reached the surface in several places. In the hanging wall, horizontal motions show rotation from pure thrust to oblique right‐lateral motion that are not observed in the footwall. A segmentation of the fault near Muzaffarabad is also suggested. North of the city of Balakot, slip decreases dramatically, but a diffuse zone of mainly vertical surface displacements, which could be post‐seismic, exists further north, where most of the aftershocks occur, aligned along the NW‐SE Indus‐Kohistan Seismic Zone.

Cassini radar observations of Saturn's moon Titan over several years show that its rotational period is changing and is different from its orbital period. The present-day rotation period difference from synchronous spin leads to a shift of approximately 0.36 degrees per year in apparent longitude and is consistent with seasonal exchange of angular momentum between the surface and Titan's dense superrotating atmosphere, but only if Titan's crust is decoupled from the core by an internal water ocean like that on Europa.

The 5–9 March 2011 Kamoamoa fissure eruption along the east rift zone of Kīlauea Volcano, Hawai`i, followed months of pronounced inflation at Kīlauea summit. We examine dike opening during and after the eruption using a comprehensive interferometric synthetic aperture radar (InSAR) data set in combination with continuous GPS data. We solve for distributed dike displacements using a whole Kīlauea model with dilating rift zones and possibly a deep décollement. Modeled surface dike opening increased from nearly 1.5 m to over 2.8 m from the first day to the end of the eruption, in agreement with field observations of surface fracturing. Surface dike opening ceased following the eruption, but subsurface opening in the dike continued into May 2011. Dike volumes increased from 15, to 16, to 21 million cubic meters (MCM) after the first day, eruption end, and 2 months following, respectively. Dike shape is distinctive, with a main limb plunging from the surface to 2–3 km depth in the up‐rift direction toward Kīlauea's summit, and a lesser projection extending in the down‐rift direction toward Pu`u `Ō`ō at 2 km depth. Volume losses beneath Kīlauea summit (1.7 MCM) and Pu`u `Ō`ō (5.6 MCM) crater, relative to dike plus erupted volume (18.3 MCM), yield a dike to source volume ratio of 2.5 that is in the range expected for compressible magma without requiring additional sources. Inflation of Kīlauea's summit in the months before the March 2011 eruption suggests that the Kamoamoa eruption resulted from overpressure of the volcano's magmatic system.

ABSTRACT. The mechanical properties of glacier beds play a fundamental role in regulating the sensitivity of glaciers to environmental forcing across a wide range of timescales. Glaciers are commonly underlain by deformable till whose mechanical properties and influence on ice flow are not well understood but are critical for reliable projections of future glacier states. Using synoptic-scale observations of glacier motion in different seasons to constrain numerical ice flow models, we study the mechanics of the bed beneath Hofsjökull, a land-terminating ice cap in central Iceland. Our results indicate that the bed deforms plastically and weakens following incipient summertime surface melt. Combining the inferred basal shear traction fields with a Coulomb-plastic bed model, we estimate the spatially distributed effective basal water pressure and show that changes in basal water pressure and glacier accelerations are non-local and non-linear. These results motivate an idealized physical model relating mean basal water pressure and basal slip rate wherein the sensitivity of glacier flow to changes in basal water pressure is inversely related to the ice surface slope.