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Xu, X, Tong X, Sandwell DT, Milliner CWD, Dolan JF, Hollingsworth J, Leprince S, Ayoub F.  2016.  Refining the shallow slip deficit. Geophysical Journal International. 204:1867-1886.   10.1093/gji/ggv563   Abstract

Geodetic slip inversions for three major (Mw > 7) strike-slip earthquakes (1992 Landers, 1999 Hector Mine and 2010 El Mayor–Cucapah) show a 15–60 per cent reduction in slip near the surface (depth < 2 km) relative to the slip at deeper depths (4–6 km). This significant difference between surface coseismic slip and slip at depth has been termed the shallow slip deficit (SSD). The large magnitude of this deficit has been an enigma since it cannot be explained by shallow creep during the interseismic period or by triggered slip from nearby earthquakes. One potential explanation for the SSD is that the previous geodetic inversions lack data coverage close to surface rupture such that the shallow portions of the slip models are poorly resolved and generally underestimated. In this study, we improve the static coseismic slip inversion for these three earthquakes, especially at shallow depths, by: (1) including data capturing the near-fault deformation from optical imagery and SAR azimuth offsets; (2) refining the interferometric synthetic aperture radar processing with non-boxcar phase filtering, model-dependent range corrections, more complete phase unwrapping by SNAPHU (Statistical Non-linear Approach for Phase Unwrapping) assuming a maximum discontinuity and an on-fault correlation mask; (3) using more detailed, geologically constrained fault geometries and (4) incorporating additional campaign global positioning system (GPS) data. The refined slip models result in much smaller SSDs of 3–19 per cent. We suspect that the remaining minor SSD for these earthquakes likely reflects a combination of our elastic model's inability to fully account for near-surface deformation, which will render our estimates of shallow slip minima, and potentially small amounts of interseismic fault creep or triggered slip, which could ‘make up’ a small percentages of the coseismic SSD during the interseismic period. Our results indicate that it is imperative that slip inversions include accurate measurements of near-fault surface deformation to reliably constrain spatial patterns of slip during major strike-slip earthquakes.

Sandwell, DT, Anderson D, Wessel P.  2005.  Plates, plumes, and paradigms. Plates, plumes, and paradigms. ( Foulger GR, Natland JH, Presnall DC, Anderson DL, Eds.).:1-10., Boulder, Colo.: Geological Society of America Abstract
Fialko, Y, Sandwell D, Agnew D, Simons M, Shearer P, Minster B.  2002.  Deformation on nearby faults induced by the 1999 Hector Mine earthquake. Science. 297:1858-1862.   10.1126/science.1074671   AbstractWebsite

Interferometric Synthetic Aperture Radar observations of surface deformation due to the 1999 Hector Mine earthquake reveal motion on several nearby faults of the eastern California shear zone. We document both vertical and horizontal displacements of several millimeters to several centimeters across kilometer-wide zones centered on pre-existing faults. Portions of some faults experienced retrograde (that is, opposite to their long-term geologic slip) motion during or shortly after the earthquake. The observed deformation likely represents elastic response of compliant fault zones to the permanent co-seismic stress changes. The induced fault displacements imply decreases in the effective shear modulus within the kilometer-wide fault zones, indicating that the latter are mechanically distinct from the ambient crustal rocks.

Sandwell, DT, Sichoix L, Agnew D, Bock Y, Minster JB.  2000.  Near real-time radar interferometry of the Mw 7.1 Hector Mine Earthquake. Geophysical Research Letters. 27:3101-3104.   10.1029/1999gl011209   AbstractWebsite

The Hector Mine Earthquake (Mw 7.1, 16 October 1999) ruptured 45 km of previously mapped and unmapped faults in the Mojave Desert. The ERS-2 satellite imaged the Mojave Desert on 15 September and again on 20 October, just 4 days after the earthquake. Using a newly-developed ground station we acquired both passes and were able to form an interferogram within 20 hours of the second overflight. Estimates of slip along the main rupture are 1-2 meters greater than slip derived from geological mapping. The gradient of the interferometric phase reveals an interesting pattern of triggered slip on adjacent faults as well as a 30 mm deep sink hole along Interstate 40.

Maia, M, Ackermand D, Dehghani GA, Gente P, Hekinian R, Naar D, O'Connor J, Perrot K, Morgan JP, Ramillien G, Revillon S, Sabetian A, Sandwell D, Stoffers P.  2000.  The Pacific-Antarctic Ridge-Foundation hotspot interaction: a case study of a ridge approaching a hotspot. Marine Geology. 167:61-84.   10.1016/s0025-3227(00)00023-2   AbstractWebsite

The Foundation hotspot-Pacific-Antarctic Ridge (PAI) system is the best documented case of a fast spreading ridge approaching a hotspot and interacting with it. The morphology, crustal structure inferred from gravity anomalies and the chemical composition of the lavas of the axial area of the PAR show evidence of the influence of the hotspot, that is presently located roughly 35 km west of the spreading ridge axis. Along-axis variation in the Mantle Bouguer anomaly is about 28 mGal, corresponding to a crustal thickening of 1.5 km where the hotspot is nearer to the PAR. Anomalous ridge elevation is 650 m and the along-axis width of the chemical anomaly is 200 km. A comparison of these axial parameters with those derived for other ridge-hotspot systems, suggests that the amount of plume material reaching the ridge axis is smaller for the Foundation-PAR system. This implies a weaker connection between the plume and the ridge. Cumulative effects of a fast spreading rate and of a fast ridge-hotspot relative motion can be responsible for this weak plume-ridge flow. The how from the hotspot may be less efficiently channelled towards the ridge axis when a fast ridge is rapidly moving towards a hotspot. (C) 2000 Elsevier Science B.V. All rights reserved.

Atwater, T, Sclater J, Sandwell D, Severinghaus J, Marlow M.  1993.  Fracture zone traces across the North Pacific Cretaceous Quiet Zone and their tectonic implications. The Mesozoic Pacific : geology, tectonics, and volcanism : a volume in memory of Sy Schlanger. ( Pringle MS, Sager WW, Sliter WV, Stein S, Eds.).:137-154., Washington, DC: American Geophysical Union Abstract
Cheney, RE, Douglas BC, McAdoo DC, Sandwell DT.  1986.  Geodetic and oceanographic applications of satellite altimetry. Space geodesy and geodynamics. ( Anderson A, Cazenave A, Eds.)., London, United Kingdom (GBR): Academic Press, London AbstractWebsite
Sandwell, DT, Agreen RW.  1985.  Seasonal-Variation in Wind-Speed and Sea State from Global Satellite Measurements - Reply. Journal of Geophysical Research-Oceans. 90:5009-5010.   10.1029/JC090iC03p05009   AbstractWebsite
Douglas, BC, Agreen RW, Sandwell DT.  1984.  Observing Global Ocean Circulation with Seasat Altimeter Data. Marine Geodesy. 8:67-83. AbstractWebsite
Sandwell, DT, Agreen RW.  1984.  Seasonal-Variation in Wind-Speed and Sea State from Global Satellite Measurements. Journal of Geophysical Research-Oceans. 89:2041-2051.   10.1029/JC089iC02p02041   AbstractWebsite

The GEOS 3 altimeter, which collected data intermittently for nearly 4 years, has measured significant wave heights and surface wind speeds over most of the world's oceans. Using these data, we have constructed contour maps of spatial variations in sea state and wind speed for winter and summer. To obtain reliable averages in the southern oceans, we low-pass filtered the data using a two-dimensional Gaussian filter with a half width of 600 km. The wind speed maps show that the zonal surface wind patterns, such as the westerlies, the horse latitudes, the trade winds, and the doldrums, shift south by about 10° between winter and summer. As expected, the highest wind speeds and sea states occur during the winter months in the mid-latitudes, 30°–60°. The most striking feature of the maps, however, is the large asymmetry in the summer to winter variation between the two hemispheres. The largest seasonal variations in sea state and wind speed occur in the northern hemisphere oceans and especially in the North Atlantic, where there is almost a factor of 2 variation. In contrast, the summer to winter variation in wind speed and sea state in the southern hemisphere oceans is relatively small. For example, the summer to winter increase in wind speed at 50°S is less than 10%, while at 50°N it is more than 50%. This differing variability can be attributed to the asymmetric distribution of continental area between the two hemispheres and the low effective heat capacity of the continents relative to the oceans.