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King, NE, Argus D, Langbein J, Agnew DC, Bawden G, Dollar RS, Liu Z, Galloway D, Reichard E, Yong A, Webb FH, Bock Y, Stark K, Barseghian D.  2007.  Space geodetic observation of expansion of the San Gabriel Valley, California, aquifer system, during heavy rainfall in winter 2004-2005. Journal of Geophysical Research-Solid Earth. 112   10.1029/2006jb004448   AbstractWebsite

[1] Starting early in 2005, the positions of GPS stations in the San Gabriel valley region of southern California showed statistically significant departures from their previous behavior. Station LONG moved up by about 47 mm, and nearby stations moved away from LONG by about 10 mm. These changes began during an extremely rainy season in southern California and coincided with a 16-m increase in water level at a nearby well in Baldwin Park and a regional uplift detected by interferometric synthetic aperture radar. No equivalent signals were seen in GPS station position time series elsewhere in southern California. Our preferred explanation, supported by the timing and by a hydrologic simulation, is deformation due to recharging of aquifers after near-record rainfall in 2004 - 2005. We cannot rule out an aseismic slip event, but we consider such an event unlikely because it requires slip on multiple faults and predicts other signals that are not observed.

King, NE, Agnew DC, Wyatt F.  1988.  Comparing Strain Events - A Case-Study for the Homestead Valley Earthquakes. Bulletin of the Seismological Society of America. 78:1693-1706. AbstractWebsite
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King, NE, Agnew DC.  1991.  How Large is the Retrograde Annual Wobble. Geophysical Research Letters. 18:1735-1738.   10.1029/91gl01882   AbstractWebsite

We compare recent measurements of polar motion (wobble) made by space-geodetic methods with older optical measurements. Multitaper spectra of these data show that the retrograde (clockwise) annual wobble is much larger in the older data than the newer data, implying systematic errors in the older techniques. Two additional analyses show evidence for a small retrograde motion in the newer data, which appears to be consistent between data types. This implies that the excitation of the retrograde wobble must be about half of the prograde excitation. None of the available estimates of the excitation shows full agreement with these observations.

Knopoff, L, Rydelek PA, Zurn W, Agnew DC.  1989.  Observations of Load Tides at the South-Pole. Physics of the Earth and Planetary Interiors. 54:33-37.   10.1016/0031-9201(89)90184-2   AbstractWebsite

The use of tidal observations to study the ‘nearly diurnal free wobble’ mode of the Earth is possible if oceanic effects in the tidal record are accurately removed. We have analyzed vertical gravity data from the South Pole to determine the amplitude and phase of the small daily and semidaily tides observed at the Pole. Since these signals at the Pole are most probably caused by oceanic tides, our observations provide an excellent target for the oceanic models. A comparison with the best models of the oceans now available indicates the need for improvement in measuring and modeling the southern oceans.