The Newport Inglewood Fault Zone (NIFZ) displays interferometric synthetic aperture radar (InSAR) phase features along most of its length having amplitudes of up to 60 mm. Bawden et al. [2001] proposed that these phase features, as well as a broader deformation pattern in the Los Angeles basin, are due to vertical motion related to annual variations in the elevation of the water table. We confirm this hypothesis through the analysis of a longer span of data consisting of 26 SAR images collected between 1992 and 2000. Moreover, we use continuous GPS measurements from 1995 to the present to establish the amplitude and phase of the vertical deformation. The Los Angeles Basin becomes most inflated in March/April, which is consistent with water table measurements as well as with the end of the rainy season when the aquifer should be at a maximum. The spatial pattern of the amplitude of the annual signal derived from continuous GPS measurements is consistent with the shape of the interferometric fringes. GPS sites both near the NIFZ and in a 20 by 40 km zone within the basin also show significant N-S annual variations that may be related to the differential expansion across the fault. These horizontal signals with peak-to-trough amplitudes of 6 mm mask the smaller tectonic signals affecting interpretation of GPS position time series. Moreover, since the ground water signal appears to have a long-term vertical trend, it will be difficult to distinguish interseismic tectonic slip within the affected areas in the basin.

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	Figure 1 Perpendicular baselines for ERS-1 orbit E1-23705, frame 2925, track 170. Pairs used for stacked topographic phase are connected by dashed lines, those used for deformation phases by solid lines.
	Figure 2 Excerpts of remaining interferograms: (a) E1-23705_E2-12048, (b) E2-07539_E2-19563, (c) E2-14553_E1-04824, (d) E1-23204_E2-21567, (e) E2-22068_E2-11547, (f) E1-11337_E1-25208, (g) E1-11838_E2-18060 and (h) E2-14052_E1-07830. Also plotted are the coastline (black) and the NIFZ (white).
	Figure 3 Plot of GPS Up component in mm for SCIGN site HOLP (+) with least squares-fit sinusoidal curve for HOLP overlain (gray curve). Plot of total monthly precipitation (TPCP) in mm for six meteorological stations in the region; lower curves. Plot of ground water surface elevation (WSE) in meters for two stations (locations shown by star in Figures 5 and 7); upper curves. Dashed vertical lines drawn at i.25 years.
	Figure 4 Plot of GPS UP component for SCIGN sites LONG (bigtriangleup), CSN1 (bigtriangledown), LEEP (star), DYHS (square), SACY (diamond), LBC1 (circle) and HOLP (+). The respective least squares-fit sinusoidal curves are overlain. Dashed vertical lines drawn at i.25 years. Note that offsets have been applied to each time series for plot clarity.
	Figure 5 Plot of Up component least squares-fit sinusoidal curve amplitudes > 1.0 mm. Note that amplitudes in mm are shown beside site names, and circle radii scale with amplitude. Wells with time series in Figure 3 shown by star.
	Figure 6 Plot of GPS North component for SCIGN sites LONG (bigtriangleup), CSN1 (bigtriangledown), LEEP (star), DYHS (square), SACY (diamond), LBC1 (circle) and HOLP (+). Dashed vertical lines drawn on all plots at i.25 years. Note that a linear trend has been removed from each of these North time series, and offsets have been applied for plot clarity.
	Figure 7 (a) Plot of North component least squares-fit sinusoidal curve amplitudes > 1.0 mm. Note that amplitudes in mm are shown beside site names, and circle radii scale with amplitude. Wells with time series in Figure 3 shown by star. (b) Plot of East component least squares-fit sinusoidal curve amplitudes > 1.0 mm. Circle radii scale with amplitude. Wells with time series in Figure 3 shown by star.
	Plate 1 Excerpt of interferogram for ERS-1/2 frame 2925, track 170, orbit pair E1-23705_E2-17559. Also plotted are the coastline (black), SCIGN stations (red), 50 meter topographic contours (green) and the NIFZ (yellow).
	Plate 2 Contour plot of Up component least squares-fit sinusoidal curve amplitudes (yellow solid lines) in mm and phase (green dashed lines) in years for the SCIGN sites labeled.