Satellite interferometric observations of displacements associated with seasonal groundwater in the Los Angeles basin

[1] The Newport-Inglewood fault zone (NIFZ) displays interferometric synthetic aperture radar (SAR) phase features along most of its length having amplitudes of up to 60 mm. However, interpretation in terms of right-lateral, shallow slip along the fault fails to match the range of geologic estimates of slip. Recently, 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 by the ERS-1 and ERS-2 spacecraft between June 1992 and June 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 one quarter of the way through the year, 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. Since these horizontal signals have peak-to-trough amplitudes of 6 mm, they mask the smaller tectonic signals and need to be taken into account when interpreting GPS time series of site position. Moreover, since the groundwater signal appears to have a long-term vertical trend which varies in sign depending on location, it will be difficult to distinguish interseismic tectonic slip along the NIFZ and within the affected areas in the basin.

[1]  Gerald W. Bawden,et al.  Tectonic contraction across Los Angeles after removal of groundwater pumping effects , 2001, Nature.

[2]  David T. Sandwell,et al.  Topographic phase recovery from stacked ERS interferometry and a low‐resolution digital elevation model , 2000 .

[3]  Yehuda Bock,et al.  Instantaneous geodetic positioning at medium distances with the Global Positioning System , 2000 .

[4]  Fuk K. Li,et al.  Synthetic aperture radar interferometry , 2000, Proceedings of the IEEE.

[5]  Yehuda Bock,et al.  Coseismic deformation associated with the November 1995, MW = 7.1 Nuweiba earthquake, Gulf of Elat (Aqaba), detected by synthetic aperture radar interferometry , 1999 .

[6]  T. Nilsen,et al.  Strike‐slip basins, Part 2 , 1999 .

[7]  Michael B. Heflin,et al.  Shortening and thickening of metropolitan Los Angeles measured and inferred by using geodesy , 1999 .

[8]  D. Sandwell,et al.  Phase gradient approach to stacking interferograms , 1998 .

[9]  Yehuda Bock,et al.  Integrated satellite interferometry: Tropospheric noise, GPS estimates and implications for interferometric synthetic aperture radar products , 1998 .

[10]  David T. Sandwell,et al.  Small‐scale deformations associated with the 1992 Landers, California, earthquake mapped by synthetic aperture radar interferometry phase gradients , 1998 .

[11]  K. Feigl,et al.  Radar interferometry and its application to changes in the Earth's surface , 1998 .

[12]  Kenneth W. Hudnut,et al.  Detection of aquifer system compaction and land subsidence using interferometric synthetic aperture radar, Antelope Valley, Mojave Desert, California , 1998 .

[13]  Y. Bock,et al.  Escape tectonics in the Los Angeles metropolitan region and implications for seismic risk , 1998, Nature.

[14]  P. Visser,et al.  Precise orbit determination and gravity field improvement for the ERS satellites , 1998 .

[15]  Kenneth W. Hudnut,et al.  Southern California Permanent GPS Geodetic Array: Continuous measurements of regional crustal deformation between the 1992 Landers and 1994 Northridge earthquakes , 1997 .

[16]  Yehuda Bock,et al.  Integrated satellite interferometry in Southern California , 1997 .

[17]  L. Grant,et al.  Paleoseismicity of the north branch of the Newport-Inglewood fault zone in Huntington Beach, California, from cone penetrometer test data , 1997, Bulletin of the Seismological Society of America.

[18]  John H. Shaw,et al.  Earthquake hazards of active blind-thrust faults under the central Los Angeles basin , 1996 .

[19]  Susan Y. Schwartz,et al.  Simultaneous inversion for earthquake location and velocity structure beneath central Costa Rica , 1996 .

[20]  Kenneth W. Hudnut,et al.  Co-seismic displacements of the 1994 Northridge, California, earthquake , 1996, Bulletin of the Seismological Society of America.

[21]  K. Sieh,et al.  Prospects for Larger or More Frequent Earthquakes in the Los Angeles Metropolitan Region , 1995, Science.

[22]  Mark D. Petersen,et al.  Fault slip rates and earthquake histories for active faults in southern California , 1994 .

[23]  P. Rosen,et al.  On the derivation of coseismic displacement fields using differential radar interferometry: The Landers earthquake , 1994, Proceedings of IGARSS '94 - 1994 IEEE International Geoscience and Remote Sensing Symposium.

[24]  K. Feigl,et al.  The displacement field of the Landers earthquake mapped by radar interferometry , 1993, Nature.

[25]  C. M. Budwine,et al.  Institute of geophysics and planetary physics , 1991 .

[26]  Thomas L. Davis,et al.  A cross section of the Los Angeles Area: Seismically active fold and thrust belt, The 1987 Whittier Narrows earthquake, and earthquake hazard , 1989 .

[27]  K. Thompson,et al.  Assessment of the Adequacy of the Ground Water Monitoring Program for Artificial Recharge of Aquifers in the Los Angeles Area, California , 1988 .

[28]  E. Hauksson.  Seismotectonics of the Newport-Inglewood fault zone in the Los Angeles basin, southern California , 1987 .

[29]  J. Platt,et al.  Newport-Inglewood Fault Zone, Los Angeles Basin, California: DISCUSSION , 1974 .

[30]  R. E. Wilcox,et al.  Basic Wrench Tectonics , 1973 .

[31]  T. P. Harding.  Newport-Inglewood Trend, California--An Example of Wrenching Style of Deformation , 1973 .

[32]  R. Yeats.  Newport-Inglewood Fault Zone, Los Angeles Basin, California , 1973 .

[33]  M. Hill.  Newport-Inglewood Zone and Mesozoic Subduction, California , 1971 .

[34]  F. E. Kasline.  Fifty-fifth annual report of the state oil and gas supervisor , 1969 .

[35]  R. F. Yerkes,et al.  Geology of the Los Angeles Basin, California: an introduction , 1965 .

[36]  J. F. Poland,et al.  Hydrology of the Long Beach-Santa Ana area, California with special reference to the watertightness of the Newport-Inglewood structural zone, with a section on withdrawal of ground water, 1932-41 , 1959 .

[37]  J. F. Poland,et al.  Ground-water geology of the coastal zone, Long Beach-Santa Ana area, California , 1956 .

[38]  A. A. Garrett,et al.  Native and contaminated ground waters in the Long Beach-Santa Ana area, California , 1953 .