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A new time series interferometric synthetic aperture radar method is presented based on a strain model. Traditionally, the interferometric phases are optimized based only on a constant set of statistically homogeneous points throughout the observing period, and thus the decorrelated phase cannot be well recovered and possible incoherent (or coherent) phases are (are not) used to optimize the target phase. In the proposed method, a strain model, representing the geophysical relationship of spatially adjacent points' deformations, is employed to optimize the interferometric phases interferogram‐by‐interferogram. The unwrapped phase time series can be estimated from the wrapped interferograms based on the linear iterative weighted least squares method, which is simple and can effectively suppress the decorrelation noise. Both simulations and analysis of data over The Geysers geothermal field (TG), California are conducted, validating that the proposed method can reduce the decorrelations and simultaneously preserve the deformation signals. The displacement results of TG from 2007–2011 L‐band ascending ALOS‐1 data and 2015–2020 C‐band ascending/descending Sentinel‐1 data reveal that (a) the displacement rate of TG is decreasing from 2007–2011 to 2015–2020, and (b) temporally variable displacement signals in addition to steady displacement can be observed from 2015 to 2020 for both the east‐west and the vertical components. Plain Language Summary: The interferometric synthetic aperture radar (InSAR) technique is capable of accurately measuring ground surface displacements at high spatial resolution and large coverage. This paper proposes a strain‐model based InSAR time series method, here referred to as the SIGMA method. The SIGMA method aims to enhance the capability of InSAR to measure displacements and can achieve higher accuracy and density of InSAR displacement measurements. Both simulations and real‐data experiments are conducted to illuminate the benefits of the SIGMA method in the presence of substantial decorrelation noise. Particularly, the SIGMA method is used to investigate the surface displacements of The Geysers geothermal field, California, during 2007–2011 and 2015–2020. These time periods are complementary to those considered in previous studies, providing an important data set to investigate the long‐term evolution of ground surface deformation, as well as the effects of recent fluid injection and production practices in the geothermal field. The new method should be of value for improved geo‐hazards monitoring. Key Points: A new time series interferometric synthetic aperture radar (InSAR) method based on a strain model and iterative weighted least squares is proposedThe method can effectively suppress decorrelation noise and improves the InSAR accuracy and densityThe surface deformation of The Geysers geothermal field, California is investigated with 2007–2011 ALOS‐1 and 2015–2020 Sentinel‐1 data [ABSTRACT FROM AUTHOR]

Abstract: The spatial–temporal evolution of surface displacement of Los Angeles area over 2003–2007 is measured with weighted least squares (WLS) small baseline (SB) DInSAR technique. 32 small baseline interferograms are generated from 18 SAR images acquired by the ENVISAT satellite and separated into two independent subsets. An additional interferogram with a longer baseline but good interferometric quality is used to link the two subsets. A time series of displacements with their corresponding standard deviations (STD) are derived from the WLS DInSAR solution by considering the interferometric displacement variances when determining the weighting scheme. Both the long-term trends and the seasonal variations of the displacements in the area are determined in the study and validated with GPS measurements from a number of stations of the Southern California Integrated GPS Network (SCIGN). The mean line-of-sight (LOS) displacement velocity map shows up to 3cm/year of ground motion and up to 10cm of accumulated displacements in Santa Fe Springs and −8cm in Pomona over 2003–2007. Seasonal variations are identified in Santa Ana basin, the San Gabriel valley and the Lytle Creek basin, respectively. [Copyright &y& Elsevier]