On the use of repeat leveling for the determination of vertical land motion: artifacts, aliasing and extrapolation errors

Leveling remains the most precise technique for measuring changes in heights. However, for the purposes of determining vertical land motion (VLM), a time series of repeat leveling measurements is susceptible to artifacts and aliasing that may arise due to systematic errors, seasonal surface fluctuations, motions occurring during a survey, and any inconsistencies in the observation conditions among epochs. Using measurements from 10 repeat leveling surveys conducted twice yearly along a profile spanning ~40 km across the Perth Basin, Western Australia, we describe the observation, processing, and analysis methods required to mitigate these potential error sources. We also demonstrate how these issues may lead to misinterpretation of the VLM derived from repeat leveling and may contribute to discrepancies between geologically inferred rates of ground motion or those derived from other geodetic measurement techniques. Finally, we employ historical (~40‐year‐old) leveling data in order to highlight the errors that can arise when attempting to extrapolate VLM derived from a geodetic time series, particularly in cases where the long‐term motion may be nonlinear

Specifications to support classification, standards of accuracy, and general specifications of geodetic control surveys /

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Uplift of the Western Transverse Ranges and Ventura Area of Southern California: A Four‐Technique Geodetic Study Combining GPS, InSAR, Leveling, and Tide Gauges

We estimate the rate of vertical land motion (VLM) in the region around the Western Transverse Ranges (WTR), Ventura, and Big Bend of the San Andreas Fault (SAF) of southern California using data from four geodetic techniques: GPS, interferometric synthetic aperture radar (InSAR), leveling, and tide gauges. We use a new analysis technique called GPS Imaging to combine the techniques and leverage the synergy between (1) high geographic resolution of InSAR, (2) precision, stability, and geocentric reference frame of GPS, (3) decades long observation of VLM with respect to the sea surface from tide gauges, and (4) relative VLM along dense leveling lines. The uncertainty in the overall rate field is ~1 mm/yr, though some individual techniques have uncertainties as small as 0.2 mm/yr. The most rapid signals are attributable to subsidence in aquifers and groundwater changes. Uplift of the WTR is geographically continuous, adjacent to the SAF and appears related to active crustal contraction across Pacific/North America plate boundary fault system. Uplift of the WTR and San Gabriel Mountains is ~2 mm/yr and is asymmetrically focused west of the SAF, consistent with interseismic strain accumulation across thrust faults in the Ventura area and Santa Barbara channel that accommodate contraction against the near vertical SAF