English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

The presence of undesirable dominating signals in geophysical experimentaldata is a challenge in many subfields. One remarkable example is surfacegravimetry, where frequencies from Earth tides correspond to time-seriesfluctuations up to a thousand times larger than the phenomena of majorinterest, such as hydrological gravity effects or co-seismic gravity changes.This work discusses general methods for removal of unwanted dominating signalsby applying them to 8 long-period gravity time-series of the InternationalGeodynamics and Earth Tides Service, equivalent to the acquisition from 8instruments in 5 locations representative of the network. We compare threedifferent conceptual approaches for tide removal: frequency filtering, physicalmodelling and data-based modelling. Each approach reveals a differentlimitation to be considered depending on the intended application. Vestiges oftides remain in the residues for the modelling procedures, whereas the signalwas distorted in different ways by the filtering and data-based procedures. Thelinear techniques employed were power spectral density, spectrogram,cross-correlation and classical harmonics decomposition, while the systemdynamics was analysed by state-space reconstruction and estimation of thelargest Lyapunov exponent. Although the tides could not be completelyeliminated, they were sufficiently reduced to allow observation of geophysicalevents of interest above the $10 \text{ nm s}^{-2}$ level, exemplified by ahydrology-related event of $60 \text{ nm s}^{-2}$. The implementations adoptedfor each conceptual approach are general, so that their principles could beapplied to other kinds of data affected by undesired signals composed mainly byperiodic or quasi-periodic components.

Methods for removal of unwanted signals from gravity time-series: comparison using linear techniques complemented with analysis of system dynamics