Raw accelerograms is rarely ready for immediate use. It contains a mixture of the actual ground shaking and various forms of "noise" or errors that must be isolated and addressed. Signal processing is the systematic refinement of ground motion data to ensure it is numerically stable for structural analysis.

Signal processing acts as a filter to separate the seismic signal from unwanted interference. This interference typically falls into two categories:

•High-Frequency Noise: This makes the record look "fuzzy" and can lead to overestimating peak accelerations.

•Low-Frequency Noise (Long-Period):  It results from tilting of the instrument or minor malfunctions. While it looks negligible on an acceleration plot, it causes the calculated velocity and displacement to "drift" or "walk" away from zero.

QuakeManager provides a comprehensive set of signal processing tools to modify and analyze ground motion records. These tools are accessible from the Project Tree or through the Project Toolbar. The only exception is the Pulse Identification tool, which is accessed separately.

Currently, QuakeManager supports the following tools:

•Trimming: Reduce the duration of the record from the start or end

•Resampling: Change the number of points and time steps (dt) of the record

•Padding: Extend records duration from the start or the end

•Fling: Add fling effect to the record’s time history

•Filter Butterworth: Apply a Butterworth filter to the record

•Filter Chebyshev I: Apply a Chebyshev Type I filter

•Filter Chebyshev II: Apply a Chebyshev Type II filter

•Filter Elliptic: Apply an Elliptic (Cauer) filter to the record

•Filter Bessel: Apply a Bessel filter to the record

•Baseline Correction: Remove baseline drift from records

•Composite: perform multiple signal processing operation sequentially.

The signal processing dialog also offers the option to preview changes to time-histories and spectra without running it by enabling “Preview Charts”. By enabling Preview Charts, changes in settings are applied instantly, allowing users to interactively explore the effect of different parameters.

Moreover, a new option has been added to the charts. In addition to “Original” and “Modified”, it is now possible to plot “Previous” as well. The previous is the record coming from the previous step (or the input record if it is the first step) in a multi-step operation (composite filter) if the “Keep Intermediate” option is enabled, otherwise it will be the same as the original.

It should be noted that if the component selected in "Apply to Triplet's" is not found, QuakeManager will skip that record.

Figure: Signal Processing dialog

Figure: Preview option

Copyright © 2026 Earthquake Solutions