Abstract
We present an upgraded processing scheme (eBASCO, extended BASeline COrrection) to remove the baseline of strong-motion records by means of a piece-wise linear detrending of the velocity time history. Differently from standard processing schemes, eBASCO does not apply any filtering to remove the low-frequency content of the signal. This approach preserves both the long-period near-source ground-motion, featured by one-side pulse in the velocity trace, and the offset at the end of the displacement trace (fling-step). The software is suitable for a rapid identification of fling-containing waveforms within large strong-motion datasets. The ground displacement of about 600 three-component near-source waveforms has been recovered with the aim of (1) extensively testing the eBASCO capability to capture the long-period content of near-source records, and (2) compiling a qualified strong-motion flat-file useful to calibrate attenuation models for peak ground displacement (PGD), 5% damped displacement response spectra (DS), and permanent displacement amplitude (PD). The results provide a more accurate estimate of ground motions that can be adopted for different engineering purposes, such as performance-based seismic design of structures.
Highlights
IntroductionStrong ground-motion records are affected by high- and low-frequency noise as well as by non-standard errors (e.g., spurious spikes, multiple baselines, etc.), so that data processing is always necessary to be able to employ such recordings in any engineering analysis
Strong ground-motion records are affected by high- and low-frequency noise as well as by non-standard errors, so that data processing is always necessary to be able to employ such recordings in any engineering analysis
While directivity effects are usually fully recovered by conventional processing schemes, the accurate recovery of the flying is made difficult by the presence of noise and baseline offsets that, small in acceleration, lead to artificial long period drifts in the displacement trace [9,10,11,12,13] (Figure 1)
Summary
Strong ground-motion records are affected by high- and low-frequency noise as well as by non-standard errors (e.g., spurious spikes, multiple baselines, etc.), so that data processing is always necessary to be able to employ such recordings in any engineering analysis. Near-source ground motion may be affected by two different effects, which can lead to large and long period pulses: rupture directivity and tectonic fling The former produces short-duration and large-amplitude twoside pulses in the velocity trace along the fault-normal direction; the latter is the expression of the permanent tectonic offset of a rupturing fault and it is usually characterized by a one-side pulse in the velocity trace and by a non-zero final displacement along the slip direction (e.g., [7,8,9]). While directivity effects are usually fully recovered by conventional processing schemes, the accurate recovery of the flying is made difficult by the presence of noise and baseline offsets that, small in acceleration, lead to artificial long period drifts in the displacement trace [9,10,11,12,13] (Figure 1)
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