Load, process and inspect earthquake ground-motion records without MATLAB. Records and calculations remain in this browser; no record data is uploaded.
Import formats
Use time–acceleration columns, single-column acceleration, row-wise packed acceleration, or PEER AT2 files containing NPTS and DT. Headers before numeric data are allowed. Time columns must have a constant positive step. Time is rebased to zero. For a folder, optional GM Data.txt rows have the form filename dt; a third numeric column, if supplied, is a per-record scale factor. Input unit selection always controls acceleration conversion, including AT2.
Methods
- Trapezoidal integration gives velocity and displacement with zero initial conditions. Optional mean or linear-trend correction is applied to acceleration before integration.
- Arias intensity is π/(2g) ∫a²dt. Duration uses interpolated crossings of normalized cumulative intensity. A zero signal has undefined significant duration.
- The one-sided Fourier amplitude spectrum uses a zero-padded FFT and normalization by the original sample count. No spectral window is applied.
- Incremental velocity integrates |a| between interpolated zero crossings, including record-edge segments.
- FIV₃ follows the MATLAB causal second-order Butterworth filter and discrete rectangular integration window. If fewer than three peaks exist, the available peaks are summed and flagged.
- PSA = ω² max|u| / g, from a linear SDOF oscillator using Newmark average acceleration with substeps no longer than T/20. PGA defines the zero-period ordinate. Sa,avg uses 21 periods, including both interval endpoints.
Differences from the MATLAB source
The MATLAB duration routine integrated acceleration differences squared. This edition integrates acceleration squared, following the Arias intensity definition. The spectrum uses a stable substepped solver and one consistent SI-to-g conversion, correcting the original repeated unit division. Additional zero-acceleration time is included in histories and oscillator response; intensity, FFT and FIV use the original record only.
Using the app
Select or drop records, or generate a harmonic wave. Apply processing, select a record and switch between the eight analysis views. Export the current curve, complete time histories, summaries or a plot image. The plotting library loads from the internet; numerical calculations use no external services.
Velocity and displacement are sensitive to acceleration baseline and record quality. This edition has analytic and sample-record checks; full numerical equivalence to the MATLAB app is intentionally not claimed.
