3.7. Amplitude Intensity Measures

imcalculator.get_amplitude_ims(highpass_hz=0.05)[source]

Computes amplitude-based intensity measures.

Peak Ground Acceleration (PGA) is the peak of the record. Peak Ground Velocity (PGV) and Peak Ground Displacement (PGD) are the peaks of the drift-corrected velocity and displacement histories of get_vel_disp_history.

Parameters:

highpass_hz (float or None, optional) – Corner frequency (Hz) of the high-pass filter applied before integration. Default is 0.05 Hz. None integrates the record without drift correction, which inflates PGD (and to a lesser extent PGV) through baseline drift.

Returns:

  • pga (float) – Peak ground acceleration (g).

  • pgv (float) – Peak ground velocity (m/s).

  • pgd (float) – Peak ground displacement (m).

Example

import numpy as np
from openquake.vmtk.imcalculator import imcalculator

acc = np.loadtxt("openquake/vmtk/tests/test_data/acceleration.txt")
im = imcalculator(acc, dt=0.005)

pga, pgv, pgd = im.get_amplitude_ims()
print(f"PGA = {pga:.4f} g,  PGV = {pgv:.4f} m/s,  PGD = {pgd:.4f} m")