code: def pgv(self, centimeters=False):
          
          if self._pgv is None:
              # Compute transfer function -- only over non-zero frequencies
              mask = ~np.isclose(self.angular_freqs, 0)
              tf = np.zeros_like(mask, dtype=np.complex)
              tf[mask] = 1 / (self.angular_freqs[mask] * 1j)
              if centimeters:
                  self._pgv = GRAVITY * 100 * self.calc_peak(tf)
              else:
                  self._pgv = GRAVITY * self.calc_peak(tf)
          return self._pgv
docs: Peak-ground velocity [m/sec].