Peak-ground velocity [m/sec].

def pgv(self, centimeters=False):
        """Peak-ground velocity [m/sec]."""
        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