def METHOD_NAME(self, R, method=None):
    """
    Peak ground velocity attenuation models
    Parameters
    -----------
    R : pd.Series
        Distance to epicenter (m)
    method : int (optional, default = None, average)
        1 = Yu and Jin (2008) - Rock
        2 = Yu and Jin (2008) - Soil
    Returns
    --------
    A pandas Series with peak ground velocity (m/s)
    """
    R = R/1000 # convert m to km
    if method == 1:
        # Yu and Jin (2008) - Rock
        PGV = np.power(10, -0.848 + 0.775*self.magnitude + -1.834*np.log10(R+17))
    elif method == 2:
        # Yu and Jin (2008) - Soil
        PGV = np.power(10, -0.285 + 0.711*self.magnitude + -1.851*np.log10(R+17))
    else:
        # Average
        PGV = (np.power(10, -0.848 + 0.775*self.magnitude + -1.834*np.log10(R+17)) + \
              np.power(10, -0.285 + 0.711*self.magnitude + -1.851*np.log10(R+17)))/2
    PGV = PGV/100 # convert cm/s to m/s
    return PGV