convert moduli to velocities
    mainly to support Burnman operations

    :param rho: density in kg/m^3
    :param v_phi: adiabatic bulk modulus in Pa
    :param v_s: shear modulus in Pa
    :return: bulk sound speed and shear velocity

def moduli_to_velocities(rho, K_s, G):
    """
    convert moduli to velocities
    mainly to support Burnman operations

    :param rho: density in kg/m^3
    :param v_phi: adiabatic bulk modulus in Pa
    :param v_s: shear modulus in Pa
    :return: bulk sound speed and shear velocity
    """
    return np.sqrt(K_s / rho), np.sqrt(G / rho)