def mblg_to_mw_atkinson_boore_87(mag):
    """
    Convert magnitude value from Mblg to Mw using Atkinson and Boore 1987
    conversion equation.

    Implements equation as in line 1656 in hazgridXnga2.f
    """
    return 2.715 - 0.277 * mag + 0.127 * mag * mag
