  In this letter, we report positive correlations between broad line width and
broad line flux for the broad balmer lines of the long-term observed AGN PG
1613+658. Rather than the expected negative correlations under the widely
accepted virialization assumption for AGN BLRs, the positive correlations
indicate much different BLR structures of PG 1613+658 from the commonly
considered BLR structures which are dominated by the equilibrium between
radiation pressure and gas pressure. Therefore, accretion disk origin is
preferred for the observed broad single-peaked optical balmer lines of PG
1613+658, because of the mainly gravity dominated disk-like BLRs with radial
structures having few effects from radiation pressure.
