Dear Xing.Wei,
During normal operation, the blade flapwise modes tend to be heavily damped by aerodynamic loads whereas the edgewise modes tend to have little damping. This is readily discussed in the literature e.g. see: nrel.gov/docs/fy07osti/41804.pdf.
The geometric details of the NREL 5-MW blade have been discussed in several forum posts e.g. Structural design of the wind turbine blade - #5 by Jason.Jonkman.
Best regards,