There have been several long-term debatable problems in earthquake physics: (1) the strain problem (localized versus non-localized); (2) the stress problem (high versus low); (3) the heat flux problem (high versus low); (4) the stress drop problem (high versus low); (5) the source spectral problem (ω^-2 versus ω^-3); (6) the seismic efficiency problem (high versus low); and (7) the earthquake recurrence problem (timepredictable versus slip-predictable). The studies of the 20 September 1999 M_s 7.6 Chi-Chi, Taiwan, earthquake can be applied to explore these debatable problems.