  The routinely flaring events from \sgras\ trace dynamic, high-energy
processes in the immediate vicinity of the supermassive black hole. We
statistically study temporal and spectral properties, as well as fluence and
duration distributions, of the flares detected by the \chandra\ X-ray
Observatory from 1999 to 2012. The detection incompleteness and bias are
carefully accounted for in determining these distributions. We find that the
fluence distribution can be well characterized by a power-law with a slope of
$1.73^{+0.20}_{-0.19}$, while the durations ($\tau$ in seconds) by a log-normal
function with a mean $\log(\tau)=3.39^{+0.27}_{-0.24}$ and an intrinsic
dispersion $\sigma=0.28^{+0.08}_{-0.06}$. No significant correlation between
the fluence and duration is detected. The apparent positive correlation, as
reported previously, is mainly due to the detection bias (i.e., weak flares can
be detected only when their durations are short). These results indicate that
the simple self-organized criticality model has difficulties in explaining
these flares. We further find that bright flares usually have asymmetric
lightcurves with no statistically evident difference/preference between the
rising and decaying phases in terms of their spectral/timing properties. Our
spectral analysis shows that although a power-law model with a photon index of
$2.0\pm0.4$ gives a satisfactory fit to the joint spectra of strong and weak
flares, there is weak evidence for a softer spectrum of weaker flares. This
work demonstrates the potential to use statistical properties of X-ray flares
to probe their trigger and emission mechanisms, as well as the radiation
propagation around the black hole.
