  The X-class solar flare of October 23, 2012, generated continuum photospheric
emission and a strong helioseismic wave ("sunquake") that points to an
intensive energy release in the dense part of the solar atmosphere. We study
properties of the energy release with high temporal and spatial resolutions,
using photospheric data from the Helioseismic Magnetic Imager (HMI) onboard
Solar Dynamics Observatory (SDO), and hard X-ray observations made by the
Ramaty High-Energy Solar Spectroscopic Imager (RHESSI). For this analysis we
use level-1 HMI data (filtergrams), obtained by scanning the Fe I line
(6731~\AA) with the time cadence of $\sim 3.6$ s and spatial resolution of
$\sim 0.5^{\prime\prime}$ per pixel. It is found that the photospheric
disturbances caused by the flare spatially coincide with the region of hard
X-ray emission, but are delayed by $\lesssim 4$ seconds. This delay is
consistent with predictions of the flare hydrodynamics RADYN models. However,
the models fail to explain the magnitude of variations observed by the HMI. The
data indicate that the photospheric impact and helioseismic wave might be
caused by the electron energy flux substantially higher than that in the
current flare radiative hydrodynamic models.
