  Active region NOAA 12673 was extremely volatile in 2017 September, producing
many solar flares, including the largest of solar cycle 24, an X9.3 flare of 06
September 2017. It has been reported that this flare produced a number of
sunquakes along the flare ribbon (Sharykin & Kosovichev 2018; Zhao & Chen
2018). We have used co-temporal and co-spatial Helioseismic and Magnetic Imager
(HMI) line-of-sight (LOS) and Swedish 1-m Solar Telescope observations to show
evidence of the chromospheric response to these sunquakes. Analysis of the Ca
II 8542 \AA\space line profiles of the wavefronts revealed that the crests
produced a strong blue asymmetry, whereas the troughs produced at most a very
slight red asymmetry. We used the combined HMI, SST datasets to create
time-distance diagrams and derive the apparent transverse velocity and
acceleration of the response. These velocities ranged from 4.5 km s$^{-1}$ to
29.5 km s$^{-1}$ with a constant acceleration of 8.6 x 10$^{-3}$ km s$^{-2}$.
We employed NICOLE inversions, in addition to the Center-of-Gravity (COG)
method to derive LOS velocities ranging 2.4 km s$^{-1}$ to 3.2 km s$^{-1}$.
Both techniques show that the crests are created by upflows. We believe that
this is the first chromospheric signature of a flare induced sunquake.
