  We present an analysis of the 15 February 2011 X-class solar flare,
previously reported to produce the first sunquake in solar cycle 24 (Kosovichev
2011). Using acoustic holography, we confirm the first, and report a second,
weaker, seismic source associated with this flare. We find that the two sources
are located at either end of a sigmoid which indicates the presence of a flux
rope. Contrary to the majority of previously reported sunquakes, the acoustic
emission precedes the peak of major hard X-ray (HXR) sources by several
minutes. Furthermore, the strongest hard X-ray footpoints derived from RHESSI
data are found to be located away from the seismic sources in the flare
ribbons. We account for these discrepancies within the context of a
phenomenological model of a flux rope eruption and accompanying two-ribbon
flare. We propose that the sunquakes are triggered at the footpoints of the
erupting flux rope at the start of the flare impulsive phase and eruption
onset, while the main hard X-ray sources appear later at the footpoints of the
flare loops formed under the rising flux rope. Possible implications of this
scenario for the theoretical interpretation of the forces driving sunquakes are
discussed.
