  We analyse the statistical pattern of seismicity before a 1-2 103 m3 chalk
cliff collapse on the Normandie ocean shore, Western France. We show that a
power law acceleration of seismicity rate and energy in both 40 Hz-1.5 kHz and
2 Hz-10kHz frequency range, is defined on 3 order of magnitude, within 2 hours
from the collapse time. Simultaneously, the average size of the seismic events
increases toward the time to failure. These in-situ results are derived from
the only station located within one rupture length distance from the rock fall
rupture plane. They mimic the "critical point" like behavior recovered from
physical and numerical experiments before brittle failures and tertiary creep
failures. Our analysis of this first seismic monitoring data of a cliff
collapse suggests that the thermodynamic phase transition models for failure
may apply for cliff collapse.
