Multiseismic cycle deformation rates from Holocene normal fault scarps on Crete (Greece)

Morphotectonic features reveal recent seismic activity on normal faults on Crete allowing slip rates, palaeoearthquake magnitudes and earthquake recurrence intervals to be inferred. The studied faults show major escarpments (100s m high, 10s km long), separating uplifted Mesozoic rocks from Quaternary deposits. During the Holocene, slip rates outpaced erosion/sedimentation rates and 5-15 m high fresh scarps formed at the base of the major escarpments. Based on our field observations and following empirical relationships between magnitude, surface rupture length and maximum co-seismic vertical displacement, it is possible to infer some important seismotectonic parameter relative to the investigated faults. Taking into account the possible sources of error and the corresponding uncertainties, our preferred long-term slip rates range between 0.5 and 1.3 mm yr(-1), the maximum expected magnitudes between 6.3 and 6.6 (or 6.5 and 6.8, considering worst case scenarios), while the mean recurrence intervals range between 260 and c. 840 years. These estimates are in good agreement with the shallow seismicity thus allowing to improve our knowledge on the seismic potential in Crete. Horizontal extension rates could be also inferred from our geological data and compared with the few available GPS data.