Structural and geomorphological constraints on the activity of the Sparta Fault (Greece)

The ancient city of Sparti (Greece) suffered extensive damage from a M w ∼7.2 earthquake in 464 B.C.E. resulting in ∼ 20,000 fatalities, but questions remain on the short (∼10 4 yrs) and long-term (10 5 – 10 6 yrs) activity of this important structure. This paper presents new structural data and fluvial geomorphologic analysis from the Sparta Fault, and in particular considers the northern fault segment that is less well known. A new topographic profile on the well-developed post-glacial fault scarp from the northern strand indicates a 7.53 m offset over the last ∼15 ka, suggesting a throw rate of ∼0.5 mm/yr. The longitudinal profiles of rivers flowing across the fault allow elucidation of longer-term fault activity. Along the strike of the fault rivers exhibit up to two slope-break knickpoints, which decrease in height from south to north. These knickpoints are interpreted to have formed owing to the initiation of faulting and a subsequent slip-rate acceleration. The post-glacial fault scarp and fluvial geomorphology both indicate that entire fault is active and has an asymmetrical throw profile that results in the highest slip-rate in the south.