Evaluating geochemical evidence of earthquake periodicity, Sparta Fault, Southern Greece
(English)Manuscript (preprint) (Other academic)
Determining prehistoric earthquake periodicity and magnitudes is important for risk assessments in seismically active areas. We evaluate a geochemical method, which has previously been used to identify prehistoric slips on normal fault scarps through an analysis of variations in the concentration of rare earth elements and Y (REE-Y) along vertical transects. Our study object is the Sparta Fault, a normal fault in southern Greece, developed in limestone and previously documented, and dated using 36Cl, to have been last active 464 BC. From geochemical analyses of 39 fault rock samples, we conclude that REE-Y concentrations correlate strongly with the abundance of quartz and possibly other heterogeneities in the fault scarp. Because the sampled fault rock is a protocataclasite, formed at depth, variations in the abundance of quartz are not associated with prehistoric movements along the fault. We therefore conclude that geochemical evidence does not provide a reliable paleoseismic proxy for fault movement. We also present data indicating a co-variation between quartz and 36Cl concentrations, which we suggest requires a re-examination of this widely used application of the cosmogenic nuclide surface exposure dating method.
Paleoseismology, Prehistoric earthquake, Normal fault scarp, Sparta Fault, Greece, Limestone fault rock, Rare earth elements
Geology Physical Geography
Research subject Geology
IdentifiersURN: urn:nbn:se:su:diva-117176OAI: oai:DiVA.org:su-117176DiVA: diva2:811674
FunderSwedish Research Council