首页|Multi-millennia slip rate relationships between closely spaced across-strike faults: Temporal earthquake clustering of the Skinos and Pisia Faults, Greece, from in situ 36 Cl cosmogenic exposure dating
Multi-millennia slip rate relationships between closely spaced across-strike faults: Temporal earthquake clustering of the Skinos and Pisia Faults, Greece, from in situ 36 Cl cosmogenic exposure dating
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NETL
NSTL
Elsevier
This study investigates slip behaviour on overlapping, en echelon normal faults by analysing the slip histories of the Skinos and Pisia active normal faults over the past similar to 20 kyrs using in situ Cl-36 cosmogenic dating. New Cl-36 data from the Skinos Fault and published Pisia Fault Cl-36 data were modelled, with both sample sites located within an overlap zone and separated by an across-strike distance of 1-2 km. Our analysis reveals fluctuating slip rates, with the two faults alternating between out-of-phase and simultaneous slip. The Pisia Fault exhibited a slip rate of similar to 0.5-0.75 mm/yr from similar to 20 ka to similar to 9.6 ka, increasing to similar to 1.25 mm/yr until similar to 5.2 ka. It then slowed to similar to 0.25 mm/yr or less until similar to 2.0 ka, before accelerating again to similar to 1.25-1.5 mm/yr to the present day. The Skinos Fault maintained a low slip rate of similar to 0.25 mm/yr or less from similar to 20 ka to similar to 6.4 ka, before accelerating to similar to 2.0-3.0 mm/yr, persisting to similar to 1.0 ka or possibly the present-day. Comparing their slip histories, the faults show periods of simultaneous slip between similar to 6.4 ka to similar to 5.2 ka and similar to 2.0 ka to similar to 1.0-0.0 ka, and out-of-phase slip occurred between similar to 9.6 ka and similar to 6.4 ka, and from similar to 5.2 ka to similar to 2.0 ka. Out-of-phase behaviour on faults across strike has now been observed on faults spaced across-strike at distances of 1-2 km, 10-20 km, and similar to 100 km, raising the question of why it occurs. Possible mechanism(s), including rheological fluctuations within fault/shear-zone structures linked between the brittle upper crust and viscous lower crust and stress interactions, are discussed to explain the out-of-phase and simultaneous slip behaviour.
NETL
NSTL
Elsevier
