Evaluating the Coupling Between Turbidites and Paleo-Earthquakes over 700 Years in the Southern Okinawa Trough, Taiwan

High-resolution marine sedimentary archives from active continental margins provide exceptional records of paleo-earthquake histories through the preservation of seismogenic turbidites. A 477cm long gravity core (HOBAB4-S2) retrieved from the southern Okinawa Trough (SOT) off eastern Taiwan at a water depth of 1505 m preserves a ~700-year record (1445–2003 AD) of alternating hemipelagic background sedimentation and rapid event deposits. Chronological control is established through accelerator mass spectrometry (AMS 14C) radiocarbon dating and excess 210Pb profiling. Detailed sedimentological and geochemical analyses identify fifteen turbidite events (T1–T15), which are grouped into three lithofacies: TI (silt turbidites), TII (sandy silt turbidites), and TIII (silty sand turbidites). Temporal correlation demonstrates that the majority of these turbidite beds coincide with documented historical and instrumental earthquakes (Mw ≥ 6.6), confirming seismic shaking as the primary triggering mechanism. Notably, turbidite thickness, basal grain size and recurrence frequency increase during the Little Ice Age (LIA, ~1400–1850 AD), a pattern we attribute to enhanced terrestrial sediment supply driven by intensified typhoon activity, which preconditioned the slope system for seismically induced failure. These findings demonstrate that turbidite sequences in the SOT provide a reliable record of local paleo-earthquake activity, while establishing that their stratigraphic expression is modulated by climatically driven sedimentary preconditioning. This principle is critical to paleoseismic reconstruction in seismically active, storm-prone continental margins globally.