Publication Date:
2024-01-09
Description:
This paper explores the paleoseismic record potentially preserved in the upper 40 m of hydraulic piston cores collected in 1996 at two sites in Saanich Inlet, British Columbia, during ocean drilling program (ODP) Leg 169S. The ODP cores are missing 1-2 m of water-rich sediment directly underlying the seafloor, but this sediment is preserved in shorter piston cores collected in 1989 and 1991. The upper part of the ODP cores consists of rhythmically laminated (varved) marine mud with intercalated massive beds, interpreted to be debris flow deposits. Some of the debris flow deposits are linked to past earthquakes, including the 1946 Vancouver Island earthquake (M7.2), a great (M8-9) plate-boundary earthquake at the Cascadia subduction zone in January 1700, and a large crustal or plate-boundary earthquake about 1000 yr ago. Earthquakes may also be responsible for debris flows in about AD 1600, 1500, 1250, 1150, 850, 450, 350, 180, and BC 200, 220, 500, 900, and 1050. If so, the average recurrence interval for moderate to large earthquakes, which trigger debris flows in Saanich Inlet, is about 150 yr. This recurrence interval is broadly consistent with the frequency of moderate to large earthquakes in the region during the historical period. Debris flows, however, can also be triggered by non-seismic processes, making it difficult to assemble a complete earthquake record from the Saanich Inlet cores. We propose that extensive debris flow deposits, emplaced by single large failures or many smaller coincident failures, probably have a seismic origin.
Keywords:
169-1033B; 169-1033C; 169-1033D; 169-1034B; 169-1034C; 169-1034D; 169-1034E; Age, 14C AMS; Age, 14C calibrated; Age, dated; Age, dated material; Age, dated standard deviation; Age, maximum/old; Age, minimum/young; Coastal waters of SE Alaska; Dead Dog vent field, North Pacific Ocean; DEPTH, sediment/rock; DRILL; Drilling/drill rig; DSDP/ODP/IODP sample designation; Event label; Joides Resolution; Leg169S; Number; Ocean Drilling Program; ODP; Sample code/label; Taxon/taxa
Type:
Dataset
Format:
text/tab-separated-values, 529 data points
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