Poster Number 195
See more from this Division: Topical Sessions
See more from this Session: Oceanic Geohazards: Distribution, Controls, and Risks (Posters)
Abstract:
We reexamined the observation that large eqs are associated with excess sediment subduction. Improved databases of sediment thickness and its lateral continuity, and occurrence of megathrust earthquakes support Ruff's conjecture. We observe the occurrence at sediment-dominated SZs of:
48 % of all eqs = to/>Mw 7.5 (36 of 75)
43 % of all eqs = to/>Mw 8.0 (18 of 42)
45 % of all eqs = to/>Mw 8.2 (13 of 29)
63 % of all eqs = to/>Mw 8.5 (10 of 16)
67 % of all eqs = to/>Mw 9.0 (4 of 6)
100 % of all eqs = to/>Mw 9.1 (3 of 3).
Key to this compilation is a matching of earthquake magnitude to trench fills of >1-1.5 km and along-trench continuity of >200 km. For all eqs great than Mw = 9, the lateral continuity is >750-1000 km. The insertion of a thick, laterally expansive sediment mass into the subduction channel evidently favors rupture prolongation and generation of large megathrust eqs. It is also clear that, except for the largest earthquakes, factors other than sediment ingestion may serve to localize events of Mw = 7.5 to 9.
See more from this Division: Topical Sessions
See more from this Session: Oceanic Geohazards: Distribution, Controls, and Risks (Posters)