DARTs and CORK in Cascadia Basin: High‐resolution observations of the 2004 Sumatra tsunami in the northeast Pacific

摘要: [1] We report unique deep-sea recordings of the Sumatra tsunami December 2004 by high-resolution DART® (Deep-ocean Assessment and Reporting Tsunami) CORK (Circulation Obviation Retrofit Kit) bottom pressure sensors deployed at depths ∼1500–3500 m in Cascadia Basin northeast Pacific. The simultaneous records from these sites establish first-ever regional-scale detection array for open ocean, enabling us to resolve both seafloor crustal signals determine fundamental properties waves following their 22,000 km journey source region. Waves reaching basin had mean amplitudes ∼5 mm with energy spread over a broad frequency band 0.4 7 cph. Peak was 0.8 2 cph (75 30 min) band. Leading event arrived 34–35 h after earthquake, roughly later than expected, suggesting that mainly propagated “most economic” (minimum loss) path along mid-ocean ridge wave-guides rather taking direct fastest across ocean. Motions within peak comprise 50% coherent progressive propagating south longwave phase speeds ∼150 ms−1 random scattered coast irregularities. Tsunami borehole were one-third those on seafloor. extensive “ringing” anomalously slow (3.5-day) e-folding decay time wave indicates long duration flux radiating Indian Ocean via Southern Pacific Ocean.