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The 2021 Antarctic (South Sandwich) Tsunami as Recorded in the North Pacific

Description: 

On 12 August 2021, a major earthquake occurred in the Antarctic sector of the Atlantic Ocean near the South Sandwich Islands. This was a complex event that was initially reported as a magnitude 7.5 at 18:33 UTC at a deep depth of 47 km followed, three minutes later, by a M_w 8.1-8.3 main shock due to rupturing of the shallow subduction zone. The main shock generated a global tsunami that spread throughout the World Ocean, where it was recorded at such remote regions as Kamchatka, the Aleutian Islands, Alaska and British Columbia roughly 17,000 – 18,000 km from the source area. To examine this event, we used data from a number of coastal tide gauges located within these regions, along with data from 14 DART stations in the North Pacific and 9 ONC NEPTUNE cable stations offshore of Vancouver Island. The first tsunami waves arrived at the southern coast of British Columbia (BC) about 23 h after the earthquake and at the northern coast of BC and southeastern Alaska about 1.0-1.5 hours later. Our numerical model simulations of the event based on the known seismic parameters and Okada’s equations agree remarkably well with the open-ocean DART and ONC records, including the recorded tsunami wave amplitudes and periods. This case clearly demonstrates that even highly distant tsunamigenic events with source areas located in remote oceanic regions can reach the coasts of Alaska and British Columbia and be reliably reproduced by the modern numerical models.

Session: Six Decades of Tsunami Science: From the Source of the 1964 Tsunami to Modern Community Preparedness - I

Type: Oral

Date: 5/2/2024

Presentation Time: 02:00 PM (local time)

Presenting Author: Alexander

Student Presenter: No

Invited Presentation: Yes

Authors