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The 2021 South Sandwich Island Mw 8.2 earthquake: a slow event sandwiched between regular ruptures
  • Zhe Jia,
  • Zhongwen Zhan,
  • Hiroo Kanamori
Zhe Jia
California Institute of Technology

Corresponding Author:[email protected]

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Zhongwen Zhan
California Institute of Technology
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Hiroo Kanamori
California Institute of Technology
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Abstract

We determined the rupture sequence of the Aug 12, 2021 Mw 8.2 South Sandwich Island earthquake which, according to the reports from the National Earthquake Information Center, appears to be a complex sequence in both time and space. Notable tsunamis were recorded by tide gauges at global distances. Given the complexity of this event, we used a multiple subevent inversion method that can accommodate complex variations of fault geometry, location, depth, and temporal characteristics of the event. We found that the rupture initiated as a regular deep thrust earthquake; it then triggered a shallow dominantly slow subevent extending ~200 km to the south, and ended with 2 other regular subevents. The total duration is ~260s, unusually long for an Mw 8.2 event. Our result is qualitatively consistent with other moment tensor solutions and the observed mB-Mw and MS-Mw relations, and provides a more quantitative space-temporal pattern of this unusual sequence.
16 Feb 2022Published in Geophysical Research Letters volume 49 issue 3. 10.1029/2021GL097104