[RSES seminar] Phil Cummins • August 26 1 pm (on zoom)

Prof Louis Moresi


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Earthquake Double-trouble in August, 2021

Phil CumminsResearch School of Earth SciencesAustralian National University
August 26 • 1 pm (AEST)
Seminar will be broadcast on Zoomhttps://anu.zoom.us/my/rses.seminar.room?pwd=NGxUekIranBCQnhQcFdkVC9kSjloZz0 ( ID 606 666 0101, password: jaeger)


During August 2021, the world experienced two remarkable earthquakes: the Mw 8.1 earthquake in the South Sandwich Islands on 12 August, and the Mw 7.2 earthquake in Haiti on 14 August in Haiti. These earthquakes were both exceptional, but for very different reasons.
The Mw 8.1 South Sandwich Islands earthquake was the largest to have occurred in this subduction zone since a Mw 8.1 event in 1929. While we often say that the largest earthquakes occur in subduction zones, this almost always refers to events in ocean-continent or island arc subduction zones, like Cascadia, NE and SW Japan, Indonesia’s Sunda Arc, the Kurils or Aleutians. Even for these subduction zones, we’ve sometimes been wrong about just how big earthquakes can be. But what about oceanic subduction zones, like the Mariana, the Tonga-Kermadec, or South Sandwich, how big can earthquakes in these subduction zones be? We really don’t know, even though the answer has important implications for tsunami hazard worldwide. Perhaps the 2021 South Sandwich earthquake can help answer this question? Then again maybe not…
The Mw 7.2 Haiti earthquake is remarkable for a completely different reason: it was the most deadly natural disaster of 2021. This earthquake occurred on a fault characterised by oblique strike-slip motion, that cuts through the island of Hispaniola in the Caribbean. While earthquakes on such faults are typically much smaller than major subduction zone earthquakes, they can be far more dangerous because that may be proximate to large population centres. This earthquake was significantly larger than a similar earthquake that occurred in Haiti in 2010, which probably caused more than 100,000 fatalities, ranking it as the most deadly natural disaster in the 21st Century (so far). Why did the 2021 earthquake kill so many people, but still far fewer than the 2010 earthquake?
In this talk I will give a brief overview of these two earthquakes, and explain why they are so significant.

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