Strong aftershocks continue after M8.1 earthquake hits South Sandwich Islands region

aftershocks-m8-1-earthquake-south-sandwich-islands-august-2021

A very strong M6.9 earthquake hit South Sandwich Islands region at 11:10 UTC on August 16, 2021, at a depth of 14 km (8.7 miles). This is the strongest of 127 aftershocks registered by the USGS after M7.5 and M8.1 on August 12.

While this intense earthquake sequence is still being analyzed, the current understanding is that M7.51 was a foreshock to M8.12 which took place about 170 seconds later.

The M8.1 earthquake occurred as the result of reverse faulting at a depth of approximately 48 km (30 miles) in the Scotia subduction zone. 

The focal mechanism solution indicates slip occurred on either a steeply dipping fault dipping to the northwest, or on a shallowly dipping plane dipping to the southeast, according to the USGS.3

"The location, depth, mechanism, and magnitude of this earthquake is preliminary and less well constrained than typical events of this size due to interference from the preceding M7.5 foreshock," the USGS said.

In the 24 hours following the M8.1 mainshock, the USGS located 61 aftershocks of M4.5 or greater.

The aftershock sequence during this time frame includes three aftershocks larger than M6 (M6.0, M6.2, and M6.3).

The aftershocks span a trench-parallel distance of about 470 km (290 miles), stretching from the M7.5 foreshock southward to the triple junction between the South America, South Sandwich, and Antarctica plates.

Preliminary locations for a subset of the aftershocks are located east of the trench indicating the potential presence of outer rise earthquakes, which occur as a result of downward flexure of the subducting slab.

From August 12 at 18:35 UTC (M8.1) to 11:52 UTC on August 16, the USGS registered a total of 126 aftershocks – 32 M4 – 5, 90 M5 – 6, and 4 M6 – 7.

Earthquakes in South Sandwich Islands region from August 12 – 16, 2021. Source: USGS. Credit: TW/SAM, Google

References:

1 Very strong M7.5 earthquake hits South Sandwich Islands region – The Watchers

2 Complex earthquake: USGS says M7.5 in South Sandwich Islands was foreshock of M8.1 – The Watchers

3 M8.1 earthquake South Sandwich Islands region on August 12, 2021 – USGS

Featured image credit: TW/SAM, Google

If you value what we do here, open your ad-free account and support our journalism.

Share:

Related articles

Producing content you read on this website takes a lot of time, effort, and hard work. If you value what we do here, select the level of your support and register your account.

Your support makes this project fully self-sustainable and keeps us independent and focused on the content we love to create and share.

All our supporters can browse the website without ads, allowing much faster speeds and a clean interface. Your comments will be instantly approved and you’ll have a direct line of communication with us from within your account dashboard. You can suggest new features and apps and you’ll be able to use them before they go live.

You can choose the level of your support.

Stay kind, vigilant and ready!

$5 /month

  • Ad-free account
  • Instant comments
  • Direct communication
  • New features and apps suggestions
  • Early access to new apps and features

$50 /year

$10 /month

  • Ad-free account
  • Instant comments
  • Direct communication
  • New features and apps suggestions
  • Early access to new apps and features

$100 /year

$25 /month

  • Ad-free account
  • Instant comments
  • Direct communication
  • New features and apps suggestions
  • Early access to new apps and features

$200 /year

You can also support us by sending us a one-off payment using PayPal:

Leave a reply

Your email address will not be published.