Two M7 Earthquakes: Kermadec Islands & Kepulauan Batu, Indonesia

[davenn]

TL;DR Summary

A pair of M7.1 quakes 20 hours and some distance apart ( aka unrelated)

The first one a M7.1 in the Kermadec Isl. region north of New Zealand

M 7.1 - Kermadec Islands, New Zealand​

• 2023-04-24 00:41:55 (UTC)
• 29.968°S 177.826°W
• 43.1 km depth

It was followed by a couple of M5+ and a couple of M4.9 events.
The Fault Plane Solution "beachball" shows a subduction ( thrust) event, typical of this region
where the Pacific Plate is diving under the Australian Plate. with a fault plane angled towards WNW.

The second event, roughly 20 hours later was another M7.1 off the west coast of Sumatera, Indonesia.

M 7.1 - Kepulauan Batu, Indonesia​

• 2023-04-24 20:00:55 (UTC)
• 0.781°S 98.534°E
• 15.5 km depth

It was preceded several days earlier by 3 x M5+ events that could be deemed foreshocks because of their location related to the M7.1.
This event occurred near the southern end of the rupture zone of the 26 Dec 2004 M9 event.

The Fault Plane Solution "beachball" shows a subduction ( thrust) event, again, typical of this region
where the Indo-Australian Plate is diving under the Eurasian Plate. with a fault plane angled towards NE.

 

[Astronuc]

M 7.1 - Kermadec Islands, New Zealand​

https://earthquake.usgs.gov/earthquakes/eventpage/us6000k6mg/executive

• 2023-04-24 00:41:55 (UTC)
• 29.968°S 177.826°W
• 43.1 km depth

​

M 7.1 - 170 km SSE of Teluk Dalam, Indonesia​

https://earthquake.usgs.gov/earthquakes/eventpage/us7000jvl3/executive

• 2023-04-24 20:00:55 (UTC)
• 0.781°S 98.534°E
• 15.5 km depth

Most after shocks with these two seem to be Mag 5 or less. I wonder if there will be similar magnitude quakes in the region.

 

[davenn]

I wonder if there will be similar magnitude quakes in the region.

Both regions are quite active, specially the Kermadec area, which will often produce several M7+ events a year and an M8+ event around every 5 - 10 years

I am sure that there would be some that would argue that the Sumatrian event was an aftershock of the 2004 M9 event. It is in the aftershock zone and the area hasnt really returned to the pre-2004 seismicity levels.

 

[berkeman]

I tried a quick Google search to check on damage and injuries, but it looks like there is nothing significant, right? That would be a good thing. M7 is crazy powerful.

The USGS site links offer a "Did you feel it" section, but it appears to be "Write-Only" where you can enter what you felt, but not read others' responses...

 

[davenn]

I tried a quick Google search to check on damage and injuries, but it looks like there is nothing significant, right? That would be a good thing. M7 is crazy powerful.

Yes, The Kermadec one only has a few islands in the area, main one Raoul Is, an active volcano, frequented by geoscientists and conservation department people

The Sumatra one close enough to 2 large islands Nias and one other and not that far offshore from Sumatra that it would have been widely felt

The USGS site links offer a "Did you feel it" section, but it appears to be "Write-Only" where you can enter what you felt, but not read others' responses...

sadly yeah