What caused the recent earthquakes in Taiwan?

[davenn]

TL;DR Summary

Mw6.5 and 6.9 SE Taiwan

Earlier today ( my time) ...

M 6.5 - Taiwan​

• 2022-09-17 13:41:17 (UTC)
• 23.096°N 121.406°E
• 10.0 km depth

this has been followed by a M6.9 ...

M 6.9 - 86 km SE of Lugu, Taiwan​

• 2022-09-18 06:44:14 (UTC)
• 23.159°N 121.316°E
• 10.0 km depth

that is still coming in ( as I type) on my seismograph here in Sydney, Australia

Both events had an oblique slip fault motion ... a mix of strike-slip and thrust

for a brief explanation of moment tensor "beachballs" see this page of mine...
https://www.sydneystormcity.com/fomec.htm

cheers
Dave

 

[berkeman]

Yikes, those are strong. It looks like no causualties so far because of the location. Fingers crossed...

• Train carriages derailed, four rescued from collapsed building
• Tsunami warnings cancelled, chip foundries unaffected
• More than 600 trapped by blocked mountain roads
• Quake follows 6.4 magnitude tremor on Saturday

TAIPEI, Sept 18 (Reuters) - A 6.8 magnitude earthquake hit the sparsely populated southeastern part of Taiwan on Sunday, the island's weather bureau said, derailing train carriages, causing a convenience store to collapse and trapping hundreds on mountain roads.

The weather bureau said the epicentre was in Taitung county, and followed a 6.4 magnitude temblor on Saturday evening in the same area, which caused no casualties. read more

https://www.reuters.com/world/asia-pacific/powerful-earthquake-hits-southeast-taiwan-2022-09-18/

 

[davenn]

OK a couple of maps showing the M4 + events

Originally the M6.5 was the main shock, till the 6.9 occurred. It then became the mainshock
and the 6.5 a large foreshock

Regional map...

zoomed in ...

cheers
Dave