The discussion centers around the M 7.3 earthquake that occurred 174 km NE of Gisborne, New Zealand, on March 4, 2021, at a depth of 20.8 km. Following this event, multiple aftershocks were recorded, including a significant M 8.1 quake in the Kermadec Islands. Participants explored the relationship between underwater landslides and tsunami generation, emphasizing that both fault slips and landslides can displace water and create tsunamis. The conversation also highlighted the importance of seismic signatures in understanding the nature of these events.
PREREQUISITESSeismologists, geologists, disaster response professionals, and anyone interested in understanding earthquake dynamics and tsunami risks.
That raises an interesting question. Often tsunamis are caused by sea bottom landslides. Is there anything in the seismic signature that might make it possible to say that the evens was a landslide rather than a fault slip?jedishrfu said:
Counter question: can a landslide occur if the depth is significantly under sea level? Or is it the nature of the various faults which determine which of it can happen? Or both of it?anorlunda said:
A tsunami warning was issued, but has since been cancelled.jedishrfu said:
The same can happen completely under water. If an earthquake makes one side of the fault drop for, say 10 meters within seconds, then imagine what will happen to, say 1000 meters of water above it? The 2004 tsunami was such an example:hutchphd said:
I guess I am caught in a semantic trap of my own making. If the Earth upon which I stand were to subside suddenly by 10 meters I would not call it a landslide. The physics is clear for an underwater subsidence. Semantics.fresh_42 said:
The choice of words is personal. But this video from Geoscience Australia depicts what we're talking about.hutchphd said:
A landslide is a mass of Earth moving under gravity, and the displacement of Earth (acting under the body force, mg) imparts momentum to the water it displaces. The momentum is transmitted through water and when it comes to a boundary (e.g., land along the coast) the pressure wave is carried onto the land.hutchphd said:
M 8.1 - Kermadec Islands, New ZealandBaluncore said:
no, it's not odd nor unusual. both either stuff sliding into the ocean or an underwater slide ... you can get tsunamis from eitherhutchphd said:
Astronuc said:
I've noticed that. I was wondering about increased activity between Tonga and Fiji, and it seems three quakes of Mag 4+ in the last 24 hours. It's been relatively quiet there until yesterday. Let's see if activity picks up.davenn said:
Some activity has picked up in the Tonga-Fiji region, includingAstronuc said:
I noticed that as well.davenn said:
Astronuc said:
Yup, the aftershocks continue for both sitesAstronuc said:
