- #1
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M 7.1 Quake Estrn PNG coming in NOW
- Thread starter davenn
- Start date
Click For Summary
Discussion Overview
The discussion revolves around the recent M 7.1 earthquake in Eastern Papua New Guinea, focusing on its depth, amplitude measurements, and the implications for surface effects and potential damage. Participants share seismographic data and explore the characteristics of deep earthquakes.
Discussion Character
- Exploratory
- Technical explanation
- Debate/contested
Main Points Raised
- Some participants report significant amplitude readings on their seismographs, indicating a notable seismic event.
- There is a discussion about the depth of the quake, with some sources reporting it at 133 km, which is considered deep.
- One participant notes that the USGS has upgraded the magnitude to M 7.2, attributing this to the amplitude and depth of the quake.
- Another participant expresses astonishment at the precision of seismic measurements from such distances, mentioning a specific error margin for depth and magnitude.
- Questions are raised about whether deep earthquakes can be felt at the surface and the potential for damage, with some suggesting that while deep quakes can be felt, they are less likely to cause significant damage compared to shallow quakes.
- Participants discuss the behavior of surface waves and their relation to depth, indicating that surface waves are stronger in shallow events.
Areas of Agreement / Disagreement
Participants generally agree on the depth and magnitude of the earthquake, but there is ongoing debate about the potential for surface effects and damage, with differing views on how deep quakes are felt.
Contextual Notes
Limitations include the dependence on various seismic measurement sources and the unresolved nature of how deep earthquakes affect surface conditions.
- #2
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Potsdam has 7.0 in 133 km depth. Sounds deep.
http://geofon.gfz-potsdam.de/eqinfo/seismon/globmon.php
http://geofon.gfz-potsdam.de/eqinfo/seismon/globmon.php
- #3
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USGS 127 km ... yeah, a reasonably deep event ... that means the amplitude on my seismo would have been even bigger had it been "normal (shallow)" depth !fresh_42 said:
- #4
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USGS have now upgradsed it to M 7.2 and that doesn't surprise me considering the amplitude it has.
They are now taking into account the depth
and that seismo mob you commented on, have upgraded it to M7.1
http://geofon.gfz-potsdam.de/eqinfo/seismon/globmon.php
Dave
They are now taking into account the depth
http://geofon.gfz-potsdam.de/eqinfo/seismon/globmon.php
Dave
- #5
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I always find it really astonishing how precise those measurements from the other side of the planet are. In such a depth the error margin ##130 \pm 3## is pretty good, and ##7.0## to ##7.2## as well, considering the depth. Looks as if we all live on a giant bell.
- #6
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Can such deep quakes be felt at the surface in the sense that we should expect damages?davenn said:
- #7
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fresh_42 said:
up to around 150km and M7++, yes for sure, but not likely to be as bad. It's a little different to a M7+ event that is shallow and say 130km away as the Surface waves, the ones that cause most of the damage, are so very much stronger for a shallow event.
here's a graph from wiki showing the drop off of various period surface waves with depth
Interestingly, it can be seen that 50 second period waves pea just below 100km depth
- #8
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here's a screenshot of my seismogram
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