Palu supershear quake/tsunami Sept 2018

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Discussion Overview

The discussion centers on the Palu supershear earthquake and tsunami that occurred in September 2018, focusing on the unique characteristics of the seismic event, particularly the concept of supershear and its implications for seismic wave propagation. Participants explore the phenomenon's rarity and its detection through seismographic data.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants describe supershear as a rare phenomenon characterized by the high velocity of rupture propagation during an earthquake.
  • One participant expresses uncertainty about the manifestation of supershear on seismograms, suggesting that it may result in higher frequencies of P and S waves due to the increased rupture velocity.
  • Another participant notes that the methodology for analyzing the supershear event may be detailed in the primary scientific article, indicating that the S-wave emanation point moves rapidly relative to seismic stations.
  • There is mention of the "bunching up" of waves on the wavefront, which may require multiple stations to accurately discern the rapidly moving location of the waves.
  • A participant references a specific speed of 9300 ft/s mentioned in popular science literature regarding the event.

Areas of Agreement / Disagreement

Participants express varying levels of familiarity with the concept of supershear, and while there is a shared interest in understanding its implications, there is no consensus on the specifics of its detection or the characteristics of the seismic waves involved.

Contextual Notes

Discussion includes assumptions about the relationship between rupture velocity and wave frequency, as well as the need for multiple seismographic stations to analyze rapidly moving wavefronts. The exact methodology and data interpretations remain unresolved.

Who May Find This Useful

Individuals interested in seismology, earthquake phenomena, and the analysis of seismic wave propagation may find this discussion relevant.

jim mcnamara
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Popular article: https://www.nationalgeographic.com/...hquake-supersonic-supershear-speed-indonesia/
Nature.com paywall/abstract:
https://www.nature.com/articles/s41561-019-0308-8

After analysis of the quake centered near Palu Indonesia that killed 2000+ people, it was determined that the velocity at which the tremor propagated the tear in the earth, this was "no ordinary earthquake". It is termed a supershear event.

Supershear refers to the velocity of propagation of the rupture. These are rare. This one had lots of seismogaphs listening. Maybe our @davenn can point out this phenomenon using his output as recorded on his machine.
 
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jim mcnamara said:
Supershear refers to the velocity of propagation of the rupture. These are rare

They must be ! ... Supershear is not a term I have heard of before
jim mcnamara said:
This one had lots of seismogaphs listening. Maybe our @davenn can point out this phenomenon using his output as recorded on his machine.
Hmmm, not sure how these would be manifest on a seismogram.
My initial thought would maybe a higher frequency of the P ( and maybe also the S) waves due to the higher velocity of the propagation of the rupture.

I would have to try and see if there is a difference in P wave frequencies of that event compared to others with a similar distance from my recorder.

Dave
 
If you can access Nature Geoscience, then I assume there is methodology in the primary article.

[guess]The idea is that the point of emanation of the S-waves would be moving really fast relative to one station. It also mentions "bunching up" of multiple waves onto the wavefront.[/guess]

So possibly it takes multiple stations to discern a rapidly moving location. The pop sci article mentions 9300 ft/s.
 
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