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Happened to see notice of fairly strong earthquakes near Fiji and Peru within the past few days, and thought I'd find they had been fairly damaging... only to find the impacts were quite minimal. Have to think maybe that relates to the depths they occurred at (563 km and 610 km)?

It seems like an overall busy period, with earthquakes in/near Indonesia, Venezuela, and Oregon as well in about the last week. But I do feel like I've seen similar bursts in the past.

However, I'm naively not sure I've ever seen such deep ones reported where they apparently didn't cause much shaking. I figure that may well be just because such earthquakes having minimal impacts simply weren't as publicized in the past??

But, not knowing nearly enough about the differences in earthquake types and patterns, I'd be interested to know:

  • Were the minimal impacts indeed a consequence of the depths of the earthquakes?
  • Are such strong earthquakes at those depths expected at fairly similar regularity to similar earthquakes at shallower depths?
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  • $\begingroup$ I guess thinking about this now, you'd first-oder expect the impacts of a 600 km deep earthquake may be similar to the impacts 600 km from the epicenter of a near-surface earthquake of the same strength. Perhaps similar to how anvil crawler lightning often doesn't make thunder despite occurring right over head... because it's so high up. (Of course physics can be quite different horizontally vs vertically, but seems a basic way to think about it). Sometimes I certainly forget how immense depth can really be in our world (even in the "smaller" lithosphere/troposphere) $\endgroup$
    – JeopardyTempest
    Commented Jul 29, 2023 at 21:28

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Depends where you are in the world, New Zealand has a combination of deep and shallow earthquakes, the shallow ones are associated with the slip-strike faults in the south. The deeper ones on the other hand occur where subduction is the dominant tectonic scheme in the north island, particularly in central and eastern areas. A deep earthquake of a given magnitude will cause considerably less damage to human artifacts than a shallow one; there's more, and softer, rock between the rupture zone and the surface to absorb the energy of the 'quake. If they're deep enough then the hot, plastic, rocks between the rupture and the surface will in fact block most of the L and R shear waves that often cause the most surface damage.

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  • $\begingroup$ That makes a great deal of sense (no idea why I didn't consider the very basics of fault interfaces, and realize that subduction would be quite likely to be deep...) Thanks! $\endgroup$
    – JeopardyTempest
    Commented Aug 27, 2018 at 15:51
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    $\begingroup$ @JeopardyTempest It helps that I actually live somewhere that has multiple earthquakes in the 3-4 point range every day of the year. $\endgroup$
    – Ash
    Commented Aug 27, 2018 at 15:54

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