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    France Administrator Hervé's Avatar
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    Default Lithospheric Intraplate Horizontal Plane Delamination Fault Zone: The Initiation of Subduction Zones?

    Scientists Reveal Possible Reason Behind Deadly QUAKES on Iberian Peninsula

    Sputnik Tech
    14:10 07.05.2019


    The hypothetical phenomenon suggested by the scientists could shed light on the deadly Great Lisbon earthquake of 1755 and the 1969 quake in Portugal, both of which came as a surprise as the Iberian Peninsula is located far away from tectonic plate boundaries.

    A group of geologists led by Joao Duarte from the University of Lisbon has come forth with a hypothesis that the Eurasian Plate has started to delaminate and peel apart near the Iberian Peninsula's coast as a result of ocean water. In his article, which was presented at the European Geosciences Union (EGU) General Assembly, he argues that tomographic models indicate the existence of a seismic anomaly at a depth of 250 kilometres.
    "We interpret this anomaly as a lithospheric drip caused by the delamination of oceanic lithosphere. If this is the case, it is the first time that delamination of oceanic lithosphere is identified", the study says.
    The researchers suggest that a process of serpentinisation, a phenomenon [occurring] when rock structures absorb ocean water and change their [mechanical] properties as a result, has led the European Plate to begin separating the upper layer of the lithosphere from the lower one. This process, if proved to be taking place, could lead to the creation of a new seismic zone, where one [portion of the] tectonic plate is being driven under [the] other.

    The hypothetical process results in the plate being [sub-horizontally decoupled/split] in two [sheets], creating strong quakes as a result. The geologists indicate that such a [splitting] could explain the deadly magnitude 9 earthquake in 1755 that essentially wiped out Lisbon, killing between 10,000 and 100,000 people, according to various estimates; as well as the 7.9 magnitude earthquake in 1969 in the same region. Both quakes remain a mystery due to the Iberian Peninsula not being situated near [active] tectonic plate boundaries and [their] seismic zones.

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    Interestingly, I would have expected such a phenomenon to first start at the passive margin of the North American continent where the oceanic crust is older and colder... not at the Eurasian plate passive margin.

    I have edited [edited portion] part of the article for better accuracy.
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    Default Re: Lithospheric Intraplate Horizontal Plane Delamination Fault Zone: The Initiation of Subduction Zones?

    Here is a more competent article on the same subject:
    https://www.nationalgeographic.com/s...ocean-geology/

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    Default Re: Lithospheric Intraplate Horizontal Plane Delamination Fault Zone: The Initiation of Subduction Zones?

    There is no subduction, only expansion.

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