Iran's massive earthquake explained

Apr 16, 2013 | Posted by: roboblogger | Full story: CBS News

The strongest earthquake to hit Iran in more than 50 years was a subduction-zone quake, the same tectonic setting underlying deadly temblors in Japan, Chile and Indonesia.

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1 - 2 of 2 Comments Last updated Apr 18, 2013

“Geologist [I'm Climate Change]”

Since: Mar 07

Nuneaton

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#2
Apr 17, 2013
 
Interesting report.

The really interesting bit is that it occurred on the arc graben rift and in that area the descending plate averages 120-140Km depth and anything @ less than 100Km is & that point in the base of the crust & upper mantle of the overriding plate.

This has a rather similar mechanism to a quake a couple of years ago near Wam (Balochistan) also in the arc graben, and also involving a rift mechanism.

In the case of rift events in compressing backarc basins, the result is usually the movement of magma in the base of the crust held in fractutes along the arc graben been squeezed sideways by tectonic compression into a less compressed part of the backarc basin. The magma is liquid & aseismic, but its movement dilates the arc graben & compresss the forearc (usually less compressed), The result of the dilation of the arc graben is a rift earthquake with a climbing aftershock series as the rift fault extends to the surface due to the top of the dilated arc graben falling in.

The rift quake series is extending toward the group of volcanoes in the core of the Makran backarc basin. Bazman (SW), An unnammed volcanic field (mid) and Taftan (NE) in the range sector in the mid of the Makran.

The result is likely to be a spectacular volcanic eruption at (most likley), Bazman volcano, sometime in the latter part of this century.

Other examples of magma movement resulting in dilation earthquakes @ backarc basins occur in the Tonga arc, and also in both the Calabrian & Aegean backarc basins of the Mediterranean. The most obvious one being Etna with the last dilation event occurring @ shallow level in 1908 resulting in a landslide & local large tsunami.

The unusual aspect of the current dilation series of earthquakes @ the Makran backarc basin is its unusual depth & the fact that the Makran is @ the latest stage of recompression and will undergo a megathrust earthquake of 2004 type in the relatively near future,(the compression appears to be sending the locals in Iran & Pakistan Gaga).
An unusual volcanic eruption of very small volume @ the SW. part of the pashtun range {Tur Zawar}(even more gaga there), N. of the N.margin of the Quetta basin forearc province probably has something to do with the current arc graben dilation quakes in the makran. The Magma probably originated in the arc of the Quetta arc & Pashtun backrange and as the region has a stronger megathrust it can compress to a much greater amount than the makran backarc basin.
Magma has been likely exported sideways out of the Quetta arc region & is now being transferred into the centre of the makran backarc basin where it will eventually erupt as a result of the Zagros range & margins being more compressed.

Proof will be the eruption of trachybasalt relatively similar to that of the Tur Zawar volcano erupting from one of the central Makran volcanoes, assuming of course that the high level magma chamber does not excessively modify the magma injected into the volcano from the base of the crust.

Keep watching that space, next quake in series will likely be south of Taftan.

Have a nice day: Ag
Die

Germany

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#3
Apr 18, 2013
 

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Iranians must build better buildings, which will be resist to earthquakes, there are such technologies. Clearly, that earthquakes will be there, because it is such region.
The deepst sympathy for victims and their families.

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