Wednesday, March 24, 2010

Strain Is Accumulating On Istanbul

Here is a good example of how geoscientists are creeping towards a better understanding of earthquakes by monitoring and estimating slip rates along major faults which then are used to estimate locations and likely magnitudes of future earthquakes.

The north Anatolian fault near Istanbul, Turkey has been accumulating strain since the last big one in 1766. Measurements and model estimates of slip rates along the main Marmara fault indicates that the slip rates are variable along the length of the fault.

The supplementary information to the paper is open access and the figure below shows estimated slip rates along the Marmara fault which is beneath the Mediterranean sea bed for long portions of its length.

This might mean scientists think that the building strain would eventually be released not as one big earthquake but several smaller ones as portions of the fault fail at different times and with differing intensities.

That's not to say Istanbul can breathe easy.

Continuing with my previous theme of how well prepared different countries are to face earthquakes and their aftermath, Istanbul scores lower than Chile in the quality of its building structures.

Andrew C. Revkin of Dot Earth interviews Turkish builder Ali Ağaoğlu who admitted that most developers in Turkey have in the past used inappropriate materials for constructing buildings. Since 2000 though all new construction according to him is of good quality but that still leaves about 70 percent of settlements vulnerable to a major earthquake.

How should the city respond? The interview reveals a tension between those that want government help in retrofitting old buildings against private developers who want the buildings razed and new ones built.

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