Towards an earthquake early warning system for the megacity of Istanbul

Jochen Zschau1, M. Isikara2, O. Ergünay3, M. N. Yalçin4, M. Erdik2
GeoForschungsZentrum Potsdam, Telegrafenberg E424, D-14473 Potsdam, Germany.
Tel. :+49-331-288-1200, Fax: +49-331-288-1204,
E-mail: zschau@gfz-potsdam.de
2Kandilli Observatory, Istanbul
3Ministry of Public Work and Resettlement, Ankara
4Tübitak, MRC, Gebze

One of the megacities directly located in an earthquake prone area is Istanbul. Destructive historical earthquakes in the past 2000 years hit Istanbul about once every century. Between 1950 and 1990 the population increased from 1 to about 10 Million people. About one half of the industrial potential of Turkey is concentrated in this area. Due to the immediate vicinity of the North Anatolian Fault System, overpopulation and concentration of industries and infrastructure, Istanbul has developed to a megacity with extremely high vulnerability against earthquakes.

An earthquake early warning system in the area of Istanbul does not encounter easy seismological conditions. The tectonics in the area shows the transition of the North Anatolian Fault System from strike slip east of the Marmara region to a system of faults with different mechanisms in the Marmara region itself. Earthquakes with a destructive potential for Istanbul may happen along an about 250 km long zone extending from Adapazari-Izmit some 150 km east of Istanbul to the Marmara Sea area immediately south to some 100 to 150 km southwest of Istanbul.

This paper outlines an earthquake early warning system for the area of Istanbul and summarises the corresponding current activities. At present the project is a co-operation between Kandilli Observatory (Istanbul), Tübitak, MRC (Gebze) and Earthquake Research Institute (Ankara) in Turkey as well as the GeoForschungsZentrum Potsdam in Germany.

The concept has four main components:

  • long-term component (stocktaking, preparation phase)
  • medium-term component (years to days before an earthquake)
  • short-term component (earthquake happened)
  • instantaneous component (earthquake hit the city)

The long-term component is intended to collect and provide all relevant data to cope with a potential destructive earthquake in the area of Istanbul. It includes the stocktaking of the area, earthquake hazard assessment, microzonation, process modelling, and the installation of monitoring systems. Current activities are focussing on the combination and completion of existing digital seismological networks around Istanbul, on the incorporation of the existing multiparameter observatories and a continuously recording GPS-system to be established in the Marmara region, as well as on simulations of earthquake scenarios. The inclusion of information from earthquake prediction studies of different national and international groups in the area is part of the medium-term component. The short-term component includes the automatic determination of earthquake hypocentres and magnitudes. At present only part of the digital seismological network is capable of a first estimation of these parameters within less then ten seconds. However, by combining the existing seismic networks we are expecting to obtain this capability for the whole area with destructive earthquake potential for Istanbul. The instantaneous component is still in the planing phase. It will incorporate rapid damage evaluation combined with GIS based vulnerability information as well as rapid information dissemination.