Investigation of the Local Soil Effects at the New Strong-Motion Array (MATNet) in Hatay-K.Maras Region, Turkey

Abstract:

The national strong-motion network in Turkey (TR-KYH) is owned and operated by the Prime Ministry, Disaster and Emergency Management Presidency Earthquake Department (AFAD). All TR-KYH stations generates real-time continuous data. A new dense strong-motion array (MATNet) has been installed near Hatay-K.Maras areas. It is at the SW corner of the East Anatolia Fault Zone (EAFZ). Primary target of MATNet is to investigate local site effects. Other important goal is to evaluate them as a part of early warning and preliminary damage estimate system. We also aim to develop a new attenuation relationship in the future from records including this new array. Most recorders are deployed as free-field and mounted in the container which is designed and produced for specific purposes.

Hatay, Iskenderun and K.Maras cities have residential, industrial and dense populated areas. New stations are installed on different geological units in 1-3 km or 5-15 km intervals in city centers. Distances increase up to 30 km at the outside of settlements. The MATNet contains 55 triaxial force-balance accelerometers and capable to record explosions. A recent earthquake (Mw=4.5) occurred in the Gulf of Iskenderun on 14 February 2014, and triggered the MATNet and other regional accelerographs (80 triaxial strong-motion stations in total). Location of MATNet strong-motion stations in Hatay-K.Maras Region, Turkey, and distribution of triggered accelerometers during the recent earthquake (Mw=4.5), have been shown in the figure as a- and b-. In the present study, we analyzed to estimate the site response in the frequency range 0.5-10.0 Hz using the reference site (SSR) and HVSR techniques. The site response values thus obtained at each strong-motion sites were observed to be associated with the Quaternary formations. The maximum site amplifications at 0.5-1.8 Hz are detected as 10 around Hatay city, 6-8 (for 0.8-2.3 Hz) near K.Maras and Iskenderun areas. It is apparent that in both 0.5-1.8 and 0.8-2.3 Hz frequency bands, presence of geological contacts and sediment thicknesses controls the site responses in the study areas. It is also inferred that larger site response (~10) value in the 0.5 Hz frequency band could be indicating the probable presence of soil class C (360<Vs≤760 m/s) or D (180<Vs≤360 m/s) in the Hatay basin according to NEHRP provisions.