Site Classification and Seismic Hazard Assesment of Kocaeli Province of Turkey

Objectives:
In this project, the Greater Metropolitan Municipality of Kocaeli and Marmara Research Center of TÜBİTAK have worked towards Site Classification and Seismic Hazard Assesment of Kocaeli Province of Turkey. With this purpose, a series of  geological and geophysical surveys and investigations were carried out. These surveys included macro scale investigations and measurements to determine S-wave profiles at 60 different sites selected in various settlement areas.  A site classfication map of Kocaeli was produced based on average S-wave velocity down to 30 m depth and surface geological class map. To investigate the deep structure of the Izmit Basin, S-wave profiles and newly collected 327 point Gravity data were jointly evaluated to obtain a map of three-dimensional bedrock depth. The results shows that bedrock depth reaches down to 750-800 m depth in the middle of the Basin. A total of 422 three-component microtremor measurements were made to directly obtain site resonance frequency and horizontal to vertical amplification parameters using the well-known spectral ratio method.
Vs30 derived from S-wave velocity profiles and bedrock information were used to perform a deterministic Seismic Hazard analysis for selected scenario earthquakes that may threaten the city of Kocaeli both at local and regional scales.  Seismic Hazard Maps were produced in terms of maximum horizontal Peak Ground Accelarations (PGA) ans Spectral Accelerations (SA) using Geographical Information Sytems. These maps were then unified into a single map of ‘Seismic Hazard Zones of Kocaeli’. These macro-scaled maps are anticipated to lead decision makers in settlement&city planning actions, seismic retrofitting, engineering designs, identification of earthquake safe regions. The Turkish Earthquake Code (2007) was used to evaluate the predicted PGA and SA values in these maps. This evaluation leads to a conclusion that the structural damage associated with large earthquakes in Kocaeli is not due to any shortcomings in the code, but is due to lack of enforcement of the code itself.

Supported by  Kocaeli Municipality

Duration: 05.10.2005 - 06.10.2008