Behaviour of foundations over surface fault rupture: Analysis of case histories from the Izmit (1999) earthquake

The 1999 Mw7.4 Izmit (Turkey) earthquake was triggered by reactivation of the North Anatolian Fault. Although the faulting mechanism was strike-slip, the paper focuses on the normal fault that nucleated within the pull-apart basin of Golcuk, and its effect on overlying residential structures. The 4 km normal rupture, caused maximum vertical displacements of 2.3 in. Several structures were crossed by the rupture. As expected, many of them either collapsed or were severely damaged. Surprisingly, some structures survived the dislocation with no damage, while in some cases the rupture deviated to "avoid" the structures. Luckily, the foundation of the involved structures comprised a variety of foundation types, ranging from simple separate footings to piled foundation. The paper provides a comprehensive description of the observed fault-foundation interaction patterns, accompanied by the results of soil exploration and geological trenching. Each structure is analyzed through the use of finite element modelling to reveal the main aspects of Fault Rupture-Soil-Foundation-Structure Interaction (FR-SFSI).