Fault rupture–foundation interaction: selected case histories

Abstract

The 1999 earthquakes in Turkey and Taiwan, offering a variety of case histories with structures subjected to large tectonic displacements, have refueled the interest of the earthquake engineering community on the subject. While several structures were severely damaged or even collapsed, there were numerous examples of satisfactory performance. Even more astonishingly, in specific cases the surface fault rupture was effectively diverted due to the presence of a structure. For the purpose of developing deeper insights into the main\ud mechanisms controlling this fascinating interplay, this article documents selected field case histories of fault rupture–foundation interaction from (a) the Mw 7.4 Kocaeli (August 17)\ud 1999 earthquake in Turkey, (b) the Mw 7.1 Düzce-Bolu (November 12) 1999 earthquake in Turkey, (c) the Mw 7.6 Chi–Chi (September 21) 1999 earthquake in Taiwan, and (d)\ud surface faulting in Mount Etna. A subset of the case histories presented herein is analysed numerically, using the methods developed in the companion paper. It is shown that relatively\ud “heavy” or stiff structures supported by continuous and rigid foundations may divert the fault rupture. Such structures are subjected to rigid body rotation, without substantial structural\ud distress. In contrast, structures on structurally–resilient foundation systems or on isolated supports are prone to substantial damage

Simplified theoretical approaches to earthquake fault rupture–shallow foundation interaction

“…2 and 7, it can be seen that in most practical situations, if a safety factor 3≤FS≤ 5 against bearing capacity failure is selected, a relatively shallow surface soil layer is sufficient for the fault rupture to be diverted from the foundation base. Although this result may appear to be too unrestricted, it is indirectly confirmed by the numerous examples of satisfactory performance of not-engineered buildings in the vicinity of surface fault ruptures, as documented by Faccioli et al (2008). However, for a careful interpretation of the previous charts, it should be reminded that they are based on the assumption of a rigid and continuous shallow foundation system: if this condition is not met, as in the case illustrated by Faccioli et al (2008) of the Tze-Min Commerce and Technical College 5-storey building intersected by the Chelungpu thrust fault during the 1999 Chi-Chi earthquake, these results are not applicable.…”

“…As thoroughly documented by field case histories in the companion paper by Faccioli et al (2008), heavy or stiff structures supported by continuous and rigid shallow foundations may interact with the emerging fault breakage and divert it from the foundation itself, thus contributing to the reduction of risk of structural collapse. These observations were further supported by the centrifuge model tests in which interactions of normal and reverse faults with shallow foundations on dry sand were analysed experimentally (Bransby et al 2008a,b).…”

Numerical analyses of fault–foundation interaction

“…It initiates from the top-right (footwall-side) edge of the foundation and propagates downwards. This All of the above factors are examined herein, with the exception of the type of foundation system: given that the continuity of the foundation system has already been shown to be (Anastasopoulos and Gazetas 2007b;Faccioli et al 2008), we will focus on buildings resting on mat foundations (slab or box-type). Without underestimating the general importance of the details of a superstructure, we treat all of the analysed structures as "equivalent" in this respect, changing only the number of storeys.…”

“…However, examples of satisfactory, even spectacular, performance of a variety of structures also emerged (Youd et al 2000;Erdik 2001;Bray 2001;Ural 2001;Ulusay et al 2002;Pamuk et al 2005). In some cases the foundation and structure were quite strong and thus either forced the rupture to deviate or withstood the tectonic movements with some rigid-body rotation and translation but without damage (Anastasopoulos and Gazetas 2007a, b;Faccioli et al 2008). In other cases structures were quite ductile and deformed without failing.…”

“…• Field studies (Anastasopoulos and Gazetas 2007a;Faccioli et al 2008) of documented case histories motivated our investigation and offered material for calibration of the theoretical methods and analyses, • Carefully controlled geotechnical centrifuge model tests (Bransby et al 2008a, b) helped in developing an improved understanding of mechanisms and in acquiring a reliable experimental data base for validating the theoretical simulations, and • Analytical numerical methods calibrated against the above field and experimental data offered additional insight into the nature of the interaction, and were used in developing parametric results and design aids.…”