Investigation On The Effects Of Foundation Stiffness On Surface Fault Rupture In Reverse Dip-Slip Faults
The occurrence of large earthquakes in cities placed near active faults is an undeniable fact. Earthquakes which occur in these cities have different characteristics from those occuring in cities placed in far-field. After destructive earthquakes, such as Landers-California(1992), Kobe-Japan(1995), Chi-Chi-Taiwan(1999), Duzce and Kocaeli-Turkey(1999), engineering societies and scientific committees realized that these different characteristics should be considered in analysis and design of structures placed in near fault.One of these characteristics is surface fault rupture which is a very destructive feature of near-fault earthquakes and has caused great loss of lives and severe damages to lots of structures. But, past earthquakes showed that there were also some structures that survived this surface fault rupture and the rupture path was changed and passed away from the structures instead of passing under the foundation of structure; this fact shows that by studying this characteristic and setting some limitations on the construction of structures in near-fault, structures can survive this destructive feature. In most standards of seismic design of structures, this characteristic was denied; in some other standards, fault avoidance zones have been considered in order to deal with surface rupture, but these zones are not adequate for this purpose due to different reasons.In this investigation, this characteristic of near-fault earthquake was investigated by studying the effect of foundation stiffness on the surface fault rupture. In order to study the effects of this characteristic on designing structure in near-fault field, 2D models of soil layer with the mat foundation on it were modelled in finite element software ABAQUS considering soil-foundation interaction. The stiffness of foundation was varied with 2 parameters, the thickness of foundation and the length of it.Results demonstrate that the foundation stiffness has an obvious effect on the surface rupture path and increasing stiffness of the foundation by increasing the thickness of it or decreasing the length of it changes the path of surface fault rupture.
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