Response Of Building Structures To Scaled Laboratory Earthquake Ruptures

We propose a unique framework to study the response of building structures to earthquakes using a laboratory earthquake setup. Specifically, we are interested in assessing the damage done to near-fault structures by sub-Rayleigh and supershear earthquake ruptures. The laboratory earthquake experiment originally developed by Rosakis and coworkers (Xia et al., 2004, 2005a, 2005b; Lu et al., 2007; Rosakis et al., 2007) is deployed. Heterodyne laser interferometers enable continuous, high bandwidth measurements of fault-normal (FN) and fault-parallel (FP) particle velocity ``ground motion" records at discrete locations on the surface of a Homalite test specimen as a sub-Rayleigh or a supershear rupture sweeps along the frictional fault. Photoelastic interference fringes, acquired using high-speed digital photography, provide a synchronized, spatially resolved, whole field view of the advancing rupture tip and surrounding maximum shear stress field. A key element for the applicability of this study is a proper scaling relationship between laboratory and natural earthquakes. We use the 2002 Denali earthquake ground motion recorded at Pump Station 10 as a benchmark to develop a scaling relationship between laboratory data and natural earthquakes. This scaling relationship then enables us to examine hypothetical rupture scenarios on the Denali fault. Previous work (Mello et al. 2010) has demonstrated unique ground motion signatures associated with supershear earthquake ruptures, specifically the leading shear Mach front characterized by a dominant fault parallel component followed by a trailing Rayleigh disturbance with a dominant fault normal component. Using a finite element code, FRAME3D, developed by Krishnan et al. 2009, we present a three-dimensional analyses of buildings subjected to scaled particle velocity records derived from laboratory data. We examine the cumulative effect of the shear Mach field and the trailing Rayleigh disturbance on hypothetical structures. We also quantify the damage on such structures as a function of increased fault normal distance subject to the attenuation properties of sub-Rayleigh and supershear velocity fields.