Basin Amplification Effects on Structures: Bridge Fragility Subjected to Subduction Earthquakes

The sedimentary basins are regions of the earth’s crust that consist of thick multiple layers of sedimentary soil deposits. With the availability of fresh water and flat terrain for ease of infrastructure, the sedimentary basins have become home the dense urbanization. Most of the densely populated cities like Mexico, Seattle, and Kathmandu located directly on basins. Due to the impedance contrast between basin and bedrock materials, these sedimentary basins often amplifies the seismic waves. One of the classic examples is 1985 the Michoachan earthquake where the Mexico City located at 350 km from the epicentre, suffered significant damage. It is also evident that the densely populated basins are in the vicinity of seismically active fault regions such as Cascadia subduction zone and Himalayan fault zone. Since the sedimentary basins often lead to amplification of the seismic ground motion, which eventually increases the consequences of earthquakes on civil infrastructure, the investigation of the basin amplification is one of the major concern issues for seismologists and earthquake engineers.