Influence of anthropogenic landscape modifications and infrastructure on the geological characteristics of liquefaction

Many large cities worldwide are built on natural and engineered geological materials that are highly susceptible to liquefaction and associated ground failure in earthquakes. Constitutive equations describing relationships between sediment geotechnical characteristics, seismological parameters, and liquefaction susceptibility of natural and engineered sediments are well established. What is less understood is the role of anthropogenic landscape modifications (e.g., river channel modifications, sediment engineering and re-distribution) and infrastructure (e.g., buildings, buried infrastructure such as drainage systems) on the spatial distributions and severity of liquefaction and ground deformation. Here we use stratigraphic studies, ground penetrating radar (GPR), and analyses of high-resolution aerial photographs to evaluate surface and subsurface geological manifestations of recurrent liquefaction in anthropogenically-modified landscapes during the 2010-2011 Canterbury earthquake sequence in New Zealand. Engineered fill layers provided low density, high permeability traps that captured fluidized sediment and promoted the formation of a unique assemblage of liquefaction-induced sediment intrusions that differ from those preserved in proximal natural sediment. Subsurface drainage systems imparted significant influence on the location, size and orientations of liquefaction ejecta features. Sediments adjacent to engineered stream channels experienced large lateral strains that are unlikely to have occurred in the absence of channel modifications. Spatial variations in pre-Anthropocene topography and liquefaction-susceptible sediments exerted strong influence on the characteristics of liquefaction hazards, even in highly engineered environments. Collectively, these observations highlight important interactions between concomitant Anthropocene and pre-Anthropocene environments that should be carefully considered when interpreting the geologic effects of contemporary earthquakes and / or using pre-Anthropocene geological records to forecast future hazards.The following supplementary files are included: - Figures S.1 - S.6 - Tables S.1 - S.3 - ST.1_Supplemental Text for Figure Captions - SCPT_1 Factual Geotechnical Report - SCPT_1 CPT data.xls - SCPT_1 Seismic data.xls - Porritt Park GPR lines (unannotated) - Avondale Park (AP) GPR lines (unannotated) Funding provided by: Frontiers AbroadCrossref Funder Registry ID: http://dx.doi.org/NoneFunding provided by: EQCCrossref Funder Registry ID