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Geophysical investigations of marine geohazard risks to infrastructure incoastal zonesTodd Mitchell 1 , Daniel Ebuna 1 Phil Hogan 2 , & Kevin Smith 21 Fugro Pelagos, Inc., 4820 McGrath Street Suite 100, Ventura, CA, 93003, USAtmitchell@fugro.com, debuna@fugro.com2 Fugro Consultants, Inc., 4820 McGrath Street Suite 100, Ventura, CA, 93003, USAphogan@fugro.com3 Fugro Consultants, Inc., 101 W Main Street, Suite 350, Norfolk, VA 23510, USAksmith@fugro.comAbstractSea level rise, tsunamis, nearshore earthquakes, and hurricanes continue to alarm us as they threaten the infrastructureand the lives of millions people globally. Heightened awareness of the impacts of these coastal processesand episodic natural disasters has brought far more attention to the threats to coastal infrastructure and those residingthere. With such a significant amount of existing infrastructure as well as new projects planned within coastal zones,the need for properly identifying the geospatial and geological hazards associated with the sites becomes critical forcost-effective construction and sustained operation throughout their designed life. Improved offshore seismic geophysicalexploration techniques can be applied to these geohazard investigations allowing vastly improved assessmentsof the risks posed by such hazards. Geophysical data is only one element of these studies. Thus it is importantto utilize a platform that can integrate geophysical data with other sources. GIS can play a key role in the integration,analysis, managing, and presentation of these datasets.IntroductionNearly every year a large seismic event takes lives and causes significant damage to infrastructure. These can beparticularly problematic when the fault lies hidden or below the ocean floor, especially in locations close to existinginfrastructure and/or habitation. The devastating earthquakes in Tohoku, Japan (2011), Maule, Chile (2010), andChincha Alta, Peru (2008) are recent examples of these events. The Tohoku earthquake was monitored globally asthe impacts of the earthquake and tsunami devastated the Fukushima Dai-ichi nuclear power plant. The concern forour coastal infrastructure has likely never been greater.Geohazard studies are those that look to identify geologic and geospatial hazards with the potential to hinder theconstruction of or that threaten existing infrastructure. Characterization of coastal geohazards may include conductingtopographic and/or bathymetric surveys to consider terrain impacts (such as slope stability or liquefaction) aswell as geophysical surveys that explore the subsurface, below the seafloor, for hazards (such as seismic groundmotion or sediment processes). New technologies and methods have improved our ability to detect and evaluatefault hazards. Offshore geophysical investigations using seismic reflection exploration techniques have achieved anew level of resolution and fidelity. In recent years, these methods have been refined and have demonstrated unparalleledability to characterize coastal geohazards.However, geophysical data is only one element of the variety of datasets used for these studies. GIS plays an importantrole in assembling a comprehensive data model that also includes geotechnical exploration data, bathymetrysurface data, and (where available) seafloor imagery data. As there are many input data sources, there are also manydisparate end users of these datasets. Geologists, geotechnical engineers, surveyors, contractors, designers, projectowners, and even the public – many people require the data in a usable and accessible format. GIS is often themechanism to enable this.Ultra-high-resolution offshore seismic reflection geophysicsMany geophysical survey projects conducted for infrastructure are performed in relatively shallow water – oftenin the presence of vessel traffic and/or in confined spaces. Small survey areas also require frequent turns of the vessel.These issues may demand operating only during daylight hours and thus necessitate nimble deploy-108