## 2 Materials and Methods
### Marine Oil Spill Scenario and Scenario Tree Construction Method  
A marine oil spill historical case can be divided into multiple scenarios according to its evolution. Each marine oil spill scenario can be described from the following three aspects: hazard, exposure and human behavior [21]. Since human behavior can strongly affect the results of a disaster, for example, due to the effective implementation of preparedness actions such as evacuation and rescue procedures, it is considered as a controllable driver of the development branch of oil spills. The hazard is the time-space distribution of the intensity of a given marine oil spill accident with an assigned occurrence probability at a given time and in a given geographical area. The exposure is the distribution of the probability that a given element (including people, buildings, infrastructure, the economy, or the environment) is affected by a disaster. In this paper, an oil spill scenario can be represented by a set of scenario elements as \(S=\{E_{1},E_{2},\ldots,E_{n}\},\ n\in\mathbb{N}^{+}\), where \(E_{i}\) is a scenario element instance that alternates in type between hazard and exposure. The scenario element instance set \(E_{i}=(T_{1},T_{2},\ldots,T_{m})\), where \(m\in\mathbb{N}^{+}\), is a vector composed of features, where \(T_{i}\) represents the attributes of a scenario element instance; such attributes may include the tonnage of the oil tanker and the amount of spilled oil as shown in Table 1. In this case, the scenario instance can be represented as  
\[S=\left[ \begin{array}{c}T_{11},T_{12},\ldots,T_{1m}\\ T_{21},T_{22},\ldots,T_{2m}\\ \ldots\\ T_{n1},T_{n2},\ldots,T_{nm}\end{array} \right] \tag{1}\] \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Order** & **Category** & **Scenario Element** & **Scenario Element Attributes** \\ \hline \multirow{4}{*}{1} & & & \multicolumn{2}{c}{Flash point; Condensation point; Density;} \\  & & & \multicolumn{2}{c}{Glue content; Sulphur content; Nitrogen content;} \\  & & & \multicolumn{2}{c}{Hydrogen content; Wax content;} \\  & & & \multicolumn{2}{c}{Asphalt value; Acid value; Carbon residue;} \\  & & & \multicolumn{2}{c}{Kinematic viscosity; Distillation range} \\ \cline{3-4}  & & & \multicolumn{2}{c}{Oil slick} & Color; Cover area; Thickness \\ \cline{3-4}  & & \multicolumn{2}{c}{Sea condition} & Window speed; Wave height; Water temperature; \\  & & & \multicolumn{2}{c}{Sea visibility} \\ \hline \multirow{4}{*}{2} & & \multicolumn{2}{c}{Oil tanker} & Offshore distance; Vessel age; Tonnage;} \\  & & & \multicolumn{2}{c}{Amount of spilled oil} \\ \cline{3-4}  & & \multicolumn{2}{c}{Offshore oil and gas platform} & Geographic position; Vertical height; \\ \cline{3-4}  & & \multicolumn{2}{c}{Marine organisms} & \multicolumn{2}{c}{Creature name; Wildlife habitat; Number of dead} \\  & & \multicolumn{2}{c}{creatures; State of fire or explosion} \\ \cline{3-4}  & & \multicolumn{2}{c}{Fisheries and} & Geographic position; Breeding number; Species \\ \cline{3-4}  & & \multicolumn{2}{c}{Subsea tunnel} & Geographic position; Buried depth of tunnel; \\  & & \multicolumn{2}{c}{Length of tunnel; Damaged area} \\ \cline{3-4}  & & \multicolumn{2}{c}{Port infrastructure} & Geographic position; Coastline length; \\ \cline{3-4}  & & \multicolumn{2}{c}{Use of the facility} \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Marine oil spill scenario element and scenario element attributes. An emergency response scenario is not a typical case, and the core of this approach is to identify instances with similar characteristics. The similar scenario instances are merged into a typical scenario, and consequence scenario instances are linked to the typical scenario. Thus, the expanded branches express the uncertainties of the evolution of marine oil spill accidents.