## 1 Introduction  
Safety at sea has always been a major concern for the shipping industry, due to the serious consequences of maritime accidents [1]. Based on accident causation theory, accidents occur as a result of the consistent evolution of physical unsafe conditions and human unsafe acts under the interaction of environmental conditions, management defects, and other influencing factors. A large number of studies have been devoted to investigate the causes of industrial accidents and pointed out that human unsafe acts are the main and direct causes of accidents [2]. The international shipping industry began to recognize the significance of unsafe acts in the 1970s [3], and 80% of maritime accidents were attributed to unsafe acts of seafarers [4]. The International Maritime Organization (IMO) called on countries to make sure that they pay more attention to unsafe acts when conducting maritime transport safety studies [5]. With the efforts of IMO, the International Convention on Standards of Training, Certification and Watchkeeping for Seafarers (STCW Convention) and the International Safety Management Code (ISM Code) were introduced sequentially, which proposed new requirements for promoting maritime safety from the perspective of seafarer training and management, respectively. In 1999, to avoid neglecting or missing critical information on human factors in maritime investigations, IMO adopted the Amendments to the Code for the Investigation of Marine casualties and Incidents (A.884(21)), which provides maritime investigators with methods and procedures for investigating human factors in the maritime accidents [6]. Although the shipping industry continues to take proactive initiatives to improve the safety of seafarers' acts, the incidence of maritime accidents has not been controlled to the expected level [7, 8]. Safety in maritime transportation is based on the coordinated operation of the \"human-ship-management-environment\" system [9]. The purpose of maritime safety management is to avoid unsafe acts of seafarers, eliminate unsafe conditions of objects, reduce unsafe management in the organization and control unsafe factors in the environment. Due to the progress of science and technology, the safety and reliability of ship machinery have been greatly improved, and the use of various monitoring and warning means has made the negative influence of environment factors effectively controlled. However, the seafarers, as the only part of the system with subjective initiative, have uncertainty in their acts. The occurrence of seafarers' unsafe acts is considered to be the result of the interaction among various complex and dynamic influencing factors [10; 11]. Factors from organization, technology, environment, and individual traits are coupled and superimposed on individual seafarers, making the generation of seafarers' unsafe acts uncertain, sudden, and random. As a result, human factors are recognized as the dominant cause of maritime accidents, accounting for 75-96% of maritime casualties [3; 4; 7]. Particularly, 79% of tugboat groundings [12], 84-88% of tanker grounding accidents [13], and 89-96% of collisions [14] were demonstrated to be triggered by human factors. In order to interrupt the risk propagation of human factors, clarifying seafarers' unsafe acts and their influencing factors, and exploring the complex risk interaction law among multiple factors have always been difficult issues in safety management and also important research trends in the field of maritime safety. As the complexity of maritime transportation activities increases, the interaction between seafarers' unsafe acts and their influencing factors has deepened. The traditional probability-based methods are no longer competent for risk assessment and cannot clarify the complex risk interaction in maritime transportation activities. Therefore, this study integrates association rule and complex network theory to analyze the interaction of seafarers' unsafe acts and their influencing factors in maritime transportation activities.