Knowledge Structure of Seismology in Materials and Energy Fields From 2010 to 2020: A Science Mapping Study

The main objective of this paper is to analyze the intellectual framework of seismology in two distinct domains: materials and energy, from 2010 to 2020, using a science mapping technique. These two fields were selected based on their investment rate by international institutions compared to other areas of seismology. Moreover, this study also focused on the evolution of different clusters and subclusters that were formed or transformed into other clusters during the time span of the study. 

To this end, scientometrics approach and science mapping technique used for creating an intellectual structure of seismology through a co-word analysis. Both strategic and theme evolution diagrams were prepared using R's Bibliometrix package. Strategic diagrams pinpointed the place of different clusters in four areas of Motor themes, Highly developed and isolated themes, Emerging or declining themes, and Basic and transversal themes. Sankey diagrams were also utilized in order to depict the evolution of different clusters through time. The time frames of these graphs were determined automatically by the R Bibliometrix package. 

the results showed that the number of papers in materials' field is higher than energy field and this number is ascending in both fields. 4 clusters were identified in the field of materials and each of them is placed in one of the 4 tiers of the strategic diagram. “Earthquakes” is placed in Motor themes, while “reinforced concretes” cluster is placed somewhere between motor themes and Basic and transversal themes. The "energy dissipation" cluster is classified under Highly advanced and isolated themes, while "walls (structural partitions)" falls under Emerging or declining themes. As for the energy field, six clusters were identified, but they were divided between two different quadrants of the strategic diagram. The clusters "earthquakes," "earthquake event," and "Nuclear power plant" were placed in the Motor themes quadrant, while "Wenchuan earthquake," "forecasting," and "stochastic systems" were fitted in the Emerging or declining themes quadrant. Another interesting finding of this study based on the Sankey diagrams is that during 2010 to 2020 in the field of materials at least 20 different clusters were formed and reformed or dissolved into other clusters which means that this field is somehow active and during 2014 to 2017 has experienced lots of changes and reforms among its sub-clusters. As for the energy field, 21 clusters were identified, each of which experienced some sort of transformation or even devastation. During 2017 and 2018, this field experienced its most active era. If we compare the results of both fields, we can infer that the materials field has undergone more branching than the energy field. In 2010, four clusters were identified in the materials field, whereas in 2020, the number of identified clusters increased to seven. However, in the energy field in 2010, 7 clusters were identified. However, by 2020, the number of clusters had declined to 5. The third part of this study's findings focuses on the highly cited papers in these two fields. The results show that the top ten most cited papers in the materials field are divided into eight different clusters. Among them concretes and earthquake resistance are placed among Motor themes and earthquake engineering and reinforcement clusters are fitted in Basic and transversal themes. While columns(structural) and separation clusters are placed in Emerging or declining themes. As for the energy field, these top 10 cited papers are divided into six clusters. Nuclear energy cluster is considered to be a Motor theme but risk assessment and seismology is placed in Highly developed and isolated themes. However, hydrolic fracturing and deformation clusters are fitted in Basic and transversal themes and earthquakes cluster is among Emerging or declining themes.

based on the results of this study, it is evident that thematic diversity in materials field is more than energy field. This trend is also observed among scientific products with higher citation rates. As for the evolution of clusters in both fields, the results indicate that the materials field has undergone more branching than the energy field.