Analysis of seismic characteristics for permafrost according to porosity ratio using 3D printing technology

Permafrost means soil that remains below 0 ℃ for at least two continuous years. Due to climate change, permafrost is thawing, releasing greenhouse gases(Schuur et al., 2015; Colett et al., 1988). Greenhouse gas emissions from permafrost could accelerate climate change. Therefore, it is necessary to detect and predict changes by estimating the distribution and thickness of permafrost. One of the methods to detect permafrost and detect changes is seismic exploration. Permafrost has various geological characteristics depending on the region, and the porosity of permafrost affects the acoustic wave characteristics(Brothers et al., 2016). Therefore, in order to detect permafrost and detect changes in seismic exploration data, a study is needed to analyze seismic characteristics according to the porosity of permafrost.

In order to create a model according to the porosity of the permafrost and analyze the characteristics of seismic, the porosity was controlled using 3D printing technology and seismic data was acquired through an seismic physical modeling. In this study, an FDM(fused deposition modeling) 3D printer was used to control the porosity of permafrost. Since the porosity of permafrost is about 20-50 % depending on the region, the pore size was set to 3, 4, and 5 mm to create a model similar to the porosity of permafrost. Permafrost was simulated by saturating and freezing water in the pores of the porosity model according to porosity.

A seismic physical modeling was performed to acquire seismic data in permafrost according to porosity. The seismic physical modeling is an experiment that reduces field exploration to a laboratory scale and has excellent field reproducibility. A 1 MHz transducer was used as the source and receiver, and signals were generated using a pulser/receiver. Signals were received and stored using a digital oscilloscope. In order to analyze the characteristics of permafrost according to porosity, the velocity and maximum amplitude were analyzed in the time domain from the acquired seismic data. In addition, the maximum frequency and magnitude according to the porosity of the permafrost were analyzed in the frequency domain.

In this study, 3D printing technology was used to control the porosity of permafrost. Additionally, seismic characteristics were analyzed according to the porosity of the permafrost using a seismic physical modeling. The results of this study are expected to be used as basic data to understand the characteristics of permafrost according to its porosity and to detect and detect changes in permafrost.

 

Acknowledgement

This research was supported by Korea Institute of Marine Science & Technology Promotion (KIMST) funded by the Ministry of Oceans and Fisheries, Korea (RS-2023-00259633).