An effective-medium model for P-wave velocities of saturated, unconsolidated saline permafrost

• DOI: 10.1190/geo2016-0474.1
• Publication Date: 2017-03-02T10:49:19Z
• Authors: Shan Dou; Seiji Nakagawa; Douglas Dreger; Jonathan Ajo-Fran...
• Keywords: Geochemistry & Geophysics; Geophysics; 13. Climate action; Earth Sciences; 01 natural sciences; Physical Geography and Environmental Geoscience; 0105 earth and related environmental sciences

To better understand the relationship between P-wave velocities and ice content in saturated, unconsolidated saline permafrost, we constructed an effective-medium model based upon ultrasonic P-wave data that were obtained from earlier laboratory studies. The model uses a two-end-member mixing approach in which an ice-filled, fully frozen end member and a water-filled, fully unfrozen end member are mixed together to form the effective medium of partially frozen sediments. This mixing approach has two key advantages: (1) It does not require parameter tuning of the mixing ratios, and (2) it inherently assumes mixed pore-scale distributions of ice that consist of frame-strengthening (i.e., cementing and/or load-bearing) ice and pore-filling ice. The model-predicted P-wave velocities agree well with our laboratory data, demonstrating the effectiveness of the model for quantitatively inferring ice content from P-wave velocities. The modeling workflow is simple and is largely free of calibration parameters — attributes that ease its application in interpreting field data sets.