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

• Main Authors: Dou, Shan, Nakagawa, Seiji, Dreger, Douglas, Ajo-Franklin, Jonathan
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: eScholarship, University of California 2017
• Subjects: Earth Sciences; Physical Geography and Environmental Geoscience; Geophysics; Geochemistry & Geophysics; Ice; permafrost
• Online Access: https://escholarship.org/uc/item/1cg559k6

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 loadbearing) 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.