P-wave velocity changes in freezing hard low-porosity rocks: a laboratory-based time-average model

Author:

Draebing D.,Krautblatter M.

Abstract

Abstract. P-wave refraction seismics is a key method in permafrost research but its applicability to low-porosity rocks, which constitute alpine rock walls, has been denied in prior studies. These studies explain p-wave velocity changes in freezing rocks exclusively due to changing velocities of pore infill, i.e. water, air and ice. In existing models, no significant velocity increase is expected for low-porosity bedrock. We postulate, that mixing laws apply for high-porosity rocks, but freezing in confined space in low-porosity bedrock also alters physical rock matrix properties. In the laboratory, we measured p-wave velocities of 22 decimetre-large low-porosity (< 10%) metamorphic, magmatic and sedimentary rock samples from permafrost sites with a natural texture (> 100 micro-fissures) from 25 °C to −15 °C in 0.3 °C increments close to the freezing point. When freezing, p-wave velocity increases by 11–166% perpendicular to cleavage/bedding and equivalent to a matrix velocity increase from 11–200% coincident to an anisotropy decrease in most samples. The expansion of rigid bedrock upon freezing is restricted and ice pressure will increase matrix velocity and decrease anisotropy while changing velocities of the pore infill are insignificant. Here, we present a modified Timur's two-phase-equation implementing changes in matrix velocity dependent on lithology and demonstrate the general applicability of refraction seismics to differentiate frozen and unfrozen low-porosity bedrock.

Publisher

Copernicus GmbH

Subject

Earth-Surface Processes,Water Science and Technology

Reference95 articles.

1. Akimov, A. T., Dostovalov, B. N., and Yakupov, V. S.: Geophysical methods of studying permafrost, 2nd International Conference on Permafrost, USSR Contribution, Yakutsk, USSR, 767–777, 1973.

2. Anderson, D. M. and Morgenstern, N. R.: Physics, chemistry, and mechanics of frozen ground: A review, 2nd International Conference on Permafrost, Northamerican Contribution, Yakutsk, USSR, 257–288, 1973.

3. Barnes, D. F.: Geophysical methods for delineating permafrost, 1st International Conference on Permafrost, LaFayette, Indiana, 1963, 349–355, 1965.

4. Barsch, D.: Refraktionsseismische Bestimmung der Obergrenze des gefrorenen Schuttkörpers in verschiedenen Blockgletschern Graubündens, Schweizer Alpen, Zeitschrift für Gletscherkunde und Glazialgeologie, 9, 143–167, 1973.

5. Barton, N.: Rock quality, seismic velocity, attenuation and anisotropy, Routledge, London, Leiden, New York, 756 pp., 2007.

Cited by 51 articles. 订阅此论文施引文献 订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献

同舟云学术

1.学者识别学者识别

2.学术分析学术分析

3.人才评估人才评估

"同舟云学术"是以全球学者为主线,采集、加工和组织学术论文而形成的新型学术文献查询和分析系统,可以对全球学者进行文献检索和人才价值评估。用户可以通过关注某些学科领域的顶尖人物而持续追踪该领域的学科进展和研究前沿。经过近期的数据扩容,当前同舟云学术共收录了国内外主流学术期刊6万余种,收集的期刊论文及会议论文总量共计约1.5亿篇,并以每天添加12000余篇中外论文的速度递增。我们也可以为用户提供个性化、定制化的学者数据。欢迎来电咨询!咨询电话:010-8811{复制后删除}0370

www.globalauthorid.com

TOP

Copyright © 2019-2024 北京同舟云网络信息技术有限公司
京公网安备11010802033243号  京ICP备18003416号-3