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Seismic moulin tremor

Roeoesli, Claudia and Walter, Fabian and Ampuero, Jean-Paul and Kissling, Edi (2016) Seismic moulin tremor. Journal of Geophysical Research. Solid Earth, 121 (8). pp. 5838-5858. ISSN 2169-9313. http://resolver.caltech.edu/CaltechAUTHORS:20161111-085832479

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Abstract

Through glacial moulins, meltwater is routed from the glacier surface to its base. Moulins are a main feature feeding subglacial drainage systems and thus influencing basal motion and ice dynamics, but their geometry remains poorly known. Here we show that analysis of the seismic wavefield generated by water falling into a moulin can help constrain its geometry. We present modeling results of hour-long seimic tremors emitted from a vertical moulin shaft, observed with a seismometer array installed at the surface of the Greenland Ice Sheet. The tremor was triggered when the moulin water level exceeded a certain height, which we associate with the threshold for the waterfall to hit directly the surface of the moulin water column. The amplitude of the tremor signal changed over each tremor episode, in close relation to the amount of inflowing water. The tremor spectrum features multiple prominent peaks, whose characteristic frequencies are distributed like the resonant modes of a semiopen organ pipe and were found to depend on the moulin water level, consistent with a source composed of resonant tube waves (water pressure waves coupled to elastic deformation of the moulin walls) along the water-filled moulin pipe. Analysis of surface particle motions lends further support to this interpretation. The seismic wavefield was modeled as a superposition of sustained wave radiation by pressure sources on the side walls and at the bottom of the moulin. The former was found to dominate the wave field at close distance and the latter at large distance to the moulin.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1002/2015JB012786DOIArticle
http://onlinelibrary.wiley.com/doi/10.1002/2015JB012786/abstractPublisherArticle
ORCID:
AuthorORCID
Walter, Fabian0000-0003-4793-7880
Ampuero, Jean-Paul0000-0002-4827-7987
Additional Information:© 2016 American Geophysical Union. Received 2 JAN 2016; Accepted 10 JUL 2016; Accepted article online 13 JUL 2016; Published online 8 AUG 2016. This project was funded by Swiss Federal Institute of Technology Zürich (ETH) under grant ETH-27 10-3. The salary of F.W. was partially funded by the European Union Seventh Framework Programme (FP7-PEOPLE-2011-IEF) under grant agreement 29919 and by the Swiss National Science Foundation (GlaHMSeis Project PP00P2_157551). This work was partially supported by grants from the Swiss National Science Foundation (200021_127197 SNE-ETH (ROGUE)) and the Arctic Natural Sciences Program of the US National Science Foundation (OPP-0909454 and OPP-0908156). Waveform processing and plots were done with MathWorks MATLAB and Obspy (A Python Toolbox for seismology/seismological observatories). We thank Brad Lipovsky, Naofumi Aso, and one anonymous reviewer for their review that helped to improve the quality of the paper. We are grateful to many members of the Institute of Geophysics, the Swiss Seismological Service and the Laboratory of Hydraulics, Hydrology and Glaciology of ETH Zürich. S. Husen provided valuable support for preparation and conduction of the seismological monitoring. Importantly, M. Lüthi initiated the ROGUE project opening access to logistical and scientific support for the present study. We thank M. Funk, V. Tsai, F. Gimbert, P. Dalban Canassy, and L. Andrews for interesting discussions. We also thank T. Wyder, C. Senn, K. Plenkers, S. Hiemer, M. Meier, C. Birchler, A. Bauder, R. Hawley and B. Morriss, M. J. Hoffman, and G. Catannia for their help during the field campaign in Greenland and making it all possible. Seismic waveform data are available via arclink.ethz.ch using network code XH.
Group:Seismological Laboratory
Funders:
Funding AgencyGrant Number
Swiss Federal Institute of Technology Zürich (ETH)ETH-27 10-3
European Union29919
Swiss National Science Foundation (SNSF)PP00P2_157551
Swiss National Science Foundation (SNSF)200021_127197 SNE-ETH (ROGUE)
NSFOPP-0909454
NSFOPP-0908156
Subject Keywords:seismic tremor; moulin; Greenland Ice Sheet; englacial hydraulics
Record Number:CaltechAUTHORS:20161111-085832479
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20161111-085832479
Official Citation:Roeoesli, C., F. Walter, J.-P. Ampuero, and E. Kissling (2016), Seismic moulin tremor, J. Geophys. Res. Solid Earth, 121, 5838–5858, doi:10.1002/2015JB012786
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:71930
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:16 Nov 2016 00:39
Last Modified:20 Aug 2017 05:46

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