Testing seismic amplitude source location for fast debris-flow detection at Illgraben, Switzerland

Walter, Fabian; Burtin, Arnaud; McArdell, Brian W.; Hovius, Niels; Weder, Bianca; Turowski, Jens M.

doi:https://doi.org/10.5194/nhess-17-939-2017

Articles | Volume 17, issue 6

https://doi.org/10.5194/nhess-17-939-2017

© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

https://doi.org/10.5194/nhess-17-939-2017

© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Articles | Volume 17, issue 6

Research article

|

22 Jun 2017

Research article |

| 22 Jun 2017

Testing seismic amplitude source location for fast debris-flow detection at Illgraben, Switzerland

Fabian Walter, Arnaud Burtin, Brian W. McArdell, Niels Hovius, Bianca Weder, and Jens M. Turowski

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Final revised paper (published on 22 Jun 2017)
Supplement to the final revised paper
Preprint (discussion started on 13 Oct 2016)
Supplement to the preprint

Interactive discussion

Status: closed

AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

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- Supplement

RC1: 'Review', Anonymous Referee #1, 16 Nov 2016
- AC2: 'Response to Review', Fabian Walter, 20 Dec 2016
RC2: 'Review', Anonymous Referee #2, 22 Nov 2016
- AC3: 'Response to Review', Fabian Walter, 20 Dec 2016
AC1: '"To Editor"', Fabian Walter, 20 Dec 2016

Peer-review completion

AR: Author's response | RR: Referee report | ED: Editor decision

ED: Reconsider after major revisions (further review by Editor and Referees) (27 Dec 2016) by Paolo Tarolli

AR by Fabian Walter on behalf of the Authors (20 Feb 2017) Author's response Manuscript

ED: Referee Nomination & Report Request started (21 Feb 2017) by Paolo Tarolli

RR by Anonymous Referee #2 (08 Mar 2017)

RR by Andrew Lockhart (19 Mar 2017)

Suggestions for revision or reasons for rejection

Technical queries and observations:
Body wave vs surface wave: the findings in Burtin et al that body wave dispersion fit the data better (if I understand that finding correctly) seem curious, given that debris flows are inherently a surface phenomenon. I look forward to your future work exploring the body wave vs surface wave question.
P10, L 20 – Since Table 2 shows that your Guralp 6TD’s have a frequency response from 1-100 Hz, I’m puzzled by your selection of a butterworth filter edge at 0.5 Hz. In order to keep your analysis in the linear part of the seismometer response curve, shouldn’t you filter it above 1Hz? Maybe 2Hz?
P11, L11-22, and Figure 10 – This 10-minute detection time lag at CD24 with respect to the geophone detection is interesting and important. 10 minutes is a long time for this example. Is there a volumetric component to the discrepancy? Is the ASL method detecting something like a volumetric centroid of the flow? If so, and if the flow front is just an un-energetic watery flow it is still a useful detection for hazard mitigation.
Following this theme, if a public alarm is to be disseminated as soon as possible, one would surely use the detection at or around CD1, where the discrepancy between the two systems is not great.
Figure 10, Section 5.3 – It seems possible that the lack of success using ASL to detect short-lived rock falls using short time windows may not be a good reason to avoid them for debris flows. For example, Kumagai et al (2009) used a 5-second window. Why the difference? It appears that your results using a 30-second window were similar to the 100-second window. Did you try a shorter window? Can you discuss that a little more?

Minor editorial suggestions:
P1,L15 – change ‘torrents in short time.’ to ‘torrents in a short time.’
P7, L15 – change ‘only few stations of the seismic network’ to ‘only a few stations of the seismic network’
P8, L15-20, and Figure 6- it’s not clear but it looks like a typo may have been made (station IGB3?). IGB09 does not have a very high amplitude, despite P8, L16.

Referee Report: PDF

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ED: Publish subject to minor revisions (further review by Editor) (21 Mar 2017) by Paolo Tarolli

AR by Fabian Walter on behalf of the Authors (04 Apr 2017) Author's response Manuscript

ED: Publish as is (12 Apr 2017) by Paolo Tarolli

AR by Fabian Walter on behalf of the Authors (18 Apr 2017)

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Short summary

Debris flows are naturally occuring mass motion events, which mobilize loose material in steep Alpine torrents. The destructive potential of debris flows is well known and demands early warning. Here we apply the amplitude source location (ASL) method to seismic ground vibrations induced by a debris flow event in Switzerland. The method efficiently detects the initiation of the event and traces its front propagation down the torrent channel.