A semi-automated algorithm to quantify scarp morphology (SPARTA): application to normal faults in southern Malawi

Hodge, Michael; Biggs, Juliet; Fagereng, Åke; Elliott, Austin; Mdala, Hassan; Mphepo, Felix

doi:https://doi.org/10.5194/se-10-27-2019

Articles | Volume 10, issue 1

https://doi.org/10.5194/se-10-27-2019

© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/se-10-27-2019

© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 10, issue 1

Research article

|

11 Jan 2019

Research article |

| 11 Jan 2019

A semi-automated algorithm to quantify scarp morphology (SPARTA): application to normal faults in southern Malawi

Michael Hodge, Juliet Biggs, Åke Fagereng, Austin Elliott, Hassan Mdala, and Felix Mphepo

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Final revised paper (published on 11 Jan 2019)
Supplement to the final revised paper
Preprint (discussion started on 09 May 2018)
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: 'A Semi-Automated Algorithm to Quantify Scarp Morphology (SPARTA): Application to Normal Faults in Southern Malawi', Anonymous Referee #1, 25 May 2018
- AC1: 'Response to Reviewer 1', Michael Hodge, 18 Oct 2018
RC2: 'Review of A Semi-Automated Algorithm to Quantify Scarp Morphology (SPARTA): Application to Normal Faults in Southern Malawi” by Michael Hodge et al.', Laura Gregory, 27 Jun 2018
- AC2: 'Response to Laura Gregory's Review', Michael Hodge, 18 Oct 2018

Peer-review completion

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

AR by Michael Hodge on behalf of the Authors (18 Oct 2018) Manuscript

ED: Referee Nomination & Report Request started (22 Oct 2018) by Federico Rossetti

RR by Laura Gregory (12 Nov 2018)

Suggestions for revision or reasons for rejection

The manuscript has been carefully revised and all of my previous concerns and comments have been dealt with to a high standard. The method is clearly described and I hope will be used by the community. It has been applied in an important region accompanied by a nice discussion of fault rupture, segmentation, and growth. I have two very minor comments. I look forward to seeing this paper published.

Minor (technical) comments:
Figure 4 caption – should the caption indicate that the grey triangles show the location of the crest and base of the fault scarp based on the ‘input parameters’ or possibly ‘as dictated by the algorithm?’. In the description of the algorithm it seems like these locations are assigned to each profile and therefore do not need to be ‘manually’ picked.

On the age and most recent rupture of the faults sampled (p 34-35): If a fault has had a recent rupture that only produced a relatively small displacement (e.g. 1 m offset on a 10 m high composite scarp), is it possible that the recent rupture may not be recognisable in the algorithm, because the average slope of the scarp is calculated. If a fault had a recent rupture, I would expect the composite scarp to still be recognised in the algorithm, but with a slightly steeper average slope value representing a steeper scarp base and a gentle scarp above the recent rupture (both steeper than the upper and lower surfaces).

I do not see this as a problem, but it also may be important to take into consideration if one is trying to determine whether there has been a recent rupture – I wonder if changing the threshold angle could help recognise a steeper portion of a larger composite scarp if it is persistent along the scarp? (This is more just a comment than a request to change anything).

Best regards,
Dr Laura Gregory

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ED: Publish subject to technical corrections (04 Dec 2018) by Federico Rossetti

ED: Publish subject to technical corrections (04 Dec 2018) by Federico Rossetti (Executive editor)

AR by Michael Hodge on behalf of the Authors (05 Dec 2018) Manuscript

Short summary

This work attempts to create a semi-automated algorithm (called SPARTA) to calculate height, width and slope of surface breaks produced by earthquakes on faults. We developed the Python algorithm using synthetic catalogues, which can include noise features such as vegetation, hills and ditches, which mimic natural environments. We then apply the algorithm to four fault scarps in southern Malawi, at the southern end of the East African Rift system, to understand their earthquake potential.