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    Possible evidence for variation in magnitude for marsquakes from fallen boulder populations, Grjota Valles, Mars

    Brown, J. and Roberts, Gerald P. (2019) Possible evidence for variation in magnitude for marsquakes from fallen boulder populations, Grjota Valles, Mars. Journal of Geophysical Research: Planets 124 (3), pp. 801-822. ISSN 2169-9097.

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    Abstract

    Following observations of mobilized boulder trail populations from Cerberus Fossae, Mars, that have been interpreted as possible evidence of large magnitude marsquakes rupturing for distances of ~207 km along exposed active faults, additional boulder trail populations were measured along shorter faults within the region of Grjota Valles (50-150 km length) to test the hypotheses that (1) these faults are also candidate locations for marsquakes, and (2) that marsquake magnitude might be smaller, limited by fault dimensions available for rupture. For a region containing two en echelon graben, boulder trail data define two anomalies with maxima in (a) boulder trails per kilometer, and (b) maximum width of boulder trails, one that is ~116 km in length along strike and the other ~70 km in length along strike. Values for the maxima are 45 trails per km and 5 m mean trail width for the 70 km long anomaly, and 115 trails per km with 5.3 m mean trail width for the 116 km long anomaly, above background values measured elsewhere along these faults of zero trails per kilometer with zero boulder trail widths. If combined with published data from Cerberus Fossae with a ~207 km long anomaly in boulder trails per km (125 trails per km maxima) and maximum mean boulder trail width (8.5 m maximum trail width), the 3 datasets suggest correlations between the (a) along-strike length of boulder trail anomalies, (b) boulder trails per km and (c) maximum boulder trail width. If interpreted as due to single marsquakes, and if the dimensions of these anomalies are a proxy for rupture length, when combined, one interpretation of this is that boulders have been mobilized by marsquakes and that the marsquake magnitude is proportional to the along strike length of the anomalies. In other words, the data suggest that marsquake magnitude, if that is the cause of the anomalies, is limited by fault length as expected for terrestrial seismically active faults. Such findings suggest that the Martian surface may have been shaken, in the very recent past, by large magnitude marsquakes. We discuss this in terms of the seismicity of Mars.

    Metadata

    Item Type: Article
    Additional Information: This is the peer reviewed version of the article, which has been published in final form at the link above. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.
    Keyword(s) / Subject(s): Marsquakes
    School: Birkbeck Schools and Departments > School of Science > Earth and Planetary Sciences
    Research Centre: Earth and Planetary Sciences, Institute of
    Depositing User: Gerald Roberts
    Date Deposited: 08 Feb 2019 13:24
    Last Modified: 07 Dec 2019 14:15
    URI: http://eprints.bbk.ac.uk/id/eprint/26146

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