Microearthquake seismicity of the Mid-Atlantic Ridge at 5°S: A view of tectonic extension

Frederik Tilmann*, Ernst Flueh, Lars Planert, Timothy Reston, Wilhelm Weinrebe

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

26 Citations (Scopus)


We report measurements made with an ocean bottom array which was operated for 10 days on the Mid-Atlantic Ridge just south of the 5°S transform fault/fracture zone. A total of 148 locatable earthquakes with magnitudes ∼0.5-2.8 were recorded; seismic activity appears to be concentrated within the western half of the median valley. The median valley seismic zone is bounded in along-axis direction by the transform fault to the north and the tip of the axial volcanic ridge to the south. A few scattered events occurred within the inside corner high, on the transform fault, and in the western sidewall close to the segment center. Earthquakes reach a maximum depth of 8 km below the median valley floor and appear to be predominantly in the mantle, although a few crustal earthquakes also occurred. The presence of earthquakes in the mantle indicates that it is not strongly serpentinized. We infer the median valley seismic activity to primarily arise from normal faulting.

Original languageEnglish
JournalJournal of Geophysical Research
Issue number6
Publication statusPublished - 10 Jun 2004


  • Earthquake location
  • Mid-Atlantic Ridge
  • Tectonic extension

ASJC Scopus subject areas

  • Earth and Planetary Sciences (miscellaneous)
  • Atmospheric Science
  • Geochemistry and Petrology
  • Geophysics
  • Oceanography
  • Space and Planetary Science
  • Astronomy and Astrophysics


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